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Thread: skin on frame sailboat?

  1. #1
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    Default skin on frame sailboat?

    I'm thinking of building a cartopper, and it seems the lightest way to build cheaply is skin on frame. Thing is, skin on frame is too flexible for sailboats, is the common wisdom. Can this be overcome, or would I just not have a boat that responds well to gusts? I've thought of building a plywood tub with a web frame around it for stiffness, with the fabric on the outside of the frame, but it seems like that would be about as heavy as a plywood boat.

    any ideas?

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    Default Re: skin on frame sailboat?

    Brian Schulz's sof ducker came out pretty well. Used ply decks and we ran the daggerboard through the deck as was done on some historic boats. Check it out at Cape Falcon.
    Ben Fuller
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    Default Re: skin on frame sailboat?

    Thanks for that. I'll study it closely. I haven't quite settled on what shape I'd want, the notion came to me when I was looking at a possible storage space and thinking about some of the illustrations for the document I sent you. This one, in particular:

    15' arc bottom, narrow waterline, low chine 5-19-2018 5-04-24 PM 1660x754.bmp.jpg

    Although I may end up settling on something more stable. I'm thinking it would be inexpensive to build, especially if I use a Laser practice sail, those are dirt cheap.

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    Default Re: skin on frame sailboat?

    Have you looked at Dave Gentry's lineup? The Light Melonseed looks pretty interesting to me.

    http://gentrycustomboats.com/NewHomebuilderplans.html
    -Dave

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by Woxbox View Post
    Have you looked at Dave Gentry's lineup? The Light Melonseed looks pretty interesting to me.

    http://gentrycustomboats.com/NewHomebuilderplans.html
    Thanks, that does look interesting.

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    Default Re: skin on frame sailboat?

    There's the Monfort boats too http://gaboats.com/boats/cricket12.html.

    Seems to me it would be simple and roughly follow convention to have a web comprised of stem, king plank, mast partners, daggerboard case, hog, rudder post. Everything else is bagatelle.

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    Default Re: skin on frame sailboat?

    Hmm. 250 hours instead of 30 hours. I wish I could get a better look at the Melonseed's hull shape, is it a profile boat that is intended to look like the original, or does it follow traditional lines?

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    Default Re: skin on frame sailboat?

    One thing I've thought about for years is a 14 footer with an Avenger type hull in skin on frame. It would be a whole lot lighter, so I could get by with a smaller rig, but it's a very stable hull shape. Something like this:

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    Default Re: skin on frame sailboat?

    Thanks for the nod, Wox. I thought I had already fed SOF propaganda to everyone on the forum, but apparently not.

    Quote Originally Posted by johnw View Post
    I'm thinking of building a cartopper, and it seems the lightest way to build cheaply is skin on frame. Thing is, skin on frame is too flexible for sailboats, is the common wisdom. Can this be overcome, or would I just not have a boat that responds well to gusts?
    John, in addition to day sailing all of my boats in a variety of conditions, I've torture tested a couple of my sailing designs in the Everglades Challenge. There's no flexing going on - at least nothing perceptible. I put a lot of thought into that issue, and it seems to have worked out well, so far.

    The Light Melonseed has a multi-chined hull, but other than that the shape is true to Chapelle's. The cockpit is modified, and she has a modern centerboard, of course.
    One could put a Laser rig in her, though they are relatively tall and heavy, with all that implies. One would want reef points . . . like the originals, she does not have a planing hull, in any case.
    LM1.jpg
    M8.jpg

    But, for solo cartopping, with stability, you might consider my Piankatank River Pram. She's a delight to sail, and very easy to get up on the roof of a car or truck. Probably won't fulfill one's need for speed - though she does move right along.
    Annabelle is just a bit harder to car top, but she can get up and go. Not as stable as the others, however.

    And, I'm happy to answer questions and/or offer advice whatever you build - including something to your own design.

    Dave

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by DGentry View Post
    Thanks for the nod, Wox. I thought I had already fed SOF propaganda to everyone on the forum, but apparently not.



    John, in addition to day sailing all of my boats in a variety of conditions, I've torture tested a couple of my sailing designs in the Everglades Challenge. There's no flexing going on - at least nothing perceptible. I put a lot of thought into that issue, and it seems to have worked out well, so far.

