What's the REAL story about ammonia?

I've often heard that ammonia makes crooked balsa "correctable".

Also, some guys told me that even though it is so, in case I crash, the "ammonia corrected" balsa would will become balsa dust., and the whole thing would get beyond repairs.

I'd like to get this settled for good...

God bless you all!

In Christ,

Water pretty much will do the same job, without the smell.

Hi Ion,

Nice to see another brother in Christ posting here,

I use water only. I run the hotest water I can in the bathtube and soak the wood an hour or so. Take it out and towel it off and then straighten it by bending in the opposite direction of the warp. Hang it vertically to dry. Most balsa will straighten this way though I have had some that would not respond and would just take its original shape when it dried, but this has only happened twice out of many times. This wood I toss and start over.

Ammonia breaks down the fibers of the balsa and makes it plastic (pliable). When it drys that balsa in not structurally the same as it was pre-ammonia, thats why it sometime disintegrates on impact.

Randy

I use very hot tap water and amonia. Yeah the smell is awful but I really dont care. I do it only a few times a year so what is the big deal. With Amonia I only have to soak the piece for about 5-7 minutes before it is ready to be wrapped around or pressed flat. I have tried it both ways amonia helps it bend more and stay there once it is dry.

Ashes to ashes balsa dust to balsa dust. After it receives some dope and covering it is plenty strong and should last just fine. Crashing is another story. Yes it may not be as storng under a crash situation but up until then it will have remained straight and been a good flier. Without the amonia to fuly break it down and let it dry up and take new shape it may try to find its way back and warp later. Then it will never trim out. May take a crash better but never fly as good. Its your choice of course. I use about 60-40 water to amonia mix in the bath tub. Makes for good molded shells and leading edges of the wings and stabs. Not to mention after the molding is done I clean the tub with the amonia water. The wife like that part.

DMoon

I'm convinced that the ammonia works better in preparing the wood for molding. I use it straight - yes, it is rough on my eyes and lungs, the wife always comments (sweetly) that the "garage really stinks, Larry". But it WORKS so well!

As for compromising the strength of the molded part, I couldn't disprove that premise. But I do know is that my laminated molded sheets are extremely strong, particularly after being doped and tissued (and/or fiberglassed). More than adequately so.

L.

"My phone number is 17. We got one of the early ones."

I would totally advise against the use of ammonia. I used it a couple of times to mold parts the way I wanted them, and over time it destroyed the wood. The key here is "over time." Immediately afterwards you may not notice a difference. In time you will. In a crash it will shatter. If it is that brittle, it will break on its own if a heavy load is placed on it (like the wing shearing). If you think it makes no difference, take two pieces of equal weight/strength wood and soak one in water and soak the other in ammonia. Let them air dry and then put them away for a year or so. Then take them out again and apply weight/pressure to each. The ammonia wood will break far sooner than the other.

So:

If it "doesn't make any difference" you have overbuilt the structure. Use lighter or thinner wood to begin with (but not ammonia). And if you build it the way it should be built (strong enough in flight without the ammonia wood) it will shatter in flight.

Use water. If that is not good enough, dump the wood (see the thread about throwing away bad parts) We don't make them good by weakening the structure.

Leonard Neumann

I have always used a mix of ammonia and water to bend balsa. Not only that, but I heat it to about 180 deg F. if I can find a large enough pan to put on the stove-top. I am told that ammonia breaks down the lignin in the wood and makes it super flexible. But once formed and dried out, it seems to be just as strong as original.

Ammonia also discolors the wood, but if painted, it doesn't matter.

I use this method for molded turtledecks and laminated wingtips.

This is based on fuzzy understanding and memory of stuff I have read, not experience. The function of the ammonia is to uncouple the lignin and subrin molecules in the wood. Balsa has little or no lignin or subrin, so ammonia is not needed for that function. In woods with lignin and subrin, the molecules will recouple and the strength of the wood is not impared.

The problem is getting the balsa wood completely wetted, and ammonia may help with this. I suspect a tiny bit of detergent in the water might be better. If I were going to go into balsa moulding big time, I would fix up some kind of gadget to asperate the balsa to suck all the air out and replace it with water.

