Sailing Catamarans

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Updates to Plans

All plans - please read before building

Although we spent a great deal of time and effort in making our plans available in electronic format unfortunately a few errors crept in.

So please use this page to update and correct the download drawings. Some of the errors we have noticed ourselves, but please let us know of any more so that we can update this page and make the download drawings as accurate as possible. To make it easier for you to print out the revised drawings and us them in your workshop I have uploaded them as PDFs

This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Thank you

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General Notes:

The normal method of marking out plywood bulkheads using full size patterns is to lay the pattern on the plywood. Then "prick though" the pattern with a nail or bradawl at say 1in or 30mm spacing. Remove pattern and "join the dots"

Some of the Materials Lists still suggest using resorcinol glue. However this glue is now outdated. Now I recommend using epoxy throughout, but you can use polyurethene glue for strip planking and also for non structural or lightly loaded above water joints. Always use epoxy below the WL.

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Rudder blocks

The kick up rudder system I use on many of my boats works very well. However the blocks need to be carefully made for best results.

They do not want to be tight in the slot or they might jam (which is why it is probably not a good idea to use solid unsheathed wood as it can swell if the rudders are left down for long periods). But neither do they want to be loose as then there will be a very annoying rattle when at anchor.

So what I usually do is make the block as snug a fit as possible and then add a vertical bead of Sikaflex or 5200 to the sides of the block. Not only does this act as a fill-in if the block is too narrow, but also acts as a soft bumper and reduces any banging noise.

Furthermore the block should extend behind the transom at least 50mm so that when you tighten the downhaul rope it pushes the block forwards.

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Waterlines

While your hull is still upside down you should mark the waterline all round. The boat is already set up square, if you don't do it now you'll find it much harder to square the boat up once you've turned it over. You can use a laser level or the more traditional watertube

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The following changes list the designs in alphabetical order so please scroll down to see your boat details

 

Eclipse

On the lines plan the bow height should be from WL1, not WL2.

(The arrow is wrong, not the dimension)

 

Flica

Click HERE to see a new mastbeam arrangement

 

Gypsy

Daggerboard

The total length of the board is 3050mm and the part below the waterline is 1350mm

 

Janus

Sheet 1

Although the Janus plans have been selling well for nearly 30 years, it is only recently that I learnt that my bulkhead pattern sheet doesn't quite work. So here is a better layout, as drawn by a builder.

Sheet 2

Keel panel dimensions
Reading from aft the half widths are 137, 145, 170, 195, 205, 210, 205, 190, 165, 125, 70, 16. The spacing is 600 except 140 for the two aft widths.

Setup Note 6) Fix string to Bhd 4 on WL/CL intersect (bunk top). Pull tight and horizontal (check with spirit level) through Bhd 5 to Bhd 6. Temporarily clamp legs to Bhd 6 and offer up and adjust height so that string and WL are horizontal. Screw legs to Bhd 6 and brace as before (see 2B IV)

Setup Note 9) Fit side stringers, beginning at the keel and working down. Fit port and starboard stringers at the same time. Check that hull is not twisting as stringers are fitted. Glue and screw as 8) above. Note: if stringers are not long enough they should be scarphed together before fitting, see sketch at 2B1. Stem see VIII, IX, X

Sheet 3

General Procedure Deck Framing
Note: Interior should be finished and painted before fitting any deck framing
After fitting cabin shelves (see 3AXI) begin fitting deck framing at bow and work aft.
Check that stem, Bhd 1, 2 and deck beams 1, 2 form a fair camber curve before decking, plane as necessary.
Hatch side coamings are fitted after decking - see Sheet 5
Before fitting sloping cabin front the foredeck should be fitted to deckbeam 3 and forward beambox
Find deck beam 3 position by holding straight edge (or timber 'A' in sketch 3BIII) from Bhd 4 to Bhd 3 and then to gunwale
Bed central roof stringer on epoxy filler on foredeck - position depends on own boat - see Sheet 5
Deck stringers need slight bevel before decking. See Sheet 5

If you want to fit LAR keel to your Janus there is a pdf drawing HERE

 

Merlin (also suitable for Janus and Strider)

We spent the 2006 season sailing our Merlin Tucanu. This was the first time I had cruised an open deck catamaran for 15 years (but I did cruise and race a Wizard in the mid 1990's) As a result I have a few ideas that will improve both comfort and performance. The sketches are given to give you an idea. I am not offering these changes as detailed plans, but those of you who have already built your own boat should be able to make something similar without any problems. They are drawn for Merlin, but should also work, with modifications, on Janus and Strider.

1) I like telescopic tiller extensions, one on each side. However they are very expensive. So I got telescopic boathooks, removed the ends and fitted a universal joint. Total cost was 1/4 the real thing. After several seasons heavy use they are still working well.

2) To reduce forestay sag and mast loads the new Tucanu rig has a bowsprit and a forestay that is 500mm aft of the original position. Thus the genoa is smaller (and so easier to handle) while we are fitting a new larger racing mainsail, see below

3) Many people now use a "squaretop mainsail" for racing. This is very similar in concept to the mainsail I made for Cockleshell Hero back in 1980! We ordered a triradial carbon sail from GM Sails in Australia. CLICK HERE to see the new rig. But please note that the Strait of Georgia, where we race, is an area with predominately light winds and flat seas. Unless you are very experienced this rig may be too powerful for English Channel sailing, for example.

