Many people ask me the same questions. I have listed the most popular here, please click on the question to see the answer (or simply scroll down to see them all). If you have a general query that you don't see answered here, please let me know and I'll probably answer it here for the benefit of others.
General Questions
Rocket Science
Simple Boats
Comfort Comparisons
Can I lengthen the boat?
How much does it cost?
Charter boats and the Norseman 43
Which is better, a "Galley up" or "Galley
down"?
Crossbeam Design
Safety Questions
Design Specific Questions
History of the Strider
How do you trail a Strider?
How roomy is a Strider hull?
Building Questions
How long does it take to build?
Can I build in steel?
What is KSS?
Foam sandwich and vacuum-bagging
How do you strip plank a hull?
Which plywood and timber should I use?
What does PAR timber mean?
Sailing and Performance Questions
How long does it take to assemble?
Performance Comparisons
Performance Predictions
Bridgedeck Slamming
Which steering system should I use?
Low Aspect Ratio (LAR) Keel Design
Aerorigs
How well do catamarans tack?
Can I build in steel?
No, is the short answer. It's just too heavy. A typical 10m catamaran might be built in 9mm ply. This weighs about 1lb/sqft. In comparison, 4mm steel plate - the thinnest you can use for boatbuilding, weighs about 7.5lbs/sqft! Clearly a boat built in steel will be far too heavy for any normal boat. However, some large catamarans (say over 45') have been successfully built in aluminium.
Having said that, most people want a wood interior while condensation is a problem on all metal boats. Thus significant extra non structural weight is added to the shell which compounds the problem. Also don't forget that the cost of the hull shell is only about 30% of the total cost, so any material savings will only have a small impact on the total budget.
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Are multihulls dangerous?
The following question was posted on the Multihulls Magazine bulletin board by George White on September 22, 1999 at 22:52:20: Can someone give me some ammunition to throw at a monohull owner who swears that catamarans are much more dangerous than monohulls. He owns a 42-footer. I want him and his wife to charter a 40-foot catamaran in the BVIs and they say no way, that catamarans are far too likely to turn over. I know this is ridiculous, but I need some help. Anyone?
I replied: "Ask your friend to prove his assertion. Point out that NO cruising catamaran has ever capsized when under bare poles. Implication: cats that capsize have too much sail up - "driver error". Tell him about Bob Beggs - 4 Atlantic crossings in 26' open cats, yet capsized a Beneteau 38 monohull in Biscay and lost a crew member. Primarily you friend wants a SAFE boat, ie one that is not risky to sail. I feel the risks at sea are (in order): Personal injury, collision, rig failure, fire, structural failure, capsize.
I once crossed the Atlantic in a monohull that we had to pump every 20 minutes - on the same trip we had a major (electrical) fire and broke the forestay. My cousin was badly injured when she was thrown across the cockpit in the Caribbean on her monohull. Multihulls offer "no bruisin cruisin". It's very easy to fall overboard on a monohull (eg Eric Tabarly); very hard on a multihull. If he won't charter get him to go to the Multihull demo days so that he can try out some cats for himself. Ultimately one cannot answer someone with uninformed prejudice if they don't want to listen."
Someone else said that most charter boats in the Caribbean are now catamarans. Charter companies would not risk letting people sail dangerous boats. Which is a good point.
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What is KSS?
The KSS method could be one of two things. Either it's just the now standard way of building flat panel foam sandwich boats (I used flat panel foam sandwich to build my Gypsy). Or its Derek Kelsall's own system of making a big panel that includes both sides and bottom in one piece which is then cut, tapered and pulled up round the frames. The problem with the latter system is that you make a VERY big panel. That leads to several problems. Unless you are several experienced laminators working together I would not recommend making a panel bigger than 15' x 5' in one go. Its just too much hard work. You would also need a very big flat table (and large shed to fit it in). My Gypsy panels were built in a garage 15' x 14' so I made them in two pieces. That way they fitted in, but it also meant that I could make a panel in an evening (3 hours). I also built the complete cuddy, cockpit, beams, bulkheads etc there so I could work at home and make a complete kit of parts before moving to the boatyard - a great saving in time and money.
Folding up the hull seems to be a rather hit and miss system, again because of the size of the panel. Unless you have several people to help it will be impossible, even then it will be difficult as it will be very floppy and hard to keep square. Cutting and joining will mean a lot of bumps that need filling later. I don't honestly think it is a time saving system in the long run. Remember that building the hull is the quick part. Don't be tempted by claims of speedy building - no method is. But it IS easy to design a boat that is hard to build! The best way to have a boat on the water quickly and in budget is to build the one that you need rather than the one that you want. Also go easy on the services (plumbing, electrics etc.) as they take forever to fit. Building a flat panel boat (steel monohull or deep V cat, or a dory - it doesn't matter) compromises the shape you would ideally like from performance, seakindliness etc. Making a KSS shape must compromise it even more. For example, you really need Veed sections forward if you have an offshore boat. The KSS system is usually used on wide flat bottomed hulls. Although my Gypsy is flat bottomed it is Veed forward to reduce slamming.
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What is the history of the Strider?
Striders have proven one of our most popular designs, for good reason as they are good all rounders. Enough accommodation for coastal cruising, race winning performance - especially in light winds - and readily trailable. The original version was for home building in ply and featured daggerboards and a semi trampoline/hard deck area.
This version was first built in grp in 1984. It proved to be a popular race boat, holding the course record for one leg of the offshore fully crewed Three Peaks Race, coming third in the 1985 World Micromultihull Championship and 1st and 3rd in the 1989 and 1992 UK Championships respectively. Several different rigs were drawn to suit individual owners specific needs, the big rigged boats have a wider overall beam and usually an all trampoline deck area. Such big rig boats are sailed on Lake Kariba in Zimbabwe for example.
In 1987 Palamos Boatbuild wanted a budget boat that would be a good introduction to cruising catamaran sailing. We had found that many people did not want performance, just a big open deck, simple to sail dayboat with the option of occasional overnighting. Most of these owners only wanted to take a boat home at the end of the year and so designing the boat for regular trailing was not important. As a result the Strider Club was developed which proved very popular during 1988 and 89 with about 40 grp boats sold.
This version of Strider had low aspect ratio keels, a small rig and a solid cockpit tray. All making the boat easy and comfortable to day sail. It was this version that three of us sailed singlehanded in convoy to the Soviet Union in 1989. In the same year Palamos Boatbuild went into liquidation and only a few new boats were built in the 90's before the moulds were broken up. However, the plans are still available for both versions if you wish to build in plywood or strip plank cedar. The home builders version of the Strider Club is called Shadow.
To learn more about the different versions buy the video "A Day Sail to Russia" which features the Strider Club, or "Multihull Sailors Have More Fun!" which features sailing shots of both versions.
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How do you trail a Strider?
