Bending sides

[Stray Feathers]

I should have done this BEFORE I started . . . I have just bent two sets of sides, one EI Rosewood and one cherry, for OM style guitars. I used a bender given to me by a friend who made it and used it for several guitars, so I thought I was on the right track. It's a piece of large aluminum boat mast, so sort of egg-shaped in cross section, and heated with a 300 watt bulb that pretty much fills the inside. I soaked the sides as instructed by the Kinkead book I am using, and sprayed water on the sides regularly. The pipe is hot enough to make the wet wood sizzle (and my fingers burn), and I could make the bends but they would not hold shape. I got them into the form and they have come out not bad but with a couple of small cracks to deal with. It seemed more difficult than I was expecting. Is this maybe not hot enough? Any other suggestions? And one question: When bending sides, should I expect a bend to hold its shape without putting it in the form, or do you have to hold it in position to get it to stay?

Thanks -

[MaineGeezer]

Others know a lot more about bending than I do, but based on my limited experience:

It sounds as though the tube is hot enough.

The wood ought to hold the bend by itself.

You do have to wait for the wood to cool off before it will hold the bend, however, and if you just bend it enough to get it into the form there will be some amount of springback when you take it out.

You may be rushing it. Take your time and gradually work the bend into the wood until it fully conforms to the curve you want before you put it in the mold.

Some woods bend a lot easier than others, too. I think both rosewood and cherry bend fairly readily, so that probably isn't the issue.

If you've got a piece of scrap, practice with that to get the hang of it. I've seen "practice bending wood" for sale somewhere.

[tippie53]

how thick were the pieces ?
they should be about .075 in thick

[Danl8]

As MaineGeezer writes, I think your setup isn't hot enough. Both woods can be bent dry without water, but steam helps distribute the heat to make the wood cells plastic. I would encourage you to take some scrap wood and practice bending. Try it too hot where you get some scorching, then dry, then with water and push till you feel the wood breaking and then push just up to the limit of breaking, and so on. The only way to get a feel for where you are in the bending process is to have been there doing all those things, scorching, breaking, and bending perfectly. When the wood is ready to bend you will feel it give way; once you know that point bending is just another job. Once the bend is made, I usually hold it off the pipe until it cools. I have pieces I bent 30 years ago that have not moved at all regardless of humidity and time.

[B. Howard]

when bending on a hot pipe temp is important. as already noted your pipe sounds a bit cool. A good reference fro temp is you want the pipe hot enough that a drop of water put onto it will dace on the surface as it boils away. If it does not dance it is too cool and if it bounces off the pipe or evaporates instantly it is too hot.

[MaineGeezer]

As MaineGeezer writes, I think your setup isn't hot enough.

Is, or isn't, hot enough? I initial thought that it's hot enough, but I'm quite ready to be convinced otherwise. I guess I'd ask the question, is it hot enough to scorch the wood? If not, I guess it's open to debate. While it's hot enough to boil water, that may not be sufficient. I think it should be in the neighborhood of 300+ degrees F.

[Stray Feathers]

Thank you all for very helpful replies. John, the sides were thicknesses to .075 - .080. Kinkead specified .078 I think. I am coming to think it is not hot enough. I did not experience any scorching, though I was very conscious of that and spritzing water anywhere the wood got dry. I will try experimenting with dry wood, but I always thought to bend wood you had to "steam" it, so moisture was involved. One last question - I assume I can put sides back on the pipe to work them a little more?

[Danl8]

I typically adjust the bent sides/binding by going back to the pipe, so my answer would be yes, re-working is okay. That goes both ways --unbending and adding more bend. I haven't tried overworking, though I guess that must be possible. Steam and water, for me, are just 'helpers' as I prefer bending dry when the wood cooperates, but sometimes it is really stubborn. Highly figured woods definitely benefit from wetting IMHO and, more importantly, a flexible steel backing. For the start of each session, I like playing with scrap wood to remind myself how easy it is to break it and regain a feel for the wood becoming compliant as I mentioned earlier.