Should I Adjust Tiller ? How?

[johnston]

So my old faithful hickory flatbow has developed a situation. Nice when rested unbraced nice when braced.
Two hours or so later the top limb is a half inch stronger at brace. Unstring it and 30 minutes later all is well.

Afraid to adjust it after it has been stressed and afraid I'll throw it out if I scrape it rested. It is my favorite
and I want to treat it right but don't know what to do if anything. Any help would be appreciated.

Lane

[adb]

Posting pictures would be infinitely helpful.

[johnston]

adb normally you would be right but the essence of my question is simple, to re-tiller after
stress or not. Or is it something I even need to worry about.

Can post pics tomorrow but all you'll see is one limb is stronger than the other after stress.

Lane

[Josh B]

Lane,  this is a common problem.  I will try to explain the cause of it before I attempt to explain  the cure, perhaps prevention would be a better word.  I'm not the smartest guy in the woods and I can't find an app on this phone that uses the crayons and a big chief tablet I usually express  myself with, so please bear with me. What  is happening is that when you draw your bow, as the pressure increases on the web of your thumb (on your bow hand) you naturally transfer the increasing strain to the ball of your thumb as opposed to keeping it all on the web. This shift in pressure changes the fulcrum point and forces the bottom limb forward.  The harder the draw, the more pronounced this effect becomes.  This adds slot of stress to the lower limb because it now has to bend further than the upper limb.  This can be counteracted several ways.  One measure is to make the lower limb a bit longer than the upper, which reduces the stress by having more wood work. Another thing you can do is tiller the bow so that the lower limb is a bit stronger than the upper, which balances out the shift in your grip.  I use a combination of the two

[Josh B]

(Continued)r
Now this is more for prevention, something to keep in mind for future bows.  As far as the bow hour concerned with right now,  it sounds as if it is more an issue of string follow as opposed to set.  That being the case you have a good chance of correcting it.  The problem is you will undoubtedly loose several pounds  of draw weight in doing so.  If you don't  correct it that string follow will most definitely   become permanent.  Sorry to be the bearer of bad news, but those are my honest opinions on the subject.  Hope I helped at least a little,   Josh

[Josh B]

Let me try this again.  Think of your bow as a teeter-totter .  The part of the grip where the web of your thumb grips the handle is the fulcrum point.  As the draw resistance increases, you naturally shift the pressure to the meaty part of your thumb which lowers your grip on the handle. This in turn moves the fulcrum point lower on your handle, giving the upper limb more leverage  on the lower limb. This causes the lower limb to have to bend farther to compensate for the leverage disadvantage.  Instead of tiller checking with the filler stick centered where  the web of the thumb is placed, put the tiller stick in the middle of the handle to check tiller. This should help balance the limbs at full draw.  I hope that makes more sense,  Josh

[mikekeswick]

To counter this the lower limb needs to be shorter not longer! Short limb = stiffer , longer = weaker (all things being equal and all that...)
It should definately be sorted out asap, especially if it's your favourite. It5 will get worse not better over time.
When the center of the bow is the center of the handle you need to tiller the bow so that the lower limb is a shade stiffer to counter this problem.
If you don't want to lose poundage give your weaker limb a mild heat treating - somewhere around light brown, stops before you get to medium brown (subjective I know but you get the idea). I wouldn't introduce any reflex or else you will end up 'chasing the problem'. Also remember to let the bow rest for 3 - 4 days after heat treating.
Hope this helps.

[Pappy]

If I didn't want to loose lbs. I would just shorten the bottom limb by an inch or so,that should do the trick,it will probably pick up 2 or 3 lbs that you can adjust with or live with. Never tried heat treating one limb but I suppose that would work also.
   Pappy

[George Tsoukalas]

Nothing approximates how the bow looks when you draw it. My bows are not done until I pester my wife to take some full draw pictures so I can adjust tiller. I like even tiller or slightly stiffer (1/4") bottom limb. Drawing in front of a mirror helps as does in front of a window at night which keeps the neighbors interested in my bow making efforts. You could slide the arrow pass down a bit to help your situation. If you have been shooting it as is and it shoots well then leave it. I've broken a few bows trying to get a picture perfect hero shot. We are dealing with wood and in spite of our efforts to tame it "it is what it is" to use a saying by Bellichek. Jawge

[George Tsoukalas]

Nothing approximates how the bow looks when you draw it. My bows are not done until I pester my wife to take some full draw pictures so I can adjust tiller. I like even tiller or slightly stiffer (1/4") bottom limb. Drawing in front of a mirror helps as does in front of a window at night which keeps the neighbors interested in my bow making efforts. You could slide the arrow pass down a bit to help your situation. If you have been shooting it as is and it shoots well then leave it. I've broken a few bows trying to get a picture perfect hero shot. We are dealing with wood and in spite of our efforts to tame it "it is what it is" to use a saying by Bellichek. Jawge

[johnston]

Thank you all. Sometimes I forget just how much I don't know.
This bow has probably 10-15000 arrows through it and I guess
I thought it was immortal.

Really don't want to lose weight so will try heat first and minor
piking after. Bow has static levers so it would be easy to do.

'Ol Jawge may be right about just leaving it alone. How can a stick
be so complicated?

Lane

[n2everythg]

Shoot it and enjoy it. Don't stress over it.
When it breaks make a new one. 

[dragonman]

if you turn the bow upside down and shoot it the other way up for a while and shoot it same as before it will gradually adjust its self without any major surgery, it has worked for me several times anyway..... good luck with this common frustrating problem.   I think gun doc explained the cause of the prob well.

[Josh B]

Okay, I'm fully awake now, so I shall try again. It was pointed out that piking a limb makes it stiffer.  Not so much.  What it does is reduce the mechanical advantage of leverage ,causing you to exert more force to do the same amount of work. Let us not forget leverage  is the key problem at hand. By piking the lower limb, it will certainly be harder to bend, but you will have also shifted the fulcrum point of leverage the same distance giving the upper limb more leverage advantage. For a net gain of zero.  You could shorten the lower limb until your bow resembles  a Japanese Yumi and solved nothing.  That being said, the suggestion to heat treat the lower limb only is genius. That alone would probably do the trick. Probably gain a pound or to that way.  Once again  good luck and I look forward to hearing how it turns out,  Josh

[johnston]

I really want to thank everyone for their help. This is a really good bow and
I just plain don't make many of that kind.

Figured if I heat treated to start and it did not solve the problem I would wind up removing
wood and didn't know how waiting for rehydration would be and so...shot the bow 48 arra's
so I could see the problem and seeing no unbending spots I went over the whole upper limb with 36
grit sandpaper. Kept it even with heavy pencil lines both sides and center. Had to check 4 or 5 times til it got close
then changed to 80 grit and sanded it out to 400. When tiller was once again dead even I went a little positive
on the bottom limb and shot it 48 more.

Everything still looks good. Did drop from about 50# to close to 46#. Arrows changed spine but by dropping from 580gr.
to about 470gr. arrows the cast wasn't affected and might even be a tad better. I have never posted this bow
and I think I' gonna do that.
Again, thank you for the help.

Lane