Like all our small cats (except Wizard and Sango) the Strider is demountable. For quickest assembly a telescopic trailer is used. I do not like telescopic beams as that means that the overall beam is restricted and when opened out there is not much crossbeam left in the hull, compromising strength. There are stainless steel straps over the beams, one at each outer and one at each inner gunwale. These have proved 100% reliable over the last 18 years.
If you don't have a telescopic trailer then it is quite feasible to assemble the boat on the foreshore as each hull can be manhandled individually. A telescopic boat can only be moved as one unit which of course is going to be much harder as its more than twice the weight. 2 people (who had done it before) assembled a Strider from trailer to launching in 40 minutes watched by a magazine reporter.
Most of the time taken is not assembling the hulls but raising the mast, attaching nets, sheets, rudders etc. Bigger rigged boats take longer to raise the mast - one reason why I prefer smaller boats for trailering. A standard Strider mast can be raised without using the boom as a lifting pole which saves a lot of time.
The Wizard and Sango are trailed differently. The hulls fold under the central cuddy for trailering. To assemble, the trailer is simply backed into the water and as the hull sterns begin to immerse so they open out. The more the trailer goes into the water the more the boat opens until it is completely assembled. Let the water do the work, no lifting or jacking! Even my mother could assemble a Wizard (assuming she could back a trailer in a straight line!). Retrieval is the opposite, again no lifting is required.
The Wizard and Sango mast is stepped into a deep mastfoot so will stay up without shrouds attached, simplifying things enormously. It is also possible to lower the boat from the trailer onto the ground. Incidentally, most trailerable boats (eg Farriers) must either stay on the trailer or in the water and it is very difficult to get them off a trailer when on-shore. That can often make life difficult when making repairs or even when antifouling the hull.
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What is your opinion of charter boats and the Norseman 43 in particular?
In general terms: I would not buy a charter boat to live on. Charterers are only on the boat for 1-2 weeks and they tend to eat ashore and not sail at night. Usually there are 6-8 people to help with anchoring, sail handling etc. So there will be little stowage, no bookshelves, small galley, no chart storage area etcetc.
I would definitely NOT go for a scheme where you buy a big charter cat for 50% down and leave it with a charter company for 5 years. If you want a new Mercedes would you go for a scheme where you paid 50%, and then lent the car to a taxi firm for 5 years before being able to use it?
Charter boats are business assets, so owners want the maximum return for minimum investment. In other words, charter boats (like hotels) go for maximum bunks and lounging space (by the pool in a hotel, on deck on a boat) at minimum cost. Would you choose to live in a hotel?
I have owned cruising catamarans from 35' to 28' and lived on board and sailed multihulls up to 55'. I have also worked on charterboats up to 70ft in the Caribbean. I have found that a 35' cat is plenty big enough for a couple to live on. Bigger boats need more cleaning and maintenance, the sails and anchor are heavier etc.
If you only plan to day sail and holiday on the boat I'd recommend 32'-35'. If you want to live aboard then 38' is about the maximum for a small crew. The problem with smaller cats is the load carrying. I have lived on a Windsong and a Gypsy, but it's a bit like camping. A 32' boat is like having a caravan or RV. It's not until you get to 34-35' that you have the carrying capacity to live like you do in a hotel or house. Over 40' you have to take your servants with you (ie crew).
Specifically regarding the Norseman 43. I sailed it 4100 miles between Capetown and Rio and lived on it for 4 weeks with 5 other men. So I have probably sailed one more than the designer or builder. It was unstable. The bows are very fine, vertical and have no flare. So there is no reserve buoyancy.
I have pushed catamarans hard in races over the years, but until sailing the Norseman never had any worries about nose-diving. In a squall we had the rudders out of the water and the bows under until the maststep was in the water. After that we sailed very cautiously. We found it made a lot of leeway, tacked very slowly and only sailed 120 degrees between tacks even in ideal conditions.
The saloon seating was VERY uncomfortable. When I sat in the cockpit my feet would not touch the sole, so that was uncomfortable as well. The chart table was very small and the bookshelves tiny. There was little space for personal effects apart from one bag of clothes each (ie fine if you're a charterer). The bunks were very awkward to get into. Bridgedeck slam was very pronounced, even downwind. But there was 7' headroom in the saloon so why the low bridgedeck?
The deck layout did not work well. It took 5 fit men 10 minutes to hoist the mainsail, the mainsheet traveller didn't work properly, the stoppers were badly placed, the helmsman seat was poorly positioned etc. But in general the boat was well built except for the fact that the interior was gelcoated throughout and there were no headlinings. This means it would not be usable in the UK or most of Europe because of condensation. Also all the deck fittings are tapped into aluminium plates. So there is a potential corrosion risk. Also its impossible to add or change any deck fittings. Electric cables are run in the laminate so cannot be changed and again no extra lights or electrics can be fitted (again not a problem on a charter boat)
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How do you strip plank a hull?
When we first started drawing strip plank boats, back in the early 1980's, we drew and built them using a "male" mould. Ie we set up frames that looked like upside down bulkheads, and then strip planked over them. So the frames are set up in exactly the same way as one would do when building a conventional stringer frame or foam sandwich boat.
This way has the advantage that it looks like a boat so is easy to fair and it takes up the minimum of space. The disadvantage is that after releasing and turning over the hull is relatively floppy until the inner glass skin has been laid up. Also it is not possible to add furniture or bulkheads before glassing the inner skin.
These disadvantages have led many people to use the "female" mould system. This means the boat is built "insideout". Instead of having "bulkhead shaped" frames the frames look like the bit of plywood you'd normally discard. The advantages are that you're working on the inner side of the hull skin, so you glass the inner skin first. It also means you can add bulkheads etc before releasing from the frames. The disadvantages are that more space is needed. What you're building doesn't look like a boat while it is in the frames, so it is potentially harder to fair. There has to be a join down the centreline which is hard to make especially at the bows - possibly the most important part of the boat to make strong.
As far as I am concerned, the jury is still out, so at present I will continue to draw boats built with the male mould system until I'm convinced otherwise. However, whichever way the boat is built, the final result will be the same. There is no difference in strength or weight between the two systems, it's only the way the boat is built that is an issue.
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How much does it cost to build a boat?
It is a natural question for people to ask as cost is usually the main factor in deciding what boat to build. Unfortunately it's not an easy question to answer - different people want different levels of fit-out while obviously different countries have wildly different material, labour and overhead costs. So the best I can do is make comparisons between different boats and to give an idea of costs when building in the UK.
But before I do that it's worth pointing out that building a 10m, 3T boat with 50 sq m of sail (or 33' x 6000lbs x 500 sq ft) will probably cost the same whatever designer is chosen. That's because sail and rig costs are independent of design, as are glass, resin and plywood as they are sold by weight or area. So too are cookers, anchors, lights etc etc.
You can make a similar sort of comparison with cars. The steel in a Skoda costs the same as in a Mercedes, but the latter is ten times the price of the former! And the difference in price goes into the builders pocket and into the general public perception of "I want one of those!" So, don't be misled by those who say "my boats are cheap to build". Having said that, it is certainly possible to find designs that are expensive to build. Ones that need special one-off fittings, or use exotic materials for example.
