Problem during tillering

[BowsAreFUN]

Hi gang,

Tillering a reflex/deflex bow right now and i ran into a weird problem. I got it bending pretty equally on each side at 6"/7" with a long string and decided it was about ready to put a real string on and brace it at 3".

 

Braced it with a stringer (had to use a lot of strength since the bow is still really heavy) and was about to put it back on the tree when i noticed the bow's curve was kinda lopsided (didn't take any pic of that). Unstrung it right away and now the bottom limb (on the right) hang about half an inch lower at rest (without any tension) than the top one, which it obviously didn't do before.

 

And this curve difference of course persist when the bow is stretched.

 

Anyone ever had something similar happen? Not quite sure what caused it, maybe the force needed to string it warped the bottom member a bit? Is this fixable? Was just gonna remove wood from the top limb and try to get it bending equally again, but wanted to check with you guys before i screw up again if there was better way to try fixing this.

Thanks!

[Mad Max]

What kind of bow is ?
bamboo/ipe?
fades look short and steep angle!

[Pat B]

You may have over stressed it when you braced it if it was way over weight. Get the weight down some and continue on with the tillering.
 You are dealing with natural materials so each bow is different and natural bow materials aren't as durable as man made bow materials.

[mikkekeswick]

The limb that took the set was weaker than the other.
You can use set all the way through tillering to make sure you have the right limb balance.
The lower shopuld be a shade stiffer than the upper limb.

[die_dunkelheit]

Originally posted by Pat B:
You may have over stressed it when you braced it if it was way over weight...

What Pat said, and on that note...
Never, NEVER, draw a bow that is being tillered past it's intended draw weight.

[Roy from Pa]

Your bow was still way too heavy to string up, however you should be fine once you get the limbs evened out. You should floor tiller a bow first and get some bend in the limbs before stringing up. Then file in the string grooves and put a string on it that lays snug against the belly when in the string grooves. A real long tillering string is not a good idea as it doesn't apply much stress to the outer third of the limbs. The shorter string you use, the more stress it puts on the outer third of the limbs. I have my tillering tree and pull rope setup to replicate where the center of my middle finger of my drawing hand will be when shooting the bow, and I assume my arrow nocking point on the string will be 3/8th above the shelf of the bow. At that point I have a black vertical line drawn down the wall. As I pull the pull rope down, I want the pull rope to track straight down that vertical line on the wall. That means both limbs are bending in sync. If one limb is stronger than the other, the trees pull rope will drift off the black line on the wall and it will "always" drift in the direction of the Stronger limb. I keep removing wood from the stronger limb and work the bow 20 to 25 times after removing wood and keep repeating that process to get the pull rope tracking the black line on the wall. When the tips are bending to about 6 inches, I brace the bow to about 3 inches and repeat the above process. When the tips are bending to about 9 inches, I brace the bow to about 6.5 inches and finish tillering like explained above, all the while keeping the pull rope tracking straight down the black line on the wall. Picture of tillering tree below. One thing I have noticed on my setup is after tillering and the bow is shot in, the bottom limb takes a tad more set. So I now let the trees pull rope drift about 1/8th" towards the bottom limb, which means the bottom limb is a tad stiffer than the top, which is usually what we want.

       

Video of tree.

     

[BMorv]

What Roy said...and in case you haven't floor tillered before, if you have a bow of similar weight you can use that as your guide to see if your bow is way too stiff for the tree.  You'll be able to tell right away that you still have a ton of work to do.  Get the floor tiller right with both limbs  feeling like they are bending equally and the rest of the tillering process is much easier.

[Mad Max]

Originally posted by BMorv:
What Roy said...and in case you haven't floor tillered before, if you have a bow of similar weight you can use that as your guide to see if your bow is way too stiff for the tree.  You'll be able to tell right away that you still have a ton of work to do.  Get the floor tiller right with both limbs  feeling like they are bending equally and the rest of the tillering process is much easier.

Very Important

[Wolftrail]

When I first started building wood bows I did not realize how important it was to floor tiller correctly. I guess it comes with experience.  The more I floor tiller is the quicker I get the bow to full brace and everything falls into place.

   

[Mad Max]

Originally posted by Wolftrail:
When I first started building wood bows I did not realize how important it was to floor tiller correctly. I guess it comes with experience.  The more I floor tiller is the quicker I get the bow to full brace and everything falls into place.

     

I had problems at first with out floor tiller,
Now It "fall into place"