Bending Black Walnut

[C Herb Hickman]

I'm gathering materials, making tooling, and starting out on building of two F-style mandolins, which I've never done. I've done pretty extensive repair work -- neck re-sets and the like, but haven't tried building an instrument since the 1950s. Now I'm semi-retired.

I have fancy curly maple for one mandolin back and thin maple for ribs (sides), spruce for two tops at least, ebony for fingerboards and headstock overlays, and bridges. I have roughed out two maple necks and two mahogany, have tailpieces ordered and Grovers one gold and one nickel sets. I have some 3/4" thick black walnut that has been on hand for many years, and that has always been one of my favorite woods. So I'm moving toward one maple b&s, maple neck, englemann top and one black walnut b&s, mahogany neck.

Having never bent anything, I'm very wary when I read that black walnut is difficult to bend. How difficult? Are there any special precautions that will make success more likely? The walnut I have is pretty straight grain, board sawn. I have some round pipe-like things I could torch heat, and a pressure-cooker steam generator of rather low capacity (which I could increase). I wouldn't really welcome a side track to build a steam chamber like I've seen illustrated somewhere, made from pipe, as there's so much work ahead already.

Thanks
Herb

[David Newton]

Hi Herb, welcome back to building.

A steam chamber is a waste, you won't be able to get the wood to a good temperature for a long enough time. You could make it work, but it just isn't a very efficient use of your time and energy.

Either do a bending iron, a pipe with heating element inside (made from a electric charcoal starter) or a heating blanket.

Black Walnut is a joy to bend, find the right heat, which isn't that high compared to other woods, and it bends easily, and smells great too. You couldn't pick a better wood to build with for getting back into it.

[C Herb Hickman]

Thanks, David. What diameter "pipe" do you suppose would work or be best? I don't seen any really tight curves in the F-style except in that scroll which is formed by a solid block in the tightest portion.

I'm sure there are going to be a lot more questions, before this is over.

[Mike Langford]

Hello Herb,

Here's my hot pipe for bending sides....(pipe is inch and a half dia. galvanized from Lowes')
I'm forming the scroll for a F-style mandolin (my first!)

[C Herb Hickman]

Thanks. I guess it's possible that someone with such a neat and tidy workbench COULD be doing things right! Can you bend down to a radius almost as small as your pipe? I've been saving a shiny steel tube that came from a treadmill I wore out last year. I'll dig it out and check how big it actually is. There's a limit to how much you want to heat galvanized iron, but I imagine the temperature needed for bending is far lower than the temperature where the zinc will start vaporizing off into your breathing air. I don't recognize that flange that the U-bolts anchor into -- is that special hardware? I guess a simple angle iron could also possibly work, no?

[C Herb Hickman]

It's HUMOR, Mike. Most all of us acoustickers joke about the messy state of our shops. Your picture spread is in my opinion an excellent contribution to this new forum. Thanks again.
Herb

[Bob Gaddis]

The pipe has to be heavy enough to hold heat evenly and not flex when you apply pressure. I'm thinking your chrome-plated treadmill pipe might be too thin. You could find a piece of scrap stainless steel pipe if the galvanized is a concern. I have apiece of heavy, thick-walled aluminum pipe that I use.

When working with open-grained woods, you may want to use a strap to help keep the fibers compressed when they bend.

[C Herb Hickman]

Yes, I can't tell how thin the wall is in the treadmill roller, but it's hardened and I don't relish the idea of trying to hacksaw it. I'm not worried about the heat on the galvanized, though a person who just left the torch on it in a closed workshop could conceivably get zinc fume in his breathing air. I like the polish on the treadmill roller, though. I'll check the metals dealer where I buy aluminum to see what kind of tubing they have lying around there. Still got a few days of work before I'll be at the bending stage. I understand now that bending the black walnut is not to be feared necessarily.

Somewhere I read that a black walnut mandolin was not as "powerful" acoustically as one made of maple. Guess I'll find out.
Thanks
Herb

[Donald A. Fortune]

Greetings Mike, Not to get away from Herbs origonal post, but I thought this might be a good spot to ask this question......
can you give me a good idea as to how small a radious that the walnut will bend?? and also what do you put the material in before you bend it????

Donald

[Mike Langford]

Hey Donald,

The wood in the pics is maple (haven't tried walnut yet) and I can (slowly) get the bend pretty much as tight as the dia of the pipe (see pic #4)....with a bit of spring back, plus you'll have to have a form to keep it in till dry.

I soak the strips in distilled water (the minerals in tap water will spot or stain the maple) for about 10-15 min before I start to bend. The black tray you see in the pics is just an inexpensive wallpaper tray from one of the borgs.

The longest piece still hangs over the edge!........;0)

[Donald A. Fortune]

Thanx Mike -- good info -- I have one other question for ya--
Is the water in the tray hot or cold or somewhere in between??

Donald

[Mike Langford]

Water is room temperature......straight from da jug!

[Donald A. Fortune]

UMMM -- Is da jug brown or one of does new fandangled plastic ones ????? :D