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Thread: Canoe to Sailing Trimaran conversion

  1. #1
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    Default Canoe to Sailing Trimaran conversion

    Hello, I am new to this forum, was pointed to a thread here that was very interesting to me as it paralleled closely what I have been doing and so I registered to comment and perhaps gain advise from those wiser than me. Problem is I have a thick skull and it takes lots of beating to get some common sense inside sometimes :/

    The thread that brought me here is by Lee.007
    http://forum.woodenboat.com/showthre...trimaran-setup

    I am not sure what the politics are on this forum, every forum has different rules and policies in regards to linking and mentioning potential competition so I will try not to link or appear to be advertising (which I am not) though I am quite happy with the designer of the boats I have built so far.

    A few years ago my son and I built a Hiawatha Canoe 14' and followed that up with a 17ft Fast Skiff we put a new 60hp Mercury on, we have enjoyed both of those a lot and are currently building an all aluminum airplane from scratch. My goal has been to raise him with knowledge and skills not necessarily to be able to build boats or airplanes, but to know that no matter what he dreams, with hard work and persistence he can achieve them. My wife and I ended up drinking our own cool-aid, and now dream of building a large catamaran to retire on. We live in a remote area in Alaska with no sailing boats and neither of us have sailed, so we both wanted to be realistic in a couple of ways, one in that we should learn some basics, and two that we should experience some time on a live aboard yacht before starting a project that large to make sure it is actually something we want. This project addresses the first of those, a simple (relatively?) way to learn some of the basics of sailing and have fun at the same time.

    I searched around lots of different drop in outrigger plans and kits and never found exactly what I was looking for. Perhaps one or more of those available are easily modified, but it is hard to know without buying them first... So I kept reading and researching and decided to just do it myself.

    I have been trying to teach myself Solidworks as I got a free student edition access with my EAA membership. I spent a while this winter playing with different sizes and shapes until I came up with something I was happy with. (winter is a good time for this as my 'workshop' is an unheated Shelterlogic tent and I can not do any epoxy work during the winter) The hulls are 12' long so as to maximize volume from one and a half sheets of plywood. I had designed them for just over 400lbs of buoyancy each, but messed up with a beginner mistake in Solidworks and so it is less than that in reality. (I haven't calculated but probably ~350lbs each)
    I bought a 420 Mainsail which is 80ft2 and am building the mast and boom for it as well as able to 'upgrade' to a 470 sail if needed later down the road. I built a hollow teardrop shaped mast and boom from 1x4 lumber glassed inside and out with pex pipe for the track. I scarfed the 12ft 1x4s for the mast, so without trimming it is a little over 23ft long, the boom is 12ft but I will trim it down to length.
    So far I have assembled both hulls and glassed the inside seams with 6oz tape, glassed in the two bulkheads that will go under the beams and filled all the outside seams with thickened epoxy for shaping. That is as far as I got before we headed out for a long Mothersday weekend, but I am hopping to get back to it tonight.

    My thought for the beams was simple straight box beams made from the same 12ft 1x4s as I made the mast from glassed on the outside with 12oz tape. Simple and strong... my only concern is that they may be too close to the water, I know a lot of kayak/canoe conversions have pretty sweeping curved beams which not only pretty also serve to get them higher above the waves..... however, I wont want the canoe swamped, so as long as the waves arent swamping the canoe they shouldn't be splashing off the beams either?

    My biggest puzzle still is leeboard placement and size and to a lesser extent rudder sizing. I had originally planned to build daggerboards and build cases 2-3 times too long with spacers and a subcase for the daggerboard to play around with balance, but it seemed overly complicated so I was talked into doing a leeboard. I think I will mount it on the forward beam angled back so that balance can easily be adjusted by how deep it is submerged, further down will be further forward, and further up will be further back.... Just need to build a sturdy hinge and actuation system for it. (and the rudders)

    Anyways, enough of an introduction, I welcome advice... maybe someone can beat some sense into me











    https://youtu.be/cHo8aSRDKH4

  2. #2
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    Default Re: Canoe to Sailing Trimaran conversion













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  5. #5
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    Default Re: Canoe to Sailing Trimaran conversion

    and just for fun to say hi to the forum, a couple of plane building pics,












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    Default Re: Canoe to Sailing Trimaran conversion

    Ha! Your plane building photos reminds me of my Air Force days. I was a "spark chaser" (aircraft electrical systems specialist) but I cross trained into sheet metal and hydraulics and was put in charge of a battle damage repair crew.

    I got pretty good at the sheet metal work!

    I quite like your outrigger design. I might be building something similar for a canoe of mine this summer. Still haven't designed mine....

    I live off grid in the Washington mountains. Not quite as remote as you of course, but I do snow shoe down the mountain to get to where I leave my jeep for the winter.

