Trying to finish one. Tillering suggestions appreciated.

[mwosborn]

This is a hackberry recurve I started in Jan.  Getting around to finishing it.  I heated the belly about 6-8 weeks ago and it has been hanging since.

My question - at brace the upper (right) limb appears to be stronger (negative tiller).  However, as I draw it on the tillering tree the string nock pulls left toward the lower limb and the upper limb tip seems to travel more based on the grid behind my tree.  This would indicate a stronger lower limb?  I am working to get the limbs so that the string nock travels in a straight line when drawn and then returns to brace in the same straight line.  Not sure how to do that at this point!
 Here are a couple of pics.

Unbraced, braced, pulled to 15", pulled to 20".

Thanks!!

Mitch

 

 

 

 

[macbow]

Good looking bow.
Is it possible the tip is flipped a little,more,on the right side causing the extra deflection?

[4est trekker]

I agree with the above...your first picture seems to bear that out. Also, make sure your bow is dead-level and squared with your yard stick. I have marks to help me maintain a level bow at brace and have my yardstick squared to it. I also keep little shims of sandpaper to help level on the tillering tree. A little off at the handle means a lot off at the tips.

[takefive]

No tillering advice here, just have to say that is one beautiful bow and I'm sure you'll get 'er tillered.

[Roy from Pa]

My question - at brace the upper (right) limb appears to be stronger (negative tiller).

 However, as I draw it on the tillering tree the string nock pulls left toward the lower limb and the upper limb tip seems to travel more based on the grid behind my tree.

Mitch, that looks perfect to me. I first level the bow on the tree and, after that I am only concerned about the vertical travel of the pull rope of the tree. I like the fact that you have your pull rope pretty much where your middle finger of your draw hand will be when shooting the bow, and I like the fact that the bow is just sitting in the tree cradle and not clamped down. Those two facts alone, let the bow just sit there in a neutral state and when you pull it with the tree rope, it balances itself as to how it, the bow, wants to react when being drawn. Now think about this, where your pull rope is connected to the bow string, " above center " which is where the middle finger will contact the string when shooting the bow, "means" you are applying more pressure to the top limb than the bottom limb. So naturally you will be applying more pressure to the top limb. So it has to bend more compared to the bottom limb, as you are applying more pressure to it. So don't worry about how the top limb tip travels coming down the tree, only be concerned with the vertical travel of the trees pull rope. The fact that the pull rope is drifting to the left means the bottom is stiffer when drawing the bow, thus it needs more wood removed to get the pull rope traveling down the vertical line of the tree. Many guys tiller for a positive tiller, but since I started tillering for equal limb timing, I have found that most of my bows end up with a positive tiller on the bottom limb, exactly opposite of what most guys tiller for. I realize many guys have different tillering methods, and they make very nice bows. But in my opinion, tillering for equal limb timing is the best method.

[Bowjunkie]

I concur with Roy. The hook pulls towards the stronger limb, relative to how the bow and string are held. The reason the top limb is coming down sooner is because you're holding the bow at the center but pulling the string from a good distance above it. This puts more strain on the top limb causing it to flex more.. i.e. act weaker... regardless of the fact that it appears stronger at brace... with your holds, it isn't yet strong enough... so you need to weaken the bottom limb in order to sinc it with the top.

In your bow's case, I would begin weakening the bottom limb and checking it as I go. Often it doesn't take as much as you might think.

A better bet for a split finger shooter is the asymmetrical design which would put the bow center closer to the string hand fulcrum, and ultimately cause less of a shift between static and dynamic balance, and usually results in a tiller profile that is close to even after the limbs are sinchronized at full draw.

The bow I tillered last weekend is such a bow and resulted in a 1/16" negative tiller after it was done. Part of that measurement is due to a slight hump in the bottom limb right where I took the measurement. If it wasn't there, I believe the bow would show an even tiller.

Dean was right in his organic bow tillering article when he said that many folks who build symmetrical bows and shoot them split fingered, and tiller them a predetermined 1/4" (or whatever) positive are making the wrong limb weaker.

You're on the right track, Mitch.

Do yourself a favor and make the next one with a shorter bottom limb and see and feel the difference. Even with both bows timed to perfection, there's a difference to be felt.

[mwosborn]

Thanks for the help guys!  I will slowly weaken the lower limb and see what happens.

I have read a lot of the discussions on here concerning tillering from center vs from where it is actually pulled.  It can be confusing!  It just makes sense to me the way that Roy and Jeff are describing.  

I am glad you mentioned making the bottom limb shorter on the next one Jeff - that is what I was planning on trying (after reading a bunch of old posts about the topic).

Will let you know how this one turns out.  Heading out to the shop now.

[Roy from Pa]

Well Mitch, how did things work out?

[mwosborn]

Well Roy, I am getting nervous.

