heat treating a hinge

[radius]

I have almost completed a pyramid shaped reflexed bow of osage backed with hickory.  The limbs are lenticular, my first try at that.  Looks good, feels good.

PROBLEM:  HINGE:  it's not a huge hinge, but it's there, and is the result of too little practice with a too-sharp scraper.  I wonder if I heat-treat that spot, would it temper out the hinge?

[mullet]

  I've had limited sucess doing that. I had a bow with a weak limb, and toasted the heck out of it and then burnished. The weight came up by two pounds and the limb stayed where I wanted it too. All you can do is try. The worst that can happen is it will break sooner than later.

[radius]

anyone else?

[Ryano]

I would remove material from either side of the hinge area to get the limb bending evenly and then reflex and heat treat the whole limb to gain some strength on that side.

[radius]

of course ... too late for that now...it's a mild hinge, let's say an over-enthusiastic bend...and i just tillered the other limb to meet it or so, and then sanded it clear...

but in the future....!

[Gordon]

I've had some temporary success with heat-treating a weak spot. But it usually comes back over-time.

[RT]

when u are using the C clamps and block method in gluing up your form, sometimes when your pre-tiller lams are not "spot on" they will tend to bend unevently when u clamp them up.

I have had much success in "heat tiller" u will need experience to tell u how much to heat as too much heat will cause the glue to delam (i use smooth on) heat a little and force bend that area that is not bending enough.

Most important , do it little be little and take your time, cheers Robin

[GregB]

I have seen a thin patch applied on the belly at the hinge work. That along with heat treating and removing the stress on the hinge by removing material on each side and the other limb as Ryan said. Sometimes I think a combination of "fixes" might be the ticket...nothing ventured, nothing gained.

[broad_head]

Hi All
        I have read in the TBB 4 that a thin layer of raw flax can be used to correct a weak spot in a limb. I have just got some to do a repair, but as yet have not tried it! Would interested to know if it works?
                                                                                            Peter (UK)

[Pat B]

Depending on how severe, a hinge is where he cells has collapsed due to over stressing. No matter how much heat treating you do the cells in that area are still damaged. An overlay of some kind or replacing the damaged wood with an inlay would be the most effective method. You might get a quick fix with heat treating but I would imagine it would be temporary. I haven't tried it but I don't think I could trust a hinge that was just heat treated.  If the h9inge is just beginning, Ryano's method would be your best bet.       Pat

[Kegan]

It's worked for me, but only on flatbows. Haven't got it to work on narrower flatbows.

[Marc St Louis]

The heat needed to temper the belly will damage the glue

[radius]

thanks, it's just yellow glue, too

i am just going to live with it, and chalk it up to experience...

[radius]

ok!

'nother hinge!

This one is bamboo backed maple, the bow is 60" long in total, and came in underweight at about 42# at 28".  When I first drew it to 28, it developed a hinge which was not present before. 

I am going to heat treat the whole belly, both limbs, but concentrate especially on the hinge.

Question:

When I sand out the "char" won't the benefits of heating the bow be lost?

[George Tsoukalas]

I usually become unhinged when I see that frightful hinge. Those inevitable chrysals just ruin that stave for me. There are fixes But...The best way to fix a hinge it to not get one. Avoid power tools when tillering until you've made 2 dozen bows. Take long strokes with your wood removal tool often going beyond the target area by a little bit and when possible remove wood from the whole length of the limb in one pass. No, I would not use heat. I would remove wood from either side of the hinge and retiller the other limb too. I would not add any more stress to that limb by reflexing or recurving. I would add some rawhide or 1/8 inch thick birch bark to the belly over the hinge. This is what I would and would not do. Have and have not done. Jawge