    I heat my "boatshop" (read as old barn.) with a wood stove, and can usually figure out how to make it warm enough for Titebond III glue (45 degrees) and once used kerosene lanterns to help kick off epoxy in the bottom of a hull -

    SAM_8477.jpg

    Otherwise it' just huddle around the wood stove -

    SAM_8333.jpg

    And my kerosene burning samovar provides hot drinks in the shop!
    Pretty cozy really, I seldom have to wear a winter coat in there.
    What with global warming or whatever, it never seems to get below zero here anymore.

    SAM_8313.jpg

    I think 80 sq. ft. is everything you'll need and more for that little boat! Better have a way to reef it!
    By all means keep up the posts and let us know how the canoe is coming along!

  7. #7
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    Default Re: Canoe to Sailing Trimaran conversion

    Oh, I'd recommend putting the leeboard in line with, or just behind, the center of effort of the sail.


    These two links should help -


    http://www.jimsboats.com/15oct11.htm

    http://www.jimsboats.com/webarchives/2001/1sep01.htm

  8. #8
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    Default Re: Canoe to Sailing Trimaran conversion

    Welcome aboard NarfiWillem, that looks like a great project.

  9. #9
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Etdbob View Post
    Ha! Your plane building photos reminds me of my Air Force days. I was a "spark chaser" (aircraft electrical systems specialist) but I cross trained into sheet metal and hydraulics and was put in charge of a battle damage repair crew.

    I got pretty good at the sheet metal work!

    I quite like your outrigger design. I might be building something similar for a canoe of mine this summer. Still haven't designed mine....

    I live off grid in the Washington mountains. Not quite as remote as you of course, but I do snow shoe down the mountain to get to where I leave my jeep for the winter.

    I heat my "boatshop" (read as old barn.) with a wood stove, and can usually figure out how to make it warm enough for Titebond III glue (45 degrees) and once used kerosene lanterns to help kick off epoxy in the bottom of a hull -

    I think 80 sq. ft. is everything you'll need and more for that little boat! Better have a way to reef it!
    By all means keep up the posts and let us know how the canoe is coming along!
    Electrical systems are my weak point :/ but I have spent my adult life working sheet metal on small aircraft and really enjoy it, it is a lot of fun to entice my son into parts of building. I just have to be careful to make it fun in small spurts and not a forced 'chore'... so far I think it is working well but when in the moment it is always hard to know the right balance.

    Looks like you have had some fun building experiences of your own
    We live very remote, but not off grid like you, our village has power but we are off the road system, only way in or out is by small aircraft. The kids here drive 4wheelers and snowmachines to school in the winter.

  10. #10
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Etdbob View Post
    Oh, I'd recommend putting the leeboard in line with, or just behind, the center of effort of the sail.


    These two links should help -


    http://www.jimsboats.com/15oct11.htm

    http://www.jimsboats.com/webarchives/2001/1sep01.htm
    Those are great links I hadn't seen before, should provide me with a few rabbit holes as well, thanks!
    From what I understand and from his paper, I think the board should be slightly forward of the center of effort on the sail? That way without rudder input the wind pushes the transom while the board pushes the bow into the wind where it should stall... or do I have it backwards somehow?

    From what I have read, on small boats like this (tiny even in terms of sailboats) even a couple of inches shift in the board can make huge differences. This is why I think a long adjustable board will work well for me and why I had gone away from my idea of daggerboards in the hulls even though I think they are much more aesthetically pleasing. With a leeboard or 'offset centerboard' I can shift its effort significantly, and even if I could calculate perfectly for this sail, that will allow me to make changes to the sails later if I ever wanted, a larger or smaller or reefed or an added jib, etc... will all change the balance, and the adjustable swinging board will be able to balance any of that. (I hope)

    Speaking of reefing..... how is that done on a sail with a bolt rope in a track?

  11. #11
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by johngsandusky View Post
    Welcome aboard NarfiWillem, that looks like a great project.
    Thanks!
    It will end in fun or disaster, but the journey will be fun either way (and my goal is that if it is disaster it is a manageable disaster :P )


    I sanded and shaped the exterior of one hull last night, took about an hour but then my wife called me in, friends had invited us to dinner, so progress was halted... hopefully more tonight, was wanting to glass tapes the outside seams yesterday or today, but its overcast and rainy today, not sure if the greenhouse effect on the tent will be enough for me to do epoxy this afternoon or not. It isnt freezing at night anymore, but its getting close, so sunny afternoons heating the tent up into the 80s are my windows for working epoxy as that lets it gel and harden up good before night and then cure over the next couple days in the sunny afternoons when the tent heats up.

