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Has anyone built either a L Gato or La Chatte in welded aluminum?

With descriptions saying ' built using thin plywood sheet in a continuous piece between between keel to sheer' it would seem we should also be able to make it in welded AL.

Any opinions? Disadvantages?

Might 5052 .100 or .090 work without (much?) additional framing given the releatively small size of the hulls and the fact that they are 'completely closed eggshells'??

5086 .125 too heavy? Or a reasonable choice not needing any additional framing?

Any and all thoughts, suggestions, and opinions appreciated!

Chris

P.S. If feasible and reasonable, the aluminum La Chatte would be modified/used with two electric trolling motors - approx 1 HP into each motor, not as a sailboat, - and would be my 'inital build boat' before tackling a larger 18' - 20' ELCO-like electric cruiser, again all aluminum.

The`AL La Chatte would be used at displacement hull speed or less for fishing, swimming platform, and calm water cruising. An alternative to a 15' or so skiff I was earlier considering.

One MK Endura 34 for each hull, driven by a Penny+ Giles 4Q 24V 50A wheelchair controller with joystick 'skid steer'. This is 'V2.0' of an initial single MK 34 with PWM that got a lot of fun use this last summer on a Jon Boat. Ref: http://www.cfnet.net/tm

I built La Chatte in 1970 out of wood, this boat is not ment to be a displacement speed boat. In short it flys... If you are looking for twin hull design that is efficient at low speeds maybe this is not the best choice.

My 2cnts.

Carl

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Carl
If not now......When?
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cahudson42,

Hi Chris, both these small boats would build in welded aluminum if you could control the weld seam size as you welded. The issue is scaling the weld down to fit the material.

Aluminum expands and contracts based on the thickness of the sheet but the effects of heat transfer and weld distortion are not linear to thickness. You can reliably use 0.035" wire on 0.125" but even 0.030" is a serious challenge on 0.090" material. I say that after building lots of skiffs and welding for many hours, and working with employees and other welders on this exact topic.

I mentioned weld seam scale in this context because any comparison to wood suffers using the scale issue for comparison. Wood joins cold and smaller pieces are more easily formed, clamped and glued but thinner metal (below 0.125" 1/8") is increasingly harder to weld without distorting the material.

While these are some form of developable surfaces which implies they could be formed of metal, the real similarity stops there.

Both of these designs would build in metal- but I'd recommend someone to build in the 16' -20' range first- using 1/8" material before they dropped down to 0.100" or 0.090" as the skill required in welding is exponentially higher with each 0.01" you thin the material.

The area of the hulls where the problems will be most difficult are not the keel seam or the sheer where outside corner welds could be added with less difficulty. The real challenge will be adding the beams and interior framing which in this size will need to be added before the ama's are decked.

I realize that it might look as though a smaller, lighter scantling boat would be a good warm-up for a larger, thicker boat. As regards cutting, handling, holding and jigging? that is true. As far as welding the opposite is true.

I believe we could look at the current market to understand this more clearly. What major manufacture/builder offers a boat thinner than 0.125" that is welded? [none?] They would if they could, as welding is faster than riveting, cheaper in regard tooling or lack of jigs and less exacting by far. The main issue is welding tiny aluminum seams in sheet aluminum is a fully Olympic event - or needs robotics.

Sure some weld the 90 degree outside corner of the transom to the bottom or topsides but does that same model have welded chines? Or welded interior framing?

glad you're thinking about boats again, I still say just build the Lady of the Lake in 1/8" and she'll likely be clean and fair with less effort than a little sailing cat of thinner sheet.

cheers,

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Kevin Morin