Try an experiment

[RC Storick]

I want everyone to try an experiment with steam. I see in a lot of places some have no faith in the power of steam. So here is what I want those who have no experience in steaming to try. Grab a 1/4 or 1/2 x 3 x 24  scrap sheet of hard balsa. Get your wife's tea kettle (with her permission) fill it 1/2 full and set it on the stove. Wait until its wistling and start heating the plank. The stiffer the better to prove my point. Hold it over the steam about 6-8 inches from the spout. Get both sides hot and start twisting that board. It will move small amounts at first but keep steaming until you have a big twist or until you have straightened it. Your choice.

As the power of the wood breaks down it will move more and more. This works through painted wings and it will work on foam wings. However foam requires more time.

Try it first before telling me it doesn't work it does every time without exceptions.

[RknRusty]

Okay I have a new Skyray kit that I'll be starting on next month, and the fuselage is bowed toward the inboard side, plus it's twisted slightly. I doubt if I can make it worse, it's useless as it is now. So I'll try the steam treatment and then clamp it flat on my glass to dry. I tried spraying it with cold water and weighting it but it didn't help much, if any.

Rusty

[Peter Grabenstein]

Many month ago I went to my LHS and had a look of a ARF Primary Force Kit.
The fuse had a bad left bow inside circle.
My idea was using hot steam to bend the fuse back into straight.
After I was thinking,what will happen if the ready build model stays in the hot sun for hours ?.
Will the fuse work again and the inside bow comes back ?.
I asked the Manager to order a second Kit what he did.
The TE of the wing on this was twisted like a prop. .
My thinking, the wood was too fresh and too wet (not dry) when they build those Kits.
I didtn make the Experiment for that amount of mooney.
What goes away may comes back, sooner or later ?.

Peter

[Randy Cuberly]

Uhhhhhh....I would mention here that some aliphatic resin glues will simply turn loose of thier bond with the application of very much steam.  Can you spell "fall apart"? 

Randy Cuberly

[Douglas Ames]

I don't see where using a little steam judiciously would hurt.
Not sure if it would work with a monokote covered wing ? Might have to strip the covering first.

[Derek Barry]

Derek

[Dennis Adamisin]

Derek:
I watched the vid and still say IMPOSSSIBLE!  BTW that looked like balsa from my LHS...

[Avaiojet]

They would steam layers of wood to make ribs for ships, small and large.

[Doug Moon]

Next time you are near a grand or baby grand piano take a long hard look at the "rim."  That's the outer piece of wood that creates the shape from the top view.  That is steamed wood bent to shape in a sauna. It's actually quite impressive.  That is not balsa wood either. 

There is no doubt steam works.  Its a powerful tool and its been used for years for many many applications. 

[Randy Ryan]

This is a very well known practice for grand piano makers, huge laminated hardwood planks are steamed and clamped onto forms. These parts are dried and they stay put.

I have on occasion soaked entire structures (provided the glue is waterproof) and clamped fixtured to remove warpage. One in particular was the stab of a large rubber model which had all the spars swept back at the tips. When I took it off the bench it went all kinda ways! I threw it in the bathtub in hot water and let it soak a while and when I took it out it was noticeable less stiff. Clamped and let for a couple days it was perfectly flat and straight and even after years it still is.  I have never imersed a stunter wing though I have wetted the sheeting and blocked it reversing the warp and had great success. Wood is an amazing material

[john e. holliday]

I did that in Aunt Betty's kitchen one year at a VSC in Tuscon one year.  It works and stays from my experience.   Didn't have a place for the King Sweep to steam it out.

[Russ Danneman]

i have used my "as seen on tv"  shark{floor steam cleaner} b4 worked perfect.rd

[RC Storick]

My friend Ron Otoole and I have been steaming together 25 years and never broke a part and always fixed every warp. If there is a lot of power in the wood we have to steam it a few times but it ALWAYS works!

Trick is go slow and try not to over twist things before they are soft.

[Peter Grabenstein]

I don't see where using a little steam judiciously would hurt.
Not sure if it would work with a monokote covered wing ? Might have to strip the covering first.

SURE I would strip the covering first before I do the "hot steam trick".
But NOT with an ARF and that amount of Money I have to pay for.
I left it in the shelf ,like what I did.

[RC Storick]

It works through monokote,silkspan,silk and even a foam wing. Mater of fact works better if the plane is finished and flown so you can see exactly what it needs. Even fix a built up twisted fuse.

