Advice needed on trimaran

If you are talking about 16 or 17 ft long hulls, you can get by with 1x2 gunwals, and 1x1 stringers with 1/2" or 3/8" plywood bulkheads, should be plenty strong.

If the fabric you buy is untreated/coated, than yes you either tack, staple or hand stitch the skin tight over the frame and than paint it after to seal it. thin first coat to it soaks in, than apply remaining coats all from outside until weave is filled (usually 4 or 5 coats).

 

Mark, thank you for so much information.

I know that downscaling hulls requires to modify shapes, but I do not know what exactly changes. For this instance, you say scaling down USA 17 will not work - I had that fear - but could you explain why not? What could go wrong?

Well, I have to agree with what you say about advantages of folding hull. Mobility and storage space are very important for me, as well as safety - people in our country sometimes steal even sewer manhole covers.
Question is, can I make 3 folding hulls under 400$? If so, how? Could you please tell more? I looked up in Yost site, these are great plans, and these hulls look like they could last forever, but that is completely out of my budget. So can you help me here?

I checked for Klupper (google refers to it as Klepper), and found 2 or 3 people selling used canoes, however, it is starting with 325$ per canoe. No one is selling carcass separately.
So I think I won't go far that way...

There is some trouble with that, too. Even if I find used canoe carcass to buy (luckly 2 identical and one a bit larger for center hull), canoes are optimized for paddling, not sailing. I heard they don't perform well in high speeds. From your example, I would go with hulls that sail at reasonably high speed, and paddles at half that speed. For that, I need custom hull shape, which I hope to create with DelftShip (which I'm learning to use now). Even more important, I'll need to integrate centerboard, and that can be tricky and dirty installing on Klupper or any other second-hand canoe, while on custom shape, I can make space and reinforcements for centerboard more easily.

As for making folding hulls out of wood, I did not exactly understand how you propose to do that. Cross sections out of plywood, stringers from lumber, and those tubes to join stringers - from metal? Do I understand correctly? Talking of broomsticks, I guess if I had to replace all stringers with round wood, we would be talking about some serious weight!

What would be advantages and disadvantages of folding wood construction versus aluminum and HDPE like Yost suggests? I guess it would be cheaper, but not so long-lasting? What about weight and reliability?

P.S. One more question: what are best methods of joining that PVC material waterproof and strong? For example, I'll need to join edges of cloth at bow and stern of each hull. Maybe heating? Gluing? Stitching?

 

Yost has good current experience. He has designs that can be built for under $300. He has folding designs that would likely be $500 or more. The majority of the cost is the aluminum tube. He also has wood, non-folding designs. A folding wood design will weigh more and will have issues of wear at the joints. The Klepper is a very reasonable design, and it weighs close to 100lb. If you can get the aluminum and HDPE, I say they are worth it. I would start with the sonnet designs (the under $300) and add structure to support the sail rig.

 

Well, actually, if I pay 325, even 300$ for hull which does not need new skin, I only have 100$ left for outboard hulls and beams which join all 3 hulls together, and there is also a rudder. Not to mention the web which will be between hulls (like in USA 17 or any larger trimaran. It's just a waste of space not to add web. And with it, I can sit anywhere, balance out - therefore, carry far more sail). And there is a problem of hull shape I mentioned. Nah, I think I better build it myself... I really can't push that budget. It is already a bit over my head. I also have to make a mast and sails...

As for leeboard, I have considered it, and I red from various sources that although it is easier to build, the advantages end just there. I'm willing to put in extra effort for quality. Daggerboards are possible, I just need that thing retractable, so I can put my ship in and out of water with little problems, also sail shallow waters.
Why do you say that daggerboards are better than centerboard here?

Well, as for wood versus aluminum, if I build folding hulls, weight is not an issue - as long as trimaran won't sink when 4 people climb inside. I really doubt I'll find enough HDPE and aluminium under 400$ for 3 hulls, but I'll try.

I found this site (watch introduction movie) where they build just this - folding wooden canoes. I think I can get some ideas from it. Also this highly detailed photo from Wikipedia shows some very fine solutions which I hope I can copy from eye. What do you think?
And by the way, why do they varnish these carcasses instead of painting? I thought varnish lasts far less, especially in contact with water.

