How Stable Are Your Bows?

[dragonman]

I find with many of my bows that I shoot a lot, the  distance between the bottom limb fade out and the string very  very gradually increases, when it gets to about 1/8"difference in tiller I usually reverse the bow , so that the bottom limb becomes the top and this solves the problem, but then the same thing gradually happens, over maybe a few thousand shots....in some cases I keep doing this.

Does anyone else have this same experience?  Do you think this is down to shooting style?  stressing the lower limb more with an unbalanced draw?,Is it poor tillering? or could there be other reasons....Some bows dont do this ,but a lot do!!

I was once in a club where a few guys had ELB's and I noticed this had hapenned to their yew bows, one case was severe....I told him he should reverse his bow and it may fix the problem, but he didnt believe me and left it!!!...so I know its not just me

[Badger]

  I have seen this quite a bit on self bows, not uncommon. It just means that the bottom limb is getting stressed a bit too much and taking set. Your hold is likely putting more pressure on the bottom or your MC levels may be varying some. Wood is not as forgiving as glass. I try not to build mine too close to the edge anymore for this reason.

[Marc St Louis]

Occasionally but not that often

[PEARL DRUMS]

I'm with Marc. When it does happen I know why right off the bat.

[dragonman]

so why would a bow that had an exact tiller for months start to develop an inbalance??

[Badger]

so why would a bow that had an exact tiller for months start to develop an inbalance??

  If a bow is marginal, too close to the edge of being stressed one slight overdraw can throw the tiller off. I like to tiller mine for a couple of inches more draw than I actually shoot at to keep them stable. I used to store my bows in a big cardboard drum. I didn't even think about the lower limbs gaining and holding more moisture than the top limbs. First time when they were draw comming out of the barrel some of them took set in the lower limb.

  I never did like that phrase about a good selfbow being 90% broke. The stage before being broke is when they start taking set. I like to stay inside what we call the elastic range and then your bow will stay stable for years.

[dragonman]

that makes complete sense Badger, thanks. I store my bows horizontal for that very reason , so cant be that...and I do usually  like to push design limits so that explains it.....I am going to follow your advice on this.

Dave

[sleek]

I dont understand moisture gathering at the lower limb? Does dead wood not still draw water up? If not, then which ever end is down gets excess moisture. So the best way is backside down belly up?

[PEARL DRUMS]

Water runs downhill sleek.

[bradsmith2010]

I agree with Badger, and the closer to the edge the bow is,, the more likely moisture content or an overdraw could effect the tiller in a negative way,, when I shot alot of tournaments,, if I shot two days in the rain with the bow strung all day the tiller might shift,,, lots of moisture out there,, I seem to have this happen more with sinew bows and I will just shoot the other limb up if needed,,I think the sinew bow is more sensitive to the moisture,, just more sensitive in general,,
I have thought of making the bottom limb longer since it is under more strain,, but have not done that yet,, and I usually start out with a little more positive tiller than needed in case it does shift a bit,, sorry to ramble,,
but I think the bows we see from the past with a shorter bottom limb did not start that way,, but was just a tiller adjustment later in the bows life

[dragonman]

I have never noticed a problem from storing staves vertically,  but it sounds very possible that water would sink into the bottom limb..so I turn them around occasionally...

as for making the bottom limb shorter or longer, I have heard theories that make sense for doing both...I think just make it a bit stronger, if its necessary...I.do try to leave the bottom limb slightly stronger, but they always tend to end up about equal in the end for some reason!!!

I think Badger hit the nail on the head. If this happens at some point later on in a bows life the bottom limb must have been very near the limits of its tolerance, and some small change was enough to overstress it. otherwise it wouldnt move

[Badger]

  I don't think storing them verticaly was the problem, I had a bucket full of bows with no air circulation. The humidity in the barrel was much higher than it was in the air. The top limbs got plenty of air circulation.

[PEARL DRUMS]

Moisture inside the bow will allow gravity to yank it down, however minute it is. When I'm drying a blank, like I am now, I flip it end for end every couple days. Maybe that's being anal, but hey. I want to build the best bow I can so I pay attention to everything and hope in the end it adds up to something.

[bradsmith2010]

Dragoman,,I think the trend over the years has been to make the bows more stressed,, pushing the limits of the wood,, and there is a trade off for that,,if the bow is going to be shot very little it will not show the signs of stress very quickly,, one of the best lessons I learned was from a guy I made bows for,, Mike Prince,, he would shoot several hundred arrows nearly every day out of my bow,,,,, if anything was going to give it gave,, gradually I learned that slightly overbuilt was the only bow that would hold up,, and that was a delicate balance, because the bow had to have good cast for him to compete on the level he desired,,lucky his draw was 29 inches so the power stroke made for a nice cast if I did my part in making the bow hold up,, if the bow held up to several thousand shots,, then it was usually stable from that point on,, when I tried to put the bow to the edge,, something usually gave

[Badger]

  Thats the same way I feel Brad, I gave up on the super skinny bows or super stressed designs.