DDK - Die Deutschen Klassiker

Please put your dirty minds away - this is serious

What do people think about Gravitex or alternative over the top of UPOL Raptor, under new (very expensive) or original bare-metalled inner and outer wings, bumpers, floors, petrol tank and any other exposed panels?

That may seem silly, or worse, to some people but please hear me out and comment accordingly:

- Raptor is very hard and brittle, but also very water-proof so great long-term protection for sheet metal - a bit like epoxy primer. Unfortunately, it has been shown to chip or crack reasonably easily, and especially if its adhesion is less than perfect absolutely everywhere, which cannot be guaranteed. Chips and cracks let moisture in before we know it, and we all know what happens then!

- Gravitex is soft and flexible so less susceptible to chips and no cracking, but can still get damaged quite easily by road debris and MOT garages, and proven not to be very good long-term moisture barrier even when undamaged. Of course, you can and probably should have epoxy primer under it to solve the moisture issue, but that solution is still unlikely to give decades of protection like the original underseal did.

But Gravitex over primer over Raptor over (ideally epoxy) primer??? Mmm, Gravitex protecting Raptor - best of both worlds?

OK, bit of extra weight and an extra ££ per panel but that's nothing compared to the ££££ per new wing bought or restored, fitted and painted....

Other equivalent products, wax protection, body coloured paint/overspray and wheel arch linings all play into the equation for the best protection too.

What do you think of this proposal or what protection options would you go with please?

Weld-through zinc primer inside all seams and box sections
Epoxy primer
Seam seal everywhere (including the bits that the factory didn't do - messy like the factory where appropriate, tidy elsewhere)
Thorough covering of nice durable modern paint everywhere, inc underside and interior.
Gravitex-style underseal if you want factory finish, 3M "bag seal" if less bothered
Cavity wax everywhere, including drilling a few extra access holes (hidden by interior trim) to make sure the kidney bowls etc are fully protected.

and, most importantly of all....
Dehumidified garage!
(Seriously, on a less well protected car I own which has the odd bit of bare metal showing, I find that it just doesn't rust if you keep the humidity low. It can't - chemistry says so).

It should work…

I’ve gone bare/2k epoxy/Raptor for the complete underside and under the wings.

I’m planning just to keep an eye on it and as it’s black I can touch it in really easily.

Where I had to patch my largely original 1970 'underseal' I used 3M bag seal. You would be hard pushed to tell the difference between the 3M product and the original especially after a bit of road dirt has made its presence felt. On bare metal epoxy primer or rust bullet. As Richard said plenty of cavity wax.

If the panel has been 2k epoxy primed, a thin coat of 2k inderseal is fine.Throwing loads of thick heavy underseal,is not neccessary.Modern coatings are far superior to those offered OEM 50 years ago.Plus its easier to see any possible breeches in the finish.
We all use weld through primer,however it will get burnt.I dont like any thick undersealing.It just creates areas where mud and road stuff,can accumulate then it gets damp and you know the rest.
If you want to get into box sections and between the lower edges of welded panels,id forget waxoyl type coatings and use a metal converter/primer such as vatcan.Its very light and will seep into every crevice.Any rust will become inert and any bare areas primed.

Some interesting and noticeably different ideas and points of view here, and a few products that I was not aware of - much appreciated though - choices choices!!

The main reason that I was interested in Raptor 2k underseal was because it is tintable (beige), and allows to recreate something that resembles the original mix of painted and unpainted beige-ish underseal, both for patching up existing underseal, and under new wings. As I said, I just worry that it might be too brittle, and I might not spot chips or cracks until the damage is done... I get the impression that it also sprays on really rough like sandpaper unless you put it on heavy

Those other products, 3M bag, Wurth aerosol version, Gravitex, although probably great or good enough esp. over epoxy primer are just the wrong colour for patching up existing underseal, if you want that original beige (of course, still difficult or impossible to match the road-worn original underseal). I didn't think about this when I suggested Gravitex (grey or black) over Raptor. I don't think these other products can be tinted...