[john e. holliday]

Of course most people will not believe this and will never try it.  It helps also on bigger planes to have an extra set of hands and ey balls.

[Phil Krankowski]

Don't overcook or you get overcooked asparagus...so limp it can't help but crush under any bending.  Also overcooked wood is weakened permanently.  Wood is pretty amazing stuff, and quite capable of taking on rather wild shapes from steam bending. 

The rule of thumb is an hour per inch, but that is based on much larger stock sizes.
http://robroy.dyndns.info/baidarka/bending.html

I'm not sold on cooking a covered model, but I am sure it can work in the right circumstances.

Phil

[RC Storick]

Don't overcook or you get overcooked asparagus...so limp it can't help but crush under any bending.  Also overcooked wood is weakened permanently.  Wood is pretty amazing stuff, and quite capable of taking on rather wild shapes from steam bending.  

The rule of thumb is an hour per inch, but that is based on much larger stock sizes.
http://robroy.dyndns.info/baidarka/bending.html

I'm not sold on cooking a covered model, but I am sure it can work in the right circumstances.

Phil

Steam form a tea kettle works every time. No Exceptions!  Where are the challengers to this statement? Every time no EXCEPTIONS! Some problems just take a little longer.

You have to break the woods power but steaming it past straight and letting it settle into straight.

[Michael Massey]

Here is another 2 cents.

I have had a number of occasions (actually more than I would care to confess to) where I have completed a new plane, using my traditional silk and butyrate dope, only to find it needs the wing de-warped (or warped in another direction).  Here is what has worked very well, every time, for me.

I "clamp" the offending part of the airplane (always the wing for me) into the desired spot.  Measure (or whatever else) to insure it is where I want it to be.  Then when my wife is not looking, I soak about 6 to 8 hand towels in water and wring them out, not dry but simply remove the real excess water.  I then put those towels in a large plastic bowl and microwave them for about 8 minutes, using 2 minute intervals.  (Not sure why the 2 minute intervals other than I am very cautious with anything in the microwave that could "trap" the sudden heat build up of prolonged and continuous "heat.") 

Then, using gloves for protection from the heat and steam, I lay the towels on the part to be de-warped/warped.  I usually, but probably not necessary, cover those towels with a plastic cover just to further trap the steam.  I let it sit for a couple of hours, remove the towel and usually leave it clamped over night just for good measure.

It always works well.  The finished is not effected by the hot towels and the part de-warps/warps to where you clamped it.  No need to allow for "spring back" or other movement when the clamps are removed.  It stays where you put it.

I would take credit for this simple yet effective method but in all honesty, I picked it up from Floyd Carter.

Give it a try next time you need to remove a warp.

Oh by the way, be very careful picking up the plastic bowl from inside the microwave.  If you should accidently pull out the class "shelf" on the bottom of the microwave, and it should fall to the Granite counter top, add in about $50 more, or so, for that particular project.  Don't ask.

[RknRusty]

I want to try this on the kit fuselage I mentioned above. I am wondering how much the ambient humidity where it's stored has to do with warping. Is there an optimum level of humidity that balsa should be kept in? My shop is drafty and unstable temperature and moisture-wise, but maybe after steam straightening it, I should keep it inside the house until I dope it. After that I suppose it will be sealed up at whatever moisture content it has when doped.

I'm concerned about this one enough to think about cutting a new one because it's bowed to the inboard side.

Rusty

[Steve Helmick]

Rusty, I am thinking that part of your problem with the profile fuselage blank is/was letting it 'dry' on your glass table. It's going to dry slower on that side and might therefore cause warping instead of curing it. Even with steam, I think you need to avoid doing that. Possibly a towel between, and hopefully repeated on topside for similar drying rate from both sides?

When I started in the machinist's trade, I worked as a hydraulics mechanic in a fishing boat shipyard in Ballard, the Scandinavian part of Seattle. Still a fair number of wooden fishing boats then, and the carpentry shop was always busy. Lots of lovely teak interior work and a lot of "ironbark" (aka ironwood) for keel caps, gunwale caps and rub rails. The rub rails went right 'round the stern, which meant they had to be pretty severely curved. The process was to put the 20'-30' long 2" x 8" (or so) in a tubular steaming oven. A very large steam cleaner was attached and fired up. Preparations were made...fasteners, drill motors and drill bits were readied, along with lots of clamps and come-alongs. It was pretty impressive to see a big hunk of that stuff bent around the stern of a boat! FYI, "Ironbark" as it was always called, is so dense that it will not float in water.