 

4 people? All I have considered is 1 or two people -4 is 1000lbs minimum rating. I have no idea how you can build a good fast trimaran for 4 for under $400 and I have never seen anyone who has. My 29ft 2 ton trimaran was designed for 4, 6 on a daysail, 8 overloaded.

Focus on the russian site. The US places too high a value on life to consider such a boat.

 

No, no... Racing configuration of course is 1-2 people... 4 people is for slow cruising... Sorry that I made myself unclear. It's just that my catamaran I built this summer could sail to windward with 1 sailor only. 2 sailors - and it's too heavy to go anywhere but off-wind.

So don't mind that about 4 people. I just don't want my trimaran to sink.

 

buying HDPE or hypalon fabric is way too costly for your budget, and those links above show heavy and complicated hulls, you do not need that. those people have been copying obsolete designs that are too heavy, take too many parts to build, they have no imagination on how to do it simple and with less cost. I highly recommend you make three non-folding lightweight hulls and have them detach from the beams for transport. all you need is lashings or bungee cords to attach the outriggers, the cross beams can be lashed to the center hull. Keep it simple and costs will stay under control.

Any low stretch fabric will work, you stretch it over the frame and paint it with what ever water resistant paint you can find. Polyurethane works well (tough), but you can also use latex (not as durable but cheap, reapply regularly), oil based paints have been used for many decades, also cheap and tough, if you can find it.

I can build a frame like the one below for about $40 paying retail for everything, you can use the same construction method but make the outboard hulls narrow, and the center hull more like a canoe to give you more capacity. the beams can carry a light deck so you will have plenty of room for passengers.





Way to adapt skin on frame construction to other hull types:



Here is something close to what I have in mind, just add another outrigger and you have your trimaran:



so if you pick a design and just get started, you will have a nice low cost boat fairly quickly.

 

Well, you see... There is much sense in what you say, but there is also a lot in what Skyak says. If I make it non-foldable, I'll have some (probably solvable) problems with transportation, and huge problems with storage and safety. See what Skyak wrote...
Petros, what about foldable wooden hulls? Like the one from photo from Wikipedia I provided. It doesn't seem much more complicated than similar non-foldable hull. It should weight more, yes, a little more work, but still way cheaper than HDPE and aluminum, and maybe just a little more expensive than similar non-folding construction. I would only need to add some metal parts which join stringers and beams... Right? Why are you so against folding construction?

Sorry for my many questions, it's just that Petros and Skyak highly recommend different approaches, and I'm a bit lost. Thank you for your both time anyway!

 

I have built both folders and non-folders, and know of others that have done so. Folders are a lot more work, two or three times the effort and cost. If you have no other way to move it than you are stuck and that approach will work, but those hulls I posted above only weight in the 20 to 40 lb range, they should be easy to move on the roof of a car. I have traveled long distances with up to 3 skin on frame kayaks or my SOF sailboat on the roof of my 1984 Toyota Tercel, it only has 62 hp and is 14' long, but have moved boats over 18 ft long with it. I can not see how moving complete hulls around can be that big of a problem when they are that light.

the Yostworks web site has good instructions for making a foldling kayak, you can use plywood instead of HDPE (costs less), and wood stringers with short length of pipe connectors for the wood stringers. Most important is to keep it simple and keep the number of parts, fasteners, etc. to a minimum. With a non-folder the whole hull has perhaps 20 parts total (not counting the lashings), a folder would have way more, lots of parts to assembly and lose. Takes over an hour to get underway if you are folding the hulls and than assembly skins, beams, sail, etc. With non-folding hulls you can be under way in 15-20 min. It is just much simpler, lighter and less costly to make hulls that do not fold.

Your choice. If there is no way to store three long thin hulls where you are at, than you have no choice and must make a folder. The fabric skin will be much more costly, will weight more, you will need a way to tension the skin to get it tight, you will need lots of small parts (as you can see in the pictures of the folders), lots of things to make, lots of things to break, lots of things to loose every time you take it out. But if you have no choice that you are stuck with the more costly way to go.

THat is all I am saying, you will do yourself a big favor if you can get by with just removing the hulls from the beam and store them as complete hulls. Saves a lot build time, build cost, and launch and break down time as well.

