bilbo wrote:Thanks GreenLake. Did you let the patch cure out before applying it to the hull? The way I'm envisioning the backing plate, if needed, is to pull it up against the back (inside) of the hull with something. Then lay wet glass on it so it's supported and allow to cure in place. Last, remove the bracing/support system.
On a DSII where you can't access the inside of the hull, anything you put behind the repair will remain in place. That's why you use something like the thin (!) plate made from laminate. It's OK to glue that to the inside of the hull. You can then remove whatever you used to hold it while the glue (epoxy) sets. You then laminate over that from the outside. The patch on the inside supports the wet laminate, but also adds a bit of strength, which is a bonus though not strictly needed.
Because not strictly needed for strength, you can keep it thin and a bit flexible, just strong enough to ensure the edges of your gap are aligned, and you'll get a fair curve in your hull when you are done. Because you'll be gluing your backing plate, you can (and should) remove whatever you used to pull it against the hull before you add the laminate on the hull side. (In your case, that support is on the outside, so it would be in the way if you tried to laminate with it in place).
If you let the plate cure all the way before gluing in place, you need to sand it rough before gluing. You also need to reach in and sand the inside edges of hull so you get a good bond.
In my case there was some tension in the hull that pulled the edges of the crack out of plane very badly. I had to make the plate stiff enough to counteract that. I suggest you make a small sample to check your layup schedule for the backing plate; don't just use whatever I wrote in my other post.
You will sometimes read about laminating over something that's still in the "green" stage of curing. That will give you a better bond, but as you are gluing to the hull anyway which is a different resin and long cured, that's not something to worry about. Any surfaces that are not "green" epoxy need to be sanded before laminating. If you don't use a "blush free" epoxy, you may need to wash (water) the surface to remove amine blush before sanding.