    The Light Melonseed has a multi-chined hull, but other than that the shape is true to Chapelle's. The cockpit is modified, and she has a modern centerboard, of course.
    One could put a Laser rig in her, though they are relatively tall and heavy, with all that implies. One would want reef points . . . like the originals, she does not have a planing hull, in any case.
    LM1.jpg
    M8.jpg

    But, for solo cartopping, with stability, you might consider my Piankatank River Pram. She's a delight to sail, and very easy to get up on the roof of a car or truck. Probably won't fulfill one's need for speed - though she does move right along.
    Annabelle is just a bit harder to car top, but she can get up and go. Not as stable as the others, however.

    And, I'm happy to answer questions and/or offer advice whatever you build - including something to your own design.

    Dave
    So, here's the thing. If it's true to Chapelle's lines, it's not a planing hull, and that's one of the things I wanted. The deflection angle at the stern of a melonseed is too steep for planing.

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    Default Re: skin on frame sailboat?

    Montfort did a hybrid with a ply bottom and skin on frame sides - blivit 13
    http://gaboats.com/boats/blivit13.html

    As all skin on frame boats need bottom boards to stand in this seemed like a good idea. People have also done pram dinghies this way by when I did a CAD model the weight savings for SOF was negligible. It was a lot of light ribs type construction and only small. I am sure there is a law of diminishing returns with as SOF gets smaller

    I think a larger boat with a Dave Gentry type frame and about half the bottom made of ply would be worth looking at, the ply part would make a good planning surface.

    johnw what are you look for a primary requirement of this craft- lightness for car topping, or performance? One or two up?

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    Default Re: skin on frame sailboat?

    And how much are you prepared for invest in a decent roof rack. Manhandling just a sea kayak onto the roof, without dinging anything, can be a challenge on a gusty day. Get one of those racks with a roller across the back (I'm assuming a wagon or SUV shape vehicle), and suddenly loading something quite a lot bigger and heavier becomes easy.

    Pete
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    Default Re: skin on frame sailboat?

    Sailing a canoe as I do, I see no reason that a SOF sailing canoe would not work similarly.

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by tink View Post
    Montfort did a hybrid with a ply bottom and skin on frame sides - blivit 13
    http://gaboats.com/boats/blivit13.html

    As all skin on frame boats need bottom boards to stand in this seemed like a good idea. People have also done pram dinghies this way by when I did a CAD model the weight savings for SOF was negligible. It was a lot of light ribs type construction and only small. I am sure there is a law of diminishing returns with as SOF gets smaller

    I think a larger boat with a Dave Gentry type frame and about half the bottom made of ply would be worth looking at, the ply part would make a good planning surface.

    johnw what are you look for a primary requirement of this craft- lightness for car topping, or performance? One or two up?
    I'm thinking making it light will help make it fast, and I'm thinking one up, with enough potential displacement to carry two. A roomy cockpit is a plus for this reason. I'd like to make it self-rescuing.

    The more I look at the Gentry design, the better I like it. Only the stern does worry me, the Chapelle lines show a boat built around an almost full-length, rather wide straight keel, which means the stern is fairly veed and the run is short and steep. Dave, I can't really tell from the picture, is that true of your design? If so, it's better for rowing than the kind of boat I have in mind, but has a lower top speed that I'd hoped for.

    The Blivit looks awesome, by the way, is it self-rescuing?
    Last edited by johnw; 06-03-2018 at 01:32 PM.

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by epoxyboy View Post
    And how much are you prepared for invest in a decent roof rack. Manhandling just a sea kayak onto the roof, without dinging anything, can be a challenge on a gusty day. Get one of those racks with a roller across the back (I'm assuming a wagon or SUV shape vehicle), and suddenly loading something quite a lot bigger and heavier becomes easy.

    Pete
    That's what I was thinking of, I've got a small truck with a cap on the back, so there's a nice surface for putting a rack.

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    Default Re: skin on frame sailboat?

    I would worry a bit about that wide, flattish bottom. With traditional light bent frames, it would be a week point. Maybe with Dave Gentry's system of plywood bulkheads and fewer, heavier stringers it would be OK? With some lighter intermediate stringers to keep the fabric from going deeply concave between heavier stringers.

    Quote Originally Posted by johnw View Post
    One thing I've thought about for years is a 14 footer with an Avenger type hull in skin on frame. It would be a whole lot lighter, so I could get by with a smaller rig, but it's a very stable hull shape. Something like this:

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by Bill Mercer View Post
    I would worry a bit about that wide, flattish bottom. With traditional light bent frames, it would be a week point. Maybe with Dave Gentry's system of plywood bulkheads and fewer, heavier stringers it would be OK? With some lighter intermediate stringers to keep the fabric from going deeply concave between heavier stringers.
    See post #1.

