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Greg Sigworth

Bending violin "C" ribs

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I am making a couple more violins and I am back to bending the ribs. This will make seven total violins made. They have turned out well and are in the hands of players who are glad to have them. I could use some advice on this process of bending ribs. I use a home made bending device made from plumbing pipes and heat with a small propane torch from the inside end of the pipe. I have to be very careful or the wood will burn. Temperature control is tough and when water bounces off pipe I will start. Then there is the question of how much water to use and how to apply it. Also, should I bite the bullet and buy an electric heating iron designed for this? Please don't be horrified by this. everything I know about this is from reading books or the internet and trial and error. I soak the ribs for about three minutes and then begin. When the ribs are bent, not perfect fit to inside mold but close, I apply some more water with a small brush to ribs and then fit them to the mold. When they are fully dry I take them off the mold to which they now fit quite well. I made a clamp for the "C" bout ribs that pushes the rib into the mold and works, Johnson, Courtnall in The Art of Violin Making shows a  C bout clamp similar to this, but mine has some small steps in the surface that touches the ribs. The rest of the ribs on the violin are not as hard to do as the C bout ribs. I have tried to use a bending strap but using a block of wood to hold the rib to the pipe and slowly bend to the pipe is what I have done. I could use some advice on this. Thank you.

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Instead of copper plumbing pipes try using iron pipe. it's much easier to control the temperature.  Copper get's really hot and will burn the wood easily,  Iron not nearly so bad.   Try using an old leather belt for a bending strap,  I found that works well.  

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Thank you all for the help. I was reminded by my wife of the first violin I made. I used the Hoover vacuum hose ( Al part) for my bending iron. I think I will invest in a good bending iron. The current version I have is made out of cast iron plumbing parts. I believe the part which I bend against has a zinc coating on it which prevents rust. 

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I found that just wetting the side of the wood in contact with the iron is sufficient.   Not a huge amount of water just dip your fingers in a bowl of water and wipe it on the wood.  Worked well for me.   Flick a few drops of water on the iron to test the heat.  Oh and apply a good amount of pressure with the bending strap.  It doesn't take long to get a feel for how the wood is bending and when to wet it some more.

I first tried using wood forms and an old electric clothes iron... that did not work! 

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The shape of the bending iron is pretty important. I use  the ones from Gewa which are a sort of flattened egg shape. Brass or iron are better than copper or aluminum and they can be either electric (nice ) or heated on a hot plate or with a torch and then clamped in a metal jawed vise. Thin brass or steel with wooden handles can be used for the strap although a steel one will come with the good commercial irons. The proper heat is when water just beads and bounces off the iron. Best to use just a little water and to work fairly quickly with a lot of pressure from the strap. You are best off with the rib radii bent slightly larger than the form so that when you push it into the form it will tend to make a "fair curve" which is smoother than trying to bend exactly to shape. Lastly don't under estimate the importance of having the rib thin enough. 1mm is about right for a violin and more figured wood needs to be a tiny bit thinner rather than the other way around.

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