What is really important to homebuilders though, is the resale value. I know that's not at the forefront of your mind when choosing a new design, but you will want to have your work valued by others. I read recently that someone was complaining about the high price of second hand Woods Designs compared to other designers. Now that may be bad news for those trying to buy a cheap boat, but it has to be good news for the original builder.
It's been well publicised that my Gypsy cost me £5000 to build in 1995-7. But in fact that figure was for a sailing shell and was so low because I was very lucky to get a complete second hand rig for £200, about a tenth of the new price. Even so, I actually spent nearer £10,000 when things like engine, electronics, ground tackle, fridge, boom tent etc etc were included. Most UK builders reckon on spending around £12,000 for a complete Gypsy. I later sold my Gypsy for the asking price of £25,000. So that meant that I earned around £10 an hour while building it. And that's the sort of figure I would hope everyone would expect as a minimum when costing out their labour. A 10 year old wood Sagitta was recently sold for £45,000, again making it's builder about £10 an hour
So my guide for prices are as follows (in 2000): Strider etc £4-6000 (resale £8000-10,000) Wizard/Sango £6-8000 (we sold our Wizard in 1995 for £19,000) Surfsong/Windsong £8-10,000 Gypsy £12,000 (sold for £25,000) Sagitta, Mira £20000 (sold for £45,000) Flica, Meander £25,000 Nimbus £35,000
In other words, don't build one of these boats until you know you've got that much money available. But having said that, it's rare for me to actually have enough money to be able to finish a boat when I start building it. Boats always take time to build and money does slowly come in.
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How long does it take to assemble one of your trailable designs?
The first thing to appreciate is that there are two types of boat that can be taken by road, ie "transportable" and "trailable". Transportable means anything that can be legally taken by road. So a Mira and even a Meander are transportable, even though each hull has to be taken to the water individually. All the production Flicas and Banshees had to be taken 7 miles along narrow Cornish country lanes to been launched so even large boats are "transportable"
"Trailable" means that the whole boat can be taken in one trip without a police escort and that it can be assembled and rigged without outside assistance. At the recent (2000) Annapolis Boat Show I saw a large trimaran that is advertised as being "trailable" having its mast stepped by crane. I also saw that several builders claim "trailer to sailing in 30 minutes or less, even singlehanded". Now that really is misleading and totally impossible.
When I think of "trailer to sailing" I include: arriving at the slip, untying the boat, assembling it, tightening trampolines, raising the mast, bending on barberhaulers, spisheets etc as well as sails, launching the boat, tying it up, taking the trailer away, parking the car, walking back to the boat, untying it, motoring off and hoisting sail. That's "trailer to sailing". 30 minutes, I don't think so!! It takes me 15 minutes to rig my dinghy from the trailer, and I still have to get changed and launched so I always allow half an hour.
So, after that preamble, how long does it take to assemble a Strider? Many years ago a grp Strider was tested by a magazine. We had the boat in the yard, on the trailer behind a car, but untied. 40 minutes later it was at the top of the slip, ready for launching. 10 minutes later we had the sails hoisted and were sailing. That's with two people who had done it before. Later the same reporter watched us assemble and rig a Wizard in 20 minutes.
What takes the time is not the initial assembly, but raising the mast. The standard Strider and Wizard score well here as their masts are small and light enough for one person to be able to "walk" them up which save a lot of time compared to larger masts that need a pole/lever arrangement and a line taken to a winch. I recently saw a video of a Savannah 26 being launched. It literally took seconds to fold out and assemble itself. But I would still think an hour would be a sensible time to allow for "trailer to sailing".
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Can I lengthen the boat?
The quick answer is NO! The answer is also NO if you want to change the rig, or add a central rudder or lots of other modifications that you would like to see. Like all designers I spend a long time deciding on the initial concept of the boat and then even longer on working out all the details.
I know it's easy to add an extension to a house when you need more room for a growing family. But houses don't have to sail to windward, and it doesn't matter where the centre of gravity is - a house will always "float" level.
If you have a small car but would like it a "bit bigger" you don't go to your local garage and ask them to "add a bit in the middle". If you want more performance you don't just fit a bigger engine. You know that you would have to change the steering, brakes, chassis etc as well. So you either accept what you have or trade it in for a larger or faster one. So why, when it comes to boats do people think that they can have what they want, rather than what the designer drew?
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Which steering system should I use?
Getting the steering system right is vitally important because after all it is the main point of contact between you and your boat.
Except on the simplest and smallest boats I prefer to use semi balanced rudders with no skegs. These offer light steering - you should be able to balance the tiller extension on the end of your finger, even at speed, yet will still steer straight "hands off". A Youtube excerpt from the MSHMF video is shown below
I've sailed enough of my boats to know that it is quite possible for any of them to sail themselves in a straight line, yet still tack quickly in any sea. To say that only boats with a skeg hung rudder will steer straight is simply not true. The photo below shows my Merlin sailing at 7 knots with no hand on the tiller. The straight wake is obvious.
Boats with LAR keels have a conventional rudder setup with bearings at each end of a rudder stock tube. On boats with daggerboards the rudders have to lift when drying out. I use kick up rudders which lift clear of the water and are fixed to the boat with one bolt at deck level, and held down at the lower bearing by a rope led to a cleat. See photos below.
It's a very simple system, and has worked extremely well over the last 20 odd years. When raised the rudder does not stick out behind the boat, where it could be prone to damage from other boats when moored. It does not kick up automatically because such a method would have to ensure that the rudders didn't lift when sailing through a clump of weed at speed, but did kick up at low speeds if running aground in mud when probably the shock loads are a lot less. It doesn't seem likely that an automatic system can be devised that can differentiate between the two.
Clearly a wheel offers far more power than a tiller and thus it is essential for boats over 12m (40'). Conversely, the steering loads on boats under 30' are low and tillers work well. It's on boats between 30' and 40' where it's more a question of personal choice. Of course, there are pros and cons to both wheel and tillers. A wheel is good when motoring as the engine controls are always within easy reach, the steering position is near to the centre of the boat, so it is well protected and the helm can reach most sail controls. On the other hand, tillers are good when sailing as they allow the helmsman to move around the boat, see both sides of the sails, keep clear of the crew winching etc. Furthermore, tillers are more responsive when sailing in a quartering sea, while when coming alongside they allow the helm to stand near the gunwale for the best view.
I always use a tiller bar despite its disadvantages, as it ensures that the rudders always stay in line. With a tiller steered boat I now prefer two telescopic tiller extensions, one for each tack, rather than a very long central extension. I use standard dinghy extensions that extend out about 5' and initially clamp them to the tiller bar to check for their correct position. Later I through bolt them, I haven't found pop rivets to be very successful as they tend to wear out quickly. I always draw an Akkermann linkage on the tillers (that's the same as used on the front wheels of a car). As the boat turns the inner rudder makes a smaller radius circle than the outer, so it has to be held over at greater angle.
