Dinghy design

[Brands01]

Here are a few pictures of a little skiff that i designed for messing about on our local river, which is pretty protected.

Design parameters were ease of construction (stitch and glue), cheap, pretty, and able under sail or oar power.

I'd love to hear people's thoughts on the design.

http://www.boatdesign.net/gallery/data/500/nice_little_skiff_1.jpg

http://www.boatdesign.net/gallery/data/500/nice_little_skiff_2.jpg

http://www.boatdesign.net/gallery/data/500/nice_little_skiff_linespan.jpg

[JLIMA]

Looks similar to one I had a few years back, the one I had was a little less beamy and had less dead rise but otherwise were pretty similar. Mostly i rowed (used an antique pair of 8' oars very lovely, now on the wall of my workshop) but she handled very well with a 10hp out board but i never fitted her for sailing. I only used her as a tended for my old Penn Yan. I'm assuming she's about 10-13 feet long I'ma gonna level with you here, I don't understand metric very well. But from the pictures seems to be a not bad little boat, just a thought if you lessened the dead rise you would stiffen her up a bit, but it i don't know what you consider pretty protected. If it's anything like what i consider than you should be fine although for use under sail I would definitely say choose your rig wisely and rig her with a dagger board. Personally i like the look of the old Gaff rigged catboats but that's up to you.

[Easy Rider]

I like her a lot. But like JLIMA I don't think she's perfect. I'd leave the deadrise and reduce the rocker about 40%. And like JLIMA I'd like to see inches and feet. Brands, how do you make drawings like that of your skiff?

Easy Rider

[lewisboats]

freeship/delftship

I would say reduce the flare of your first chine and widen the bottom some. You are looking at a fairly tender boat with the bottom that narrow...almost like a vee although not quite. If my calcs are correct you have a 6 ft long boat with a max beam of 33" and the bottom is around 14" wide. You are going to have a hell of a time getting plywood to bend as much as that top plank forward is curved and twisted in the bow area. Do a right click and check on the developability after reducing the resolution to high or medium. This will give a good indication of how cheap you can go on your plywood. The red areas are stress and if too big you won't be able to bend it without breaking the plywood or doing something like soaking or steaming it.

[apex1]

The boat is 9´by 4´with some 8" draught. (when will you accept, the entire world is metric?)

As Lewisboat mentioned the bottom is too slender, that is a tippy junk.

[lewisboats]

OK...so I skipped a step in the calculating...you would too if a 110 lb (50 KILO!) dog was seriously attempting to get your attention!

[apex1]

Ja Steve, I would!
Though my Labrador / Dane mix was 74 kg (163.1404 lbs) and had a shoulder height of 72 cm (28.3465 in)

[lewisboats]

Sounds like my Ex....I didn't say that!
I hope you meant Chinese Junk rather than the other definition (quick return to topic!)

[apex1]

Sounds like my Ex....I didn't say that!


Could I possibly have that a bit less cryptic? Who, why, what sounds like your Ex?:confused:

[Brands01]

Great guys, thanks for the suggestions. I'll make some changes and repost the pics - along with some imperial dimensions :)

[lewisboats]

Could I possibly have that a bit less cryptic? Who, why, what sounds like your Ex?:confused:

Never mind...it wasn't on topic

[JLIMA]

These are just a thought to consider, similar to the one you posted. S&G construction 1/4" ply with a 1" thick transom. The bottom is wider and the look is similar just something to consider, although I'm sure I'm going to catch some flak from some around here for the design it's one that worked for me and after 6 years is still solid and hasn't killed me, capsized or misbehaved with use in the chop of Buzzards Bay. Just something to consider.
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[JLIMA]

Also I put it in metric for you. Yes even I can learn something new.

[nordvindcrew]

I like your design a lot. I also think you should get rid of a lot of the rocker in the bottom. The flaring garboard panels along with the flare in the rest of the hull will provide a lot of reserve bouyancy. Can't comment on a sail rig, but it should be possible if a daggerboard is added and the rig is kept small and low. Good luck!

[Brands01]

Here is a revised version.

I've taken on board all the comments. This version has about 30% - 40% less rocker, a wider bottom panel, and I've removed a tiny bit of flare. You can see from the developability picture that there shouldn't be any problem getting the plywood to meet any of the curves.

I've also added about a foot (since when did anyone designing a boat go back to the drawing board and not add any length?), so its now close to 10ft.

AND ... I've even put it in imperial!

Barney

http://www.boatdesign.net/gallery/data/500/medium/nice_little_skiff_10_linespan2.jpg

http://www.boatdesign.net/gallery/data/500/medium/nice_little_skiff_10_linespan.jpg

http://www.boatdesign.net/gallery/data/500/medium/nice_little_skiff_10_developability.jpg

http://www.boatdesign.net/gallery/data/500/medium/nice_little_skiff_10_2.jpg

http://www.boatdesign.net/gallery/data/500/medium/nice_little_skiff_10_1.jpg

[Brands01]

Links to linespans so you can see the dimensions:

http://www.boatdesign.net/gallery/data/500/nice_little_skiff_10_linespan2.jpg

http://www.boatdesign.net/gallery/data/500/nice_little_skiff_10_linespan.jpg

[lewisboats]

That's looking really nice there. You have initial stability and reserve stability now in good measure for both. I am a little concerned about the hollows at the bow in the bilge panel...freeship might say it is developable but my personal experience with plywood is that it tends to go convex rather than concave in such conditions. It isn't a big thing...it is simply that you might not end up with that exact shape when things go 3d.