Finishing Balsa Nose cones

[AfterBurners]

Well I decided to pick up where I left off on my MAD COW Batray

https://www.madcowrocketry.com/Batray_Rocket_p/k-118.htm

I need some insight on some ways of finishing/sealing the nose cone. The last one I had I messed up trying to fix the defect in it so I had to order another. I was considering just masking the shoulder and applying Aero Gloss Balsa Filler as the first coat. Repeat and sand a couple times and then apply Aero Gloss Sanding Sealer. Maybe two coats or until I get the finish I want. Prime and paint.

I figure I'll stick to 320/400 grit papers and finish with 600. I don't want to sand so much as to change the shape of the cone. I know balsa is soft, which is why I want to use the finer papers.

This is how I was thinking of finishing it.

As far as the body it's primed and ready for wet sanding.

 

[JPVegh]

I like the Aerogloss products and have been using them for a long time. Before I start applying it though I try to fill the deeper imperfections with something like elmers wood filler. My technique is just like you describe, fill, sand, fill sand... until I get the finish I want then seal, lightly sand. Even with the finer sand papers it's easy to sand in a flat spot so pay close attention to what you are doing.

I've used other products and techniques over the years but I keep coming back to the Aerogloss. Maybe I just like the smell of dope or maybe I'm just an old dog who can't learn any new tricks.

 

[Massrokit]

I basiclly use diluted FNF and sand then primer, sand then primer again, sand. the FNF is used to fill the balsa grain Aero gloss will crack over period of time since it is continiously drying out.

 

[JPVegh]

I have to say in the almost thirty years of using Aerogloss products I've never had it crack on me. I'm not a huge fan of using diluted FNF on balsa because of the potential for warping and swelling but I know there are those who swear by it. FNF is certainly a cheaper option than Aerogloss and I do use it from time to time undiluted. To each their own and in their own way. There is more than one way to skin a cat and I'm sure someone will chime in here on the virtues of CA to seal balsa cones.

BTW the one product that I definitley don't recommend is SIG sanding sealer. I found it to be a bit goopy and hard to sand, but that is just my opinion.

 

[AfterBurners]

I have to say in the almost thirty years of using Aerogloss products I've never had it crack on me. I'm not a huge fan of using diluted FNF on balsa because of the potential for warping and swelling but I know there are those who swear by it. FNF is certainly a cheaper option than Aerogloss and I do use it from time to time undiluted. To each their own and in their own way. There is more than one way to skin a cat and I'm sure someone will chime in here on the virtues of CA to seal balsa cones.

BTW the one product that I definitley don't recommend is SIG sanding sealer. I found it to be a bit goopy and hard to sand, but that is just my opinion.

JP - I'm with you on the Aero Gloss products. I've used FnF and got good results, but sometimes I just prefer doing it the old school way. Using the Aero Gloss doesn't make such a mess when sanding. Like said I start with this.

https://www.brshobbies.com/catalog....illercoat_Primer__3.5_oz_bottle_ships_ground_

and then I follow with this.

https://www.brshobbies.com/catalog....s_Sanding_Sealer__3.5_oz_bottle_ships_ground_

I let each coat dry for several hours, if not over night. I never rush the process. I figure it allows me time to work on other aspects of each build. I agree if you are careful with the FnF you can warp the wood, such as fins. I know there is a new product, well maybe not so new that is similar to FnF.

https://www.hobbylinc.com/hobby_and_craft_wood_filler

I heard this stuff works pretty good.

 

[Tarasdad]

Been using Hobbylite to fill and smooth my RC models for a LONG time. Good stuff.

 

[o1d_dude]

As a lifelong AMA Free Flight modeler I used to go the long and boring sanding sealer route.

Then someone here suggested brushing on thin CA with a Q-tip.

Do make sure to do it outside tho. The fumes are eye-watering.

Once dry 30 seconds or so, break the glaze with 220 grit. Add a bit more CA if you see any 'holidays' and repeat.

This technique also works on nose cone or payload bay shoulders.

 

[AfterBurners]

That CA kills me...and if you add it up can be pricey for each bottle. IDK - think I might stay with the dope and get high in the process.

 

[Disaster_Guy]

I have started using ultra-thin CA on the edge of fins (particularly if I have papered them) but still use Aero Gloss for general balsa sealing. If there are any major defects I will use a tiny dab of elmers wood filler.

