Fiberglass bonds to fiberglass very well. Most FG layup is done with polyester resin rather than epoxy resin. It's cheaper, easier and more flexible. Reworking is best done with polyester resin as well. It's easy to tell the difference when you purchase it, epoxy will require specific resin to hardener mixing ratios, typically 1:1 or 1:2, and will have a set working time (example epoxy glue that comes in two tubes and in 5 minute, 20 minute, etc hardening times). Polyester will have a variable mixing ratio often just a small amount of hardener to resin, and setting time will be variable with amount of hardener and temperature (example body putty). To achieve a good bond, the area will need to be cleaned with solvent and roughed up with 60 grit of you will be doing a major rework, or 80-100 grit if just surfacing with putty. You want to get down to the glass fibers where you are going to rework, but only scuff the edges or areas where you will feather for final paint.
Resins by themselves have no strength, but rely on fillers to give it's strength. Typical fillers used for buildup are fiberglass cloth and matting or chopped glass fiber. Other fillers may be used to give a smooth surface and sanding ease such as talc, chalk, microballoons etc used in body putty. When using glass fiber, the strongest material will result from using just enough resin to wet out the fiber or cloth, and no more. Cloth will give the most strength, but will build slowly and isn't good for filling gaps. Mat will build faster (cloth and mat is available in various weights) so is used to build thickness, Pulled apart mat or chopped fiber is good for packing into small gaps.
It is near impossible to paint over FG that is sanded down to the fiber without the texture telegraphing thru, so build to slightly below the finished surface ~1/16" or so then top coat with body putty or polyester surfacer putty, being sure all glass is buried.
There are plenty of info available on working with FG, check at your FG supply store (check the yellow pages for Fiberglass and plastic suppliers) or online for info or ask specific questions on here.

 

thanks for the info!! ... im sure it can be done...and i will look into it a bit more...just need to come up w/ a good plan..maybe some templets of the cab contour in relation to the fender when its bolted on completly...something to go by once i remove the fender.. maybe do the same in the front, i think its going to be a long process of on and off the truck, w/ sanding and fitting..but maybe in the long run worth it? my biggest concern is purchasing new fiberglass fenders and having the same fit...
i know these fenders are old..has anyone bolted on glass fenders recently and had a real perfect fit? is this just a common thing?
also.. can anyone see the sag i speak of from the front view of my fenders??

 

49, The newer pics look alot better the the other ones but still not perfect. I think what AX is all correct, pretty much it is going to take a lot of time and knowhow to do it right. Well good luck. ya i did see the sag in the fenders. most likely from years of being bolted down not perfect.

 

