Bow Physics revisited.....Bow Finished!

[styksnstryngs]

I don't know how you grip your bow, but for me, the throat of the grip is where the majority of the pressure is. And in regards to Olympic bows, the top and bottom limbs are the same length.

[Roy from Pa]

Yup, it depends on the hand grip also.

Low, medium, or a high grip and grip shape determines how your trees cradle is setup.

[hightop_hunter]

Hmm iv always done the tiller then did the grip. But i like this I think ill give it a try on the bow I'm currently working on. are there any books or literature you can suggest for tillering a glass bow. ?

Thanks Roy  for the tips

[joebuck]

In Jim Thorne article on his web page. He achieved even tiller out to 20" with tiller board grip dead center and rope dead center regardless of what ever style of shooting..............Then final tillering, he adjusted tiller board grip to center of grip pressure to however the archer holds the bow,(low, med, high) and rope pull on string  to center of archer finger pull ( depends on style he used, three finger or split) and tiller the bow out to his draw length. He stated at his draw length he like limbs even tiller for three under and split was a 1/8 to 1/4

[joebuck]

My original question was how to build a bow favorable for this "crawl" epidemic i pick up!!!  We have bounced around ideas and suggestions on bow design.... thanks for the input and i have learned a couple things.......................so................my new bow project is getting close to rubber meeting the road ( riser glued up, lams are ground, etc.) ..............
As of last night of shooting my current bow i have set up....with a light smell of Silver patron present....here are my dedutions

1. My current 58" curve.....just doesnt like a "crawl" set up...Arrows fly erractic.
2. The high string angle on the nock really pushes down on back of  arrow at release to cause a low nock at impact.
3. Crawl it seems is for longer bows 64" 68" ( less string angle)
4. All my deciphering on where the balance center vs true center of the riser vs low grip..yada yada....doesnt matter  my bow is too short. No tiller adjustment will lesson the string angle of a 52" string braced to 29.5"
5. Split finger still casts the prettiest arrow i can throw out of any bow... But Been too long on the dark side to go back. Three under it is
6. my future/  make this current project as usual design as my 58" but 2" longer on limbs

[stickmonkey]

2 “ longer limbs will only  change a few degrees of string angle however if you designing a recurve or a static tip then you can time the tips to remain at 88-90 degrees for the best string angles possible for a particular bow. You will do that by tillering/timming the limbs to do so at draw.

Recurves are not as stable as deep core hybrid or longbows so using an existing bow that was not tillered/timed for how your shooting it adds to the instability of the limb causing erratic flight and oscillation. I have a 56” extreme hybrid that has a higher shelf , 2.5”, than my normal 1”. I simply tillered the limbs to where I am drawing from and it shoots just like the others set at neutral.

If you want a recurve you may consider a deep core recurve limb or an extreme hybrid but I think as long as you time the limbs from where your drawing it on the string you will be fine.

[joebuck]

Stick ...on your hybrid.......what is your shooting style?  Raising the shelf ,only increases my string angle. I shoot a 1/2" shelf now built up with JB Weld under leather

Nuts and bolts of my deductions...the Crawl is for longer bows, period..

I only went to the crawl because i love the solid anchor in corner of my mouth yet my arrow is right under my eye like a shotgun...so deadly a system at 20 and in.. it's like pointing a shotgun at deer at 18 yards..

i have an unlimited supply of grizzly sticks    well almost......going to try different spines

[stickmonkey]

The customer wanted 3 under for that hybrid.

The shape of the shooter face plays an important role in choosing a style and anchor that’s often overlooked. Three under puts the nock under my dominat eye but I have to push hard and deeply into the corner of my mouth to get the same with split finger. When I started 30 years ago I shot split finger as it kept the arrow inline under my dominant eye but as I matured and gained weight in my face my anchor had to change to keep the same alignment.

The crawl is nothing new and the bows length doesn’t matter if it’s tillered to where your drawing on the string. Yes The higher you go on the string the steeper the angle but that angle doesn’t cause an torsional instability to be induced reguardless of the bows length. The erratic light is a product of the limbs not being timed to the where your drawing on the string.

Time to build it and see.

[joebuck]

Well............bow is finished except for spraying and shot a hundred arrows out of it tunning to a bareshaft. Very very pleased with accuracy. It's Bareshaft grouping a golf ball size group at 18 yards 320 TDT  New Grizzly Sticks Victory with a 175pt.  ....Very pleased with my handle and torque is diminished. Fooled with side plate thickness by adding leather to get the shaft a slight fade at point with string lined up dead center. Bow tillered out to my sweet spot at 29" . Came out at 50# 29 which feels like a dream for a guy thats 56 and been shooting 68# for 25 plus years.  feel like i am cheating now.
Tillering for the Fixed Crawl...to the nuts and bolts.......I tillered the bow by placing the fulgram of handle on pulley board wall exactly where pressure is for my heel/base thumb. Then i hooked up pull down hook on string exactly where my middle finger ( center) of my 3 under grip. I then tillered the limbs at 30" to Even tiller on the wall graph. Interesting point here is .........this bow upper limb is 1/8" negative tiller at brace.!   Since it is shooting like a lazer with bareshafts...........I am cool with a slightly stronger upper limb at brace.   not sure of the physics or what but second set of limbs will be in works soon to get more data.


Right Now for my Data and stats to build a bow for fixed crawl
60" T/D recurve ( 27 " limbs and 16" riser)
50# at 29"
1/8" negative tiller at brace upper
Even tiller at 30"
590 gr arrow 171fps at 29"at 50#
500 gr arrow at 50# at 29"  190fps at 10gr/per pound