 

The only things I have to add are

I think you are not clear on how much more demanding it is to build a trimaran capable of sailing with 4 at all. The size of everything more than doubles. In wood it would be so heavy that 1 man could not carry it at all. There are no 4 man folding boats to show how it can be done -you would be the first. As such, I must admit, I have no idea how or if you could build one for $400.

Petro is right that all the wooden folders you have seen (besides Yost) are the same old design popularized by Klepper. I don't see this as a negative, they are proven, and for carrying over 700lbs they are as good as anything. By the way, the designs/construction technique of the boats in his photos are thousands of years old.

The only things I have to add about the the non-folding skin on frame;
-the first thing you need are flawless pieces of the right wood, longer than the hull you intend to build. I think those are white oak, quarter-sawn.
-the next think you need are many short (1 to 2 times beam) flawless pieces, and the ability to steam and bend them into at least 20 unique precise shapes. Yost cuts shapes out of plywood -not as pretty.
-the next thing you need is the ability to mortise and tenon.

All of these things can be done but require tools, materials and skills you don't have yet. I assure you that all the pretty hulls pictured above were created in shops with more than $400 worth of tools. I should also say that builders of such boats enjoy the work greatly. Also note that of the pictures of SOF boats Petro posted, only the proa at the bottom has sufficient structure to make a 4 man multihull. All the others assume a light. distributed load.

You asked why skin on frame builders varnish rather than paint frames. Mostly to show the pretty wood off, but also to not hide any degradation like splitting, rotting, checking... that could lead to failure.

Concerning the skin, I think the reinforced PVC material you found is a reasonable cost and capability (It's the only useful material you have reported available). There is one benefit to using regular weave and painting like Petro says -material fits better before it is sealed, painted, impregnated because the weave can shift diagonally.

Concerning folding or not folding, if you can get long flawless lengths of suitable wood, non-folding is much easier to make a strong boat. If you can't get long flawless lengths and must join them anyway...
The added difficulty of the folder is in the joints. Less joints, less difference. You could make a 16ft folder with 8ft sections.
Another consideration -the non folding construction is self fairing. The continuous straight lengths tend to make smoother boats.

That's all I have to add.

I know my values and I am satisfied I have communicated them. A folder takes twice as much... To me it's worth it. Can't build a 4 man for the price -consider a smaller boat or a bigger budget.

If you want the big boat/small budget I can't help you. Petro has an idea, see if you can find suitable wood and tools.

For designs and proportions, take a look at Kurt hughes line of small tri's. Note the smallest one rated for 4 is 23ft.
http://multihulldesigns.com/daysailer.html

 

Thank you both. Well, I'm sorry about that I thought of this trimaran being able to carry 4 people - I must have misjudged. I see that was a bit foolish. Sorry. I'll then expect for 2 or max 3 people trimaran. That is possible, right?

I don't expect to find flawless wood, but I'll try.

Speaking of wood, what about drying it? Last time I bought a plank 15cm wide for my catamaran, it ended up 14.5 after non-deliberate drying for a few months (it messed up my design a bit). How I should deal witht that? Should I dry the timber, and then cut the pieces, or cut larger pieces to account for shrinking (pretty hard to calculate what will end up).

I'll consider both folding and non-folding, as there is no time pressure for now.
Anyways, I fail to see why folding hull should be more expensive than non-folding. Skyak, you said that for non-folding I need flawless wood, while for folding, I can get away with lesser wood. That suggests that flawless wood is more expensive, therefore, adds to price of non-folding?
Of course, I expect the higher price of folding one to come from joints. But are there that many joints? From photo from Wikipedia I see that stringers were connected by metal panels which jacket 3 of 4 sides of a stringer. And then screwed together, I believe. Screws are cheap, these panels - I have worked with them, their price is reasonable, I believe I can make that shape with clamp and hammer. There are some corner joints, and well, that's all? I expect it would add up to 5 kilos to total weight per hull, and maybe 50$ maximum for all 3 hulls?
If so, what am I missing? Not that I'm ignorant, I just don't see it.

And please forgive if some of my questions or considerations are stupid or annoying. I'm trying to learn...