  12. #12
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    Default Re: Canoe to Sailing Trimaran conversion

    My initial gut feeling upon seeing the drawing is that the mast is too far aft, and most likely should be placed more like this.

    tri.jpg

    Depending on just how far up the mast the sail will actually be, you might even be able to go boomless and sheet the sail to the aft tip of the main hull, though having a boom and sheeting to the aft crossbar area would probably be more practical.

    Reefing is done by having a spot slightly above the sail's tack corner where the track is opened up (cut away). This allows the sail to be fed-in for raising and partially pulled down and out of the track and then bundled or rolled for reefing.

    When you start looking at multihulls, some of the standard conventions for things like the hull's center of lateral plane can get pretty wonky. Different hull and ama shapes and combinations can have drastically different sideslipping characteristics. It's probably not wise to assume that your just going to drop a daggerboard, centerboard or leeboard in some pre-determined position and everything will be just fine. Combine that with the fact that it can easily take a whole sailing season to learn the tacking timing for consistent tacks that don't stall out half way through. So keep as much adjustability as possible in your board position until you have really begun to get used to the boat and what it needs in terms of combating excessive weather helm, how much speed you need to carry into a tack, how sharply or quickly you should turn the rudder when tacking, etc.

    Most monohulls will round up to weather as they heel due to the hull's shape. More heeling equals more rounding up. Moving the CE slightly ahead of the CLP helps to counteract this to some extent, so that you aren't having to drag the rudder sideways through the water to correct for it. A trimaran doesn't heel much. It won't round up much and it can't lean over much to spill wind, so it will respond differently and again, keeping your fine tuning options open as long as possible as you get used to the boat is a very good idea.

  13. #13
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Todd Bradshaw View Post
    My initial gut feeling upon seeing the drawing is that the mast is too far aft, and most likely should be placed more like this.
    That is good to hear... I have since drawing that rough outline changed my idea a little and have already been planning on the mast being closer to where you drew it.
    Point taken on keeping as much adjustment as possible for the board, that has been beaten into me a few times now and I have embraced it.
    Thanks for your input, I have seen your name quoted with respect before on these topics.

  14. #14
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    Default Re: Canoe to Sailing Trimaran conversion

    Yeah, sometimes I get lucky.

  15. #15
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    Default Re: Canoe to Sailing Trimaran conversion

    You might like to look at the Brit Open Canoe Sailing Group site
    http://www.ocsg.org.uk
    They tour in open cold water all the time and there are many tri's in their number.

    I sail an Outred Macgreggor decked canoe with a lateen rig and leeboard.

  16. #16
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by skuthorp View Post
    You might like to look at the Brit Open Canoe Sailing Group site
    http://www.ocsg.org.uk
    They tour in open cold water all the time and there are many tri's in their number.

    I sail an Outred Macgreggor decked canoe with a lateen rig and leeboard.
    Thanks, I'll dig into their site

    Sanded and shaped the outer seams last night and this afternoon.
    I could have spent a little more time on the bow curve, but it's purely asthetic and I'm trying to be quick instead of pretty as much as I can force myself to.

    Then my wife helped tape all the seams. She mixed and I applied.
    First time using woven tapes,(I've always used biax tape but wanted a cleaner finish for these with less sanding) I think they went ok. I was careful at the bow and did it with a shorter strip so it would form around the curve better.

    My intent has been to follow up with a layer of 6oz cloth over the entire outside but as stiff as the hulls were with just the inside taped(I used biax inside), I'm toying with the idea of just fairing in this tape and calling it done.... Will see how it feels after it cures. The full top deck will add even more stiffness to it..... Thoughts?

    20210515_181134.jpg

    20210515_181152.jpg

    20210515_181208.jpg
    Last edited by narfiwillem; 05-17-2021 at 11:13 AM.

  17. #17
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    Default Re: Canoe to Sailing Trimaran conversion

    When I built my sailrig, I used 4 oz fiberglass inside and out. But, my wooden planks were 1/8" cedar strips. I don't remember reading above, but it looks like your plywood is 1/4 inch. My kayak is 1/4" cedar strips, glassed inside and out with 4 oz. I have dropped it from six feet up on the jeep to the ground before. No breaks, cracks, or de-laminations yet (knocking on wood).

    I would glass the outside at the least, just to help resist blunt force trauma from rocks, trailer hitches, and any other hazard lurking under the surface of the water. And don't worry too much about aesthetics, unless you want to show it off in a trade show or something. I like Nick Schade's quote, " A wooden boat will soak up as much perfection as you throw at it, and you need to learn to pick your battles." After 6 trips to the lake, mine is scratched up all over, but I don't care, it still floats!
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  18. #18
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Lee.007 View Post
    " A wooden boat will soak up as much perfection as you throw at it, and you need to learn to pick your battles."
    Hehe, I like that quote.
    I'm using 1/8" bs1088 hydrotek

    Cut and dry fit the cleats for attaching the decks. I think should provide good gluing surface area. Hopefully get them glued in tomorow with thickened epoxy.

