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
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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.
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
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.
Thanks everyone for the feedback. That will help quite a bit. Will post the finished product when I'm done.
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.
Pictures please
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. (//%5Burl=http://s1289.photobucket.com/user/mccarlson/media/First%20BBI/20130617_221408_zps350f0ac5.jpg.html%5D%20%5Bimg%5Dhttp://i1289.photobucket.com/albums/b510/mccarlson/First%20BBI/20130617_221408_zps350f0ac5.jpg)[/url] [/IMG]
Pulled to 13", still stiff right limb
(http://i1289.photobucket.com/albums/b510/mccarlson/First%20BBI/20130617_221330_zpsab2fcb1d.jpg) (http://s1289.photobucket.com/user/mccarlson/media/First%20BBI/20130617_221330_zpsab2fcb1d.jpg.html)
(http://i1289.photobucket.com/albums/b510/mccarlson/First%20BBI/20130617_221408_zps350f0ac5.jpg) (http://s1289.photobucket.com/user/mccarlson/media/First%20BBI/20130617_221408_zps350f0ac5.jpg.html)
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.
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.
how's it coming along?
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.
Get some pics up. You may be able to save it. What type of glue did you use.
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.
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.
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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.
What Bowjunkie said plus print this picture out below and save it for future reference. Works on longbows, or self bows too.
(http://i47.photobucket.com/albums/f165/ROY-CHRIS/limbalignment.jpg) (http://s47.photobucket.com/user/ROY-CHRIS/media/limbalignment.jpg.html)
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.
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.
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.
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.
You can fix that by making the string grooves deeper on the left side, and grinding some wood of the right edge of the limbs.
[img=http://poorfolkbows.com/images/aelb00.JPG]
Lemme try that again.
(http://poorfolkbows.com/images/aelb00.JPG)
D'oh! Roy beat me to it.
thanks, Jeff. good to know.
Another update. I was able to fix the string alignment by a combination of deepening the knocks and removing wood on the side that was bowed out. I also removed wood from the bowed side of the belly so I didn't have to weaken the limb so much.
Tillering was going great until my bamboo(too thick probably) splintered up. I added the pics below. I used super glue to try and fix it. Will try to continue tillering today. I've got it pulling pretty even with a 5 1/2" brace to 18".
By the way, thanks everyone for the help on this one. I've learned a ton.
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Yes the bamboo looks pretty thick.
If you can keep it together through tillering then some sinew or string wrapped around the beginning could save it.
I'd also add,some on,the opposit limb to even out the look.
is all the "white wood" bamboo?
Or is this a tri lam?
Yes. All the white is bamboo. It's way too thick but the super glue seems to be holding for now. I've got it tillered to 21"
No matter how thick the bamboo I always round off all corners including the bamboo before and during,tillering.
In this case there might have been a nick or something.
I didn't do that. That is good to know. I'll do that for the rest of the tillering.
Thanks
Another update. I've got the bow tillered to 24" but have new bamboo splinters although they've all been very thin. I rounded the bamboo on the edges with sand paper, then applied superglue to all the edges and repaired the second splinter. I'm hoping to tiller it to 26" and get the weight down to around 45# at 26". If it lives, I will final sanding and apply super glue to the entire backing after removing the rind.
The good news is I've got more bamboo cut and ready to taper(this time I'm tapering it much thinner.
The key on the bamboo tapering is to thin and flatten the back till the edges are thin. Less than 1/8 maybe 1/32.
Then trace out the pattern and cut it out. Now thin and taper,as,need to,get even thickness on edges.
If your careful you can easily sand off the bamboo with a sander and then when you get close use a toothing plane. Then re glue a new piece of bamboo on and place it back onto your form. I was able to do it with this BBO bow I got a bunch of cracks in over the winter. Still came out with a hunting bow and shot my first longbeard this spring with it. When I placed it in the corner of the garage it was way under weight, like 35#, adding the bamboo and another thin lam of osage brought the weight right back up to my desired 45# when all said and done with tillering... Anyways just a thought!
Picture of my harvest with "Second Chance"
(http://i1177.photobucket.com/albums/x344/bowhntineverythingnh03743/2013050395072126.jpg) (http://s1177.photobucket.com/user/bowhntineverythingnh03743/media/2013050395072126.jpg.html)
Is it possible to grind the bamboo down enough to put linen over it?
Would linen or can is hold?
Quick Update: I continue to have problems with my overly thick bamboo so I cut backing from tent material and am attempting to back the bamboo with synthetic fabric. I'm hoping it will keep the bamboo from getting worse and allow me to tiller this bow.
Good news is that I've learned a ton on this bow and my next BBI should be much better.
I'm also working on a board bow so I increase my chances for success.
This bow is officially dead. I plan to cut off the handle and make a takedown with it. Starting my next one tomorrow.