Hand Layup on 90 degree corners

General Composites Discussions Composites Talk
#1

Hey All,

I’ve scoured and scoured for a solution to this, but I’m not sure if there is one. Hand layup on outside 90 degree corners seems absolutely impossible to do. Is rounding over the edges the only solution to this problem? I’ve read that vacuum bagging/infusion sometimes won’t even help. I’m using 1.5oz CSM, but I’ve also tried 3/4oz and various weights in cloth, as well as poly and epoxy resins. Any advice? If rounding over corners is the only answer, then so be it, but I thought I would ask first. Thanks?

#2

if you’re not bagging, then likely you need to mix a little bit of resin and cabosil and apply it to both surfaces right next to the corner. Then laminate on top of this. If done right you wont get voids from the fiber bending around the corner

#3

This ^

Some loose short (4-6mm) chopped strand is also a good addition to fumed silica and resin to make a nice strong reinforcement ‘putty’. If you make it relatively thick, and then laminate directly onto it while still wet, then you should be able to laminate without any voids.

#4

We have molds that have two back to back 90’s that are separated by 5/8". To say that the lamination is tricky is a big understatement. What works for me is I laminate the skin coat of 3/4 oz mat on one side of the 90 so that it sticks up over the edge by 1/8" or so. Let that cure at least until the material is firm. Brush on some loose milled fiber/resin putty and then butt a second piece of mat up to the first. Wet with resin and roll out any air and let it cure. Once hard, you can sand in a radius to laminate over. You can use feathered mat for a couple of more layers and you can build up a decent radius that will accept full laminates (1.5 oz mat, biax, etc).

This process gets glass fiber as close to the corner as possible. The putty is just there to fill any small discrepancies in the gelcoat and small gaps where the second piece is butted in.

I hope that makes some sense. If not, post up questions if you want and I’ll try to clarify.