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Thread: When manhours isn't a consideration in hull construction

  1. #1
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    Default When manhours isn't a consideration in hull construction

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    Default Re: When manhours isn't a consideration in hull construction

    What is the point of the inner transverse layer. Not the best use of materials IMHO.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: When manhours isn't a consideration in hull construction

    I don't know anything about that particular hull, but I do know that one of the aims of multi-layer cold-molding was that there would be grain structure in 90, +45, -45, and 0-degree orientation so that there would be even stress distribution within the hull skin at the stiffest & lightest structural arrangement. AFAIK, the ambition was somewhat abandoned during the IOR years because carbon fibre became price-competitive, then less expensive, that the labour-intensive 4-layer veneer cold-molding process.

    Edit to add: I do know that in some non-competitive hulls, the inner layer of veneers was laid fore-and-aft to create a pleasing interior of varnished wood "planks".
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    Default Re: When manhours isn't a consideration in hull construction

    One piece of trivia;during the IOR years the hulls tended toward a faceted shape to take advantage of the measurement points and there were many with a very flat central panel.I have known of a designer who stipulated the the ends of the +/- 45 degree layers should be cut square to the run of the veneer thus creating a herringbone joint line.It avoided having a single central joint line and seemed to me to be a good idea.

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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by mmd View Post
    AFAIK, the ambition was somewhat abandoned during the IOR years because carbon fibre became price-competitive, then less expensive, that the labour-intensive 4-layer veneer cold-molding process.
    I'm under the impression that carbon fiber needs vacuum bagging and perhaps heat? At least, I've not seen it done any other way. For the amateur, the technique you show tends to produce a naturally fair hull with less technology.

    Or am I wrong?

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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by mmd View Post
    I don't know anything about that particular hull, but I do know that one of the aims of multi-layer cold-molding was that there would be grain structure in 90, +45, -45, and 0-degree orientation so that there would be even stress distribution within the hull skin at the stiffest & lightest structural arrangement. AFAIK, the ambition was somewhat abandoned during the IOR years because carbon fibre became price-competitive, then less expensive, that the labour-intensive 4-layer veneer cold-molding process.

    Edit to add: I do know that in some non-competitive hulls, the inner layer of veneers was laid fore-and-aft to create a pleasing interior of varnished wood "planks".
    I'm thinking hull girder. Ford and aft on top and bottom flanges to take tension and compression loads, 45degrees on the sides to transfer shear loads from top to bottom, Plus span breakers for pressure loads on the panels. I can't see how transverse contributes much.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by CWSmith View Post
    I'm under the impression that carbon fiber needs vacuum bagging and perhaps heat? At least, I've not seen it done any other way. For the amateur, the technique you show tends to produce a naturally fair hull with less technology.

    Or am I wrong?
    If you are going to the sophistication of carbon fibre, vacuum bagging gives you the maximum fibre with the minimum resin matrix. Both lighter and optimum strength. The need for heat may be to help the particular resin of choice set in good time.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by Peerie Maa View Post
    If you are going to the sophistication of carbon fibre, vacuum bagging gives you the maximum fibre with the minimum resin matrix. Both lighter and optimum strength. The need for heat may be to help the particular resin of choice set in good time.
    Heat is used for pre-preg, but maybe that is cloth and not carbon fiber? The heat activates the epoxy. Commercial builders buy ovens big enough to hold the entire hull for that purpose and run the vacuum lines out the side. I can't see amateurs doing that.

    I'm just wondering how much carbon fiber has made it into the amateur build beyond building experimental dingy masts and such.

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    Default Re: When manhours isn't a consideration in hull construction

    Maybe it is the "cosmetic" veneer layer, Nick. Pretty up the interior a bit.

    CW, you are not wrong. Carbon fibre is normally purchased in pre-preg form which requires heat and usually vacuum-bagging for curing, but the fabric can be had in dry cloth form, just like 'glass, and manually impregnated with epoxy resin. This is not the norm, as carbon fiber is much more difficult to wet-out than 'glass. Wood veneer is an amateur-friendly technology, but the biggest challenge is avoiding inter-laminar voids or pockets filled with epoxy, both of which create a weak spot in the hull structure.