For wheel steered boats I suggest using a quadrant to one rudder stock. You can buy one, or take a lead direct from lugs on the tiller. It's then simple to use a pair of wires (or spectra rope) from the tiller leading to a chain and sprocket fitted to the wheel. An alternative is to use a push-pull cable (eg Morse, Teleflex) although this usually only works well on smaller boats (say under 10m). I don't recommend a hydraulic system. It's heavy, complicated and seems more prone to problems than any other system I've seen. But worst of all, it gives no feel to the helm. The result is a bit like driving a car with PAS or a motorboat, not a sailboat.
It is hard to arrange a automatic disconnect wheel system for use with kick up rudders that doesn't result in some play, so if you choose a boat with daggerboards (and thus kick up rudders) the wheel is probably not for you. Having said that, some people have made a good compromise (eg a local Sagitta) and use a wheel purely when motoring and revert to tillers when sailing.
If you do use wheel steering then you must also consider emergency steering. I usually prefer to have an emergency tiller that can be fitted to the rudder without the quadrant as that means it is possible to disconnect a potentially completely jammed rudder and steer with just one.
These days autopilots are simple to set up and use (especially those with a remote control), reliable, draw very little power and so when passage making are almost certain to be used. This means that the crew comfort and protection considerations are no longer as important as they once were.
One final comment, if you want a boat that is easy to build and maintain, go for tillers.
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How long does it take to build?
I've written about this elsewhere, but feel I must keep going on about how complex boats can be to build. I know that building the hulls is usually the first step and its natural to want to make that as simple as possible, but in fact building the hulls is always the easy bit.
My last two boats have been the Gypsy and Eclipse. I was day sailing my Gypsy after about 1000 hours work, although only 4' longer I've done more than 1000 hours work on the Eclipse since first sailing it and its still not finished.
One small example, which may sound a minor, silly point, but all these little extras soon mount up. My Eclipse has 23 interior lights, Gypsy had 6. Lights need wiring, conduits, circuit breakers, switches etc and all to be planned before building has progressed too far so that it can all be neatly hidden.
At least 30% of a monohull's displacement is a "go out and buy, then stick on the bottom" lump of steel or lead. On a multihull ALL its displacement will go through your hands. That means on a 40' cat you'll end up handling 5-6 tons of material. An Eclipse 3 tons, a Gypsy 2 tons.
Don't think that a slightly longer boat is not much more to build. Surface area (laminating, painting, sanding etc) goes up by the square of length. Weight (material that you have to handle, carry up ladders etc, eg timber, plywood, glass, resin) goes up by the cube.
If you really want an "easy build" boat the answer has to be - leave it out. Use an outboard engine not inboards, a tiller not a wheel. Don't fit a freezer or a shower. Keep the electronics to a minimum. Accept open fronted lockers, not drawers etc
By and large, boat building is not profitable, so when a boat is sold for £100,000 that means most of that money goes on materials and labour. Typically I'd suspect that 25% would be on materials. You don't get anything for nothing in life, so you will have to earn that remaining £75,000 by putting in the hours. Typically you work 2000 hours a year at your job. Think back over the last 3 years and work out how much you're done at work. Then think about spending 5-6000 hours building a 45' cat. Also think what else you could be doing in that 5000 hours, (have a social life? watch your kids grow up?).
On a 40' cat 5000 hours probably equates to 35,000 miles sailing. In other words, you will have to sail nearly twice round the world before you spend more time sailing a 40 footer than building it. I have built 18 boats in the last 20 years (all but two for my own use). I know first hand how hard it is to keep going on a project. The Eclipse has taken up most of my life for the last two years, I know I couldn't cope mentally with building anything larger.
Much worse than having a boat that's too small for you is spending years half building a boat and then giving up. So, please think very carefully about the length of time you are really prepared to commit to your boatbuilding project. I will say it again and again, there is no need to have a catamaran much over 35 feet for normal family sailing, while even a charter boat need not be more than 40 feet. Don't be seduced by the glamour of big boats unless you can afford to buy one complete.
What do you think of the Aerorig?
Several people have asked me about fitting the Aerorig to their catamaran. The Aerorig is a trademark name for a unstayed mast where the jib and mainsail are attached to the same very long boom. . The Aerorig is not patented as its been used for years by model boat enthusiasts. It was also used on the 70' Elf Aquitaine in the 1984 OSTAR It has also been used on several of my designs, most notably the Savannah 26. In October 2000 I sailed this boat 1500 miles singlehanded up and down the eastern seaboard of the USA from Savannah to Annapolis. So I now have a pretty good understanding of how it works. As with all things there are advantages and disadvantages.
To my mind the advantages are: Easy sailing: The sails are always working correctly, whatever point of sail. Maybe it would be better to say the rig works to 95% efficiency all the time. A conventional rig may work to 100% if you're an expert, but only 70% if you're not. A conventional rig needs extra downwind sails, ie spinnakers. The Aerorig doesn't. There are only light loads on the mainsheet (but not as light as claimed), and once unrolled there is never a need to adjust the jib sheet
The disadvantages are: The rig is very heavy, leading to more pitching and less load carrying You probably need to modify the cabin. The minimum "immersion" of mast into cabin is about 1 in 7 ie a 35' high mast needs 5' of bury. Also the cabin has to be wide enough to spread the load. Its usually OK with a conventional bridgedeck cabin (although you may need to add a nacelle). Impossible to fit on an open boat and a bit awkward on a boat with a cuddy like the Savannah. A possible lack of sail area especially in light winds. That's because the jib is very small (only 20% of the total area) to maintain the correct balance. You can't motorsail safely to windward with both sails unfurled. It is possible to sail an Aerorigged boat backwards. A nice party trick but about as useful as reverse on a motorbike. But I discovered the hard way that the boat could sail backwards in a strong wind when I thought I was motoring forward. After a narrow shave when going under a bridge I always rolled up the jib before motoring. When reefing the jib must be furled first or the rig unbalances
It's a very expensive rig. With the case of the Carbospars/Forespar rigs a lack of attention to detail and unfortunately a lack of customer aftersales service. I could recommend the concept to those cruisers who wouldn't dream of using a spinnaker, but unfortunately I can't recommend products made by either Forespar or Carbospars.
How accurate are computer speed predictions?
I was fortunate that when I was a design student I was able to use the college test tank to run some model tests on a 5' (1.5m) model catamaran. I wanted to see how much extra drag was generated by having two hulls relatively close together rather than at infinite spacing. I quickly discovered that test-tanking models is not a very exact science (even using 5 ft models in the biggest educational test tank facility in the UK) A bit better than a guess, but not a lot.
Purely theoretical /computed tests are even more of a guess. There are far too many assumptions that have to be made. The monohull race boat rule, the IMS is a good example of such a "theoretical" rule.
