Advice needed on trimaran

Discussion in 'Boat Design' started by laukejas, Aug 29, 2012.

  1. laukejas
    Joined: Feb 2012
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    laukejas Senior Member

    Hello all,

    I have recently finished and sailed my first sailboat, catamaran (made out of PVC tubes, like Rebelcat), with Tyvek sails. It didn't work out very well, but I managed to reach 60 degrees to winward, which is a lot for me. Budget was about 300$, but it could have been somewhat lower if I hadn't make some mistakes. Such as muddling with glass fiber and resin.

    Now I'm considering to make a new ship for next season, since I'm totally hooked. I think I'll get a normal Dacron sail from local sailmaker, and order a dismantable metal mast.

    I still haven't decided with number of hulls, but I think I'll go with trimaran, which has best speed characteristics and acceptable comfort. Let's assume its trimaran for now.

    So, things that I need to put it this boat:
    1. Budget up to 400$ for hull only (not including mast, sails, rigging). I have a lot of enthusiasm and time, but very little money.
    2. Lifetime at least 10 years without too expensive maintenance. My main idea: I could join 3 inflatable/dismantable canoes/kayaks with dismatable metal carcass. Canoes would last many, many years with virtually no maintenance if I don't ram it to rocks. However, they can cost at least 500$ brand new, which is my whole budget. If I buy second-hand, I'll never find two identical canoes. And 3 of them still it will be over budget. I could make them out of plywood, but in the end, I think expenses will be the same, and plywood will start to swell, rot and gain weight, and even dry, it weights too much already (see next paragraph).
    3. Ease of transportation - weight under 60kg (at least parts that are not dismantable), since I don't have trailer, only car roof, and there is 50kg limit - well, I can push it to 60, but no more). So, any parts that don't fit in trunk will have to go on roof.

    It doesn't have to be fast, (but if it's monohull, it's already fast enough). I'll sail on fresh waters, lakes, but if I'm lucky, I'll get some salt too.

    I would very much appreciate any advice on how I can make these hulls cheap, dismantable, and long-lasting.

    Thank you in advice.

    P.S. I will make a compilation of photos and put it in YouTube sometime next week of my catamaran (which, sadly, I had to demolish due to non-transportability...)
     
  2. HydroRocket
    Joined: Jul 2012
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    HydroRocket Junior Member

    chop a canoe down the middle and make two sponsons out of that (you will need to build new sides which will be flat), get a separate one for the middle.
     
  3. Petros
    Joined: Oct 2007
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    Petros Senior Member

    sounds like you have a fun little project.

    If you have access to a table saw, or can assemble one from a peice of plywood and a circular saw screwed to it, you can rip your own stringers and gunwales from salvaged lumber. with those you can make some pretty decent and light weight hulls using skin-on-frame construction for well within your budget.

    Go search the sea kayak and unimak construction method. You can cut plywood bulkhead, or laminate or steam bend ribs, and than you lash the frame together with polyester lacing cord (do not use nylon, too much stretch). You can make a fairly large center canoe like hull, with two slim ama or sponsors. Simple beams fore and aft holds it all together with either rope lashings or even heavy bungee cords. Easy to mount and dismount beams for transport. Use nylon or polyester fabric (heavy cotton works too but has to be replaced more often), with 5 to 7 coats of exterior paint for sealant. Skin can be stapled on, or can be stitched over frame with heavy needle and lacing cord.

    YOu should be able to easily build within your budget, and totally assembly should not weight more than about 40-45 kg complete. If you salvaged the lumber, and rip your own stringers, you should be able to make it the hulls for well under $200 (I have done it for about $100), the most costly part is usually the fabric, so if you can find some strong, low stretch fabric cheap, you can use it. If you use same construction method with catamaran you only have to build two hulls, might be easier but you would have less cargo capacity.

    An experienced builder friend and I built a 16 ft monohull sailboat this way using Tyvek sail, retail lumber with salvaged paint and fabric for about $70 (buying everything retail) in about 15 hours time (30 man hours). IT might take you much longer, like 100 hours, but cost should be low if you watch for free lumber in junk piles, and look for low cost sources of suitable fabric.

    Good luck.
     
  4. laukejas
    Joined: Feb 2012
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    laukejas Senior Member

    Petros, I'm interested in what you propose. But can I really make 3 hulls in 400$ total? You sure? Because marine plywood costs quite a lot, I'll need a lot for carcass, and these 6-7 coats of paint... Well, that's a lot of paint. If, for example, 1 hull water surface is 4m2, then 3 hulls is 12, 6 layers is 72m2, and with average paint, that is at least 9 liters... And 1 liter of antifouling paint (at least in Lithuania) can cost around 35$. So I don't get it, how do you make this so cheap? What kind of paint, what kind of polyester fabric? Is there any projects or plans already made from which I could take example? Since now what you say seems to me like at least 400$ for single hull, not all 3.

