foam core versus wood core

Hello evryone, I am currently a student at The Landing School in Maine and we are just starting our own personal projects. I am replacing the transom in my cvx 16. Before i go to my teacher with my plans i would like to get your thoughts on core versus wood, just so i can argue my point if needed. He is a great teacher and wont lead me astray i just like to have ammo just reaching out for suggestions.

 

Foam core is a poor choice for a transom. That may not help your argument. Use plywood for strength. Use epoxy to encapsulate the plywood. Properly done, the transom will outlast the rest of the boat.

 

Thank you for your time it is appreciated, going down now to give him my proposal

 

Yes you can make a tramsom with only using a small amount of wood !!!
Foam or balsa can be used in a transom to make it light and strong but its a whole transom thing you need to look at Plywood in the middle where a motor is mounted with through bolts and clamps etc etc and a shamffered edge and glassed over then outside that use strong H80 or higher density foam then shape to fit so it can also be totally encapsulated with glass , use double bias and unidirectional glass . Its much lighter than a whole plywood and glass transom and way stronger and will last a long long time !!

If you introduce shape into a transode designe then you can vertually completely eliminate using core at all and just have plywood where the motor mounts and the rest can be 100% glass !! . If you have a flat panel its floppy but introduce shape and it not floppy any more !! the more shape the stronger it becomes and all you are adding is shape and still has the same weight !!
Every one is locked into it must have a core thing we its dosent!!Do you see core oin car doors ? how does a car door get it strength ?? shape !!!
Shape = strength without the introduction of extra weight !!! with those thoughts see what you can come up with . I will try to find a picture i have of a transom that has only plywood where the motor is mounter the rest is glass only

 

restoration

My before , during and finished project !!
This what i made all from glass on my work bench and then chopped the old transom off and got rid of the water soaked wood and terrible grubby glass .
I stepped the out board 450 mm out the back and made the splash well much smaller and because the outboard is a 25 inch its very dry boat . Its my fast fishing boat ! a lot of fun to drive and handles really good !Jumps clear out of the water like a jet skii when you take of quickly !
The boat is 1975 and the hull is totally glass with no wooden floors or frames any where just one square of ply where the motor is mounted and bolted through !!, i used shape to give strength !!
I have made a few other transoms and simply used the same concept and they all worked really great !!

 

Tunnels, I agree that plywood is not necessarily required throughout the whole transom, only in the area of the motor mount. However, I disagree that foam cored glass is way stronger than plywood as you suggested. I would argue that plywood is just as strong if both methods are properly done. The foam cored job will be stiffer because it concentrates tensile and compressive loads on its skin and plywood carries the same loads throughout its thickness.
Wood can rot, it's true, but not when the job is properly done. A lot of manufacturers built boats with plywood transoms that were poorly sealed (polyester resin is not water-proof like epoxy, the preferred repair resin).

 

You are right !! IM just a bit of a stick in the mud and like to make glass boat out of glass . Wood always gets wet and will rot eventually . wood gets heavy as well and a very high percentage of glass wood glass transoms the glass is not even stuck to the wood any more !!
I was foreman of a small power boat manufacure for a while saw all what goes on an was a part of it all . The junky ply that gets use is criminal in some boats just because it sprayed with resin they think its sealled but its not after a few years its just the glass that holding everything together the ply has disintergrated and is just rubbish !!

 

Wood is lighter than glass. If your mounting a high HP engines, wood is you best weight option. But agree it has to be done right. Use only marine plywood in layers , with plenty of epoxy,and cross bracing. I rebuild transoms on high Hp fishing boats and sportfish. Trust me everyone wants to get rid of wood, but when I explain the difference in price and weight, the composite wins.

 

End grain balsa has been used successfully on transoms of smaller boats. The core is in compression so foam can work well too, particularly something like Coosa board.

 

This is a great conversation and i am enjoying and considering all of your replies. Thank you all for your input!

 

EVERY material has advantages over others theres a list of glasses and resins as long as your arm !!,same with timber and ply theres a list of timbers that are excellent and some you shouldnt touch !!,choose carefully and do your research and home work properly before comitting yourself to any thing reguardless what it is !!:idea::?:

 

Coosa board is used as the core in transoms by several builders in Maine, including transoms of boats with large outboards. My understanding is it's considered superior to plywood since it doesn't rot.