What The Heck! Bow Tip Adjustment?

[2fletch]

Earlier today I was experimenting with something that I read recently. Someone was saying that you could put rubber tubing over the limbtips to dampen the noise on a noisey bow. Well, I had a really nice bow, but it shot low and a little irratic, with some vibration.

I put 3" of about 5/8th inch tubing on each end and let fly. There was a slapping noise. On the second shot the bottom piece came off. Out of curiosity I shot it again with just the top part on. Just like that, the bow shot where I pointed it, and was quieter. Then I cut about another inch off of it and saw little difference, so I left it there. It was amazing that this worked so well. To further varifly this I put the tubing on the bottom limb and it shot even lower then before. It occured to me that this might be an easy way to correct a bow that shoots high or low.

I wouldn't suggest putting a large weight on the tip of a bow and shooting it. The tubing that I used was about 2" in length and weighed about 100 grains. I had it far enough on the tip that it didn't flop. I'd like to hear some of your ideas, opinions, and experiences.

[Msturm]

Do you think you results reflect an imperfect tiller in the bow and the added weight moved it closer to a more symmetrical tiller?

[RJonesRCRV]

Sturm might be right

[ozy clint]

is this the idea you heard of?
 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=153461

[2fletch]

That's it. I was curious to check out what you had done clint when I ran into the tuning thing.

I think that  as sturm ask, "Do you think you results reflect an imperfect tiller in the bow and the added weight moved it closer to a more symmetrical tiller?", that it had to do with the tiller not being right for my 3 under method. It was amazing how the bow quieted and started grouping around the bullseye. If I ever have another bow that wants to shoot high or low, I'll go to this as another way to tune.

[McDave]

I recently got a high quality recurve that won't tune.  There is always a little kick to the bare shaft, no matter where I put the nock point.  The recurve is tillered for split, but in the past I have generally been able to tune split tillered recurves for 3 under by adjusting the nock point.  I think I'll try putting one of these tubes on either the top or bottom limb to see if I can quiet it down.

[kenneth butler]

McDave, Could your new bow have a little more positive tiller than normal are what you are use to? Have you measured it? >>>---> Ken

[McDave]

It has a tiller of about +1/8", which is actually a little less positive than most bows tillered for split that I have seen.  It shoots great, but I can't seem to get the nock high any lower than about 15 degrees, shooting a bare shaft 3 under.  I prefer a nock high of about 5 degrees, even on bows where I could get it down to zero degrees, if I wanted to.

The odd thing is that I have tried shooting it split fingers with a bare shaft, just to see if I could tune it that way, and I still can't get the nock high lower than about 15 degrees.  It occurs to me as I write this post that maybe I should play around with brace height to see what effect that has, if any, in addition to trying the tube on the limb tip.

Another odd thing is that the nock high occurs from about 5-10 yards.  By 15 yards it has gone away.  Most bows I tune, the nock high stays or gets worse with distance.

Since it shoots great, I should probably just forget about it, but I am still open to trying new ideas to see if anything makes any difference.

[2fletch]

McDave, it will be interesting to see what you come up with. It's a pity to have a bow that you want to shoot but for one reason or another it won't settle. I have made a few bows, but I don't like to remove material from someone elses work to get the tiller right. I'd like to hear what some of the bowyers would say about this.

[McDave]

Thanks Don for letting me hijack your post, but since you asked, I will continue.  This morning, among other things, I decided to switch the top and bottom limbs to see what happened.  I frankly expected awful bare shaft flight, so stood close to the target for the first shot.  To my amazement, the bare shaft flew perfectly!  I got the 3-5 degree nock high that I wanted without changing the nock point of 5/8" I already had from 5-20 yards.

As I said, the tiller was +1/8" with the limbs on "correctly."  With the top and bottom limbs switched, the tiller was zero.  I didn't expect that either.  I thought if I swapped the limbs, the tiller would be negative.

I can only come up with two theories to explain this:

1.  The limbs were mismarked top and bottom, and were really tillered for 3 under.

2.  The limbs were correctly marked, and intended to be tillered for split, but weren't tillered correctly, but through some kind of fortuitous accident, were tillered correctly for 3 under when swapped top for bottom.

Neither one of these seem very likely, but that's all I can think of at the moment.  Meanwhile, I now have a bow I like to shoot, as long as I can remember to put the limbs on upside down if I ever take it apart and ship it somewhere to hunt with.

[kenneth butler]

I am glad you got it squared away. I ran into a weird tiller thing, like that. I was taking weight off and the tiller only dropped 1/16 on the upper limb. From 1/8 to 1/16 but reversing the limbs didn't change it.I shoot 3 under also so all is good. Maybe it has something to do with the limb pocket angle. Any way it is over my head. >>>---> Ken

[LC]

I'll go out on a limb here and be devils advocate! IF this works for your bow it is so overly spending energy in all the wrong places that one should look beyond this remedy!

[2fletch]

LC, how many times have you picked up a good respectable bow and it just didn't shoot right. Granted it would seem inefficient to put weight on one tip, but I believe that it might have produced more efficiency with the arrow flight, resulting in better penetration. The arrow speed was not checked before or after the adjustment so that is not verified.

A customer left with the bow after seeing the change in how it shot with the heavy duty tip protector. I may not get it back since it's on a trial basis. If it does come back to the shop I'll spend some time to find out exactly what weight tip is optimum.

Just for the record LCDA, it does seem like the lesser way to correct a tiller based problem, but the results were good and easy. I have wondered if this could cause limb breakage, but the harmonics seem improved with less noise and vibration.

[McDave]

the harmonics seem improved with less noise and vibration.

The same thing happened with my bow when I swapped the limbs.  It is quieter, and shoots a bare shaft without the blips it had before.  The bottom line is that it picked up 5 fps in speed, from 180-185 fps with a 9 gpp arrow, which I am sure is because of eliminating a lot of the vibrations and timing problems.

If putting a piece of rubber tubing on it had done the same thing, I would have done that, even if it did make the limb tip look uncircumcised.