4) The Shadow/Strider Club had a deep mastbeam which we found a big improvement over the standard beam. The new Tucanu beam is shown HERE. It also has the advantage that the mast foot and hence boom is higher (note you will need longer rigging). If you do not use this deep beam and have a wide beam version of a micromultihull then I recommend fitting a dolphin striker under the mast beam to limit deflection.

5) The micromultihull daggerboards were originally drawn to make the best use of plywood sheets. However for optimum performance you can extend the length of the boards between 250 and 300mm.

6) Maybe we are too old for small boat cruising, but we like more undercover space. So we are making a small cuddy. This will be removable when racing and will fit in our truck for transport. It can have a fixed nacelle or a "pop bottom" as used on Wizard and Sango. The bottom needs to be 9mm ply, but the rest can be as light as you dare. You may also need to recut the genoa to fit.

The photo shows the almost complete cuddy being fitted to Tucanu's deck

To see the general cuddy details CLICK HERE

To see the cuddy dimensions CLICK HERE

To see the pop bottom details CLICK HERE

Note: If you plan to trail regularly then I suggest either having no nacelle, or fitting the pop up version. That is because the fixed nacelle makes it harder to slide the cuddy off the boat and it takes up more room on the trailer.

These drawings make the cuddy look large, so CLICK HERE to see the cuddy with rig above - much better visually! You will notice that the boom is angled up to give yet more room as we found ducking under the boom hard on our backs and knees. This change was easy to make, as we simply cut the sail along the first seam.

Just to repeat, these sketches are to give you ideas. At this stage I am not going to draw detailed plans.


"I just want to thank you for the cabin plans you put on the web.

"I have used ideas from those plans and the open Strike cabin to build a cuddy to suit me and my wife for our Strider - a suitable shelter for daysailing which can easily be converted with a tarpaulin (or in the future something more sophisticated) into a night time cabin.

"It looks much better than I hoped and as soon as I get it on the water again I will be able to find out what it is like in practice - but I am confident it will fulfill my needs.

"All the best and thanks again,

"John, owner of Strider no37."


 

Pixie

Materials list
The metric measurements are the final timber sizes. But many builders use thicker pieces of wood as they are easier to obtain, and they don't then bother to plane them thinner. There is no problem doing that if you want to save time.

Deck jig
1 sheet 8ft x 4ft.(2440 x 1220mm) 12mm thick chipboard
Approx 6m 2" x2" (45 x 45mm) and 10m of 3" x 1" (70 x 20mm) rough sawn timber.
Misc
Copper wire 10m minimum (we use old household wiring)

Bulkheads

Bhd2
217 width at deck, 95 width at 150 above keel, 47 deck camber
Bhd 3
40 Deck camber
Transom
88 width at deck, deck camber 8, 150mm above keel width is 55, gunwale is 150+127=277 above keel

Deck Jig

Reading from the left of the drawing the measurements are: 5, 140(horizontal dimension), 30, 100, 150, 183, 195, ALL 500 (horizontal dimension), 195, 180, 145, 90, 140 (horizontal dimension), 70 The cutout in the jig doesn't have to be too accurate as the ply will form a fair shape.

Rudders

The rudder drawing reads: Steering is more positive if "Ackerman Linkage" is used (as on the front wheels of cars). This can be done by making cranking tillers (angle in 10deg) as shown dotted below

Mast

The 3225 means 3.2in x 2.5in (80mm x 60mm) as a minimum. Most beach cats use similar spars so there is no problem using second hand spars from other boats. You just have to accept a few odd holes here and there, but I have never found that to be a problem.

The mast can be longer if you want more head clearance under the boom.

 

Quattro 16

Notes for Quattro Full Size Patterns

It is important that the patterns are printed out at the correct size!! Print out on A1 paper

Sheet 1 Bulkhead Patterns

Total Vertical Distance BHD4 must be 565mm

OR if you cannot easily print out the full size patterns you can use the following offsets. Draw a fair line through all points. NOTE: You will soon discover that the "stitch and glue" method used is not particularly accurate as the plywood forms its own fair curves. Thus the bulkheads may not fit exactly.

