Chassis Painting

[GS guy]

Have a question about sanding scratch size for painting my chassis. I'm gathering up the supplies now for a fun summer of sanding and painting!

So my chassis is all tubular with a mix of rectangular and round tube. It's been in a mostly bare steel state for years as I worked out the details, with surprisingly not too much surface rust forming over that time.
I'm planning to use a DTM epoxy primer, and overcoat with Kirker (aka: Summit/Eastwood) charcoal gray metallic urethane single stage paint.

The primer spec sheet says to prepare the surface with an 80 grit DA finish. The paint sheet says to scuff the surface with 400-600 grit. That's a BIG jump in scratch sizes! I'm not sure how well the primer will "fill" those 80g scratches and because of all the surface irregularities, I really don't want to be sanding the whole thing down and re-coating multiple times with ever finer surface finish before painting. This is a chassis after all - not the primo finish I'd want on the bodywork.
The bare metal prep will probably be a combination of Clean and Strip discs on my angle grinder, some minor sand blasting where I can't get the discs in there, and some hand sanding with 80g paper. I'll shoot the primer over this and plan on 2 or 3 nice coats. Then I guess I'll need to at least sand some of the more exposed areas like the roll bar with something finer (320?) and if necessary re-shoot with a final primer coat before laying down the top coat.
I just don't want the heavier scratches showing through the finish, especially after drying for several months.
Advise?
Thanks, Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[jspbtown]

2 or 3 coats or epoxy primer will do a very good amount of filling (although I never sprayed the primer you are using).

Any reason why you are separating the priming from the finish coats? I think its best to shoot them all at once to get a good chemical bond versus relying on a mechanical bond via scuffing.

[GS guy]

Jeff - hoping to stay in the top-coat window (5 days or so) so I don't have to sand for adhesion. I do want to clean up the welds on the roll-bar with some filler to blend them in a little. Otherwise, I'd only be sanding the primer to sand out any heavier scratches showing through or clean up any nits in the primer finish.
Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[jspbtown]

Ok..got ya. I just read your post wrong. To me it seemed like you wee going to prime and then not top coat for a long period. I mis-read.


I think 80 grit on a DA is fine. Now the hand sanded sections might be a little different. I have found that the same grit on a DA and hand sanding don't really produce the same results. DA sanding produces a much finer scratch than a hand sanding.

Even with that caveat I think 2-3 coats of a good epoxy are going to fill just fine.

[rugblaster]

I think what they are saying is DA sand with 80 grit on the bare metal, not sanding the primer coats with 80 grit....do that with the 320 or 400. I don't know what your chassis looks like, but if you use a sanding primer, you will have to sand the whole thing not just parts of it.

You might want to hi build the part you care about sanding smooth and use a non sanding, etch primer on the rest of it.

[joescoolcustoms]

I have done several chassis and get very good results with just sand blasting the entire chassis. I then blow the dust off, wipe the last bit and spray Summit Chassis Shield. Comes in either semi or gloss black.

I do the same for my bumpers, nerf bars, roll cages.

The Chassis shield covers nicely,evenly and leaves a great surface for top coating the next day.

Blasted to white metal:

Blasted, chassis shield, then final top coat. No sanding.

_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[GS guy]

Saw your car at Carlisle Joe, I'm hoping I can get a similar finish! That is a great looking buggy. I don't have ready access to sandblasting here, and also have panel rivet holes in many of the tubes i don't want sand getting into!

Rugblaster - agreed on the overall finish. I think the DA winds up producing a smoother finish than hand sanding would - and primarily intended on flatter body panels. Once the primer is down, if you miss the re-coat window it needs to get a 180 grit sand all over before priming again.

If I can, I'm hoping to just prime with a few coats, then the next day shoot the finish coats. If necessary, I could lightly sand some areas (again like the exposed roll bar) to get a slightly smoother finish on those areas most visible with the body on.
I guess it depends on how the primer looks the next day. I definitely don't want to get into applying and sanding multiple primer coats - like you would on the bodywork.

I guess I'll be doing a test section in the process. I first need to prime several areas - bottom of floor tubes and front bulkhead - where I'll be riveting and bonding aluminum panels in place, The adhesive takes a full week to dry, so only want to prime areas that will be covered up by the panels. I'll be able to see the finish in those areas the next day and make a finish call before I attach the panels. Once the panels are installed and set-up, then the chassis will get the full prime and paint process all over, hopefully over the course of a few days.

Thanks for the tips!
Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[rugblaster]

That is a COOL chassis.

