Limb twist in fiberglass bows

M Hardman · Post by **M Hardman** » Fri Jul 27, 2007 6:42 pm

Unfortunately, a bow I bought recently develops a mild limb twist (1cm deviation from center at ears) when strung. It is a Grozer fiberglass bow. His website claims that it is correctable by twisting the limb in the opposite way. Is this advisable? Otherwise, I am happy with it, the Bow shoots well and the twist disappears as full draw is reached (as far as I can see).

I hope this problem is not critical.

Mike

Orda Khan · Post by **Orda Khan** » Sat Jul 28, 2007 8:39 am

Mike,
Is this a new bow and is this a recent problem? I'd be inclined to contact him if the bow is new.

M Hardman · Post by **M Hardman** » Sat Jul 28, 2007 11:53 am

Yes, its new (from shop, I do not know how long they have had it) , having tried it this morning, it is a very pleasant shooter. It has a 9 month shop warranty so perhaps I shall wait to see if it gets worse.

Thomas Duvernay · Post by **Thomas Duvernay** » Sun Jul 29, 2007 6:56 pm

Korean bows made for the Korean market are often curved towards the arrow side. For those who like a center-strung bow, it is easy enough to correct.

In hot months, no preparation is needed. First string the bow. Next, while holding the siyahs from the curves just below the nocks, push the handle into your belly. Carefully, flex the upper nock (held in the right hand) so that it becomes straight; hold it in place for about thirty seconds. Switch the bow in the hands and repeat for the other end. It is important you do not bend the ends back and forth, and only hold it in place in one direction. Also, it is equally important that you bend only the upper part of the siyahs; bending them on the lower part could twist the core.

In cold months, warm the upper siyahs over a flameless heat (like with an electric hotplate). Hold the siyah over the heat source about 20cm, moving it around (don't hold it in one place, or else it could burn). Next follow the directions as shown in the paragraph above.

Of course, as someone else mentioned, if the bow is new, you should first talk with the bowyer.

T

M Hardman · Post by **M Hardman** » Mon Jul 30, 2007 7:18 pm

I do not think that it is new from Grozer, as it was in the shop when I bought my first bow, about 3 years ago. He says that he has now stabilized the C-form Turkish design, perhaps this is what he meant.

Thomas, thank you for your information, the method you have described does indeed remove the problem, but after a few shots the asymmetry returns. I think perhaps as this is the UK it is not quite hot enough. I believe that the irregularity was probably introduced by bad stringing inshop. I will purchase the next bow direct to avoid this.

regards

Mike

Orda Khan · Post by **Orda Khan** » Tue Jul 31, 2007 3:47 pm

M Hardman wrote:I believe that the irregularity was probably introduced by bad stringing inshop.

Almost definitely. I have seen the common 'push/pull' method used many times so that someone can try out one of these bows.
I am particularly fussy and won't allow anyone to draw my bows. Buying direct should ensure the bow is yours and only yours.

M Hardman · Post by **M Hardman** » Fri Oct 05, 2007 6:09 pm

I have just recently been brave enough to heat my Fiberglass Turkish bow's limbs as Thomas suggested. It had a positive effect for a short while, but after a few shots the irregularity returned.

I am not in fear of the bow de-stringing itself on me, but I wonder how common (or uncommon) this little problem is. Grozer's website claims that hornbows do not twist, implying thereby that fiberglassbows do, is it true that full C-form fiberglass bows will twist because of the material? On closer inspection, the siyahs are not glued into the limb at a perfectly perpendicularly in either plane, I think this my be some kind of method to offset the limb irregularity.

I hope this will not put anyone off Grozer's bows, both of the two bows I have bought that were made by him have surpassed expectations in terms of cast and handshock.

Regards

Mike

Bede · Post by **Bede** » Fri Oct 05, 2007 9:58 pm

I am surprised that Grozer's site would suggest that horn bows don't twist. They do and do it more often than Fibreglass laminates. One of the skills of the composite bow owner is the knowledge of how to correct a twist. The Koreans are experts at this and it was well known in China. Even Japanese bamboo laminate bows can twist and there are special ways of correcting it.

Wider limbs have less propensity to twist than narrow ones. I had a bad experience with limbs going out of alignment at the American National Flight Archery Championship. I had left a bow braced on tepeliks to weaken it for a weight limited competition and it went out of true slightly. Twice the string came off as the arrow left the bow. Since I was shooting 14 inch darts with an arrow guide, I decided to stop at that point. Now I have to sit down and heat and correct it until it is stable again.

M Hardman · Post by **M Hardman** » Sun Oct 07, 2007 4:36 pm

Is twisting inherent in high stress bows then? To be honest, I am not sure if my limbs are out of true or not, because of how the siyahs are glued in. The splice and the string line up throughout the draw though.

Mike

Tapio Manner · Post by **Tapio Manner** » Fri Oct 12, 2007 2:43 pm

Is twisting inherent in high stress bows then?

Not really, only in ones where the materials are not isotropic and where the principal direction of the material is not quite parallel to the main structural axis.

TM