Some design help ?

Discussion in 'Sailboats' started by Deadeye, May 12, 2009.

  1. Deadeye
    Joined: Jan 2009
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    Location: BC, Canada

    Deadeye Bender of Nails

    Howdy folks,
    I've got a bit of a project on the go and I need your help to proceed. First, a story:
    Going back a long way, but I built a Bateau 'cheap canoe' which wound up getting a kayak deck with a large cockpit and cargo hatch. Unfortunately, the thing couldn't get out of its own way - it's a bit of a beast to try and push around the lake with a paddle. It'll pack a load of gear though !
    Here's a pic.
    And here's a link to the plans, offsets, etc

    Now, my plan is to fab some outriggers and a mast but I need some help with locating the components. The boat is 14' long with a flat bottom. I've got the kickup rudder and footpedals about half done and the outriggers will most likely be formed from rigid styrofoam and glassed. I weigh about 250 and sit right in the center of the boat.

    So, my questions:
    First and foremost, I'm looking to place the mast. I've got access to the lateen rig from an old Sunfish but I don't know much about multihull layout. The other option I'm considering is making up my own (sloop) rig and making sails from poly tarps, which I can then use as patterns to get Dacron sails made up.

    Secondly, how do I figure out the fore-aft position of the outriggers with respect to the hull ? I understand that the rule of thumb for keelboats is to start with the sails' center of effort 10% of the waterline length forward of the CLR of the keel, so in this case can I substitute the center of bouyancy (CG) of the floats for the keel ?

    With all due respect to the designer, this boat as I built it doesn't really perform very well. It definitely serves the purpose of being cheap and a canoe and I laud his posting of the plans in the public domain. You just can't expect much from 2 sheets of ply, especially when you're getting 14' out of them. If this project works out, I hope to contribute the efforts in the same way. If it doesn't work, it's looking more and more like there's going to be a Viking funeral...

    Thanks for any and all input !
     
  2. alan white
    Joined: Mar 2007
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    alan white Senior Member

    If it's slow to paddle, it will be slow to sail. Maybe you know that already. It won't be heeling (and gaining any speed by becoming consequently narrower), since you want to sail upright--- and you can't sail without the outriggers.
    In stronger winds, it might just fly, however.
    You might weld the right sized pipe onto a steel base that can be screwed down temporarily. This would make a movable socket for the Sunfish mast.
    That's what I'd do rather than trusting a calculation. After all, the only help you're going to get is free help here unless you're wealthy, and can afford a designer's fee.
    I'd rather take my best shot at fore/aft location based on good advice and then move it if it doesn't work well there.
    Also, you need lateral plane in the form of a daggerboard, and I'd clamp a mock-up onto a gunwale and move it fore or aft the same way. But do the sail first without anything more than the hulls themselves as lateral resistance. One issue at a time. Then I think you'll have a good sailer. Very similar to a Sunfish but slower at lower wind speeds (and possibly faster when it pipes up).
     
  3. Deadeye
    Joined: Jan 2009
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    Deadeye Bender of Nails

    Thanks Alan, I like your approach...keep tinkering and all that.

    Part of the paddling problem is the freeboard. My 84" paddle is actually a bit short - I have to reach a bit just to bury the blade in the water. I use that paddle because it takes down and stows in the cockpit so I can fish.

    I've since built another boat for fishing so now it's time to do something with this one. I guess the trick is just to make everything adjustable. The floats ought to be easy enough and, though the deck won't support the mast step, I can certainly oval the hole to allow me to move it around. I can play with mast rake that way as well I guess.

    As far as a daggerboard goes, I'm thinking about forming the floats to a thin edge along their keels. As the boat heels more, the leeward edge gets more 'bite'. That's why I'm thinking the fore/aft position of the floats is so critical, because it locates the CLR of the float.

    Quite right though - one thing at a time. Just making up the floats and the beams will take a while...
     
