Seam?

[Jacob]

The bonding seams on the front fenders were very easy to see, just slight sanding with 60 grit and they were readily seen. The rear seams aren’t. My question is do you “dig” down until you reach the seam, in order to make a trench for the the filler? Or should you leave as is? My concern is that it seems I’ve read where you’ll have future problems if you don’t dig the seam out. I’ve sanded quite a bit on the rear and don’t see the seam...should I leave as is? Thanks, hopefully the pic will show what I’m talking about.80941

Please excuse the photo insert, switched from my laptop to an IPad and haven’t figured it out yet.

[DaveS53]

There's no need to dig deep. As soon a fiberglass is exposed, you'll probably have some pinholes to fill. Also no need for high strength filler in these areas. These are mold seams not separate pieces that were bonded together.

[edwardb]

Those are best described as parting lines. The body is a one piece layup over a multi-piece mold. When the layup is done, the mold is dis-assembled and removed, leaving lines where the various mold pieces were. In the past, there were often issues with contamination between the mold pieces, e.g. clay, uncured resin, gel coat, etc. If not removed, would case problems later with the paint. Hence the digging, grinding, HSRF filling, etc. For the last few years the Roadster bodies have been better and often don't require anything more than knocking off the parting line and start the usual body work. That has been the case with my two Mk4's. If you sand off the parting line and see contamination, yes grind it out. But no reason to go crazy. Best trick I've seen is to shine a light from underneath after you knock off the line. Anything that needs to be removed can be seen pretty clearly.

[Jacob]

Thanks all...you never disappoint!

[Hotyacht]

I have recently started the body work on my MkIV Roadster. I have been in the Marine Industry for 30 years and so I am very comfortable with this part of the build, but I know that others are not.

The best advice that I can give you is......JUST STEP AWAY FROM THE POWER TOOLS!

I know that it is difficult for a guy to do, but honestly you will save so much time by not having to fix all the bits you messed up in 10 secs flat. Take it slowly with some decent hand tools and you will find that you are 90% of the way there without having to 'dig out' seams, or grind parting lines.

I spent a bit of time washing the body first with a cleaner to remove the release wax from the moulding process, and I scrubbed all of the parting seams - this removed all of the clay and wax.

Then I used a panel file to knock the top off the parting lines, then 80 grit sandpaper on a sanding block to finish off the lines, then I sanded the whole body with 180 grit. It took me about 90mins to go from the cleaned body to lines knocked off and body sanded. There is almost no filler required anywhere.......until i come to align the doors etc once mounted on the go-kart.

Take your time, stand back and take a look every once in a while and trust the feel of your hand caressing the curves.

[initiator]

I have recently started the body work on my MkIV Roadster. I have been in the Marine Industry for 30 years and so I am very comfortable with this part of the build, but I know that others are not.

The best advice that I can give you is......JUST STEP AWAY FROM THE POWER TOOLS!

I know that it is difficult for a guy to do, but honestly you will save so much time by not having to fix all the bits you messed up in 10 secs flat. Take it slowly with some decent hand tools and you will find that you are 90% of the way there without having to 'dig out' seams, or grind parting lines.

I spent a bit of time washing the body first with a cleaner to remove the release wax from the moulding process, and I scrubbed all of the parting seams - this removed all of the clay and wax.

The used a panel file to knock the top off the parting lines, then 80 grit sandpaper on a sanding block to finish off the lines, then I sanded the whole body with 180 grit. It took me about 90mins to go from the cleaned body to lines knocked off and body sanded. There is almost no filler required anywhere.......until i come to align the doors etc once mounted on the go-kart.

Take your time, stand back and take a look every once in a while and trust the feel of your hand caressing the curves.

Hotyacht - please start a body work thread showing your progress and approach. Your description gives me confidence I can do some of this myself. Never done body or fiberglass work before.

[Hotyacht]

Hotyacht - please start a body work thread showing your progress and approach. Your description gives me confidence I can do some of this myself. Never done body or fiberglass work before.

OK, I will try and remember to take some photos and post them. I have already started of course but the body is currently sitting with parting lines cleaned up and shell sanded so I will post some shots as is with no filler added and you can see how little work there is to be done if you slow down.

I can also show you two spots where I didnt take my own advice.......I picked up an air grinder.......and now I have to fix some divets with filler!!

[Yama-Bro]

OK, I will try and remember to take some photos and post them. I have already started of course but the body is currently sitting with parting lines cleaned up and shell sanded so I will post some shots as is with no filler added and you can see how little work there is to be done if you slow down.

I can also show you two spots where I didnt take my own advice.......I picked up an air grinder.......and now I have to fix some divets with filler!!

I'll second the body work thread request!

[Avalanche325]

I agree with Hotyacht. The most aggressive tool I used on my body was a dremel tool (and you have to be careful with that). Pros will be fine with a grinder and a DA, but you can get in trouble quickly if you don't have a feel for it.

[j.miller]

The bigger the grinder, the harsher the grit...the better I like it...but then, I like trouble.....Trouble is my middle name T....R....O....U....B....L....E.....ok, so my middle name is really "Charles".....but I was always in trouble. That's gotta count for something. Right?...da Bat

[Hotyacht]

Here are some shots from when i had completed the fairing of the parting lines.

So I knocked the tops off the gelcoat lumps with a flexible body file until they were just above the level of the surrounding body. Then I took one of J Miller's favourite tools - the Holey-Terror Sanding Block - wrapped it in 80 grit sandpaper and dry sanded down to the surrounding area. You will see that I have not continued sanding below this even when there are still imperfections - you need to judge when to stop, balance the sanding vs. the filling so that you maintain the correct body form. I find that feeling with your hand is the best guide for the shape.

The gelcoat is hard, so it is better to leave it intact if you can, it is much tougher than paint, although it has no structural value - that is the glass laminate beneath, and you should sand and damage this as little as possible. I got impatient in the corners at the front of the guard flares.....I was getting tired, and stupidly picked up the air grinder and you can see some gouges that I have to now fix - last photo. But apart from these you can see that the parting lines have come up pretty well, no deep trenches required, just a fair number of pinholes, and then a light skim of filler. The worst area on my car body is around the fuel filler recess where there are a few voids that need filling to build up the edges, but nothing serious or unsound structurally.

I am not a pro, not a painter, but as I said I have had a lot of experience owning small boats and working as a designer in the marine industry, and I have learned to take things easy and to try not to cause myself more work than is necessary. As far as body threads, there are plenty of them on here already and masses of great advice from far more experienced hands, like da Bat!

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