a question on canoe building

Discussion in 'Boat Design' started by yoram, May 27, 2011.

  1. yoram
    Joined: Nov 2010
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    yoram Senior Member

    Hi guys
    I have built a flat bottom canoe last year ( stitches and glue ) and I want to build another one. ( here is a link to the canoe http://www.bateau2.com/free/ccanoeM.PDF ) You probably know the inner process that one goes through after building something and thinking next time I am going to do this and that in a different way, well, I am going through this process too. On the other hand, since the different “this or that” means not doing it according to the original plan, I am thinking that I need your comments on that since my knowledge is very limited.
    I want to build the same canoe and make it also a sailing, rowing and with an option to mount a trolling electric motor. Since this type of canoe is not high end, why not trying to gain all possibilities taking to an account that the performance would suffer to a degree. My aim is as simple and easy to build, as less sanding and fairing, all on the account of performance and beauty but strong and robust enough to be used by all kind of different people. (it is for special school and students will be building and sailing that). It will be standing most of its time out of the water in a shade or just out, mostly in the shade in Scandinavian (Danish) weather

    So here are some of my thoughts, please DO criticize.

    1. instead of 6 mm ply for the whole canoe, to build the bottom part from 9 mm and the side planks from 6 mm coated with epoxy and then paint it all.
    the advantages I could see in that:
    1. more robust and durable bottom
    2. no need to fiberglass the bottom and much less epoxy
    3. when building it, I could use temporary nails (it has enough “meat” for that) to connect the side planks to the bottom piece instead of stitches so I could apply the epoxy putty on the inner seams in one go.
    4. from the outer side ,I could just seal the seam (that would face down) with putty, no need for glass tape which makes less work and less material.
    5. I could keep the seams always facing bottom while the side planking do not show any. Better looks, less sanding and fairing.
    6. I was thinking even to connect the seams with 3mm wood plugs every 40 cm or so, since 9 mm thickness can take it, this will maybe enable not to put fiberglass tape on the outside. Also it does give some kind of “carpentry, boat building feel” to the whole thing.

    I understand it would be heavier since 6 mm plywood board is 11 Kg and 9 mm is 15 kg and I am going to use for the bottom part about 70% of a whole 244x122 cm ply board, it would be about 2.5-3 kg more.

    2. there will be 3 pair of ribs positioned in the (more or less) 1/4 and 3/4 and middle of the length of the canoe for seats to cover the options of one or two person on board and the 1/4 and 3/4 as supports for the arms (do they call outriggers?) that hold the amas.
    Advantages
    1. Give more strength
    2. keeps the shape better
    3. easier to build since they could act as some kind of strongback
    4. maybe enable 4 mm thick side planks?

    3. The stern would be not like the bow but more like a dingy shape stern, , 10cm at the bottom and about 20 at the top to be able to mount a small electric trolling motor or a rudder for a sailing option.
    4. The amas would be from standard pvc 10 cm diameter water pipe with the front part connected to a 45 degrees connecting pipe. (Elbow like part). The amas and the arms will be bolted to the body through the ribs and the rubrails. (I have done it already in my present canoe, even without the elbow like part in the bow, tested it in water once without sail and it seems to works well). They stay above water line. The amas and the outriggers could be easily dismantled.
    5. sail and mast, as simple as possible mast height no more the 2.5 meters from bottom of the canoe to top, sail area about 1+ square meter. The mast is connected to the bottom of the canoe, going through a special hole in the front seat as another holding point. No stays.

    \here is a sketch. It is done by “Microsoft paint” so it is very basic.
    thanks you
     

    Attached Files:

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  2. NoEyeDeer
    Joined: Jun 2010
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    NoEyeDeer Senior Member

    Why not just build it with a chine log? That way you don't need any glass at all. Simply cut out both side panels, glue and screw a bit of 30x20 to the top and bottom edges inside, wrap the panels around the frames, plane chines flat across, glue and screw the bottom on. Simple, clean and strong.
     