 

[AfterBurners]

I just applied my first coat of balsa filler to the nose. Gonna hit with some 400 grit tomorrow and then another coat. I'll do it a few more times and then a couple coats of sanding sealer...repaet and then the primer and paint. I'll post pictures when I finish this bird.

 

[o1d_dude]

If you start with 400 grit, you will be a long time filling the pores.

Better to start with a coarse grit (120-180-200) and work your way up to something you can fill with primer.

Unless you're building a museum quality display model, you will ultimately ignite a black powder motor underneath it, boost it to a dizzying altitude, hope the chute deploys, and that it lands in the mythical tall grass. Don't invest so much time in finishing your rocket that you would be afraid to launch it.

 

[MarkII]

I have become a big fan in recent years of using Minwax Wood Hardener on balsa nose cones. No, it doesn't petrify them (this is balsa after all, not oak), and it takes a good while to fully harden, but it really toughens them up so that they don't pick up nicks and gouges so easily. I usually give them two applications 48 hours apart, with a bit of sanding before the second application. Then two weeks later I use Delta Ceramcoat All Purpose Sealer to fill in and seal the grain. With a couple of applications, followed, after they are dry, by some wet-sanding with 400 grit the cone is billiard-ball smooth.

 

[MarkII]

I like to use Aero Gloss products on small balsa fins, though. Works great, and there aren't more than a couple of filling and sanding cycles required if you do it right. My one quibble with it is that I cannot keep it from gradually evaporating away out of the jar once I have opened it, no matter how tightly I reseal it. It's a real pain to keep a good supply on hand because it is more than 50 miles to the nearest hobby shop from here.

 

[mkadams001]

I only use Aero Gloss sanding sealer on balsa. I have never had a problem with cracking.

 

[dander]

Do you guys have problems with the Aero Gloss kinda pulling up the FNF when you apply it? I have, I let the FNF dry for about ten hours before applying the dope. Perhaps I should have let it set for a full 24 hours. I am noobish and trying to figure this stuff out by reading posts followed by trial and error. When I was building rockets as a kid I didn't even prime or sand. It's amazing how some of the models posted come out, I just seem to make big messes. That being said, I had better luck with CA followed by FNF on my Cherokee D. Too bad I botched all that work with the paint.

Dave

 

[Pem Tech]

A second on the thin CA...
I buy the larger bottles of thin CA (Great Plains I think) and it lasts pretty well.
Soak a good initial coat, quickly wipe with a paper towel, wince as your eyes water from the fumes and let harden.
Repeat as needed.

If you start with 400 grit, you will be a long time filling the pores.

Better to start with a coarse grit (120-180-200) and work your way up to something you can fill with primer.

Unless you're building a museum quality display model, you will ultimately ignite a black powder motor underneath it, boost it to a dizzying altitude, hope the chute deploys, and that it lands in the mythical tall grass. Don't invest so much time in finishing your rocket that you would be afraid to launch it.

 

[AfterBurners]

Do you guys have problems with the Aero Gloss kinda pulling up the FNF when you apply it? I have, I let the FNF dry for about ten hours before applying the dope. Perhaps I should have let it set for a full 24 hours. I am noobish and trying to figure this stuff out by reading posts followed by trial and error. When I was building rockets as a kid I didn't even prime or sand. It's amazing how some of the models posted come out, I just seem to make big messes. That being said, I had better luck with CA followed by FNF on my Cherokee D. Too bad I botched all that work with the paint.

Dave

Dave

There isn't one rocket that I built that came out perfect...everyone had some kind of issue whether it was my fault or the parts were poor quality. Just practice until you find what works best for you. In time you will get better at all aspects of building. Some of the guys on here been doing this for years and years...this is a great place to come for advice so at least you picked a great forum to learn from.

 

[Marc_G]

To the OP's concern about sanding causing flat spots or otherwise messing up the shape of the cone: this is a main reason I seal with thin CA. After the thin CA sets you would have to try hard to oversand and cause a flat spot. I do a light sand to remove fuzzies, then thin CA, then a good solid sanding to remove any hardened wood hairs that stick up. After that whatever filling is convenient works. Plain filler primers, CWF, or spot putty work great on top of CA. No worries of warping fins, either.