    Just for fun laid the mast ends on benches and sat on the middle, it held me fine though I was nervous and listening for any creaking or cracking. Fully dressed with my mud boots on I'm just over 200lbs. Roughly 23ft between the benches.

    20210516_172126.jpg

    20210516_172148.jpg

  19. #19
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Todd Bradshaw View Post
    My initial gut feeling upon seeing the drawing is that the mast is too far aft, and most likely should be placed more like this.

    Depending on just how far up the mast the sail will actually be, you might even be able to go boomless and sheet the sail to the aft tip of the main hull, though having a boom and sheeting to the aft crossbar area would probably be more practical.
    Revisiting this with a little more detail on my thought process.....
    The canoe is symmetrical at 14ft, the seats are 6ft from outside to outside and make a good visual and/or physical marker for placing the beams which means the inside faces of the beams will be 6ft apart and 4ft each from the tips of the canoe.
    My current plan is to mount the mast to a reinforced section on top of the forward beam to simplify installing and removing the canoe.
    A forestay to the front of the canoe and shrouds to the ends of the rear beam. Will that allow enough travel of the boom? or do I need to build some reinforcements for attaching a little further forward on the outriggers?
    A 420 mast has spreaders, but as stiff as the one I built seems, I don't think there is any need for them.... Should I attach the forestay and shrouds at the top of the mast or at some arbitrary point lower down?
    The published foot of a 420 sail is 7.87ft so I think you are right it should be practical with the boom and sheeting to the rear beam.
    No final plans yet for the height of the boom, but thinking roughly 6" higher than the top of my head if I were to sit up on the side of the canoe. Perhaps a little high, but will prevent me from wacking myself in the head with a big stick?


    Quote Originally Posted by Todd Bradshaw View Post
    Reefing is done by having a spot slightly above the sail's tack corner where the track is opened up (cut away). This allows the sail to be fed-in for raising and partially pulled down and out of the track and then bundled or rolled for reefing.
    I am not to this point yet, but usually how long is the cutout? Ive been aware I will need a cutout to insert the sail, but not sure how much that should be.... 1-2ft from above the boom?
    Bundling or rolling the unused section while reefed sounds awkward, but perhaps thats just because I have no experience.... will be interesting to play with.


    Quote Originally Posted by Todd Bradshaw View Post
    When you start looking at multihulls, some of the standard conventions for things like the hull's center of lateral plane can get pretty wonky. Different hull and ama shapes and combinations can have drastically different sideslipping characteristics. It's probably not wise to assume that your just going to drop a daggerboard, centerboard or leeboard in some pre-determined position and everything will be just fine. Combine that with the fact that it can easily take a whole sailing season to learn the tacking timing for consistent tacks that don't stall out half way through. So keep as much adjustability as possible in your board position until you have really begun to get used to the boat and what it needs in terms of combating excessive weather helm, how much speed you need to carry into a tack, how sharply or quickly you should turn the rudder when tacking, etc.

    Most monohulls will round up to weather as they heel due to the hull's shape. More heeling equals more rounding up. Moving the CE slightly ahead of the CLP helps to counteract this to some extent, so that you aren't having to drag the rudder sideways through the water to correct for it. A trimaran doesn't heel much. It won't round up much and it can't lean over much to spill wind, so it will respond differently and again, keeping your fine tuning options open as long as possible as you get used to the boat is a very good idea.
    I have a pretty sharp 'V' on the bottom of my outriggers, I did that in hopes of some lateral stability even without a board lowered, but their balance will be forward so will be interesting how they affect it all as well.

  20. #20
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    Default Re: Canoe to Sailing Trimaran conversion

    shrouds to the ends of the rear beam. Will that allow enough travel of the boom?
    I'd like to see more ability to ease out the boom than that. You wouldn't really have very much ability to de-power if needed with the shrouds there. Situations that far aft usually are running backstays and the boat's shrouds are farther forward, allowing more ability to ease the boom out. Sheeting to the aft beam also brings in the possibility of mounting a traveler of some sort on the beam so that the mainsheet tackle can move side to side. The advantage of this is upper sail twist control and adjustment. Keeping the sheet tight and easing the traveler can allow you to keep the sail working all the way up for better performance in lighter air. Easing the sheet, but not the traveler as much lets the sail's top twist to leeward, spilling excess wind when it's blowing hard out there and you want to de-power a bit.

