I have some used fiberglass fenders I plan to use. They don't have any damage to them from an accident or anything. They do however have some hairline spider cracks that I don't want coming back. The cracks are probably just in the gel-coat but I need to fix them. I know I could just DA it down until the cracks are gone but what is the best way to finish it? Can I just use epoxy primer? Urethane primer? Or can a new gel-coat be applied and is that necessary? I will need something on top that's high build so I can block it down afterwards to get the ripples out. I do all my own body and paint work as it was my former profession for a few years but I don't have much experience with fiberglass body panels. Thanks for any advice.
common problem as the old gelcoats expand contract(which causes the crazing/spider cracks) and as the overall units chemical composition shrinks over time. You will need to treat them as you would a plastic/uretahne bumber for best results. get back down the gel coat without causing any more damage if possible fill prime flex prime as you would plastic or urethane bumber covers/body kits(you can use additives with many off shelf products as well) urethane sealer would be optional here flex paint(with same flex additives used to prime) the flexible primer/topcoat will now be much more forgiving to expansion contraction and nearly eliminate future crazing/cracking issues(even though they will likely continue to develop underneath) and the units will be considerably more durable for chip resistance.
I use this when repairing some of my Shelby fiberglass. V the crack with a Dremel and fill. Read it on a Corvette restoration site. http://www.evercoat.com/productDetail.aspx?pID=13 Then epoxy prime. Early Shelbys and Corvettes didn't use gelcoat.
Predfan, That Evercoat product looks like its for repairing deeper damage than what I have. Groberts, The flex paint would be an additive I assume? And use it in the primer, color, and clear?
it is. You can also buy some products that come packaged with it.. or just stick with one's that are urethane based(usually the premium lines) to begin with and the need for their use becomes less critical. Whatever you do.. just be sure to talk to the supplier about your needs and the compatability with the chosen products, is all. Here's a quick link to help with an overview of potential pitfalls and what other pro's recommend. However, this thread is older and you might want to look for some newer posts to get a better idea of the newest pitfalls though. http://autobodystore.com/forum/showthread.php?3529-Using-flex-agent&
I assume you are talking about the typical fiberglass stress cracks (not cracked fiberglass from damage). You have to cut out the crack as much as possible with a Dremel, if you just sand it down it may look gone but the crack is still there. Skim it with the Evercoat fill, sand, epoxy prime, high build primer, block, colorcoat and clear.
I believe he's descibing crazing and spidering.. not actual flex caused depth cracks. These types of cracks are no the same as impact or flex cracks and only go so deep into the gelcoating and would not require digging out to repair. You'd actually cause more damage and weaken the panal if you did v them all. Not to mention.. it would look like a termite burrowed through the panle after you were done prepping it. lol
The common stress crack or surface crack is not related to an impact. V'ing the crack and filling with the proper material is the standard used by most vintage Corvette restoration shops. This method has been proven to last much better than just doing a surface repair which has very limited success. We're not talking about using a router and making termite trails.
I realize that you're trying to help here just like I am.. and I'm not trying to step on your toe's here. I repair fiberglass bathtubs for a living which are required to take thermal shock and constant flexural loading(also keep in mind that a lot of people in the midwest aren't exactly "little" either) and have fair bit of experience in regard to glass autobody repair/refinishing as well. Based on that.. all I can say with complete certianty.. is that using "evercoat" on "v'd out fiberglass cracks".. regardless of how deep they are.. will not add much structural integrity to the repairs.. especially as they get deeper. This is simply because the plastic putty(Evercoat is just another brand which makes many various products intended for specific applications) that you recommend for "doing it right".. is not going to be even close to stronger than the fiberglass resin/gelcoat it means to replace.. and would only be considered cosmetic preparation. In a nutshell.. and IMO.. it's like this. If it's actually cracked?.. repair it right with more resin/gelcoat(and possibly a reinforcement backer cloth on the underside). If it's just cosmetic?.. grind it down to resin/gelcoat and see if you even need any putty before using surfacer. The more coats of anything added.. only increases cost and adds more points of failure down the road.
Yeah I know nothing about fixing fiberglass bathtubs. I'd recommend the op Google "Corvette stress crack repair" for more info and opinions. You kind find the most info. on this type of repair using that search since it is such a common topic.
just to be clear here.. I really wasn't trying to "one up you" with my advice above.. and after belated inspection of your link shown above.. that product is certianly designed for the task you mentioned. My bad.. and I seemingly jumped the gun in my previous statement about reduced durability when using "regular plastic filler" as that's obviously not "regular lighweight filler". I'll try harder to read more and post less next time. :Handshake Because if the OP has stated that his cracks were more severe?.. I'd have been 100% in agreeance with that protocol. Now, I'm certainly not one to scoff at overkill.. but it seems that he isn't at an advanced state of repair is all. TBH, I should have included a disclaimer right up front as I tend to over engineer(and therefore overspend) on most projects that I do.. cars or otherwise.. so with that in mind the OP could very likely get away with just sanding and spray filling with some decent urethane primer and topcoats(which will have enough "flex agents inherent to the product itself) to give more than enough flexability for a couple of front fenders which don't see much more than vibratory and bounce stress anyways(not in as bad astructural environment as Corvette body would be). In other words.. flex agent additives can be a tad tougher to work with and don't necessarily buff out quite as easily as just straight urethane and may just be overkill in that environment. Hope that helps the OP better make up his mind and balance durability and end results with the time and cost involved.