Under my four, yes four, new wings, I am swaying towards roller brushing on beige-ish tinted Raptor, which when roller'd lays much flatter than spraying - I want it relatively smooth and light-coloured so that I can spot issues easily and can clean it easily... (by hand - I dont let pressure washers near my classic cars).

For the inner wings and floor sections that need patching to match the original underseal, tinted Raptor sprayed on heavy to get a similar to original texture...

Thanks again, and further suggestions/comments all welcome!

Couple of other thoughts...
Depending on your specific situation (model year's ratio of black vs beige, amount of original beige you are trying to retain and blend in with) don't forget that bag seal etc can all be over-painted. It's not beyond the realms of possibility to go with (say) gravitex grey for texture, beige paint to your own colour choice, then black paint (factory style, coverage varies by model year).

Re thin stuff inside box sections and to creep into seams - I wouldn't say forget cavity wax, but I would say that, following wax, using something really thin and creepy is a good idea. Personally I like ACF50 (also very good on exposed metal eg engine cases).

Hi, The Raptor isn’t rough, and it’s slightly squishy to the touch. With the supplied gun you can’t help but put it on with a decent thickness.

This is the inside of one of my front wings, probably about as light a coat you can do.




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The tint definitely works well with the Raptor, this was my Sons Honda

And once it’s back from paint is going to get injected absolutely bloody everywhere! Thin as possible, rust converting, waxy, you name it, it’s going to get pumped in.

Gary71 wrote:Hi, The Raptor isn’t rough, and it’s slightly squishy to the touch. With the supplied gun you can’t help but put it on with a decent thickness.

This is the inside of one of my front wings, probably about as light a coat you can do.




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Well, you can always use a normal spray gun with a primer tip, and thin it.Adjusting the air pressure,distance and speed will get a finer finish,if so required.However,I think your past that decision Gary!

I’m sure you can put it on thin if you really want, but that kind of negates the point of it

inaglasshouse wrote:Couple of other thoughts...
Depending on your specific situation (model year's ratio of black vs beige, amount of original beige you are trying to retain and blend in with) don't forget that bag seal etc can all be over-painted. It's not beyond the realms of possibility to go with (say) gravitex grey for texture, beige paint to your own colour choice, then black paint (factory style, coverage varies by model year).

Re thin stuff inside box sections and to creep into seams - I wouldn't say forget cavity wax, but I would say that, following wax, using something really thin and creepy is a good idea. Personally I like ACF50 (also very good on exposed metal eg engine cases).

Great suggestion to paint the underseal beige - I didnt thing of that.

Bilt Hamber Dynax s50 is an excellent thin and creepy cavity wax (I wrote a post about it here: https://www.ddk-online.com/phpBB2/viewt ... ax#p623147)

Gary71 wrote:I’m sure you can put it on thin if you really want, but that kind of negates the point of it

I gather that Raptor goes on very smooth with a roller, but not too thin, especially if you use a smooth roller rather than the Raptor roller (which is designed to give a bit more texture).

Can't thin of any downsides to using a roller (or probably many rollers) other than it goes off quickly so you have to mix less and work fast.

I haven't tried this.... yet - anyone tried it, any issues?

I dont know what Coop rear wings are like, but on Targa rear wings there is a very difficult to get to area between the inner and outer rear wings (adjacent to the top corners of the engine lid) - this will either have to be either partially pre-Raptored before fitting the wing (to avoid weld areas) and abraded for finishing it the undersealing when fitted, with a long (bendy) brush, or just abraded and Raptor'd after fitting with said brush....

deano wrote: Great suggestion to paint the underseal beige - I didnt thing of that.

I did that, in fact, on my shell. Or rather my painter did.
Being a rather lovely chap, he was quite tolerant of the part where I had him spray out various test colours of beigey-grey, to see which one I thought looked most authentic... although at one point he did suggest I should cover them in mud and lie on the floor looking up at them for the full effect, which might possibly have been a p*ss-take

Some relevant pics from my resto website:
https://www.safetycolours.com/porsche-9 ... shed-shell