I think it was Lee Hines that told me about the hot towel trick, many years ago? Yeah, the Sweepette HLG guy.  Basically, wrap a towel around warped item and pour the boiling water on it.  Steve

[RC Storick]

All you need is a tea kettle.

[Steve Helmick]

All you need is a tea kettle.

Try the towel, and pour the water out of the tea kettle. You'll like it.  Steve

[RC Storick]

Try the towel, and pour the water out of the tea kettle. You'll like it.  Steve

Its the super heated steam that breaks the fibers down to allow you to twist it. I don't think the towel trick would be good on a painted wing.

[Brett Buck]

Its the super heated steam that breaks the fibers down to allow you to twist it. I don't think the towel trick would be good on a painted wing.

    It works, and just about instantly. Actually, in the hard cases, you can put a dry towel on the part, twist, and then have someone pour the boiling water into the towel. You can feel it give almost immediately. You also don't need to "go past", just get it straight and hold it there until it cools off.

      Brett

[RC Storick]

    It works, and just about instantly. Actually, in the hard cases, you can put a dry towel on the part, twist, and then have someone pour the boiling water into the towel. You can feel it give almost immediately. You also don't need to "go past", just get it straight and hold it there until it cools off.

      Brett

I have not tried this method but I will try it sometime of coarse I hope not to.

[Brett Buck]

I have not tried this method but I will try it sometime of coarse I hope not to.

   Of course. you would rather have it straight in the first place. It takes some nerve to pour boiling water on a finished airplane, but so far, no damage. It's exactly the same effect and mechanism as the steam, just much faster.

     Brett

[RknRusty]

Okay, thanks guys. I'll report back with how it goes. Hoping for some weather that makes occupying the shop not so unpleasant.

Rusty

[pipemakermike]

Anybody who has made acoustic string instruments needs no persuasion of the power of hot water or steam to bend wood.  Some of the curves on a violin or a mandolin are quite extreem.  Have a look at my "bending ribs" page:-
http://www.machineconcepts.co.uk/mandolin/mando2.htm

[Avaiojet]

I may use steam to bend the .5" thick LE to the elliptical wing I'll be building.

Possibly better than laminating layers of thinner wood, say four pieces of 1/16".

My concern would be that the wood has a memory. Will, after a period of time attempt to straighten?

[Will Hinton]

I have the cherry guitar sides for a jumbo acoustic ready to soak over night in the shop right now.  Then I use a heated "bending bar" with a 4 inch diameter to do the bending.  The combination of thoroughly wet wood and the heated bar create the steam.  The most amazing wood to steam is maple.  That stuff is sooooo hard, yet with the steaming it becomes like a limp dishrag.

[RknRusty]

...My concern would be that the wood has a memory. Will, after a period of time attempt to straighten?

That's what I was concerned about, thus my question about humidity. Thinking it might change shape as the wood's moisture content shifts. But with the extreme fiber busting of the steam treatment, maybe not.

Rusty

[RC Storick]

Wood does have a memory and with steam you change its memory. I cant remember the name of the fiber/chemical that steam changes but you train it to live in its new position .

[Lauri Malila]

It's called lignin, Robert. It is the "glue" that binds wood fibers together.
Actually, the main thing in the process is the heat, water steam mostly just helps in heat distribution as wood is a good insulator. You can do miracles with just a heat gun but things burn up easily.
I re-pitch my wooden props with heat gun, just like carbon ones. You just have to heat the wood very slowly to get also the core hot without burning the surface too much. I tried steam first but it was not good with props as they tended to deform a little during drying. With just hot air, they are allways bang on and stay as I set them.
As you said, it's allways a surprise how plastic wood gets as you get past the certain (about 100C) temperature.
But I do use steam, to tweak my Carbon Free Flight wings!

L

[RknRusty]

Lauri, how do you gauge the pitch when you reshape a prop, is there a tool to measure it? It seems like eyeballing it wouldn't work for something as critical as that. Especially on a three blade prop.

Rusty

[Andrew Saunders]

Dennis. i do custom woodworking and cabinetry. What you saw in that video That Derek Barry posted with the wood block and the nail is not impossible. We use hot water and steam all the time to manipulate wood. What he did in the video is very possible. Just takes patience.

