HEY,
I see several layers of ''cloth'' 6&7, in the lay-up.....it has no place with g.p.resin (Polyester) its for epoxy use..
1 1/2 0z. mat and 18 oz. roving.....you can use 24 oz. roving ,but its a 'bear' to wet out without a wet out gun.....
3/4 '' x2 or 3 for transom....you DO NOT need marine plywood unless you choose to spend the extra money....
SOME boats like HURSTON Glasscraft and DOUBLE EAGLE(early models) had stringers totally incased in glass and often 2 units lay-up.....that's mat/roving/mat roving/mat.....
some are layed up cheaply...just a bit of glass going up a few inches on the stringers......
again,some were built with cardboard tubes cut longitudinally and 2 or 3 units of glass laid over .....works just fine....
when laying up ,a layer of 1 1/2 oz. glass,then your first piece of plywood (That has been flood coated with UNWAXED RESIN)
another sheet or pieces of 1 1/2 oz. mat,then another piece of plywood.......remember to drill ''squish holes '' to let excess resin SQUISH OUT. I used to drill them about 18''apart,all thru the plywood.(DO THAT BEFORE INSTALLING>
finally ,I drill holes thru back of transom thru plywood (Yes ,transom stern will need filling and paint/gelcoating )
and bolt all together ..to tighten everything up and gTt all the extra resin to run out......
I buy cheap galv 5/16 or 3/8'' cheap carriage bolts from any hardware store and C O A T THEM W E L L with paste wax.or you will never get them out .... again,i space them 18'' apart....once the resin is hard, remove the WELL WAXED BOLTS
by hand, knock down any high spots on the inside of new transom.....fill holes with EVERGLASS that can be bought at any auto parts store....its in a redish /purple can.....contains short strands of Kevlar.....then lay up the inside of youe new transom with a unit or 2 of glass,running up 6-10 inches up sides and floor......
only use WAX RESIN on last application of mat....if you are going to put gelcoat on ,then UNWAXED RESIN and wax in gelcoat. take your time..and take pictures of the job....incase you sell your boat.......glenn