leskinner

Hi Guys-
I'm trying to put an Ecklers fiberglass front bumper cover on my 75 convertible. It doesn't fit I think because the front end has been broken and repaired many times by previous owners. I have read several posts here about bonding the new bumper cover on with just an adhesive and ending up seamless. I was planning on bonding it with glass mat and resin for strength and then filler for the seamless look. After reading what others here have done with just adhesive, is the glass mat and resin overkill?
TIA
Larry

onaqwst

you will need to V-groove the seam and use the proper resin/matte/filler to make it happen....

it's alot of work but will turn out nice

b

SH-60B

I would use the adhesive for bonding on the fenders. I think it's just called "vette panel adhesive". Then use some Rage fiberglass, then filler / high build primer.

MN80Vette

I used panel adhesive on mine but I didn't use fiberglass. Mine seamless bumpers are bolted to the body with stainless steel bolts through 1/8" x 2" x 1/2" aluminum rectangular washers on both sides and nylon core lock washers. The single 1 1/2" long hairline crack I have now is in the filler but half of the crack is diagnonal to the seam line.

V-Twin

Epoxy bond the bumpers to the front and then groove the parting line and lay in some glass to get a uniform surface for prep & paint. Bolting the bumpers will not rigidly attach them and it will eventially lead to cracking. Bonding is the only way to do it properly.

onaqwst

Bullcrappy1

That looks GREAT... i will have that done...

r

onaqwst

just remember to buy the correct resin/filler....

i bought the typical homedepot resin and filler..... not a good idea....... i have to redo everything because of that...... you have to get an epoxy based resin ..... not polyester (the typical store crap)


b

had alot of typos in this....#$%^&

V-Twin

epoxy based resins don't contain styrene and won't break down the binders of your crushed fiber mat. Epoxy based resins do not "wet" the fibers, it won't work very well at all. You won't end up with a polester/fiber matrix but with a epoxy with fibers in it, there's no crosslinking no nothing

onaqwst

ahh......

glad to know that......

all i know is that the stuff i used was the wrong stuff........

some one suggested the "west systems" products....... i thought those were epoxy based.....


hmmm


b

Bullcrappy1

So exactly what do i tell my body guy...what to use to fill those seams..so they never crack?

how long ago did you have urs done? how many miles year?

thx
r

MN80Vette

Bonding is a must. I didn't trust bonding alone though, so I bonded AND bolted the bumpers on.

stinger12

Okay, here is the low down on the epoxy stuff. People have there own opinions on what is right and what is wrong, and I have researched everything in regards to which resin to use, which resin not to use, which is good, which is bad...the works.

Fiberglass matte is held together with a binder called "styrene". when you use fiberglass matte with your typical polyester resin, the styrene in the polyester resin dissolves the styrene in the fiberglass matte. You are then left with very formable fiberglass matte. It will take on any shape you want it to. I have talked to several guys regarding the use of regular polyester resin on pre 1982 bodies, and some still stand by it that the regular polyester stuff will work just fine with any body panel before 1982. V-twin, me and your bro had a really long conversation on vettemod about a week ago regarding all this stuff, there is conflicting information out there regarding SMC panels.

Now, this being said, you have a few options. You could test out using regular polyester resin on your body panels, and see if you can pull it up - remember, prep is extremely important. Like I said before, I know a guy who has been working on vettes for 30 years and he has only had one issue with the polyester stuff not sticking, and that was on a really late model one. Rough up the surface extremely good. remove all contaminants, clean, clean, clean. Try to pry it off, leave it in the sun, let it cool down, leave it in the sun, then try pulling it off again - if you can't pull it off after several weeks, chances are you aren't going to pull it off.

Yes, you can use fiberglass matte with west system epoxy resin. The only issue here is because epoxy resin does not contain any styrene, the fiberglass matte does not form like it does with regular polyester resin. The matte stays more stiff, and the styrene just stays suspended in the fibers, thus it is more stiff. It is also much harder to wet out. I use a stiff bristle brush and dab the hell out of the fibers on a plexiglass sheet. Once I wet it out, I put it on the car and work it the best I can. Remember, because the matt stays stiff, you don't have to wet it out on the car, you can wet it out on another surface, then pick it up and place it on your v'd out groove. Before you wet it out, try softening the glass by bending it in your hands - the styrene is not going to dissolve, so it is going to be muc hharder to work with unfortunately. I know they sell stitched fiberglass matte which does not contain styrene, and it works very well with epoxy. The fibers are held together using stitching evey 1/4'' on the sheet of matt. Thus, its just like working with polyester resin and matte, but instead of styrene holding the fibers together, there is stitching holding the fibers together. I have not used this type of fiberglass matt myself, as I have not done a ton of glass work on my vette yet.