    I would really appreciate as much specific information as possible. (Since in my last project I almost sunk due to heavy leaking - due to inaccurate knowledge of materials)...

    As for tools, I don't have table saw, but I plan on buying a fretsaw for around 50$.
     
  5. claydog
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    claydog Junior Member

  6. laukejas
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    laukejas Senior Member

    One more thing - I looked up about skin on frame canoe construction, but all these aren't dismantable. I need something that is dismantable. I can't put 3 hulls on car's roof. And I won't have where to put it during winter...
     
  7. Petros
    Joined: Oct 2007
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    Petros Senior Member

    not sure I know what you mean by "dismantable", but if you make a center hull of say 17' length and 4 ft beam, and two amas of say 12 ft length and 1.5 beam each, they can nest inside the center hull if you build it with a few removable thwarts.

    You will kind of have to be on your own as far as detailed design since there are no plans for such a boat. You can find a tri design you like and copy the shape of the hulls, scale it to suit your size needs, and than build it skin-on-frame. Since marine plywood costs so much I would avoid it, instead select decent lumber from the local lumber yard and rip your own stringers, keel and gunwales from larger stock, use the poor quality parts for short strips, fillers or laminating, or firewood, select the cuts for the critical parts from clear parts of the lumber.

    I have built 9 or 10 skin-on-frame 15 to 17 ft long kayaks or canoues from salvaged lumber for $50 to $90 each total cost. I would find left over house paint, perfered is oil based gloss finish, but I have also used latex paint too. You only need costly antifouling paint if you keep the boat in the water all the time. Keep it out of the water than bottom stays free of growth. Most costly skin-on-frame was a folder make with aluminum frame, about $250 in materials.

    You need to look around your area and see what you can salvage, find, haul off for free. There is always lots of used lumber and wood in cities near contruction sites, you just have to look for it and ask. Fabric is more difficult to find, but it can be done too, any heavy low stretch fabric works, I like polyester because it is strong and light.

    Make the hardware, cleats, etc from wood, scrap metal. it can be done, just get creative.

    I know I can build a break-down trimiran about 18 ft long using my tools (table saw, drill, hand plane, etc) for about $250 US with a Tyvek sail, wood mast, hull empty weight will be around 70 kg, total weight will be about 100 kg. easy to put on roof of car, will take about 15-20 min to assemble and rig and set sail from beach. It would take me about 100-200 hours to build, longer if I want it to be "pretty", but can do "working boat" quality in even less time. I have built almost 20 small boats, most of them skin-on-frame, the only thing I need is the spare time to do it.
     
  8. Nnnnnnnn
    Joined: May 2012
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    Nnnnnnnn Junior Member

    If you haven't place to store boat in winter, may be it makes sense to build inflatable boat? Such boat is fully demountable and relatively easy to transport.
    Something like the boat on the picture. If you can read russian go to
    http://gik.fordak.ru/
    also there you can find ideas about using cheap materials under "Недояхтинг" topic.
     

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  9. laukejas
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    laukejas Senior Member

    By "dismantable", I mean "possible to dismantle", to break down into parts easily, and then assemble again when needed.
    For example, my parents had a skin on aluminum frame canoe, Soviet built, and it was possible to break it down to parts no longer than 3ft. Is such thing possible to be made?

    I really doubt there is possibility to salvage any lumber from my area, since it is already near-impossible to buy quality lumber, but I'll try.

    I have a question - since some parts of the frame will lie on bottom of the hulls, are they subject to rot due to water gathering in those parts? Do they need some paint or varnish to protect it?

    And one more thing, do I necessarily need table saw, or is it possible to make those stringers with fretsaw?

    And thanks for the information!

    Nnnnnnnn, how hard and costly is it to make inflatable hull? (sorry, I don't read in Russian which is in the link you provided, but thanks anyway)
     
  10. Nnnnnnnn
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    Nnnnnnnn Junior Member

    It is all matter of skill. I think first time better to try with some salvaged PVC fabric from advertising banner, for example, and simple forms.
    May be you can ask your parents or somebody else in neighborhood? If you are interested in small inflatable or folding skin-on-frame sailboats from cheap materials, you can find a lot of information in Russian from the times of USSR and later.
    BTW, you can convert aluminum frame canoe into trimaran. Something like in the picture.
    Look at the link with plans, it’s in Russian, but drawings are understandable.
    http://lodki.masteraero.ru/lodka-parus-19.php
     

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  11. Petros
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    Petros Senior Member

    I have built folding kayaks before, lots of extra work and cost. If you want to completely dissassemble the hulls than I would find two used russian folding kayaks and make beams that attach with bungee cords, and make a sailing rig. It would be cheaper and faster to build. You can also still use the kayak hulls as kayaks too.

