Problem cutting epoxy laminated part

[leaky]

I got busy, let a pile of panels cure in the tent. Then got back to it.

So an update here. Although I very well may not choose the best cutting tools, it's more complicated. This is why I've been so perplexed.

The delamination is due to a problem between the top layer of fiberglass and my finish coat of epoxy. What issue, I gotta assume is a rule with the bonding window I broke..

This is system 3 Silvertip with fast hardener, they state 72 hours at 70 F no-sand recoat times. I generally keep it to 24 hours or less, else I prep, but maybe I did something one afternoon, came back the following night, and meanwhile all day it was 80 F in the tent with high humidity and it took it to full cure with a blush or something.

If this wasn't a bolt down panel I'd probably scrap it, but instead am able to chip away the top coat. I'll then prep and recoat to fill the weave in again.

Really weird to me. Not a pro but done this a good 30 times with the same and similar epoxy, never such a problem. Wouldn't even expect such a thing if I'd let parts sit a week and then coated. Isn't as bad as if it had a mold release but as you can see the bond is pretty lame.

I guess my new policy, sand if you can sand. Always.

 

[leaky]

Oh and also worth mentioning, problem is only one side.

 

[fallguy]

So, sanding will not remove blush. Be warned. Blush in Silvertip is almost an absolute uncertainty. Can it? Sure. Likely, no. I have 300+ gallons of experience with it and it blushed NEVER.

But, the bond window of 72 hours is; quite frankly, a stretch. I offer mt experiences here to avoid litigious problems. And as a Silvertip user; my cat has 1.5 gallons of another brand. I like it!

I have sanded thru, for change purposes, a coating of clear epoxy on other epoxy within the bond window and if feathers off.

But why?

To be fair to Systems 3, a lot of dirt can fall on a part overnite. You may have been mixing fumed silica or simply had the door open and dirt settles on the part. But I think sheen is the real major culprit. When I see a hard shine; I never trust the bond window. Anything not green on, I sand next day.

Yesterday, I bonded bulkheads (16) into the BBs and did NOT have time to get the tapes on. They will all be sanded and I hate sanding fillets.

Anyhow, sheen is bad. 72 hours is not at 80F.

all the best

 

[leaky]

So, sanding will not remove blush. Be warned. Blush in Silvertip is almost an absolute uncertainty. Can it? Sure. Likely, no. I have 300+ gallons of experience with it and it blushed NEVER.

But, the bond window of 72 hours is; quite frankly, a stretch. I offer mt experiences here to avoid litigious problems. And as a Silvertip user; my cat has 1.5 gallons of another brand. I like it!

I have sanded thru, for change purposes, a coating of clear epoxy on other epoxy within the bond window and if feathers off.

But why?

To be fair to Systems 3, a lot of dirt can fall on a part overnite. You may have been mixing fumed silica or simply had the door open and dirt settles on the part. But I think sheen is the real major culprit. When I see a hard shine; I never trust the bond window. Anything not green on, I sand next day.

Yesterday, I bonded bulkheads (16) into the BBs and did NOT have time to get the tapes on. They will all be sanded and I hate sanding fillets.

Anyhow, sheen is bad. 72 hours is not at 80F.

all the best

Yeah I don't know. Dirt, around here, nah - too wet practically always outside (NH).

What's odd is I don't think there's any way I went 36 hours even.

Shiny surface - must have been. However it went that cured, that quick, never gonna be quite sure. But moving forward, gonna be looking at this harder and doing some sanding if there's a question.

I did chip 90% of that stuff off. Rest got a 40 grit, was bonded from those results, but I cut through it anyway.

 

[groper]

firstly - get some heat onto your panels to cure them properly .

Second,
A Circular saw running a “metal cold cutting blade” is a wet dream if you’ve never tried it . It cuts fiberglass panels like a circular saw thru balsa wood…

the metal cold cutting wheels are designed to cut thru solid steel - the teeth are closer together than a timber blade , and the teeth are made from a very hard material that lasts. These blades are very expensive at about $100usd each for a 7in circular saw blade , but they last forever and cut very fast with minimal dust- you’ll have lots of very small chips rather than airborne dust.
And lastly - set the circular saw up so thr depth of cut is only just deeper than your material - this way the teeth are not cuttting at 90deg to the laminate -like thr jig saw does