gbarmore

I'm bonding a fiberglass bumper to an SMC front clip on my 80 and glassing it in for a seamless look. I'm using Lord Fusor 100EZ Plastic Panel Repair Adhesive for the bond, and will be glassing in the seam with West Systems Epoxy and Mat.

Question is, do I need to remove the gel-coat from the Eckler's bumper before bonding it to the front clip to get a good bond? Dpes the gel-coat need to be removed from the seam area where I will be laying out the epoxy and mat? I'm actually unsure what purpose the gel-coat serves, but it seems to have been laid on fairly heavily.

Appreciate any feedback!

Greg

John S 1961

Epoxy and mat dont work together, it has to do with the binder on the mat, I think there may be a special mat for Epoxy.

gbarmore

Huh???? Pretty sure fiberglass mat and epoxy work quite well together..... Maybe some confusion regarding what I'm doing here??

markids77

Remove the gelcoat to allow a trough for the epoxy and mat to fill and provide strength to your seam. Gelcoat is really not a structural material; it is a cosmetic application which lends little strength or rigidity to the part.

gbarmore

Thanks markids77, appreciate the input. I assume the gelcoat only needs to be scuffed in the other areas prior to filler, primer, paint but please chime in if I'm mistaken.

Thanks,
Greg

Scott Marzahl

Greg,
I would try to avoid using the epoxy adhesive if possible. I did this to my kids '76 and used 3M 8115 epoxy to bond the bumper in place. Then dished the area out, filled with mat and epoxy, and finished with Evercoat 870/880 filler and damn it if I don't get a seam ghost line in the sun. I think it has to do with the epoxy. All the other glass repairs to the car do not show up, just this seam.

BTW, there is no problem using mat and epoxy resin, there is no styrene in the resin so it will not break down the binder in the mat but that is it. The mat will just remain a little stiffer than if you were to use polyester resin.

gbarmore

Hi Scott, greatly appreciate the input. I have heard many stories about ghost lines and I'm worried about that as it would completely defeat the whole purpose of glassing in my bumpers in the first place. I have thought about ways to use only glass / epoxy and apply it to both sides of the bumper, top and underside. That is a tricky thing though and I can't imagine the seam being strong enough if I were to only glass the top without any bonding.

The other alternative is bolting the bumper on and then glassing it in, but I would think that the fasteners would expand and contract at different rates than the glass and could cause other problems long term as well.

I was out in the garage last night just staring at the front bumper that I've spent MANY hours massaging to fit, and thinking how easy it would be to just bolt on the old plastic one and be done with it.

If you could it to do again, how would you do it differently on your son's '76?

Thanks,
Greg

DUB

I...PROFESSIONALLY would NOT bond your front bumper on. Many reasons for this and one of then is future service work. Another is that regardless on what you use...you will get a crack in time. too much flexibility and the bumper was not designed or given additional anchoring points to aid in making it more rigid.

YES..I know many of you have molded them in and they are great...I am glad to hear it.

I have done numerous (in the past) and I used Fiberglass/Evercoats part # 994 ( SMC Panel Adhesive) and have found that no line will come up using it...along with the Fiberglass/Evercoats part number 880 (Vette Panel Adhesive/Filler) There is specific prep / set-up needed to make this go well.

I had in the past I used a 2-part epoxy and had problems due to it not being a sturdy adhesive and allowed movement BECAUSE it was designed to go under the panel where there is no seam to fill.

I now install the bumpers and make them so when they are bolted in place...the seam is SUPER tight and NICE. If you care to know how...PM me and I will let you in on it.

And yes...I would remove the gelcoat entirely in the bond area.

DUB

gbarmore

DUB, many thanks for the feedback on this. PM Sent......

Scott Marzahl

Personally I would not glass it in. I tried talking my kid out of it for the very reasons DUB provided but no luck. I had the replacement bumper fitted with very tight lines as well but he wanted it glassed. I think I would use the SMC adhesive since it is more like the substrate it is being bonded to rather than using an epoxy adhesive again. It takes so much time to fit a fiberglass bumper correctly, I would almost use the urethane bumper if you could live with the look.