>This is based on fuzzy understanding
>and memory of stuff I
>have read, not experience.
>The function of the ammonia
>is to uncouple the lignin
>and subrin molecules in the
>wood. Balsa has little
>or no lignin or subrin,
>so ammonia is not needed
>for that function. In
>woods with lignin and subrin,
>the molecules will recouple and
>the strength of the wood
>is not impared.
>
>The problem is getting the balsa
>wood completely wetted, and ammonia
>may help with this. I
>suspect a tiny bit of
>detergent in the water might
>be better. If I
>were going to go into
>balsa moulding big time, I
>would fix up some kind
>of gadget to asperate the
>balsa to suck all the
>air out and replace it
>with water.
>

Like a vacuum pump.

I've only used it 2 times, the first was on a fully symmetrical wing with D-tube structure. The front of the wing had a lot of curve and the sheeting was very hard and didn't want to bend. I just used an eyeglass cleaner that I had with amonia in it, in a small pump bottle. It workd fine until I ran out, and had to use plain water, definitely didn't work as good(straight from a pump bottle), so I used it again on the fuselage for a Corsair I am building now. The first plane is still flying after 2 years, so I'm happy that it didn't hender the strength. Never thought about hot water, but that would have probably worked too, but using the amonia(now straight, lemon scented) to just spray on as needed works for me, and I don't seem to get a lot of fumes this way.

mouse

A good video on balsa molding is the "Balsa Molding Techniques With Bob Hunt & Bill Werwage" from Robin's View Productions. Both Bob and Bill use hot water with a "generous amount" of ammonia. Bill mentioned that the plane he shows has over 1000 flights and does not even show stress cracks.
Perhaps the difference is in the concentration of ammonia. Added to water it seems to make the balsa "wet" faster. A right out of the bottle concentration may affect the wood differently.

I guess I've made as many molded fuselages as anyone. these include two Sea furys, four Mustangs, two Millenniums F-51s, two classic Bearcats, two Quick Build Bearcats, a P-47 and A DH Hornet. These were not turtle deck add ons. They were completely molded fuselages. In my opinion water is all that is required and all that I have ever used. Small pieces are molded in sinks. Fuselage halves and wing leading edges are wet in the bathtub. I don't know if amonia hurts the strength of balsa, but why take the chance. Water works.
Al

Al,

Forgive me for intruding here, but another interest of mine is wooden boats (the full-size stuff). Mind you I NEVER said I actually liked going out on them, I just like the boats as an art form (hee hee hee!).
An OLD technique for building a planked hull is to use a steam box to steam the planking (sometimes other parts of the hull as well) until it is soft and pliable. When it is ready, it is then pulled from the box, quickly positioned and nailed in place.
I was curious if anyone has ever used this in (aircraft) models rather than just hot water or soaking. I know steam is an ancient technique for warp removal (so is boiling water). I have no idea if this would be better or worse for balsa than other woods, merely curious.

I don't see how steam could be used to make airplane parts. I don't plank hulls.
Al

>I don't see how steam could
>be used to make airplane
>parts. I don't plank
>hulls.
>Al

Hi Al,

I was just wondering if the steam would speed up the process vs soaking in plain water.
The full size WW-2 US Navy Timm N2T (I think that is the correct designation, don't quote me though!) trainer used a "Duramold" construction technique in which the fuselage shells were formed under heat and pressure in a mold. I think Howard Hughes was involved in this somewhere along the line.
I also THINK Top Flite may have used the steam (or just heat) and press on a form method for their "Superform" line of kits. Given the time factor envolved, I'd be real surprised if they had a bunch of tanks out in the shop soaking balsa sheets for the next run of kits, although it might well have been so.

See ya!

Water works. It is simple and easy if not as quick as a manufacturing method. What is your hurry? Why try to introduce exotic methods into what is a very basic and simple procedure. In short, it works for me and I build a lot of molded airplanes so I speak from experience. If you want to try to introduce ship building methods to stunt ship fuselages, be my guest. I doubt the result will be as light as a molded 3/32" balsa shell which is strong enough.
Al

I think John was suggesting the same building materials and molding techniques that you use with the exception of steaming the wood instead of simply soaking in water. I know the builders of the wooden ships had only a couple of minutes after removing the wood plans from the steam to form them into place, so the heat must have made it more pliable. But that may be the "clinker". If you could form it quick enough around the mold before it cools, it might be more pliable for the short term. Matt has simply used water for the parts he has molded, and that, for those parts, has worked fine for him.

