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My R&D build up for WTT3

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My R&D build up for WTT3

Postby jwillis » Thu Oct 16, 2008 8:15 am

The fun part of bow making for me is sharing ideas and photos (and especially seeing those of others), so I'm starting this thread to show my research and development process for the next Walk-the-Talk (WTT3). I have nothing to hide and everything to gain from your feedback, so like the naked archaeologist on the History Channel (one of my favorite shows...lol), I'm going to lay my bow making bare...I'm going to peal back the outer layers to show what I am thinking and testing as I tweak and peak my hybrid longbow design until, hopefully, it will be fast enough to live up to the name I have given it--"The Hammer." I named it that because once it is peaked and tweaked it will "hit like a hammer and drive em deep." :lol: If it isn't obvious by now, you should know that I work in marketing...lol. Ernie, for one, asked if I would do a SuperTiller build along. There may be some of that I can show during this process as well.

OK, so let's get started...
I took two longbows to WTT2 last year at Ken's. Both from my 64" hybrid form with 2" deflex and 4" reflex.

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My son's bow was about 48#@28 and mine was about 53#@28. Both good shooters but they had overbuilt tips and 14-strand D97 strings with two extra strands in the loops plus cat whiskers. These bows both shot about 179 to 180 fps on Ken's machine with 10 gpp arrows.

Daniel drawing his bow...
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My bow...
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You can see in the braced and drawn photos that there is extra reflex in the tips. The WTT video also showed that my bow especially had vibration. I think that was mostly due to the heavy tips. Daniel's bow had a straight width taper and mine had a parabolic (curved taper). Mine had vibration...hmmm? So, I think the first thing that I'm going to do in my R&D process is to try some experiments with this existing bow design and see if I can speed it up and reduce the vibration in the power stroke. I have the first bow that came off of this form that I can do my first testing on. It came out too heavy in weight plus it had some delamming issues in the riser. First, I repaired the riser by injecting some super glue into the cracks between the lams and clamping it all back together. Then I drilled and screwed a bunch of long screws into it. So far, it is holding together. Next, I ground the limbs into a straight taper from 1-3/8" at the fades to 1/4" tips with back nocks. Last night, I shaped the handle and refined the tips a bit. This glue up also had a tillering problem in that the lower limb is 5/8" too strong. I must have mis-matched the glass during glue up or made a grinding error making the lams. So, I also sanded the back and belly glass a bit on the lower limb and will work on that more tonight. I'll show some pics later. What I hope to discover by testing this particular bow is how much narrowing the limbs affects the brace profile, full draw profile and finished draw weight. Then I can make adjustments in the lay up on the next bow. I believe that my goal for the profile is to have some visible reflex at brace and straight tips or just a bit of visible reflex at full draw. I can already tell that the super narrowing is letting some of the reflex open up, but once I get the tiller balanced, I'll be able to see it better on the tree.

Jim
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Re: My R&D build up for WWT3

Postby Kirkll » Thu Oct 16, 2008 9:47 am

this is pretty cool Jim....7 card stud....face up huh?
Maybe i can share in the tip wedge department...i'll be doing some experimenting along those lines.....Kirk
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Re: My R&D build up for WWT3

Postby Hornseeker » Thu Oct 16, 2008 12:40 pm

The length and thickness of your tip wedge will obviously have a big influence on the shape at brace and full draw. You have enough reflex in the end of that thing that it just "may" be possible you dont even need a tip wedge... however...maybe 2 1/2 -3 inches below the grooves...and dang thin...like 3/32 at the butt end... I have found recently that too much reflex at brace or draw is not making my bows any faster... not slowing them down much either, but if its not necessary I'm not going to keep it! Just makes things harder on the bow I think.
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Re: My R&D build up for WWT3

Postby jwillis » Thu Oct 16, 2008 1:16 pm

Hornseeker wrote:The length and thickness of your tip wedge will obviously have a big influence on the shape at brace and full draw. You have enough reflex in the end of that thing that it just "may" be possible you dont even need a tip wedge... however...maybe 2 1/2 -3 inches below the grooves...and dang thin...like 3/32 at the butt end... I have found recently that too much reflex at brace or draw is not making my bows any faster... not slowing them down much either, but if its not necessary I'm not going to keep it! Just makes things harder on the bow I think.

