Main Discussion Area > Horn Bows
Finished composite hickory bow/ pics
BowEd:
The horn was tapered before I glued it to the core.The core was tapered too before glueing.The tips do work a bit but the horn on the inner 1/3 is fairly thick.Wish I could explain it too.All I know is I got it into good tiller and I'm leaving it.I should just do another fdc on it maybe.I'm bumbled by your question too.I guess the bow does what it does.
I don't know if you got Adam Karpowicz's book to be on the same page with me but I'm trying to figure out something.How well to measure a bows' capabilities of putting energy to an arrow. On page 171 he talks about a useful coefficient[Ce] to compare stored energy of different bows is the ratio of the measured energy to the energy of a bow with the force-draw curve exactly straight at the same draw length and weight.In modern bows,a ratio of stored energy to the peak draw weight[SE/PDF] is another common indicator.The higher the Ce or SE/PDF the more energy a bow is capable of storing.I don't know if he's talking here about how well a bow is capable of putting energy out to what it has stored or what.He says good modern bows have the SE/PDF in the range of 0.85-0.96 for 28" draw and 0.92-1.04 for 30" draw.Does this just all mean a bow gets more efficient shooting heavier arrows or what?I'm confused.
DC:
No, I don't have the book. I'm not sure that I fully understand what you're saying but it sounds like,"If the FD(force/draw) curve is humped, it's good, if it's sagging, not so good." If Adam's coefficient is comparing his FD curve with a linear one then we're thinking along the same lines. I'm going to do some googleing along the lines of "understanding an FD curve"
BowEd:
Yes I was thinking so too.That it means a straight line fdc is not as efficient as a humped fdc showing stored energy.
mikekeswick:
The initial 'hump' is there because of the unbraced reflex the bow has. The more reflex - the more force required to get it to brace. The tighter the string at brace the more of a 'hump' you will have because you simply have to pull harder due to the 'preloading' of the limbs making the string tighter. An average wooden bow simply cannot have the same amount of unbraced reflex therefore the string isn't as taut at brace requiring less force to start it moving.
A big hump is good!
When you have actual recurves you will also get a point in the f/d curve where the string lifts off the recurves this will make the bow longer and thus more leverage to work against bending the limb making the last few inches of the f/d curve level off.
BowEd:
Yes the bow should have more set back in the tips.That might increase fdc hump too.It's still a blast to shoot.
Here's 3 short videos of shooting the bow,including shooting through the chronograph[I reweighed the arrow after shooting and it was a 630 grain arrow @ 11.8 gpp] from a 53# bow @ 28" @ around 175 fps which puts the efficiency of the bow a little over 79% and the kenetic energy of the arrow to 42.8#'s.Crappy short drawed form and all target shooting.....lol.At twenty yards though even at that draw the cast is pretty decent.Without the more extreme set back bends of the tips it braces much easier.Video of that too.Very stable easy to work with bow.I've shown about as much about this bow as is necessary.More than most I've made.Mostly because it is that enjoyable to shoot for me.Thanks for looking.
http://youtu.be/tzI_SemADvc
http://youtu.be/6K5--yTZ5T4
http://youtu.be/dYYro-hmpD8
http://youtu.be/eOCt26XTOKQ
Well I could'nt resist knowing exactly what a 500 grain arrow would do through this bow.I had Robin video it.I shot the bow a couple of times before testing then through the chronograph.After seeing the results I reweighed the bow at full draw.It is pulling not quite 55#'s @ 28" now almost 3 months later.Around a 1.5# increase from last testing.Sinew curing the reason I'm sure and it being winter time here in Iowa too.I don't think I come to complete full draw yet though testing.Maybe 27.5".Results were 210 fps @ 48.95#'s kenetic energy @ 89% efficiency with a 500 grain 9gpp arrow.Somewhat comparable to your turkish horn bows yet from my investigating.Here's the video:
https://youtu.be/gmrye1L5_Ks
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