Mind numbing!!!

[ssrhythm]

Ok.  I’ve seen Clay Hayes say he makes his bows ~1/8 pos tiller because he shoots 3 under…where as someone shooting split would want to have a greater degree of positive tiller…reasoning that as you move your hand up the string, it puts more stress and requires more work of the bottom limb.

This is what I thought I remembered getting from TBB.  I remember it stating that it is actually opposite of what it would seem to be. 

Mr. Yancey told me what I’ve seen many folks say on the innerweb….3 under puts more stress on the bottom limb and requires it to work more. 

I’ve tried to draw it out…that was a joke.  I really don’t want to test it out to an extreme level (so I can actually see it) on one of my bows. 

So…

A.  what’s the truth here with an explanation of your understanding of the physics involved?

B.  If I have 1/4” positive tiller on a recurve, and I add a touch more recurve to the weaker top limb…
     will that result in less positive tiller or more positive tiller at brace.

For some reason, these questions are turning my mind to mush today just as the whole issue of reducing limb twist by thinning one side does.  Please help clarify!  Thanks.

[SDBurntStick]

This helped my understanding of it. 

http://buildyourownbow.com/the-truth-about-bow-balance/

[bownarra]

Well whoever Clay is.....he is wrong! 3 under puts more strain on the lower limb as you are further from the center of the string. If we could somehow hold the bow dead middle and pull the string evenly either side of the exact middle then there would be no need for positive/negative tiller. eg. a crossbow
The further you go away from the middle of the strings length the further you have to increase that limbs strength relative to the other. glassbows are good for testing
The other option rather than trying to make it such and such a measurement (which won't always be correct anyway) is to make your tillering tree so that the bows handle is supported but free to 'rock'. Then use a rope and pulley for the pulling string. Draw a line straight down from the point the arrow touches the bow. Clip (small karabiner) your pulley rope to the string right where you will be pulling from.
Now as you tiller your bow the 'pulling point' krab is free to move left or right dependant on the limbs relative strength to each other. If you have the bow balanced perfectly the 'pulling point' on the string will follow the straight line you draw. If not then it will drift towards the stiff side. This balance as you draw is key to making a well manared bow that will last and last......because it was made balanced in the first place
I can take a photo of my set-up if you want. It is well worth the time to make a set-up like this as you can tiller each and every bow, of whatever design, perfectly. A lot of handshock ,thuds,twangs and buzzing can easily be avoided Once I made my set-up it confirmed a whole lot f stuff regarding tillering for me.

[Del the cat]

@bownarra
 I like that karabiner idea, 
A pulley would be even more sensitive, I might give it a go for the fun of it as I'm an advocate of letting the bow rock on the tiller.
Del

[Eric Krewson]

I take a different tact, I don't worry about this and that and tiler a bow so it shoots and arrow straight and true with authority and has minimal hand shock. I have made a lot of bows and have never made two that had wood so similar that I could use a formula to tiller them.

[SDBurntStick]

Well whoever Clay is.....he is wrong!

Clay Hayes is a pretty reputable bowyer.  He has a great YouTube channel.  Not saying he is always correct but he definitely helped me get start with making my own bows.

[Morgan]

Well whoever Clay is.....he is wrong! 3 under puts more strain on the lower limb as you are further from the center of the string. If we could somehow hold the bow dead middle and pull the string evenly either side of the exact middle then there would be no need for positive/negative tiller. eg. a crossbow
The further you go away from the middle of the strings length the further you have to increase that limbs strength relative to the other. glassbows are good for testing
The other option rather than trying to make it such and such a measurement (which won't always be correct anyway) is to make your tillering tree so that the bows handle is supported but free to 'rock'. Then use a rope and pulley for the pulling string. Draw a line straight down from the point the arrow touches the bow. Clip (small karabiner) your pulley rope to the string right where you will be pulling from.
Now as you tiller your bow the 'pulling point' krab is free to move left or right dependant on the limbs relative strength to each other. If you have the bow balanced perfectly the 'pulling point' on the string will follow the straight line you draw. If not then it will drift towards the stiff side. This balance as you draw is key to making a well manared bow that will last and last......because it was made balanced in the first place
I can take a photo of my set-up if you want. It is well worth the time to make a set-up like this as you can tiller each and every bow, of whatever design, perfectly. A lot of handshock ,thuds,twangs and buzzing can easily be avoided Once I made my set-up it confirmed a whole lot f stuff regarding tillering for me.

Please post your set up.

[Don W]

Don't feel alone. I don't understand how so many accomplished bowyers can have completely different opinions on some of these subjects. You can't help but respect the opinions, so there has to be a reason for the opposite opinions that all seem to work. I get there isn't an exact formula, but I don't believe there is not something that will get us at least to final tillering.

