I am restoring an old, vintage Rainbow House. Everythiong is going great so far.....(Knock on....uh....wood).....except for one problem. The roof of the larger, outer house is made of 1/4" plywood. Each side of the roof is seperate, and hinges to the house. One of the roof sections is warped pretty bad. Actully both are warped, but one is slight enough not to affect performance. However, the worst section is pretty bad, and I need to do something with it.

I have weighted it down for long periods, clamped it flat for long periods, and even clamped it numerous times overnight with opposite pressure to the bow. (I hope that makes sense). I am not having any success at all. I even tried wetting it slightly, but still, no luck.

Does anyone have any advice or suggestions for a remedy? This prop is probably 20-25 years old, and I would really like to keep all the original pieces if I can.

Thanks for your help!

Regan

Have you tried a steam box? Not too hard to build one, you can find all sorts of plans on the net. I don't know where you are located , but if the community is large enough, there is probably a wood working club and you can bet somebody in that group will have a steam box.

No, I have not tried that. I wondered about steam, or lot's of water, but I also wondered if it might make it worse. I will try and do a search and see if I can find out some info on it, and maybe I can learn how to control how the wood reacts.

As far as a wood club in my community goes, there isn't one. I am from a very small place. I may check some of the larger cities near me.

Thanks!

Regan

How hard would it be to just replace it? Or maybe brace it?? I doubt you get it to flatten out and hold without reinforcement.

-=tabman

I'm with Tabman. If this had been a piece from early 1900's and the materials were hard to come by, then maybe try to remedy the problem. But since you are restoring this, maybe to be used, just get some new 1/4 inch stock and avoid all the frustration and hassles.

FWIW

Well, I guess it would be easy enough, but I'd like to keep the original pieces if I could. As long as the thickness is the same, the only other problem I might have in replacing the pieces is the angle of the cuts. I don't really have the proper tools to do it, but I suppose I could find somewhere that could do it for me.

I read a lot about the steam box, and it sounds as if it might work. I'm not sure I am willing to go to all the trouble of building one though. I stumbled on some information that mentioned that boiling wood wood have the same effect as the steam. Since the pieces are small, I figured I may try it. Either in a large pot on the stove, or I thought I might put it over a pan of water in the oven. Seems like that would be essentially the same as a steam box. I may experiment, because I really don't have too much to lose.

Regan

Be careful boiling the wood. Plywood is glued together, you could boil it apart. Boiling over soaks the wood as well and it may not dry evenly, could result in the exterior venieer buckling or warping.

Thanks. I am trying to figure out how to set up up in the oven first. I also thought about using a large slow cooker. If I had a metal rack to set the wood on, so that it would stay over top of the water, I;m thinking it might work.

Find an old teapot from a yard sale or a resale shop for making the steam. This sits on the ground on a fire source, like a small hibachi or a camp stove. The steaming box is above this, maybe resting on a pair of saw horses. A smallish automobile radiator hose connects the two with hose clamps.

A box made of 5/8" ply and lined with tin works great. Five of the sides should be screwed down tight as can be, and the 6th side is your door. Realative shape and size will depend on your project. I've seen them 12" square and 10' long -- it all depends.

The steam box should have an interior space roughly 3 to 4 times the volume of what ever you are steaming. The bottom of the interior should have small raised parts so that objects are not resting on the bottom, so that steam can go everywhere at once. The box should NOT be air tight!!! Always allow for a small (1/8 to 1/4") relief hole on each end of the box. Never mind this if the door is not air tight (although you should try for this.)

The goal is to completely saturate the parts with intense steam for several minutes. Again, all these values must be adapted to each project individually. Twenty minutes might be half too little one day, and 15 minutes twice too long the next.

But the next step is even more important, and that is to get your project clamped up the second it comes out of the box! You can not be too fast!!! Wear leather gloves or some other type of protection, and get your wood into the clamps immediately. Let stand for 24hrs.

Good luck!

Sounds like it would just be easier to replace the warped part but if you do this you might want to consider adding some opposite camber to the clamped part.

-=tabman

Hey Tabby, I didn't say this is the way I would go, just trying to offer some sound advice on the subject of steaming. If it were me, I'd probably just replace the wood and be done with it. Only a true antique from before 1950 and owned by somebody famous would really be worth all that trouble, IMHO.

Thanks Chance. I had researched and found out a lot of great info about steaming wood, but I had not read anywhere how long to leave the piece clamped. You answered that for me! Thanks!

Plywood is a **** to straighten!

I have successfully straightened moderately bent plywood sheets (admittedly, only the thinner 5 ply stuff) with wet towels, and an electric clothes iron.

I clamped it 'past' flat (it'll want to spring back after its straightened so you have to almost reverse bend it a tiny amount), and just laid my wet towels over the concave side, then I'd keep heating and wetting.

