JEM Watercraft

Hello Builders,

I am working on a small power dingy suitable for one or two persons. I would very much like comments or ideas for the design at this preliminary stage.

Main dimensions for the dingy is:
L.O.A = 3,760 m (12’4”)
B = 1,280 m (4’2”)
D = 0,608 m (2’)

At a displacement of 400 kg (882 lbs.) it will have a draft of 0,176 m (7”)

The whole idea with this boat is that it has to be very simple to build. Should handle well with an outboard engine and have the ability to carry the weight of batteries if an electric engine installation is preferred.

Keeping the beam relative small the boat can be constructed only with transverse supports. One thing that is difficult to handle when building is longitudinal stringers. Therefore I have tried to avoid them. If however someone would like to have a larger outboard it will always be possible to apply longitudinal stiffeners as inserts between the transverse frames.

The boat is high. This gives the advantage of good stability and god loading capacity. Furthermore it gives a dry ride if someone choose to go off sheltered waters. The height also has some disadvantages. I would not suspect the boat to handle very well by oars.

Nice looking Garvey-type design.

What size engine are you designing for without any longitudinal stringers?

I would recon that a 5 hp 4-stroke would be fine with no stringers and according to my calculations the boat will be able to go 8 kn.

Nesting almost ready. This nice little Garvey will only need 4 sheets of 9 mm (3/8") and 2 sheets of 12 mm (1/2") plywood. I'll properly need a prototype builder for this one. Further notice will come.

The construction is going well . Need to measure up some detail drawing for the dingy. Please have a look at the pictures below.

that's looking great!

Plans ready for the new design. Called 12' Garvey flex:

viewtopic.php?t=82

http://www.boatplans.dk/mo-gf12.asp

Very interested in your dingy for use on sheltered waters where wind can whip up 1 foot waves with wind/tide direction. Require this craft to be relatively light since it would have to be carried/transported over about .5 km. over wetlands to get it to the water for fishing. I feel that max. power be 5 hp. outboard but that 2.5 - 3hp. would suffice.
Need more information on construction details ASAP - wood construction in any form for me would be no problem as I am a cabinet maker by profession.
Need to start on this boat as soon as possible since I will have time in the next month to build this boat & the fishing is at it's best here at this time of the year in my part of S.Africa.
Regards,
Tony Prince

How will you carry it? A cart of sorts? They make tranport carts like this for canoes and kayaks with wide tire to keep from digging into sand.

I bet you could easily rig up something similar for this boat.

The scantlings for the 12’ Garvey flex is calculated in accordance with the CE-regulations for small crafts. The regulations is only valid here in Europe, so when you build the boat yourself or live outside Europe you don't have to care about that, but it gives you the safety that the boat you are about to build, comply with a high standard.

The weight will be app. 60 kg (132 lbs.) depending on the weight of the plywood you choose. This weight will be as it is, i.e. without making any constructional changes. It will be possible to cut somewhere between 3-5 kg off the weight by making lightening holes in the frames. There will be further optimizing possibilities if you prefer to have a even lighter boat but they will all cost you something. I have calculated the costs for plywood, epoxy, fibre glass and filler to be less than USD 400 in the US (this price is without paint, hardware, oar locks if rowed, rub rail etc.). If you choose to make your boat lighter the price will be higher, so it is simply a question of how much you are willing to offer.

The weight for the boat will properly be too much for one person to carry 0.5 km. So Matt’s suggestion about a cart will be a solution. Otherwise maybe some kind of runners installed would make the job easier.

I have made some calculations regarding the outboard engine size you suggest. With a 2.5 hp outboard engine you will be able to go somewhere between 5 and 5.5 kn. So if that’s a sufficient speed for you there is no need for a larger outboard engine.