Bending the stick #2

This photo shows a stick which has been rough cambered.  The stick has been planed down considerably from it’s initial size after being selected.  I like to remove as much material as possible to relieve stress on the stick during bending.  As stated in an earlier post the stick is heated section by section gradually working from one end to the other as the curve or camber is induced.  I use a heat gun with a temperature range from 0-1100 degrees.  Normally the sticks are rough bent at about 650 degrees.  The curve is formed by hand bending the stick over the edge of my bench.  The stick needs to remain straight at the same time that the camber is established.  An interesting side note to this process is that often the stick will twist from one end to the other as it is bent.  This presents no problem though as enough material is left on the stick to facilitate more planing and everything can be brought back into axis.

It is very hard to keep your cool as a bow maker when this happens!  Time has been taken to carefully select a stick.  Tools have been sharpened for the work.  Perhaps an hour or two have been spent planing the rough stick down.  Now the maker is bending the stick.  In this case I was about 2/3 finished, probably another hour of hard work.  Suddenly the stick gives way like butter under the same amount of pressure used on the rest of the stick.  This was a beautiful, strong, and resilient stick and now it’s highest use might be as repair material!  It cannot be overstated how difficult it is to obtain pernambuco of this quality.  It simply isn’t available anymore short of a bow maker’s estate sale.  Player’s can acquire bows with wood of this quality but maker’s have great difficulty in replenishing their supply.

In the next post I will fit the ivory tip plate and ebony liner.

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7 Responses to “Bending the stick #2”

  1. Daniel Says:

    What type of bow knife do you use?

  2. Robert Morrow Says:

    I buy old straight razors at antique stores and regrind them. The thin variety of straight razor is common and will work. The best ones have a heavier blade and are my preference. They are a lot harder to find though. My current knife was a beautiful Sheffield razor. It was a shame to grind it up but it makes a great knife. I use a single bevel and you can put it on whatever side suits you. There have been other questions on tools so it looks like I should do a post on tools. There will be photos to reference.

  3. Daniel Says:

    Thanks. I made my first from a Sheffield straight razor, but a different grind. I would like to attempt the single bevel.

  4. Joseph Pagán Says:

    Regarding the above picture of the broken stick: Does the fact that the stick broke in the process of being shaped indicate that there was a flaw in the wood? BTW, still loving my viola bow.

  5. Robert Morrow Says:

    Hello Joseph,

    It does indicate a flaw, one that is nearly impossible to see ahead of time. I think that there was already a compression fracture in the stick. Apparently the forces exerted on a tree while it grows, leans to one direction or the other, and is whipped by the wind can compress areas of the trunk and fracture the wood fibers. This type of fracture causes a sudden failure of the wood under very light pressure. Fortunately, this type of failure will always be found in the initial bending.

    Nice to hear from you, and glad to hear that you are happy with your bow.

    Best regards,

  6. Andrew Bellis Says:

    Dear Robert, as a time served (32 years) British bow maker, can I make some suggestions to maybe avoid the broken bow stick problem? Firstly, work your stick blanks to a more dowelled cross section – I have never tried springing square section blanks, the ‘corners’ are a stress riser. Second, make sure there are absolutely no flaws on the underside of the stick that will similarly cause (in tension) a crack to start. Third, use a heat source with moisture in it – electric heat guns are far too dry; try gas (propane, a bunsen burner with a very ‘gassy’ flame), or for violin sticks, a camping type spirit stove. The true test will be springing a double bass bow; if you can do that, violin bows become remarkably easy!! Best wishes, Andrew Bellis, Bournemouth, U.K.

  7. Robert Morrow Says:

    Thank you Andrew. I appreciate your input and will give it more thought.

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