over-the-tip stringing

[godfreymik]

Some time ago, I found some discussion of passing the loop of a string around nocks then up the back and over the tip.  As I remember, there was discussion of the mechanics, eliminating any weight beyond the strung length, made sense.  The led me to making this black locust bow.  56" long, at 20" it draws 42 lbs. Using a 20 g. arrow, it shot 148 FPS.   Similar bows I have made in the past with traditional knocks seem to shoot 135-140 FPS. (I think I will tiller it to draw 24" at 45#.)

Now I am trying to figure out why this style is not more common.  It is harder to string, but seems to make a faster bow.  Does anyone have experience with this?

[sleek]

Absolutely brilliant idea and great first post. Welcome aboard! If you do this type of work and thinking, you will certainly be a huge asset to this page. Thank you for signing up, and I think you may have just changed how I make my bows forever.

[ajooter]

Very interesting!! The only thing that might present a challenge is alignment.  It may be harder to get a snaky stave to line up.  I will definitely give it a try.  You would be able to glue your nock overlays on with the grain orientation perpendicular to the back of the bow as well.  Cool stuff!

[Eric Krewson]

I would be worried about the limb splitting down the middle, I had a string slip out of one side nock once, I didn't notice this, when I shot my bow the sring split the limb 6" down the limb. I was using DF-97 for a string which is rougher on bows than B-50.

[sleek]

I would be worried about the limb splitting down the middle, I had a string slip out of one side nock once, I didn't notice this, when I shot my bow the sring split the limb 6" down the limb. I was using DF-97 for a string which is rougher on bows than B-50.

Good point. A wrapped nock or bone tip overlay would fix that.

[mmattockx]

Welcome new guy.

From last October:  http://www.primitivearcher.com/smf/index.php/topic,72949.0.html


Mark

[TimBo]

I don't know...this idea seems a bit over the top.

[bjrogg]

I saw this somewhere before. I think here. Even had some numbers comparing the same bow with it over the top compared to conventional.

I think it’s a really cool idea.

I see mmattockx already shared the link.



Bjrogg

PS love the tiller, nice bend

[superdav95]

its a cool concept.  yes i remember the topic has been posted before.  My opinion for possibly the why it works to get more speed is this,  the over the top string nock in theory maximizes the length per mass of the limbs compared to using the regular cut nocks.  even if you use the same string you would essentially lower the brace height as you are using the loops around the nocks in the traditional way.  this method would increase your brace height a little and push that energy transfer out a tiny bit on each limb. There is also the elimination of string rub on the sidewalls of the string grooves, every little helps and in this case it seems to translate into little more speed.  This also may in fact add a tiny bit more draw length as well which may contribute to more speed along with the other factors. 

[Del the cat]

Interesting post... no wasted wood beyond the nock 
Del

[godfreymik]

I finished this bow and did the experiment.  Same bow, same string tied to get the same brace (5 1/2").  I shot the same three arrows, once with the string over the top and once with th string nocked normally.  The results surprised me with the dramatic difference. Over-the-tip: 145.2 FPS, 146.4 & 142.8     Normal nocking: 131.6 FPS, 132.2 & 132.8.

I'm glad I was lurking on gratis site when pierce_schmeichel posted last October.

[Badger]

    That is a dramatic difference. I think I see why, but I am not sure. I kind of suspect that the knock style you are using breaks over a little like a recurve giving you a little let off right around that 18 to 20 inch point of your draw. It might flatten out the curve at that point giving it performance of a bow maybe 6# heavier.

[bassman211]

I have tried it on 2 different length bows. It showed some difference on the short bow that was reflexed, and none on the longer bow that was deflexed. The example above shows that you made a  longer  bow. When I did it I shot first through the chrony 10 shots with the normal nocks.. Then I cut the v, or u groove were the regular limb nocks were.  It is puzzling to me , but that is what it showed through my chrony. The weather is breaking now, so  I will try it a few more times with some of my older less cherished self bows. Both long, and short.

[superdav95]

I finished this bow and did the experiment.  Same bow, same string tied to get the same brace (5 1/2").  I shot the same three arrows, once with the string over the top and once with th string nocked normally.  The results surprised me with the dramatic difference. Over-the-tip: 145.2 FPS, 146.4 & 142.8     Normal nocking: 131.6 FPS, 132.2 & 132.8.

I'm glad I was lurking on gratis site when pierce_schmeichel posted last October.

Ya I believe that string groove friction and moving of energy transfer out to very tip is part of the reason at least for performance improvement.  I am presuming that you achieved same brace height by twisting the string a bit? Good experiment actually.  Those string grooves look nice a neat with burnt in grooves.  I do this on my yew bows.  I may have to try this on a longbow to see what happens.   

[Badger]

 The speed difference represents only about 3ft#'s, but it is over a 20% jump in power. Would you mind doing a force draw curve on those two set ups, at least the last 4" or so.