    I have seen and paddled an all aluminium russian folding kayak, it was actually very impressive and at the time quit inexpensive. But no one is importing them because getting reliable inventory out of russia can be a problem.

    If you build a wood skin-on-frame hull I would recomment not make the hulls folding, but rather remove the beams and carry the hulls on the roof of the car full sized. They are light and easy to move, and setting up is much faster. A folding frame more than doubles the cost and triples or more the time to build, and usually doubles the weight as well. Two 16 ft kayak-like hulls would be easy to carry on the roof of even a small car, or one 17 ft center hull and two 10-12' long amas could nest inside and also be easy to carry on the roof of a small car without having to fold it up.

    Yes, you can cut stringers with a power hand saw, you make a simple jig out of plywood and blocks, feed the lumber through to cut your long stringers. Some also just slide the power saw with a guide the length of the board to make stringers, but it is easy to damage the wood this way. I think it is worth making a simple jig that is screwed to a heavy bench or saw horse, you get better stringers, better cuts and way less work than sliding the saw along the plank.

    You must store the hulls upside down if they are to stay in the weather, otherwise they collect water and the frame will rot. You can make water proof covers for the openings as well, but easier to hang them up-side down in a simple frame covered with a tarp or small roof. It is always best to fully and carefully paint the frame to preserve it. Any oil based exterior paint works, or if you want to spend the big bucks get marine paint (but personally I think it unnecessary on such a simple and inexpensive boat, you will want to build larger and better ones later anyway, so do not spend too much on paint). Some people leave the frames bare wood, I would not recommend it, the members are small and light sticks of wood, they loose their strength real fast once rots starts. The best way if possible is to build the frame, put several coats of wood preservative (the more toxic the better), and after it is dry put 5 or more coats of paint on it. You can also use clear varnish or poly finish (looks nice) but it is not as durable as exterior grade paint. The water that splashes into the boat during use is of no consequence, just allow it to dry between use. Rot only shows up after extended periods of being in moisture/damp. Sea water actually preserves wood, as would regular cleaning with bleach or other disinfectant (once a season). After 5 or more years of use, even when stored outdoors, you will want to strip the skin, inspect and repair the frame, repaint it and than put on a new skin. I have had some skins last up to 10 years or longer if stored out of the weather.
     
  12. Skyak
    Joined: Jul 2012
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    Skyak Senior Member

    I like the spirit and experience Petros provides. I have a little advice to add.

    If you use google chrome browser, it can translate the russian web site for you. They are using PVC impregnated fabric that is commonly used for awnings and truck tarps -I found the stuff they use at http://www.alibaba.com/product-free/11813903/PVC_Tarpaulin_For_Truck_Cover.html

    If you intend to fold your boat then you had better use this pvc material. If you build a skin on frame boat that does not fold, paint on fabric can work like Petros describes. Kayaks take very little force to propel, maybe you don't need a trimaran, just a smaller sail like a klupper -One sailed across the Atlantic.
     
  13. redreuben
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    redreuben redreuben

  14. laukejas
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    laukejas Senior Member

    I've been away for a while, sorry for my late reply.

    Thank you all for the information. It is very, very helpful.

    I decided to abandon folding hulls idea because of weight, cost, complexity, and other things Petros described.

    I looked up a lot of trimarans, and I'm thinking to base my design on USA 17 (of course, scaled down heavily, max up to 17 feet LOA). I like this one because of hull shape (long and narrow, wave-piercing bow), proven performance and very good looks. I really don't like these trimarans with large center hull and small outboard hulls - they don't look very reliable in weather.
    With this design, it means I won't be able to put hulls one inside other when transporting, but maybe they'll fit in a triangle (outboard hulls will lie one beside another, and center hull on top of them).
    I can't find any plans or blueprints on USA 17, but I hope I can re-make it in DelftShip from eye and some info available on wikipedia, and then fine-tune it with resistance calculators. Speaking of which, how DelftShip handles trimaran hull calculations? Are they reliable?

    For fabric, the only thing I was able to find in Lithuania after very, very long search, is this shop. It lists this pvc fabric as "moisture resistant" and " used in coating of different transports (trucks, etc.)". It costs 5.55$ per square meter, so I think price is quite acceptable. But please tell me, if this is good fabric for my ship?

    I have a few questions about painting:
    1. If I use that pvc fabric, will enamel paint stick to it? I red it is oil-based, but I don't know if it will stick to pvc laminate. Enamel is cheapest, but maybe it won't work?
    2. Is it better to paint fabric from one side, or both sides?
    3. Painting is done after stretching fabric over wooden carcass, right? Because I think if I paint it before, it may become too rigid, and it will be impossible to stretch it on carcass.

