Hardening a Balsa Nose Cone

[jdud]

Is there any way to harden a balsa nose cone? I want to harden a rather large BT-80 cone to keep it from getting dinged up in transport and flight recovery.

I've seen the Minwax wood hardener at the hardware store (anybody have any experience with this stuff?). I also thought about fiberglassing the cone, but was not sure how well glass would do the compound curves.

 

[troj]

Folks have reported success with the Minwax Wood Hardener, so that's likely a good approach.

Fiberglassing the nosecone would work, provided you used a harness satin weave cloth. Anything heavier than about a 3oz cloth would also prove more difficult to get over the tip of such a small nosecone. And really light fabrics generate their own "fun" getting them to cooperate.

Another option would be to mix up a batch of a laminating resin (not standard 1:1 "construction" epoxy, as it's too thick) and painting it onto the nosecone. This will penetrate the wood, like the Minwax product, and stiffen the fibers.

The first and last option are the best; I wouldn't recommend the fiberglassing option. Which one I'd suggest depends on whether or not you already have any laminating resin -- if you have the appropriate epoxy, why buy another product? But if you don't have a use for a laminating resin, the Minwax product is likely to be more beneficial to you.

Also, understand that any such method only protects the surface layer -- a hard enough whack will penetrate through to the soft center. But, it will protect the nosecone from the typical dings and dents.

-Kevin

 

[JoeG]

All good ideas. The easiest and fastest way I have found is to saturate it with thin CA. I'm always looking for easy and fast.

You will be surprised how much harder it makes balsa with very little weight gain.

Joe

 

[jim fustini]

30 minute epoxy with micro balloons works good. Work it in good with a stiff brush.

 

[MarkII]

I have used thin CA to harden small nose cones (BT-50 and smaller), but not that often, because smaller ones don't seem to need it as much. (They don't get dinged as much with casual handling.) The CA works great, but it takes a lot of sanding to smooth it out. Although obviously it would work just as well on a larger cone, I can't imagine what it would be like to coat a BT-80 cone with it. How much CA would a 2.6" diameter balsa nose cone suck up?

I have used Minwax wood hardener on large cones. It definitely does give them good protection from incidental dings and dents. I pour some hardener into a disposable plastic cup (polypropylene - it will melt PET and other types of plastic) and then brush it onto the cone with a chip brush. I do this outside, because the fumes from the product will melt your brain. I always shake the can vigorously for 3-4 minutes to thoroughly mix the product before I pour some into the cup. Then I hang the cone by a screw eye inserted into the base and let it cure. In my own experience, it has taken about 24 hours to dry to the touch, but I have found that leaving the cone alone for a week or more seems to result in enhanced protection. I often repeat the process for a second treatment, which also seems to help. The Minwax will also seal the balsa grain, but it will not fill it. After the Minwax has had time to thoroughly cure, I fill the grain with a brush-on liquid wood filler (Delta Ceramcoat All Purpose Filler).

A few months ago, I accidently dropped a 2.34" diameter nose cone that had received this treatment onto the linoluem-tiled floor of my workshop from a height of about 4 feet. I had given this cone two hardener treatments, allowed it to cure for an extended period of time, sanded it and then gave it another hardener treatment. After another extended cure time, I filled the grain with 3 coats of Delta Ceramcoat. It was hanging by its screw eye on a dowel, waiting for me to get around to wet-sanding it, when I bumped into it and knocked it off the dowel onto the floor. It bounced off a couple of things on its way down and then did so again after it reached the floor.

:y: :y: :y: :y: :y:

When the blood finally returned to my head, I picked the cone up and examined it for dents. I couldn't find any, though; the cone didn't have a mark on it. :w:

MarkII

 

[troj]

I've not had the best luck with CA -- I find that it leaves a very thin "hardened" coat and it doesn't take much to punch through it.

Sanding it smooth afterwards is also a rather...unpleasant....task.

-Kevin

 

[sandman]

When I want a nose cone to be really tuff I make it out of basswood.

But that's just me.:blush:

 

[MarkII]

When I want a nose cone to be really tuff I make it out of basswood.

But that's just me.:blush:

Well, you are in the rare position of having that option.

MarkII

 

[m85476585]

I don't like Minwax wood hardener. Everything I have tried it on has just become impossible to sand, but not much harder than plain wood. Thin epoxy would probably work a lot better.

