Fixing to a hollow gunnel

Access shouldn't be a problem,rolling the boat over would mean I would have to do the job externally which would somewhat defeat the purpose,I appreciate your input on it,thanks.
PAR,
if I regard the gunnel as a box section,and cut a neat hole in one elevation,place in the timber reinforcing and epoxy it in,I could temporarily use "F"clamps to hold it until it sets.If the cutout piece will fit back in then I can use that,if not,epoxy it back and sand it down to the original lines.
I have used slate dust in the epoxy on the new transom on my other boat,it sets like rock,and it's tensile strength improves vastly.
The only slight setback with using slate dust is the working of it once set,normal tools barely touch it,so grinding,then sanding is really the only option.
What do you think?
V

 

Working with polyester boats, the usual mix is milled fibers, maybe a heavier bulking agent, like cotton flock, balloons or wood flour and silica to stiffen it up to the desired consistency. Stone dust will increase density, but decrease elongation. On the topsides of a poly build, you'll want the repair to remain seamless, so save the slate dust for repairing a ballast casting. It's a two step process, the structural filling portion, which holds the cutout piece and the reinforcement, then a cosmetic filling, with balloons, spheres, etc.

 

I can see what you mean,so keep the initial filler below the surface in order to use the cosmetic filler so that it can be feathered.
Thanks PAR
v

 

Bingo . . .

 

If your putting a pad in, and feather it (ie chamfer the block/ply) you can glass it in, over the top. This is often best done after bonding in place first, if the boat is right way up and the goo squeezing out...two stage it.
If gravity is helping you, then often it is possible to do the lot in one hit. Depends how well the piece will stay in place ie not slide about etc. If you do glass, it is better to seal the surface(s) of the reinforcement piece first to ensure it remains dry.

The gelcoat (show) face can be filled in fairly easily. If a flat area (or 2D curve) just masking tape the edges and pop the gelcoat flush with a cabinet scraper or good edge. then you only have a fraction of a mm to cut back.

Bit different to the Crownline I've just been working on....