    I'm not a fan of high booms, especially if the excuse for having one is the old getting hit in the head thing. Learning to deal with the boom is just part of learning to sail. I'd rather keep my C.E. down a bit lower, along with the heeling force on my boat. On small boats it's easy enough to learn the tacking/jibing timing and at the proper point in any tack or jibe, simply reach up, grab the boom and calmly pass it over your head. The alternative, hunkering down blindly and waiting for the wind to slam it over at some point, isn't very attractive.

    Typical small boat mast cutouts tend to be in the 6"-10" range. With the combination of the tack corner secured to some fitting, jaws, gooseneck, etc. and the pull of the halyard from above, that little area where the boltrope isn't in a track is not going anywhere. Some, like this one may be cut all the way down to the gooseneck. Others sometimes start a couple of inches above the gooseneck and run upward 6"-10" above their starting point.

    And yes, with the possible exception of roller reefing, where the whole boom spins and the mainsheet is attached end-boom with a topping lift to allow it, a lot of reefing is not particularly neat looking. You can sometimes roll the excess, or flake it back and forth on top of the boom (required if the sail is attached to the boom along the foot), but in many cases, it tends to look more wadded up than anything else.

    #39-tack-corner.jpg

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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Todd Bradshaw View Post
    I'd like to see more ability to ease out the boom than that. You wouldn't really have very much ability to de-power if needed with the shrouds there. Situations that far aft usually are running backstays and the boat's shrouds are farther forward, allowing more ability to ease the boom out.
    I think it will be pretty tight between the boom and backstay if I did that... at this stage of the game it will still be pretty easy for me to build reinforcement into the hulls for the shrouds. Would 2ft aft of the mast be ok 6ft out on each side? Perhaps mounted 2/3rds of the way up the mast for the shrouds and forestay?

    Quote Originally Posted by Todd Bradshaw View Post
    Sheeting to the aft beam also brings in the possibility of mounting a traveler of some sort on the beam so that the mainsheet tackle can move side to side. The advantage of this is upper sail twist control and adjustment. Keeping the sheet tight and easing the traveler can allow you to keep the sail working all the way up for better performance in lighter air. Easing the sheet, but not the traveler as much lets the sail's top twist to leeward, spilling excess wind when it's blowing hard out there and you want to de-power a bit.
    Forgive my ignorance, and probably wrong use of terminology as well.... What are the advantages/disadvantages between using a downhaul and a traveler? I thought they served a similar purpose, but perhaps am wrong? The goal being to set the shape of the sail by raising or lowering the end of the boom while still allowing adjustment side to side that wont affect the tightness on the sail?

    Quote Originally Posted by Todd Bradshaw View Post
    I'm not a fan of high booms, especially if the excuse for having one is the old getting hit in the head thing. Learning to deal with the boom is just part of learning to sail. I'd rather keep my C.E. down a bit lower, along with the heeling force on my boat. On small boats it's easy enough to learn the tacking/jibing timing and at the proper point in any tack or jibe, simply reach up, grab the boom and calmly pass it over your head. The alternative, hunkering down blindly and waiting for the wind to slam it over at some point, isn't very attractive.
    Noted. I am sure a lot of my thought process is from lack of experience, and just by being able to 'do it', many things will become more obvious. Is there a 'standard' height above seat level you would recommend? I would guess bottom of boom level with bottom of chin would be a comfortable enough level to grab and ease over without having to bend too much?

    Quote Originally Posted by Todd Bradshaw View Post
    Typical small boat mast cutouts tend to be in the 6"-10" range. With the combination of the tack corner secured to some fitting, jaws, gooseneck, etc. and the pull of the halyard from above, that little area where the boltrope isn't in a track is not going anywhere. Some, like this one may be cut all the way down to the gooseneck. Others sometimes start a couple of inches above the gooseneck and run upward 6"-10" above their starting point.
    Ok great that seems easy and logical.

    Thanks again, appreciate your insight.

  22. #22
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    Default Re: Canoe to Sailing Trimaran conversion

    Glued in all the cleats with epoxy thickened with wood flour. Installed a couple of spreaders in the bow compartments to widen the top out a bit and add a little more bouyancy up front if they get submerged.

    Took a look at my last eight 12ft 1x4s I will use for the box beams. Not pretty, and 2 of them have small split sections.... I will try to balance them, best 4 pieces for the tops and bottoms and the worst for the webs with one each of the worst on each beam web..... I think the big box beams are overkill so hoping it will be ok with the inferior wood I am using.


