Sanding sealer types

[Tom Howe]

Hello,
its been many years since I have worked with balsa so I am behind the times for some of the types of products for sealing balsa grain. There are what I used to use such as Testors sanding sealer (which is similar chemically to the good ole dopes available for decades) and then there are the modern water born types. Suggestions appreciated.

Tom

 

[Funkworks]

I tried Minwax sanding sealer a few times. I'm not impressed with the results, but maybe I don't have the right touch yet. It seems like many here are choosing to go with water-thinned Elmer's wood filler instead of sanding sealers. Maybe you should try that. Seems easy to use.

 

[neil_w]

This has been discussed here many, many times. There's a current thread going here: https://www.rocketryforum.com/threads/how-does-cwf-dope-compare.153176/

And another here: https://www.rocketryforum.com/threads/sanding-sealer.153009/

 

[kuririn]

Tom, I remember using Aerogloss and Pactra sanding sealer and dope to finish my model rockets as a kid.
When I became a BAR some five years ago I went in to a local hobby shop looking to buy those: Nowhere to be found!
When I asked the clerk what builders are using now to fill wood, he told me to "just keep spraying layer upon layer of enamel until the wood is saturated".
Yikes! Talk about bad information.
I suppose you could paint layers of enamel or dope until the wood is saturated and get a glossy finish, but that would not be the most EFFICIENT way to do it. Also not very economical, plus there is the extra weight.
So nowadays, most of us use Elmer's Carpenter's Wood Filler (CWF). Combine the CWF with a little water and create a slurry, then brush it on. Two coats or more, sanding between coats, followed by a coat or two of sandable high fill primer, again sanding between coats. That should do it.
https://www.amazon.com/Elmers-E842L...s+wood+filler&qid=1562032522&s=gateway&sr=8-4

Reasons CWF has replaced sanding sealer:
1. Availability: Very few places selling sanding sealer now. Brodak and Sig are a couple of name brands.
2. Economics: One small bottle of sanding sealer costs $9. For $12 I can get a tub of CWF that will last me the rest of my life.
3. Volatile fumes: None with the CWF. Water cleanup.

BTW if you are still interested in using sanding sealer I found a recipe for cheap homemade sanding sealer: dissolve styrofoam into a container of MEK (Methyl Ethyl Ketone) until saturation. Solution should be the consistency of honey. I use the styrofoam peanuts that come with my parcels. Use in a well ventilated area or with a respirator. Disclaimer: Use at your own risk.Fumes are toxic. Also use a glass container and tight fitting metal lid. MEK will dissolve many plastics and synthetic rubber gaskets. Note also that there are two kinds of shipping peanuts out there: don't use the soy peanut, it will not dissolve in MEK.
Seals like liquid plastic. Oh wait, it IS liquid plastic.
And, there is a safer substitute MEK at the big box stores. Haven't tried that yet.
Cheers.

 

[jqavins]

When I became a BAR about 12 years ago I used Aerogloss dope (which I had no trouble finding in hobby shops) and it worked really well to help to get to a nice, smooth surface. Then I tried foam spackle as filler, and it worked just about as well with less effort, because filling the grain then sanding down flaws is fundamentally less work than sanding down all the roughness.

As for dissolving styrofoam to make your own, acetone works (almost?) just as well as MEK, is still easily available, and is somewhat less toxic (not that you want to snort or drink the stuff).

 

[Event Horizon]

I have begun using Deft Lacquer Sanding Sealer with very good results. Two coats on plywood and three coats on balsa, sanding lightly between coats.
The reason I shied away from using carpenters wood filler is because of the fear of the water wet balsa/plywood warping from the part getting wet.
Deft does not warp anything.
I have read that others use CWF and place the fin between wax paper, lay them on a flat surface and lay heavy books on them with good results. I don't understand how the CWF dries when sandwiched between layers of wax paper. It must take a while to dry that way.
Regardless Deft dries in an acceptable amount of time for me. I do spray apply it and do so out doors, while wearing the proper protective breathing gear. Deft Lacquer Sanding Sealer is available in quart and lager containers for brush application.
One can of spray Deft did the tail fins and strake fins for a 1.6" airframe and a 2.6" airframe Sentinel. The fins, all 16 of them, turned out near mirror smooth with a small amount of effort after being primed with 2 coats of Krylon paint and primer flat white.

 

[MichaelRapp]

One can of spray Deft did the tail fins and strake fins for a 1.6" airframe and a 2.6" airframe Sentinel. The fins, all 16 of them, turned out near mirror smooth with a small amount of effort after being primed with 2 coats of Krylon paint and primer flat white.

Interesting.....did you sand between the sealer and the primer? If so, how does it sand?