[Steve Helmick]

Lauri, how do you gauge the pitch when you reshape a prop, is there a tool to measure it? It seems like eyeballing it wouldn't work for something as critical as that. Especially on a three blade prop.

Rusty

Use a pitch gauge. Prather used to make them (I have one of those), a few others have been produced in small batches. There's the "Hooptee", detailed in an article in AAM/MA by the late John Kilsdonk, and the Canadians (BC buds propeller factory) have one available for LH props...not sure about RH props, but that could probably be arranged. You might check Brodak's catalog...seems to me they may have had a batch made.

I think you could make your own "Hooptee" gauge ok. Also, I have not f'got about the mufflers, just can't find the second one, and it'll cost as much to mail one as two, which goes against my grain too much.  Steve

[RknRusty]

Okay, I tried the experiment... sort of. It was finally time to cover my Yak-9 wing. I know, I've been yakking about this build since I joined SH, but it's finally time for the end run on it. I checked for twist on the wing skeleton by laying a straight steel rod across the frame against each #9 rib, squinting and eyeballing the two rods to look for any criss-cross. The outboard wing appeared to have a lower angle of attack than the inboard. I gently but firmly twisted and held it at room temp by hand until it was straight. It looked okay, so I applied Monokote to the bottom panels, but did not shrink it tight. A couple of days later I was ready to 'Kote the top, so checked it again and the twist had returned.

Since I didn't want to moisten the bones immediately before sealing it up, I went with one of the suggestions above; that heat does the work, and steam mainly helps expedite the job by spreading the heat faster. The LE is epoxied and glassed at the center joint. I put a hair dryer on the table and held the wing in front of it while counter-twisting the wing and focusing the air on the LE joint and center sheeting for 5 minutes. I held it in that position until it cooled and re-checked. My rods showed no more criss-cross, lined up perfectly. I left it on the table for about 12 hours and re-checked, still perfect. So I covered the top panels and tightened it with the iron starting at the #1 bays(top and bottom), and tightened each bay top, bottom, inboard and out, all the way down. I never use the gun, just an iron with no sock. It came out great. (I might be a Monokote idiot savant)

Now I don't know for sure if I reconfigured the wood, or just the epoxy, but in any case, thanks to this thread, I now have as straight of a wing as I have ever built.  So for my next two projects, I still have twisted wood, both fuselage stock, and will try the same thing with steam and report my findings.

Thanks for putting ideas in my head from which I can cherry pick the ones that fit my own puzzle(that's how to best use a forum, right). Oh, and bye the way, the closest thing to a jig I used on this wing was a bunch of square blocks, some of them slotted to accept the TE sticks, pins, divider caliper, and a ruler. I guess that really was a jig though, wasn't it. :p

You crazy people will help me become a better builder yet!

Rusty

[john e. holliday]

Well I pulled my new wing off the jig so I could sheet the top leading edge.  While on the jig I checked every thing with my four foot level for straightness.   It was looking great until I pulled the jig rods out.  Trailing edge on one panel has a slight bow.   But, I think I can remove it when I get to the covering stage.  Otherwise the  wing is straight.  But then again I think I will wet  it real good and clamp between the straight sheet metal pieces I have and let dry.   

[RknRusty]

Well I pulled my new wing off the jig so I could sheet the top leading edge.  While on the jig I checked every thing with my four foot level for straightness.   It was looking great until I pulled the jig rods out.  Trailing edge on one panel has a slight bow.   But, I think I can remove it when I get to the covering stage.  Otherwise the  wing is straight.  But then again I think I will wet  it real good and clamp between the straight sheet metal pieces I have and let dry.   

Might want to re-jig it and heat it while it's wet to help get the wood to conform.
I recently got a new rod type wing jig that I've not yet used. For my last wing I just used square blocks and a ruler and pins to elevate it and hold the LE and TE without any rods through the ribs, and it came out only needing an easy minor adjustment. Now that I've read more, I'm not so sure the rod through the rib type is a good idea now. If I do use it, I may consider hot steaming the finished skeleton before removing it from the jig. I don't want to de-bond my wood glue though. I was looking for ideas to make a jig for aligning my wing and fuselage for gluing when I started reading more about wing jigs, and now have reservations about my new one.

Rusty

[john e. holliday]

If you really want to see the proper way of doing jigs, go to Stuka Stunt and do a search on Al Rabe.   Or better yet go to get his DVD set.   Here in the Vendors section see Al's Models.