How fast will weight come off during tillering? (aka my new bow is done!)

[Diligence]

Howdy folks....so I'm hopeful that I will get some free time in the next while to continue tackling this new adventure of bowyery.  (just had twin daughters and my 2.5 yr old son seems to take up most of my time   )

Anyway, I have a stave of chokecherry that has developed a couple of quirks.

It was greenish when I started to work it, and took it into long string tiller while green.  It has some set, no big deal, I can live with that as this is my first bow.

I now have let it dry for a month or so inside my home and it's much drier.  I have completed a low brace and it's pulling 48# at 20inches right now.  It's about 58" ntn and has a total of 11 knots in it.  I'm attempting a bend thru handle design.  The belly has some crown. 

It's twisting now too as it has dried a bit more.

Jawge gave me some good advice about making sure I have the same thickness - to prevent twist.  Also, how I can adjust my nocks to gain some string alignment thru handle....and I will incorporate that advice.

The bow, when viewed from the end, shows the belly at each nock to be in the same plane, but moving towards the handle, the bow twists (propellers) a bit so that if I hold the bow so that the belly faces me, the string sits outside the bow at least 3/4" if not more.

I've realized that I have made the thickness of the bow different thru the handle (ie the width is constant, but the thickness varies from the left to the right side of handle).  I think this may be contributing to the twist.  Also, the knots are closer to the left side of the bow than the right.

My question is this:

If I attempt to correct my thickness issue, (ie constant thickness from left to right bow sides) how fast will my weight drop?  I think I have to remove about most of the belly crown, and a bit more to create an even thickness. 

And, if I do this thickness correction, will it be probable that the twist will be reduced?

I will attempt to post a couple of photos of unbraced, braced and partial draw photos....I am aware of a hinge in right 1/3 adjacent to handle...and am avoiding it.

Here's a link to a photo share program...couldn't directly upload...techno-peasant!

http://photoshare.shaw.ca/view/3670323764-1237606348-47095/
Cheers,
D

[Jmilbrandt]

I don't really understand your question completely. Are you trying to get the string to track closer to center by changing the thickness of the limbs to twist them more towards center? I haven't ever been able to get the string to move very much by doing that and never the 3/4 of an inch you are showing. Also you said it was 48#s so I'm guessing you don't really want to lower the weight much more so I would say not to remove wood to correct the problem. By the time you reduced the wood enough to straighten the twist you would be at a very low weight. I would probably attempt to heat bend the handle to bring the tips in line. The propeller twist isn't a big issue and doesn't hurt performance so I wouldn't worry about it just make the ends of the bow line up with the center of the handle. Once you have the bow straightened let it sit for a while to regain proper moisture content then continue tillering. It's looking good so far.

[George Tsoukalas]

So the handle will be the widest part of the bow? Jawge

[George Tsoukalas]

How much prop twist do you have? Staves are less likely to twist if they are  close to bow dimensions. So you did everything right in that regard. YO can floor tiller a green stave  a little bit. Like Jmil said they rarely need correcting. Jawge

[Diligence]

My apologies, I reread my last post and it is rather cryptic.  I'll try to be clearer.

I think I have these issues:

1. When in low brace and low draw, the string sits outside the handle at least 3/4" inch, or more.

2. when I hold the bow in my left hand so that the handle belly faces directly towards me, the belly at the nocks face back over my right shoulder about 25 degrees. (this is the twist that I called propeller)

3. I've shaped the bow so that the left side of bow is a bit thicker than the right side of bow, and this difference is consistent from middle third thru to middle third on both limbs and thru the handle.  So when the string sits outside the handle, it is sitting outside the thicker side of the bow.  The thicker side is also where the knots are located.

4. I'd like to have about a 45# draw bow, but I would be happy with 40# (or maybe even 35#) since this is my first.

5.  I think I attempted a pretty tough stave, since it has all these knots, and existing kinks and bends, but I'm game to see what I can do.

Jawge, The handle is the widest and thickest part of the bow.  Even taper in thickness and width out to the nocks.

Jmilbrant - yes, since I have some wood to remove on the left side of bow, I thought that might allow the bow to twist less. (but the bow is deflecting towards the thick side and away from the thin side)...which I think is the opposite of how it's supposed to be.

