Bodywork Overview
Frequently Asked Questions
What are the differences between restoring/repairing a fibreglass body panel compared to a steel one?
1) You have to be careful when flatting down the paint not to start rubbing through the "gel" coat of the fibreglass. This is the protective smooth layer of (sometimes) coloured resin which is intended to simulate the surface of a metal body panel - and also protects the main layers of resin/strand matting mix underneath. Unlike metal panels, your sanding block will not detect the fibreglass layer - so you will need to know when to stop.
2) Stripping the paint requires a lot of patience. Very careful use of a heat gun combined with a semi sharp scraper is my choice, but only down to the primer layers, then it's down to a good old sanding block and plenty of hours/days work. DA (Dual Action) air & electric powered orbital sanders may seem like a good idea, and will suffice if doing a superficial repair, but as soon as you start breaking into the gel coat you can find yourself reshaping the body panel from a nice curve to a multi faceted nightmare! Paint stripper is not advisable, although I did try a special liquid which claimed to be kind to non metal surfaces. This barely dissolved the top layer of paint, and was especially slow on two-pack paints - so I would advise against this. NEVER use standard paint stripper of any type, as you will dissolve the gel coat and possibly more.
3) Holes have to be filled with new fibreglass material, not just filled with polyester. You will need various types of fibreglass matting to do this correctly - depending on where the holes are. Another problem is crazing of the gel coat, and stress cracks which need to be treated as structural repairs, rather than simply skimming a layer of filler to cover them up.
4) Moisture can be trapped inside panels which are left outside after flatting down to the gel coat - therefore just because it can't rust, don't assume it's OK left to the elements outside. A major problem for all car restorers is moisture - which not only comes from the air, but also from the air supply for the paint gun - poor water filtering from the compressor/air tank plays havoc when spraying - read about that and much more further in this section (such as why fibreglass cars don't like car covers in the winter that rest on the paintwork....). All this applies with regard to contaminants in the atmosphere such as silicone, greases and so on - anything but a pure gel coat surface is as good as useless.
Why repair my TVR myself?
1) Well, that's up to you, but if you have the time & patience it can pay dividends in a number of ways - a) it will save you money, b) you will learn a new skill, c) you have only yourself to blame for poor quality, not finishing on time, d) you may be surprised to learn that many bodyshops don't spend enough time fixing problems, they simply cover them up (you have no way of telling as you do with metal cars how good the repair is - (a special magnetic depth gauge allows you to see how deep the filler is can be purchased for metal cars).
2) Finish quality can most definitely be better than original - even when using old fashioned paint systems like cellulose (it's also your only choice if you want to stay healthy!).
3) The more you know your TVR, the easier it gets each time you need to do something or if something goes wrong with it. Unless you have no space to work on your car, the more time spent "tinkering" in the garage/on the driveway, the less problems you will have with it.
Lets get started......
Types of repair to fibreglass main & gel coat layers (this assumes you have already removed the layers of paint down to the gel coat)
Foreword & Warning! Repairs to bodywork involves the use of power tools and hazardous materials/chemicals. Minifix cannot be held responsible in any way for injury caused by the action of a reader. Please be safe, use the correct face/eye/ear/respiratory/skin protection, and if in doubt consult your local car body paint supplier.
1. Fine Cracks/hairline stress cracks to gel coat - removal & preparation to top coat stage
These must be ground out using an electric or preferably an air powered "cut off" grinder. If using the electric type you may be somewhat limited to the size and type of discs you can use, and obviously the thinner the better as you need to keep the surrounding area untouched. The best disc to use is a metal cutting and not grinding disc, due to its thin profile. If using the air powered grinder tool, you will be able to use an even thinner and smaller diameter disc (the smaller diameter and thickness make repairs much easier to finish, and smaller diameter also assists when working in tight areas such as in door shuts or swaged areas).
Step 1: Once paint is removed (so you can determine the extent of the crack(s)), carefully grind approx. 2-3mm through gel coat until you reach main layer of fibre/resin mix, right along the crack plus 5-10mm at each end. This will ensure that any "invisible" cracking not yet apparent can be removed with rest of repair. You will then need to dust off the panel, and blast the area with high pressure air from a compressor (70psi approx.). Any less and you may find "dust" from grinding can remain in ground area causing new resin to not stick correctly.
Step 2: Mix some fibreglass repair compound (they type with resin impregnated fibreglass strand - normally in a blue tin (mentioning no names). Try your local bodyshop paint supplier for trade products as going to your local superstore means you'll be paying through the nose. You will have to experiment with quantities by trial & error, as too much mixed will mean it will harden before you put it all onto the repair area. Note winter repairs in unheated workshops are best avoided due to poor hardening of repair compounds under about 15ºC. A little at a time, fill the crack with the resin/fibre mix, and "stipple" the mixture inside the ground line so as to remove any air bubbles, and to ensure resin has fully bonded with existing gel coat. Work your way from one end to the other, then leave to harden (between 20mins & 1 hour dependant on temperature).
Step 3: Once fully set, the area will be "tack free" - that is the repair will no longer be sticky. Using a block with 80 grit aluminium oxide or similar paper, gently skim the new repair until you just start to make contact with the old surrounding gel coat. Once done, you then need to swap to 180 grit wet & dry paper and do the same, until area blends in with surrounding area. You will almost be sure to have a few unfilled areas or low spots, so you'll need to repeat this step until happy with the finish. Degrease panel with panel wipe fluid.
Step 4: With a small mix of filler/primer, spray the area with a couple of coats, leave to harden, then spray a guide coat of matt black paint (easier from a can) to the primer area. Leave to harden again, then dry sand with 180 grit paper to find any small blemishes. If any are found, fill with stopper paste (use 2 pack acrylic type as cellulose takes too long & sinks for weeks after). Dry sand again, and when happy, flat the complete area down to the gel coat level again. Degrease panel fully with panel wipe fluid.
Step 5: Using a proprietary etch primer (again see your local paint supplier), prime the surrounding gel coat to ensure following layers of paint have a good base surface. Allow to harden fully - see manufacturer's instructions.
Step 6: Using 1k (or single pack) acrylic filler-primer, spray the repair area with up to 8 coats (or until happy any small blemishes will be adequately covered). Allow to harden fully.
Step 7: Use the guide coat black (see stage 4), cover all the primed area & allow to harden.
Step 8: Using a finer grade wet & dry (800 grit is best, 600 if you're feeling lazy), wet flat the primed surface & surrounding area with a block until all the guide coat black disappears. Any guide coat that remains indicates a low spot in the panel (requiring either polyester body filler, stopper, or more resin/fibre mix - depending on type/shape of area). Once happy with area, degrease panel again.
Step 9: Spray a final 2 coats of filler-primer, but add a little more thinner than before to ensure a really smooth paint finish ( and to make final flatting easier). Apply a guide coat again, then repeat stage 8 until panel really smooth/blemish free. Degrease panel, ready to apply top coats of paint.