I've started to copy dimensions of working bows working with calipers and refining them. So far it looks like it will work, but it would need to be process that lots of people followed and documented for all the different styles and woods. Something like Tom Baker did and it really would just be an extension of his work.

[ssrhythm]

Heck...I may have misunderstood what Clay was saying, but I swear I thought I read the same in TBB...the volume I can't seem to find at the moment.  My tillering rack has a rounded cradle which allows the bow to rock and I use a pulley and carribener as suggested...and it is definiely helpful to see the limbs' strengths relative to each other. 

Ok...how about the second question?  If I add just a touch more recurve to the top limb of a bow that has 1/4 inch positive tiller....indicating that the top limb is a tad weaker than the bottom limb...will this result in a greater amount of positive tiller or will it result in less positive tiller.

The reason I ask:  My bow currently has 1/4" positive tiller and the top recurve has just a hair less curve than the bottom limb.  It's not much...maybe 1/8" or so less total curve at the tip. 

My first thought was..."if I heat it up and put another 1/8' of curve in it, it will strengthen the limb and result in a touch less positive tiller."   

My next thought was "you really don't know that, and you have no idea if it will add strength and result in less positive tiller or if it will put more stress on an already weaker limb resulting in more bend and a greater degree of positive tiller...and you certainly don't know how much its going to affect the bend regardless of which way it goes, so don't screw with it dummy!"

It's shooting great, so I'm not going to mess with it, but the question is still messing with my brain!

[meanewood]

I try to replicate how the bow would be drawn and shot during the tillering process.

So if it is a stiff handle type, have a flat block to support the bow which is the width of your grip and pull the string from the arrow nocking point, but have a folded piece of thick leather which is attached to the pulling string which is the width of your three fingers plus arrow width.

If the bow is to be a bend through the handle design, then allow it to pivot (tilt/rock) but again, pull from the nocking point with the leather attached.

[Pappy]

I try to till with bottom limb a little stiffer for 3 under shooters, Pappy

[Morgan]

My opinions on the positive / negative  tiller thing may come from a place of misunderstanding, but here it is. None of the bows I make are of a perfect stave. One limb is never exactly the same as the other. The whole measure to the string @ brace don’t always work, it may on laminated or board bows though, idk. It is not uncommon to have a bow that looks off @ brace but is tillered evenly and well. My tillering routine typically involves starting the process pulling dead center of the string, with handle support dead center of the bow. I will bend it like this out to 10-12” at this point I will ensure that the handle is supported where the pad of my bow hand will rest and my strap is pulled where my middle finger will be on the string and finish tillering. The reason I start from long string to 10-12” on the short string pulling in the middle is that early on I have always had an issue balancing the stave in the T tree if I started out pulling the string off center. It seems to balance better after the bow is to the brace point and bending a little. All that may be 100% wrong but it has worked for me. I am interested in seeing and trying  bownarras set up for developing balances limbs.

[superdav95]

Ssrhythm,   I had a bow do the same to me and I got lucky with it in the end.  I had a 1/4 positive tiller on my yew recurve bow I made a while back and I felt like it was little too positive on top limb so I added a hair more to upper tip and it worked.  It essentially (from what I gather) shortened or stiffened or both the top limb and made the bow look little more balanced.  I found it helped eliminate the hand shock too.  Not sure if that answers your question or not but I would say it would lessen the positive tiller by adding little more recurve on top limb based on my experience.  As for the tillering set up seems like good advise here.  Only thing I’ll add is I start off with an inverted tiller set up and clamp my bow down belly side up to my scraping board and use a long string to start and pull from center of knock point location based on positive upper limb.  This saves me having to remove the bow between scrapes and saves me some time.  When I get closer to final tiller I move to low brace string and main tiller tree with pulleys similar to others here.  I haven’t heard of others using an inverted tiller set up yet but I find it works for me and save some time on the the most time consuming part of bow making.  Hope this helps ya. 

Dave

[bpctcb]

I tiller to achieve the best bend at full draw. I have no regard for what the tiller measures at brace. I’m pretty much right with bownarra on this.

BP

[Don W]

So are you saying you don't measure the string distance at all? If you draw the bow on the tree, replicating where you will hold and draw, and the draw is straight down (following a straight line and not pulling to one side or the other) that makes a perfect tiller?

Do you worry about distance the limbs draw? In other words do you want the tips to wind up in the same horizontal line  (which could not happen unless the limbs were the exact same length) or does that not matter either?

This is the problem being new. We try to many different processes mixed together because everyone explains it different and not completely.