  3. messabout
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    messabout Senior Member

    You do not need 9mm ply for the bottom unless you intend to abuse the boat. Take no eye deers advice and use chine logs if you want simplicity and use the fillet and tape method (as shown in the instruction) if you prefer lighter weight and cleaner interior. The wooden peg idea is novel but not a practical idea. Save yourself some grief and just follow the instructions on the bateau build sheets.

    100mm pipe will not provide much righting moment but will add weight and complexity. The boat itself has a rather narrow bottom but it could be sailed without the amas.

    The free plans are very similar to a popular design called "the six hour canoe" It is a U.S. design a little longer than the bateau but has similar material layout. It uses chine logs for simplicity.
     
  4. yoram
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    yoram Senior Member

    noeyedeer, messabout, thank you for your answers.

    noeyedeer, about the chin log, is it water tight? i mean, you wrote that the point where the bottom meets the side plank and is under the chin log is not going to be glassed or puttyed just glued and screwed. in my original idea i thought first to attach the side planks to the bottom with temporary nails, then apply putty all along the seams that would serve as glue and would make it water tight and only then to put the chin logs. i also want them only where the seats are. it might sound strange that i ask that but i have no experience in that and i would really like to understand how it works.

    messabout, from what point of view the wooden peg is not a practical idea? would it not hold? or the pegs eventually will come out because of the boat movements since it is a bit too rigid? or it is just unnecessary work?

    i have tried it in my canoe. i have some experience with surfing kayaks. i have very little experience with canoes and it felt to me not very stable so i was happy to feel the safety of the amas though there was hardly a situation where they touched the water. like a child on bicycle with 2 side small wheels.:eek: it takes 8 screws for the whole device (amas+ outriggers) and takes less then 10 minutes to assamble it all so it is not a problem. if you are very experience, you could sail the canoe without it. unfortunately i am not...
     
  5. yoram
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    yoram Senior Member

    sorry, i did not quote it right. my 4th paragraph in the last message comes as an answer to this:


     
  6. messabout
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    messabout Senior Member

    Yoram; If the 100mm pipes are perhaps 3 meters long they will have a flotation potential of about 14 kilograms. You must subtract the weight of the pipes themselves, along with the weight of that part of the arms (akas) that extend outside the boat. Let us, for example, say that those weights together are 6kg. then you have 14 - 6 = 8kg of effective flotation when the amas are entirely submerged. In no case will you want them to be submerged while the boat is in motion. So you should figure to have half immersion, or less, wherupon your potential flotation is 4kg...hardly worth the bother. Another reason to avoid the outriggers is that in the case of a capsize the boat can be very difficult to right.

    If you are working wih young people with little or no experience in boats, especially boats that might be sailed, then you will be better and more safely served by a wider boat. If you widen the bottom of the boat by perhaps 8 to 10 cm, you will increase the stability by a factor that will equal or exceed the amount that would be provided by the outriggers. The wider bottom of the boat will also increase the load carrying capacity by a large amount. That will be welcome if you use an electric motor that requires a heavy battery. The battery will weigh about 20kg or more and if firmly secured at the bottom center of the boat it will add some more stability. If the battery is not firmly secured at the center of the boat it becomes a serious liability. If the boat leans over a little bit the loose battery will slide to the low side and will cause a very dangerous situation. This is a common oversight with many inexperienced boatmen. A loose battey is a deadly mistake.
     
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  7. yoram
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    yoram Senior Member

    thanks

    messabout, your comment was very good. thanks.
    making the bottom a bit wider sound very appealing to me and about the battery, you are very right.

    i was wondering about how to calculate the flotation of the amas. i got different numbers then the one you have but i did it in the way i learn in high school which was many years ago and figure that every liter of air in the pipe is 1Kg of flotation. please correct me if i do it wrong.

    square radius (in meter) x 3.14 = the area of the base of the pipe =0.05x0.05x3.14= 0.0786x3 (the length in of the pipe in meters)=0.02355 which is 23.55 Kg for one ama and about 47 Kg flotation for both.

    what about the wooden pegs? could you mention them too as why are they not going to work?
     
