Shetland 460. Rotten transom and waterlogged foam under deck.

[TheMarketMech]

Hi all, I'm new to the site. I've just bought a shetland 460, plate number 263. I knew it needed work prior to buying and I want to get my hands dirty. As per title the transom is rotten, and the buoyancy foam under the deck is soaking wet. Ive started to remove the transom. The box part of the transom is 18mm marine ply which I don't think I'll have too much of a problem with. The wood glassed in at the hull (where outboard clamps too), measures 27mm thickness. So I thought maybe to replace that by using 3 x 9mm marine plywood to glass in? As from what I've researched, multiple layers of ply are better than one thick piece.

My main concern is the deck and where to cut and how to go about repairing it... do i use foam and replace like for like? Or do I go down the play pit ball/empty plastic bottle route? Where do I cut? Do I reuse the original deck or am I completely glassing in some marine ply? I've attached a picture showing the deck, transom is already removed. Thanks. Chris.

 

[PCUK]

Your pictures won't appear until you have made a few more posts. To repair the deck, cut the top section off and remove al the old rotten foam. Replace the foam with ply of the appropriate thickness. Slice 2/3rds through the face of the ply using a plunge saw to make it flexible them gle=ass it in using thickened epoxy and then refit the top deck section using more thickened epoxy. Fill and fair and finish the deck in whatever style you prefer,

 

[Refueler]

Transom - you seem to have that covered well. I would suggest alloy or plastic plates as used on dinghys for the outboard mounting screws to press onto instead of just ply.

Deck ... IMHO this depends on the bottom layer of GRP .. if that's in good condition then I do not see that it needs the extra weight of all ply replacing the foam. As PCUK says - carefully cut away the original deck as cleanly as possible. Lift away and clean off all the crap foam stuck to it. Try get it as clean as possible - rotary sander is good.
The wet foam needs to be removed and again cleaned up - right into corners / sides etc. Try get that as clean as possible ...
But to avoid adding too much weight - personally if all still good - I would get sheets of closed cell foam insulation - generally used on floors / walls before final laminate etc. Instead of cutting whole area sheet - I would cut the area up into sections, create ply vertical support bulkheads to carry the deck joint and intervals of the deck and epoxy into position ... with epoxy between joints of pieces to ply etc as well .. building up the foam depth.
The ply vertical bulkheads with epoxy laminating and joints will add a small amount of stiffness to the already stiff foam sheet.
Once infill is at level and ready for top GRP to go back ... a generous coat of epoxy over the foam / ply and apply the GRP deck back ... Suitable weights applied to make sure it conforms to deck shape.

 

[PCUK]

All good info', the reason I use ply is to ensure the strength of the deck is at least as strong as it was originally but closed cell foam will do the job and probably be easier.

 

[Refueler]

All good info', the reason I use ply is to ensure the strength of the deck is at least as strong as it was originally but closed cell foam will do the job and probably be easier.

Its not a big boat and I was just thinking of each KG added ...

 

[PCUK]

Good point.