 

[Event Horizon]

I lightly sanded the first coat of sealer using 320 grit sandpaper to knock down any fluff or high spots, then I sprayed again and sanded off until I got a smooth surface.
Even if you sand most of the sealer off, the wood absorbs some to a depth and will still make a smooth surface when primed.
I sanded again between each primer coat, finishing with 400 grit, and it's ready for a color coat.
I did apply fairly heavy coats each time, spraying a bit on, letting the solvents flash for a few minutes then spraying another layer, repeating this until it built up to my satisfaction.
Warmer temperatures and low humidity help, although I've sprayed Deft and Krylon in cooler temps as well, just have to make each layer a bit thinner and let it flash longer before spraying another layer.
Deft will clog the sandpaper some, so after sanding some I use a wire brush to clean the sandpaper, or pick the clumps off with my fingernail.
I noticed that Krylon paint and primer flat white doesn't seem to clog the paper as readily as other primers will. However after a while I either used a wire brush or rubbed the sandpaper against a cloth, like blue jeans.
This process has worked for me on two rockets so far and I'm happy with the results.

 

[MichaelRapp]

Very cool. I need to give this a try. I keep getting pits in my CWF fins.

 

[beantownJPL]

I use Titebond I thinned down a bit with water. Paint it on, sand, repeat as necessary. Has the added advantage of strengthening the fins a bit.

You do have to do both sides at once to prevent warping, but I've gotten good results with this method.

CWP works well too, but has no structural benefit.

 

[prfesser]

I bought a quart of Minwax sanding sealer, as it was the only kind available at Lowes (or at Home Depot, which we don't have here in PartsUnknown, KY). It cleans up with water and has very little odor, but I was surprised to find that it didn't raise the grain of plywood the way that CWF did. It dries quickly and is quite hard, so it's a bit of work to sand. A big plus IMHO: 3M Sandblaster Pro sandpaper 320 and 400 grit do not clog AT ALL when sanding the Minwax product. I used a single piece 4.5x5.5" to sand a 4" cardboard airframe and four 1/4" plywood fins. Slap the sandpaper against my leg and all the dust comes off. Wet/dry paper clogged slightly but still, not too much.

I haven't painted the rocket yet but two coats of sealer appear to be sufficient.

Best -- Terry

 

[RobertH3]

Had good luck with both CWF and also Bondo #2 tube putty thinned with lacquer thinner (not the 2 part stuff). I use the Bondo mix over plywood surfaces and epoxy fillets, and the CWF for most other stuff. The Bondo is actually easier to sand but fumes and dust are nasty. I am fearful of wetting plywood and light ply - once it warps its warped. Hobby shops used to have Squadron Green Putty back in the day - I think that was Green Bondo as odor was similar.

Cheers / Robert

 

[AfterBurners]

Tom, I remember using Aerogloss and Pactra sanding sealer and dope to finish my model rockets as a kid.
When I became a BAR some five years ago I went in to a local hobby shop looking to buy those: Nowhere to be found!
When I asked the clerk what builders are using now to fill wood, he told me to "just keep spraying layer upon layer of enamel until the wood is saturated".
Yikes! Talk about bad information.
I suppose you could paint layers of enamel or dope until the wood is saturated and get a glossy finish, but that would not be the most EFFICIENT way to do it. Also not very economical, plus there is the extra weight.
So nowadays, most of us use Elmer's Carpenter's Wood Filler (CWF). Combine the CWF with a little water and create a slurry, then brush it on. Two coats or more, sanding between coats, followed by a coat or two of sandable high fill primer, again sanding between coats. That should do it.
https://www.amazon.com/Elmers-E842L-Carpenters-Filler-1-Quart/dp/B001E5L19O/ref=sr_1_4?keywords=elmer's+carpenters+wood+filler&qid=1562032522&s=gateway&sr=8-4

Reasons CWF has replaced sanding sealer:
1. Availability: Very few places selling sanding sealer now. Brodak and Sig are a couple of name brands.
2. Economics: One small bottle of sanding sealer costs $9. For $12 I can get a tub of CWF that will last me the rest of my life.
3. Volatile fumes: None with the CWF. Water cleanup.

BTW if you are still interested in using sanding sealer I found a recipe for cheap homemade sanding sealer: dissolve styrofoam into a container of MEK (Methyl Ethyl Ketone) until saturation. Solution should be the consistency of honey. I use the styrofoam peanuts that come with my parcels. Use in a well ventilated area or with a respirator. Disclaimer: Use at your own risk.Fumes are toxic. Also use a glass container and tight fitting metal lid. MEK will dissolve many plastics and synthetic rubber gaskets. Note also that there are two kinds of shipping peanuts out there: don't use the soy peanut, it will not dissolve in MEK.
Seals like liquid plastic. Oh wait, it IS liquid plastic.
And, there is a safer substitute MEK at the big box stores. Haven't tried that yet.
Cheers.

Guess I'm one of the few who have few jars of unopened aerogloss left.

 

[SCIGS30]

I was bummed when Aerogloss stopped making balsa sealer, used it for years with great results and was carried at all hobby stores. I tried Sig Sealer but could not achieve the results I was getting with Aerogloss, could just be user error. Then I ordered Brodak balsa sealer and I have found it is better than Aerogloss. Most of the time I am brushing on just 2 coats and the grain is filled with minimal time and effort. The downsides......You have to order online and just like Aerogloss the fumes are strong.

 

[prfesser]

FWIW the Minwax sanding sealer I got from Lowes only required two coats on 1/4" plywood to remove the grain marks entirely. Balsa might be different, I dunno.