    I also have some questions about crossbeams. Thank you for the link, redreuben, there was a lot of useful information. The guy there used wood crossbeams, but such shape is very, very difficult to make, and I believe that is some quality timber. And in Lithuania, I certainly won't find any quality timber. For example, in shops, "wood type" is listed as "conifer". NEVER more specific than that. That may be spruce or birch, probably.
    So, what is the best way to make strong and light crossbeams? Maybe I need to try some metals or plastics? Is it possible? Or if I do it out of wood, how can I make shape that complex?

    One more thing. Since I'll make hulls non-foldable, I won't be able to store it indoors or under any kind of roof. If I'll leave it at the edge of the forest, turn upside down, and lift half a meter above ground (of course, cover centerboard hole), will it be ok? In Lithuania, we have winters with snow and temperature down to -20-25C, occasional rains during other seasons.
    So, will hulls survive if I store them like this?
     
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  15. Skyak
    Joined: Jul 2012
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    Skyak Senior Member

    Laukejas,

    USA 17 is a very pretty boat, but I don't think there is anything to be learned from a 90ft long and wide, 200ft tall carbon fiber racer when building a 17ft boat out of wood and canvas. It is very important that your boat fits your body and scaling something so far off will not work. There are many designs (it seems there are as many designs as boats) but I think that two you should not miss are Warren's 'Little wing' and the 'Weta' design. Little wing is a high quality kayak/trimaran. Warren has been designing trimarans for decades so the proportions and layout of the littlewing are the best I have seen for a 'sit in the center' design.

    http://www.warrenlightcraft.com/specs15sail.html
    http://www.warrenlightcraft.com/specstandemsail.html

    Weta differs conceptually in that it is a 'crawl on top' design. It doesn't look as fast as little wing but it is much faster and much more demanding to sail because the crew shifts their weight from one side to the other which allows the boat to carry a much larger taller sail. Note that bigger sail and more speed mean bigger forces and more weight. And it needs to be able to capsize and recover.

    The last design I would point out are international canoes, and skiff designs. These take more skill to sail than trimarans, but they are as fast or faster. The point is that speed with light weight comes from shifting ballast (the crew). If you do not shift weight, increasing speed will require increasing size and weight.

    http://www.intcanoe.org.uk/gallery/thumbnails.php?album=51

    About that fabric, it looks like the right material but the specifications are not all there. What you want is Polyester weave fabric, approximately 1000 denier (say 800 to 3000), with PVC impregnated or molded over. If you call and ask the right questions they should be able to confirm. If you get a sample, a 1 inch wide strip should be able to support 200lbs if it is 1000 denier. 800D should support 160lb, 3000 should support 600lb. Concerning weather capability, UV light (sun) is the biggest threat. You should avoid stressing the material while it is below freezing.

    The good news is that you don't need any paint with this material. In fact, paint might damage it so keep it away. This material is also capable of folding if you decide to go that direction. My personal belief is that a folding boat is much more useful than one that does not. I can carry a 70lb kayak in a pack on my back 20KM easily. I would have a hard time carrying a 17ft 40lb kayak 100 meters in a solid breeze. A folding kayak would fit in in the trunk of my car, someone else's car or taxi (who would let you strap your boat to their roof?) or even a bus or plane. This leads me to another consideration, the usefulness of a boat that sails very fast, but paddles very slow and must return to it's origin. Take a trimaran that sails at 20kmph and paddles at 2kmph, in one hour you can sail a days paddle away from your car, if the wind quits and you have only half a day of light left you will regret the trip and never go far. Contrast this with a boat that sails and paddles easily at 8kmph. It will have a much larger planable range. If you can pack the boat up, you can go any distance without planning, then get a ride back. This is just the advantages in use. In storage the folding design is a dream. Non-folding is a nightmare of concerns -will it get damaged? will it get stolen? do I have room inside? If inside, it is always in the way...

    I would suggest that you look around for an old Klupper folding kayak that needs a new skin. I have seen a dozen near me in Chicago at prices ranging from free to $200. Kluppers and identical copies have been produced since the 40's or 50' in eastern europe and the majority of them remain there. The frames last forever and the skins last only 20years, so there are thousands of them near you.

    If you want to build, be sure to check out Yost. He has the best, most complete skin kayak build site there is. http://www.yostwerks.com/

    About wood and construction. I think you likely have better access to quality wood than you think. I look at Lithuania, and I see trees, not desert. Your problem is figuring out what you have and finding or creating long spans without flaws. The worst it can be is lots of flaws to deal with. Skin on frame requires the smallest volume of flawless wood possible. Making a folding design is even less demanding because you use many short pieces. You could find some thin walled tube in the right diameter and use short sections to join lengths of wood trimmed to fit. Do they not have broomsticks in Lithuania?

    There are two ways to make bent wood, laminate thin strips, or steam and bend. Bent wood is pretty but you can design it out if you don't want the extra work.

    Hope this helps.

    Mark
     
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