Paint compatibility! Duplicolor + Water based Acrylic

[mpflies2]

Hi!

Brand new to pinewood derby. Making 3 cars. A trans-am for myself, raptor for my oldest son (bear), and a Dr. Robotnik car for my youngest (tiger).

Where I’m at in this process:

Cut cars on scroll saw. Glue up for fenders is finished. Sanded with 150/220/400 grit sand paper. Used bondo wood filler on the trans am for some gap filling. Tried to paint with Krylon 2x paint and primer assuming it you know… primed and painted. Quickly realized it looked like junk. Sanded it all down. Used 3x coats of shellac with light sanding between coats. Switched to duplicolor after reading a slew of forum posts here. Primed with diplocolor filler/primer.

Thats where I’m at.

The question I have before I proceed.

1) How bad did I mess up not drilling weight holes before starting the paint process.

2) knowing that we all want to paint a bunch of small details (trans am screaming chicken, head lights license plate, windshields, pin striping, raptor eyes and skin texture, robotnik computer panels)… I ordered Arteza water based acrylic paints. With that said, is it safe to add these above the duplicolor topcoat and will the subsequent duplicolor clear gloss be a problem with water based acrylic? If so would shellac work as a final sealant/gloss coat as well?

3) what’s the best way to remove weight from the front of the car at this point? I don’t want to damage the look and don’t care if I actually win anything but I’d like to give it an honest effort. Thinking of removing some wood by cutting out some pockets about 1/2” from front axle. Then drilling holes just forward of rear axles for tungsten weights. Ideally making it not look bad in the process. Maybe a Forstner bit on drill press while car sits inverted on some cloth?

Sorry for the long post and multiple questions but primarily I’m hoping to answer the paint question. I’ve spent more on this derby than I care to admit…

Thanks in advance.


Going to attempt to put some pics in the post but not exactly sure how. lol. The removal of all the paint and subsequent attempt.

[exoray]

Maybe a Forstner bit on drill press while car sits inverted on some cloth?

I have done this many times to finished cars, now I try to plan a little further ahead and router out the bottom before I start whacking the block...

1) How bad did I mess up not drilling weight holes before starting the paint process.

Generally not ideal, but you can make it work, drill, router or chisel out from the bottom carefully...

I ordered Arteza water based acrylic paints. With that said, is it safe to add these above the duplicolor topcoat and will the subsequent duplicolor clear gloss be a problem with water based acrylic?

As long as you give the artist acrylics plenty of time to fully dry, you should have no issues with pretty much any rattle can paint... But, do a quick test on a scrap board to be 100% sure...

If so would shellac work as a final sealant/gloss coat as well?

I would personally avoid shellac as a top coat (I love shellac as a base coat and sanding sealer) it will yellow/amber out with age pretty quickly and you might have issues down the road if someone say decides to say wipe down the car with Windex as ammonia will eat away curred shellac...

I have been using clear acrylic for my clear coats as of late if I mix paints...

If you want the kids to be more involved in the painting, get a jug of Mod Podge gloss and have them sponge or brush on a clear coat with that... Yes it will have brush strokes, but the kids are more involved and you don't have to deal with the learning curve of rattle cans...

My son hates sanding and painting, so this year he went for simple and leaned heavily on the 3D printer, and just a straight-up block of wood that I helped him 'paper wrapped' and then he brushed on two clear coats of Mod Podge and was actually proud of the brush strokes, proclaiming that it made it look like it was hand painted... BTW if you ever want to try a paper wrap, you need to use acrylic clear coat on both sides of the paper or else it wrinkles, we stuck it to the block with Mod Podge and then clear coated it with Modge Podge twice in the same day, made for a quick build...

[whodathunkit]

mpflies2,
You guy's have got some good looking car builds taking place .

And I've been in your shoes many times.. as far as Paint compatibility go's with water base acrylic and krylon 2x spray paints.
(Some paint types just don't mix well together.) For water base acrylic paints I'll just use them with out spraying any primer on the car.
sometime i put down several coats and when it's dry ( at least for 24 hours or overnight.)
Ill use the krylon 2x clear spray paint for the gloss coat.

