Wet Lay-up Pictorial (Mast Thwart)

I've previously mentioned this technique in some detail, but if you're like me, a few pictures get the message across much better than words, so here goes a run-through of the most recent job - fitting the mast thwart.

Mast thwart frames dry fitted

The screw holes in the edges of the frames need to be centred to avoid splitting the ply, and VERY IMPORTANT THIS: countersink them - makes it a doddle to get the screws in the right place when you're doing the final lay-up/assembly wearing gloves, everything covered in thick sticky epoxy, and fighting the resin's 'curing window'. 

The wonky thwart frame on the left, and the voids in the plywood edges indicate the very poor quality of the 12mm plywood I'm using for the frames (should be 15mm, but my supplier didn't have any). Needless to say, the price I paid did not reflect the poor quality...

OK, enough of the moaning; it's gotta get built, right?

Strips of glass tape cut ready

 So, one strip of glass tape goes behind each thwart frame edge (against the sides), then one goes each side of each thwart frame edge, over the epoxy fillets. 12 strips in total. At this point I'm well into my second 50 metre roll of glass tape!

Thwart frames and seat (with alignment cleats glued on)
ready for epoxy priming

 Because of the crazy twists in the 12mm ply, I decided to orientate them so that they bent towards each other. By fitting some thin cleats 12mm in from each edge of the seat, the seat would be held firmly in place, and straighten up the thwart frames at the same time. It would have worked perfectly if the bends in the plywood only went in one direction...

Thwart frames and seat primed on all edges and faces
(that's why you need gloves!)

Glass tape applied to side panels

Next a strip of glass tape was epoxied in place on the side panels behind each of the four thwart frame mounting points - I've done the same with all frames attached to the sides and bottom of the punt as reinforcement/load spreading.

Then thickened epoxy was spread on the (primed) ends of the thwart frames, and each one was positioned and screwed in place (by hand - power driving is too brutal, and I don't want epoxy all over my nice cordless drill handle/trigger).

Thwart frames in place over glass tape

Thickened epoxy fillets were then spread along front and back edges of each joint - easy without the seat in place.

Glass tape epoxied over fillets

Glass tape was then epoxied over each fillet (both sides), and spare resin used, as always, to seal any bare plywood nearby.

Mast thwart seat epoxied in place (thickened epoxy)

Nearly there - I spread thickened epoxy along the underside edges of the seat and popped it in place. Finally, a fillet of thickened epoxy was run along the ends of the seat where it joins the sides.

Time to fire up the barbecue and crack open a beer or several methinks...