    20210517_193648.jpg

    20210517_193617.jpg

    20210517_193627.jpg

  23. #23
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    Default Re: Canoe to Sailing Trimaran conversion

    Would 2ft aft of the mast be ok 6ft out on each side? Perhaps mounted 2/3rds of the way up the mast for the shrouds and forestay?
    That seems more reasonable to me. Make the anchors for the shrouds sturdy. With a trimaran you always have the "flagpole principle" to deal with. Since the three hulls greatly reduce the boat's ability to heel over and spill wind in a blow, the mast is more like a flag pole which is either strong enough to stand up to the gusts, or it is soon broken or torn loose. I don't know whether real boat designers have specific criteria for what altitude on the mast is the best spot to attach the shrouds and forestay, but 2/3 to 3/4 of the mast height sounds good.

    What are the advantages/disadvantages between using a downhaul and a traveler?
    That should probably be a boom vang, not a downhaul. A vang is mounted to the boom a bit aft of the mast and runs down and forward diagonally to the mast base or something in that area. It is there for twist control, pulling downward on the boom to reduce upper sail twist to leeward. On a multihull, the vang and traveler can both do the same job, but the traveler is much more powerful, being a more direct downward pull, nearer to the aft end of the boom. Most catamarans and trimarans that have a wide traveler track aft don't have much use for a vang. A downhaul is generally set to pull straight down on the luff edge of the sail. On something like a lugsail, it keeps the luff edge tight and firm. On a sail with a boltrope in a groove, tightening the downhaul pulls the sail tighter along the luff and to some extent can pull the sail's maximum draft forward a bit or temporarily reduce the draft. With modern, non-stretchy sailcloth though, this ability to distort the sail's shape from what it was designed and cut to be in the first place may be quite limited. In a lot of cases the downhaul's job is simply to keep the boom from rising on sails which don't have a fixed gooseneck position (sails with boom jaws or goosenecks which can slide in the sail track for example).

    That's another one for the cutout consideration. Some sails have booms with sliding goosenecks, made to fit into the boltrope track on the mast. In that case, the cutout will be several inches above the spot where the boom will be when in use. In the area where the boom will ride, the mast groove will not be cut away. The sail's boltrope is fed into the cutout and goes up the mast when raised. The gooseneck is then fed into the cutout and slides downward below the cutout. It is secured there by a simple downhaul which keeps it from rising upward when sailing. A lot of common small boats, like Hobie Cats use such a system.

    Here is a Hobie gooseneck.

    hobie-gooseneck.jpg

    The sail's tack grommet is pinned to the upper shackle. The downhaul is tied to the ring on the bottom of the gooseneck and that is cleated off to a simple cleat below the boom on the mast. The slug part is fed into the mast slot and the downhaul pulls down and is cleated to prevent boom-rise. The boom's end cap can rotate as needed on the big pin and the universal joint allows the boom to tilt upward or downward a bit. It's a pretty clever assembly.

    For most recreational small boats I'll usually run the boom somewhere between shoulder and nose level, but it's all a matter of personal choice. In a multihull the issue is usually not one of a high boom increasing heel angle as much as increasing strain on the mast and rig (flagpole principle) and possibly being more prone to burying the leeward ama.

  24. #24
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    Default Re: Canoe to Sailing Trimaran conversion

    Quote Originally Posted by Todd Bradshaw View Post
    That seems more reasonable to me. Make the anchors for the shrouds sturdy. With a trimaran you always have the "flagpole principle" to deal with. Since the three hulls greatly reduce the boat's ability to heel over and spill wind in a blow, the mast is more like a flag pole which is either strong enough to stand up to the gusts, or it is soon broken or torn loose. I don't know whether real boat designers have specific criteria for what altitude on the mast is the best spot to attach the shrouds and forestay, but 2/3 to 3/4 of the mast height sounds good.
    ok, great, Thanks!


    Quote Originally Posted by Todd Bradshaw View Post
    That should probably be a boom vang, not a downhaul. A vang is mounted to the boom a bit aft of the mast and runs down and forward diagonally to the mast base or something in that area. It is there for twist control, pulling downward on the boom to reduce upper sail twist to leeward. On a multihull, the vang and traveler can both do the same job, but the traveler is much more powerful, being a more direct downward pull, nearer to the aft end of the boom. Most catamarans and trimarans that have a wide traveler track aft don't have much use for a vang. A downhaul is generally set to pull straight down on the luff edge of the sail. On something like a lugsail, it keeps the luff edge tight and firm. On a sail with a boltrope in a groove, tightening the downhaul pulls the sail tighter along the luff and to some extent can pull the sail's maximum draft forward a bit or temporarily reduce the draft. With modern, non-stretchy sailcloth though, this ability to distort the sail's shape from what it was designed and cut to be in the first place may be quite limited. In a lot of cases the downhaul's job is simply to keep the boom from rising on sails which don't have a fixed gooseneck position (sails with boom jaws or goosenecks which can slide in the sail track for example).
    Yes, thank you, I knew I would get some terminology wrong. Looks like I will be researching simple traveler systems I can use along my rear beam


    Quote Originally Posted by Todd Bradshaw View Post
    That's another one for the cutout consideration. Some sails have booms with sliding goosenecks, made to fit into the boltrope track on the mast. In that case, the cutout will be several inches above the spot where the boom will be when in use. In the area where the boom will ride, the mast groove will not be cut away. The sail's boltrope is fed into the cutout and goes up the mast when raised. The gooseneck is then fed into the cutout and slides downward below the cutout. It is secured there by a simple downhaul which keeps it from rising upward when sailing. A lot of common small boats, like Hobie Cats use such a system.