Image of a hummer my son and I did with Krylon spray paints.. and a few burnt ember water base model paints.


I know you said that you've invested far more then you care to share..

There are ways to make your own paint stands.. like wooden stick handles with a two way dowl screw in them to make a handle that also screws to the bottom side of the car to hold it
while painting with spray paints.. and finding a way to hold it while the car dry's. like clamped in a vise.. or the wooden handle stuck in a hole cut out in a cardboard box.
https://cheapstairparts.com/shop/dowel- ... KsQAvD_BwE
Or setting the car on top of a paper cup to paint it and let dry.

The paint stand system seen in the image above that my son and I are using is from Derby Guys .
It's just one of paint system tools I've invested in over the years for spray painting derby cars with.
There very handy for holding the car while spray painting color coats or clear coats It gives you a handle and a rack system to set the car on while it's drying.
The red metal one seen in the next image.. is of the very first proto type paint system that was also offered by Derby Guys before they changed it over to the plastic handle.

https://www.youtube.com/watch?v=crG1n80p9Eo


As long as your cars are in the Dupli -color primer and they have dried for a day .. id say your safe to work on hollowing out wood weight and the weight pockets .
And that if any touch ups are need to your cars primer paint after the wood removal stages and weight pockets are done.
That it's far better to do while you are still in the primer stages of your paint jobs.. and before moving on into the painting stages of your cars.

Hope you'll keep sharing the photos of the car builds as they progress guy's and best of luck with you're paint jobs.

[FatSebastian]

Maybe a Forstner bit on drill press while car sits inverted on some cloth?

I have done this many times to finished cars...

It is not uncommon that people need help with drilling underside holes at our car-building workshops. It can really help if you still have the scrap of the wood that was cut off the top (if it came off in one piece); it can make for an inverse car-shaped cradle into which the body can be turned over and leveled for milling out with the Forstner bit. If already painted, you can try putting a washcloth between the body and the cradle of scrap wood...

[mpflies2]

If so would shellac work as a final sealant/gloss coat as well?

I would personally avoid shellac as a top coat (I love shellac as a base coat and sanding sealer) it will yellow/amber out with age pretty quickly and you might have issues down the road if someone say decides to say wipe down the car with Windex as ammonia will eat away curred shellac...

I have been using clear acrylic for my clear coats as of late if I mix paints...

If you want the kids to be more involved in the painting, get a jug of Mod Podge gloss and have them sponge or brush on a clear coat with that... Yes it will have brush strokes, but the kids are more involved and you don't have to deal with the learning curve of rattle cans...

My son hates sanding and painting, so this year he went for simple and leaned heavily on the 3D printer, and just a straight-up block of wood that I helped him 'paper wrapped' and then he brushed on two clear coats of Mod Podge and was actually proud of the brush strokes, proclaiming that it made it look like it was hand painted... BTW if you ever want to try a paper wrap, you need to use acrylic clear coat on both sides of the paper or else it wrinkles, we stuck it to the block with Mod Podge and then clear coated it with Modge Podge twice in the same day, made for a quick build...

Thank you for the info! I like the idea of modge podge for the kids cars. They'll be doing the majority of painting after I apply the primer/base coat. Doesn't need to "look perfect." I've already spent tons of hours cutting, prepping, priming etc. I had them help me with the design portion. They helped me with the initial sanding with the 3 tiers of sand paper but I went back to make it much smoother for them. They just don't have the elbow grease just yet to get it super smooth but I wanted for them to participate. They'll paint the details (I may help mask off certain areas of the cars to guide in the design idea that they say they want). But yea I would like them to get a feel for as many steps as possible so the final clear would be good for them to do using modge.

3D printer is high on my list as it supplements like every one of my many hobbies. Looking at a Bambu P1S.

[mpflies2]

mpflies2,
You guy's have got some good looking car builds taking place .

