Primitive Archer
Main Discussion Area => Bows => Topic started by: cailean on March 07, 2010, 12:32:43 pm
-
Hey Folks...i have a problem i'm hoping someone here can shed some light on for me.....i'v made a few bows now and seem to have the same trouble with ALL of them....i use split staves and when i tiller the bow the limbs get a propeller twist going in opposite directions in both of them and i can't see it being the wood EVERY TIME... so i'm doing something wrong....i've made bows from Birch, Shag-Bark and Smooth-Bark Hickory, HHB, and Red Cherry.... if i try to tiller the twist out the draw-weight of the bow makes it useless for anything but a small child and the twist is STILL THERE.... i have no idea what i'm doing wrong but it MUST be me cuz it can't be the wood EVERY TIME...any insight you have will be greatly appreciated...thanks for listening.
Cailean
-
Cailean,
I dont make split stave bows but it is still possible for ME to induce propeller twist especially in the wider limbed types like Mollegabets or even the little Ottawas. I got around this by doing the following.....when I have the stick to low brace I sight down the backs of both limbs and if I see a "high" (too strong) edge....I correct that before I get to the curve / weight tillering. Then as the bows starts to come back I do the same thing every time.....check the back for twist....then tiller for curve and weight.
This may not be of use to your methods but it works for me....if it helps any
half eye
-
Thanks Half-Eye...i do check the back and work on the "high" side to try and get the twist out but it doesn't seem to help any cuz the twist remains and never seems to change or lessen...one bow i made from Birch is 72" long ntn and only weighs 20lbs at 30" of draw i took so much off trying to get the twist out.
-
Feel the thickness of the limbs from side to side. Sounds like you are making different thickness from one side to the other. If you have a vise attached to your work bench, generally the side of the bow closest to the work bench will be thicker because the access to that side is less accessible. If you use your thumb and fore finger to feel the thickness of the limb you should be able to feel the difference. Your feel is generally more accurate than trying to see a difference. That thickness difference will make the limb twist as the bow is drawn.
-
I second what Pat says. I have a tendency to remove more wood from one side of the limb than that other (something about the angle of my vice and how I hold my tools). But I am aware of it and am constantly checking both sides of the limbs to make sure wood removal is even. It seems like you may have to do the same.
-
Sounds like myabe you re removing thickness unevenly across the limbs, or in an attempt to correct the twist actually making it worse by removing wood from the wrong side (it's easy to do).
Maybe I'll draw a picture later...
Del
-
I have to concur...this was a big problem for Me when I started out....with a Vise mounted on a Table or Bench top...you will always be put in a precarious position on the side closest the Bench/Table....so if possible use calipers....or your fingers and thumb.... ::)....or do like my Brother did....mount your Vise on a post anchored to the Garage Floor ...so you have 360 degrees of access.....JMO
-
Dunno if this, not very good pic will help.
(http://i411.photobucket.com/albums/pp195/Del_the_Cat/limb.jpg)
With flat section limbs it can help if you hold a bit of arrow shaft across the back and belly of the limb (a rubber band will hold them in place) they should be parallel, the arrows will quickly show any error as the added length will magnify it.
Del
-
Yup. Been there. Let's se you are right handled. It's natural to to remove more wood from the right side. Then you flip it around and remove more wood from the right side. There's your propellor twist. Do as Pat says run your hand over the limb and visually check for even wood removal. Jawge
-
Yep, we're all creatures of habit. You make one limb uneven and turn the bow around to do the other limb and you'll do exactly the same thing again. You come away with twisted limbs everytime. At think at some point, we've all made this mistake. Now that you're aware of what's causing your problems you'll be more conscious of the fact and try to prevent it. Good luck..........ART
-
I think I've gotten lucky and have dodged this bullet by not having a workbench or a vise.
I do my bows out on my deck. When it comes time to remove wood for tillering, I lightly shaded the whole area with a pencil.
Then I set the bow on my deck railing, with the tip bumping into my waist, just under my belt.
This lets me draw my surform smoothly back towards me. It stays pretty horizontal the whole time, and by doing that, and evenly removing the pencil lead I put on, it seems to come out pretty flat.
I'm also pretty obsessive about sighting down the bow from both ends before I do anything.
best of luck!
-
Another tip, if you strap a bit of arrow shaft across the limb you are NOT working on, it will provide a nice reference for the limb you are working on.
Or one at each end of each limb, heck ...jus' strap e'm all the way down both limbs, that'll show where the twist is >:D
That's one advantage of an English style lonbow...there are no staight edges to worry about ;D
Del
-
are you using pencil marks when you are tillering,,,mark up the limb well and just remove the pencil mark,, controls the amound of wood to be removed does not matter right or left handed,, mike
-
"I think I've gotten lucky and have dodged this bullet by not having a workbench or a vise."
You still can favor one side over the other. Usually it's the side closest to you. Jawge
-
thanks so much for all the input folks....i'll try as you all say and use my thumb and finger to check for equal thickness... and hope for the best...lol...and yes my vise is mounted as you all say...{the post idea is clever}....thanks again very much, i'm off to try it out.
cailean