I did a small bit of scraping on the lower limb (whole length) and then worked the near fade just a little because I thought it needed to bend a little more.  It definitely weakened the lower limb - the brace is now a full 1/4" negative tiller. (looks terrible).  The pull rope is still pulling to the lower limb a bit - maybe not quite as bad though.

I flipped the bow over in the tree cradle essentially switching limbs and the rope pulls dead straight.  This tells me I still need to remove more wood from the actual lower limb.  But the braced tiller is already 1/4" negative!!!

I had to prove to myself that the rope will drift to the strong limb.  I took an old hickory selfbow that was one of my very first attempts a few years ago and intentionally weakened one of the limbs and put it in the tree.  Sure enough the rope drifts to the stronger limb.  However - the brace on this bow corresponds to the weak and strong limbs.

The bow I am trying to work on now is driving me nuts.  At brace the upper limb seems to be stronger....but as I pull the rope it drifts to the bottom limb indicating it is stronger.

I decided to shoot it at about 20" draw since I have already pulled it to that anyway.  Quite a bit of handshock with arrow 1.25" above center.  It is noticeably less when I move the arrow down to about center and shoot it.

Might be time for a coors light - and I don't even drink the stuff!!  

[Echatham]

Hey roy and jeff... Ya ever have a bow pull toward the top limb?  Every bow i tiller starts out with the lower limb stiffer and it takes a great deal of scraping and "negative" tiller to get it tracking down the vertical line.  Never once had my pull rope drift right of the line.  Just somethin that makes me scratch my head and wondered if you guys have a similar experience.

[Echatham]

Mwosborn i thought i had already commented on your bow but i guess i was mistaken... I love the profile and it looks really nice to me.  Ive had static recurves on the brain for a while now and i got to build another.  Thats what i want to hunt with this year so i gotta get on it.  Im coming back to this thread for inspiration

[Roy from Pa]

Mitch, I know that all the bows I have tillered for equal limb timing have had zero hand shock. I am wondering if the hand shock isn't coming from the design of your bow, especially the amount of reflex you have in the tips. However you said by lowering the nocking point, the hand shock got noticeably less. By doing that, you are pulling more in the center of the bow and getting a more defined dynamic center. As Bowjunkie stated above, an asymmetrical design would be better suited for tillering for split finger. I also have seen some of my symmetrical bows with a high negative tiller and yes I don't like the looks of them either. Hence now I make the bottom limb a good 1" shorter now. Actually there are many bowyers that make the bottom limb shorter to even up the dynamic center.  Eric to answer your question, the majority of the bows I have made, the pull rope drifted to the left. However my last swap bow, the pull rope drifted to the right, top limb, and I was surprised and it was so easy to tiller that bow, and it ended up with a -3/16th tiller. It was symmetrical, had it been  asymmetrical, the tiller would have been more like even.  I have since started putting the stronger billet in the top limb. Since I make bows by splicing two billets together, I make the billet with the thicker growth rings the top limb. Now with a one piece stave, I would make the top limb the end of the stave with the thicker growth rings, as when a tree grows, the trunk end of the stave will have thicker rings than the end that was 6 feet up the tree. I have heard guys say to make the bottom limb the trunk end of the bow because it gets more stress. I can not see how that could be true as we already decided above the we are pulling the bow above center so the top limb does get more stress applied to it. So like I said above, when I make a bow now, I design it for the top limb to be the stronger of the two billets I splice together. Let's wait for Bowjunkie to comment on this, Mitch.

[George Tsoukalas]

If the pull string slides towards the left  limb that means that limb is much stronger. Just the way it is. Took me about 10-15 years to figure that out. LOL.  

I've often flipped a bow around to make the tiller "better". I've also slid the arrow pass up or down.

I should mention that while I tiller I take the strung bow and and do some partial draws to check the evenness on the handle.

In the final analysis, how she feels in the hand is key. I check tiller in front of a mirror or have my wife take a digi pic. Nothing comes close to how you hold the bow and draw.

Hand shock can be a function of several variables including poor tiller, poor limb timing, light arrows, etc.

The rope and pulley is great for checking limb timing...pull...slowly let down.  A photo while drawing is also helpful with tiller.

Cannot think of much else to suggest.


Jawge

[George Tsoukalas]

I should mention when I tiller I pull from the center and make last minute adjustments while drawing or from a digi pic or two. Jawge

[Echatham]

here is a tidbit that might be applicable here.  im shooting in a character bow right now whose limbs are timed and the tiller is good.  however because the top limb has several holes in it and i left extra wood around them (probably over-compensated) the top limb is heavier weight... center of gravity  is around the arrow pass not the center of the handle (its a symmetrical bow)   anyway it has more handshock than any bow ive made, not unbearable, but noticibly different than other bows.  my thinking is the difference in weight between the limbs is causing it.

