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Thread: Outrigger location

  1. #1
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    Default Outrigger location

    16' canoe, 8' outriggers. how does putting all three centers inline compare with having the three bows inline?

    this would be flat water lake, some larger river/bay sailing.

    outriggers would be flown or just barely touching water





  2. #2
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    Default Re: Outrigger location

    I'm going to guess that optimal outrigger placement has to be sorted out with the sail plan, assuming this set up is for sailing. If its for paddling only I'd guess in the middle would make maneuvering easier. Close to the middle, or just slightly aft seems common

    Last edited by JimD; 05-10-2017 at 10:03 AM.
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  3. #3
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    Default Re: Outrigger location

    I imagine placement has to do with what kind of stability you're going for and the size and shape of your outriggers/amas. Do you always want to sail it flat like a trimaran? Or are they to be more like the gull wing amas on a Solway-Dory sailing canoe and used primarily as safety floats/training wheels. 8' amas would probably be more for flat sailing and inline with the boat center. What experience I have with large single outriggers, that makes sense to me. I think they'd move forward more if they were smaller or your main hull was shaped fuller forward. Canoes are usually prettysymmetrical fore and aft. If yours is, I'd say put them center.

    Someone more versed might come along soon. There's also an Outrigger and Proa thread that you could pose the question on. Several designers chime in there.

    -Trevor

  4. #4
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    Default Re: Outrigger location

    appreciate the replies. i have seen production boats with either configuration hence my question.

    primarily i'm concerned about stability because my two sons are smaller and I dont want to flip the canoe. its is not a high performance boat and we will not be breaking any speed records. initially i had thought to use much smaller flown outriggers like on the solway dory canoes but figured perhaps bigger might be better if I can rig up a trampoline system ala the hobie island kayak my boys can goof around with a bit more room.

  5. #5
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    Default Re: Outrigger location

    First off, you need to know where the center of buoyancy of the outriggers or floats or amas, such as they are called, is located. Most amas locate the center of buoyancy forward of the centerline, but many simpler amas made for canoes and kayaks are symetrical fore and aft or close to it.

    When your boat is pressed hard, the lift provided by the ama will act at the center of buoyancy, so you have to think about how this will affect the trim of the main hull. The standard approach is to put the center of buoyancy of the ama ahead of the center of buoyancy of the main hull (vaka to some.) In doing this, as the boat heels, the main hull assumes a bow-up attitude. This is good for insuring said bow doesn't dive beneath the waves, and is the safest approach. If taken too far, it will adversely affect performance, but it's definitely the safer configuration.

    The easy answer to your question is to just line the bows up, and if the amas are symmetrical fore and aft this would probably be a good way to go. If your amas are fuller forward, then the bows should most likely (we're dealing here without any numbers to work with) be aft of the main hull a bit. What you don't want to see is any of the bows diving underwater, and when the amas are further forward, they tend to work in concert with the main hull to keep the water under the boat, not over it.

    Any photos to share?
    -Dave

  6. #6
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    Default Re: Outrigger location

    Storer has a good outrigger plan for sale, at a good price too, not sure if you have seen in. It is the larger style, not the Soloway type, so you could tramplolean it for the boys. Storer seams pretty helpful if you get those plans My guess is he would help with placement and such.

    http://www.storerboatplans.com/wp/bo...ailing-videos/

  7. #7
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    Default Re: Outrigger location

    Quote Originally Posted by Woxbox View Post
    First off, you need to know where the center of buoyancy of the outriggers or floats or amas, such as they are called, is located. Most amas locate the center of buoyancy forward of the centerline, but many simpler amas made for canoes and kayaks are symetrical fore and aft or close to it.

    When your boat is pressed hard, the lift provided by the ama will act at the center of buoyancy, so you have to think about how this will affect the trim of the main hull. The standard approach is to put the center of buoyancy of the ama ahead of the center of buoyancy of the main hull (vaka to some.) In doing this, as the boat heels, the main hull assumes a bow-up attitude. This is good for insuring said bow doesn't dive beneath the waves, and is the safest approach. If taken too far, it will adversely affect performance, but it's definitely the safer configuration.

