Cold-moulded dinghy plans?

Discussion in 'Sailboats' started by tomkcook, Oct 1, 2018.

  1. tomkcook
    Joined: Oct 2018
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    tomkcook Junior Member

    I'm trying to find plans for a 10-foot or so dingy suitable for sail rigging (though as I plan a junk rig it's unlikely I'll use the original rig - I'm reasonably happy calculating CLR/CE to come up with an equivalent rig) suitable for cold moulding.

    An hour or so on Google hasn't turned up a lot. Can anyone suggest something?

    Free is good, but not necessary.
     
  2. JamesG123
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    JamesG123 Senior Member

    Probably because stitch n' glue and even plank on frame is a far easier method at the scale of a dingy.

    Given the monoquque nature of cold-moulding, you can probably take the dimensions and lines of any hull that strikes your fancy and produce your own jigs.
     
  3. bajansailor
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    bajansailor Marine Surveyor

    The Fairey Duckling designed by Uffa Fox is quite famous, and has a good reputation - some pals of mine had one as the tender for their schooner 35 years ago, and they thought she was a wonderful dinghy.
    She is 'only' 9' long, but quite beamy, with good load carrying capacity, and she rows well (they never had an outboard, just sails and oars).
    It looks like you can buy plans here -
    Duckling http://www.uffafox.com/duckling.htm
     
  4. Doug Halsey
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    Doug Halsey Senior Member

    For home-building, I would highly recommend stitch & glue over cold moulding. Cold moulding is so labor intensive.

    When I was much younger, I built a Moth (11' long) & used over 10,000 staples to hold the veneer strips in place temporarily while the glue dried. It took a long time!
     
  5. tomkcook
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    tomkcook Junior Member

    Thanks all for the advice.

    I'm aware that cold moulding is not the best option for constructing a dinghy for its own sake - the point of it is partly to have a dinghy to mess about in and partly to get some hands-on experience with the method, with a view to building something bigger.
     
  6. Doug Halsey
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    Doug Halsey Senior Member

    That's great, as long as you know what you're getting into.
     
  7. messabout
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    messabout Senior Member

    I suggest that you consult the book: the Geogeon Brothers Book On Boat Construction. There is good information about cold mould construction there. Cold moulding a small boat is about the most sophisticated way to do it. I like the advantages of light weight monocoque construction and all that good stuff. It is the most laborious and demanding of builds but it promises to yield a fine specimen if done well.

    On the other hand a nice little boat made from Ocumee BS1088 ply is almost as light and strong, And a whole lot easier to build. The ultimate result in some cases favors the flat panel ply type in terms of performance.
     
  8. bregalad
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    bregalad Senior Member

    Most small boats can be adapted to cold molded construction.

    Early in 2017 I began building the 18' Light Batteau from John Gardner's The Dory Book as a rowing cruiser. I started lofting on Jan.1 and she was ready to launch on July 4. I built her on my front porch so while I had cover overhead I did not have any climate control and construction especially early on was slowed by weather and it was interrupted by two surgeries.

    I live out in the woods and freight truck wouldn't come within a mile or so of my house. To get okume or such meant big $$ and it would be delivered to a freight depot 50 miles away. Not acceptable. The sheet of so-called marine fir plywood that I got through my local lumberyard began to de-laminate just from humidity while leaning against the house under the porch roof. I sent it back.

    In the end I used the lightest, clearest 2x4's I could select and re-sawed them into 1-1/2" x 1/8" 'veneers" and cold molded the beast. In fairness I've had a fair bit of experience with cold molding and strip planking boats up to 30 feet. Is the method slow? Yes, but everything is of a very manageable size for the lone old-guy builder. The finished boat is about 100 lbs.

    I used 2 diagonal layers to finish ~1/4" thick.
    I used a Fasco stapler that takes 22ga. 3/8" crown staples (depending on manufacturer these go by 7, 71, BA71, C type), the most common staple in the upholstery business. That makes them cheap and readily available in a wide variety of sizes in galvanized and stainless. I used mainly 3/8" and 1/2" staples. I got the staples from floydtool.com where 3/8" leg staples are currently $3.00 for a box of 10,000. I drove and pulled ~17,000. There are no permanent metal fasteners anywhere in the hull. Other suppliers for staples that I would recommend are manasquanfasteners.com and fastenersusa.com.

    I drove the staples through the green plastic banding with which bundles of lumber and plywood are held together during shipping. My local lumberyard was kind enough to save it for me and I'd pick it up whenever I went to town. I cut it into ~2' lengths and would use 1 or 2 layers depending on how soft the particular wood was. Once the glue had cured I could 'unzip' a row of staples quite easily. I didn't try to keep an accurate track of the free strapping but I think I used about 4000 feet.

    For chines, frames, and gunwales I used KDAT treated yellow pine. A relatively higher grade of yellow pine kiln dried after treatment. It costs more that the usual run of treated lumber but way cheaper than anything more commonly recommended for boat use. Being dry it took glue without any problems. It is quite stiff and no pleasure to bend or twist.

    I decked over and enclosed about 5-1/2 feet at each end leaving just enough room for me to lay down and sleep on the floorboards in case I couldn't find a suitable campsite ashore. I have only needed that capability once. Usually I hang a hammock and tarp between trees ashore, backpacking style. Another benefit of the enclosed ends is flotation. Capsized she floats very high with the center of the gunwale clear of the water and is extremely easy to flip back upright. I have to rig an oar and fender to help me get back aboard. Someone younger (I'm 70), lighter and more nimble might fare better. Other than testing I haven't needed to play that game. The high ends and ample flair that are detriments rowing in strong winds do enable her to cope well with big powerboat wakes. I also cold molded some wing style outriggers. They are easily removed when coming alongside and enable the use of 8' 10" oars that I built.

    Also, I used no fiberglass anywhere in the construction. Several coats of epoxy and then paint. For freshwater use I used a hard copper non-antifouling bronze bottom paint from Kushpaint.com This is great stuff and stood up to repeated (careful) beaching on sandy beaches.

    To the OP. Find a design you like and adapt it rather than build something you aren't quite as happy with just because it's already designed for cold molding.
     
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  9. JamesG123
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    JamesG123 Senior Member

    Thats a lot of sawdust!
     
  10. tomkcook
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    tomkcook Junior Member

    Thanks, that's interesting details and advice.

     
  11. fallguy
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    fallguy Senior Member

    Cold molding is a job for many hands.

    I have a cold molded hull still in service built in 1960.

    Mine was built using a team of six and they bag it and vac it an oven roast it. I believe the entire job is done in a day with vacuum bagging; sorry, don't know more, but if you can do all the gluing in a day; it might be worth researching.

    She needs a stem repair, but alas, I am getting a new hip first. Kinda funny when you think about it that way.

    I would avoid slow cold molding as a single builder and as well avoid a larger project.
     
  12. tomkcook
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    tomkcook Junior Member

    So what is the current wisdom on how best to amateur build a seaworthy, mid-to-large (40-50 foot) hull? The Buehler method works but cost a fortune at modern timber prices (and his designs are, erm, a bit reluctant to go to windward by some accounts). Cold moulding is a lot of work. Strip planking is expensive and wasteful.
     
  13. JamesG123
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    JamesG123 Senior Member

    ? So we've gone from 10' to 50'?

    The answer anywhichway is of course wood/foam sandwich core fiberglass composite.
     
  14. tomkcook
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    tomkcook Junior Member

    I did say it was practice for a bigger project!
     

  15. TANSL
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    TANSL Senior Member

    ... and, what is going to be the constructive system of this larger project? That would be the system with which you should practice.
     
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