Author Topic: Achieving Target Draw Weight?  (Read 5612 times)

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Offline Ippus

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Achieving Target Draw Weight?
« on: September 02, 2015, 02:15:06 pm »
I'm really just getting started - looking forward to selecting my first staves in the next week or two, probably Siberian elm, but something I haven't quite understood yet from my reading is this:

How do you get to a target draw weight?

I mean, does the wood kind of decide for you? Does stave selection have a lot to do with it, or is it pretty negotiable (downward at least) in the tillering phase?
If I overshoot with a self-bow, particularly ELB, can I just continue removing wood until it's down to where it's as light as I want it? In that case, is it better to try removing width? If I remove thickness, am I restricted to removing wood mostly from the belly, or is that going to make it collapse under compression - do I dare mess with the back at all?
"There is nothing quite so gentle, deep, and irrational as our running — and nothing quite so savage and so wild.” Bernd Heinrich

Offline bradsmith2010

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Re: Achieving Target Draw Weight?
« Reply #1 on: September 02, 2015, 02:26:56 pm »
well, its a complicated question,, but to over simplify ,, yes remove wood till desired weight is achieved,,there are fairly standard processes to tiller the bow without over straining the bow, and there are different opinions on where to remove wood for best results,, it really depends on the design,,start with something simple and ask questions and learn as you go,, reading will only get you so far,, hands on is the only way :)

Offline Ippus

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Re: Achieving Target Draw Weight?
« Reply #2 on: September 02, 2015, 02:34:25 pm »
Thanks! I'm pretty sure my wife and several friends think I've gone off the deep end at this point, but I'll show them. I'll show them all! Muahahahaaah! >:D

Seriously, though. Really excited to get started! Just got the notification that my local library got TBB 1 in (they had the other volumes, but not the first!), and work seems exceptionally long today.
"There is nothing quite so gentle, deep, and irrational as our running — and nothing quite so savage and so wild.” Bernd Heinrich

Offline Del the cat

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    • Derek Hutchison Native Wood Self Bows
Re: Achieving Target Draw Weight?
« Reply #3 on: September 02, 2015, 02:54:37 pm »
Follow some of the builds on my blog.
Bottom line... always pull to your target draw weight (unless you see the tiller isn't right as you are applying weight, in which case you stop and remove a litte wood to correct the tiller), that way you'll either end up at your target or with a pile of broken wood.
It is nonsense to think Ooooh I want a 50# bow, but I don't want to overstrain the wood so I'll go gentle and pull it to 30#
If you pull to 30# you'll end up with a 30# bow
Del
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Offline Pat B

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Re: Achieving Target Draw Weight?
« Reply #4 on: September 02, 2015, 02:55:24 pm »
What I do while tillering so I get to the weight I want is to check tiller to the max weight. So if I want a 50# bow at 26" I make my long string pull to 50# and check to be sure everything is good them remove more wood, pull to 50# and check tiller, and so on. I get off the long string and to low brace as soon as possible, usually when I get about 8" of tip movement.
 If you come in over, remove wood until you get the weight you want. Remember to exercise the wood often as you tiller.
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Del the cat

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Re: Achieving Target Draw Weight?
« Reply #5 on: September 02, 2015, 03:03:32 pm »
What I do while tillering so I get to the weight I want is to check tiller to the max weight. So if I want a 50# bow at 26" I make my long string pull to 50# and check to be sure everything is good them remove more wood, pull to 50# and check tiller, and so on. I get off the long string and to low brace as soon as possible, usually when I get about 8" of tip movement.
 If you come in over, remove wood until you get the weight you want. Remember to exercise the wood often as you tiller.
+1
Doing it like this you'll get results that go like this:-
50# at 6" long string (and by long string, we mean only just long enough to get onto the bow)
50# at 10" long string
50# at 16" long string
50# at  20" braced
50# at 22" braced
50# at 24" braced
50# at 26" target weight at target drawlength.

If you keep pulling 50# you end up at 50#!

The main adjustments of tiller are in the first 4 readings, after that it's very fine tuning and removing wood v carefully to ease it back.
If you are not heartilly sick of putting it up and down on the tiller and exercising it, then you aren't doing it enough! >:D ;)
The hard thing is getting your eye in to seeing problems before they are too obvious... also knowing how much wood to remove to achieve the desired result.
The whole process is one of successive approximation and prevention rather than cure.
When in doubt, stop, take pictures and video, look at how the bow actually flexes, not just the static curves.
Del
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Offline Eric Krewson

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Re: Achieving Target Draw Weight?
« Reply #6 on: September 02, 2015, 03:26:38 pm »
First make a tillering gizmo, it will put you over target weight so you have a lot of room to work down to your target weight.