I'm sure I'm not the only one who has a background of dinghy sailing. Thousands of dinghies race thousands of handicap races every year. So we "know" a Laser 1 rates 1077 and a Laser 2 1035. That's what, 4% faster? Even my mother could look at the two boats sailing and say the Laser 11 is the faster boat. After all it is longer, and has a trapeze and spinnaker.
I believe the IMS is supposed to be accurate to +/-2% and people are happy with the results because the formulae look complex and results can only be calculated by computer so must be right! Yet if a Laser 1 speed was calculable under IMS it could be 1050, say, ie within 2% of the real value. Similarly a Laser 2 could work out at 1050, also within 2%. So the super accurate, everyone is happy with the results, IMS would make the Laser 1 and Laser 2 the same speed!! As I said a second ago, my mother is a better handicapper than that.
Compare the complex measurements needed, the small speed range that monohulls use and the type forming of the IMS rule and I think you can see that no completely theoretical calculation can be much better than a guess dressed up by computers to convince the uninitiated.
Having said all that, about 15 years ago I developed a spread-sheet to try and predict the performance of my new designs. It seems to give reasonable results. As an example, the 35' Banshee has been tested full size under power with engines ranging from 4hp all the way up to twin 90hps. The predicted speeds were always close to the real thing. One reason for the accurate results is that my hull shapes are all fairly similar so I was able to "type form" the results. I also used the data I obtained from those early tank test results and also from work done by the US Navy in the Taylor tank. Unlike many I also make an allowance for windage (those who have tried to motor a large multihull under outboard in a strong wind will know how great windage drag can be!)
At its simplest, it seems that the best indicator of speed is the Texel Rating, developed by Nico Boon of Holland (Lilian's father). More details can be found on the website www.texelrating.knwv.nl for beach catamarans and on the website www.ctcnederland.nl for all cruising multihulls.
Incidentally, I think the nut on the end of the tiller has a bit to do with it as well. I raced my Stealth dinghy on New Years Day. A number of Laser 1's also raced, including one from the UK Olympic squad. He was 30% faster than the second Laser and that's in identical boats!! I regret to say he also beat me and I was supposed to be faster.
Over the years I've built several foam sandwich boats, but always as an amateur rather than professional builder. That means I haven't had access to lifting gear, a large work force, sophisticated heated workshops etc and I only use tools that anyone might have at home.
Airex foam is still the only sensible choice for double curved areas, eg the hull bottoms as it can bend at room temperature. But it softens in even moderate heat (eg from the sun). So a rigid pvc foam is necessary for the decks and topsides. I have found Divinycell to be the best foam, partly because it has smaller "pores".
Divinycell make a lightweight bonding paste for their foam, but other companies make similar products which I usually use. The main problem with foam sandwich construction is that although you can stick glass to foam its hard to stick foam to glass. Because of the huge area you need lots of pressure.
People tried sandbags etc to weigh the foam down, but it doesn't work as you can't get an even pressure. Its also lots of heavy sand to move! That's why about 25 years ago people started using vacuum bags. But they found there were problems in getting all the air out over the whole panel. It was possible to suck the air out near the outlet and then the polythene sheet would stick down hard and so prevent any more air being sucked out. So builders then started laying plastic mesh fencing between the laminate and polythene. That made channels for the air to run through. But it was messy as the resin stuck to the fencing. So people then developed bleed cloth which seemed to do it all. But of course its expensive as its a one time use only material. Also it's time consuming to stick down.
Using a vacuum does suck up some of the resin and remove most of the little air bubbles. That makes a stronger, lighter laminate but to be honest I don't think the savings really amount to very much and are only important on a racing boat. And the bond is still only on the surface of each foam skin.
Instead of using a vacuum bag, I prefer using "contour foam" or scored foam, which is like end grain balsa in the sense that it is cut into small squares (about 11/2") and stuck to a thin glass backing. The squares mean that not only will the foam fold round a curved hull but also it can be laid down one row of squares at a time. Thus each square is in effect put down individually. Furthermore the bonding paste oozes out through the squares so you can see that its properly bonded, and also the squares increase the bonding area. I admit the weight is a bit higher, because of the extra bonding area, but its quick, reliable and needs no disposable materials. You can also do it alone. All the Sagittas, Elves, Flicas and Banshees were built that way. Its also how I built my Gypsy and Eclipse. I haven't had any reported problems with core failure over the last 17 years.
I hope the above helps explain the alternative "low tech" foam technique I prefer.
The glass I like to use is +/45 deg "Biaxial" glass bonded to a chopped strand mat backing for stability and interlayer adhesion. That is, instead of the glass strands running along and across the roll ie 0 deg and 90 deg (0/90) they run at 45 deg to the length. Its harder to make and thus more expensive, but has three advantages. One is that it isn't woven, but two layers laid one on top of the other. That makes its stronger as the woven glass tends to try and straighten the rovings which is weaker. Two, the bond to the substrate is better and it looks neater as the glass is flat. Finally, the impact strength is increased. That's because the energy from an impact runs the length of the glass strands and then "explodes", as it were, at the ends. So the longer the strands the better. That's one reason chopped strand glass isn't very strong. Obviously the longer the glass lengths the better. Glass at 45 deg is 40% longer than at 0 or 90 deg
Which plywood and timber should I use?
The quality of plywood is dependent on two factors. First the type of bonding glue and second the wood used. Both "weather and boil proof" (WBP) plywood and "marine" plywood use the same rescorcinol-type waterproof glue. Other types of ply, with one exception, don't use a "waterproof" glue so must not be used for boatbuilding.
The exception is possibly the "best" plywood you can get, the Dutch made Brynzeel. Even though it doesn't use the "correct" glue and therefore isn't classified as marine ply it actually has a guaranteed life when used for boatbuilding far longer than most other plywoods.
In some areas, notably N America, it is possible to get marine grade softwood ply (usually douglas fir). Otherwise the choices are usually "Far Eastern" (meranti) or Gaboon (also known as okume). Of the two I recommend gaboon as it is significantly lighter than meranti. It may not be as strong, but it is maximum stiffness and minimum weight that are the main requirements for plywood, generally all boats are strong enough.
As a general rule, if you are not sure how to judge the quality of wood, choose marine ply, but if you are able to inspect the wood, or can get it from a reliable source then WBP is usually OK for decks and interiors. But I'd still use the real thing for hulls that are kept afloat (even if glass/epoxy sheathed) and beams. That is because one of the differences between marine and WBP ply is that although the outer veneers will be essentially the same for both standards, the WBP inner veneers can be in several pieces, have gaps and be of less good quality.
The choice of timbers appears at first to be more confusing, but can really be broken down into three main types.
First there is timber used for strip planking. By far the best wood is western red cedar. It is lightweight, easy to work and durable. However it has a short grain and is soft so should not be used for structural timbers. Sometimes this wood is unavailable and so you should consult with your timber supplier for the nearest alternative. But be aware that you boat is likely to be heavier if you use a different wood.