 

[troj]

Well, you are in the rare position of having that option.

Gordy would be more than happy to help you use basswood for nosecones, too.

For a small (very reasonable) fee, of course....

-Kevin

 

[sandman]

Gordy would be more than happy to help you use basswood for nosecones, too.

For a small (very reasonable) fee, of course....

-Kevin

Well.....yes, I would.

 

[MarkII]

Gordy would be more than happy to help you use basswood for nosecones, too.

For a small (very reasonable) fee, of course....

-Kevin

Oh, I knew that...

I don't like Minwax wood hardener. Everything I have tried it on has just become impossible to sand, but not much harder than plain wood. Thin epoxy would probably work a lot better.

I wasn't too impressed with it at first, either, and I said so on the forums on a few occasions. But then I changed my mind, after seeing the cones again after more time had passed. Give it time, lots of time. Sand your nose cone smooth first. Then give it more than one treatment with the hardener. And then allow it plenty of time to cure; I'm talking about a week or more. Yes, you can sand it, with good, fresh, sharp sandpaper. If it seems to be gummy when you sand it, it hasn't fully cured yet. The hardener in a large balsa cone, like one sized for Semroc LT-225 or Estes BT-80, can take a long time to fully cure. The surface may be dry and no longer tacky, but the hardener inside the cone is still curing. The cone will still pick up dings easily until the interior is completely cured. Sanding it when it is fully cured will produce fine, dry, talc-like white dust. But don't try to sand out gaps and other imperfections; fill them in and build them up with filler, instead.

MarkII

 

[AKPilot]

This product, although I haven't personally used it, has infiltrated the r/c guys with both foamies and balsa products and looks very promising:

Liquid Sheeting II

 

[Zeus-cat]

If the wood is already dented, you can work the dent out with a clothes iron. I have used this trick on soft woods like balsa and pine.

The idea is to get moisture into the wood and apply heat to make the water turn to steam and expand the wood. Done carefully you can reduce or eliminate even fairly large dents. Keep the iron moving so you don't scorch the wood.

 

[jcsalem]

All my balsa nosecones get several coats of Delta Ceramcoat's All Purpose Sealer. It leaves them significantly harder. It's not fiberglass but it helps resist dents while transporting.

Or are you looking for something harder?


Ceramcoat is found at Michael's. Coat, sand, coat, sand, coat, sand. It sounds like work but the sanding goes very quickly after the second coat.

Jim

 

[AKPilot]

With all of this sanding on balsa n/c's, I've always had a problem with the shoulder becoming too thin or even on existent.

How do you prevent that?

 

[foose4string]

With all of this sanding on balsa n/c's, I've always had a problem with the shoulder becoming too thin or even on existent.

How do you prevent that?

I usually sand the nosecone while it's seated in the corresponding body tube. That will prevent it from getting too thin at the shoulder as the tube acts as a guide/gauge. You could probably use a few wraps of tape around the base to achieve the same thing, but the body tube is already the correct diameter.

 

[jdud]

Thanks for all of the great comments and suggestions. I've been keeping up with the thread, but have not had time to respond - things have been a little crazy this week.

I already have some laminating resin, so i may go that route - mixed with some micro-balloons. Would it be better to thin the resin with some denatured alcohol to help it penetrate the wood more efficiently?

I read a little about the minwax hardener over at a knife making forum. Those guys use it on the carved handles and have the same advice regarding the long curing time. It is apparently a thinned resin as well and must have a long curing time for the interior of the object to fully harden.

With all of this sanding on balsa n/c's, I've always had a problem with the shoulder becoming too thin or even on existent.

How do you prevent that?

I do the same thing as foose does in regard to sanding nose cones - put them on the corresponding body tube. I usually fill the spiral groove on the body tube, so the nose cone also prevents the sandpaper from ripping the outer layer of body tube at the end of the tube.

 

[AKPilot]

Well I've been searching but, I haven't been able to find any Miniwax Word Hardener in any chain or local hardware store.

So I called up a local, specialty, hardwood store and asked them what they'd recommend. They recommended Bondo Rotted Wood Stabilizer found here: Bondo Rotted Wood Stabilizer

So I picked up a can for $14.00 and dipped some scrap balsa into it. Kinda weird because as this stuff soaks in, there's a few tiny-tiny bubbles coming out of the balsa - as if the air is being displaced.

