Ozbow

Anyone can offer any assistance/guidance/opinion would be appreciated.
A custom longbow purchased earlier 2014 has gone reverse tiller after a few months of use. I noticed after the knocking point had crept high by almost 3/4 inch.
The bowyer claimed the problem was with the way I was stringing the bow. Funny the same push/pull technique, I have also seen used by many others, had raised problems with any of the earlier longbows I have and still posses.
Is it possible the stringing of the bow can cause the bottom limb to weaken or is it more likely something along the lines of the timber laminations (wattle) collapsing as some have suggested.
The bow has seen the top limb rounded/shaved to bring the tiller back to positive by original bowyer.
Is this problem likely to reoccur? I don't believe just re-tillering is going to correct to root cause.

Can you give some detail on the makeup of the bow, all wood laminated, glass laminated etc.

Also some close up photos of the bow could be helpful.

Daryl.

Scubaninja,

On the presumption that your bow is all wood with no glass, I offer the following on the basis that I have done over 100 bows this way with 100% success and no breakages or other problems.

The commonest reason that a wood bow will reverse tiller to negative tiller (weaker lower limb) is that the shooter has a heavy heeling grip when shooting. If the bow had positive tiller when made, it will not change significantly with normal shooting. I have also used the 'step-though' method of bracing for many years and that technique has never adversely affected any of my wood bows . . . ever. That story is another of bowmaking's furphys. Of course the push-pull method will not either.

If you download and read the article I posted on heat treating bows to remove string follow (which your bow has done in the lower limb) you can remove and even strengthen the lower limb to prevent it recurring. I have reattached the PDF for you to download. Many people shoot longbows, either flat or D-section, using a firm full-palm grip. I started this way but have long since used a much looser grip without closing my little finger around the handle and drawing the bow into the ball of my thumb with finger loosely closed.

The worst case of heeling I have seen was used by a mate who actually pushed the bow with the heel of his hand so hard (unconsciously) that the lower limb at the end of the dip was a full 3/4" further forward than the same in the upper limb. That put the limbs out of synchrony which meant that they moved forward at different speeds and badly affected his arrow flight.

Apart from using heat, you could also have shortened your lower limb by around 1 inch to make it stiffer against the upper limb and regain correct tiller. The heat treatment I devised can be used on the one limb only if necessary and does not require the removal of any wood. Normal retillering will almost always result in lower draw weight because of the loss of material unless shortened to compensate.

I am using heat treatment to straighten out the many old bows in my collection almost every second or third day. All of them improve immeasurably in performance and the biggest improvement was with one bow which increased draw weight by 15lbs. Most of them get around 5 lbs and rarely regain more than 1 inch of set from the original 3 to 4 inches of set they had when I bought them.

Anyway, have a think about it. As Greybeard said, it would help if we had some specifics about your bow though.