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PostPosted: Tue Mar 07, 2023 5:14 am 
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Found this again after some time since I had read it and thought it may be useful to someone if they haven't read it.
NOTE he's using 2 silicone blankets, one above one below the wood.

Bending Sides
by John Mayes

Ok so I get lots of questions e-mailed to me about bending sides and while I am always happy to answer the questions to save some repition here are my methods to bending sides that I learned/worked out in Maine working under Dana Bourgeois. Dana did all the hard part I just fine-tuned the temps and side thickness to the size I thought worked best. Ok so here it is.

For side thickness it will vary from model to model and for each species of wood as well. But as a general rule here are the thicknesses you should thin the sides to.

Dreadnaught .085-.090
Slope D .085-.090
OM .080-.085
SJ .080-.085
anything with a cutaway (unless it is a sharp cutaway) .075-.080

The best bending method I have used so far is to use TWO silicone heating blankets available from LMI/Watlow and other places too. Two blankets ensure that you get quick even heating across the whole piece of wood. One on top and one on bottom with the wood sandwiched between two pieces of spring steel .010 that is essential when bending to avoid cracks and reduce springback.

There are a couple different things to keep in mind while actually bending the wood. 1st is the point in which you can start the bend. There are a few ways to do this but I approach it this way. The boiling point of water is 212f so at about 225-240 you will start to see steam coming from the blankets. When you see steam you want to bend. Since the water is steaming the steam loosens the fibers in the wood and therefore makes it possible to bend the wood. As a steadfast rule you can start bending at 240f if you see steam or not. If you do not see steam it may be because you did not put extra water on it, and that is ok as long as you put enough on. Enough would be a thin coating over the whole side but not dripping off. You can know what temp you are bending at by buying as digital thermometer from wal-mart. The kind used for cooking. They have the long stem that would normally be put into a turkey or something like that. They read temps up past the highest we would use.

So at 240f you have started your bend. You move somewhat slowly..not so slow that by the time your almost done there is no water left in the fibers as that can run the risk of scorching, but slow enough so that you don't break the wood. On highly figured woods such as quilted mahogany use extra care as they can be very tough to bend. The process I use for bending is to bend the wasit first and then the lower bout and then the upper bout. Not the only way but the way that suits me best.

I regulate my temperatures via a potentiometer or a dimmer switch. I then can bring the temperature up the mark that I want and then keep it there for as long as I want with less plugging in and unplugging of the cords, but either way works.

So the waist press is down, and the sides are also curved. You will want to bring it up to a temperature and hold it there for around 5-7 minutes to really 'set in' the bend. Each wood has a different temperature to go to and some woods are less prone to scorch than other so here is a list of woods commonly used and what temperature to bring them up to:

Indian Rosewood: 300f
Mahogany: 310f
Maple (bigleaf): 290f
maple (European): 280f
Brazilian Rosewood: 305f
Cocobolo: 310f
Koa: 300f
Paduk: 310f
Walnut: 300f
Other Rosewoods: 300f

You will want to keep the wood at that temperature for about 5-7 minutes. Then unplug the wood or turn off your dimmer switch and wait for 30-45 minutes before taking the wood out.

With these methods I have bent hundreds of sides and using them should help you to feel confident in your bending and not afraid that you are going break a side.

Again these are just my findings. Above all be flexible and be prepared to find your own methods. I hope this helps!

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.



These users thanked the author Colin North for the post (total 4): Kbore (Thu May 25, 2023 3:09 pm) • Hesh (Wed Mar 08, 2023 1:36 pm) • rbuddy (Wed Mar 08, 2023 12:30 pm) • Durero (Tue Mar 07, 2023 4:29 pm)
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PostPosted: Wed Mar 08, 2023 10:43 am 
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I miss that guy, he was a wealth of knowledge.

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PostPosted: Wed Mar 08, 2023 1:38 pm 
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And funny too! I did an aggregate if his temp recommends and just do everything at slightly over 300 lol.

I got his DVD set which was great. I got it after I had learned in a very traditional method with a lot of hand plane use and I was amazed to see his modern methods. I adapted many, but it was just really eye opening to see someone doing things in completely different ways. I think he used to work for bourgeois and maybe the other one with the D-shaped sound hole.

Pat

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