First BBI, need some help please

[mccarlson]

Hello all,

I'm in the tillering phase of my first reflex/deflex BBI but need some help.  
First issue - 1 limb(right limb) is 5/8" higher(measured from tip of bow to flat surface) than the other, the one I'd like to be the top limb and the one I want to be slightly positive.  Right now it isn't bending as much at 16" as the "lower" limb.

- What effect will the 5/8" difference have?(on picture)

- Should I switch which limb will be the top limb and the one that will have slightly positive tiller?  The reason I chose the higher one to be the top limb is because a node is just above center on that side of the bow handle.

Thanks in advance,

Malcolm  

[/url] [/IMG]

[Echatham]

are you talking about when the bow is un braced the limbs have different amounts of reflex, and so one tip is higher than the other?  if so that doesn't matter as much as what it looks like at brace and at draw. from that pic it just looks like you need to take some off of mid limb on the right limb and you will be in business.

[Roy from Pa]

You also should use a shorter tillering string. Use a string that when the bow is first strung, the string lays tight against the belly of the bow. The shorter string you use, the more stress it applies to the outer 1/3 of the limbs. When the limb tips are bending to 6 inches, brace the bow to a 3 inch brace height and continue tillering, when the tips are bending to 9 inches, brace the bow to 6 inches and finish out the tillering.  Also make yourself a tillering gizmo, the link shows how to make and use it.
    http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=000075

[LittleBen]

Roy is right on with what he's saying as always.

If I undertand correctly your concerned about the node being less comfortable to wrap your hand around?

I looked at the position of the node and it's only like 1" off the center of the bow. I would just make the stronger limb the bottom limb, and when you shape the handle, just flatten that one node however you need to make it comfortable. The handle area is going to be stiff, and non-bending. It won't fail from flattening that node. Obviously never grind off a node on the limb, but in the handle area it wont matter. Expecially if you put a leather wrap on the handle, you wont even see that the node has been ground down.

[mccarlson]

Thanks everyone for the feedback.  That will help quite a bit.  Will post the finished product when I'm done.

[mccarlson]

Just an update.  I realized why my right limb was stiffer.  I did not do a good job grinding that side of the bamboo down so it's a little thicker.  I've changed the top limb to the left one and changed to a shorter string and tillering it so the tips are at 6".  I have to remove some more wood on the stiffer limb(right) but I think I'm making progress.

More to come.

[LittleBen]

Pictures please

[mccarlson]

Here are some new images after some more tillering.  I'm attempting to get it to 3" brace but can't seem to get the short string off the belly not matter how short I make it.   [/url] [/IMG]

Pulled to 13", still stiff right limb
 

 

Not sure what to do next.  I was going to take more wood off the right limb but I also need to get it to 3" brace height.  I thought I cut my knocks at a 60 degree angle.  Not sure what I'm doing wrong.

[Echatham]

if thats a dacron string its going to stretch alot. when i first get to the short string, i use a long string with a spliced end and tie a timber hitch in the other end. i brace it at 3" or so and you can watch the string stretch until its on the belly. take it off, shorten the string, do it again. it may take a few tries to get it right.  that bamboo being thicker will keep having an impact, making that limb stiffer every time you turn around. just have to make the ipe thinner there. i ran into that too.  you will get around it. as far as picking a top limb, i usually have an idea which one it will be when i start, but i just shoot for even tiller and at the end one limb will probably be a hair stiffer anyway, and thats the top. if it comes out dead even, shoot it both ways, and if it likes one way more than the other, there ya go.

[Zradix]

how's it coming along?

[mccarlson]

Not too good.  Once I got the bow strung at 3" brace, I noticed 1 limb is really warped.  I must not found the right centers on the ends of the ipe core wood.  I used 2 weights on twine to id the center point of the tips for each limb but it was still way off.  Ill string it and post pictures tonight.

[LittleBen]

Get some pics up. You may be able to save it. What type of glue did you use.

[SEMO_HUNTER]

Oh my God, working with IPE brings back old terrifying memories. I hated my days when I was working with IPE, it will over power even the strongest of woods like  bamboo, and boo is one of the strongest bow woods known to man. I'm glad that I sold all of the IPE that I had on hand and went back to the old favorites like osage and hickory. Good luck my friend, you have taken on a project that just might get the best of you? I wish you the best.

[mccarlson]

Here are the pics.  The alignment is pretty bad.  My guess is that I didn't find true tip centers on either the ipe, the bamboo or both.  

I used smooth on epoxy.

  [/url] [/IMG]

  [/url] [/IMG]

[Bowjunkie]

A few things to check... mostly regarding symmetry... make sure the string grooves at the tips are cut the same on each side, otherwise the string loop will pull harder on one side than the other... pulling the limb to the side.

Check the limb thickness to be sure that at any one place in the limb, the limb isn't thicker at one edge than it is the other.

If this all checks out, unstring it and lay a weighted string on the bow from end to end and see if it bisects the bow down the center of the limbs and handle.

If that checks out perfect too, then it could be the core wood has internal tensions of its own which are causing the problem. Unfortunately, straight boards can be sawn from crooked, twisted, or transition wood... transition meaning the wood on the side of the tree that lies between a definitive tension side and compression side. In static applications like furniture, such wood is often acceptable, but in a dynamic application like a bow limb, it won't want to behave no matter how straight it looks at 'rest'. That's the chance we take when we make bows from boards/trees sawn by folks who aren't bowyers.

Depending on the cause, there may be options available for correction.

[Roy from Pa]

What Bowjunkie said plus print this picture out below and save it for future reference. Works on longbows, or self bows too.

   

[Bowjunkie]

Don't settle on a course of action until you know the cause(s).

Heating and bending may be an option as well, depending on which glue you used.

[J.F. Miller]

X2 on doing your best to determine where the problem really lies. is almost certainly one of the potential problems already stated. the illustration Roy posted is an excellent reference. I printed a copy of it a while back and usually dig it out right after I start pulling my hair out. can get confusing when trying to get a string lined up, no matter how many times you've dealt with this problem.

heating and bending is always the last resort for me. it practically always works, though, particularly if you have isolated the problem and do it carefully. I've only ever dry heated bows glued with Urac, and have never had a problem, even after repeatedly heating and adjusting the same area. not sure if you can do that with Smooth-on.

[mccarlson]

The attached illustration is helping.  I adjusted the knocks(filed down the side according to the drawing) and that helped some.  I check for center an the top limb is a little off.  I'ts also got a "dog leg" in it that is causing to to point out away from center.  The bottom limb doesn't do this.  I have been removing wood from the outside of the top limb to pull back when strung.

I think the root cause may be a flaw in the wood of the top limb.  The dog leg is really pronounced only when strung.

[Bowjunkie]

Jamie, yes Smooth On deals with it as nicely as Urac. I've made mutiple corrections to the same limb that was glued up with Smooth On with no adverse effects... in all sorts of bows... bbo's, tri-lams, glass/wood laminates, etc.