Thanks for the good advice. You may be right that it doesn't need a wedge and that's why I'm narrowing this test bow to see what it does. No wedge might be optimal for this particular layup. This bow has .002" per inch taper and the next question might be, "should I try more taper like Ken and TJ in order to lighten the tips?" In that case, I'm thinking it might need a bit of a wedge like you are suggesting. In fact, I think that will be my next layup (.004 taper with a tip wedge) just to see what happens with the taper Ken suggested. It's hard to argue with someone who just built a 202 fps bow...lol. Jim
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Re: My R&D build up for WTT3

Postby tjdeerslayer37 » Thu Oct 16, 2008 6:48 pm

jim, can you snap a pic of some back nocks for me? id love to see em.

very cool design, i love the profile even if it is a little too much for optimum performance. :D
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Re: My R&D build up for WTT3

Postby Hornseeker » Thu Oct 16, 2008 8:43 pm

Tj...back nocks are simply nocks that are NOT filed into the side of the bow... only the back... therefore you can narrow the tips WAY down cause you dont have to leave space to file nocks in... Get it?? I may have to try it...never have yet...
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Re: My R&D build up for WTT3

Postby Kirkll » Thu Oct 16, 2008 10:26 pm

Hornseeker wrote:Tj...back nocks are simply nocks that are NOT filed into the side of the bow... only the back... therefore you can narrow the tips WAY down cause you dont have to leave space to file nocks in... Get it?? I may have to try it...never have yet...


sounds good in theory, but how do you keep the string from coming off at the emd of the power stroke? smaller loops? or what?
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Re: My R&D build up for WTT3

Postby Hornseeker » Fri Oct 17, 2008 6:54 am

The nock overlay is thick enough that the nock groove is filed deep enough that it works... BBP did his that way and they worked fine... They work.....

So TJ...do you see that? THe string just slides along the side of the limb and is held in place on the back!

E
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Re: My R&D build up for WTT3

Postby jwillis » Fri Oct 17, 2008 7:59 am

I'll get some pics up soon and show the back nocks. I'm still sanding the glass on this thing trying to get the tiller balanced. It is way off. Jim
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Re: My R&D build up for WTT3

Postby jwillis » Sat Nov 01, 2008 7:15 pm

This is blurry, but it shows that really narrowing the limbs has opened up the reflex in the tips some. They don't look quite as curved as the wider profile. I'm going to guess that more taper will open them up even more, so I'm going to lay up another bow on this form with .002 more taper and see what that does.
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There is still a fair amount of reflex in the braced profile. If you look closely at this photo, you can also tell that I cut about 3/4" off of the lower limb to do some balance testing on my tillering tree. That also added five pounds. One interesting thing about this bow is the tiller is really sensitive. At one point, I had it at even tiller, but after rough sanding it is 3/8" positive now. It shouldn't take much more sanding to even it up again. Cutting the lower limb shorter put the low point of the grip at the geographical center of the bow. My tillering tree is rounded at the top so the bow can pivot and show balance. With the pulling point on the string about where my middle finger will be, it balances best with even to 1/8" negative tiller. I was hoping that the balance testing would prove or disprove some of the Torges stuff I've been reading.
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This shows the narrow tips and back nocks. These tips seem really strong and stable--not delicate at all.
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This bow has .002 thickness taper and a straight width taper from fades to 5/16" wide tips.
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It feels pretty snappy with the narrow tips. I still don't have a chrono yet, but hope to order one this month. When I get one, I'll test this bow and the original profile I made with this form to compare the performance. Surely by the next bow off the form, I can get the chrono.
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