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    Default Re: skin on frame sailboat?

    I've had two thoughts.
    Historically, think St Brendan's currach, there was as much wood in a sof boat as in an Old Town canoe.
    Then I thought may be geodesics might be strong enough. You probably would need to build over a form.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by Peerie Maa View Post
    I've had two thoughts.
    Historically, think St Brendan's currach, there was as much wood in a sof boat as in an Old Town canoe.
    Then I thought may be geodesics might be strong enough. You probably would need to build over a form.
    The Blivit uses geodesics:


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    Default Re: skin on frame sailboat?

    Quote Originally Posted by tink View Post
    Montfort did a hybrid with a ply bottom and skin on frame sides - blivit 13
    http://gaboats.com/boats/blivit13.html

    As all skin on frame boats need bottom boards to stand in this seemed like a good idea. People have also done pram dinghies this way by when I did a CAD model the weight savings for SOF was negligible. It was a lot of light ribs type construction and only small. I am sure there is a law of diminishing returns with as SOF gets smaller

    I think a larger boat with a Dave Gentry type frame and about half the bottom made of ply would be worth looking at, the ply part would make a good planning surface.

    johnw what are you look for a primary requirement of this craft- lightness for car topping, or performance? One or two up?
    Blivit does look good - nice lines, nice weight, nice foils, nice idea!
    Last edited by Chris249; 06-03-2018 at 06:19 PM.

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by johnw View Post
    The Blivit uses geodesics:

    On a solid bottom.
    With enough bottom stringers and geodesics you might not need the ply bottom.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: skin on frame sailboat?

    Blivit is full on planing machine. I'm not sure about her longevity, shrouds and board support, however I do know the daggerboard trunk is pretty stout after testing it on a sandbar when I had it planing.
    Ben Fuller
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    Default Re: skin on frame sailboat?

    Quote Originally Posted by Ben Fuller View Post
    Blivit is full on planing machine. I'm not sure about her longevity, shrouds and board support, however I do know the daggerboard trunk is pretty stout after testing it on a sandbar when I had it planing.
    Well, that's a pretty good recommendation. 200 hours, though, those geodesic boats take a lot of labor.

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    Default Re: skin on frame sailboat?

    You cant expect to get the ideal boat for your needs if you are not willing to invest the time to build it. Is there a reason you have not bought a second hand Laser?

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    Quote Originally Posted by johnw View Post
    I'm thinking making it light will help make it fast, and I'm thinking one up, with enough potential displacement to carry two. A roomy cockpit is a plus for this reason. I'd like to make it self-rescuing.

    The more I look at the Gentry design, the better I like it. Only the stern does worry me, the Chapelle lines show a boat built around an almost full-length, rather wide straight keel, which means the stern is fairly veed and the run is short and steep. Dave, I can't really tell from the picture, is that true of your design? If so, it's better for rowing than the kind of boat I have in mind, but has a lower top speed that I'd hoped for.

    The Blivit looks awesome, by the way, is it self-rescuing?
    You are trying to find the holy grail of sailboat design, and something I have thought about for far too many long hours.
    One of my hot contenders has always been a tacking outrigger.

    Stick with me, there is some logic to this.
    The main hull, vaka:
    >Simple quick construction of ply with chine logs
    > Long and thin, fast, light and easy to get on a rack,
    > Simple enclosed buoyancy will be minimum width and depth, again helps with racking and also storage
    > Depending upon design lateral resistance can be provided by the vaka.

    I can hear you saying that’s all good but then I need beams (aka) and floats (ama), which is very true but these are relatively small, light and with correct design simple to make. They could be designed to fit inside you car.

    I have always admired flaquita

    http://www.flaquita.net



    And Arara

    http://arpex.blogspot.com/search?q=arara



    But you can go SOF

    http://www.capefalconkayak.com/outri...ingcanoes.html



    http://gentrycustomboats.com/splinter.html


    You could even go hybrid, SOF above the waterline.

    Anyway just a thought but you could get a good speed, still roof rack and a simple and quick build




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    Default

    Very much work in progress
    14ft vaka,
    40lb easy probably 30lb



    https://tinkboats.wordpress.com
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    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
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    Default Re: skin on frame sailboat?

    What, exactly, is meant by the recurring phrase "self rescuing"

    Self righting I understand
    Self rescue- in a canoe/kayak context means capable of being recovered from a knock down or capsize by the crew.