    Here is a Hobie gooseneck.

    ....

    For most recreational small boats I'll usually run the boom somewhere between shoulder and nose level, but it's all a matter of personal choice. In a multihull the issue is usually not one of a high boom increasing heel angle as much as increasing strain on the mast and rig (flagpole principle) and possibly being more prone to burying the leeward ama.
    This gives me lots to think about. I had thought about a gooseneck that slid in the track but was concerned about the strength of my track and not sure what forces the boom would put on it.
    Here is a picture of my sample mast profile with track I made to test the idea before I built it. The track is pex pipe and it has 2 layers of 12 oz glass around it, but split (obviously) at the back. The way I layed up the mast halves with a layer of 12oz inside and a layer outside when I was done putting them together put both layers around the pex.





    I guess the outhaul will ensure that all pressure from the mast is towards it and not pulling away, so perhaps there is no issue to worry about at all.

    I have some 1/8" 6061-T6 aluminum from the airplane I am building with my son, and am thinking I will make 2" straps wrapped around the mast and screwed into the wood/fiberglass with tabs sticking down for the forestay/shrouds and another for mounting the gooseneck as well as the straps for mounting the the shrouds to the hulls(backed inside with 3/4" wooden doubler plates). I will prime/paint them and we live in freshwater so I am not very worried about corrosion, just the strength needed for these bits of hardware.

  25. #25
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    Default Re: Canoe to Sailing Trimaran conversion

    My gut feeling is that your boltrope track will be plenty strong enough. Although modern sailcloth isn't particularly stretchable, a sliding gooseneck with a downhaul, or a Cunningham (a line passing through an eye in the sail slightly above the tack corner and running down to some sort of cleat, used mostly in situations with fixed, non-movable goosenecks) can still help flatten the sail when desired. Adding extra tension to the luff edge of a sail attached to a bolt rope groove tends to pull the sail's luff round into a long vertical wrinkle just behind the mast. Luff round is one of the major contributors to sail draft. If it's blowing like crazy out there, or if we are trying to point up pretty high when sailing to weather, then a flatter sail is just what the doctor ordered. Usually if we're sailing around with big wrinkles in the sail we may be doing something wrong. In this case, however, the potential drawback of disturbing the airflow over the mast and sail a bit with a wrinkle is less important than flattening the sail for better performance.

    This is my old Mini 12 at our place up north - old ancient, steam-powered Sony HandiCam video, most of which can be ignored. At just about 1:30 though, there is a shot glancing up the sail while sailing upwind. The Cunningham is cleated tightly (it had a fixed gooseneck) and as you look up the luff you can see the fabric gathered behind the mast into the vertical wrinkle. The mast is off to the left side and you can see the spreader sticking out horizontally. The luff fabric is a very stiff Dacron and the back part of the sail is all Kevlar. The dark stripes are draft stripes - visual indicators of what horizontal chord shape the sail has. Notice that instead of a nice airfoil shape, they indicate the big wrinkle just behind the mast and a lot of flat-ish sail aft of the wrinkle. In normal situations there isn't much reason to overdo the tension when using a sliding gooseneck with a downhaul or a Cunningham. For the most part, you want a firm luff with enough tension to be smooth and set nicely along with decent draft in the sail. Cranking up the tension to sometimes flatten the sail as the conditions dictate is just one more tool in your skipper's toolbox.

    https://www.dropbox.com/s/kov39qvik3...video.mp4?dl=0

    wrinkle.jpg

  26. #26
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    Default Re: Canoe to Sailing Trimaran conversion

    Well you convinced me. I will work on getting or building a sliding gooseneck. Thanks again for taking the time, I am learning a lot.

  27. #27
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    Default Re: Canoe to Sailing Trimaran conversion

    Didn't have a lot of time tonight, but was able to cut and glue in the shroud attach bracket mounting reinforcements. 1 layer of 1/8th pretty large to spread the load and a slightly smaller layer of 1/2" the sticks are just wedged in to hold the bottom portion in place while the glue cures.

    Guess the hulls are port and starboard now..... Until this point they were symmetrical.

