Quantcast

Spot filling - plastic nose cones

The Rocketry Forum

Help Support The Rocketry Forum:

MarkII

Well-Known Member
Joined
Jan 18, 2009
Messages
8,212
Reaction score
9
Please excuse the basic nature of this question. I'm primarily a balsa nose cone guy, so this is uncharted territory for me. What would be a good product or technique to use to fill in the gaps in the seam on a plastic nose cone and smooth it out? (Estes Fat Boy nc, to be exact.)

On a remotely related matter: Squadron Green putty vs. White putty - what's the difference? (And don't just say that it's the color... :rolleyes: )

Thanks in advance.

MarkII
 

jj94

Well-Known Member
Joined
Jan 18, 2009
Messages
3,980
Reaction score
0
I do the opposite. I actually sand away the seam. I sand away most of it and then use normal FnF or wood filler and fill the rest of the seam.
 

MarkM

Well-Known Member
Joined
Jan 18, 2009
Messages
2,197
Reaction score
1
I use Bondo spot filling putty to even out the seams and fill any imperfections.
 

RangerStl

Well-Known Member
Joined
Jan 17, 2009
Messages
1,080
Reaction score
1
Please excuse the basic nature of this question. I'm primarily a balsa nose cone guy, so this is uncharted territory for me. What would be a good product or technique to use to fill in the gaps in the seam on a plastic nose cone and smooth it out? (Estes Fat Boy nc, to be exact.)

On a remotely related matter: Squadron Green putty vs. White putty - what's the difference? (And don't just say that it's the color... :rolleyes: )

Thanks in advance.

MarkII
MarkII;

I'm sorry, but I think the only difference besides the color is that the green stuff has *slightly* larger granules. They're 2 different colors so you can see them on different color plastics and if you make a couple different fill/sand passes.

Fill once with the green, let dry and sand. then go back with white and let dry and sand. This is often necessary when filling larger divots because the stuff shrinks a little as it dries. If it's too thick it even cracks. If you alternate colors you can see your applications easier.

N
 

dr wogz

Fly caster
Joined
Feb 5, 2009
Messages
5,496
Reaction score
805
Location
Land of Poutine!
Pure speculation here..

But I beleive colour too. Green because then you can see where it is put, and where it is filling after sanding (identifiing the low points). So you know you havent sanded it all off!!

I'd steer away form "Bondo" because it has acetone in it, and that can weaken the plastic.
 

RangerStl

Well-Known Member
Joined
Jan 17, 2009
Messages
1,080
Reaction score
1
The Squadron stuff also has Toluene, Acetone, MEK and some other stuff to keep the binders disolved and so it bites into the plastic. Without that stuff (like if it was water-soluble), it would dry up and immediately fine off the plastic surface. You are right, though; apply it thin to keep it from shrinking and so it doesn't soften the underlying plastic.

N
 

Pem Tech

Well-Known Member
Joined
Jan 20, 2009
Messages
4,394
Reaction score
14
I do the opposite. I actually sand away the seam. I sand away most of it and then use normal FnF or wood filler and fill the rest of the seam.
Like-wise here....
Sand the devil of the thing and use wood filler to cover any remaining evidence. SUprisingly, the wood filler holds to the plastic pretty well.
Have used BONDO as well, but the FNF gets the knod because it is water soluable and doesn't have to be mixed.
:2:
 

MarkII

Well-Known Member
Joined
Jan 18, 2009
Messages
8,212
Reaction score
9
Thanks for all of the suggestions. I did plan to sand the seam down as much as I could, but there are little gaps here and there, and I wanted to get it all evened out. I had thought about using FNF, but I didn't think it would stick well enough or be hard enough. I do have some Aeropoxy Lightweight Filler, which I have used with much success on balsa parts. It is a bit pricey though, so I only use it for major dings and salvage projects. (And for awhile, I forgot that I even had it. :blush: )

I used some Squadron Green Putty for the first time last fall to fix some spots on styrene parts on the Saturn 1B that I was building for the Apollo 7 Celebration. I was a bit dismayed at how soft and crumbly it was when I first applied it, but after it had enough time to cure really well (about 24 hours), it performed OK and did what I needed it to do. (Can't ask for much more than that from any product, actually.) It didn't stick all that easily to the styrene at first, which is why I wondered whether the white putty, and not the green, was more appropriate for plastic. Now I can't even find that tube of Squadron Green - maybe I tossed it. :rolleyes: (Nah, that couldn't be it; I never toss anything...)

I thought about using Bondo, too. I was worried that it might cure too hard for the styrene (making it difficult to sand without damaging the plastic). I have never actually used Bondo yet, so I didn't actually know what it was like to work with. The hardness issue was why I rejected another idea that I had: spot filling with epoxy cut with microballoons.

All of your suggestions are telling me that this problem isn't as big of an issue to resolve as I thought at first, and that there is more than one way to skin a nose cone. Thanks so much.

MarkII
 
Top