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    Default Re: skin on frame sailboat?

    When righted, the boat drains itself. No need to bail.
    -Dave

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    Default Re: skin on frame sailboat?

    Quote Originally Posted by DGentry View Post


    But, for solo cartopping, with stability, you might consider my Piankatank River Pram. She's a delight to sail, and very easy to get up on the roof of a car or truck. Probably won't fulfill one's need for speed - though she does move right along.


    And, I'm happy to answer questions and/or offer advice whatever you build - including something to your own design.

    Dave
    Here is a Piankatank pram, stretched to 10 feet, powered by a drop-in Opti rig:

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    Default Re: skin on frame sailboat?

    Blivit is not self rescuing. And I suspect that she could use some shroud/ partners beefing for longevity. Pretty much any self rescuing boats have to have tanks or bags. With all of the plans around for skin on frame sailboards, you might go back to the original Sailfish concept.... the first truly self rescue sailing boat. ( at least that I know of).
    Ben Fuller
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    "Bound fast is boatless man."

  31. #31
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    Default Re: skin on frame sailboat?

    Quote Originally Posted by skaraborgcraft View Post
    You cant expect to get the ideal boat for your needs if you are not willing to invest the time to build it. Is there a reason you have not bought a second hand Laser?
    Yes. I am not strong enough to lift a Laser on top of my truck. That's why I thought of skin on frame. The Blivet weighs less than half what a Laser does.

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    Default Re: skin on frame sailboat?

    Sometimes you just build something (like a SOF catboat) for the love of the game.
    Quote Originally Posted by James McMullen View Post
    Yeadon is right, of course.

  33. #33
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    Default Re: skin on frame sailboat?

    Quote Originally Posted by tink View Post
    You are trying to find the holy grail of sailboat design, and something I have thought about for far too many long hours.
    One of my hot contenders has always been a tacking outrigger.

    Stick with me, there is some logic to this.
    The main hull, vaka:
    >Simple quick construction of ply with chine logs
    > Long and thin, fast, light and easy to get on a rack,
    > Simple enclosed buoyancy will be minimum width and depth, again helps with racking and also storage
    > Depending upon design lateral resistance can be provided by the vaka.

    I can hear you saying that’s all good but then I need beams (aka) and floats (ama), which is very true but these are relatively small, light and with correct design simple to make. They could be designed to fit inside you car.

    I have always admired flaquita

    http://www.flaquita.net



    And Arara

    http://arpex.blogspot.com/search?q=arara



    But you can go SOF

    http://www.capefalconkayak.com/outri...ingcanoes.html



    http://gentrycustomboats.com/splinter.html


    You could even go hybrid, SOF above the waterline.

    Anyway just a thought but you could get a good speed, still roof rack and a simple and quick build




    https://tinkboats.wordpress.com
    http://proasail.blogspot.co.uk
    What I get up to
    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
    https://youtu.be/oni-3rJzxqQ Sail Canoe
    https://youtu.be/eW078PPgJak Proa
    I actually have considered this, although many of these are a bit wet for sailing in the waters I live near. From my perspective, part of the beauty of these is that they come apart, and you don't have to lift the whole thing at once.

  34. #34
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    Default Re: skin on frame sailboat?

    Quote Originally Posted by Ben Fuller View Post
    Blivit is not self rescuing. And I suspect that she could use some shroud/ partners beefing for longevity. Pretty much any self rescuing boats have to have tanks or bags. With all of the plans around for skin on frame sailboards, you might go back to the original Sailfish concept.... the first truly self rescue sailing boat. ( at least that I know of).
    I sailed Sailfish quite a lot when my family lived on Okinawa back when I was a kid. I love those, but the Pacific Northwest is not the best place to sail one, unless you wear a dry suit. And yes, I did think about building one, then thought about how important warm water is to enjoying sailing them.

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    Default Re: skin on frame sailboat?

    Even at the size of build you're considering, you'll need to find a way to leverage this boat up onto the roof of your truck. Guaranteed you'll figure out a way to do it, though. I had a 13' SOF Gentry Whitehall and it was just on the edge of what I could lever up there. I usually found a way to skid it up from behind the truck up onto the rack. Or I'd have my wife come on out and help me pick the thing up. There was just that much less of a chance that I'd drop the thing or dent my truck. Getting it off was much easier. Gravity did most of the work.
    Quote Originally Posted by James McMullen View Post
    Yeadon is right, of course.

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