[joescoolcustoms]

Before I got the tools to sand blast, I used Scotch pads. They take the pickling off the steel, but don't leave the scratches in the metal surface. It is a lot of hand work, just like sanding.

Then I picked up an angle grinder, (small, air, that uses the 2 inch rol-loc pads) and bought the scotch pads from Summit Racing. Wow! Knocked out a lot of hand work, sped the process up by 10 fold, and still did not leave scratches.

BTW, hope to see you in a 1 1/2 month's at Carlisle again! Will be my second year, and may have 3 to 5 buggy's I have built there.
_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[GS guy]

I figured on the Scotch pads to remove the surface rust - then I'll see about how to get the scratch-finish I (think) I need. WHile stocking up on supplies I picked up a bunch of Rol-lock sanding discs in various, fairly coarse, grades and couple of sizes. They might come in handy for this?
One of my favorite tools is the ultra-cheap HF angle grinder. I've got lots of coarse flap-wheels I use on it for shaping metal and prepping for welding. I know these will give a good "tooth", but don't do too great for keeping the surface flat. I'm sure some hand sanding on a flexible pad will also come into play.

I usually hit Carlisle on Saturday Joe - it's a couple hour ride up from Balto and easy day trip. Just wishing I had a buggy to show off!
Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[GS guy]

FWIW, here's what I'm up against!

I've added a lot more brackets and bits since this pic from the first full suspension mock-up (a couple of years ago). Man - time sure flies when you don't seem to be getting much done!
Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[vwracerdave]

I would very seriously consider having it powder coated.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[MacLeod Willy]

[Hot Air]

Powder coat all the way, That is to nice of a frame not too..
_________________
73' Bug
85' Porsche 911 Carrera 3.2

[GS guy]

Sorry guys - this one is getting the paint treatment. I do love PC-ing, all the suspension bits and a few other parts are powder coated.

With all the tight-tolerance mounting points, threaded holes, etc. it would take me weeks to get them all cleaned out if it were PC-ed. Plus it would be tough to get all the nooks and crannies in this chassis coated well - it'll be tough enough painting it!

Once primed, I'm thinking I might do the floor pan pieces with U-Pol Raptor. Maybe a little tougher finish than the poly paint, which is supposed to be pretty tough already.

Wonder how it would accept the paint color of the rest of the chassis? How does that work anyway, just add some paint without the activator to the U-Pol clear?
Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[didget69]

I'd go with Paint, as it's easier to work with on later frame mods or repairs. Paint frame light gray, so that weld cracks or frame cracks are easily located.

Bryan
_________________
I never found the need to impress people with any mechanic certifications, trophies or track wins... unless it was for Mom to post on the refrigerator door.

[joescoolcustoms]

I am a paint guy, but I have had a chassis PC'ed.

The Coater puts heat resistant silicone plugs in the threaded holes and no need to clean them up afterwards, just a touch of anti-seize and go. For getting into nooks and tight areas, the coater PC's twice. Heats it the first time, pulls it out hot, coat a second time and back in the oven. The second coat pulls back into the welded and tight areas better on the second coat due to any exposed areas attract the paint where as the coated areas do not.

For the Raptor tinted, I use it too. Very tough if the surface is prepped properly. Only use Urethane paint to add to it. No paint reducer or activator, just the paint. About 9 to 10 ounces paint per liter of bed liner. The Bed Liner activator sets it up. The Urethane paint adds UV protection to the bed liner.
_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[crack monkey]

Hit it with Mastersieries paint. It is great stuff.

That is a great looking chassis

[fiaroadster]

GS guy, that is truly a great looking chassis. This the way I want to go. More info and pictures please! Wheel base , engine and trans, front suspension?

[GS guy]

fiaroadster - This car has been a "work in progress" for much longer than I care to admit! I've decided this summer I "have" to get the chassis painted and at least make some serious progress on getting - at least the rolling chassis - assembled!
Here's the short version - started out as a Deserter GS basket case, original mid-engine chassis, GT bodywork. Original drivetrain was toast, so my vision became to re-work it into a more suitable road car - remember the GS was built primarily as a super lightweight track car. Along the way front and rear suspensions underwent major surgery, along with the drive-train, general chassis (to support the suspension changes), brakes - just about everything!

The painting of this chassis will be the beginning of my "build" thread - as it should start going together pretty quickly after that. Nobody would have the patience to sit through how long it's really taken!
Here's a close-up of the front suspension:

Jeff
_________________
70's vintage Deserter GS buggy - undergoing transformation to Super GS!