Feeling apprehensive - body prep!

[SpitfireIV]

So many sources, so many opinions, so many schools of thought, methods etc etc....

Phew!

Getting close to prepping (finally) the body of my '71 Spitfire, I've already done the underside, inside and the bulkhead, all of which were nerve wrecking, but, came out grand in the end. The outer body shell, the bit that's gonna be on show has me very apprehensive though, but, I'm determined to tackle it myself........whats the worst that can happen?!


I'll be using cellulose and spraying the primer with a conventional 1.8 gravity gun and color with a 1.4 LVLP gravity gun.

Question 1. A number of months back I brushed/rolled the body tub with Besa 2k epoxy, prior to this I had cleaned the whole body back to bare metal with 80 grit. I've hammered out as many little dings and dents as I could but obviously it'll still need filler work doing. I'm assuming I can just rough up the epoxy where filling is needed and apply filler on top? What would be a good grade paper to rough up the epoxy? Or perhaps a red or grey scotchbrite?

Question 2. As I already mentioned I brushed/rolled the Besa 2k epoxy primer to hold off any flash rust over the winter months, seems to have worked just fine. After I have the filler work done I'd like to be able to spray the whole tub again to seal in the filler........I'm assuming that unless I have the proper safety gear (which I dont) that spraying that stuff is a no go? As too would be brushing/rolling again as I wouldnt get a smooth/flat enough finish?


I'm sure I'll have many more questions, but those two will get me started....

 

[richie00boy]

Use a red Scotch pad as that won't cause breakthroughs but will give a good key.
Spraying epoxy with just an a1p2 rated mask is fine as there are no isocyanates.
Sounds like you are on track for a good job.

 

[the snooper]

I brushed/rolled the body tub with Besa 2k epoxy.

unless you make sure the primer is flatted perfectly smooth and any brush / roller marks completely removed, it will look hand / roller painted when you have sprayed it

 

[SpitfireIV]

Use a red Scotch pad as that won't cause breakthroughs but will give a good key.
Spraying epoxy with just an a1p2 rated mask is fine as there are no isocyanates.
Sounds like you are on track for a good job.

I hope so! This part of the project has me sweating....and I haven't even started the hard work yet! :-P

unless you make sure the primer is flatted perfectly smooth and any brush / roller marks completely removed, it will look hand / roller painted when you have sprayed it

I reckon the rolled areas are pretty smooth and I figured I'd be doing a fair bit of sanding, filling, flattening before the primer that would take care of the most of the painting marks, I guess I also assumed working the high build would have taken care of any roller/brush marks.

I picked up DA recently would you recommend I went over the whole tub and flattened it all back? There is a lot of humps and curves so I guess an interface pad(?) would be necessary, but what grade of paper?

 

[the snooper]

I hope so! This part of the project has me sweating....and I haven't even started the hard work yet! :-P



I reckon the rolled areas are pretty smooth and I figured I'd be doing a fair bit of sanding, filling, flattening before the primer that would take care of the most of the painting marks, I guess I also assumed working the high build would have taken care of any roller/brush marks.

I picked up DA recently would you recommend I went over the whole tub and flattened it all back? There is a lot of humps and curves so I guess an interface pad(?) would be necessary, but what grade of paper?

the problem is high build will build on the highs as well as the lows and will follow what ever the pattern is.

you could try an area with a block and see what its like and work out a plan from there, if it turns out that you need to flat it right back use a guide coat to be sure

 

[norsa]

guide coat, guide coat, guide coat. saves hours of guessing. DA is a useful tool but until you have used it for a long time, youll be better off finishing with a block. DA 120-180 to get your basic shape then go to your block 400 before your high build. im going to recon on filling/flatting at least 3 times on most dents, youll never do it with one fill.
Nick

 

[SpitfireIV]

Thanks for the help and info guys!

Had a closer look at the panels yesterday, and although the rolled epoxy seems smooth enough I might sand it back again in the visible areas (wings, sills, frame etc) wont be too precious with the door shuts, scuttle etc).

Thankfully the wings are 'rescued' replacement panels, just out of interest I gave them a dusting of guide coat yesterday and a quick rub, this showed up only a few minor little spots.

The bonnet is GRP and finished in 2K I believe. Has a couple of little stress cracks which I assume can be cut back and filled with Isopon P38? Was planning on buffing up the bonnet then with 400, giving it a blast of primer and then top coat.

 

[PSweeney]

I'm prepping my race car with epoxy as a base to fill on and build up primer coats. I Thinned it with 20% thinners and tried to get the final coat on wet but got some peel I gave it two coats more of epoxy and hit that with 240 on the da, then 320, then 500 both by hand. The Jawel epoxy I'm using seems to flat back nice and I imagine would spray better if you have the right gun size. I only had a 1,5mm suction feed hence the need to thin it down and knock it back with 240. If I could have got it on nicer ire on it would have flatted with 320

 

[langy]

Thanks for the help and info guys!

