8 ft. minimost hydroplane

[Dave Gallaher]

Starting to gather supplies to build a minimost hydroplane and the plan says 1/4 or 3/8 in plywood. I am guessing I should go with 3/8 for the strength. Any ideas on exterior finish? If anybody has any suggestions before I get stared I would love to hear them.

[Keith Outten]

Dave,

When I was a kid 50 years ago a friend of mine had a hydroplane his Dad built for him that was a similar design. His Dad used 1/4" plywood and filled the 4" sides and the bow with foam so the boat was unsinkable. Two of us could pick up the boat and carry it down to the river without the motor of course. The boat was designed for his 12 hp outboard, on occasion my friend would borrow his Aunt's 25 hp motor and we would fly. The boat would do insane speeds, once it was planing we could steer it by simply leaning from side to side. It had a small aluminum fin on the bottom.

[Dave Gallaher]

Thanks a lot for the information it is really helpful

[Mac McQuinn]

I believe this is an older design that did not use the epoxy encapsulation process. In that case I think I would lean towards 3/8" ply since ply isn't the same as when this boat was designed. If you decide to encapsulate the boat, then I'd go with 1/4", Marine if available or affordable. As far as interior finish, I would seal all joints/corners with epoxy/wood flour fillets, covered by a layer of FG cloth and epoxy followed by a light colored coat or two of paint. This should alleviate any possibility of trapped water doing damage. Sponge out after running.

I remember this type of boat racing on the Saginaw River in Michigan back in the mid 1960's, lot's of fun for the buck.
Good luck,
Mac


Starting to gather supplies to build a minimost hydroplane and the plan says 1/4 or 3/8 in plywood. I am guessing I should go with 3/8 for the strength. Any ideas on exterior finish? If anybody has any suggestions before I get stared I would love to hear them.

[Dave Gallaher]

Thanks Mac.

[Chris Damm]

My dad and I built a Mini-max boat back in the early 60s. The plans were from Mechanics Illustrated magazine. We used 1/4" marine plywood and a good marine spar varnish. The quality of plywood was much better than what you can get today. The boat was designed to be used with a small outboard. We had a mid 50s 10 HP Mercury with a Quicksilver lower unit and the boat would flat out fly. It was great when the lake would lay down at dusk but if there was a lot of wave action it was a thrill ride! I outgrew the boat and my dad was afraid my little brother would get hurt so we sold it and bought a ski boat. I've often thought about building another one but at 6'4" and 300# it wouldn't be practicable.

[Dave Gallaher]

That's awesome Chris

[Jack Battersby]

Hey Dave, in order to build that boat you need to split the bottom and put a small curve in the cut and then pull the two sides together. That process is much simpler to do with 1/4" than it is with the 3/8". The original plans most definitely called for 1/4" on the bottom and top with 3/8" on the transom. That boat is well framed out so 3/8" would be a bit of overkill unless you plan on riding her up on the rocks.

I built one 40 years ago and yep, I tried a 25 hp engine on it. Scared the life out of me. Had to wear goggles because my eyes watered so badly. You may want to consider a little glass on the underside just for abrasion resistance.

[Dave Gallaher]

Thanks a lot. It would be smart to use 3/8 on the transom and 1/4 on the bottom.