Roy i said the same thing about the top limb being more stressed but Jeff convinced me otherwise... or maybe i misunderstood.  im interested in what he has to say on this one.

btw... im done with symmetrical bows i think.

[Roy from Pa]

Eric I sometimes don't even care to offer advice in these types of threads, as everyone has their own way of tillering..    But I know what's been working for me and you also I believe. Jeff said this above:
The reason the top limb is coming down sooner is because you're holding the bow at the center but pulling the string from a good distance above it. This puts more strain on the top limb causing it to flex more.. i.e. act weaker...

George you have made many more bows than I have. You pull from the center of the handle then finish the tiller by drawing the bow by hand, from I suppose where you will be drawing it when shooting. Let me ask you this, after you start tillering by pulling the bow with your hand, on an average, which limb do you normally need to remove wood from?

[mwosborn]

Just when you think you might (just might) start figuring out this bow building stuff a bow your building reaches out and slaps you one just to remind you that you don't know as much as you think!!!

I guess it is what I love about building bows - every bow is different and everyone gives its own challenges.

Roy - you are correct in the fact the hand shock can be coming from a number of things. I might not figure out what it is!  It is not terrible - just a little shocky (I've done worse).  I am glad you offered advice - I've seen the many nice bows you have built - your advice is sound and always welcomed.

Eric - thanks.  This is my first static.  I am hoping to be able to hunt with this one come fall!

George - appreciate the comments.  I actually had to do some testing to convince myself the rope pulls to the stronger limb.  I should have asked you sooner!  

[Bowjunkie]

“Jeff said this above: The reason the top limb is coming down sooner is because you're holding the bow at the center but pulling the string from a good distance above it. This puts more strain on the top limb causing it to flex more.. i.e. act weaker...”

Yes, and so it needs to be made stronger (or make the bottom weaker) to resist that additional strain. If not, the nock point will travel toward the stronger acting limb during the draw.

From Dean’s article: “If you do this with a same-limb bow, you will discover that the bow only balances when the upper limb is a bit stronger than the lower limb, not weaker. How much stronger (negative tiller) depends upon the wood of the bow and the discrepancies in length between the upper and lower limb designed into the handle.”

A couple things are contradictory and confusing in your posts, Mitch. You said as you weakened the bottom limb, the string fulcrum came back straighter, which means the relative limb strength was better balanced and you were doing the right thing. This revealed a 1/4" negative tiller, but then when you flopped it on the tree, it pulled straight. That is counterintuitive. It SHOULD have pulled toward the bottom limb severely… if your bow is indeed symmetrically designed. That part doesn’t make sense to me. Was the handle perfectly level each time? Make sure the handle is level, not necessarily the limbs, or limb tips.

At this point I would double and triple check my measurements on the tillering tree and bow, as well as make sure everything was level, plumb and square just to be sure.

I have to have my bows balanced/timed/sync’d whatever you want to call it. And doing so with a symmetrical bow can be a pain in the butt… and I don’t care for a considerable negative tiller, so I make my bows asymmetrical. It puts the static and dynamic balance points together with my fulcrums and tiller is usually close to even after limbs are timed.

If you didn’t have those nice recurves on there, I’d ask you to chop some off the bottom limb
 

[Bowjunkie]

Eric, you said... "Hey roy and jeff... Ya ever have a bow pull toward the top limb? Every bow i tiller starts out with the lower limb stiffer and it takes a great deal of scraping and "negative" tiller to get it tracking down the vertical line. Never once had my pull rope drift right of the line. Just somethin that makes me scratch my head and wondered if you guys have a similar experience."

Yes, but very rarely. The reason is as I alluded to in my last post... When we pull the string from above the static balance point, the top limb is prone to tip towards us, causing the nock point to travel toward the bottom limb in relation to the shelf. The farther above static balance we pull, the less likely you'll ever see the nock drift toward the top limb when you begin tillering.

For instance...

The hook is slightly prone to drift toward the bottom in bows like mine... asymmetrical/split finger, because I pull the string from just slightly above bow center.

It is extremely prone to drift toward the bottom in bows like Mitch's i.e. symmetrical/split, because the string is pulled from a greater distance above center.

But conversely... the nock traveling toward the TOP limb when first put on the tree is much more likely to happen on an asymmetrical/three under set up, because the string is being pulled from virtually the exact static balance point... so if the top limb is just the slightest bit stronger... it'll pull that way.

I would guess this is the type of setup that Roy was working on when it happened to him.

Is this making any sense?

When you said it takes a good deal of negative tiller to get the limbs sync'd, I'm guessing you are referring to symmetrical bows?

[Bowjunkie]

Those various bow types I mentioned... and their degree of preponderance to nock point 'drift' away from the line... are directly related to the degree of 'shift' from static balance to dynamic balance during the draw.