Leonard Neumann

Jake: Well, of course, we use steam to de-warp wings, per the old GMA instructions. But this is an open structure, and it is after the fact.

Surely works well, though. I have a Super Ringmaster that had an Industrial Strength warp in one of the wings. A couple of minutes over the stove, and it disappeared. Plane flies well, and too fast, with a Johnson S .33.

I was mainly interested in the time factor. How long must one soalk balsa vs. steaming it to get the same results. The steam bending of wood is hardly an exotic method, it was and is used in furniture making also.
I was only curious if anyone had tried applying it to models as a time saver. I will have to give it a shot and see how and if it works. Thanks for the input, your ships are truly beautiful; flying art work.

Best wishes,

Whattasmatter John. No bathtub? Steaming balsa might work for small parts but I doubt that the wood could be kept hot or wet long enough to wrap a full fuselage half to a 40" long mold with strips from a twin bed sheet using nearly half a sheet worth of strips. If you are going to mold, and from the sound of this thread, I doubt it, you are going to find out, to make parts bigger than turtle decks, the wood will probably have to take a bath. Amonia not required. End!
Al

I've been molding with water and ammonia since 1974. Don't remember where I read it but the article I fot the info from indicated the ammonia softened the lignin in the wood (the pitch in the grain for want of a better description) allowing a greater degree of molding without breakage. The most important aspect of the ammonia was supposed to be the fact that the lignin rehardens after evaporation and helps the balsa to lose its *memory* and remain in the new shape.

This appeared to be true. My 1977 concours winning Citation had all the top and bottom blocks *and* the bubble canopy molded in this fashion. The canopy was particularly impressive in that it had no tendency to spring back to its flat shape and, to this day, it sits up in the attic loooking like it did when first finished. It has, to the best of my recollection, no internal structure to support it.

Re strength. The current Final Edition was built with the first ever (I think) molded leading edges using the water/ammonia mixture. This is the same plane that was the Great Expectations which flew in the 1994 World Champs and was completed the previous year. I don't know how many flights it has on those leading edges but it's a bunch. To date there is no indication of failure. This is true even though the ship was stripped to bare wood and then had the wing leading edge and center section sheeting covered with CF veil while refinishing in the purple pond scum theme, thus making a potentially very hazardous stress riser right at the fuselage. Again, no apparent damage has occurred.

(Please note re the above. This ship was built with three carbon fibre reinforced spars and is very rigid in spanwise flex as a result. I do *not* advocate doing what I did on a wing which doesn't have such substantial sparring. A failure at the stress riser of the fuselage is predictable for such a condition.)

If, in fact, strength after molding isn't an issue for ammonia based molding I think one could say the following. The use of ammonia does allow a greater degree of curvature before splitting (I do top and bottom blocks all the way down to the tail post using either multiple layers of 1/32 or a very good A-grain 3/32 single sheet. The resulting radius at the tail post is about 1/8 inch or a touch less.

In addition, I believe the ability of the part to retain its shape is enhanced. When the Ace bandages are removed from parts molded with the ammonia mixture the part has to literally be "popped" off the mold due to its willingness to remain in its new shape.

I'd say if your project requires serious radius curves or any sort of compound curving the ammonia probably makes sense. For more modest shapes which will, in the final analysis, be supported by bulkheads or ribs, etc. the ammonia is probably overkill.

Al

Yes I do have a bathtub, but I also have a small tank that I use for soaking wood (laminate tip outlines for FF Rubber Scale, etc.). Stunt is a lovely field, but my main interests are Scale and Carrier. I was thinking the difference between soaking the balsa and steaming it might be like in cooking for example; slow soaking beans or other veggies vs pressure cooking them. You get the same results, just one is much faster. I'll have to try the steam bit and see what happens.
Still have the AAM issue with your Mustunt article in it, GREAT stuff!

See ya!