Evercoat makes an SMC resin which is polyester based, and it contains styrene in the mixture. It works with regular fiberglass and also with SMC panels. So what is the difference between it and regular polyester resin? Here's a message I received directly from evercoat...

The reason that SMC Resin work on SMC panels where regular polyester resin won’t is because SMC resin contains a small amount of Methyl Methacrylate (MMA) that help to increase the bond. The MMA works to compensate for the mold release that is in the SMC panel. SMC stands for Sheet Molded Compound/Composite.

In order for the material to be molded it is placed inside of the mold which has a positive and negative side. The material is compressed between theses two sides during the manufacturing process. After the part is cured the positive and negative molds are separated and the part is removed. In order for these parts to come out of the mold a release agent is incorporate into the resin that allows the parts to easily removed, otherwise they would stick to the molds. It’s this release agent that causes the issue for traditional polyester resins to not stick.


So, if you want the qualities of fiberglass matting and polyester resin being more formable, and faster drying times, the smc evercoat resin might be the way to go. Whichever way you put it, everyone will tell you something different. That's the jist of it with bodywork - everyone has their own beliefs, and you will not get one straight answer.

Here is an article from west systems regarding the use of fiberglass matt with their resin...

Chopped strand mat & epoxy


By Tom Pawlak

Chopped strand mat, in fabric form, is sold on the roll and in small folded packages. It is made up of 1"-2" long fiberglass strands that are randomly oriented and typically held together with a styrene-soluble binder that acts like glue connecting the fibers. The binder is designed to dissolve upon contact with styrene in polyester resin or vinylester resin. Once dissolved, the fabric softens, allowing it to drape around curved shapes. It comes in a variety of weights between .75 oz to 3 oz per square foot. The most popular weights are .75 oz and 1.5 oz.

In the US, chopped strand mat is nearly always sold or specified in ounces per square foot. This is different than fiberglass cloth and fiberglass fabrics with oriented fiber layers (including woven cloth, stitched biaxial & triaxial fabrics, and the like). These are designated in ounces per square yard. When mat is attached to any of these fabrics (as in fabmat or biaxial with mat), the combined fabric is often called out in fabric weight. An example of this is our 738 Biaxial Fabric, which is a 1508 biaxial fabric with mat. This means 15 oz per sq yard of biaxial fabric plus an attached 0.8 oz per sq foot layer of mat.

The big question

Can WEST SYSTEM® epoxy be used to wet out chopped strand mat? The answer is yes. The fiberglass strand in mat wets out with epoxy, but the binder holding things together does not dissolve. (It does get put into suspension and is sealed in the cured epoxy.) This undissolved binder causes the wet-out mat to remain a bit stiff compared to wet out with a styrene-based resin. For gently curving or flat projects like cabin soles or plywood decks, mat and epoxy should work fine. The fabric does not wet out perfectly clear with epoxy. Wet-out clarity of mat with epoxy varies somewhat with different suppliers, but none of them wet out as clear as a good 4 oz or 6 oz fiberglass cloth.

The texture of the chopped strand mat is quite rough given its random fibers (many of which come loose when epoxy is applied). Mat requires a number of coats of epoxy to fill the profile at the surface. 879 Release Fabric can be applied over the freshly wet-out mat to compress the fibers and minimize the need for many of the buildup coats. Using release fabric in this way will result in a much smoother surface, and if you are going to allow the epoxy to cure before continuing, the surface is ready for buildup coats of epoxy or fairing putty after the release fabric is removed.

4 mil plastic sheeting can also be used over the still uncured epoxy and mat to compress the fibers. Trapped air bubbles can be removed by piercing or slitting the plastic over the bubble before the epoxy begins to cure. If the plastic was clean when it was applied, you can pull the plastic after the epoxy cures to a hard gel and apply epoxy fairing putty or buildup coats of epoxy later the same day. If you allow the epoxy to cure hard before pulling the plastic, be sure to sand the surface completely dull before applying more epoxy.

When choosing chopped strand mat to be used with epoxy, look for mat that is soft and pliable. Some forms are quite stiff and may cause problems wetting out with epoxy. Stiff mat is often older stock and the fibers may take more time to wet out with epoxy.

Stitched mat

There are chopped strand mats produced without binder that work extremely well with epoxy. These products are referred to as stitched mats. The random oriented strands are held together with light stitching, which runs parallel to the length of the roll and is spaced about 3/16" to 1/4" apart over the width of the roll. The stitching eliminates the need for binders. These products tend to wet out a bit faster with epoxy and become more flexible on average than generic chopped strand mats.

