Rebuilding the Aquasport Classic "flatback"
Bedding the transom core. The Transom core is Renicell E240 from DIAB, 2" thickness. The foam will is bedded in epoxy glue made from regular Marinepoxy and woodflour/silica
The cardboard template was used to cut the core, then we dry fit it
into the boat. The core was trimmed so that it fits flush against the
outside skin. This of course leaves gaps around the sides that will be
filled with epoxy before the inside glassing begins. It is VERY
important to avoid gaps between the core and the skins so make sure the
core fits flush. The idea in bedding your core is to apply even
pressure all around to squeeze out excess epoxy glue. Epoxy is a great
gap filler. Bonds are stronger when you do not squeeze out too much.
We used galvanized bolts to pull the core into the skin. The bolts are
spaced at 8". For a plywood core I would recommend more bolts (plywood
is much stiffer). Two of the bolts on the top/outside are facing
inward, this gives a place to "hang" the glued core, while the other
bolts are being put through facing out.
Dry fit and do a test run! We glued this transom (2 people) in less than 20 minutes from the first mixing of epoxy to the last tightening of the bolts. On this day it was at least 90 degrees, so you will not have much time even with a SLOW hardener.
We rolled a coat of unthickened epoxy onto the core and the inside skin before the glue was applied with the notched spreader. Glue was applied to both the core and the skin. The core was "hung" on the skin. Bolts were tightened beginning with the inside and working out. Any material squeezed out was removed.
TIPS:
Have multiple 1 quart mixing cups ready
One person does nothing but mix, the other mixes and spreads.
Store the epoxy in a refrigerator for a few hours before mixing to give a couple extra minutes
Pour, don't pump – pumping takes too long
Use a notched spreader – helps to apply the glue evenly and gives an escape for air
We mixed 5 pots of glue. Each pot was 15 oz of epoxy total (10 resin, 5 oz. hardener) and enough woodfour/silica to give us a nice non-sagging constancy. I estimate we put 3 quarts of glue total down and squeezed out 1 pint.
The new outside skin is tied into the hull by overlapping 12" up the sides and bottom. We could not have done this from the outside without a whole lot of grinding and fairing.
Also its nearly impossible to get 1708 to stay on a such an angle above vertical (transom angle) - it would just fall down. Unless we flipped the hull in which case it would work.
Mold removed...
