Originally Posted by andreas.mehlin
Problem is getting it here in Mexico
foam sheet from the states down here is sort of impractical.
How about strip planking and coating each strip with epoxy? Water
shouldn't be any issues at least?
You could try and find a door with a cardboard honeycomb core.
Strip the skins and remove the core.
The following steps describe how to make ghetto Nomex.
The honeycomb will be too coarse to take the compression
loads encountered on the trailing edge of a rudder.
Cut the core to the shape of your project
with a box knife.
Test fit - it will be nice and flexible.
Cut somewhat circular plugs from the excess core and spiral them into alternate holes in the core as a test fit.
Remove the plugs.
Apply a slurry of thickened epoxy (glue ) to the work
area on the rudder.
Allow epoxy to get sticky.
Apply honeycomb to rudder.
Use masking tape to hold in place.
Allow epoxy to set - no need to wait for cure.
Spray coat of epoxy over and into the honeycomb.
Insert plugs whilst epoxy is wet
Spray another coat of epoxy over the combined core material.
Allow to set
Clean up knock off and have a beer
while the sun goes down.
Fair to final shape.
Cut a layer of non emulsion Chopped Strand Mat to fit.
Wet out the CSM and allow to gel (sticky)
Apply CSM to work
Allow to set (not cure)
Apply thickened epoxy (glue) to CSM
Allow to Gel
Apply on a layer of laminating resin.
Apply bi directional cloth , roll , add resin
Allow to gel
Job done by beer
thirty on day two ready for final sand barrier coat and antifoul on the same schedule as the rest of the hull/appendages.
Best not to use 5:1 or 7:1 resins.
4:1 is OK but 2:1 is best for non blush formulations that allow the work flow to continue without curing and sanding
If you are stuck with a blushing resin (West?) brown vinegar will remove the blush at any stage from gel to cure without sanding
Strip planking would take me 3-4 days.
Expanding foam about a day and a half.