And I've been in your shoes many times.. as far as Paint compatibility go's with water base acrylic and krylon 2x spray paints.
(Some paint types just don't mix well together.) For water base acrylic paints I'll just use them with out spraying any primer on the car.
sometime i put down several coats and when it's dry ( at least for 24 hours or overnight.)
Ill use the krylon 2x clear spray paint for the gloss coat.

Thank you! I'm excited about how they turned out so far. I used to do some scroll saw work so I had a handle on design and shaping both with the blade and sandpaper. Not an expert but dabbled enough to get a semi descent result.

I've got a scrap piece of wood and I'm making sure all the paints and coats play nice.

I know you said that you've invested far more then you care to share..

Yea. That's not on the kids at all. It's been an excuse to upgrade my tool collection to some extent.

I offered to get them some alternate colored wheels before we started building when we were at the scout shop. Bought a pinewood derby book I found at ollies. Had the $200 dremel kit in my amazon cart for almost 2 years. Pulled the trigger lol. Bought extra wood at hobby lobby for fenders. Sanding sealer ($21 for the cheapest can I could find). Brushes, 3x packs of sandpaper, bondo wood filler (not cheap), wood glue (2 types since I didn't like the gorilla glue... first time I'd tried it)...spray paint (4 cans of Krylon I won't end up using)... after sanding my first attempt all down, bought shellac (which I find worked much better than the sanding sealer), shellac dedicated brush, almost $90 worth of duplicolor between our 3 base colors, the primer, and the clear. Bought acrylic water based paint and brushes, tungsten weights, tube of graphite, pinstripe tape. I feel like I'm forgetting something but that's where I'm at. I'd love to buy a 3d printer as mentioned in my previous comment response above but that has to hold for a bit longer. Been on the fence for a few years.

The paint stand system seen in the image above that my son and I are using is from Derby Guys .
It's just one of paint system tools I've invested in over the years for spray painting derby cars with.
There very handy for holding the car while spray painting color coats or clear coats It gives you a handle and a rack system to set the car on while it's drying.
The red metal one seen in the next image.. is of the very first proto type paint system that was also offered by Derby Guys before they changed it over to the plastic handle.

I just used a camping tent stake that I clamp to my work bench when they're drying. drilled a hole slightly smaller than the stake in the bottom center of the cars.

As long as your cars are in the Dupli -color primer and they have dried for a day .. id say your safe to work on hollowing out wood weight and the weight pockets .
And that if any touch ups are need to your cars primer paint after the wood removal stages and weight pockets are done.
That it's far better to do while you are still in the primer stages of your paint jobs.. and before moving on into the painting stages of your cars.

Ok cool, yea I'm going to attempt it before I put the base coat on over the primer. Letting some acrylic dry on a test piece in the mean time and will attempt to clear coat it tomorrow to determine how much total cure time I need for the acrylic details.

Hope you'll keep sharing the photos of the car builds as they progress guy's and best of luck with you're paint jobs.

I will! May put a separate post in the appropriate thread. Thanks a ton!

[mpflies2]

Maybe a Forstner bit on drill press while car sits inverted on some cloth?

I have done this many times to finished cars...

It is not uncommon that people need help with drilling underside holes at our car-building workshops. It can really help if you still have the scrap of the wood that was cut off the top (if it came off in one piece); it can make for an inverse car-shaped cradle into which the body can be turned over and leveled for milling out with the Forstner bit. If already painted, you can try putting a washcloth between the body and the cradle of scrap wood...

I do have part of it but because I used a seperate piece of wood glued to the top of the original cut for the cab, then shaped it with sanding, that won't work at this stage lol. At least on my car. As for the kid's cars... yea i didn't think about it at the time and they got tossed with some other scraps unfortunately.

