Fil-n-Finish vs. Sanding Sealer

[AKPilot]

I use Fil-n-Finish, with good success, to fill in the grooves on both my balsa and BTs. I really have no complaints and my models come out pretty slick.

I've never had any experience with sanding sealer and, to be quite frank, not sure what this is all about.

What are the advantages over simple fil-n-finish?

 

[Rob Fisher]

I would stick with the fill-n-finish. Sanding sealer has some very noxious fumes & I doubt that it would work at all for filling spirals.

 

[RoyGreen]

Originally posted by akpilot
I use Fil-n-Finish, with good success, to fill in the grooves on both my balsa and BTs. I really have no complaints and my models come out pretty slick.

I've never had any experience with sanding sealer and, to be quite frank, not sure what this is all about.

What are the advantages over simple fil-n-finish?

only a couple. Sanding sealer will result in a tougher finish. Fil'n Finish is soft and moisture sensitive. I've done two rockets that are F'nF-only (and a coat of spray filler/primer) and while they look great after painting, they tend to take dings easily.

On the other hand, I've done nose cones and fins where I use one coat of sanding sealer as the base, then F'nF, then spray filler/primer. This seems to be the best combo.

F'nF first, then one coat of sanding sealer, then optional spray filler/primer seems to work as well.

Using sealer only can result in beautiful nose cones and fins that are pretty tough, but it takes work.

Sealer *will* work for spirals, but it's not easy, and you'll have to roughen up the tube with 400 grit sandpaper or the sealer will peal easily from the glassine.

 

[m85476585]

I use Minwax Polycrylic as a sanding sealer. It is water-based and has almost no fumes (I have the brush on kind, not the spray can kind), but it is water-proof when it dries. It takes a few coats so get balsa smooth because you have to sand most of it off each time, but it results in an extremely smooth finish even with just two coats. It makes a good clear coat too.

 

[JBeau]

Originally posted by RoyGreen
...while they look great after painting, they tend to take dings easily.

If this is an actual issue for you, toughen up your fins before you do any finishing using Thin CA...a light layer wicked onto each surface. Adds no weight and really makes your fins firm. Then, sand and finish, you may need fewer steps after sanding the CA application.

 

[Mad Rocketeer]

How about using Fill-N-Finish, then wicking water-thin CA into it after it's dried, then doing the final sanding? That's what I planned for the outer portion of my Graduator's fin fillets. (I had done an epoxy fillet first, then covered it with Fill-N-Finish, to get the final size, curve, and finish.) I forgot though and just painted over the Fill-N-Finish directly.

 

[Rocketeer]

I seal the balsa with wood glue first, then apply the Elmer’s wood fill (thinned with a drop or two of water) after the glue is dry, then I sand. The wood glue strengthens the balsa some, and because both the glue and wood fill are water based, they adhere together well. On cheaper, flimsy balsa I have used CA and then wood fill and that worked as well, but you need good ventilation with CA because the fumes are nasty.

btw, I stopped using dope type sanding sealer for rockets a long time ago. The fumes are bad, it takes three coats to get the balsa smooth, and it doesn’t seem to strengthen the balsa as well as wood glue.