Balsa nose cones

I have gotten excellent results using a sanding sealer sold in woodworking stores. It is a lacquer product by Behlen. It goes on well, dries fairly quickly and sands well. Once that has dried a couple of days, I follow up with Plastikote spot filling sandable primer to show up remaining surface defects. The primer is also a lacquer product. Any remaining dings get filled with the red lacquer putty. I think it's Bondo, but any brand would work. The key thing is that everything is lacquer-based so there are no compatibility issues. After a final coat of primer, I wait a couple of days and paint. I've used Plastikote lacquer (auto parts store), Testors plastic enamel, and Krylon with no problems. It is essential that you let each "layer" (sealer, primer, color) dry thoroughly before going on to the next and you should sand with 400 grit paper between coats. This process works on model rockets up through high power.

Larry

"a.hornsbyiii" wrote:

could try some glass filled epoxy if you're a little daring... however wait like at least a full day before sanding (better if you wait some more) and leave it somewhere hot. Otherwise the thing will clog up sandpapers like mad. Those polyfiber superfil is good as well since its very sandable and light (if desirable) then you can prime it with something like BINS or something like that... They are shallac but are used regularly by guitar builders who paint them with nitrocellouse lacquer so there no problem with compatibility. If you use behlen lacquer sealer just know that since balsa is open-grained, its going to take quite a bit of sealer to fill the pores completely, so use something solid like mentioned before, or if you want something that can be purchased from HW stores, try those grain fillers or wood putty thinned down slightly. Then sanding sealer and primer. The carpenter's waterbased filler also works well and it's non-toxic, however the downside is that it does not dry as hard as the oil based stuff but the plus side is that it does dry a LOT faster than oil based.

Ever considered turning nosecone out of non-balsa hardwood like ash/alder/walnut? if its small rockets the weight may actually make the rocket more stable and still not enough to make it too heavy... not to mention they are much more durable as well.

I've had good results with sanding sealer, but it seems to take 2-3 coats and quite a lot of sanding.

I've also had good results with finishing epoxy. In some cases a single coat and little sanding.

I take all my cones and coat them with a slightly diluted yellow glue solution. Just sand, brush it on and let dry. then sand as usual.

I prefer Balsa Fillercoat to Sanding Sealer for balsa.

-Fred Shecter NAR 20117

For lacquer-based products, balsa fillercoat (dope with various powdered solids) is the preferred filler - sanding sealer is something else. Fillercoat has a lot more "body" and thus fills faster. Nothing special about it - people have been making it from clear dope for 75 years. It's hard to beat clear dope and corn starch. Clear dope and talcum powder is more common, but the adhesion to talc is not nearly as good as corn starch. Dope and zinc stearate is even better, but not enough to justify going out and finding it, when you can get corn starch at Safeway for darn close to free.

All lacquer-based products have a common shortcoming - they shrink over very long periods of time. You can apply and sand 4 coats in a day. But it you subsequently paint over it, that nice level surface will start showing the grain as the filler continues to shrink over the next

20 years! That's why models that are built for good finishes are generally not finished with filler right on balsa. First, apply tissue (Jap tissue, or silkspan, or silk), then fill/seal *that*. And, most importantly, let the stuff set up for a while before you sand it. Obviously, most of the shronk occurs right away - from a few days to several weeks, depending on the material. SIG Nitrate may only take a few days, Brodak is more on the order of a week, and SIG Butyrate takes weeks and weeks even in hot conditions.

Synthetic materials (like catalyzed automotive fillers) are much more stable and have greatly reduced shrink characteristics.

Brett

I just finished an Estes X-Ray clone using a balsa nose cone from BMS. I coated the entire nose cone with thin CA glue, a little at the time so it soaked in, sanded, and applied a coat of medium CA. After sanding it looks quite good.

John

I herd something about that once. They used thin CA and a rag. Put the nose cone in a drill put CA on the nose cone and just spun it till the CA took on a glossy finish. Adding more CA as needed to not let the rag stick to the piece.

Can this be an option as well?

John

It might have been a post I made, although the idea is hardly unique. This works like a charm, and results in minimal filling required. But I have never attempted it wth a cone that was pre-made. I have only tried it with the cone still on the mandrel that I used to turn it in the first place. It would take some sort of a jig to get it centered well enough to spin it true enough.

Brett

I put a screw eye in the base of the cone and simply hold the cone and turn it slowly as the CA wicks into the balsa. It takes just a little sanding to smooth over, but it works well.

John