[exoray]

shellac dedicated brush

A lot of people recommend denatured alcohol to clean shellac, but as I said basic household ammonia destroys it, so when I use it now, I just clean it with ammonia and then a little ammonia and dish soap, super easy, just make sure it's fully rinsed and dry before next use... Soaking in ammonia will also remove cured shellac, so when I'm working on something, I put the wet brush in a plastic bag and even if I forget about it and it dries all I need to do is soak it in some ammonia to get the brush clean again...

Modge Podge also works as a kid-friendly sanding sealer, not my preferred choice over shellac or clear lacquer but I have used it before, like on the Minecraft car just to seal it down before papering it...

And 3D printers are fun, I went with a resin printer because I like the higher details, but a filament printer is on the wish list, just don't have an immediate use for it because if I want something printed on a filament printer the local library maker shop will do it for just the cost of filament weight, saves me the hassle as long as their cue isn't too backlogged...

[mpflies2]

shellac dedicated brush

A lot of people recommend denatured alcohol to clean shellac, but as I said basic household ammonia destroys it, so when I use it now, I just clean it with ammonia and then a little ammonia and dish soap, super easy, just make sure it's fully rinsed and dry before next use... Soaking in ammonia will also remove cured shellac, so when I'm working on something, I put the wet brush in a plastic bag and even if I forget about it and it dries all I need to do is soak it in some ammonia to get the brush clean again...
..

Yea I didn’t have any ammonia and I didn’t love the idea of another 30 min each way trip to the store. Did some research and several suggested soaking brush in the can of shellac would soften the brush again and I found that to be true. It worked quite well!

[mpflies2]

Hope you'll keep sharing the photos of the car builds as they progress guy's and best of luck with you're paint jobs.

I’ve got a test piece going with all the paint layers including the water-based acrylic and duplicolor clear coat and far so good.

Not the cleanest looking cutouts but it’s the bottom. Also, I took as much as I could out of the Firebird without risking punching through. Only got me under 5 oz and able to add one single 0.07oz weight near the axle. That car will have to be going for looks and not speed More photos:

[FatSebastian]

Not the cleanest looking cutouts but it’s the bottom. Also, I took as much as I could out of the Firebird without risking punching through. Only got me under 5 oz...

Because your margins are ~0.03 ounces with primer, and you still need to add paint, clear coat, decals, etc., might you need to take out just a little bit more from the bottom? Also, the official scale at check-in may read higher than yours, so it would be easier to leave it a tad underweight and add weight (e.g., a wood screw, or tungsten putty) than to remove more wood at check-in if overweight on the official scale. Just a thought...

[whodathunkit]

Looking good guys.

You’ll also want to put something over the holes to cover them up
Like clear packing tape.. this will help with drag and keep you from catching air under the car on race day.

[Loud2ns]

Looking good guys.

You’ll also want to put something over the holes to cover them up
Like clear packing tape.. this will help with drag and keep you from catching air under the car on race day.

This is the way.

Sent from my SM-G991U using Tapatalk

[mpflies2]

Race Day Today! We didn’t do great things in the speed category but we all had fun at our first derby. My youngest got 1st place for the Tigers in best in show for his Dr. Robotnik car. My older son’s raptor was super cool but with steep competition in the Bears he didn’t win anything this year but was surprisingly supportive of his brother (at least in the moment) and his other pack mates. Somehow I just inched out over an unbelievable build by my friend Steve to win 1st place with my ‘77 Pontiac Firebird Trans Am in the Outlaws. Steve built a beautiful ‘36 Chrysler Airstream C8 Convertible. I’ll post the pics here to follow up with those invested in this thread and then I’ll post pics in the car/semi-truck photos thread. Thanks for all the support for our first year!














Also. Here’s Steve’s amazingly painted Chrysler:

[whodathunkit]

mpflies2, Crew

Grate job on all the car's and congrats on your wins guys.
The Bandit one car is super cool you did a nice job.. all you guy's did Killer looking paint jobs on your cars.
(who doesn't love the craftsman ship and the look's of hand painted works of art !)
For your first year you should be proud.. the cars and the memory's are the real trophies.

Congratulations Guy's.