How do you control or modify hand shock in an otherwise efficient bow

[Woodbear]

Hand shock.
What do you bowyers do in the design of a bow, or modifications to the bow during tillering to minimize or adjust the hand shock?

Here is a little background to this question.

I am making a 6 foot long red oak bow with a target of about 35# at 30” of draw. The design is a working handle pyramid style bow, 1.5inch wide at the widest point in the limb at 9inch from the center of the bow. The handle is narrowed to 1 inch wide and 0.75” thick. Limb thickness is about 0.50” (at 9in from center) the tapering sightly to 0.40” at the tips. The bow currently draws 33# at 28”, has no set in the central +/-9” and gentle set in both arms (beyond 9”) of just under 1 inch.
With my release style (two split finger), I am getting 153fps with 353 grain arrows at 28” draw, so the bow is delivering 61% efficiency which is comparable to many of my best bows.

The reason for the question: With this bow I feel the hand shock as a vibration persisting for several cycles lasting for about ˝ second. The hand shock is not severe, but it is the obvious vibratory feel that I find annoying. With my other bows there is a similar amount of total hand shock, but the character is more of a muffled “thump” than a vibration.

So, what do you bowyers do with hand shock?
Do you have a specific favorite design that has favorable hand shock?
Should I ignore it as the bow is delivering good speed & efficiency?
Pad the handle to muffle the vibration?
Re-tiller to a lower weight?
Start over with a design that has a larger rigid handle?

Dave

[Eric Krewson]

Hand shock is usually caused by the limbs being out of time, in your tiler picture the right limb is stiff in the fade and appears stronger than the left limb.

You could shoot a heavier arrow, that would dampen the hand shock.

[TimBo]

You could also try flipping it over.  Are you drawing the string with just two fingers?  I suppose if that is the case, it might not make as much of a difference as one over/two under.  Maybe try that anyway, try heavier arrows, and take a few careful scrapes on the stiff fade Eric mentions if the first two things don't help.  Maybe even use sandpaper so as not to remove too much material.  I have also had luck changing where I grip the bow slightly (if the RH limb is top, I would slide down just a wee bit and evaluate).  What kind of string are you using? 

[superdav95]

You could also try flipping it over.  Are you drawing the string with just two fingers?  I suppose if that is the case, it might not make as much of a difference as one over/two under.  Maybe try that anyway, try heavier arrows, and take a few careful scrapes on the stiff fade Eric mentions if the first two things don't help.  Maybe even use sandpaper so as not to remove too much material.  I have also had luck changing where I grip the bow slightly (if the RH limb is top, I would slide down just a wee bit and evaluate).  What kind of string are you using?

Agreed with Eric and timbo.  I was also wondering what string material as my next question.  Also consider having someone take a video in slow mo mode from the side as you come to full draw and release.  You may just be able to see the timing issue Eric was speaking of.   

[sleek]

I once made an extreme lever/recurve that would shoot the string off. I went heavy in the arrows and it calmed down and became a rather good shooting bow. I have noticed a few things cause hand shock, the obvious mass distribution, timing, and also limb twist only enough. If the limb has any sideways bend it will torque the limb on the draw and that's energy that can't go into the arrow. I have also noticed if I make the bow really long with a low draw I tend to get shock. Probably a mass distribution thing again.

It's great to see you on here Dave hope you have been well.

[Woodbear]

Thanks for the thoughts on dealing with the hand shock.

It is not that the hand shock is severe, a bit of a push or bump is normal (for me at least) and OK, it’s the feel of vibrating is annoying.

The feel of vibration is there with 353 grain to 519 grain arrows.

I am shooting with two fingers, one over and one under the arrow. I started doing this when the third finger got arthritic. Now all my fingers are arthritic, but I have kept the two-finger style anyway.

The string is endless loop, 12 strands of B55. I have 2 strings, one with monofilament nylon serving at the arrow nock, and one with no serving. The serving did not alter the vibration, but does make the arrows clip on to the string.

I tried flipping the bow over, and the feel is the same. However, I am always holding with my hand pressure point dead center. This places the arrow pass (arrow centerline) at 0.60” above the bow center.
The idea of shifting the pressure point is something I have not tried and sounds promising.

Slow motion video sounds like a great idea but beyond my resources at the moment.

To see the relative bend in the two arms I duplicated the full draw photo and overlaid a reversed 50% transparent image on the original photo. The overlaid image is carefully adjusted in angle and position so that the tips exactly overlay. Since both halves of the combined image contain both bow limbs, only one side of the overlaid image is needed for evaluation. At least when I took the photo, the upper limb had about 1 bow limb thickness worth of more bend than the lower.

The bow is indeed quite long for the draw weight. I am trying to get both a 30” draw and a low strain light-ish weight bow, so I can hand it to people un-familiar with wood bows (read that compound & Barebow style glass/carbon recurve) to experience a “real” bow without worrying about over-drawing. This is why the vibration is annoying me, I want a smooth shooter to entice the over-complexified modern archer.

Sleek,
Good to hear that an old acquaintance is still makin bows & posting on line.
I am doing fine, and enjoying semi-retirement. I have had a bit more time for bows of late.