If you want a perfect fit along the cowl, then mold the seam right against the cowl!
Not as difficult as it might sound, in fact it is probably the easiest way. First go to the body shop supply and get a quart of "Kitty Hair" filler. This is body putty with fine fiberglass filaments in it. It is made for building up and filling cracks in FG cars. With the fender off, lay a piece of 4 mil polyethylene sheet over the cowl so it covers at least 12" past the seam and tape firmly in place with duct tape. Be sure it lays smoothly, no wrinkles or they will transfer as well. Sand the flange and ~ 4" of the face of the fender with 100 grit to a good scuff being sure to get thru any paint and primer down to the original gell coat. Wipe the bolts with a thin coat of vaseline. Bolt the fender back in place putting the bolts right thru the plastic. Push them thru after sticking an awl or small nail thru to start the hole. Pushing the bolt thru will stretch the plastic around the bolt forming a seal. Slip small U shaped pieces of cardboard or washers between the flange and cowl at the bolts if necessary until you are satisfied with the general fit. Wash the fender down with acetone on a clean rag and DON'T touch it! Mix up some kitty hair using the minimum hardner recommended to get as long a working time as possible. (Once any body putty starts to get stiff and curdles when you squeegie it, don't use any more of it, let it harden to leather hard and scrape if off your pallet and tools and discard. Clean everything completely clean with acetone before mixing another batch.)
Pack the KH into the gap with a thin piece of plastic (credit card you've maxed out works good), stuffing in as much as possible between the cowl and fender. Scrape away any excess off the fender and cowl before it kicks. KH is harder to sand than regular body putty, so don't leave gobs on the fender to harden and have to sand off.Once all the gaps are filled and hardened, mix up a batch of your favorite body filler and squeegie on a layer ~ 4" wide and ~ 1/8" thick at the cowl tapering to a feather edge all along the back edge of the fender. You want the putty good and hard so leave it overnight. Now unbolt the fender and remove it, peeling off the plastic sheet if it sticks. Turn the fender over so the flange is facing up. Remove any spacers you may have used and examine for any small voids where the KH didn't fill all the way to the back edge, especially around the bolt holes. Mix a small batch of the KH and wipe into any voids being sure to NOT add any to the places where the fender fit tight. You just want to fill any low spots without the need to do any sanding after. Now block sand the rear edge of the fender with 80 grit on a long boardmoving the board at a 45* angle from the fender off the edge, trying to keep the edge as sharp and straight as possible. Take your time and let the sandpaper do the work. Heavy pressure just distorts the surface and clogs the paper, there is no reason to lean hard on the board. When you are completely satisfied, fold a piece of 180 grit paper over the edge and just lightly radius the sharp edge ~ 1/16". Prime, surface putty if needed and paint. When you bolt that finished fender back on it should fit perfectly!

 

I'm not sure that's a good idea; there is a fair amount of movement between the fenders and cowl. There should be a gap, and there is a strip of rubber that fills it.

 

If you get an accurate fit without the welting, then if you use welting the fit will still exactly match.
It is near impossible to mold a fiberglass part with a sharp edge like when you bend metal, and that soft edge gives away FG parts. By sharpening that edge it will look like metal. Molding the edge to the cowl like I outlined is much better IMHO than trying to freehand fit it. That would be as difficult as straightening a damaged steel fender off the truck and expection it to fit properly after. Welting can cover some sins, but not all.

 

AX,

i truly like ur idea of the repair for my fenders..i agree. taking them off and trying to free hand it will be a rediculas adventure...i think i could even "pad" out the area slightly in order to leave a gap for the welting...my biggest concern ( never having done ANYTHING w/ fiberglass) is just the possibility of this "added" area to crack further down the road...w/ so much movement and stress in these areas...how well will this kitty hair bond to the fiberglass? i thought for sure a regular resin and matting procedure would be necesary??? im wondering about using ur ideas..but using the resin and mat material even if to only get the right gaps and contours..then remove the fenders to complete the job using resin and mat,..,then the kitty hair for thinner spots? i know my pictures dont show the true image..ive tossed many into my profile...we're talking some major gaps here...well over and inch in some places...
have any of u guys ever bolted the back half of ur fenders to the cab in the cowl area?? what might happen?

 

The fenders are bolted to the cowl, because they are bolted to the inner fenders, which are bolted to the cowl. This is a problem with all Bonus Builts. The cab is floating on the frame (rubber isolators), the inner fenders are bolted to the cab and to the radiator support, which is also floating (on springs) off the frame. So far, so good. But then the front fenders bolt to the inner fenders and are also bolted to the running boards, which are connected to the frame directly. Personally, I think this is why we always find the bolt holes at the bottom of the front fenders torn apart and rusted. The fenders try to float, but are anchored to the runnning boards. I have glass fenders, so I left out the bolts to the running boards, as so far, so good. I intend to make a "loose" connection like a spring-loaded bolt, eventually. There is definitely movement between the fender and running board.

