Basic tillering / weight question...

[Lee Slikkers]

OK, so here is my question on Tillering to reach a specific draw weight.  For an example I currently have an Osage that is drawing #48 @ 16"

I've read that a bow will typically add 2lbs of weight for every inch of additional draw.  So with that theory in mind, if I knew I wanted to hit #56 @ 26" I could work my way back and that would indicate that I can reduce this bow to #37-ish @ my current 16".  If I am way off base or totally lost I'd love to hear any help or opinions on the best way to hit close to my target weight.  I really don't want to come in on the light side.

Many thanks folks!

[PEARL DRUMS]

Get the tiller perfect at 20-30 #'s max. Once you have the tiller correct you can pull the bow until you hit your desired draw weight. Remove wood evenly (or not) until you hit "x" pounds @ "x" inches with proper bend. Math never seems to work well with wood..............not with me anyway. Hopefully your tiller is dead nutz already if your pulling 48# 's , regardless of inches pulled.

[Lee Slikkers]

Here is where I am at...not "dead nutz" but there is a wavy hump/wind check and a knot that kind of messes with the bend in the left/lower limb.



Thoughts?

[blackhawk]

Im confused 

Why is the string nocked 3-4" from the end on the left limb. If its extra why not cut it off? Is that where your string is supposed to be? Please explain


Oh and what's sitting in the garbage can?   

[Lee Slikkers]

That is just an extra 1"+ that haven't taken the time to cut off...bothered me too for a while but I guess I got used to it 

That isn't really my trash, its a can I sweep all my shaving into (good for mixing in parafin for fire starters) and I simply had traded out the ERC build off the tree and layed it there...she's still alive 

[crooketarrow]

   Build a tillering tree with a scale this way you hit your draw weight with the draw lenth perfect every time. You can't go by the 2 pound thing and hit it right. All wood is different through a knot in there that really puts a screw into it. I'd build a tree.

[blackhawk]

Oh ok...wheeeeeeew. u had me nervous there

That extra length is messing with my eyes.....cut it off.

Tiller looks close but I don't know what the unbraced looks like. Id say a tad more near the fades. And yes get that wood moving under that big purty knot a lil bit. And maybe a wee bit stiff out towards tips but that's ok too cus then you can really narrow them and lose mass and make a sweeter shooting bow.

[Lee Slikkers]

Ok, thanks for the feedback guys.

Chris, the area at the knot has me a bit nervous about removing much more wood there but I will see where it takes me.  Good thought on slimming the limbs towards the tips too...it is fairly narrow now but I could stand to loose a touch more.

[Cameroo]

Here's my 2 cents - I agree that it looks like it should be bending a little earlier on the left limb.  I'd take a few scrapes off just to the left of that knot. Or maybe it's just the knot messin with my eyes.  If I was you I'd be careful not to develop hinges where the red is.  I'd just scrape where the green circles are until you get a nice arc, then proceed with full-limb scrapes.  I wouldn't be pulling over 25 lbs till that's sorted out. You don't want excessive set, especially at the fades. The right limb looks perfect to me, once you get those slight hinges worked out of the left limb, just keep taking wood off evenly across both limbs.

Or maybe it's just the picture and the left limb is fine too

[Del the cat]

No no no no no! Don't work on the 2 pounds per inch thing .
It's just a useful guide when you are very near draw or you are wondering what will happen if you pull your 40#@28" bow back to 31" (assuming it doesn't goe BANG)
I you want to hit 56# at 26 then you have to hit 56 @ 16" first, then 56 @ 17", then 56@18" etc whilst trying to get the tiller perfect  and maintain it as you slowly get it back all the way to 56 at about 24" then you stop and finish it and shoot it and fancy it up and you'll probably find you've lost a couple of pounds and gained a couple of inches and all of a sudden you are spot on your target weight. Do it like that and you have some chance of getting there.

If you work it out to say 37 @ 17 even with perfect tiller and then pull it back to 28, you'll proabably find the tiller is a mile out.
If you take a finished bow of 56@28 and measure it at 17... it may well be 37 or whatever...but this is hindsight, you can't do it the other way round (IMO)
Del

[Lee Slikkers]

Thanks Guys, both of those replies helped emensly!  I've got the hinge warning marked now 

Del, not sure where or why I was headed in that direction with my "new" math and I've probably read what you described in various places but how you explained just really clicked for me so thanks a ton for taking the time to do that...very much appreciated!

[johnston]

Lee it looks pretty close to me but I can see what Cameroo is saying with the red marks. These guys are good.

Lane

[Lee Slikkers]

Thanks Lane, yup...these guys and this site ROCKS, period!  Headed down to the "dungeon" to see if I can't correct the issues.  Hopefully I'll have some additional pics of the progress to add up here later tonight.

[okie64]

Looks pretty good Lee, but I would try to get it bending a little closer to that knot. Del explained it perfect on the tillering.

[DCM4]

While I agree the 2# per inch projection can get you into trouble I disagree on the remedy.  I find if I tiller a bow to max draw weight all the way up the draw lenght, and especially if I "work" the adjustments in as conventional wisdom suggests by pulling an arbitrary number of times at each station, each inch of draw say as I tiller it out, I finish with a bow drawing the poundage I wanted and making cast like a bow 5# or more lighter.  IMHO you are better served by drawing the bow as little as possible in general, and only enough to find flaw with the tiller.  Then proceed to projected draw weight at a particular lenght, eg. not the full draw weight as you continue to adjust tiller.  But you do have to allow an extra 5#, on average say for a 50# to 60# bow at 28", of lost draw weight from set. So if I want a 50# finished bow, I project back 2#/" from 55# for my max weight at each inch of draw.  The set will usually come when you get to about 22" to 24" of draw, again assuming a typical design, moisture control, all the normal stuff.  I try to get my tiller dead nuts before I get to this point, to try to minimize the lost draw weight but more importantly the lost cast.  Maybe not the best advice for a fellar just trying to get his first good bow, or having just made a few.  But after you've made a dozen good shooters and you want more, that last little bit of performance, it's something that will open your eyes when you get it right.

To put it another way, if it were possible to cut a bow out to final dimensions, perfect tiller having never drawn the bow, then when you first work the bow it may drop a few pounds of draw weight to set but it will make cast like a bow 5# or more heavier.

When I first started out, after a couple three years and as many dozen bows, I was amazed at some of the chrono numbers I saw posted for bows very similar to mine.  Eventually I figured this out.  I think most bowyers follow the same path, employ the same technique without realizing, simply by developing a better intuition for tillering from experience.  This having the net effect of not needing to draw the bow as many times, or to as high a draw weight/strain level to get it "right."