These stitched mats are suitable for use above and below the waterline for marine applications. Roll mat, the type held together with binder (not stitched), is used by some of our customers for new construction and repair for below water applications, but we have had some reservations on this if the boat stays in the water.

Testing in warm/moist conditions

To see if our concerns were justified, we compared samples of generic chopped strand mat (wet out with WEST SYSTEM 105 Resin and 206 Hardener) against samples made with our Episize™ fiberglass fabrics (wet out with 105/206) in moisture uptake testing under warm/moist conditions. The test environment was a room we affectionately refer to as "The Amazon Room". This room is maintained at 100°F and 100% relative humidity, jungle-like conditions. All of the samples were accurately weighed on a gram scale before entering the chamber. Each specimen was weighed periodically until no additional weight gain was observed. The samples made with generic roll mat and epoxy experienced an average 2.3% weight gain over a two-month period. The Episize fiberglass/epoxy samples gained weight at a slightly lower percentage of 1.9%.

Wet-out chopped strand mat and woven fabric test samples are prepared for moisture uptake testing.

Visually all of the fiberglass/epoxy samples "whited-out" or became slightly more opaque during the test. We were not concerned about this because there were no obvious differences in appearance between samples made with our Episize™ fiberglass and samples made with generic chopped strand mat. Our test included three specimens of chopped strand mat, two different sources of 1.5 oz and one 3 oz. One of the samples was made with generic mat found on the fiberglass rack in our shop, and the other two were purchased from Composite Structures Technology in Tehachapi, California. (661-822-4162)

Conclusion

Chopped strand mat can be used effectively with WEST SYSTEM epoxy for a variety of marine projects. Based on the results of our moisture uptake testing, we would feel comfortable using the mats that we tested for below the waterline applications including hulls that stay in the water for extended periods. Like any fiberglass applied to surfaces that will be used below the waterline, barrier coats of epoxy are necessary over the fabric to provide the moisture barrier required for long-term protection.

2000FRCZ19

this is what i did with mine and it worked very well. use lord fusor t-21 epoxy adheasive. then sand it, v-groove the body and use fiberglass and resin on top of the seam. the fusor t-21 is very strong and will hold the body pannels together with no problems. you can make a stronger bond by drilling the bumper and the body a few times so the fusor squeezes through the holes when the two are placed together.

Bruthish

Vette Mag(or maybe it was Corvette Fever?) just ran an article on doing this. They used "Mar Hair"(sp?) to bond it.

onaqwst

if i get a chance to get to my vette....which is 20 minutes away now.... i';ll get some pics of what is going on with my 77 when i used the resin for home depot..... (f^&kn b.s.)...

i talked to a friend today that paints lowriders and all that eye candy stuff and he might be able to hook me up with a homie discount to fix/repaint my 77....hmmmm.... might want to suicide the doors now..

b

leskinner

Thanks to everyone for the replies. I will V-groove the seam as suggested, it's already bolted, and use the SMC resin I got from Ecklers
for an earlier project. And ONAQWST, that's the nicest Vette I've seen in a long while. You've given me a standard to shoot for.
Thanks again everybody! I'm goin' for it!
Larry

noonie

Polyester resins, depending on the composition can have a shelf life of approximately a month. On the other end of the spectrum is a good epoxy that has an average shelf life of approx a year.

Chances are, if you buy resin at Homey Depot, in the quantities that they buy, and the length of time it sits in their warehouses and stores until some noobee decides to take a stab at it, your chances of getting junk are quite high.

Smart thing to do is to buy your supplies from a big high sales dealer that specializes in glass.
Look at onaqwst's situation, a redo and repaint ain't cheap.

Why don't you guy's read up at an authoritive source like Composite World or compareable to get some no bull****, non marketing answers.


And Onaquest's car looks great. Nice Job.

onaqwst

thanks people......

it's different and i got alot of heat in the beginning for doing what i did...


it's alot of work to get the seams straight and in line..... i actually cut my front bumper in 3 pieces to make it look right..... dont ask me why i did that really....

also make sure your bumpers and lower than higher on the seam..... it's easier to build up the bumper and long-board it even..... but if you are high then you will need to build up even more on the body.....

make sure to pop/sand out any air pockets too.......in between layers i tok a palm sander with 60 grit just to get the boogers/etc off and rough it up for the next layer.....


good luck.....

luckily my paint job only cost me 2500 so i'm not out that much..... it's 2 years old now.....

Overlord

[QUOTE=onaqwst;1565218400]


Wow! Those are the biggest cup holders I've ever seen!