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Spring steel backer for tight Bends in figured maple,
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Author:  SteveSmith [ Wed Feb 11, 2015 11:17 am ]
Post subject:  Spring steel backer for tight Bends in figured maple,
I've been trying to bend (on a pipe) some highly figured maple sides for a mandolin and need something to back it up. Figured it would also be useful for cutaways. I've tried aluminum flashing in the past buy the blued spring steel seems to work the best for me. The spring steel I use for guitar sides is about 0.030" and is just too stiff for tight bends. McMaster Carr has stock from 0.002" up so lot's of options; I could get a 6" wide piece and cut it down to fit. What thickness are you guys using?
Author:  TonyKarol [ Wed Feb 11, 2015 2:34 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
I use 10 thou in my bender .. but on a pipe, and for a really tight bend .. probably .008
Author:  Michael.N. [ Wed Feb 11, 2015 3:08 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
The stuff I have is .0010. Given to me by a Violinmaker. Some of their C bouts bends can be pretty tight. Place paper between the steel and the Maple, otherwise you might get some staining especially when the spring steel starts to oxidise.
Author:  SteveSmith [ Wed Feb 11, 2015 3:40 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
Thanks guys - I guess I'll go with the 0.008". Michael, thanks for the hint about the paper.
Author:  kencierp [ Wed Feb 11, 2015 4:34 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
Have you considered boiling the figured Maple? I've done that for violin sides and its amazing how soft and pliable the wood becomes. Actually I have boiled figured guitar sides as well. Let it completely dry and there will be virtually zero spring back. I believe Yamaha still boils all their sides prior to bending -- just a thought.
Author:  SteveSmith [ Wed Feb 11, 2015 4:37 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
kencierp wrote:
Have you considered boiling the figured Maple? I've done that for violin sides and its amazing how soft and pliable the wood becomes. Actually I have boiled figured guitar sides as well. Let it completely dry and there virtually zero spring back -- just a thought.


I had not even considered that. I thought that the figured maple would fall apart. Well, I ordered some extra to test so I'll try it out. How long do you boil them or do you just check them for pliability as you go?
Author:  kencierp [ Wed Feb 11, 2015 5:21 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
Boiling is a slight over statement -- I guess steeping hot, steam rising off the water. I'd say about 45 minutes maybe a little longer. I am revealing my age now, this is actually my original side banding method found in the Sloane guitar making publications. Back than it was all we had -- and I am glad --- his writings proved to be invaluable.
Author:  Cush [ Wed Feb 11, 2015 6:52 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
When I bend figured maple I don't soak the wood. I just spray it till wet and go right to the iron. After the moisture is driven off I rewet and bend again. I repeat this till I get the bend I want. There is a limit to how tight the bend can get without fracturing. The limit is set by how thick the ribs are. For a Mando scroll or in your case the neckblock area the wood may need to be as thin as .06 or less. The rest of the ribs where there is less curvature it can be left a little thicker like about .085. When bending I use a steel backer of .012".
Author:  SteveSmith [ Wed Feb 11, 2015 9:09 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
According to Siminoff's site he uses steam and bends them at 0.110" so there's another idea. Since I am used to using the hot pipe I will probably focus on that but I will try the hot water on a test piece first just because I would like to see how it does.
Author:  Michael.N. [ Thu Feb 12, 2015 2:52 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
You could also try my method of wrapping the side in foil. That helps to retain both the heat and the moisture. You will need to 'lock' the bend after removing it from the iron, otherwise you will lose some of the bend. Watch fingers, the foil conducts heat extremely well!
Author:  bluescreek [ Thu Feb 12, 2015 6:49 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
you can use stainless steel as it won't stain . Maple can be funny to bend too much water and it wants to over bend. It is all in the heat and feel. There are times it can be steamed. There was a violin maker in my town that was trained in cremona , his bending set up was rather simple just a chimney and an alcohol burner.
once bent the mold and spreader will refine the shape. If you are free building , take your time. Like Cush if I hand bend it is just a light spray and bend. I do try and keep the wood moving , you want to wary of over heat and scorch.
Author:  SteveSmith [ Thu Feb 12, 2015 7:46 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
I appreciate the replies from everyone. I have a fox type bender for my guitars but usually use the hot pipe because I enjoy the feel of working the wood. I thought I was getting pretty good at it till I got this highly figured maple. Like several of you I usually use a light spray and bend but based on my tests the other day that means thinning the sides down to 60 or 70 thou for the tight bend at the neck which is a 1 1/2" to 2" radius. I enjoy learning new methods so I will at least try steeping in the steamy hot water bath and may even cobble up something to try steam bending some too.
Author:  Barry Daniels [ Thu Feb 12, 2015 8:42 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
60 or 70 thou is about right in my book. Be careful of using too much water because curly maple may start to facet or develop ripples when bent.
Author:  SteveSmith [ Thu Feb 12, 2015 9:52 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
Barry Daniels wrote:
60 or 70 thou is about right in my book. Be careful of using too much water because curly maple may start to facet or develop ripples when bent.