Regarding my tiller so far, I believe that I need to get more bend thru the handle, and I am aware of at least one spot where a hinge is forming.  I plan to tiller to full shape, then cut my tips and shape nocks to reduce some tip mass.

I hope that clears up what I was trying to tell you.

My question is related to how I should proceed with getting the string back in line with the handle.  I know steaming and bending is an option, cutting deeper nocks on one side is an option, and perhaps removing some of the thicker wood from one side is an option.

Any other ideas?  any preferences?

thanks in advance!

D

[Jmilbrandt]

If you are close to your final weight I would not attempt to reduce the twist by removing wood. Weight comes off very quickly during final tillering and if your not careful you will come out under weight. I believe that the string will move towards the thicker side of the limb but it's been so long since I did it last I'm not sure. Believe me though taking off wood to correct a twist or move the string towards the center only works if the amount you want to move it is very small. I would not recommend it for 3/4 of an inch. I would first try to move the string over by narrowing your nocks on one side, that is if you left them wide enough. I couldn't really tell from your photos how wide they were but I generally make mine about 1/2 inch even on higher weight bows. If that doesn't work try steam bending it. None of the problems you have there are that major just keep at it I'm sure you'll get it.

[Jesse]

If its bending towards the thicker side then I would say you need to heat it and bend it to line up the tips. I have had bows that were farther than that off the handle and a little scraping on the other side will bring it right back easy but with this one going towards the thick side I think you have other issues.

[Jmilbrandt]

Ok I just checked and I was wrong the limb should twist towards the thinner side.

[George Tsoukalas]

Jmil, then you caused the twist by uneven wood removal which is easy to do since we favor one side as we remove wood. At least I do. Constant visual inspection and running your hands on the limbs as you tiller will help pick this up. I'd either live with it or slowly remove wood from the strong side to fix it. Yes, and it's been there done that. MY early bows often had strings off the handle because of that reason. They shot fine. I don't think heat will be a lasting fix. Jawge

[Diligence]

Thanks to all for your responses.

I think will try to remove a bit more wood from the thicker handle area. I need to get that area bending more anyway....will see what happens....then, I will cut my nocks to adjust string position....and finally, if still needed, I will try some heat.

All in all, this has been fun so far.  I can hardly wait to finish this chokecherry bow so I can get to my 2 ash staves, and my well dried birch stave with natural tip recurves

cheers.
D

[Jmilbrandt]

I use a pair of calipers to check the limbs for uneven thickness throughout the tillering process I realise it is easy to mess that up. I don't think that was my problem I think it was the natural twist the staves had when split that caused my twist.

[Pat B]

If it were a natural twist it would be apparent when the bow is unbraced. With it showing up only when braced tells me there is something uneven about the limb. Even though your limbs may not be different thicknesses from side to side, one side is stronger than the other. You are dealing with a natural material with many variables.
  With a glass bow calipers may come in handy but in my opinion, when working with wood bows you have to work with the irregularities of the wood. It's more of an art than a science.
   Even though I use my fingers as calipers(by feel) I also study the bend of the limbs. I study whether they twist, if there is a possible hinge or stiff spot and the resistance of each limb and by comparing then individually and together.

[Jmilbrandt]

Pat I agree completely. You never know what your materials will do when they are natural. I usually use the calipers for thickness when roughing out the bow and then up until final tillering were I check the limbs only by sight and feel. The only time I have ever had a problem with twist is when it was naturally twisted before I even started tillering. Maybe I'm too much of a perfectionist.

[Diligence]

Just a quick update.  I decided to take off a bit of the belly with a scraper, and also to narrow the handle section a bit.  This had the desired result of getting more bend thru the handle.

Also, I took the bow to full brace height --- and lo and behold, most of the twist came out of the bow!  At low brace it is there, at high brace it's much better.

It's sitting at 52# at near to 28".....I decided to see what I could get out of it.

Thanks to all of you for your advice.  I'm going to sand and finish the bow, then shoot it a bunch and re-tiller as required.  I will post a final picture when all is done.

Cheers,
D

[Pat B]

Don't worry about sanding and finishing it just yet. Take it out and shoot the snot out of it then sand it and finish it.