Just a question for all of the lap top physicists on here.

Which causes the greatest stress in a bows nocks during shooting.

A low brace height or a higher brace height?

I really don't think the issue of limb tip stress is of any concern. Although, I guess in theory the lower brace MIGHT because the limb tips would travel a little further.

The biggest concern would be the stress at brace due to the higher brace height, and while it is strung. The limbs are under more stress all the time.

Although in a glass laminated bow I don't believe it to be much of an issue. In an all wood bow, big issue in my mind.

I think a simple way to check it might be to hook a scale to the string and pull stright down parallel to the string and see which took more force to cause the string to go slack. Lower brace height having more tension would not surprise me. I have always wanted to check this but never got around to it.

Not sure why it would be a concern, especially when so many think it's okay to let bows strung indefinitely. That's one reason I unstring my bows after each use. It just makes sense to me that a strung bow, no matter the brace, is under stress. How much that affects a bows life is up for discussion....not that we haven't been there and done that.

Uhhhh, I believe that Bruce's hypothetical question is wondering about the greatest stress during "shooting".

I'm not sure how shooting would make any difference. You are still pulling the bow to your draw which just changes your power stroke, not the total pull of the limbs. At rest you bow just has more load on it.

If anything I would think a higher brace would be easier on the limbs. But for the most part it's that sudden stop at the end of the stroke that's the most stressful. That's why the light arrow thing, with lighter arrows the limbs are moving faster when they hit that sudden shocking stop at the end of the stroke.

I think a lower brace height creates more stress on the nocks than a higher brace height. With a lower brace height, there's a longer power stroke, that means more power, and more shock. Raising the brace height reduces felt recoil in a bow because we effectively stop the power stroke short.

I agree with jeff, I saw a slow motion video of bow limbs after the string release on a low brace height and the recoil of the limbs were unbelievable because there was not much poundage holding them, they looked like a hula girl. I'm surprised it didn't come unstrung. The light arrow thing with fast flight string increases the shock on the limbs no matter what the brace height. This is my two centavos................wing

My thought here is that a given bow is designed to be shot within a certain range of brace height. Stay within that spectrum, and unless there's a defect, assume it will be fine. It's not something I worry about though'.

Nope, last thing in my mind is stress when setting my brace. If the bows that fragile it's time for another brand bow.

I routinely shoot extremely light arrows from my longbows that are braced very low. I grind off most all of the material above the nocks and get almost zero over travel. To me that is the thing that ruins bows, too much bulk above the nocks. Even with normal brace and 8-10 grns/lb., it makes a real difference. Daniel Perry showed that to me some years ago down on the Salt Flats. A fellow was making board self bows and every one of them broke on his first shot. Daniel asked him if he could modify his last effort and shoot the bow for him after. The guy agreed and Daniel took out his knife and whittled most all the wood above the nocks away and then shot several arrows with an abusive loose and handed the bow back to the guy. He set a new record the next day with that bow. I tried it on my fiberglass/carbon longbows and found that it makes a difference there also.

Mr. Hatfield, how much material would you remove off the nock on a fiberglass/carbon longbow? Both nocks? Same amount? Thanks. God bless.

Mr.Hatfield,

If you are removing material outside/above the string nocks, and it changes the speed of the limb travel, how would you avoid, or measure, differences between limbs? And, is there any benefit to one limb traveling faster than the other?

I remove all but a tiny arrow shaped piece about 1/4" high and wide. It does not speed up a limb, that's not the purpose. It DOES eliminate any over travel of the limbs after the shot on my bows. Over travel is harder on the string and tips than anything to do with brace height, in my opinion. If it changed the speed of a limb I would expect the change to apply to both limbs so that's not a concern. Tiller addresses that.

So would a fast flight string reduce the amount of overtravel on a bow with big nocks versus a bow with big nocks and a b50 string?

I use fast flight, (halo), and had over travel before I ground off the excess.

Very interesting stuff Mr Hatfield. I would like to see a picture. But I am guessing that for the most part these nocks look a lot like the nocks on the bottom limbs of a lot of bows. It amazes me how many bows have a micro nock on the lower limb and a dagger sized one on the upper limb. It makes sense from a safety point of view, but not so much in any other way. The safety issues being overshooting nocks when stinging, but that is a newbie type thing for the most part.

I did see a picture that google dredged up for flight bow nocks, it was a crossbow. :)

One bow that had really small nocks was my Widow MAII, it was hard to find them with some stingers. The bow came with a special stringer.

here is a picture of one of my bows being shot by a young lady. Notice that you do not really see much of anything above the string.

another view.

I would think low brace height would place greater stress on the tips, due to the increased power stroke. Flight bows are under high stress shooting those light arrows. Here's a Drake tip. You can see it's smaller than a dime. Thin too.

Joe

My tips are much smaller than that. I shoot really low brace and have never had an issue with a limb or tip on any of my bows. Through testing over a bunch of years, I believe over travel of the tips and limb after releasing the string is the cause of most damage to a bow than any other factor except poor workmanship.

I don't think ultra-tiny tips are practical for general shooting/hunting though, unless one can easily use a block stringer like a Selway. I'm not so sure large tips, unless overly large, are responsible for stuff like hand shock. I think limb timing is most important but am just suspicious of it. Limb straightness too. Even a slight twist that comes back into the string groove as the string fly back in place, can cause hand shock and poor shooting characteristics in my experience.

Joe

A bit off the Op's question, but has anyone found that the use of low-stretch strings on older bows changes the brace height at which a particular bow may perform best? Whether or not that results in more stress remains debatable.

I wonder if hi-speed photography has been used to show any difference in oscillation between dacron and low-stretch strings. Less oscillation would seem to reduce stress on limbs.

I have never used a stringer on any bow, but I remember that when we had to use epoxy when the only glass was Gordon, and urac would not glue it, we had to make our tips bigger so stringers could be used on all the bows because of the glue creep inherent to epoxy and the ease of twisting a limb. Until then almost all of the bowyers made small or tiny tips as pictures of old bows show all the time. With urac, the only way you could twist a limb was to heat it or mess up tipping the bow.

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