And I believed I promised to make compilation of photos in youtube of my catamaran, but I did run into some technical difficulties, so I'll just show these photos on facebook, if you are interested:
https://www.facebook.com/media/set/?set=a.4527778842248.2177559.1524256570&type=3

It's open for all. Sorry, all descriptions are in Lithuanian, so I'll translate them here, if you are interested:

Actually, I'll upload English descriptions in facebook in a moment. Just click "see more" beside each photo, there will be English description below Lithuanian one.

Photo 1: "The Drop" (like a water drop) is a small home-made catamaran for 1 or 2 people, built and launched on August, 2012. Why? There are things which deserve the right not to have some special purpose. Sailing is not a lazy sport, but there is also some unique magic in it. In these times, when so much of our life is automatized and simple, surfaces a wish to shed away the sheets of comfort, and stand alone against harsh wind, to bend and steer the force of nature... The budget of this boat is minimal, it was built from various obtained, given, bought, found materials - from sewerage pipes to cocktail straws...

Early stage of development, in photo - my brother, who is annoyed to the bone by the sound of a drill.

Photo 2: One of many experimental assemblies in shore. Mast isn't fixed at all, hold only by professional climbers rope (red), donated by Irmantas Saulius. Without his help ship would have never succeeded.

Photo 6: Mainsail hosting and shaping was a huge headache for about 8 days until I found working configuration. In this photo you can see how sail is wrinkled...

Photo 7: ...and in this - how gaff jaw wants to twist.

Photo 8: Ropes, lines... There are never too many.

Photo 9: Day before launch, final inspection, everything is assembled except that hulls are not joined together yet.

Photo 10: These two sewerage pipes, which were a base of "Drop's" buoyancy, were donated by "Wavin" factory logistics department director. Without her help, the price of this ship could have doubled.

Photo 12: First launch - with my brother. He helped me with the sails - and to paddle back if ship fails to go to windward. Sadly, we had to paddle.

Photo 13: Support team...

Photo 14: Opinion of the experts: "THIS will sail? Stop joking..."

Photo 15: Captain's hat adds to the sedateness of the ship.

Photo 16: It is said that rats abandon sinking ship first. So, it is quite reliable method to see if a ship will sail - put a rat in it. My family said that no rat, dead or alive, will ever set foot in my ship. As a matter of fact, captain can have his own personal rat for checking ship's seaworthiness. Apparently, captain's rat would abandon sinking ship after all the other rats...

Photo 17: First sail hoisting in water. Not without problems... And then, traditional calm.

Photo 19: One of a few moments when construction errors and inaccuracies worked against each other, and sails shaped nicely, and "Drop" just flew...

Photo 21: Victorious wave after a successful stage, which could also be interpreted as a dramatic goodbye... Ship wasn't in a mood to get back to windward harbor.

Photo 22: After 8 days, countless upgrades and remades (sailing experts will see), catamaran achieved sufficient quality to sail to windward. That was the main objective, because downwind... Even sh*t can go downwind.

Photo 23: Now "Drop" was flyin'. I made two successful long trips to open lake, with different conditions - from light breeze which you can't even feel on your face, up to breaking waves, gusts which heeled ship on it's side, so that even windward hull was flying.

Photo 24: This ship was designed for about a year, built and upgraded about 20 days (full working days). It took a lot of patience, stubbornness and love, but one thing that it couldn't miss - the support, help and encouragement of my friends and relatives. Special thanks go to family and my good friend Marius Ivaškevičius - without his professional critique, advise and suggestions I would have probably sunk in harbor.

Photo 25: Only for two last days before leaving Sartai lake "Drop" earned it's name, fulfilling everything I had in store for it. There was a lot of wonderful sailing. Who tried it, will know...

However, due to unpractical construction and non-folding hull it was impossible to transport it with a car. Even more, hulls were leaking water, and deck was starting to rot, soaking with water, and counting it's last days. With heavy heart I took an axe into my hands, and reduced ship to pieces, took it to a dump yard...

Photo 26: But why "The Drop"? Because a drop in the sea. Longs to be in the sea. Longs to roam the broad waters. Because a drop after drop can hole a stone. Good luck and patience to all the persistent, in whatever you do!