I know '48-'50's are a little different than the more refined '51-'52's in this respect, but both use a 3/4"-wide rubber strip between the fender and cowl. A tight fit here just isn't necessary, underneath the rubber, mine looks just like yours does now:

 

Alb,

like the color!... urs really had gaps as large as mine? u wouldnt happen to have a picture of urs w/ the hood open of this area would u? did urs have that huge gap where it follows the corner around the cowl? how about the gap of ur glass fenders between the front grill panel?
i had pretty much this same gap before and would have to occasionally push that welting back in once i got home from a ride haha..
SOO this is my next question...why are these cabs mounted as they are...i assume its so that the frame can flex around and not twist the cab along w/ it.. yet..what about us guys w/ the darkside suspension that have portions of our frames boxed in?
im certainly not trying to redesign the wheel here..or the truck haha..but im just wondering which way to roll here..im more confident in making the back of these fenders fit correctly then that area up between the fender and upper grill panel...thats where i see things really going bad if i dont do the gap filling correctly....
Alb...how much trouble did u have fitting ur fenders? did they fit around the grill better then mine do? (see above pics) i cant imagine what its going to be like trying to assemble this nose after its painted...i was laying on my back using both hands and all my toes to get that grill in...and yes that was w/ EVERYTHING still loose...i then had to put 3 1/2 bolts in the lower grill apron/lower fender and slowly crank the panels together...
thanks for the interest in all of this from all of u...im really kinda sick about it..seeing as (in my own opinion) the nose of these trucks is the important part....i just want a presentable "fit"

 

OK, I understand now how the front of the F1s areassembled. I had the mistaken impression the fenders bolted to the cowl like the F100s with just the thin welting between. Sorry.
AFA the Kitty Hair bonding to the glass, as long as the surface is roughed up to cut thru the gell coat, it will bond to the glass more permanently than body putty to metal, since chemically it is the same material it has the same contraction/expansion rate and flexibility. You only need to go to resin and cloth or mat if you are building a new area that is relatively large, such as filling the frame slots in a FG front lower pan if not using bumpers, or to reinforce a cut thru the panel like someone here did a while back where they moved the wheel well openings forwards in their front fenders or where you need to extend an unsupported edge such as the rear edge of a FG hood. I have stiffened FG panels that wanted to oil can or were too flexible (on race cars) by placing a length of flexible plastic tubing on the inside where I wanted a stiffening rib then laying up several layers of glass cloth and resin over it. After the resin kicks you twist and pull the tubing out leaving a hollow rib.
If you think you have fit issues you want to try working with race car lightweight panels and parts! Because they are extra thin they tend to warp all over the place. On my brother's Omega he had to cut one of the doors into 3 pieces and put it back together to get it to fit. From what I understand and read, Fairlane's F100 hoods and one piece front ends need major surgery to come close to fitting.

 

I t was no treat to get the left fender bolted up, in fact it still isn't totally cranked down. (The right fender slapped right up, no problem. Are your fenders made by Gibbons?) The area around the grille panel (vertical panel w/headlight) needed a fair amount of sanding, and getting it to connect to the lower front extension was nerve-wracking, scared the panel would crack. Crank down a little at a time, when it's been sitting in the sun, etc.

These don't show the gap real well, because the rubber is glued to the fender. With patience, you'll get there!

Edit: found this pick of fit-up

 

thanks!
looks like u had a much better fit to start w/... the fender line doesnt even come close to matching the cab of my truck..i do believe ill get it done..just trying to go about it the right way.. i forgot urs has a differant grill then mine.. sorry to be a pest.. do u have any pics of the fender to running board fit? i have glass running boards too.. thats whole nother subject for another day hahaha...
i think my fenders were made by Fa? something starting w/ an F.....
i just found some pics from the early 90's from my first attempt at this project.. ill see if i can scan and post them.. i dont know why im still having so much trouble posting pics...takes me forever each time...blonde moment perhaps...

 

Fairlane? They are generally very high quality

 

that sounds familiar Alb....... il try to find the answer...

 

I bought lower fronts from Fairlane for my 50; will not be installing them until this winter but they were great to deal with and delivery was excellent.

I may re-work the original metal on lowers.

Good luck with the alignment; with so much work done on the cab, fenders etc I'm hoping bolt up will be "reasonably "straight" forward.

Tom