  8. messabout
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    messabout Senior Member

    Yoram; You are quite correct in calculating the displacement of the amas. I must have been into the rum when I did the calculations, and made an incorrect answer. Your formula pi x radius squared times length is the standard and reliable method. Sometimes it is more convenient to use the diameter rather than the radius. In that case square the diameter and multiply by 0.7854 then multiply by the length. The number 0.7854 is merely pi divided by four. Either way the answer is the same.

    The potential displacement of the ama can be multiplied by the distance from the center of bouyancy of the hull to the CB of the ama. That figure will be the righting arm of that arrangement. If the ama is one meter from the center of the canoe and the displacement is 23 kg then you will have 23 x 1 = 23 kgm of righting potential. A longer aka would provide even more righting potential but there is a practical limit to width on account of weight, structural considerations, and clumsiness which impairs turning ability.

    About the wooden pegs...... a peg of say 3mm diameter driven into the edge of a 9mm ply, leaves only 3mm of space from the peg to the ply surface. Edge fasteners in ply are generally avoided by boat builders as the holding power is thought to be compromised. If you use epoxy at the joining surfaces the pegs will probably not do any harm.
     
  9. peterchech
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    peterchech Senior Member

    Why not just build an actual outrigger canoe? Putting amas on a wide beamed hull defeats half the purpose of building a multihull, which is the ability to exceed hull speed. Building Gary Dierking's Wa'apa would be almost as simple as any other flat bottomed canoe design, especially if done in one piece, and would cost about the same too...

    Even if you don't, there is a whole thread on forum.woodenboat.com in the design section on outrigger canoes. Lots of good info there on improvising amas and other issues.
     
  10. yoram
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    yoram Senior Member

    messabout, thanks, you have a good point with the wooden pegs. 3mm is really not much to hold a peg and that is in the ideal case that i drill exactly in the middle. i will leave this idea.

    peterchech, you are right in a way but i want it to be a car top canoe and with 2 fixed outriggers and amas it become a bit too much so it is some kind of compromise. i can use the canoe without the amas just for paddling and with someone who feels a bit insecure to fall in the water, even without the sail, i add the outriggers and amas. i tried to tip it as much as i could when the amas were on and did not menage so it is safe. it all goes on the top of my car and it takes 10 minutes (even less) for one person to put it together. the sail is only to help and not as the main power.
     
  11. peterchech
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    peterchech Senior Member

    I see. An outrigger canoe can be cartopped. But certainly lashing on the amas will take more time than just throwing the canoe in the water. There is a beauty in the simplicity of a monohull canoe too IMHO.

    Mike storer has plans for a set of very simple s&g drop-in outriggers that would prob suit your purposes here perfectly. You could prob make them in a single saturday if not too concerned about finish, and they would be a drastic improvement over PVC, both functionally and aesthetically.
     
  12. yoram
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    yoram Senior Member

    it looks really nice. i will give it a thought. thanks for that.
     
  13. ancient kayaker
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    ancient kayaker aka Terry Haines

    You’re getting good advice here, so I’ll just recount my own experiences and let you draw your own conclusions, since what you propose is what I have done. Nonetheless IMHO Peterchech is right; you run a risk of ending up with a slow and unsatisfactory boat and would be better served by getting plans for a proper multihull so you’ll be happy with what your efforts give you.

    My first canoes were flat bottomed and I found they had insufficient secondary stability, downright scary to paddle despite sitting on the bottom, although they were narrower in the beam than your one. After several unsuccessful boats I went to a 5-plank design with a narrow bottom plank and bilge planks angling up and out to meet the sheer planks near the waterline, to lower the CoG. This produced a fast and very light canoe that is very easy to paddle and feels comfortable and safe even when power boats pass too close. A 5-plank canoe has a much nicer response to paddler movement and waves than a flat-bottomed canoe, although flat-bottomed boats like my flat-bottomed sailing skiff can be very stable if broad enough - but it has a waterline beam of 120 cm.

    I had an old 4.3 m fiberglass canoe and I added a single, long and skinny flat-bottomed ama and a small sail rig, which I planned to sail somewhat in the manner of a proa. It was disappointingly slow, until the day I found myself sailing at a remarkable clip in a modest breeze, and realized the ama was out of the water. That did not feel safe but I concluded it was best to mount 2 smaller amas high enough to clear the water, avoiding the excessive drag. My plans were never realized because the canoe was destroyed, but I had started to build amas that were shaped like miniature offshore power boats, the kind you see bouncing from wavetop to wavetop, reasoning that they would plane when they touched the water.

