Strength before primer question???

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Well-Known Member
Jan 22, 2009
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I have been using wood glue with my finger and a little water as needed to fill the balsa wood. I sand and mount the fin then put the wood glue on both sides at the same time then after drying I sanded it then use fill and finish then plastic coat primer. I have used thin super glue in place of wood glue but I don't like the smell.

Question, do most of you use primer only or fill and finish only on balsa or do you use something to give the wood some strength first and if so what?

First, welcome to TRF!

For strengthening balsa fins, you have many choices. Like you, I don't like the fumes from using mass quantities of CA. I have also used watered-down glue, but if I am going to do that, I feel like I get much more benefit from laminating a sheet of paper on each side of the fin. (I do this before attaching the fins so I can pile some old phone books on top.) Some people even use heavy paper or card stock. However you do it, the fins are STRONG, and the surface is 90% finished.

You can also cover the balsa with epoxy. This adds a lot of weight, and I am not sure how well it soaks in.

One more product that I found out about here on TRF: Minwax-brand 'Wood Hardener' is a very watery, VERY STINKY product that is specifically designed to soak into wood to harden and pre-seal the wood fibers. THIS STUFF MUST BE USED OUTDOORS. It is labeled as being quite flammable. It will definitely get you an invitation to move your stuff to the far end of the yard. A pint of it cost about $6-8 at the home improvement store.

For finishing balsa fins (or anything else) there are several products that will quickly and easily cover just about any kind of wood grain. Kilz brand spray-on primer has been extensively discussed in another current thread. You can get it at your local home improvement store.

Some people have used a mix of thinned glue (water-based) and talcum powder. You could accomplish the same thing, in a more high-tech fashion, by mixing in micro-balloons instead of talc. You can even mix in balsa dust (that last suggestion is from an old Estes publication).

There is no one 'right' way to do it, it comes down to what materials do you have handy (or what can you afford), what technique do you think is easy to do, and how perfect does your finish have to be to make you happy. Go from there. Make sure to come back sometime and tell us what worked for you?
Originally posted by Flash

Question, do most of you use primer only or fill and finish only on balsa or do you use something to give the wood some strength first and if so what?

I use Deft spray lacquer sanding sealer. It's pretty much like the stuff Powderburner describes, though it doesn't specifically say it adds strength. It does though. It even strengthens body tubes, and it fills the spirals. Two coats on the body, two double coats on the wood with sanding after both, and it's ready for priming. Definitely an outdoor only product, unless you've got a fume hood.