Second there is the timber used for general framing, stringers etc. The species of timber you can use for these applications appears to vary enormously, but in fact they generally all have similar properties and so are equally suitable. You are looking for a lightweight timber with a long grain that is easy to work, as knot free as practical, and that glues easily. Usually the softwood pines and firs are the logical choice. Douglas fir, yellow cedar, sitka spruce, are typical examples. Again, your timber supplier can advise you further.
You want to use "joinery quality" or better as that standard has the least knots. Unless you are sure of your supplier it is best to inspect the wood yourself, and certainly be allowed to reject any you feel is unsuitable. Generally though you can cut out and discard sections of poor timber. The only exceptions to this are gunwales and, in particular, beams, which must be best quality throughout.
Finally there is timber for cosmetic uses, including outer gunwales, galley trims etc. For these you want a hard wearing and "pretty" wood. So teak, iroko or other hardwood is the logical choice, unless you want painted trim of course.
PAR means "Planed All Round" ie the wood is planed rather than rough sawn. So it's ready for use. However the planing removes some timber. So, in more detail, if the nominal size is 2" x 1" (say), which in millimetres would be 50mm x 25mm, then that means the thickness BEFORE planing. The planer takes about 3mm or 1/8" off each side. Thus a "planed all round" (PAR) 2" x 1" is 6mm or 1/4" less in total. Thus it is 1 3/4" x 3/4" or 45mm x 20mm (approx, because planers vary a little) So to sum up, 2" x 1" is approx 45mm x 20mm, 3" x 1" is approx 70mm x 20mm, 4" x 1" approx 95mm x 20mm etc
I am proud to design "simple"
boats. I don't consider them "crude" just because they are easy
to build, generally from single curvature panels. Solving a problem is
easy. Finding a simple solution to a problem is much, much harder. Just
because a boat is difficult to build that doesn't make it a "better"
design. Look at other disciplines.
In house architecture people prefer simple flat shapes. You rarely see
houses with curved roofs, and never see them with double curved walls.
The Gothic style went out hundreds of years ago.
In fashion, simple clothes are called "elegant", people don't
rubbish them as a result.
Ikea have made a fortune designing simple flat pack furniture that anyone
can put together.
Cars no longer have
fins, chrome strips and other unnecessary features.
In fact it seems that only in yacht design is "complex" design considered "good" design. I look at Wooden Boat magazine and I know that I could never ever build the boats featured there. I don't have the skill, the patience or the time. I prefer to sail not build. A local builder spent 500 hours simply fairing the main hull of his 26ft trimaran. I built almost a complete Strider in that time. Some so called home builder designs are now so complex the designers insist that the beams, for example, are bought, clearly they are considered too hard for amateurs to build.
Having said that I know I decided that I would not sell hull plans of the Transit. Builders have to buy those. But that is not because they are hard to build, rather because big boats take so long to build and I feel life is too short for boatbuilding. That's also why I no longer design boats over 40ft, but that's another subject.
People are right to be concerned about bridgedeck slamming on catamarans. Having said that, it is usually a comfort problem rather than a structural one. Fortunately it is, or should be, a thing of the past.
Early catamarans had low freeboard, partly because of the heavy materials which were all that were available at the time, and also because low freeboard boats always look better. The latter is still true today of course, but people have now got used to seeing high boxy catamarans.
In an attempt to cushion the slamming, many builders, and Prout Catamarans in particular, developed the central nacelle. Prouts took this nacelle to it's extreme and their last designs were more like three hulled catamarans with the nacelle in the water at rest.
I have never believed this approach to be a good one. I always say that for offshore sailing one should be able take a conventional inflatable dinghy under the bridgedeck. I sailed the S Atlantic from Capetown to Rio in a Norseman 43. Its bridgedeck was very low (but it looked a very nice boat due to its low freeboard) and it was very uncomfortable living on board. A few years earlier I had sailed from the UK to the Canaries in another low bridgedeck catamaran (again not one of my designs). The slamming was so bad that we were unable to use the saloon table as plates would jump off as we hit every wave.
Much of this slamming is self inflicted. Imagine two hulls close together pitching into a wave. The water they displace has to go somewhere, and it piles up just as the bridgedeck sails over it. Clearly a wider hull spacing will turn a narrow high peaked mountain of displaced water into a low flat molehill. A wide knuckle and flared hull will also help reduce the size of the induced wave.
The best solution is to start the bridgedeck well back and have it low only where needed. That's why most offshore catamarans have nets or trampolines forward. The boats to avoid if you plan any offshore sailing are those with bridgedecks taken right to the bows.
Furthermore, the water that goes in at the bow also has to come out at the stern, for as the bows pitch out of a wave the sterns will pitch in. So bridgedecks should also be high near the stern. Have a look at the stern of a Prout catamaran, you'll see there is very little space for the bows waves to get out. No wonder they are so noisy to sail - and the waves trying to force their way out must slow the boat down.
I do fit a nacelle on some of my designs, notably on the Gypsy and Romany. I accept the compromises as I wanted standing headroom in a small boat. But I designed these nacelles as footwells so they are as small as possible, (they are only 600mm/2ft wide). I sailed my own Gypsy thousands of miles and didn't find slamming to be a problem. Mind you, I also had a Veed bottom to the nacelle. Had it been flat then I am sure the slamming would have been noticeable.
People often tell me "I don't want a fast boat". If I reply "So, you want a slow one?" they say "Oh no!" In fact what they really mean is that they want an easy to handle, predictable boat.
Speed has nothing to do with handling characteristics, for it's easy to think of slow boats that are hard to steer and manoeuver (after all one of the most common criticisms of catamarans by monohull sailors is that catamarans are unresponsive). Many of the early English designs, like Prouts and Catalacs, the S African Dean Cat etc don't sail at all well.
One problem with efficiently designed boats is that they make little spray or wake. For example, the Strider "Striderman" shown sailing on the Strider page doesn't look as though it's going fast, yet was photographed as we sailed through the lee of a Dragonfly whose owner later reported that he was sailing at a steady 18 knots.
The Youtube clip below shows a Skua sailing fast, yet there is little wake or spray. It is hard to tell how fast it is going, that is until it overtakes a monohull (which must itself have been doing 6 knots?)
In comparison, trimarans, like monohulls, always look much more dramatic, with spray flying everywhere. Furthermore they heel and the water rushes by much closer than on a catamaran, both factors make one think you are sailing faster than you really are. I vividly recall racing my Eclipse down the Solent with spinnaker flying. Close behind was a Dragonfly 8m, also under spinnaker. We were comfortable and dry, they were clearly pushing hard, yet try as they might they could not overtake.
It is "easy" to design fast boats. I can design fast racing boats, but such boats always have a low resale value and personally that puts me off owning one. I want my customers to get good value for money from their boats so please think carefully before buying too extreme a boat. Generally racing boats have low resale values and often a short life. Certainly they need skilled crews if they are to benefit from the speed potential.
Having said that, how do my cruising designs compare to the competition?
