Self Bow Limb Twist Help

[Drewster]

I'm in the process of building my first ever self bow......70" red oak.  One limb has a twist for about 14" from the tip in towards the riser.  I am in the process of tillering and still have quite a bit of weight to reduce.

I've been told that heating the limb will enable you to straighten the twist.  Would someone please explain exactly how to do this so I don't screw something up?  Thanks for your help.

[John Scifres]

Before you heat it, check the limb thickness from side to side.  A lot of twist can be attributed to differences in thickness across the limb.

[LittleBen]

I think I remember seeing something on George Tsoukalis' site about limb twist and heating ... I'd say check it out. Think he used bar clamps or something like that. But yeah, it's usually related to limb thickness in board bows expecially.

[Drewster]

Thanks Little Ben.  I found George's page where he shows how to fix a propeller twist.  Looks like a good technique.

[Pat B]

Do as John suggested first. Uneven limb thickness is a very common problem and will cause twist when the bow is under stress(braced, etc). If the limb is flat unbraced but twisted at brace it is probably uneven limb thickness.

[Drewster]

Pat, John, this piece of wood has a natural twist in one limb.  I've also been very careful to keep the thickness even on both sides.  It may not be twisted enough to create a serious problem, but it doesn't look very good either.  George Tsoukalas' propeller twist fix looks like a good option for this problem.  Thanks guys!

[George Tsoukalas]

Thanks, Little Ben. Did you cause the twist or was it caused by uneven wood removal as John mentions, Drewster?  Jawge

[Eric Krewson]

Regardless the cause you can untwist the limb with a pipe wrench, a 5 gal bucket and some heat.

Support the limb, put a padded jaw pipe wrench on the spot you want to correct, heat the limb, untwist, hang a bucket with weight(water works well) on the pipe wrench to hold the correction until the limb cools.

 

[Roy from Pa]

X2 what Eric and Jawge said.

[Drewster]

Jawge, I'm not sure if I contributed to the twist or not, but it's there.  I have tried to be careful to remove wood evenly, but maybe not careful enough.  At any rate, your web page solution and Eric's pics looks like the answer.  If I did contribute to the problem, I'll be even more careful with the next bow :-)

[Eric Krewson]

It has been my experience that dog leg and twist are most often caused by stresses in the wood and are no fault of the builder. The exception would be if you are really sloppy on limb thickness side to side with really glaring differences.

I have had minimal success with wood removal from one side or the other to correct twist and dogleg.

My heat gun corrects the defects 100% of the time.

[George Tsoukalas]

If you caused the twist, Drewster, it would most likely would not be there when unstrung. If it is, then take it out with heat. If you string it and it twists then it is uneven wood removal that caused it. In that case remove wood from the high side to fix it. How much twist? If this is a board, next time leave it in the store and choose prime boards that are straight grained with no knots and twists is my advice. Jawge
 http://georgeandjoni.home.comcast.net/~georgeandjoni/index.html