Best -- Terry

 

[Michael MacDonald]

I know that this has been answered here many times before but I'll ask again.

Is it better to do the sanding sealer/sanding before or after the fins are mounted to the airframe?

 

[SCIGS30]

I know that this has been answered here many times before but I'll ask again.

Is it better to do the sanding sealer/sanding before or after the fins are mounted to the airframe?

Great question, I think we have all asked that at one time or another. Sometime back I did an experiment with sealing fins before attaching and sealing after fins were glued in place. I then tried tearing the fins off the rocket and did not notice a difference, both were pretty tough to rip off. I have never had a fin pop off at the glue joint. Just have to remember not to get sealer on the root edge. It is much easier to seal and sand balsa before attaching to the rocket.

 

[afadeev]

Tom,
Don't fill the grain, paper OVER it.
This is a significantly faster process that also strengthens the fins.

Details here: https://www.rocketryforum.com/threads/papering-balsa-ply-fins-a-foolproof-method.65628/

 

[RobertH3]

Papering fins is great - if you haven't done it before, be very careful when trimming the excess off. I use Apogee, E-Rockets, ASP, and Jonrocket receipts exclusively! Free paper and no personal info available. Working on a Flutterby kit and am taking the Estes re-issue back to Centuri original. I papered the fins to get rid of the non-original balsa reinforcement pieces and used paper hinges on the fin joints of the lower piece. Good stuff.

Cheers / Robert

 

[SCIGS30]

My advise, get some scrap balsa and practice the different techniques and use the one that fits your bill. As you can see, most builders have their ideas of the best filling methods, at the end of the day it is what you like. No matter what method you select, a nice looking finish takes time, attention to detail and above all practice and some experience. Or you can just say the heck with it and build the rocket, slap on some paint with decals and have fun flying. You will see a lot of youtube videos of people doing just that and having fun flying rockets.

 

[SCIGS30]

 

[neil_w]

My advise, get some scrap balsa and practice the different techniques and use the one that fits your bill.

I can't recommend this often enough.

 

[SCIGS30]

Here is a Goblin rocket I started 2 days ago and should have the decals on tomorrow. I used Brodak balsa sealer, brushed on one coat fins off the rocket. I let the first coat dry 20 min and brushed on a second coat, let dry 30-45 min then sanded smooth and started building. I did not use any primer, just shot a coat of gloss white followed by gloss orange. Sure not perfect, but good enough for flying.

 

[BABAR]

Here is a Goblin rocket I started 2 days ago and should have the decals on tomorrow. I used Brodak balsa sealer, brushed on one coat fins off the rocket. I let the first coat dry 20 min and brushed on a second coat, let dry 30-45 min then sanded smooth and started building. I did not use any primer, just shot a coat of gloss white followed by gloss orange. Sure not perfect, but good enough for flying.

Looks great. I would argue however that pic 1 is good enough for flying!

 

[AfterBurners]

Here is a Goblin rocket I started 2 days ago and should have the decals on tomorrow. I used Brodak balsa sealer, brushed on one coat fins off the rocket. I let the first coat dry 20 min and brushed on a second coat, let dry 30-45 min then sanded smooth and started building. I did not use any primer, just shot a coat of gloss white followed by gloss orange. Sure not perfect, but good enough for flying.

I have some of the Aergloss sealer and more than likely will finish it off first however long that may take considering I'm not knocking out too many rockets, but may try your technique? You did a nice job on it and it looks great. Where did you buy the sealer at? Is this a hardware store item or do you order it online at a hobby store etc.

 

[SCIGS30]

I have some of the Aergloss sealer and more than likely will finish it off first however long that may take considering I'm not knocking out too many rockets, but may try your technique? You did a nice job on it and it looks great. Where did you buy the sealer at? Is this a hardware store item or do you order it online at a hobby store etc.

I used Aerogloss for years and the best I could do is 3 to 4 coats with sanding in between for a smooth grain free finish. I am using Brodak balsa sealer and I buy it online directly from Brodak.

 

[AfterBurners]

I used Aerogloss for years and the best I could do is 3 to 4 coats with sanding in between for a smooth grain free finish. I am using Brodak balsa sealer and I buy it online directly from Brodak.

So Brodak sells both a balsa sealer and sanding sealer or they are same?

 

[Cape Byron]

I've started using Deluxe Materials Sand'n'Seal recently. Two coats, sand, a third coat, sand, a fourth coat, sand. Really nice finish.
Sounds more onerous than it really is. Sorry, no pics. I parked the last one in a tree...

 

[AfterBurners]

Tom,
Don't fill the grain, paper OVER it.
This is a significantly faster process that also strengthens the fins.

Details here: https://www.rocketryforum.com/threads/papering-balsa-ply-fins-a-foolproof-method.65628/

I agree but sometimes when I feel like bringing back memories I'll use Aerogloss sanding sealer

 

[les]

I used Aerogloss for years and the best I could do is 3 to 4 coats with sanding in between for a smooth grain free finish. I am using Brodak balsa sealer and I buy it online directly from Brodak.

Do you thin it or use it full strength? What is needed to clean the brushes?
Thanks