Use the full size pattern drawing for other bulkhead details

BHD 1

Height gunwale to keel 492
Max Deck Camber 18
Gunwale half width 100
Then half widths at 100mm spacing working down from gunwale to keel
92, 83, 67, 41
Keel width 0

BHD 11/2 (note this is a half height bulkhead)

Height gunwale to keel 282
Max Deck Camber 0
Gunwale half width 122
Then half widths at 100mm spacing working down from gunwale to keel
93, 49
Keel width 0

BHD 2

Height gunwale to keel 532
Max Deck Camber 43
Gunwale half width 206
Then half widths at 100mm spacing working down from gunwale to keel
188, 162, 135, 93, 41
Keel width 20

BHD 3

Height gunwale to keel 516
Max Deck Camber 72
Gunwale half width 246
Then half widths at 100mm spacing working down from gunwale to keel
220, 188, 151, 106, 37
Keel width 23

BHD 4

Height gunwale to keel 498
Max Deck Camber 67
Gunwale half width 233
Then half widths at 100mm spacing working down from gunwale to keel
205, 174, 138, 91
Keel width 22

BHD 5

Height gunwale to keel 400
Max Deck Camber 38
Gunwale half width 170
Then half widths at 100mm spacing working down from gunwale to keel
142, 112, 72, 26
Keel width 22

Transom

Height gunwale to keel 295
Max Deck Camber 15
Gunwale half width 100
Then half widths at 100mm spacing working down from gunwale to keel
77, 46
Keel width 12

Sheet 2

Hull Centrelines on Cross Section Setup for Fitting Keels Horizontal Distance must be 195 mm when printed out

CLICK HERE for a dimensioned sketch of the Quattro 16 keels (pdf)

The mast length given is the minimum. For more headroom under the boom the mast can be lengthened (and gooseneck raised)

 

Romany

After living on board our Romany for several months I realised that a few changes would improve what has already proven to be a very comfortable cruising boat.

1) Few people use chart tables these days, preferring to use a chart plotter. Thus a chart storage area (for of course one should still always carry paper charts) is all that is required. Therefore I suggest moving the starboard hull companionway hatch forward to line up with the chart table. Doing this means that the aft bunk area can become a cabin, rather than just a bunk.

2) When seated in the cuddy there is a lot of headroom, thus wasted space. The seats can be raised so they are in line with the top of the mastbeam. The space under can be used as extra storage. Obviously the nacelle will need a double bottom so your feet touch the floor. I suggest finishing the raised floor area in line with the forward end of the galley. See sketch HERE

3) A rigid Bimini can be fitted over the cockpit. The cockpit seats are shown HERE

4) A bigger roached mainsail will make a difference to performance, but does require extra battens and better quality cloth so is significantly more expensive than the standard rig. Dave Calvert made a great sail for us. If you want a similar one please contact him direct, or me for a sail plan.

5) The cuddy table can have an end flap that folds up and over onto the existing table top and is then a fiddled storage area. Folded down it allows 2 more people to eat at the table

6) A fold down flap can be added to extend the galley work surface on the port side, although I don't think it is a good idea to make it a fixed shelf.

7) Ventilators should be fitted in the transom steps

No detail drawings of these changes will be supplied, but photos of the modifications to our own boat will be posted as soon as possible.

It seems that the original builder of our Romany did not make a full glass joint between cuddy front and roof. There should be a minimum of three layers glass on each side. So small stress cracks appeared. Just to be on the safe side I suggest making the top of the kingpost as shown in the photo below. Note, the thinness of the post is an optical illusion! The post should be glassed in place all round.

 

Sango and Wizard

Wizard Hard Chine

A builder has pointed out a mistake in the offsets for the Bhd 6 and Transom. (The full size patterns are OK)

Bhd 6

Sheer Height 676mm: Sheer Width 367mm: Upper Chine Height 372mm: Upper Chine Width 362mm: WL Width 223mm

Transom

Sheer Height 673mm: Sheer Width 287mm: Upper Chine Height 380mm: Upper Chine Width 280mm: WL Width 123mm

Sango

Use the hull spacing dimension from the drawing, not the photosheet. It should be 3700mm

Round Bilge offset table

Although the full size patterns are correct I still include an offset table for use as a check. I recently discovered a couple of errors in the table:

Frame 3 WL2 should be 215
Frame 4 WL3 should be 188
Frame 5 WL3 should be 202
Frame 8 WL2 should be 217

Daggerboard Position

The drawings show the daggerboard cases fitted on the outside of the hull. That is so that they do not interfere with the wing lockers. However the photo sheets show the daggerboard case on the inside of the hull. The builder whose boat I photographed chose this position to make it easier to reach and adjust the boards.

There is no real difference in performance between the two positions so the choice is yours.

Sango and Wizard Basic Hard Chine Materials List

Hull planking 12 sheets 6mm ply 3 sheets 9mm ply
Decking 6 sheets 6mm ply
Timber 2in x 1in 200m 1in x 1in 100m
NOTE: all plywood to be best quality gaboon (okume) marine grade
All timber to be best quality softwood eg Douglas fir, sitka spruce, yellow cedar or similar.
NOTE: Timber sizes are nominal. Planed all round (PAR)
Glass sheathing 300g glass cloth (hulls) 36sq m 200g glass cloth (decks) 12sq m Epoxy 30kg min Fastenings Either 1in counter sunk stainless steel self tappers or gripfast/anchorfast barbed ring boat nails Approx 2000 reqd

Wizard needs 3 fewer sheets 6mm ply

Raised hull cabins

These are removable and will fit nest one inside the other and fit on the cockpit for transport. Adds headroom and light to the hulls. CLICK HERE for basic drawings

 

Shadow

Bulkhead dimensions

Bhd 4 sheer height is 684 (not 634)

Bhd 6 aft deck height above gunwale is 89 (not 97)

 
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