Transom Foam

I am looking for replacement for plywood in my boat. Anyone have any suggestions? I want to use a foam core for the transom, but I am not a huge fan of the fibreglass reinforcements in the coosa board. I found this PVC board on Amazon, which looks good. http://www.amazon.com/CoreLite-Board-thick-48-96/dp/B01FN3VHVO/ref=sr_1_1?ie=UTF8&qid=1463602895&sr=8-1&keywords=corelite

Has anyone used this before?

 

PVC on its own lacks strength. I built a boat once with PVC foam cored GRP sandwich transom, the only concern is compression of the core from tightening bolts that secure the outboard, that was easily fixed with a thick marine ply pad under the engine bracket, and very large "washers" on the inside. Never had a problem. Naturally there was enough glass in it to supply the strength needed, much more than you'd have with ply.

 

Don't forget the structure must support the thrust from the motor to the hull properly. By this I mean across the transom to the sides and bottom of the hull or it might decide to crack somewhere towards the edges.

It will also depend how much horsepower your looking at transferring, you don't say so could be 4, 40, or 140?

I quite like using an alloy bent plate or right angle wide extrusion (modified) on the top of the transom, local to the engine mount bracket. This acts as a scuff plate and support, on the inside for the upper bolts, especially if thicker than 2mm. You need support for compression, as Mr E wisely points out, so you can use end grain soild timber as well as ply. Both should be sealed prior to encapsulating in glass. This should spread reasonably to progressively support the thrust and take the local bolt pressures. Best if you do use ply/timber to drill the mount holes oversize, fill with epoxy and microfibres and then redrill through that at correct size. Assuming 12mm bolts say drill at 15/16m first, then seal the core, redrill at 12 and your done. Fat 'penny' washers should be used and tapered custom washers as well IF the hull is curved on the inside face.

 

What is it that concerns you about Coosa Board, I sell it to several customers that use it in transoms, they've used it for years without any problems.

 

Cossa does make a good transom core material, once you get over the cost.

 

I would look at using SpaceAge Thermo-Lite Board. It is similar to Coosa in terms of the foam and fiberglass but much better quality, consistency and service.

 

Really, you've joined today and dropped 6 nearly identical plugs for "Thermo-Lite", but the site has no real data other than it being a 9 pound urethane foam. How about some pricing compaired to similar core products. Lastly, how can you compare a foam core product with Coosa?

 

Coosa is great for Transoms!