Get your limbs bending evenly with no stiff or weak spots.  When you get to this stage you take full length scrapes on each limb 10 at a time. Somewhere between ten and twenty depending on the wood will drop your bow a pound or so. Do a couple of scrape sessions, check poundage, check the tiller with your gizmo and correct any stiff or weak spots that show up and repeat until you are at your target weight.

Offline DC

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Re: Achieving Target Draw Weight?
« Reply #7 on: September 02, 2015, 04:13:01 pm »
When I started I went back about 2 or 3 years in the "Bows" section and read every post. Pay attention to all the full draw pictures and especially the "tiller check" posts. Try to get the shape of a bow burned into your retina.

Offline jeffp51

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Re: Achieving Target Draw Weight?
« Reply #8 on: September 02, 2015, 11:49:07 pm »
Thanks! I'm pretty sure my wife and several friends think I've gone off the deep end at this point, but I'll show them. I'll show them all! Muahahahaaah! >:D


If you are reading and posting on this site, there is a good chance you are off the deep end like the rest of us. My wife knew I had lost it the day I came home from the game processor with six elk legs and began stripping sinew. Enjoy the addiction. Tell your wife it is safer than drugs and cheaper than a girlfriend.

Offline lebhuntfish

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Re: Achieving Target Draw Weight?
« Reply #9 on: September 03, 2015, 02:16:29 am »
Thanks! I'm pretty sure my wife and several friends think I've gone off the deep end at this point, but I'll show them. I'll show them all! Muahahahaaah! >:D


If you are reading and posting on this site, there is a good chance you are off the deep end like the rest of us. My wife knew I had lost it the day I came home from the game processor with six elk legs and began stripping sinew. Enjoy the addiction. Tell your wife it is safer than drugs and cheaper than a girlfriend.

Amen Jeff I had a good laugh at that one. My wife said, when I started my 3rd bow, "exactly how many bows do you need?" Now she comes out and visits with me while I'm working and let's me know when it's time to eat!

Ippus, you have received a lot of good info so far.  Also go back a few pages in "bows" there was some great videos posted recently. Then check out YouTube. Look for, boarrior bows and Clay hays. Both are really good information guys. They have build a longs and how to's. Get the Traditional Bowyer's Bible's volume 1 and 2. Read them. Take pictures of your progress and post them here and let some of the best Bowyer's in the world walk you through your builds. Don't be afraid to ask questions. The only dumb question is the one you don't ask.
Oh and welcome to the obsession! Patrick
Once an Eagle Scout, always an Eagle Scout!

Missouri, where all the best wood is! Well maybe not the straightest!

Building a bow has been the most rewarding, peaceful, and frustrating things I have ever made with my own two hands!

Offline Del the cat

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Re: Achieving Target Draw Weight?
« Reply #10 on: September 03, 2015, 03:03:07 am »

My wife said... "exactly how many bows do you need?"

Same number as shoes and handbags? >:D
Del
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Offline lebhuntfish

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Re: Achieving Target Draw Weight?
« Reply #11 on: September 03, 2015, 09:24:45 am »

My wife said... "exactly how many bows do you need?"

Same number as shoes and handbags? >:D
Del

At least the hand bag part Del! Patrick
Once an Eagle Scout, always an Eagle Scout!

Missouri, where all the best wood is! Well maybe not the straightest!

Building a bow has been the most rewarding, peaceful, and frustrating things I have ever made with my own two hands!

Offline snowplow

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Re: Achieving Target Draw Weight?
« Reply #12 on: September 03, 2015, 02:46:20 pm »
Hey guys, not trying to hijack, but hopefully this continues this great conversation-

When tillering at your desired weight, what is the method you use to pull, see the scale, and step back to view and work the bow? Seems like a lot to manage and I cant picture it.

Offline Pat B

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Re: Achieving Target Draw Weight?
« Reply #13 on: September 03, 2015, 03:02:01 pm »
I'm using my tiller tree and a digital scale. When you hit the weight and let it down it shows the max weight it went to.
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Del the cat

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    • Derek Hutchison Native Wood Self Bows
Re: Achieving Target Draw Weight?
« Reply #14 on: September 03, 2015, 04:29:02 pm »
Hey guys, not trying to hijack, but hopefully this continues this great conversation-

When tillering at your desired weight, what is the method you use to pull, see the scale, and step back to view and work the bow? Seems like a lot to manage and I cant picture it.
Yeah it's a lot to do, 'cos you are looking at the bow, the weight and the length.
Which is why we all occasionally screw up by pulling too hard or too far or being too busy looking at the draw length and missing the hinge starting to bend... >:(
But if you have the rope from the scale going down to a pulley near the floor, you can stand back six foot and pull and watch evrything at once.
I can't get back very far in my workshop, so I have a camera mount on the wall opposite the tiller tree. That way I can video it and the watch at my leisure.
Like this  :)
https://youtu.be/Yni817qcUDs
Del
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