  4. alan white
    Joined: Mar 2007
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    alan white Senior Member

    I guess the fore/aft location of the floats is easily adjusted if you allow for it. I didn't know you had a deck. i hesitate to click on links due to my slow connection speed. I will check it out now anyhow.
    Okay, I checked it out. Looks very simple. Not much lead required, I'd say. It's almost as if everything could be set up symmetrically as far as floats relative to main hull, and then a 5 to 7% lead for the mast and then experiment with the board.
     
  5. Deadeye
    Joined: Jan 2009
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    Deadeye Bender of Nails

    Sounds good Alan, thanks for the help. 5-7% - I'll give it a shot !
     
  6. ancient kayaker
    Joined: Aug 2006
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    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Deadeye: that reminds me of the first couple of boats that I designed and built myself; one trip around the lake was all either of them got then it was "where's the chainsaw ..." - on later designs I dumped the 3-plank/flat bottom approach in favor of 5-plank designs with bilgeboards at about 30 deg. Much quicker and delivered more stability with less beam, and still easy to build.

    I had a fiberglass canoe about that size long ago which was heavy and sluggish, although it had enough stability for me to use a proper seat and regular canoe paddle. I experimented with a sail rig, about 35 sq ft, a 7 ft long ama on one side, leeboard and rudder. mostly it dragged its butt but on one occasion it suddenly shot forward at a great rate. I looked around for clues to what was happening and noticed the ama float was clear of the water. Not knowing anything about sailing at that time I immediately let out the sail; as I figured I needed the float in the water for stability.

    The lesson I learned from that was, the ama was a serious drag.

    I had a follow-up effort planned; I figured for any performance either the ama had to plane or be kept out of the water. I decided for the later course and built two smaller floats 3.5 ft long one on each side, the intent being to sail with both about 4" clear of the water but with the stability there in case I needed it. Being completely open it was not a boat that could be safely heeled very far. Events overtook me and it did not happen.

    Further experiments with sailing rigs for canoes and kayaks convinced me that it would be difficult to get real performance unless I was prepared to undertake the kind of acrobatics seen on the international sailing canoe class http://www.intcanoe.org/newsite/ -I found that because of the long narrow hulls designed to track well under paddle power, my boats were not in a hurry to change direction and because of the light weight they lost speed and were frequently caught in irons when changing tack.

    -on one of my sailing experiments I used a cast iron plumbing fitting designed to support a pipe running through a floor. it was a flange tapped for a pipe with four screw holes. With a short length of iron pipe inserted it made an entirely adequate mast step for a hollow mast made from an length of aluminum tubing. Home Hardware carries them in a variety of sizes.

    I had the mast mounted so the center of area of the sail was midships with a pivoting leeboard at the same location: I didn't get to experiment with different mast locations, but it seemed to balance well. For safety's sake however, figuring that it would probably not head upwind and hove to if I fell overboard, I held the sail sheet in my hand.

    Good luck with your efforts!
     
  7. bistros

    bistros Previous Member

    AK:

    Here is a thread you might want to read.

    The person proposing this (Steve Clark) is one of North America's most successful small boat builders and a former sailing canoe world champion (as well as other boats). There is a follow up thread as well. I'm still very intrigued by the idea.

    --
    Bill
     
  8. ancient kayaker
    Joined: Aug 2006
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    ancient kayaker aka Terry Haines

    As you pointed out in the link Bistros, a paddling canoe has a different shape and therefore far less stability than a sailing canoe. Once you raise your butt from the seat to gunnel level for hiking the stability goes down further so I think the amas are essential for safety and to increase the sailing/swimming ratio. Without an ama I found a paddling canoe could not support much sail unless I sat on the bottom, I couldn't do much from down there.

    Once you balance the whole thing it should go like stink with a decent sail area. My first ama had about 125 lb buoyancy, way too big, I was thinking sit on the gunnel without tipping. Later I decided twin amas about 35-50 lb each would be plenty. I don't think shape is very important as the intent is to keep them dry.

