Fin Grain Filling Technique, Which Is Best?

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RocketGeekInFL

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I am sure this has been covered here countless times, but I have not seen a thread yet that discusses the pro's and con's of each technique, and which is more preferred and why?

I have tried FNF (elmers wood filler)
I have laminated with paper and white/yellow/spray glues (have not tried glue stick yet)
I have used PRM (large label paper)
I have tried sanding sealer (the stinky dope one)
I have used polycrilic


They each have their pro's and con's, I am just wondering what everyone else sees as pro's and con's, as well as which method is preferred and why.
 
I have always used wood filler. Don't think I'll try anything else cause it's so flexible. I can thin it down with water to whatever consistency I need, fill any gap I need, it sands so easily that there's no issues there. The only drawback is that sometimes, what appears to be completely filled isn't after sanding. But the fix is super simple... Do another batch, let it dry and sand smooth.
Clean up is a breeze... Just wet a cloth and wipe it up. I've even used a slightly camp cloth to do a final smoothing on the rocket.
If anyone can name some cons, let me know cause I've never used anything else.
 
+1 on papering. I do it on all of my LPR builds now. I just use Avery labels and CA the edges.


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I sometimes use DAP. Used for filling holes in dry wall. Found at local hardware store. Goes on pink and dries white, sands easily when dry.
 
Papering. I've used thinned white glue and Mod Podge (essentially the same thing but the consistency is just right as it comes in the bottle). Then Rustoleum sandable primer and paint.
 
Elmer's Wood Filler then sand. Repeat until smooth. Easy to do. Paint on wood filler thinned with water to desired consistency. That only takes a couple of minutes. Sanding the filler is quick and easy. Works great.
 
Self adhesive label paper.
CA on the edges or when I'm feeling really patient I roll the fin over so the paper covers the leading edge.
 
To actually answer the question:

(IMO, of course)

Filler Pros: Probably the smoothest finish when done well.
Filler Cons: Time consuming and a pain in the rear. Pretty messy with all the sanding

Paper Pros: Quick. Less hassle than filler. Good results
Paper Cons: Potentially not as nice a finish as filler. Sticky fingers.


If you want the best possible finish and don't mind the time and effort, you can get better results with filler. However, if "really good" is acceptable to you, you can get there with a lot less muss and fuss with papering. If you're really masochistic, you can do both. I mostly paper these days.
 
My current techniques depend on the graininess of the wood and things like how much surface area there will be to cover, and so on.

I'm currently a big fan of papering balsa fins with lightly tacked (with spray adhesive) computer printer paper, trimming them close to the edge of the fin, then saturating with CA (proper ventilation and personal protection equip [gloves, goggles] are a must). Lightly sand the resulting fins and they are like smooth plastic, and MUCH MUCH harder than they were before. This is a relatively low effort, fast time to completion method. Following this method, I usually do one coat of filler primer and sand, but only because the rest of the rocket needs filler primer (spirals etc.).

Another thing I do with grainy balsa is saturate it with CA, let harden, then use wood filler for the grain, followed by sanding smooth. The reason to fill first is that sanding won't change the shape of the balsa unless you way over do it with pressure or duration. This is particularly important to me for balsa nose cones... I've accidentally sanded some flat spots on mine before this technique became my standard.

If it is a less grainy wood like basswood, I'll just shoot some filler primer on it and sand smooth. Two coats usually does it!

Marc

PS: My CA based techniques: pros: easy, fast, very smooth results, great paint compatibility, hardens the wood. Cons: need for ventilation when working with the CA.
 
1. Use Masonite. Needs some smoothing but no grain. Slightly weaker than plywood, same weight and stiffness, no warping, easy to repair, about 1/30th the cost of aircraft grade ply. I've seen too many pieces of warped plywood to consider using it for fins even it were free.

2. Paint. OK, all of my models with this have some visible grain ... at least it's not spiral.

3. WEST epoxy. Have only done one nosecone with it. One coat, sand, somehow I soaked some extra CA into the cross-grained part, sand again, absorbed almost no paint and barely needed more than one coat, weight barely over bare balsa. Amazing. P.S. don't listen to anyone who says you need sealer first. Epoxy is the only effective sealer against water vapor. Purpose of WEST is to convert wood into an engineering material, and then bond with the same substance.
 
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