    Most of my canoes have been built mostly or entirely from 3 mm marine ply, unglassed, which has served me well. I can car-top them on my minivan without effort despite being 71 years old and a bit arthritic. I think a 6 mm or 9 mm ply boat will be a bit heavy for car-topping. A nice compromise for a canoe is 4 mm marine ply, which is often used for lightweight sailing canoes.

    The chine log method of construction works well, looks nice and saves a lot of money on expensive epoxy. I use Titebond III to glue the logs and inwales to the sheers, and also glue logs to the bottom plank, this is done with the planks flat, after which they are bent over a form. I plane the bevels on the bottom and sheer planks for gluing the bilge planks, for that joint I use epoxy. It is a very simple way to build a small boat.

    A sailing canoe needs more stiffness than a paddling version to react the heeling force of the sail; decks are a more weight-efficient way to do that than thick ply planks. This experiment demonstrates the effect of decks: twist a shoe box with and without the lid. You may think that with a multihull you can attach mast directly to an aka (outrigger) so the wind force is reacted directly to the ama, but that requires the ama to be in the water full time, and I believe you will learn as I did that it is too slow when sailed like that.

    Ama size is a delicate balance. The apparent stability from even a tiny ama is surprising: on a long trip I can take a nap in my canoe although it is small and none too stable - by placing the double paddle athwartships and hooking a leg over it. The buoyancy of the blade is enough to dramatically stiffen the boat, so it doesn’t flip if I twitch in my sleep. However, despite the fact that such a tiny bit of buoyancy gives you extra time to balance the sail force with body weight, it isn’t enough for safe sailing. Even when sailng with the amas out of the water, they are still there when needed when you get hit by a gust or a sudden reversal (knuckle) of wind near shore, and then size will count.
     
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  14. peterchech
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    peterchech Senior Member

    I have no experience with the chine log method, but would like to experiment with it to be able to build a boat on the beach from pre-formed and painted panels, kind of like laguna sink-o did at the texas 200.

    I wonder though, how waterproof and durable is the method, without fiberglass tape along the outside chine? (laguna sink-o was bailing every hour after a few days on the water)... I mean, if one were to glass the bottom panel, and also the sides, but there is no glass on the actual joint, is the chine still sort of protected from abrasion etc.?
     

  15. troy2000
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    troy2000 Senior Member

    I've built several flat-bottomed canoes without fiberglassing the chines. The first one was solid pine planks, and I didn't to anything besides nail the bottom boards to the sides. The chines never leaked a drop.

    The bottom was made of two 1x12's laid fore and aft, and I sealed the seam by cutting a bevel halfway on one board's edge, crushing the edge flat again with a hammer, and just butting it to the next board. First time it got wet, the crushed wood swelled again and made the seam completely watertight for a couple of years. It stayed that way until I took the boat to the desert in the middle of summer, whereupon the bottom boards shrank, and left a 1/8" gap from end to end that I had to stuff and caulk. But the nailed chines never did leak...

    I built a couple of others of plywood, with 1x2 chine logs. I spread the cheapest latex caulk I could find on the logs before nailing the plywood to them, and they never leaked a drop either. Well, one did eventually, after years of setting around in the weather and having kids stomp the bottom out of it... but by then the non-marine plywood was getting rotten anyway.:p

    My latest canoe has a plywood bottom nailed to solid wood sides. The transom, stem and bottom are all nailed, with PL Premium in the joints (PL Premium is a polyurethane construction adhesive, that comes in caulking tubes). I've had it out half a dozen times, including once in a pretty ferocious chop--well, ferocious for a small, flat bottomed canoe, anyway. Two of those times it stayed in the water overnight, because I was camping. And it hasn't leaked a bit; I seriously doubt it ever will.

    So judging by my experiences, I'd say you don't really have to worry about leaking chine seams. But you should seal the plywood edges well with paint or epoxy, if you aren't going to tape the chines...
     
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