 

[AfterBurners]

I didn't go the CA route, maybe next time. I'm just using dope sealer and seeing what happens. If the cone does get dinged up over time them I'll get another and change my way of finishing.

 

[rbeckey]

I have used 20 minute finish epoxy on larger balsa cones, such as a BT80 Goblin cone made by Sandman. He provided a bulkhead/eye bolt, so I suspended it , taped the shoulder and brushed on the epoxy. It is so thin it settles smoothly and makes a hard shell. Not much filling required. There was a tiny drip mark on the end of the cone to be sanded off. I have also used Minwax Wood Hardener. Needs good ventilation. Acetone base.

 

[AfterBurners]

If you start with 400 grit, you will be a long time filling the pores.

Better to start with a coarse grit (120-180-200) and work your way up to something you can fill with primer.

Unless you're building a museum quality display model, you will ultimately ignite a black powder motor underneath it, boost it to a dizzying altitude, hope the chute deploys, and that it lands in the mythical tall grass. Don't invest so much time in finishing your rocket that you would be afraid to launch it.

Actually it seems to be working just fine. I bought the nose cone from SEMROC and they really have quality parts. It's turning well. I let the sealer dry completely over night before sanding. I probably don't have to, but it does make a difference when sanding it off.

 

[AfterBurners]

I have used 20 minute finish epoxy on larger balsa cones, such as a BT80 Goblin cone made by Sandman. He provided a bulkhead/eye bolt, so I suspended it , taped the shoulder and brushed on the epoxy. It is so thin it settles smoothly and makes a hard shell. Not much filling required. There was a tiny drip mark on the end of the cone to be sanded off. I have also used Minwax Wood Hardener. Needs good ventilation. Acetone base.

The stuff from BSI? I haven't used it and always wanted to try it.

 

[MarkII]

I figure I'll stick to 320/400 grit papers and finish with 600. I don't want to sand so much as to change the shape of the cone. I know balsa is soft, which is why I want to use the finer papers.

Sand the bare balsa only lightly to remove rough spots and get it to be minimally smooth before you begin your finishing process. Don't try to sand out nicks, grain texture, etc. because that's a losing battle. You make a balsa nose cone smooth by adding material to it, not by taking material away. The goal is to fill in the grain with some sort of filler and to coat the wood with some type of sealer. There are a number of good ways to do that.

One technique that hasn't been mentioned yet is to brush the cone with thin-consistency laminating epoxy. I haven't used anything high-tech for this, just BSI 20 Minute Finish Cure epoxy. Put a good coat or two on it, and then sand it smooth after the epoxy has fully cured. I use this technique in combination with treatment with wood hardener. As I said before, balsa is balsa so you won't turn the nose cone into stone by doing this, but you'll greatly improve its toughness. The epoxy is a very effective grain filler and sealer, and in my experience it is actually easier to sand and easier to get smooth than hardened CA. When you have finished sanding it, the epoxy coating feels like fine satin.

 

[AfterBurners]

I never tried the epoxy, but on my next MAD COW kit I will

 

[rbeckey]

The finish epoxy I used was also Bob Smith Industries as sold at a local hobby shop. Part number BSI209. Doesn't really say BSI any where except the bottom of package and the back of the epoxy bottles, which are in a plastic hanging pack with a flat bottom for store with shelves. I got a 12 pack of water color type paint brushes at the dollar store and they work quite well. Obviously I don't try to use them more than once. I try not to get epoxy on the end of the external part of the cone where it reduces to the shoulder. It is easy to sand after it is completely cured and it takes primer well. Not bulletproof, but much tougher than a naked balsa cone.

I have also use this on very pointy balsa cones to protect the point. I forms a small drip at the end that can be carefully removed or viewed as a "feature" instead of an "issue".

 

[Marc_G]

You make a balsa nose cone smooth by adding material to it, not by taking material away.

I think I ought to print this out in big letters and hang over my worktable. Best sentence in this thread so far! :clap:

 

[AfterBurners]

On my second coat of sanding sealer. It looks good so far. I can see how the sanding sealer hardens the nose cone. I lightly sand it with 400 and it's coming out nice. I had two coats of balsa filler before adding the sealer. I'm happy with it so far. Next up primer and whatever imperfection there are I can touch up with FnF