    I think the racks are intriguing. I mounted my big ama on a wood parallelogram outrigger with a simple star-knob handle with a 1/4" stud (bought from a tool shop) to lock it by friction. It would have converted to a rack easily. No reason not to have amas out on the racks. You could also have swimming noodles on the rack while learning to ride it.

    The mast I used was stayed with chains on yet another outrigger: took too long to set up and interfered with sailing; I definitely recommend an unstayed mast. The link Bistros provided leads to a commercial canoe sailing kit which had sails of 45 & 55 sq ft; mine had about 35, not enough for decent performance, if I did it again I would likely double that. An unstayed mast for that size sail would be in the region of 2-2.5" diameter, clean spruce, based on what I have read. My mast was attached to a simple board clamped across the gunnels (the average canoe thwart is not strong enough); with an unstayed mast it should pass through the board to a solid mast step on the floor of the hull.

    There should be no real difference between a leeboard and a daggerboard if the boat is not heeled much. make the rudder area huge!
     
  9. Deadeye
    Joined: Jan 2009
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    Deadeye Bender of Nails

    More great stuff, thanks guys. Especially using a closet flange as a mast step...that's a bit of genius right there.

    I definitely know about 'first boat syndrome'...given the time invested, you don't want to hack it up and start again. But it DID show you what it ought to have been...

    My first start-to-finish project was a S&G rowboat, though I didn't know it was called 'S&G' at the time. Imagine a big Optima only not so many curves, lol. It was a planter at my sister's cabin for most of its life - a role for which it was marvelously suited...aah yes, the gap-filling abilities of thickened epoxy were sorely tested, to say the least.

    Thanks for the link bistros - I haven't spent much time on SA. Also in regards to your stability comment, building a deck and cockpit in this thing was specifically to get my butt onto the bottom of the boat. In whitewater canoing, you get your knees onto the bottom of the boat and your butt rests against the seat/thwart, but only for balance. When I launched this boat, that's how I started out. Even so, the stability just wasn't there, so I figured a cockpit and deck would get me lower in the boat. Definitely a step in the right direction, but...

    My 'vision' (if hazy) is something like a waterborne ice-racer. Control will be strictly from the cockpit using footpedals and a mainsheet. AK, your sail area recommendation makes me want to put the lateen on the back burner and go with a sloop rig. Granted, coming about would be either a comedy of errors or a hydrodynamic ballet (I'm leaning toward the former...)

    A daggerboard trunk would make it too difficult to kick out underwater, so a leeboard it is. No one's addressed it, so I must be missing something in my idea of a skeg on each of the two amas ? It would take some time to dial in for sure, but it ought to prevent making leeway on a reach, no ? My concern would be a tendency for it to 'dig in' (say, a gust) and turn turtle.
    I guess it would have to be a little forward of center to make turning easier as well ?

    At any rate, thanks for all your thoughts and keep 'em coming ! This weekend I'll try and make time to draw or mock up a profile for the amas and post it for any suggestions you may care to offer.
     
  10. ancient kayaker
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    ancient kayaker aka Terry Haines

    I either didn't see or didn't understand your idea of a skeg on each of the two amas to prevent leeway.

    A deep board, narrow fore and aft will generate less drag than skegs on the amas, and is easier to raise in shoal water. I used a narrow ply leeboard 4 times as deep as its width around 10% of sail area, and started with a small sail. My rudder was about 50% of the board area, similar shape. Both were held down by bungy cords and pulled up with a woven nylon line (easy on the hands).
     
    Last edited: May 16, 2009

  11. Deadeye
    Joined: Jan 2009
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    Deadeye Bender of Nails

    Thanks for the numbers.
    I'm off for the next couple days so I think I'm going to play with this down in the shop. I'll check in again after I've cut some wood...
     
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