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Balsa Finishing?
BAR with balsa fin/cone finishing question? As a kid, I didn't worry much with filling the balsa grain in fins and nose cones and if I did, not much. Build it, paint it and launch it! Next!
As a model builder again, I would like to finish my models to a higher standard and have gained good info from this forum. I am currently using the Elmer Fill/Finish product and have had good results, not great? It seems that no matter how many coats I apply, some grain remains - especially on a nose cone I'm currently working on. Does the balsa need to be sealed before the filling process starts? Seems like the balsa is soaking it up like a sponge? Thanks in advance for any advice/info! |
#2
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Yes, at some point you will need to seal the wood. Aerogloss Sanding Sealer or Balsa Filler in three coats with 400 grit between. Then a prime (I commonly use matte white to add good undercoat) then the main color probably in two coats. If you want to really have a slick fininsh then you would use a relatively heavy final coat for color depth. Then you will get into the clear coat converation.
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Gravity is a harsh mistress SAM 002 NAR 91005 "The complexity of living is eminently favored to the simplicity of not." |
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For fins, I'm in the "self-adhesive label paper" camp. Stick it on, trim, and hit the outer edges with thin CA to seal them down.
For NC's and transitions, Kilz primer is a good method. You will sand much of it off, but what remains becomes a really good "skin" that can be polished with progressively finer sanding papers before the color shot is applied. For final finishing/decal seal coating I use "FFF", or what used to be called "Future Floor Finish". I think it's been renamed to Pledge, but it's still the same stuff. The technique has been around since the stuff first came out. I airbrush it straight, no thinning. Works both as a decal surface prep, and as a decal sealer. FnF is still a good surfacer, if just a bit messier. It's water-based, so you have to be careful on thin fins to do both sides evenly, otherwise the fin will cup with the grain as one side expands and the other doesn't.
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Craig McGraw BARCLONE Rocketry -- http://barclone.rocketshoppe.com BARCLONE Blogsite -- http://barclone.wordpress.com BARCLONE Forum -- BARCLONE Forum BARs helping BARs SAM 0044 AMA 352635 |
#4
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My preferred method:
A sealer like dope Sanding Sealer or Minwax Wood Hardener (sand smooth) Wait. Wait longer. Let that stuff outgas. Elmer's filler, several coats, sanding in between. Wait a bit. Let that water evaporate. Prime, sand, prime, sand until it is smooooooth. If necessary, use thick gray enamel to fill cracks and dings. Wait. Several coats of paint. Wet sand out any problems. Dry thoroughly. Wet sand if necessary. Rub out any haze or imperfections with polishing compound. Future. Decals. More Future. Buff. |
#5
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Personally, I use Aerogloss Sanding Sealer exclusively. The number of coats depends on the hardness of the balsa and on the desired finish. This Texas Firefly took 4 coats on the nose cone and fins.
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Never trust an atom. They make up everything. 4 out of 3 people struggle with math. Chemically, alcohol IS a solution. NAR# 94042 SAM# 0078 |
#6
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Here's my method that I have been using since 1977 (almost 35 years):
Phase 1) 3 coats of WELL-MIXED and STIRRED Aero Gloss Balsa Fillercoat with sanding between coats 2 and 3; coat two should be applied over coat one as soon as the solvents flash in coat one. Sand coat two after an hour and apply coat 3. After drying at least an hour, sand coat 3. Phase 2) After the sanded balsa fillercoat has dried overnight, apply two or more coats of Aero Gloss Sanding Sealer over the fillercoat, with sanding between coats after they dry. Some apply the sealer before the fillercoat but that is BACKWARDS as the fillercoat FILLS much better over the raw wood. Finished wood parts using this method can be topcoated with ANYTHING including butyrate dope. Using Elmers Water-based fill-n-finish results in a substrate NOT compatible with dope or "hot" solvent content lacquers. In addition, fill-n-finish makes a HIDEOUS DUST MESS when sanding which Aero Gloss products do not.
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When in doubt, WHACK the GAS and DITCH the brake !!! Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't ! Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY. ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC ! |
#7
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Great tips/ advice, thanks to everyone! I learned the hard way on my Nike X fins using the water based FnF. They are thin, fairly soft balsa and looked like Fritos when they dried! Glad I cut two sets, coated both sides at once on second set and they are fairly straight. As a couple folks noted, the FnF does make a dusty mess, had to move my sanding operation outside!
Is there a difference between Aero Gloss sealer and fillercoat or is it the same product? |
#8
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Another method for sealing is using laminating epoxy. This is somewhat of an advanced technique, so I am only mentioning it as it is something that I do to seal balsa. If you add talc and/or glass microballoons to the epoxy, it helps to close up the tiny holes in the wood. Usually two treatments are all that is needed. This method as seen as overkill by some and it's use is certainly in the minority of builders. AFAIK, epoxy-based sealing methods will have no compatibility issues with either lacquer or enamel primers.
Also, on the topic of epoxy. Stay away from polyester and vinylester epoxies. There is some nasty stuff in them and those are the kind you typically find at home supply and auto supply stores. Aeropoxy and SYSTEM 3 by WEST are good quality epoxies, but there is a distinction made between laminating epoxies (which are quite runny for fiberglass or carbon fiber layup) and epoxy adhesives (which are thicker). Regardless of whichever method you use to seal balsa, the final finish will be only as good as your primer coat. Good paint shows how good a job you did on sealing and priming. Greg |
#9
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Worked in the past.
Quote:
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Scotty Dog NAR 90998 Last edited by Scotty Dog : 03-09-2011 at 07:29 AM. Reason: WOOD |
#10
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Quote:
Sounds like you have it perfected. What do you mean when the solvents "flash" |
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