    The easy answer to your question is to just line the bows up, and if the amas are symmetrical fore and aft this would probably be a good way to go. If your amas are fuller forward, then the bows should most likely (we're dealing here without any numbers to work with) be aft of the main hull a bit. What you don't want to see is any of the bows diving underwater, and when the amas are further forward, they tend to work in concert with the main hull to keep the water under the boat, not over it.

    Any photos to share?
    This concurs with my understanding of an outrigger ama, which in the OP case appears to be intended as a float, or leeward ama.
    Diagonal stability will improve as the float is moved forward, but there comes a point where the displacement volume is over-pressed and it dives and will be tripped over.
    Diagonal stability achieved by shifting live ballast out to w/ward and sternwards will help to prevent nosedives. So an outrigger beam further aft will help when hiking out here. This probably means two outrigger beams are need each side one towards the stern of the float and one further forwards.
    Placement of these beams depends on how far aft they can connect to the float. At 8 float length, the after beam will be right on the pointy end of the float (if canoe shaped) when its other end lines up with the centre hull bow.... on account the the main hull, canoe vaka or boat being 16' length

  8. #8
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    Default Re: Outrigger location

    I've drafted up a sketch about what I am envisioning. I only drew one outrigger but I would like two symmetrical 14' long ones from 8'' PVC (I have 15 sticks of 15' long PVC from a project we just finished) End caps would be foam and glass shaped like the bow of a canoe.

    I have not marked the leeboard as im not entirely sure where the best place is. thought I might make one that could be moved around until I could find the best spot. Sail type will likely be a bermuda rig, about 40sqft.

    Currently my biggest concerns are having so much weight in the back and ability to control the sail from the back overtop of my kids.

    Any thoughts?

    https://www.boatdesign.net/attachmen...aft-jpg.133776

    cause I cant figure out how to post the picture here.

    Last edited by Eciton; 06-09-2017 at 08:40 AM. Reason: cant figure out picture posting stuff

  9. #9
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    Default Re: Outrigger location

    With 40 square feet of sail, your heeling forces will be pretty small. The tubes you plan to use for the amas will give you about 140 pounds of buoyancy each. With a more aggressive rig, you'd be driving those tubes underwater pretty often, but with the conservative sail plan you have in mind, you'll probably be alright. (But no guarantees, of course. There are lots of variables in these schemes.) A simple clamp-on leeboard that you can experiment with is the way to go. The best place for it will depend on the sail size, shape and location. Only rule of thumb is better too far forward than too far aft.

    Don't worry about sheeting the sail over the kids' heads. After you've removed their hats a few times they'll learn to duck. Just keep the boom high enough so they don't get bonked hard. I'd suggest a sprit boom on a leg-o-mutton sail. Simple, self-vanging and the sprit rides high enough to clear everyone's heads.

    Having your weight too far aft could be an issue. The only way to find out is to give it a try.

    -Dave

  10. #10
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    Default Re: Outrigger location

    Here's your basic leg-o-mutton sail. I lifted it from this page, which also has directions on making one with polytarp. Something I've yet to attempt.

    -Dave

  11. #11
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    Default Re: Outrigger location

    thanks dave!

    After some helpful criticism about the weight distribution and the outrigger material choice I have redesigned a little bit. the current design has considerably better weigh distribution but i'm unsure on the outriggers. I wanted to keep them to 8' max so i could make one from each 4x8 sheet of ply but...

    [IMG]https://www.boatdesign.net/attachmen...t2-jpg.133799/[/IMG]

    EDITED: how do you insert photos in the post?

  12. #12
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    Default Re: Outrigger location

    After you have the photo posted on another site, copy the address. Then come back here and click on the photo icon (middle one in the group of five).
    Click on the URL tab
    Paste the address into the box
    Uncheck the "retrieve etc..." box
    Then click OK and the photo will display.

    Note -- this website doesn't reformat or resize images. A good size is to make them 800 pixels wide for posting most images.


    -Dave

  13. #13
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    Default Re: Outrigger location

    And back to the amas -- if you make them that short, they'll act like brakes somewhere just north of 3 knots unless you're shifting your weight to keep them from digging in. Long and skinny is always better. The PVC isn't ideal, either, of course. That stuff is quite heavy, and the shape is far from ideal. If you could put a bow in a tube the immersed portion would have a much more "boaty" shape, and also keeps the bow and stern above the surface. Best though, is to have at it and run a few experiments. These things are easily modified.
    -Dave

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