GRP strengthening question

[diver22]

I am in the process of fitting an outboard bracket to the transom of my boat for transporting it. I have made a stainless steel outer bracket and a wooden pad to attach it to internally. My question is how should i bond the wooden pad to the inside of the transom? Fibreglass or silkaflex?. Part of me says silkaflex as the plywood may move with moisture and fibreglass will not give whereas fibreglass will give a more rigid bond. Your thoughts gratefully appreciated.

 

[davidpbo]

I would say Sikaflex. I doubt you are relying on the bonding for any strength as presumably the outer bracket will be bolted through the transom and the wooden backing plate

Therefore its main function will be sealing and some elasticity would be desirable.

 

[oldsaltoz]

G'day Lockin,

I would avoid ply or any timber as a backing, it tends to get wet and fail. You could use aluminium or stainless steel, to spread the load use micro fibres and resin, this will cure fast and hard and even out the point loading.

Also remember to drill oversize holes and fill with same as above, then re drill to the required size, happy in the knowledge that you have no raw fibreglass strands exposed.

Hope this helps.

Avagoodweekend......

 

[davidbains]

If you coat the ply with a layer of epoxy and maybe glass tape, and place filler under it, the wood will last longer. If you just want to use sikaflex you could replace the uncovered wood with a nylon/polypropylene chopping board cut to size. This will never rot but you can't glass it either, so sikaflex will be fine.

 

[tangomoon]

Agree with this chap.

Chopping board is cheaper and quicker if that's what you prefer