Official Luthiers Forum!

Hi all. I'm working on the sides for my current build, and the bending is
resulting in sides that are a bit lumpy. OK, first, the data:

Side wood - cocobolo
thickness - 0.080"
bending pipe - 5" aluminum pipe heated with propane torch

Getting the wood to bend is easy with a litle wetting, but it works best
while holding the side in one spot on the pipe. Sliding the side back and
forth to widen the bend doesn't seem to be heating it up enough to bend.

So, any suggestions for 1) correcting the lumpy bits and 2) preventing
them while bending? Thanks!!

For what it is worth, I had lumpy sides on my first pipe bend, too, and I was using mahogany. Those lumps, and the accompanying valleys, sanded out very easily though.

Someone with much more content knowledge will be along any minute.

_________________
Eagles may soar, but weasels don't get sucked into jet engines.

Those lumps quickly had me building molds and buying heating blankets.   

Sand away all you can, leave all you "need". Oh, and good luck with the building.

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http://www.dickeyguitars.com

The pipe I use is tear drop in shape creating a great contact area between the wood and pipe. This helps to spread the heat in the bend area and allows for a more even bend. I only wet the wood on the side contacting the pipe. I wet the whole side and let is sit 10 minutes before beginning the bend. I will wet the side as it dries during the bending until I’m satisfied with the bend.

Usually the bumps are created from uneven heat distribution or being too quick in the bending. Slow and easy wins the race.

I would also suggest practicing on some other wood to get the feel for the bending process before using your good sides.

Good luck.

_________________
Michael Lloyd

“I was born to ignorance, yes, and lesser poverties ...
I was born to privilege that I did not see ... I didn’t know it, but my way was paved” – John Gorka

I'm not sure I can offer much help in fixing you lumpy sdes, but there are some things you might want to try that could help you in the future.

I do all my bending on a pipe. I've been tempted to build a machine, but I don't have the space and I've managed to become pretty fast on the pipe (15-20 min per side). I found Coco really difficult to bend when I first tried it. The stuff I had was so dense and oily (like most Coco) that it would not absorb any water. As it ended up I broke a few sets. A builder friend suggested that I get the iron good and hot. Then he said to lay a damp cloth on the iron and bend on top of the cloth. This method forces moisture into the wood and usually makes it bend easily. I now use the rag method for any type of wood that I am bending. It is try that the wood will often bend easily if you keep it in one spot, but the result is that you get lumps. You have to keep it moving, and if you iron is hot enough it should work. I use one of the teardrop bending irons.

My only suggestions with your sides is that you try and flatten the bumps a bit and rebend.

Hope that helps.

_________________
Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Michael Lloyd is right !

mike collins

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Mike Collins

Keep it wet and back the torch off. I used a galvanized pipe with a cap. I know the fumes from the galvanized pipes are bad for you but it might work better than the aluminum.