In retrospect wouldn't clamp it until after I'd heated it for a while (I managed to crack the surface veneer a little).

It took a fair time and a lot of water.

Once it is flat, keep heating and wetting for a little while more I'd take it a little 'past' the flat point - mine wanted to spring back somewhat.

BUT as Father Photius said, it's made of layers and could come apart. Depending on the glue, heat and water could easily de-laminate the whole thing.

Any wood I have ever straightened, I have immediately attached it to my frame - but it sounds like your piece is not attached? In this case you might have trouble with it even after it's straight, it will might want to return to its bent state - I guess you'll just have to try it!

I'm sure we'd all like to hear how it turns out!!

Cheers,
Monkey

Just because I offer advice contrary to someone elses doesn't mean that I am necessarily criticising anyone's ideas or opionions, and Chance, I tend to agree with what you say a lot. Anyone who has been to southeast Asia for any time learns there's more than one way to catch a monkey. I am just having some fun participating in a conversation about something I have some knowledge about. Regan is going to do what he wants to do anyway. I can just hope he keeps us posted and lets us know how it turns out.

All the advice given in this thread has all been good as far as I know. It just depends on how he wants to solve his somewhat interesting problem. I wonder if we can get a picture of the warped part FOI.

-=tabman

Tabby, I didn't take offense at all to your comments! Did I sound defensive? It sure wasn't meant to be! My comment was offered in the calmest & most respectful tone possible.

Regan, I missed the part about it being a pice of plywood. Steaming ply is a very bad idea. I doubt very much the effort will be worth the result, and ply probably will just pop apart under intense steam, especially the edges. Steam done right WILL be intense, and is not friendly towards plywood.

No you didn't but I wanted to make sure you didn't think I was being critical of your suggestions, that's all. I'm just glad to be here.

-=tabman

From my understanding, if you've got a sheet of warped 4x8 ply, proper storage can help straighten it out. As for your problem- a new piece of wood may be the best route, especially if you're planning on repainting the entire prop.

Steam boxes can be handy for other projects, if you go that route- so know that you'll be able to reuse the box. For example, steam is useful for bending laminates, if you need to make a curved piece for a prop. (You'll also need a form to clamp the piece into, of course.)

-Erik

Thanks for all the suggestions everyone! I'm still not certain what I am going to do. I have been reading up on the steam boxes, and some say isteaming works with plywood. Like I said, I really don't have much to lose either way, so if I can figure out an easy way to steam it I may try it.

Erik, its not a 4' x 8' sheet of plywood, it is 2 very small pieces of 1/4" plywood. I don't know the exact size, but they are around 11" x 5".

Tabby, I will try and get some pictures up if I can when I get some time.

Thanks again everyone!

Regan

Well, I came up with make-shift steam setup. Since many of you seemed interested in ths, I thought I would post some of the details.

I borrowed a large pot from my mother, and it was just large enough for my wood to fit into. I made a metal rack to suspend the wood above the water. I first tried the oven, but it would not produce enough steam. I started smelling the wood, so I stopped. The wood actually discolored a little from the heat.

I knew I had to use a stove, but the pot was too large for a conventional electric stove. I solved this by placing it across 2 electric stove elements. The rule of thumb for steaming is 1 hour-per-inch of wood thickness. This was 1/4" plywood, so I figured 15 minutes would be the correct time. I actually went 20 minutes for good measure.

The pieces are clamped now, and I am going to leave them for 24 hours. That's only a couple of hours away. I don't know if this is going to work or not, but from all I read about steaming, I think it should. There are sceptics about bending plywood, but my research said it can be done. Since this is thin, maybe there is a better chance that it will work for me.

I tried to post some "before" pictures here so you could see the amount of warpage. I cannot get them to post, even though though are under the size limit, and in JPEG. I have had problems posting pictures before. I wish I knew why it will work sometimes and not others.

Anyway, I uploaded a few pics to photobucket if you'd like to see them. I put a ruler beside the plywood for a gauge to how much the piece was warped. I'm not sure if you can see it in the picture or not, but it is warped about 5/16"-3/8". The other piece was not as bad, and I did not photograph it. However, it was bowed in the opposite direction as this piece, and it only compunded the problem of the roof not meeting at the top. I went ahead and steamed both pieces.

http://i238.photobucket.com/albums/ff127......2009.jpg

http://i238.photobucket.com/albums/ff127......anel.jpg

http://i238.photobucket.com/albums/ff127......amer.jpg

http://i238.photobucket.com/albums/ff127......ming.jpg

Keep your fingers crossed for me. I am getting ready to unclamp the pieces very soon.

Regan

Man-o-man I love how resourceful we can get sometimes! A turkey pot! That's funny! LOL Well done Regan! Let us know how it turns out.