ChasR
RR Helper
motivation
Posts: 10,241
Club RR Member Number: 170
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As above. Say you have an arch, but it's cracking. Now I know the FG and metal expand at different rates but there's not much choice in this matter.
How would you go about sorting it? Currently it has FG and P38 accross the join (FG part is held onto the metal via rivetting and some FGing from behind. This doesn't present a problem for others who keep their cars inside but I can't afford that luxury.
Discuss.
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use a different filler - not P38, it sets too hard. I'm struggling for names, but there are fillers that retain some flexability when set on the market (try looking at the U-pol range) for this sort of job.
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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GavinJ
Club Retro Rides Member
MGB 3.9 v8 Sebring
Posts: 927 
Club RR Member Number: 209
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I blended in a sebring rear valence of my MGB, using FG and some fairly cheap easy sand filler from a motor factors, cant remember the brand now but over 12 months of hard road use and no cracks have appeared....
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plastic padding used to be the flexible filler ,seam sealer can work ,use it like caulking and 'point it' with a latex glove covered finger dipped in thinners , takes alot of practice but can be done, there is also a very fine silk like matting that can be used for jointing , worth asking a grp suppliers
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yes ,it started badly ,petered off in the middle and the least said about the end the better!!!
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purplevanman
Posted a lot
Way too orangey for crows
Posts: 3,830
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Plastic Padding Elastic is one but if you google flaxible body filler there is lots  Tiger seal or Silkaflex is like silicone sealer but is used as a flexble adhesive and can be painted. |
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Welder, fabricator, general resto work
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don't forget if your using Sikaflex you really should use the primer that make's it stick like a good un It's a black paint thye affair they same stuff as they use when putting windscreens in, it is hard to get hold of though. |
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plastic padding ultima should be flexi enough
maybe its not riveted down enough or you are bridging a huge gap with filler ...scuff up the join really well and fill any gaps with furry filler , then finish off with a decent filler
is it deffo a crack and not a sinkage line?
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91 golf g60, 89 golf 16v , 88 polo breadvan
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ChasR
RR Helper
motivation
Posts: 10,241
Club RR Member Number: 170
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I'll get a pic showing the crack:  As you can see in that one, it's only slightly there, and not all around the wing where the FG and metal join.  Again, it's only on a significant portion of the rear of the arch there just behind the bulge. Again it doesn't run all the way around the arch: And another shot. Here's one showing how it is put on. It is rivetted onto the arch. The arch is on the same level as the original 1/4 panel, and where the 1/4 panel has been cut, thick metal plates were welded onto them all around, and an arch extended from the rear wing, and seam welded on to suit.   |
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pics don't help alot...id guess its moving too much , more rivets or reinforcement underneath
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91 golf g60, 89 golf 16v , 88 polo breadvan
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g40jon
Posted a lot
Posts: 2,569
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i used a filler bought from halfrauds called isopol plastic bumper filler (comes in a little black tube and is a bit pricey but worth it) when i made a custom bumper for my car. it was used to blend to plastic items, but i don't see why it wouldnt work in your situation. it allows for movement and i never had any problems with it cracking
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if it were me fitting them arch's I would have keyed up the steel on the wing ,were the glass arch's were going to fit with a 36 grip flap disk. on a 4" grinder... keyed up the facing part off the fiberglass arch the same. then tiger sealed the 2 face, and fixed the 2 together with countersunk rivets... were the tiger seal squash out between the 2 edges, DON'T wipe this off. leave it till its gone hard and then cut it off with knife.. reason being is if you wipe it in with your finger.. its going to leave a smooth face on it, that when you tidy it all up with filler.. the fillers not going to want to stick to it.. and a crack will appear!  once the sealer is hard and cut off.. key it all up again with some 80 grip sand paper.. and then thin skim off glass fiber(p38 will do) again once this has gone off.. tidy this up with 36grip flat disk on the grinder... clean off all the sh1t and its read for the filler/tidy up... shouldn't crack again  the key to bonding any "fixed on panel" Werther it be fiber glass, or an alloy panel.. is just that! KEY up the mating face's!! the ruffer the better!! IMO thats the best way to do it.. and how I have done it in the past.. worked for me |
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Last Edit: Jun 6, 2009 8:54:58 GMT by petetong
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Hi mate, I'm having some similar problems with my rear arches, I'm gonna just sand it donw again across the cracks with rough sandpaper (like 40) and then put another skim across and do that thing with the thinners to 're-point' them. Pretty annoying eh? After all the bloody ahrd work in the first place! I hate filler with a passion |
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