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Main Boards => The Bowyer's Bench => Topic started by: BenBow on May 31, 2015, 09:58:00 PM
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For years I have had to use at least 3/4" or more to get level arrow flight. I shoot 2 fingers split corner of the mouth anchor. I've tried from 1/2" positive tiller to 1/8" negative and the negative tiller helped slightly. My bows have always had a medium high grip. I did a slow motion video of a bow I finished and was amazed at what I saw. The nocking point was at 3/4" and you can see the nock end of the arrow drop on release then bounce off the shelf. I used to shoot target compound bows and the grip on those bows was low and I was taught to put the grip pressure an inch low on my thumb pad to keep the pressure in a straight line to the shoulder. This worked great with the compound so I've never changed besides it is easier to hold that way when fatigued.
Here's the slowmo video. You may have to run it through a several times to see how it caused the arrow to porpoise.
SlowMo video (https://www.youtube.com/watch?v=pqv5EkaDTcA)
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My sander is still in the shop so I took a trashed riser and mounted a trashed set of limbs so I'd have something to shoot besides the zombie bow I built. The riser was made with actionwood and it started splitting apart in a couple of places so I didn't feel bad taking a rasp to it. I cut the grip down a ways and kept shooting and taking more wood off until it started shooting well.
Here's what it finally looks like.
I've taken about 1/2" off the lower portion of the grip and cut away some more below that where the lower part of my hand rested on before.
(http://i.imgur.com/DHl9DMJ.jpg)
Here's the belly side of the grip showing a small flat spot just below the low point of the grip. You can see the splits in the wood so I hope my sander gets back soon so I can get a new bow made up. But at least now I have a pattern that works.
(http://i.imgur.com/ZwDiBTk.jpg)
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I went out this morning and did a bare shaft test at 30 yards. I'm shooting 28.5" Beaman ICS speeds with 150 grain brass inserts, 250 grain points, 4 3.5" turkey feathers and a 4" aluminum outsert. Total weight is 685 grains and 31% foc. The bow is 44# at 28" and I draw about 28.5". I have the nocking point at 3/8", brace height is 7 1/8", tiller is dead even and the limbs are equal length from center.
Here's my 30 yard group the bare shaft is 3" left of the group which shows slightly weak for my left handed shooting but I'd rather slightly weak than too stiff. I think I've got the nock high issue solved
(http://i.imgur.com/z81nBX7.jpg?1)
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Here's the bow on the tiller tree. Draws nice and straight.
Tiller tree video (https://www.youtube.com/watch?v=PbPX1XqI2YU)
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I don't know what your question is?!
There are a few points about your set-up that are very different to the way I set my bows up.3/4 inch is very high? I only ever need to go 1/8th up, I would never tiller a bow positive because i've never needed to,15.5 gpp is a very heavy arrow, 31 foc is an awful lot, does your tiller tree handle support accurately represent the way you grip the handle? I think your spine is too weak, I personally when bareshaft tuning wouldn't find that degree of difference acceptable, bear in mind that if spine is weak then it will exacerbate any 'ramping effect of nocking point being too high eg. weakness shows itself in all planes.
I think the major cause of a lot of these problems is the fact that you are shooting off a shelf! If you got yourself a selfbow and shot it off your handed (no shelf of any kind) then all you need to do is raise nocking point a fraction at a time until the fletches don't touch your hand....and that will be 1/8th higher than the top of your hand. This is always my starting point for tuning. The fact that a shelf has no feeling unlike your hand means that the waters can become a little 'muddy'!
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Mike a self bow has a flat grip and you're not adding addtional pressure to the lower limb like a pistol grip on an recurve or takedown like mine. Thats why what you recommend is not applicable nor does it pertain to this style of bow. I've been using wood bow rules of thumb and they don't work for this style
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Whole problem is your drawing arm position. Look how high your elbow is... You are pulling upward on the string and most of the pressure is applied with your bottom finger, when you release, the string wants to drop back down and causes wacky arrow flight off the bow. Your elbow should be straight in line with the arrow.
