Hardening balsa nosecones

Could some one please explain how to use CA to harden a NC ? Do I use wood filler first? The balsa seems very soft to me so I need to do something .Thanks

You coat the bare balsa with the CA. It soaks into the surface and it hardens. Then you sand it smooth. If you tried to 'fill' the balsa first, then you could not use the CA very effectively as it would not soak in. You could fill and seal the balsa first, then apply a hard shell of paint, but you probably want to make the wood surface stronger before you fill and paint, otherwise the shell of paint will simply crack, like the coating of a Klondike bar.

Yes, CA is the first thing that goes on. And this may go without saying but: Perform this operation in a well ventilated area (outside even). Keep the piece at arms length until the CA dries as the fumes created are quite unpleasant to the eyes, nose, and throat.

First get some of the thinnest, wateriest CA you can find... Personally I use the "pink bottle" stuff from Hobby Lobby. Next, get you some wax paper to line a paper box lid (or similar low-sided cardboard box, like a soft drink flat, etc) and take your cone and CA OUTSIDE. (This operation WILL release fumes that are eye/nose irritants, so DON'T do it indoors. Gloves of some sort are also highly recommended to prevent gluing your fingers to the nosecone.

Now, stand with the wind blowing from either your right or left, across you and the work-- standing with your back to the wind can cause the wind to curl around you can whiff fumes in your face, standing facing into the wind can do the same of course. Take the CA in one hand, and cone in the other. Hold the cone point-down, as gingerly as possible by just the lower edge of the cone shoulder if you can. Apply CA starting at the edge of the cone just above the shoulder, working your way all the way around the cone, while gently turning it in your fingers... I gently squeeze the CA out of the bottle onto the surface, and then rub it slightly with the SIDE of the applicator tip to spread it across the surface, working my way down toward the tip. It will take quite a bit, because the nose cone will "drink" it in as it seeps deeply into the wood grain pores. Be careful because it WILL follow the wood grain upward through capillary action to the base of the shoulder... It CAN glue your fingers to the cone if you're not constantly keeping it moving by rotating it in your fingers! Let the cone drink in all the CA it will take. Once it stops drinking it in (you'll know, because it will start running down to the tip) spread what's running around, and then set it down on the shoulder ON TOP OF THE WAX PAPER. (CA won't stick to wax paper) and allow it to air dry. The CA will cure, and then you get to sand off all the hardened concretions of balsa dust and "hair" (wood fibers) raised and hardened by the CA.

While CA DOES harden the cone "somewhat", it will NOT make the cone "bulletproof"... Just so you know. It will fill the grain somewhat and what's left of the grain pores after hardening can usually be easily filled with a few coats of primer properly applied and sanded down. Basically, you can make balsa look like plastic with these methods...

Later! OL JR

samb said:

Yes, CA is the first thing that goes on. And this may go without saying but: Perform this operation in a well ventilated area (outside even). Keep the piece at arms length until the CA dries as the fumes created are quite unpleasant to the eyes, nose, and throat.

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this warning can't be taken serious enough. any time you are using a lot of CA you have to be EXTREMELY careful. do not lean over it, do not breather over it, the fumes are nasty. just leaning over it can burn your eyes.

Nitrile gloves will be your best friend throughout this process.

K'Tesh said:

Here's a link to my tutorial on the process...

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Thanks, interesting tips.

And expect it to soak up A LOT of CA. A Nose Cone I did awhile back that is about 2.25" Diameter by about 10" Length absorbed nearly a whole 2 oz. Bottle of Bob Smith Super Thin.

pepe said:

Could some one please explain how to use CA to harden a NC ? Do I use wood filler first? The balsa seems very soft to me so I need to do something .Thanks

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Some time ago I learned a trick for CA hardening Balsa and other wood nose cones. mount the cone on a 1/4" hardwood dowel, chuck this dowel in a cordless drill and spin the cone while holding a Medium thickness CA soaked paper dowel on the surface. A latex or rubber glove helps but not absolutely necessary. If the towel starts to dry add a bit more CA. this method not only hardens the surface it also Polished the air drying CA.
Medium thick CA gives a little more time for the CA to soak in as it's drying. For BT-5 and smaller cones a Dremel tool and 1/8" dowel work wonderfully

As others have mentioned a Fan behind you blowing over your shoulder does away with the fumes problem.

Not too long ago someone posted a method where they mounted the cone to a spare body tube, attached a shop-vacuum to the other end of the tube, and painted on thinned epoxy or penetrating epoxy. I can't find the thread, of course, and I haven't tried it, but I recall him reporting that he got it to penetrate quite far.

I've used Minwax Wood Hardener before on some bass wood that I needed to stiffen-up. Worked pretty well! It's generally used on old, decaying wood, but worked just fine on 'new' wood too.

Now that I think about it... I seem to remember that someone used a rotisserie-like setup to evenly apply epoxy to their balsa NC's. I'd be interested in adapting that for CA.

K'Tesh said:

Now that I think about it... I seem to remember that someone used a rotisserie-like setup to evenly apply epoxy to their balsa NC's. I'd be interested in adapting that for CA.

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I can't really see why... basically the balsa "drinks in" the CA as fast as you apply it until it's saturated/cured to the point it won't accept any more... and what's left dries in a couple minutes...
I could see the use of such a setup with slow-curing epoxy, but CA... nah...

Whatever floats your boat though I guess...