In 1988 the CTC (the Dutch Multihull Association) held a major symposium/regatta. All the major designers were there and after the lectures about 40 multihulls had a race. In a F3 we were first to the windward mark in our 35' Banshee (despite living on board - we sailed the 400 miles each way from Plymouth). Close behind was John Shuttleworth in his open deck 35' performance cruiser, while Malcolm Tennant on HIS 35' performance cruiser was with the rest of the fleet, ie out of sight behind. At a later meeting another Banshee was voted "best looking multihull" out of 100 boats.
In a French regatta, again on a Banshee, we raced against Erik Lerouge who was sailing one of his 38ft performance cruisers. Again we beat him to the windward mark, by the end of the race he was out of sight astern.
This Youtube video, below, taken from the Multihull Sailors Have More Fun! video, shows us easily overtaking a 32ft Erik Lerouge catamaran on our 30ft Sagitta.
As has been well reported, before going cruising in my Eclipse I raced it in the Round the Island race (around the Isle of Wight, with 1700 starters, 50 multihulls). In the latter stages we overtook Mumm30 monohulls to windward. We were first production catamaran to finish, over an hour ahead of the next one, which was a 43ft Belize.
Later, when fully loaded for cruising, we spent some time sailing in company with an Outremer 43. First in Spain, then in the Caribbean. Surprisingly we found that Eclipse was faster to windward and about the same speed offwind. The owner told me he bought his boat because of its windward performance, and he was amazed we could beat him, especially as we were 11ft (3.5m) shorter.
I believe that rocket science isn't "rocket science", but that yacht
design is.
I understand the Russians are still using a 40 year old rocket design.
When I was at the Kennedy Space Center I met a retired senior engineer
who was in charge of the Saturn 5 rockets. I asked him what changes he'd
make now if doing the same trip. "The computers" he said. That was all.
The space shuttles first flew over 20 years ago, so presumably were designed
much earlier. The Concorde was designed in the early 1960's
Think of the changes made to yachts and especially to multihulls since 1968.
The easy thing to design are static things like bridges and buildings. The position of the centre of gravity is irrelevant, furthermore all the loadings are known. Vehicles are much harder to design. Harder still are what I call "interface vehicles", that is those who have to perform in two mediums, like boats do. Even a space craft is easy to design, as once in space there are no loads.
As they say, "flying is easy, landing is difficult". That is because a plane becomes a interface vehicle just as it touches the ground.
In many respects a multihull is harder to design and build than a monohull. That is because the Centre of Gravity position cannot be changed by adding or moving the ballast. That's why you should think very carefully before making what appear to be even small changes to the design.
Low aspect ratio keels are very popular on cruising catamarans as they offer a good compromise between easy sailing and cost while also protecting the hull from possible grounding damage and usually add to the load carrying potential.
Unfortunately low aspect ratio keels are also both very inefficient in preventing leeway and in increasing pitching. So it is tempting to improve them by making them deeper and shorter. However deeper keels tends to negate one of the great advantages of catamarans - shallow draft. Short keels result in even more problems. Imagine drying out and have the crew go forward only for the bow to drop as the boat overbalances! Think of the ensuring damage to the boat, never mind to the crew if this happened on hard ground!!
No wonder that - as this photo of a well known design shows - many catamarans need props under the bows and often also under the sterns (a bit hard to fit them on a beach I would have thought!)
That is why I draw relatively long keels and accept the compromise between performance and practicality.
Comfort of monohulls versus catamarans.
I thought the following email from a friend of mine might be useful as it compares sailing on both a monohull and a catamaran and is written by someone new to sailing and thus someone with no pre-conceived ideas or prejudices.
It was written after a 2007 passage on a monohull from the Galapagos to Costa Rica. Marilyn had previously sailed on Rush, the same 33ft catamaran I sailed from the UK to Canaries. (Marilyn got off Rush in the Canaries and I got on for the trip from Canaries to Panama).
Personally I found Rush to be just about the most uncomfortable catamaran I have sailed. Certainly much much worse than my similar length Eclipse. Anyway, this is what Marilyn wrote:
The wind erred on the lighter side so we rocked and rolled for a large part of the trip! The good news - no I did not feed the fish, not once. I was amazed I didn't get seasick. It was bad enough just trying to sleep and stay in the bed! That was a feat on its own. The lee cloth certainly helped but it didn't stop my head from rocking side to side. I tried sandwiching myself in with cushions and while that worked for comfort I was so hot I had a bath in my own perspiration.
I found the last part of the trip extremely tiring as my back started to ache or I felt like I had been punched in the chest, I think caused by the balancing act while I was sleeping. It was very exciting, cooking meals on a stove that is weighted to stay level so as we rocked, the stove moved. . At least I wasn't rocking and rolling around the place and that I could handle.
The day we arrived here (in Costa Rica) was such a gloriously sunny day, the sea hardly a ripple on the surface. I lay down for a couple of hours, absolutely exhausted. I had my book on my chest and didn't move a muscle for 2 hours. I died and went to heaven for a short while I am sure. The rocking and the rolling has finally stopped. At the moment all I want to do is relax and get some good sleep.
This trip has truly been a new learning curve in my life. I thought the motorbike tripping around S America was hard, I think this has been harder. How easily we forget though. I have learnt heaps about sailing. I know I can cook excellent meals with camping equipment and limited tools! I can sleep eventually while rocking and rolling when exhaustion takes over! I did arrive safely and there are times when the seas are kind to us!
Monohulls versus catamarans!
Well is there a choice!! I mean to say, a choice where everything is tied down, even straps to tie me in the galley, coffee cups 2/3rds full so it doesn't spill, being flung from side to side versus a full cup of coffee, sitting or lying in comfort outside and not being flung out of bed.
There is nothing worse than your brains racing from side to side in your head when you are lying down. That in itself answers any doubts in peoples mind regarding the state of my brain. If I had more brains, I maybe wouldn't have been to sea in a monohull!! More brains might have meant less space to move around in!!
You know, it could have been worse, there is always worse. I have bumped around in Rush at times too but then the seas were a lot worse than we encountered on this trip. Pity help it if they had been worse, I can now see why so many monos motor sail. At least to get a break from the constant motion. "
The Youtube clip below, taken from the Multihull Sailors Have More Fun! video shows our Sagitta on it's maiden sail sailing to windward in 24 knots apparent wind with an open celebratory bottle of wine on the floor. It doesn't fall over.
That might sound a strange question but what it means is; should the galley be up on the bridgedeck in the saloon, or down in a hull?
As I have said elsewhere, the majority of productions catamarans built these days are for the charter market. Charter catamarans are "floatels" and are not really lived on. Most charterers eat out as much as they can, just as hotel guests do. So a small galley is sufficent for the breakfast and snacks charterers cook.
Liveaboard and coastal cruisers, on the other hand, will need more worktop space and a lot more stowage room. They are probably going to cook underway, so being able to brace oneself is also important. Thus a corridor style galley (ie one in the hull) is ergonomic and also an efficient use of space.
