Help with steam bending cherry

[Larry Crim]

Ok its time to make my apron for my table but wanted to get a sanity check on how I intend to do it. My plan is to make my aprons with a 45" radius two halves since the table is oval they will be about 3.25" tall and the finished thickness will be about 3/4".
I have made the form already and my plan is to cut 3 thin strips about 1/4" thick and steam bend them to the form one at a time then after the appropriate drying/cooling time place them back in the form and laminate them together with glue to achieve the required thickness. My thought is this would make them more stable and I really did not want to try bending a 3/4 " plank for the my first steam bending project.
I had previously bought some premade aprons but they were pretty bad when I recieved them and I did not want to use them so I returned them and thought I would give it a try on my own.
I also need a recomendation on what type of glue to use to prevent any creeping.
Thanks
Larry

[Lee Schierer]

Your plan sounds good to me. I have steam bent a couple of pieces of cherry and ran into the same problem. I had to make the piece out of thinner strips to get it to bend. You'll find that you need to steam the wood quite a while and you will have less than a minute to get it formed and clamped before it stiffens up. Make your steam bending form a smaller radius than you final shape as the parts will spring back. You may have to experiment some to determine how much spring back you get.

Make your steamer from wood or metal as PVC will soften when heated to the temperatures needed for steaming. Wear gloves and make sure your steam boiler is built safely.

[Roger Fitzsimonds]

I have not steam bent anything yet, but Wood magazine has a good article about bending and building a steamer. You might want to check it out.

Roger

[Mike Henderson]

I'd laminate bend the pieces and not try to steam bend them. Just make a form in the shape you want and cut laminae about 1/8 inch thick. You might have to make your form with a bit more of a bend to account for springback.

Good luck.

Mike

[Bill Arnold]

I agree with Mike about resawing your strips to 1/8" thick. Since I have a vacuum-pressing system, I've built aprons using a form similar to yours and placed the laminations in the vacuum bag to hold them to the form. You should be able to set up a series of clamps to accomplish the same thing. In my case, I was able to do the apron in four segments and place a design detail at each of the joints.

Another thing to consider is the adhesive. I use plastic resin glue (DAP) for most laminations. It dries very hard and has no creep like yellow or white glues. It takes a little longer for it to set up, but it's worth the wait to have a stable assembly.

Another thing to consider is to use bending ply for the core of the apron. Four layers of bending ply with a layer of cherry on each side will be easier to bend. A bead detail for the bottom edge will hide the layers.

[Larry Crim]

Thanks for the all the input so far.
I think I have all I need for the steam chamber I did a lot of research on it I am going with the pvc pipe and a steam kettle with the wood blocks to support inside and release holes on the end caps.
As for cutting thinner strips and laminating them without steam I considered that but I should have included in the original post I have a router bit I intend to contour the apron with and it makes a cut deeper than 1/8 " so it would cut deeper than the laminate and into the second. that is why I decided to go with the 1/4 ".
Larry

[Larry Crim]

Bill would the plastic resin glue (DAP) be the same as gorilla glue? The gorilla glue is listed as pure polyurethand glue.

[Bruce Haugen]

Larry,
Mike is right. Laminate. In the long run, heck in the short run, laminating is just going to be easier, with more predictable results. A very experienced friend of mine once told me that a magic number of laminates seems to be six. If you use six or more laminates you will have a minimal, if any, amount of springback. Any less than six will increase the springback. I've found that advice to be true. So to end up with six laminates in a 3/4" final piece, use 1/8" laminates like Mike suggests.

Just be sure to have a lot of appropriate clamps, a good clamping form and cauls. A dry run or two is imperative.

I've used this procedure lots of times and have had very good results. Another benefit is that laminating allows you to put your best wood on the face and use less than great wood in the middle where no one will ever see it.

Bruce

[Cliff Rohrabacher]

I bend the side bouts of guitars (1/8" thick) by soaking them in water for a couple hours and running them by hand over a short length 4" dia steel pipe with a propane torch runing inside it for heat.

The bending is fast and stays put. If the wood drys you just wet it again.

I don't know if this'll work for 1/4" thick cherry but It's a lot faster to set up and use than a steam box.

[Bob Johnson2]

I've never had luck with anything thicker then 1/8, and I've tried. Do a test first, it'd be a bummer to have them crack on you.
I found my home made steamer worked about the same as soaking them overnight in the tub... I've also had them always bounce out a bit by the time they've dried/cooled and were removed from the form. It's also worth considering doing them all at once, the bend will differ as you go out from the form, number them, then bend and dry all together, glue them together in the right order and put them back on the waxed form till hard. Good luck.

[Bill Arnold]

Bill would the plastic resin glue (DAP) be the same as gorilla glue? The gorilla glue is listed as pure polyurethand glue.
Larry,

They are two different products. Here's the DAP product.

By the way, it works best to measure the powder and water by WEIGHT, not volume.

[Larry Crim]

Thanks for all the info, I guess if I laminate only with 1/8" strips then I will not be able to coutour apron. What about steaming only the outer strip at 1/4" and doing the rest in 1/8" strips this would give me the thickness I need to use the router bit on the outside face without going through the laminate.
Bill Thanks for the glue recomendation.
Larry

[Mike Henderson]

When you cut your laminae, mark them so that you can put them back together the same way they were in the original wood. I do it by marking a "V" on the edge of the board before I cut my laminae. This will give you a reasonable grain match in the glued up product. It won't be perfect but it'll be close. Next, choose a glue that comes close to matching the color of the wood. The DAP plastic resin may be a good choice because cherry will age fairly dark. The glue may look dark against the wood initially but over time it will probably blend well. Plastic resin (urea formaldehyde) is a good glue for laminate bending - no creep and it gives you a fairly long open time. Slow setting so leave in clamps for 12+ hours.

Springback is related to the square of the number of laminae and the amount of deformation in the bending. That is, springback goes down a lot every time you add an additional laminate to the package. Someone commented that six is a good number and I'd have to agree. You might make your form with a bit more of a curve than you want your final product. You'll only know for sure when you take it out of clamps.

I don't exactly understand what you're going to do for a profile, but you could also try cutting your outside laminate a bit thicker and keep your fingers crossed. If you're seriously worried about it cracking, you can put filament tape on the outside of that piece. The filament tape tends to make the bend occur by compression of the inside of the piece instead of cracking of the outside of the piece. It's not perfect but it helps. You can also "pre-stress" the thicker piece by half bending it for some time. Put it on the form and half bend it - then leave it overnight or longer. Sometimes this allows the stresses in the wood to dissipate somewhat and it bends the rest of the way a bit easier. Again, not guaranteed but it seemed to help a couple of times I tried it.

Good luck.

Mike

[Larry Crim]

Well some really good info here. I guess I got some experimenting to do with laminating and how much thickness I can get away with, I will update this thread with what the outcome is. Thanks again for all the advice that is what makes this forum so great the assistance from the members and such a large pool of experience to tap into.
Larry

[josh bjork]

A 45" radius? i think you'll just get away with it.