Kenworth Project

'68 Coronet R/T

'68 Coronet R/T

Oldtimer
Would like some suggestions on how to patch the left fender on this truck.
I have done some minor patchwork on fiberglass but this fender has a pretty big crack from running into a deer.
Left Fender Damage 1.JPG


There are also spots of damage where a steel cable was run into:
Left Fender Damage.JPG
 
I did a similar repair on a Marmon tractor in the same wheel opening. Using West marine epoxy, I did a very wide and very tapered VEE relief through the area and went through about 3/4 of the way through the fender. Then applied varying layers of mat to build the area back up (opening clamped as needed to keep wheel opening from moving). Once all that area has cured, perform the same very wide VEE to the back side, about 1/2 to 3/4 of the way through (verified by grinding into the new area) and repeat the process of laying mat in to build up the back side.

Any of the other damaged areas will have exposed and dry (no resin) areas, repeat similar process to make the areas are structurally sound again.
 
I have done it the same way MP&C except I used polyester laminating resin or SMC resin if that was what the parts were made of.
Nothing wrong with West epoxy resin. If I remember it correctly, I think the fiberglass matt has to be compatible with epoxy resin?
What makes it go a little easier is to precut the pieces of matt that I think it will take to build out the tapered area making the pieces larger from the bottom up, with overlap. Random strand matt seems to work the best for me anyway. I mix up the resin and pile the matts up wetting them out thoroughly. One of those cheap serrated rollers helps smooth and pack the layers. Then grind and sand to shape, add to low spots if they happen.
 
What would be the best fiberglass repair products to buy? Is the cloth better than the matte or should I use both?
 
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Matt builds thickness quickly and offers strength in all directions.
Cloth is thinner so takes more layers and strength is usually just in 2 axis,0-90 or 45-45 so each layer you turn a little.
Polly resin is most likely what its made from.
Yes you need matt glass that's meant for epoxy if you go that way but expensive compared to polly resin.
Wet your glass first then lay down on repair area.Get a bubble buster roller.
I believe your last layers you use a finishing cloth? Cant remember if sanding into matt will finish nice.Its been awhile.

edit,,,,,Print through can be a problem with polyester resin.
 
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With being a semi hood strength should be considered,you can get glass thats matt backed so 45-45 is good for twisting strength ,you can get double bias or single.
So you basically create a sandwich of glass,the inside is matt for thickness the outside is the cloth for strength.
 
Some other tidbits as it comes to mind,polly resin is covered in gel coat as a paintable surface,Epoxy doesn't need the gelcoat. Polly doesn't stick to epoxy but epoxy will stick to polly.
Glass is purchased in weight,so 1708 is matt backed so 17oz glass being 0-90 or 45-45 and the 08 is weight of matt per sq/yd.
 
As you grind down the repair area you'll see what glass was used by the direction of the strands and how many layers.
Anyway good luck,Im itching already just thinking about this lol.
 
Cloth is strong but, harder to make lay flat, especially on a compound curve. Mat will conform to any shape after it is wetted with resin. I would think you will need both cloth and resin to do a quality repair. Poster board type cardboard is what I use to make patterns for cloth, layer your repair from both sides a mentioned above, narrow then wider strips of cloth until you have the thickness built up then mat over that to camoflage the repair area on the inside. Have several pieces of cloth precut before you start, the more you can do at one time the better repair you will have. VPA to cover all the raw glass and rough in the surface before epoxy. I think you should be able to repair the damage without it being obvious from the inside
 
1A Rock said:
Cloth is strong but, harder to make lay flat, especially on a compound curve. Mat will conform to any shape after it is wetted with resin. I would think you will need both cloth and resin to do a quality repair. Poster board type cardboard is what I use to make patterns for cloth, layer your repair from both sides a mentioned above, narrow then wider strips of cloth until you have the thickness built up then mat over that to camoflage the repair area on the inside. Have several pieces of cloth precut before you start, the more you can do at one time the better repair you will have. VPA to cover all the raw glass and rough in the surface before epoxy. I think you should be able to repair the damage without it being obvious from the inside
Click to expand...
VPA ?
 