Thanks Barry, it's nice to get confirmation.
Author:  Barry Daniels [ Thu Feb 12, 2015 10:34 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
A good point of reference is violins, which have very thin ribs that allow them to be bent almost immediately when placed on the hot pipe.
Author:  SteveSmith [ Thu Feb 12, 2015 11:07 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
That's interesting, I had not thought to check what the violin makers do but it does make sense.
Author:  dberkowitz [ Sun Feb 15, 2015 8:25 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
One trick is to put a piece of steel across an area wider than your bend and clamp the ends of the steel with a couple of small clamps so that it's held in place on the outside of the bend. It keeps the steel and wood in tension.
Author:  SteveSmith [ Sun Feb 15, 2015 12:54 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
I like that idea. I'll give it a try.
Author:  Mike Collins [ Sun Feb 15, 2015 1:59 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
I use a veneer on both sides of the side.
Just a thin veneer-not a dark resinous wood.
Wet the veneers only and make a sandwich ;
with side in between them.
You may burn the veneer on the inside but not
the piece you need bent.

Mike
Author:  SteveSmith [ Mon Feb 16, 2015 6:27 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
That would allow me to turn up the heat without scorching the side. A good thing, thanks for that one Mike!
Author:  Barry Daniels [ Mon Feb 16, 2015 11:01 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
dberkowitz wrote:
One trick is to put a piece of steel across an area wider than your bend and clamp the ends of the steel with a couple of small clamps so that it's held in place on the outside of the bend. It keeps the steel and wood in tension.


David, I am not intending to be argumentative but am trying to figure out how that works. Being an engineer I have to first comment that this arrangement would actually result in the wood being in compression and only the steel in tension. Does this compressive force help to protect the wood from fracture or is there some other benefit?
Author:  kencierp [ Mon Feb 16, 2015 11:22 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
I am sure David will respond -- but what I've found and apply in our bending operation is that it is important to keep the entire width of the blank in firm contact evenly across the heat source. If not, the material dries out at different rates and wet - dry areas develop, which can cause ripples visible and not -- the ripples not only lead to resistance but will eventually crack. So no matter which wood type we keep it pinched with high tension. Also we always have the heat source on the compression side (inside) of the curve. I really like the Taylor factory tour showing their bending process -- KMG copied that without the pneumatics.
Author:  SteveSmith [ Wed Feb 18, 2015 8:02 pm ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
Thanks everyone for sharing your methods. I've got some results using roasted curly maple 1 3/8" wide x 0.060" thick.

I tried 1) 0.008" blue steel backer clamped and, (2) steel backer unclamped. Both methods with different heats, with wood dry, lightly sprayed, and dry with wet cloth on iron. Then (3) I steamed an 8" piece for 20 minutes and tried to bend it. I did my testing with 2 different sets of sides. Although each method yielded slightly different results, the final result was always the same- a sudden break along the curl before getting the bends complete. The roasted wood just didn't seem to relax.

So I made a set of sides the same dimensions from regular (un-roasted) curly maple. Bent both sides in about 20 min. No problem. The photo shows cut offs from both side sets.

My conclusion is that the roasting process changes the structure of the wood (not surprising) making it brittle or somehow unable to take a tight-radius bend.

Image
Author:  kencierp [ Thu Feb 19, 2015 9:23 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
I missed the part about this being roasted material -- different ball game. But did you put it in boiling water for an hour like I had suggested?
Author:  SteveSmith [ Thu Feb 19, 2015 11:18 am ]
Post subject:  Re: Spring steel backer for tight Bends in figured maple,
Ken, that's the only one I didn't do, I'm not allowed to mix wood and the kitchen stove anymore (unless she's out of town). Closest I got was steam (the wood was saturated and up to temperature though) and thought that would give similar results. Maybe I'll try a shorter piece that will fit in a pot. If I understood you correctly you are boiling then taking the wood to the iron?
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