If you do fit the galley on the bridgedeck then what do you put in the hulls? On a charter boat a pair of back-to-back shower compartments makes sense, but on a liveaboard boat they aren't necessary, so this part of the hull tends to become an unusable space. Meanwhile the saloon seating area is much smaller than it otherwise would be.
There is another problem as well. You have to move around the boat, so passageways have to be left clear to get down into the hulls, get to the seating areas or chart table, never mind work in the galley. All of which is wasted space.
So unless the boat is large (say over 45ft) I do not recommend a "Galley Up" design for any application. It's all another reason why you shouldn't chose a charter boat as a live aboard cruiser.
The Youtube clip below, taken from the Multihull sailors Have More Fun! video, shows first the galley of a Sagitta and then the saloon. Notice the lack of fiddles and gimbals, and then look at all the guys eating and looking out of the windows (try that on the average monohull!) while the cook steers.
Obviously two widely spaced hulls will take more time to move through the water than a monohull will, but even so tacking a catamaran should be quick. There is certainly no excuse to have a boat that is hard to tack or one that doesn't sail well to windward. A Youtube clip on the Strider page shows a Strider Turbo tacking very fast, while this Youtube clip, taken from the Multihull Sailors Have More Fun! video, showing a 35ft Banshee tacking, gives an idea of how it is done, even if one of the crew does nothing!
Having said that, people often confuse windward ability with a narrow pointing angle, but really what everyone wants is the highest "speed made good" to windward (or max VMG). Monohulls can't sail faster than their hull speed so the only way for them to go quicker is to improve their tacking angle, hence the pointing fetish. That's not the case with catamarans which can just go faster and faster.
Thus comparing an Eclipse with a Mumm 30 in 20 knots of wind and flat water, the former may do 8.5 knots and 85 degrees between tacks and the Mumm 7.8 at 75 degrees. But Eclipse still ends up first at the windward mark. It may surprise readers, but if I want to beat a 38ft monohull to windward (which I can do with Eclipse), I wouldn't want flat water and light winds. Rather I'd want big seas and a F4 or more.
This Youtube clip, again from the Multihull Sailors Have More Fun video, shows a Banshee beating to windward in 20-25 knots apparent wind. The shots were taken from my Sagitta, the Banshee was faster in these conditions. And we were both comfortably (in all senses of the word) faster than the Sigma 38 monohull, just visible behind the Banshee.
Although the Strider and Merlin look very similar on paper, I know, from having owned and sailed both designs extensively, that the couple of extra inches on Strider's hull width makes a huge difference.
However even on Merlin there is still room for a snug single berth in each "corner". The forward ones are comfortable for weeks at a time, the aft ones are narrower and have less headroom, so are better for children or occasional use.
It is really important to have "a place for everything and everything in its place". This is especially true in the galley which can either fold onto the side of the hull or across the boat, even though the latter makes access to the bunk difficult. Side entrance hatches suit this accommodation layout, but mean you can't stow long items in the hulls (like the mainsail or boom when trailering)
Net bags on the hull sides make great stowage areas, while a Portapotti toilet is best positioned under the companionway hatch where also can be used as step down.
These comments also apply to Wizzer and Skua, although both have roomier hulls than a Strider.
This Youtube clip, taken from the Day Sail to Russia video, shows a well laid out Strider hull
Of course a deck tent or cuddy transforms life on the open deck boats. A cockpit tent need not take long to put up, as another Youtube clip from the Day Sail to Russia video shows.
However it cannot really be left up when sailing and is still a "tent". So the cuddy designs make a lot of sense. The Wizard and Sango have purpose designed cuddys, but the Plan Updates page shows one we retro-fitted to our Merlin. A similar one can be used on Janus, Strider and Skua.
Crossbeam Design
There are two stages in creating a successful catamaran crossbeam solution.
First you must DESIGN the structure, only then can you CALCULATE it. The former is usually the more important and certainly the one most people get wrong.
There are several factors to consider when designing crossbeams:
First, you need stiff crossbeams, not just strong ones. Fortunately stiff
beams are nearly always over-strong. By stiff I mean one without any obvious
deflection. Engineers normally consider that to be 1-2% of length.
Why a stiff beam? Well imagine crossbeams made out of rubber. They would
never break, but would be so flexible you could never keep the two hulls
in line and the mast would fall down as the rigging flexed.
How can you make a stiff beam? Well, actually it’s not just the beams that you want stiff, rather it’s the boat as a whole. I’ve found that the best way to do this on an open catamaran is to have two crossbeams plus a separate one to take the mast loads. The actual positioning of the beams is also very important.
Although crossbeam size and placement is often complicated by rig and accommodation considerations, the beams must take priority! If they are too near the middle of the boat then the bows can flex up and down and you cannot keep the rig tight. If too close to the ends (especially to the bows) there isn’t enough boat to take the loads and, furthermore the beam cantilever is longer.
Having the first crossbeam almost at midships was the most spectacular mistake the Team Phillips designer made. Pete Goss and I are members of the same sailing club and other members were upset when I expressed concern about its design. After the breakage they realised what I was on about.
Once you’ve designed the structure it’s really a trivial problem to calculate the necessary scantlings. If you use a strain energy analysis you’ll find that the loads will dissipate quite quickly into the hull. Indeed it’s extremely rare for beams to break off the hulls. Usually the problem is the beams themselves breaking.
Fortunately it’s very easy to check the strength of catamaran beams once you’ve built them. You simply jack the boat up with a support under each bow and each stern. Then take one of the chocks away. The boat shouldn’t move appreciably. It looks scary, and is certainly a load that you wouldn’t get at sea. But is very reassuring all the same.
You can see a photo of our Merlin Tucanu surviving this test on the “Review of 2007" page. The Merlin and the similar Strider design use two aluminum tubes with inertias around 500cm4. I usually use ply and timber beams as they are easy to make and to attach to the boat (and of course to attach boat to them), but they are heavy (approx 1.5 x the weight of aluminum tubes).
It is not just open deck boats thant need good crossbeams. Unlike most designers my bridgedeck catamaran designs also feature big beams. Apart from a big netting beam there will be one under the mast and one under the aft end of the cockpit. I design the anchor lockers and forward end of the bridgdeck to act like another beam. By adding theses beams I ensure that the boat is extremely stiff and that it is not a problem fitting big deck hatches or large companionway doors. I have seen many production bridge deck cabin catamarans that rely solely on the hull/deck mouldings for strength flex, and even crack, bulkheads because they are simply not stiff enough.
On a large, say 40ft, 7ton boat, beams that are strong enough may weigh 400kgs. Ones that are too weak will still be heavy - they may weigh 300Kgs. It’s NEVER worth trying to save weight in your beams. Carbon beams may weigh 250Kg at a huge cost. Is it worth spending that much to save 150Kgs at best? I’d rather spend the extra money on better sails and deck gear.
