Problems with Bending Sides

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Problems with Bending Sides

Postby mjthorn152 » Sun Oct 08, 2017 1:23 pm

I would like to pick yall's collective brains about how you bend the sides for your dulcimers. This is an area I have had some issues with, but I can't seem to find much solid information on out there. Before my questions, I would like to share what I have tried so far. I have been using air-dried black walnut sides 1/8" thick and 1 3/4" wide, I have been leaving them in the steam box for around 40 minutes. I started out with a steam box made from some 4" schedule 40 PVC, which didn't seem to get the wood hot enough, as well as started sagging due to the heat of the steam. I used several pieces of plywood stacked together and cut along my desired outline as a form, but I got a lot of spring back when taking the wood out of the form. After that I made a new plywood steam box to try to get the wood to a higher temp. It is based off of the one in this diagram, but a little simpler. I also made a new form to go along with it The new steamer seemed to make the wood much more pliable, but the form was a failure. The sides ended up with a twist in the curves that I was not happy with, although they seemed to retain the shape of the form a lot better. I went back to the original plywood form to attempt to avoid the twisting, which seemed to work well, and now that I was using the plywood steam box seemed to hold the shape a lot better. The problem that I am having is that although the sides keep their shape immediately after coming out of the steam box, overnight they still lose a lot of their curve I understand that the sides won't hold the shape perfectly, but this seems excessive. Originally I let the sides stay in the form for several days, but by the time I was using the plywood steam box and plywood form I only let them stay in for about three hours as I read that was all that was necessary. Neither amount of time seemed to make a difference in how much shape was lost after removing the sides from the form.

Ok, so now my questions:
Is steam bending the preferred method for bending sides or am I going about this all wrong?
What type of form would you recommend I use for bending?
How long should I leave it in the form?
I have not used a thermometer in the steam box, is this something I should do?
Are there any glaring errors with what I have done?
As an unrelated question, where do yall source your air-dried wood?

Thank you for putting up with this long post, I really appreciate the advice of all the experts on this site.
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Re: Problems with Bending Sides

Postby KenH » Sun Oct 08, 2017 3:20 pm

Stem bending works, builders have used it a lot. You may not be getting the wood hot enough long enough...
Temperature is important -- a thermometer inside, readable from outside is a good idea.

Personally I use a hot/warm water soak rather than steam. How long I soak depends on the wood. Walnut I would soak overnight.
I use a bending form which mirrors the complete shape of the dulcimer -- holds both sides at the same. I use a "peg form" similar to yours. The top of the pegs do not extend all the way to the top or above the top edges of the sides. They stop about 1/8" low.

After the wood dries on the form for at least a day or two, I glue the end block and tuning head) in place, and glue the bottom to the blocks and sides -- while everything is still in the form. Once the glue has dried, then I remove the dulcimer carcass from the form.
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Re: Problems with Bending Sides

Postby Frimp » Sun Oct 08, 2017 8:33 pm

Ken has a good method.
If you leave everything on the form then glue the bottom (or top) to them, this will help hold the sides to shape.
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Re: Problems with Bending Sides

Postby Bob Gerard » Sun Oct 08, 2017 11:03 pm

My method is much cruder- I just boil/steam my wood in a pan of water on the stove.
I often bend the sides beyond what the curves should be, to anticipate the spring-back.
Also, a trick I learned is to blow the wood with a hot hair-dryer while it is in the form. It has almost no spring back. (My form uses a series of dowels allowing air contact with the slats) which the solid forms wont allow.
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Re: Problems with Bending Sides

Postby Jon » Sun Oct 15, 2017 3:19 pm

I soak my sides in water overnight and then use an electric bending iron to bend the sides to the desired shape. I apply a wet rag as needed to keep the sides wet. I used to use a cast iron pipe heated with a torch as my bending iron-it worked just as well. After the sides are bent to the desired shape, I place them in a form to dry overnight. I use the same method for ukulele and guitar sides. My dulcimer form consists of small blocks of wood with nail holes (so the shape can be changed) and clamps (see attached)..
Bending Jig.jpg
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