Had a closer look at the panels yesterday, and although the rolled epoxy seems smooth enough I might sand it back again in the visible areas (wings, sills, frame etc) wont be too precious with the door shuts, scuttle etc).

Thankfully the wings are 'rescued' replacement panels, just out of interest I gave them a dusting of guide coat yesterday and a quick rub, this showed up only a few minor little spots.

The bonnet is GRP and finished in 2K I believe. Has a couple of little stress cracks which I assume can be cut back and filled with Isopon P38? Was planning on buffing up the bonnet then with 400, giving it a blast of primer and then top coat.

Regarding the star cracks please don't just fill with filler as they will return, best way to deal with them is grind the cracks back to the mat and fill with GRP chopped mat and paste, then gelcoat (best) or thin layer of filler, best filler is Upol fantastic, P38 is hard to rub down and a bit old hat these days

 

[SpitfireIV]

Ok, I've gotten the body prep under way, have a few more questions....


- I've stripped the epoxy off for the most part with the DA (80 grit)
- Identified areas in need to filling and tapped down a few visible high spots.
- Applied filler to the more obvious areas and cut it back with 60 grit on the DA and then 80 grit block.
- Guide coated and applied more filler as necessary and sanded again.

This is the stage I'm currently at. I'm pretty happy with how the filling is going but it's time to move on. so, I'm guessing my next step is....

- Smooth off the current filler with 120 block and a light skim of stopper and sand again with 120 or 180??
- With the filling done and guidecoat check to be sure no more filling is required (I'm sure something will pop up once the primer goes on!) I plan on applying an epoxy primer to seal the lot. What would be an appropriate grade of paper to sand down the body with at this stage to prep for the primer? 180 grit or finer?

Thanks.

I've also discovered that the dense foam kneeling pads that you pick up in any cheepo pound shop make excellent sanding blocks! They're 30mm thick, quite rigid and can be cut to any shape or size on a bandsaw!!

 

[langy]

My first question would be why did you sand the epoxy off before filling ???

 

[ajlelectronics]

I was wondering that too!

 

[SpitfireIV]

I had brushed/rolled it on as a protective measure against rust over the winter months. It was a fairly thin coating and came off easily enough with a few passes of the DA. I only knocked it off the outer areas; door shuts, inner jams etc I'm just going to scuff up.

 

[langy]

I had brushed/rolled it on as a protective measure against rust over the winter months. It was a fairly thin coating and came off easily enough with a few passes of the DA. I only knocked it off the outer areas; door shuts, inner jams etc I'm just going to scuff up.

But it's the ideal surface once keyed to fill on !!!

 

[SpitfireIV]

I understand that, but like I said I had brushed/rolled it on, so, the finish wasnt great flatting it back would have removed most of it anyway, but, thats neither here nor there, it's gone now, at least from the wings.

 

[Swift&Bold]

The companies that produce epoxy coatings recommend that you apply directly to bare metal prepped to a least SP2 to get the resin to bite (their claim is that anything else used under it will let go first, allowing corrosion to creep under and along the coating), in fact they will only entertain any claims against them if applied in this way, so if you intend to epoxy again it's relevant.

Epoxy coat, filler/seam seal then epoxy again is the usual advice.
As for question 2....standby for round two!

 

[langy]

I understand that, but like I said I had brushed/rolled it on, so, the finish wasnt great flatting it back would have removed most of it anyway, but, thats neither here nor there, it's gone now, at least from the wings.

You should of put more on

 

[PSweeney]

With regards to the grits, You just need to get the primer up to 600 without removing too much material. I find it useful to guide coat each grit to ensure I've got all scratches from a previous grit. Even doing this i still miss some but it's a good visual reference where to sand and when to stop, which is important because if your anything like me you'll naturally be drawn to flatting the flat areas easy to sand rather that the difficult curves and recesses.

 

[tlovatt]

From my experience having painted a couple of restoration projects you did the right thing in sanding off anything that was brushed or applied with a roller. There is a lot of work to do in the prep and applying the colour coat is a relatively minor step after all of the prep work is done. You will be amazed what happens to a (what appears to be) near perfect bodywork once a gloss coat is added.

Do it right, do not take any short cuts and take your time. Fill as much as you can prior to a few coats of high build and rubbing down to take all of the small imperfections out and only once you are happy with the finish under some very strong lights looking down the side of panels do you start applying the colour.

Also for my vote, if the old paint on the bonnet has cracks, strip it off back to metal and paint it along with the rest of the car. I have taken shortcuts and especially when it is your pride and joy restoration you will end up having to do the work again

 

[marlinspike]

I don't want to hijack the thread, but how smooth should the primer be before you topcoat it? I am about to start sanding the filler on my repaired wheel arch. In the past when I have used small amounts of filler then primer, I have wet sanded the primer with various grades of paper until it is is very, very smooth - but I am getting the impression from this thread that the surface should actually be keyed a bit.