Like this ole boy.. :)
(http://i47.photobucket.com/albums/f165/ROY-CHRIS/bearbowform.jpg) (http://s47.photobucket.com/user/ROY-CHRIS/media/bearbowform.jpg.html)
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I grip them both the same? Eg. I don't 'grip' them the pressure is always on the point between my thumb and index finger regardless of handle style, this way you don't unintentionally change pressure from shot to shot I suppose it's horse for courses but I was just relaying what works for me. I suppose if you are healing the grip then it's going to cause issues that would require a stronger than 'normal' lower limb not the other way round as you seem to be suggesting?
The spine issue still stands regardless. This is the first thing I would sort out.
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Thanks Mike. Yes I do heal the grip to a point but you will see the majority of target and olympic shooters using this method as it introduces less muscle into the equation which is critical when you have to shoot lots of arrows at long distances. Anything that improves consistency is what I'm after. I could adjust my plunger an 1/8 of a turn and that would take care of the 3" spread at 30 yards so its a non issue. Plus this riser may blow up with the cracks so I'm not going to shoot it much other than to fine tune the grip so I can use it for a pattern for the new bow I've got started. I appreciate your comments unfortunately we shoot so different they aren't helpful for me.
Aim small hit small.
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Originally posted by Roy from Pa:
(http://i47.photobucket.com/albums/f165/ROY-CHRIS/bearbowform.jpg) (http://s47.photobucket.com/user/ROY-CHRIS/media/bearbowform.jpg.html)
That's a purdy bow.
That's interesting Galen. I enjoy your musings and experiments. Keep 'em coming.
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Thanks Dave, it's 44 years old.. Bought it new in 1971. Bear Victor Viking take down. Shoots like a rifle.
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Mike got me wondering about the spine so I turned the plunger in somewhere between 1/8 and 1/4 of a turn and here's the 4 arrow group. I'm happy with it. Now if I can just replicate this with the new bows I've got started.
(http://i.imgur.com/zYZkF95.jpg?1)
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I do have an issue with my drawing arm shoulder. Its been dislocated too many times so I have a hard time getting the arm all the way down in line with the arrow without a lot of pain. I've been working on it but the old joint isn't happy about it. I've been compensating by using my top finger less so it doesn't push down on the nock.
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Originally posted by mikkekeswick:
I don't know what your question is?!
There are a few points about your set-up that are very different to the way I set my bows up.3/4 inch is very high? I only ever need to go 1/8th up, I would never tiller a bow positive because i've never needed to,15.5 gpp is a very heavy arrow, 31 foc is an awful lot, does your tiller tree handle support accurately represent the way you grip the handle? I think your spine is too weak, I personally when bareshaft tuning wouldn't find that degree of difference acceptable, bear in mind that if spine is weak then it will exacerbate any 'ramping effect of nocking point being too high eg. weakness shows itself in all planes.
I think the major cause of a lot of these problems is the fact that you are shooting off a shelf! If you got yourself a selfbow and shot it off your handed (no shelf of any kind) then all you need to do is raise nocking point a fraction at a time until the fletches don't touch your hand....and that will be 1/8th higher than the top of your hand. This is always my starting point for tuning. The fact that a shelf has no feeling unlike your hand means that the waters can become a little 'muddy'!
"I only ever need to go 1/8th up" Is that 1/8" from center...?
I go about 1/2" above center and my shooting is not bad at least I'm hitting the target where as before the arrows were going wild.
Is bareshaft tuning a good thing or a waste of time. If the arrows are properly spineded and fletched those that dont fly right get the axe... :deadhorse: Most of the old timers did it this way. Take out 20-30 arrows and shoot them at least 3-4 times each and take note of the lemons. Then they would throw away the bad ones.
Of course this is after the bow tuning is finalized....