Later! OL JR

luke strawwalker said:

I can't really see why... basically the balsa "drinks in" the CA as fast as you apply it until it's saturated/cured to the point it won't accept any more... and what's left dries in a couple minutes...
I could see the use of such a setup with slow-curing epoxy, but CA... nah...

Whatever floats your boat though I guess...

Later! OL JR

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I'm applying CA pretty heavily on the NC, and it cures in odd ways (bubbles up in places, raised lines from previous passes...) I'm thinking that if it was turning slowly you could get an even application, which might promote even curing, and may simplify the sanding later.

Nasty Nose Cone says to Sis': "Don't worry Sis', we'll get you fixed up, then we can call you the Bondo Balsa Bimbo."

TopRamen said:

Nasty Nose Cone says to Sis': "Don't worry Sis', we'll get you fixed up, then we can call you the Bondo Balsa Bimbo."

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LMFAO!!!!!!

I find that the CA produces a shell that can be sanded to a very smooth finish, but that it doesn't penetrate very far. It cures very quickly when it comes in contact with the wood and it seals it up. I also find that the resulting shell of CA isn't very tough and doesn't handle impacts well.


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You can thin epoxy with lacquer thinner to a near water like thickness and soak it into the balsa. The epoxy won't start working until the lacquer thinner evaporates. The mixture will penetrate deep. After sanding a second coat of epoxy finishes off the job.

dave carver said:

You can thin epoxy with lacquer thinner to a near water like thickness and soak it into the balsa. The epoxy won't start working until the lacquer thinner evaporates. The mixture will penetrate deep. After sanding a second coat of epoxy finishes off the job.

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I'm going to try that next time I do a Balsa Cone, Thanks.
On my Semroc "Retro-Repro" Blue Bird Zero, I used the CA on the Nose, but I also built it with the Stock Recovery System, meaning the Shock Cord was not long enough. On its second Flight the Nose Cone rebounded into the Mouth of the Body Tube, leaving a nice Dent in the Nose.
I was able to fill it, the Body Tube is fine and I'll lengthen the Cord with extra Kevlar before it flies again, but I was surprised that the Balsa dented so easily.

TopRamen said:

I'm going to try that next time I do a Balsa Cone, Thanks.
On my Semroc "Retro-Repro" Blue Bird Zero, I used the CA on the Nose, but I also built it with the Stock Recovery System, meaning the Shock Cord was not long enough. On its second Flight the Nose Cone rebounded into the Mouth of the Body Tube, leaving a nice Dent in the Nose.
I was able to fill it, the Body Tube is fine and I'll lengthen the Cord with extra Kevlar before it flies again, but I was surprised that the Balsa dented so easily.

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Some have given me crap about how the epoxy is "weaker" when you use it that way but you have to consider how much stronger it is compared to not having it sink in that far. It's a for sure do it outdoors thing. I've used it to strengthen door skin fins which works great. Doorskins are Philippian mahogany and very porous. Soaks up the epoxy like mad and makes for real strong fins.

Here is the thread on using a shop-vac to draw the thinned epoxy further into the balsa:

https://www.rocketryforum.com/showthread.php?64265-The-Shop-Vac-Balsa-Nose-Cone-Filling-Method

Someone needs to do a research project comparing the hardness/mass of nosecones coated with epoxy, thinned epoxy (and shop-vac), CA, and just sanding sealer.

Any takers?

wfcook said:

I find that the CA produces a shell that can be sanded to a very smooth finish, but that it doesn't penetrate very far. It cures very quickly when it comes in contact with the wood and it seals it up. I also find that the resulting shell of CA isn't very tough and doesn't handle impacts well.


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This is true to an extent... the real key is to FLOOD the CA onto the surface of the cone as fast as it will "drink it in". If you daub some on and let that cure, it will prematurely seal off the surface and the subsequent applications just roll around, drip, run, sag, etc and make the surface rough and hard to sand...

A lot depends on how dense and fine grained the balsa is... the tighter and finer the grain, and the denser the part, the less the balsa will "suck in" before it cures and seals off the pores. Lighter, more porous balsa with coarser grain and larger pores will suck in a lot of CA before sealing off... I've had it drawn by capillary action all the way through the cone on especially light cones and nearly glue my fingertips to the shoulder before sealing off before. It also will sometimes smoke or get pretty hot, due to the rapid curing (and any presence of moisture kicking off the reaction inside the wood).

It is true though that "hardening" balsa parts with CA WILL NOT make them "bulletproof". At best you get a somewhat harder and somewhat more ding-resistant outer surface, with the degree of hardening really dependent on how much CA the wood absorbed before sealing off. With severe enough impacts, the surface will be crushed into the softer, unhardened balsa below... so it's not going to make a balsa part as hard and ding resistant as say a plastic part...

Later! OL JR

I recommend odorless thin CA. It's a lot easier on the nose and sinuses.

Rob Campbell said:

I recommend odorless thin CA. It's a lot easier on the nose and sinuses.

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Did'nt know there was such a thing.

also called 'foam-safe'.
Rex

But what I wanna know is why Sis doesn't SAY anything....
Have you got another one up your sleeve?

Kirk G said:

But what I wanna know is why Sis doesn't SAY anything....
Have you got another one up your sleeve?

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She can't say anything, her Larynx was crushed when she sustained all that crazy Damage. She also suffered quite a bit of Head Trauma, seeing as how she's all Head, so now she's kinda' in a Vegetative State.