 

if you are looking for boating perfection, built like fine furniture, that is true. I have built pretty hulls like the ones I pictured, took lots of power tools and about 100 hours each hull. But the native Alaskans built skin on frame kayaks with a big knife and a hand drill/awl, their hulls were not pretty but strong and functional (and even crude looking by modern standards).

Here is the other extreme; I have built a 2 man large skin on frame canoe with a sail rig, for $75 worth of stuff bought from the hardware store, and we only used about 5 lbs worth of tools: a cordless drill, a hand held jig saw, a few bits/tips for it, a hand saw, a sharp knife, a staple gun, paint brushes/roller. It took my partner and I 14 hours to build from raw stock, plus another 4-5 hours painting/decorating/fit out. Perfect lumber is not necessary with careful selection and locating defects in low stress areas (towards the ends of hull). We still have the boat three season later with minimal maintenance.

We built a light two man trimaran in 12 hours (though it just barely floated two adults, 4 person boat would require twice the displacement), also with the same tool set for about the same cost (we bought 1x2 stringers ready made, no need to rip the wood).

These were part of a boat building contest where cost, weight of tools, time to build, design and results in a race around the lake were our total score. We came in second place both times, won the race in the tri but our points total puts in 2nd overall. both times we had the high score for best design and workmanship.

You do not need a lot of tools or a lot of money to build a fun boat to use, just creativity and determination. If you stop looking at the way expensive commercial boats area built, and look at how traditional native water craft are built, you will find inexpensive ways to build decent useful and fun low cost boats.

 

laukejas,

I just looked at your photos. that is a pretty complex sail rig for such a small simple hull. Nice job but I suggest you stick with a single cat rig. I like junk rigs because they are easy to handle, easy to make, they have low stress on the parts (so they can be light weight), and are efficient for all points of sail excpet when trying to point high.

here photos of our Quick and Daring contest boats:


"Puff" built for about $60 and with a few hand tools in 14 hours (two man crew)


this shows the "Puff", sail plan; twin cat rigged modified junk sails.


this shows 14 ft sloop I built for less than $50 (all salvaged lumber and most parts). Still have this one, needs a new skin after 6 years. frame is doug fir and salvaged oak ribs (steam bent)


skin-on-frame kayak I built for my wife, red cedar with alaskan yellow cedar ribs, total cost was under $100. still have this one in great shape after about 8 years (stored out of the weather).

 

These are very nice boats, Petros. First one made me smile. Really good job.

Why do you consider my rig complex? I single-handed my catamaran with both sails, not very comfortable, but it works. Actually, it worked very well, I tried sailing my catamaran only with mainsail - the difference is huge.
Maybe because adding jib requires stays, and these require shrouds? Because I don't hold anything against shrouds. I believe they would help to reduce stress when flying one or two hulls - because without them, all the heel force would go to the mast step and deck, weight would be held only by cross-beams. With shrouds, heel force is directly transfered from mast to hull via shroud. Am I not right? That system wouldn't add much to cost. I can use my old ropes, or even better, buy metal cords - they don't stretch, so I don't have to tension them too much, bending the cross-beams.
Jib adds much more power, ability to balance lateral resistance and center of effort.
Could you please elaborate why you advise to stick with cat rig?

As for your previous post, I agree with what you say about stopping to look at commercial boats, and utilizing traditional techniques, it's just that I would very, very much like to make it folding. I understand your arguments, in my situation, I will have many problems with non-folding: I'll have not to exceed certain length because of top-of-car transportation, transporting on roof adds to fuel consumption, no place to store (absolutely), if storing outside - problems with weather and steal risk, and so on. I know that non-foldings worked out well for you, but I'll just have more problems than I can manage... So while I'll try to make this as simple and cheap as possible, this one thing is something I can't sacrifice.

One more thing - I was analyzing some trimaran designs on DelftShip, and I was wondering, is it possible to make this kind of shape with skin on frame construction (the inward curve of the main hull)?



Because for example, this 21ft hull has Cp of 0.5659 and Cb of 0.1041... I mean, that's one fine hull, right?

 

http://www.solwaydory.co.uk/products/sailing-canoes/osprey-outrigger-sailing-canoe/

http://www.solwaydory.co.uk/videos/17

I have one of these trimarans, and I am delighted with its performance. I'm happy to talk about it at length, or answer any questions if its helpful to you.

Adrian