    Edit to add: CW, smallish carbon fibre hulls (up to 30 ft. or so, and usually racing dinghy or catamaran hulls) are successfully built by amateurs using heat-cured pre-pregs. A common method is, after the fabrics are laid on, a Styrofoam "autoclave" is built (or, having been pre-built, slid in place), a vacuum bag placed over the hull, and heat applied and vacuum pulled to the hull. However, it is ginormously wasteful of construction materials and the process is not for the faint of heart.
    Last edited by mmd; 09-11-2017 at 05:32 PM.
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    Default Re: When manhours isn't a consideration in hull construction

    ^ Oh, that is so cool!

    I assume carbon fiber requires a mold, so in effect you have to build 2 hulls? Anything for a victory!

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    Default Re: When manhours isn't a consideration in hull construction

    First you build a strongback. Then you build hull forms on top of the strongback. Then you "plank" the hull with foam strips. Then you fair the foam "hull". Then you skin the foam hull with fiberglass. Then you fair the fiberglass. Then you paint the fiberglass with epoxy. Then you wet-sand the epoxy. Then you build a styrofoam autoclave over your boat mold. Then you paint release agent on the epoxy on the hull plug. Then you skin-out the hull with pre-preg carbon. Then you apply a vacuum bag to the whole hull. Then you draw down a vacuum. Then you apply heat. Then you strip off the vacuum bag and throw it away. Then you disassemble your Styrofoam autoclave and throw it away. Then you paint epoxy on the carbon fiber hull. Then you wet sand the hull. Rinse and repeat those last two steps a couple of times. The you pry the hull off the mold. Then you begin to build your boat.

    Like I said, you gotta be dedicated...
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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by mmd View Post
    Like I said, you gotta be dedicated...
    Not me! I'd rather go sailing. It does sound interesting, but I think I'm too lazy.

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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by mmd View Post
    First you build a strongback. Then you build hull forms on top of the strongback. Then you "plank" the hull with foam strips. Then you fair the foam "hull". Then you skin the foam hull with fiberglass. Then you fair the fiberglass. Then you paint the fiberglass with epoxy. Then you wet-sand the epoxy. Then you build a styrofoam autoclave over your boat mold. Then you paint release agent on the epoxy on the hull plug. Then you skin-out the hull with pre-preg carbon. Then you apply a vacuum bag to the whole hull. Then you draw down a vacuum. Then you apply heat. Then you strip off the vacuum bag and throw it away. Then you disassemble your Styrofoam autoclave and throw it away. Then you paint epoxy on the carbon fiber hull. Then you wet sand the hull. Rinse and repeat those last two steps a couple of times. The you pry the hull off the mold. Then you begin to build your boat.

    Like I said, you gotta be dedicated...

    I was following until you said styrofoam autoclave. The autoclaves I am familiar with are huge steel vessels capable of withstanding pressure. Do you have any pics or details of that part of the process? Is it applying heat and pressure?
    Tom

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    Default Re: When manhours isn't a consideration in hull construction

    Tom, I used the term 'autoclave' incorrectly, just for effect. Sorry. The pressure on the c-f plies is via the vacuum applied between the hull surface and the vacuum bag; the external air pressure exerts an even pressure over the whole hull surface. The Styrofoam "autoclave" is essentially just a big insulating building over the hull to keep warm air inside and to ensure even heat distribution. I can't find any pics quickly (SWMBO is calling me for supper), but I believe that Professional Boatbuilder magazine did a feature on a boatbuilder that had pics of a 'curing shed' built over a hull.
    Hope for the best, but plan for the worst.

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    Default Re: When manhours isn't a consideration in hull construction

    Quote Originally Posted by mmd View Post
    Tom, I used the term 'autoclave' incorrectly, just for effect. Sorry. The pressure on the c-f plies is via the vacuum applied between the hull surface and the vacuum bag; the external air pressure exerts an even pressure over the whole hull surface. The Styrofoam "autoclave" is essentially just a big insulating building over the hull to keep warm air inside and to ensure even heat distribution. I can't find any pics quickly (SWMBO is calling me for supper), but I believe that Professional Boatbuilder magazine did a feature on a boatbuilder that had pics of a 'curing shed' built over a hull.
    Gotcha. Makes sense now. Thanks!
    Tom

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    Default Re: When manhours isn't a consideration in hull construction

    . I can't see how transverse contributes much
    Mayhap it helps ensure that seams are not directly atop seams?

    Kevin
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