Cheap, easy, fast homebuild

[TimClark]

I was messing around with some ideas for a possible senior project for next year, and I decided to get on with doing a homebuild high performance (relative term) dinghy that could be singlehanded in the lighter stuff and doublehanded when it starts to blow. I decided that I would want the build to be as easy, and cheap as possible due to the fact that I'm a high school student without a license, aka I have no way of getting to a job so I have a very small cash inflow for now. So, the build would be stitch and glue, out of stressed ply. Rig would be from a 420 so I don't have to go out and build or buy something. When singlehanding the boat, you would basically be on the trap most of the time, and doublehanding trapping wouldn't be needed until it kicks up a bit more. If you have any questions, comments or suggestions just throw them down. Thanks.

TC

[TimClark]

Basic Dimensions:

Length: 14 ft
Beam: 4.2 ft
Designed hull weight: 110-120 lbs
Volume Displaced(with singlehanded crew of 200 lbs): 4.99 ft^3
Wetted Surface area: 27.03 ft^2

Obviously by going with the chines/stitch and glue construction I am going to have a higher wetted surfaced area than if I did plank construction and no chines. However, I think the benefit of weight saved by doing stitch&glue with stressed ply strongly outweighs the advantages of having no chines and a heavier hull.

TC

[Petros]

Tim,

I built something similar out of salvaged lumber and materials last summer. Total out-of-pocket cost was about $35 complete. This includes the laminated wood mast, rigging, sails and rudder. The stitch-and-glue construction you are proposing I think is more work and more expensive than my method of skin-on-frame construction. It is built like a large kayak, but shaped like a sail boat, 14' LOA x 4.75' beam. The total weight is only about 180 lbs or so (hull weight alone is about 90 lbs). It comes up on plane real easy because it is so light.

The hard chine does not harm the speed as much as you think, yes there is slightly higher wetted area, but not a lot. And the hard chines help it come up on plane easier too. Skin-on-frame is lighter, faster to build, and uses less material (hence less expensive) than just about any other construction method. It was a fun project to build, and it came together pretty fast, perhaps 250 hours total including the sails. The only materials I had to buy was the waterproof glue, the deck screws, and a few other bits of hardware.

Below is a pic of my daughter and I out in it on first launch near Port Townsend WA, and a few construction photos. It uses Tyvek sails, doug-fir stringers with steam bent white oak ribs, a laminated fir mast, and laminated pine dagger board and rudder. The hull is held together with lashings and plated deck screws. I used a heavy plastic skin, eventually I will replace the plastic with about $50 worth of heavy polyester fabric sealed with a polyurethane finish.

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First launch! August 2007; Pt. Townsend WA
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Frame assembly, besides table saw and planer, hand tools in picture is mostly what was used to assemble hull. Friend Floyd pictured assisting in the construction.
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Test fit of sail and rigging, skin held on by coaming and heat-shrink to fit, shown before floor boards installed. The mast is stepped on the forward part of the dagger board box.

[gggGuest]

Originally Posted by TimClark

If you have any questions, comments or suggestions just throw them down.

I'd avoid the hollows in the waterlines forward if I were you. Best practice seems to be to have the waterlines at the entry straight or a very slightly convex curve. Difficult to be sure without more dimensions, but for a fast singlehander with a 420 rig I think I'd go narrower across the chines to avoid getting too sticky.

[TimClark]

Originally Posted by gggGuest

I'd avoid the hollows in the waterlines forward if I were you. Best practice seems to be to have the waterlines at the entry straight or a very slightly convex curve. Difficult to be sure without more dimensions, but for a fast singlehander with a 420 rig I think I'd go narrower across the chines to avoid getting too sticky.

I fixed the forward waterlines like you said, I agree that the hollows definitely were not right with this. I altered it to a straight entry, if you would like a screenshot let me know. The max beam on waterline is around 2.9 ft, so I was thinking that it would be fine how it is considering the fact that I'm accounting for a 200 lb person when really I'm only 160 soaking wet. If I was sailing the boat, the chines would be out of the water, and the beam on waterline would be around 2.8 ft.

TC