crashtech said:
If this is a working truck, keep in mind that it has to be a really strong repair. Car knowledge does not really apply to over the road trucks, they vibrate stuff apart like no other. Leave no stress crack unground, make every repair area thicker than stock...
Click to expand...
+1

For a working truck like that, make the repair thicker than the surrounding area. The cloth would work well on the backside of the repair kind of like a piece of tape covering the repair in a sense. Fiberglass matte would be the thing to use to do the actual repair. Judging from the pics it looks like fiberglass not SMC, but hard to say for sure without laying eyes on it. I would just use SMC resin anyway as it is compatible with fiberglass. Get that old paint off of there, grind every crack with a wide vee. Nearly all the way through. If the crack goes all the way through your Vee should to for ultimate strength. Work a crack or two at the time, don't try to do too many at once. Make sure everything is clean clean clean. Be prepared to itch for a while too. :)

As for VPA, it is more expensive than regular filler and unless the customer is super particular I would not use it. Just regular filler to finish with. Properly done repair the filler will last fine. Especially if this is a working truck.
 
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Thanks everyone, you have been a great help to me.
The owner is an independent operator and recently had a bout with prostrate cancer. He want's the truck looking decent in case he has to sell it.
He spent $28,000 having the engine rebuilt two years ago so it runs great, just looks bad.
 
'68 Coronet R/T said:
Thanks everyone, you have been a great help to me.
The owner is an independent operator and recently had a bout with prostrate cancer. He want's the truck looking decent in case he has to sell it.
He spent $28,000 having the engine rebuilt two years ago so it runs great, just looks bad.
Click to expand...

The owner has been blessed having found you to do the work. You'll do the man right, no doubt in my mind.
 
If you are worried about adhesion just use Epoxy resin. The cost is minimal above poly. Use whatever cloth you want. Woven will leave an imprint through paint so just get chopped. Grind and inch past the damage for every layer of cloth you need. I have repaired a lot of Southwest flight controls surfaces in the same manor...Well we did use more vacuum bag, but you don't need that.
OK, did more reading of posts. NO SUCH THING AS poly only cloth. You can use any resin with polyester fiber cloth. IT IS Inert glass fiber! Tungsten is wrong that poly is covered in Gel coat??? Gel coat is just polyester resin with color. I have used carbon fiber, glass mat , and aramid fiber(Kevlar) with epoxy resin.
I have an extensive background in aircraft repair, from wet layups to vacuum bag, to hot bond and autoclave rebuilds of spoilers.

Sorry if this comes off aggressive.

Just an FYI. Don't use woven glass fabric on a body. It will map through.
Mat will have the same strength, just make sure you PULL the size you need from the roll and not CUT it out for your repair.
 
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I don't have anything to add here. But I just have to say how much I love this forum. Its very impressive to me when folks I would regard as high experts, are asking for other opinions and doing what they need to do to help customers fairly.

I can't think of any other forum I've ever been on that has such an allotment of fine tradesman (maybe women too...) who are willing to share their advice, tips and tricks and not be judgmental when someone doesn't know. Or is maybe misinformed. Its literally the #1 reason I can be successful doing paint/body work. Also a big reason why anyone I ever come across gets a just buy SPI and be done with it.
 
Yes, these guys are a great help.
FYI, the project has been put on hold as the owner was contracted for another hauling job.
When and if it happens, I'll keep you posted.
 
So you don't have to get the pinchies....yet.;)
I asked a guy at a fiberglass production shop how they deal with the fibers. His answer was "baby powder". They load their skin with the powder. Told me it keeps the tiny glass fragments from getting in the pores of your skin. Shower takes care of the powder and whatever glass may be still on you.
Ever since, I at least cake my arms with the powder, wear Tyvec coveralls with a hood, Nitril gloves and a full face fresh air mask when grinding the glass. I do all the grinding in my spray area with the exhaust fan running, then blow all the dust out, off me and the work. Works pretty good.
 
Yeah, talcum powder is the stuff! Although, now they say it causes cancer, and I am not certain whether its corn starch replacement works as well for this purpose.
 
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