It was a total disaster. I’d read the posts that talked about the dangers of warping so I did what I’d read others had done and I used spray glue to apply the chop matt to the top half of SC pack the other day and then today I worked with a brush to apply thin coats of resin. The first problem I had was that the resin literally tore the chop matt apart. And it wasn’t so much that it was lifting entire pieces of matt away from the glue, it was more like it was just tearing chunks of it out like hair in someone’s fist. After trying repeatedly to stop the brush from tearing away the matt without success I stopped and switched to the bottom half of the pack where I did not pre-glue the chop matt (anticipating that it might not work and so not wanting to put all my money on one horse). There I tried the traditional method of applying some resin, laying the matt, rinse repeat.This method was certainly less messy but felt more risky to me. After finishing maybe 30% of the bottom I flipped the pack over to see what was going on in the front and sure enough there was swelling and warping everywhere. Strangely enough the top half where I had pre-glued instead has much more warping then the bottom. I’m really pretty upset about it, an 80-something dollar pack now looks like it’s stuffed for Thanksgiving, but I had always told myself that there was a risk in trying this so I was kinda prepared for this I guess. Lesson learned I suppose 
Chin up buddy. Really sorry to hear this
Sorry to hear about you misfortune. Are people really taking SC shells and applying fiberglass resin into the inside? IIRC SC packs are vacuum formed styrene. Resin will most certainly eat away/ swell styrene. That warping you see is from heat and the resin eating away at the plastic. Do you have a link to the thread someone suggested doing this?
This is distressing. Is there another way to reinforce the inside of an SC Shsell? Member Alan Hawkins has advocated the fiberglass method with success.
If you work with the resin lightly and glass in single layers, you might have better luck. Instead os using glue and then laying your mat on that, apply a thin layer of resin instead of glue. Lay your matt into that, then with a bit of resin in the brush, dab the brush into the matt to get resin into both sides of the matt layer. So long as you use a minimal amount of resin, the heat won’t be so bad. But styrene isn’t very durable to heat, so I could still see some warpage occuring. The big thing is don’t slather a ton of resin or lay on multiple layers of mat simultaneously. That increases the heat given of during the cure process. Practice on some spare flat sheets.
Sorry to hear about your project. I did the same method to mine, without the unfortunate results. This is the cloth I used.
http://www.lowes.com/pd_331525-98-20128_0__?productId=3228210
It frayed and came apart a little, but not so much that it destroyed the cloth.
I should add that Alan has reinforced two of these SC shells in the exact same way, and we’ve had no problems. Wish I could be of more help. Sorry, Zeke.
I should mention I use Bondo resin available at Lowes, but I use a chop mat from Evercoat that I purchase in 8 sq yard chunks from my local auto body supply shop. The mat is a light, loosely woven type that frays easy, but the resin can soak into it easier and more thoroughly.
I fiberglass end the inside of my shell and had no problems. Made my shelluch stronger. Very sorry to hear about your misfortune. You could try using spray foam. Not sure how well it will work but it’s an idea.
Yikes! This sounds like a chemical reaction running hot. How much hardener did you use per ounce?
I’m sorry to hear this happened.
Thanks everyone for your sympathies. 
Given a day to process it I’ve come to 3 conclusions:
1. IMO don’t ever, ever, ever use fiberglass unless you are 100% familiar with it. I think that to use it on an SC shell requires lightening the mixture or something so that it doesn’t run as hot.
2. This may have been for the best. I fiberglassed just enough of it before I realized how horribly wrong it was going that I managed to reinforce most of the top section which IMHO gets most of the weight - from the booster tube, injection tubes, etc plus it’s where the thrower hangs.
3. When I started building this pack it was just something fun to do, then I started doing my research and the more I read the more my inner movie geek demanded accuracy and so I started getting more and more detail orientated. Now with the pack looking like it belongs to the Stay Puft Marshmallow Man I don’t feel as pressured anymore. So that’s kind of a load off. #life_gives_lemons_make_lemonade
I did it this way (bolded) on the cyclotron half and found that there was still warping but it was less severe
Yup, I too bought the Bondo resin at Lowes. The chop mat too was made by Bondo although the funny thing was that I had to get the matt from an auto parts store because Lowes didn’t sell it. Who sells fiberglass resin but no matt? :lol:
Spray foam was my original plan. Clearly my elementary school teachers were right: “Always go with your first answer”
10 drops of hardner per oz of resin as written on the label
Yep, same as me. So sorry that It did not work out.
You used too much hardener. The recommended is 10 drops per oz, but I’ve found a happy medium around 6 drops per oz. The resin sets fast and heats up massively when you use the 10 drop recommendation.
And Lowes does sell mat by bondo (I’m an ex-employee). It’s a thick, tightly woven mat meant for bath tubs. Not a fan of it.
Hijacker, definitely paying you a visit when I start working on my wife’s SC build… I want to make her pack as light as possible, but sturdy and durable enough to last years…
I think you’re right about the hardener. Maybe if I’d had more experience with it I might have made that change to the mixture but being a n00b I’d probably have been too afraid that if I reduced the amount of the hardener then it would never harden at all. I’ve head that can happen if you mix it wrong.
I think this is probably the most reasonable solution to the problem. We should all go to Hijacker’s house to have it done right. 
ROAD TRIP!!
Beer’s in the fridge!!
But I was lucky enough to play with mixture’s while making the backer to my mold. Really helped iron kinks out before I started using it for more fine work.
Well, for me it helps that I’m only 40 mins away from him… =P
Hence the reason I did not glass the inside of my sc shell. The shell is pretty sturdy on its own, all I did was add 1/4 inch mdf to weight baring spots ( injector tubes, ion arm, gun mount, etc) no muss, no fuss. Simple measure and cut. I’m sorry your pack had a bad reaction to glassing. Is it salvageable at all?