You can redip every two minutes and then it hardens within two hours. Hasn't been two hours quite yet, but I did a quick check to see how it would take a ding. It faired considerabily better than untreated balsa. Also, it doesn't seem to leave any reside on the surface thereby making sanding a breeze.

So there you go . . .

 

[foose4string]

Well I've been searching but, I haven't been able to find any Miniwax Word Hardener in any chain or local hardware store.

So I called up a local, specialty, hardwood store and asked them what they'd recommend. They recommended Bondo Rotted Wood Stabilizer found here: Bondo Rotted Wood Stabilizer

So I picked up a can for $14.00 and dipped some scrap balsa into it. Kinda weird because as this stuff soaks in, there's a few tiny-tiny bubbles coming out of the balsa - as if the air is being displaced.

You can redip every two minutes and then it hardens within two hours. Hasn't been two hours quite yet, but I did a quick check to see how it would take a ding. It faired considerabily better than untreated balsa. Also, it doesn't seem to leave any reside on the surface thereby making sanding a breeze.

So there you go . . .

Looks like a very similar product and possible alternative. I think a common misconception with this product is that it's going to make the cones rock solid. I does not. It does make them less susceptible to dings and general wear, makes them quite a bit harder than untreated balsa, and makes for a decent wood sealer. Don't be in a rush to sand, although I've been able to do so in a matter of hours, but I brush mine on. I've never dipped and I wonder if that has contributed to the bubbling. Let it dry completely before sanding, adding filler, primers and such. You know the drill.

 

[The EGE]

I use plain old Elmer's Carpenter's wood glue. I just spread it on with my finger and let it dry. 1 coat will make pre-sanded balsa fins smooth; 2 coats is good for tight-grained nose cones and unsanded balsa; and 3-4 coats will make even the weakest balsa cone incredibly smooth, very strong, and ready for paint.

My machbuster survived a ride to 4000 feet on a G78G with no more reinforcement to a thin cardboard tube and balsa cone than 3 layers of wood glue, and the front cone on my Nike-Apache (6" long and 1" in diameter) has survived several hard landings, multiple doorframes, and a ceiling fan :eyepop:

Wood glue is also good for protecting the shoulder of balsa cones from crushing and heat. I coated the shoulder of the Mozzie (thin, light balsa) with wood glue after it got burned by the charge of an F23, and it's been good since.

:2:

~~~~The EGE

 

[AKPilot]

Sorry, I forgot to mention that there was no noticeable expansion or deformation.

 

[Micromeister]

Well I've been searching but, I haven't been able to find any Miniwax Word Hardener in any chain or local hardware store.

So I called up a local, specialty, hardwood store and asked them what they'd recommend. They recommended Bondo Rotted Wood Stabilizer found here: Bondo Rotted Wood Stabilizer

So I picked up a can for $14.00 and dipped some scrap balsa into it. Kinda weird because as this stuff soaks in, there's a few tiny-tiny bubbles coming out of the balsa - as if the air is being displaced.

You can redip every two minutes and then it hardens within two hours. Hasn't been two hours quite yet, but I did a quick check to see how it would take a ding. It faired considerabily better than untreated balsa. Also, it doesn't seem to leave any reside on the surface thereby making sanding a breeze.

So there you go . . .

AK: I picked up another can last weekend at Lowes in the paint and trim dept. I'm actually using it on a cabinet project but have in the past used it on an occasional nose cone if it seemed to be of the ultra soft "contest grade" type light weight balsa.
Have to say though, by the time we get 3 or more coats of primer and a couple coats of paint I just haven't seen all the much damage done over the years to warrent Hardening most average balsa cones.

 

[AKPilot]

Interesting that you found it there, in the same areas I've been looking - in multiple stores. I've even asked customer service and other employees where I'd find it. Maybe I should simply ask if they could order it.

Having said that though, the Rotten Wood Stabilizer is working just fine and I can find it within 2 miles of the house consistently.

 

[foose4string]

Interesting that you found it there, in the same areas I've been looking - in multiple stores. I've even asked customer service and other employees where I'd find it. Maybe I should simply ask if they could order it.

Having said that though, the Rotten Wood Stabilizer is working just fine and I can find it within 2 miles of the house consistently.

No doubt you were looking in the right place. It's usually near the other Minwax products(stains and such) so it's not too hard to find. I found it at Lowes also. Looks like you found a good alternative.