Treating soft/punky balsa

[Sooner Boomer]

@hobie1dog
I've been thinking about your problems with bad balsa and what to do about it. My first reaction is to suggest you soak it in thin CA. I don't think that would work for you. Fumes, etc. My next thought was something like a water-based polyurethane. The problem with that is that unless you wait a long time for it to cure, and sometimes even then, it can be gummy when you try to sand it. It's hard to find model airplane dope any more, so that's out. My last thought would be to use shellac. It's very thin, so it should soak in easily. They usually use alcohol for the solvent, so it shouldn't have bad fumes. It's fairly inexpensive and easy to find. Think that might work?

 

[Hobie1dog]

@hobie1dog
I've been thinking about your problems with bad balsa and what to do about it. My first reaction is to suggest you soak it in thin CA. I don't think that would work for you. Fumes, etc. My next thought was something like a water-based polyurethane. The problem with that is that unless you wait a long time for it to cure, and sometimes even then, it can be gummy when you try to sand it. It's hard to find model airplane dope any more, so that's out. My last thought would be to use shellac. It's very thin, so it should soak in easily. They usually use alcohol for the solvent, so it shouldn't have bad fumes. It's fairly inexpensive and easy to find. Think that might work?

I bought a can of shellac/ sanding sealer and it was pretty thin right out of the can so I used it on the last rocket and put four coats on the balsa fins and it really didn't fill in the grain that great, but it does dry fast.

 

[dhbarr]

I'd probably try one of the Wood Hardener products, but they're usually chock full of stinky -anes.

 

[lakeroadster]

Like @dhbarr said...

Minwax high performance wood hardener is a quick drying liquid formulated to strengthen and reinforce decayed or rotting wood.

• The hardener penetrates deep into the wood and its special resin binds and reinforces the decayed wood fibers
• High performance wood hardener seals from further moisture penetration and hardens to a rock hard solid base for lifting
• Designed to strengthen wood fibers of interior or exterior rotted wood prior to the application of Minwax high performance wood filler

https://www.acehardware.com/departm...f48e2130fbed129979c0453803777d37&gclsrc=3p.ds

 

[Sooner Boomer]

The problem is that wood hardener is twice the price of shellac. Shellac (commercial) contains ethyl alcohol, isopropyl alcohol, with a trace of MEK*. Wood Hardener contains methyl alcohol and acetone (plus proprietary ingredients). ^

Shellac can also be compounded by mixing shellac flakes (or buttons) with (only) isopropyl (or methyl) alcohol.

* https://www.whatsinproducts.com/fil...SDS Zinsser Bulls Eye 4 Lb. Clear Shellac.pdf

^ https://assets.unilogcorp.com/187/ITEM/DOC/Minwax_100029211_SDS.pdf

 

[justforfun]

Ever think of replacing the balsa, with a better quality piece?

Roy

 

[lakeroadster]

The problem is that wood hardener is twice the price of shellac. Shellac (commercial) contains ethyl alcohol, isopropyl alcohol, with a trace of MEK*. Wood Hardener contains methyl alcohol and acetone (plus proprietary ingredients). ^

Shellac can also be compounded by mixing shellac flakes (or buttons) with (only) isopropyl (or methyl) alcohol.

* https://www.whatsinproducts.com/files/brands_pdf/26002065 MSDS Zinsser Bulls Eye 4 Lb. Clear Shellac.pdf

^ https://assets.unilogcorp.com/187/ITEM/DOC/Minwax_100029211_SDS.pdf

$18 for a lifetime supply? And for about the price of (1) mid power composite motor?

 

[Sooner Boomer]

One more thought; something else that might work. Hairspray. Especially the pump-type. It's fairly inexpensive and readily available. A lot have a form of shellac in alcohol as ingredients.

 

[Sooner Boomer]

Ever think of replacing the balsa, with a better quality piece?

Roy

And increase the cost even more? My thoughts got started down this trail because @hobie1dog got some rockets that were already built that he needed to fix. His experience with low quality balsa got him really turned off on the materiel as a whole.

 

[T-Rex]

$18 for a lifetime supply? And for about the price of (1) mid power composite motor?

Unfortunately, like everything else, the price has increased. I just looked it up and shellac flakes are going for about $35/pound online. I have no idea what they would cost in a brick & mortar store.

 

[afadeev]

I've been thinking about your problems with bad balsa and what to do about it. My first reaction is to suggest you soak it in thin CA. I don't think that would work for you. Fumes, etc.

There are fume-less version of CA out there. They are move expensive, but worth it, IMHO:
https://www.erockets.biz/bsi-122-cyanoacrylate-ca-super-glue-1oz-super-thin-gold-gold-label/

And increase the cost even more? My thoughts got started down this trail because @hobie1dog got some rockets that were already built that he needed to fix. His experience with low quality balsa got him really turned off on the materiel as a whole.

Any remedy will increase cost.
How perfect do you want to get? How much $$$ are you willing to spend to get there??

My experience with Balsa is that its density and quality vary a LOT between different sheets, and between different corners of the same sheet of balsa. It is what it is, naturally.
Personally, I paper 100% of my balsa parts to both strengthen the parts, and achieve uniform surface for future painting.
Papering adds weight, but not much cost.

HTH,
a

 

[bjphoenix]

Ever think of replacing the balsa, with a better quality piece?

If it's something where strength matters such as a fin, I would recommend this too. Hardeners and CA will make the surface more solid but I don't think they add much to the bending strength.

 

[Ez2cDave]

@hobie1dogIt's hard to find model airplane dope any more, so that's out.

BUTYRATE DOPE . . .

https://www.univair.com/categories/paint-dope-fabric/randolph/dope/butyrate-dope.html

Dave F.