    20210518_165623.jpg

  28. #28
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    Default Re: Canoe to Sailing Trimaran conversion

    Oops was just informed on another forum that the proper term is "chain plate backers"

    I will learn..... Eventually

  29. #29
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    Default Re: Canoe to Sailing Trimaran conversion

    Sanded all the glue lumps off from installing the cleats for bonding the top deck down to a somewhat uniform mating surface. Cut the top decks out slightly over sized and dry fit them. Removed them and laid them out upside down. Coated the undersides with epoxy, coated all remaining bare wood inside the hulls with epoxy, the cleats and chain plate mounting reinforcements. Layed out thickened epoxy on all the top mating surfaces and set the decks into place and weighted them down. My wife helped as usual with mixing and quality control.

    My goal with this project is to get it done quickly and effeciently with minimal effort into looks. It is an experiment with something I don't know what I'm doing, I should keep my expectations and effort in cosmetics reasonable.

    I typically struggle with paralysis by analysis as well as some missguided notion of perfectionism. I am pretty happy to announce these decks went on with lots of ugly inside and I didn't even pause... Well maybe a few minutes of regret over the epoxy runs and zero fairing compound and no paint.... But not for long, and for now at least it is sealed inside where no one can ever see it. Though I suppose if this somehow turns into an amazing craft and gets lots of use on the lake I may open up the center compartments with a hatch of some sort to store camping gear in...... Don't need to worry about that now though


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  30. #30
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    Default Re: Canoe to Sailing Trimaran conversion

    First cross beam glued together. It is made from 4x 1x4s 12 ft long.

    I epoxy coated all the inside faces and glued in little spacers every 24 inches to hold the sides apart(building it on its side so top and bottom in the pictures)

    Layed it out on and clamped to 2x 2.5" square steel tubes so it is really straight as it cures. Will see how that translates once the clamps are removed

    My wife helped again, would have been really awkward balancing and holding all the slimey epoxy coated peices together by myself trying to get the clamps started.


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  31. #31
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    Default Re: Canoe to Sailing Trimaran conversion

    Glued together the second beam. Nothing exciting there exact same process as the first.

    Sanded down the mast and struggled with the idea of not fairing it at all, but just couldn't bring myself to do it, so applied one coat of filler to fill the weave, applied and scraped with a Bondo squeegee as thin as I could get it.

    Rained all night and cold so as thin as it was applied it is still wet this morning. I hope it cures ok over a couple of days and the cold/humidity don't mess it up for me.

    The glue and epoxy coating on the beam was thick enough I think it will do ok, probably creates a little more chemical heat that way.... I'm not sure but I do know that when I do super thin coats of filler scraped off with the squeegee they always take longer to cure.


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  32. #32
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    Default Re: Canoe to Sailing Trimaran conversion

    Routed/sanded/shaped/radiused back the top decks I had installed oversized and then taped them down.

    My math was off on amount of 6oz woven tape I ordered for the outside seams so 2nd hull got biax tape on the deck seams.

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  33. #33
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    Default Re: Canoe to Sailing Trimaran conversion

    Was perfect conditions in the tent for working epoxy yesterday. Got up over 90 in there.
    So instead of working on the outriggers we dug out the fs17 and went out on the lake for the first time this year.

    Stopped at a creek and roasted sausages and s'mores while Landon and Brutus explored and got wet.
    Landon was fine but with his pajamas and a huge beach towel wrapped around him Brutus still shivered the whole ride home

    I did sneak out to the tent in the evening and filled some spots on the cross beams. Pretty much just cosmetic but will let the glass lay down nicer and better to do before I sand all the glue down than to sand down then fill then sand again before glassing. Didn't take any pictures but it wasn't very exciting either.

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  34. #34
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    Default Re: Canoe to Sailing Trimaran conversion

    Needed to clear off the table to cut some plywood. Couldn't help myself and drug all the peices out to see how they look together. That's not the mast, just the uncut boom stock roughly 1/2 the height of the mast I built, but easier to hold in place for looks.

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  35. #35
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    Default Re: Canoe to Sailing Trimaran conversion

    I cut out and started assembly of the rudders and board.
    Epoxy coated the inside faces and then laid them in jigs with the bottoms taped together. 8nterior jig wedges were covered in packing tape so they won't stick.
    Got the idea for this method from this article,

    http://smalltrimarans.com/blog/how-t...dagger-boards/

    The rudders are 4ft by 10inch panels, the board is 8ft by 13inches. They are both oversized, I'll see if I cut them down before testing or after..... Easier to cut some off than to add more later. My goal for the board is roughly 6ft under water and whatever looks good for the rudders, I think with the two big rudders I should have plenty of authority..... But I don't really know what I'm doing so time will tell

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