[JSP]

Hello,

I have run into an issue with steam bending the sides for a mandola I am building. I built a steam box for the occasion, but in the test I did, the wood retained only about 60% of its bend at best. Today, after tweaking a few things and keeping the wood (Bolivian Rosewood) a little more damp than the test, I fear the bends will fare little better. Without getting an actual steam bending apparatus intended for luthiers, is there anything I can do to get more bend in the wood? I am mostly limited to simple hand tools in my current apartment, but might be able to accommodate other options.

To bend the wood, I pressed it and clamped it around a form after having steamed it thoroughly, and through the process used the kettle and piping as a steam gun that kept the heat and moisture up. Even still, there is a great deal of tension in the wood. I intend to leave it in the form for a few days in the hopes that it relaxes a bit into its new shape, but I am not hopeful.

Any help would be greatly appreciated!

JSP

Topic

[Jonas Jensen]

#2027233

Insulation

I am by no means an expert in steam bending. I made a steam box pretty much like yours for a settee project last year.

I had to bend some 5/4″ elm into two 90 degrees bends.

The first attempts were not successful, even though I left the wood longer than the 1 hour per inch.

I found out that the temperature of the steam box was too low. So I wrapped my drain pipe (steam box) with 100 mm of insulation mat. That really helped a lot.

So may I suggest that you try to insulate your steam box? An effective and cheap insulation material is bubble wrap which can be found pretty cheap.

As far as I have understood, the wood will not take any harm in being left longer than the 1 hour per inch rule of thumb. It is supposedly intended as a minimum time, and that makes sense if you have to make a living out of building e.g. a boat.

So I would leave the wood in the steam box longer, say maybe half an hour.

Do you have a possibility of testing with some inferior wood before going  on with the rose wood? That way you can perhaps gain some experience in placing the clamps etc.

Good luck

Jonas

 

[JSP]

#2027238

Thanks for the advice Jonas, I think that might be exactly what is wrong. I took the plunge with the first of five pieces, and the results were a little better than the scrap oak I experimented with, but still not great. The wood did not break, which was a relief, but there is a fair amount of set it still needs to take. After taking it out of the box (pipe!) I used the kettle with the smaller pipe still in it as a steam gun to keep the thin wood from cooling and drying off too quickly. That helped too, but still not quite enough. I’ll grab some insulation and give it another try!

Thanks again!

[Author]

Replies