Dave

[bassman211]

72 inches long, bend through riser, B55 string, wood choice, and a light arrow may all be contributing to felt hand shock.  Slightly shorter bow, padded handle, FF string,  heavier arrow, and wood choice could help, and maybe narrow the taper towards the tips. 

[Eric Krewson]

With a bow that long and a B-50 string it could be the string stretch at the shot is causing the vibration. Try a DF-97 string, I use them on all of my selfbows, I don't like the mushiness of a B-50 string.

[Jim Davis]

In my experience, hand shock disappears if the bow is supported without GRIPPING it.

[bassman211]

Yep that helps.... I shoot all bows with just my thumb , and index finger. Just last year I made my son a shorter sinew backed Osage bow that held 4 inches of reflex, and forty lbs at his draw for ground blind hunting. I tillered the bow for thumb ,and index finger shooting. Not thinking that he shoots a really low wrist grip. It went bad out of tiller, and  the top limb broke. I  made it a bend through riser, and had to put an 8 inch splint  on the belly of the broken limb with more sinew on the back to get it shooting again. I made him another one, and got it right for his shooting style, and he won't get to shoot this bow ever again. It is made for me. Looks like sh<<, but shoots good.

[ssrhythm]

The idea mentioned that hand shock is due to the limbs returning to brace out of time…is certainly true.  Too heavy limb tips cause shock…other aspects of the design do, I’m sure, as well.  But limb return timing or limb synch certainly is a big factor. 

I had my current build, a 35# @ 28” Osage longbow build for my son, well tillered with a dead even tiller.  It is asymmetrical with 1.25” up from center and 2.75” down from center handle.  I reduced the top limb to achieve a 1/8” positive tiller, as this is what I’ve read was necessary for this design to keep the shorter bottom limb from being overworked.  There was no hand shock when the tiller was even, but that 1/8” positive tiller added a noticeable amount of shock. 

It makes sense that a shorter, stronger bottom limb will return to brace more quickly than the longer, weaker top limb; it’s stronger and has less mass to move.  It certainly contributes to the felt shock.  I’m going to take the wisdom one sage poster suggested in my “bow-design” thread and adjust the length of my fades to yield equal length limbs on my next build while designing the handle in such a way that the bow string will be pulled as close to the center as possible…and I’m going for a neutral tiller. 

I don’t think I addressed what you are asking, but it’s some good for thought.

[Woodbear]

Thanks for the extended thoughts on de-vibrating my bow.

My usual hold on the bow is with the pressure point in the web of the hand between the base of the thumb and index finger, with my fingers lightly wrapped around the bow.  I tried holding the fingers open and only closing on the bow to retain it after the shot. The vibration is actually felt more as I catch/retain the loose bow. In fact, a slightly tighter hold seemed to dampen the vibration more than the open hold. My other bows of similar length and tiller are heavier and require more pressure on the handle at full draw (forward push, not grip). Perhaps the lighter hand pressure on the lighter weight bow dampens vibration less?

Unfortunately, shifting the hand position up & down the handle in ˝ inch steps made no difference to the feel of vibration.

The B55 string is my concession to the modern world, mostly because I hate having to replace linen or hemp strings, and the B55 is practically indestructible. I also added otter fur silencers to the string. The otter fur quiets the string but not the bow handle vibration.
In my experience linen is less stretchy than B50, so I will have to give it another try.

I have been put off using DynaFlight / FastFlight etc.  by the warnings against using it on wood bows. Can you guys give me your experience on DynaFlight 97 durability and how to protect a wood bow using it? It’s not primitive, but if I can tolerate B55 why not DF97?

Thanks for the thoughts on asymmetry and positive tiller. The bow is nominally absolutely symmetric, and the pressure point of the hand exactly central. The arrow pass in 15mm (0.60”) above center which is as close as I can get it to center. The bow has about 0.10” negative tiller mid limb at brace, but the full draw overlay shows positive “tiller” of 0.40”, so I went with that as the top limb. That said the vibration feels the same with the bow either way up, so I don’t think the positive/negative tiller is significant.
Dave

[superdav95]

The d97 stuff is very good.  It’s my go to for
Most of my bows with some exceptions.  I stick with my b55 or sinew string for my composite horn bows.  I did try to use some d97 on a 5
Piece horn bow build and found faster chrono speeds but not significantly faster.  The b55 seemed to feel little better on the bow.  Can’t explain it really.  Maybe just the right amount of stretch??   Working on a sinew string for this bow now using natural tennis racket string.  Will report on how it does when done. 

[superdav95]

The d97 stuff is very good.  It’s my go to for
Most of my bows with some exceptions.  I stick with my b55 or sinew string for my composite horn bows.  I did try to use some d97 on a 5
Piece horn bow build and found faster chrono speeds but not significantly faster.  The b55 seemed to feel little better on the bow.  Can’t explain it really.  Maybe just the right amount of stretch??   Working on a hog gut string for this bow now using natural tennis racket string.  Will report on how it does when done.

[ssrhythm]

The D97 worried me at first, as I don’t put tip overlays on my bow, and I try to make my tips narrow as possible…resulting in just a very thin area of back ring and not a lot of wood beneath the loop and between grooves.  Despite my worries about D97 damaging the tips, it’s never been a problem. The added performance and crispness of the string is noticeable and worth it.