Pinewood Derby - Polyurethane as Wood Sealer?

Seems that when the weight is in the back, the car is more likely to jump out of it's lane. That's my experience.

I have seen instances where the weight is too far back, with all the weight put behind the rear axles. This will cause the car to pop wheelies when it gets to the flat portion of the track. Then the car can jump lanes, as you describe.

From what I've read, you don't want the front-rear cg to be any further back than about 5/8" in front of the rear axle.

No, I know the difference. If cars are jumping lanes and you have to build the cars opposite of established successful method something ain't right. Bumpy track, strips not straight, etc.
I hadn't thought of that.
 
Going back to the original question, we don't know if you are talking about acrylic/latex water based products and/or solvent based products. Painting with a broad brush/generalities, with top coats it is generally safe to put a latex product over oil based, but not vice-versa due to the differing expansion/contraction properties (I hope Demarpaint agrees?). This might not apply to primer/sealers because they are built different than top coats (resins, pigment, etc.).

If I were to try your method, I would thin the (assumed solvent based) polyurethane about 50:50 with mineral spirits and wipe it on with a rag. It will penetrate and seal the wood. It might raise some "fuzzies", but it is always recommended to lightly sand the sealer/primer (maybe tack rag) prior to top coating. You could force dry the car in the oven (not so hot that pine resin comes to the surface).

Is the top coat going to be rattle can?
 
Last edited:
Going back to the original question, we don't know if you are talking about acrylic/latex water based products and/or solvent based products. Painting with a broad brush/generalities, with top coats it is generally safe to put a latex product over oil based, but not vice-versa due to the differing expansion/contraction properties (I hope Demarpaint agrees?). This might not apply to primer/sealers because they are built different than top coats (resins, pigment, etc.).

If I were to try your method, I would thin the (assumed solvent based) polyurethane about 50:50 with mineral spirits and wipe it on with a rag. It will penetrate and seal the wood. It might raise some "fuzzies", but it is always recommended to lightly sand the sealer/primer (maybe tack rag) prior to top coating. You could force dry the car in the oven (not so hot that pine resin comes to the surface).

Is the top coat going to be rattle can?
The polyurethane is a solvent based rattle can, so thinning it out with mineral spirits isn't an option. Otherwise, that would have been a good option. The paint is also a rattle can. Duplicolor automotive acrylic enamel touch up paint.

I agree with sanding between coats. My goal is to end up with a show car finish. Or, as close as an amateur like me can get.
 
I would use water based Poly dries very quick and durable. I have painted over it with latex paint with no adhesion issues.
 
Interesting, it was always a thing to keep the weight as far back as possible, still seems to be:
Do you have a secret nobody else knows?


Going to get mixed reaction to everyone gets a prize. Lots of debate.
Mark rober on YouTube has a video all about this. He found a scientist that performed alot of calculations to come up with an unbeatable pinewood derby car.
 
I have seen instances where the weight is too far back, with all the weight put behind the rear axles. This will cause the car to pop wheelies when it gets to the flat portion of the track. Then the car can jump lanes, as you describe.

From what I've read, you don't want the front-rear cg to be any further back than about 5/8" in front of the rear axle.


I hadn't thought of that.
You want the weight as far back as possible. The sweet spot is .9 to 1.3 inches in front of the axle.
 
Mark rober on YouTube has a video all about this. He found a scientist that performed alot of calculations to come up with an unbeatable pinewood derby car.
I found Mark's video and watched it. Great information, and presented super clearly. I had passed over this video before. So glad you recommended it.
 
Back
Top