Primitive Archer
Main Discussion Area => Bows => Topic started by: huntersteve on January 14, 2008, 11:35:13 am
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this is a bamboo backed red oak board bow that I've been working on....trying to finish up the tillering....It's obvious that the left limb which is the bottom limb is not bending as much as it needs too.....where should I remove wood to get this bow bending properly.....Thanks..Steve
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I would slowly remove wood fairly evenly from the whole limb now until it starts to catch up with the other one. Be sure to exercise it between scrapings. Also looks like you may have a slight hinge developing about a quarter of the way out on the right limb-keep an eye on that spot and don't take anymore wood from the area where it's bending more than the rest of the limb. Anywhere that looks like a straight line needs some scraping. Just take it slow and easy, exercise the wood, and keep posting pics.
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thanks Hillbilly.....I'll work on it some more and post more pics.......
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I agree with Hilbilly's assessment, the left limb looks pretty good just needs to be caught up. Sometimes I'd rather have a problem spot, it gives you more direction than just thinning the whole limb.
Run a 4" straightedge along the belly and look at the gap between wood and edge, that'll tell you where things are bending more or less. Try and catch that strong limb up first, a strong limb puts more stress on the other limb.
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thanks for the help guys....I'll work on it some more tomorrow morning after I get off work....working that wonderful graveyard shift....I'll post more pics tomorrow...Steve
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well...I worked on the left (bottom) limb some more this morning....I thinks it's better than it was but still needs some more work.....do I need to keep removing small amounts of wood over the whole limb? any help is appreciated....Steve
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Looks like to me the first 8 10 in. out of the fades till you get them a little more even.then you can work on the rest of the limb. :) It's coming along pretty good now.Go easy. :)
Pappy
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Also make sure you have it center on the tiller stick,it may just be the picture but looks like it is a little off to one side. :)
Pappy
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thanks Pappy.....I'll work on the limb some more and post pics tomorrow....steve
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Be sure to exercise it good between scraps and you might pull it down another notch after
this scraping.It might tell you a little more. :)
Pappy
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You might also start at the fades and mark on the edge of each limb a straight line with a pencil going from back to belly in 2" or 3" increments out to the tips. Then with the first line from the fades number it "1", next line "2", etc. Do this for both limbs such that for example mark number "2" on the top limb is at the same location as mark number "2" on the lower limb. Then with a straight edge ruler you can measure perpendular from the string to the belly of the bow and compare the limbs to each other. This is just another type of method to go along with using a 4" straight edge on the belly to find flat spots as already suggested... just using your eye for comparison, etc. If you think an area of the limb is flat, measuring and comparing may help you to confirm it is and help you make the decision to scrape in a certain spot. :)
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well I've been working on the tillering some more.....It's braced at 5 1/4".....should I increase the brace height??....I think it looks better than it did...but could probably use some more work.....the scales say it is about 52#'s @ 27" and 64" n/n.....take a look and tell me what needs to be done...thanks Steve
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anyone?????...If not....I think I'll finish this one up.......Steve
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I think the left limb looks great. I think the right limb is bending a little to much in the fade. Maybe go out to midlimb and take about 5 good scrapes on the right limb if you have weight to spare. If you are close to your target weight and draw length, I would say you are close enough and to stop right there. Justin
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thanks Justin.....I'm pretty close to where I want to be on draw weight...How much do you think it will drop....I guess that's hard to tell....I may take a few scrapes off anyway....Steve
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I think that left limb is bending pretty hard about a third of the way out, might scrape a few times at midlimb. I liked the bend in the right limb better. Just goes to show you how different people view these things.
I would suggest you run a short straightedge along the belly of the braced bow and judge your degree of bend by the gap under the edge. That won't lie, it'll tell you if you are getting a smooth even bend.
And when you are close to done like this, its time for a few photos of you drawing the bow. They often look different when being drawn by a human.
Its looking darned good though, these backed bows hold up very well. Whats your unbraced profile looking like?
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I'll take some more photo's tonight or tomorrow....unbraced the bow has taken about 1-1 1/2" set....I'll post more pics later...I'm glueing on a piece of deer antler for the arow rest and covering it with a wrapped leather handle.....steve
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Lennie, it just goes to show you how different things look when you come back and look later. I agree with your views. Both limbs have spots that are bending to much. But looking at it now I would say the left is worse.
Steve, take several scrapes off both limbs avoiding the marked areas. As for weight, I dont know what it pulls now so I could never venture a guess as to what it will loose. ;)
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well I scraped some more off the limbs as you suggested Justin....made a string for the bow,finished the arrow rest and leather grip.....I've shot the bow 20-30 times....shoots really well.....it ended up 50# @ 27".....which is a great weight for me....after shooting the bow I noticed 2 different spots...one on each limb that appear to be small hairline cracks....since I'm pretty new to this can someone fill me in on what's going on with this bow and tell me what(if anything) can be done....with a bamboo backing is it going to break?....can it be repaired?.....I'm going to post some pics....
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more pics.....
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Looks like crysals, tiny fractures from the wood being compressed to much. I have never had to fix them so I will let someone else tell you how to deal. It is probably in one of the areas that were bending to much right. Can you show us where it is on the limb. Also a picture of the thickness of the backing compared to the thickness of the belly wood would be nice. Justin
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Steve, those are called chrysals, those of us who work with bamboo get to see more than our share of them, when using a soft wood like red oak againsta bamboo back about all you can do is try to get as much limb workking as you can as evenly as possible. That bow is now scrap, sad to say but you got some good tillering practice in and did a pretty good job tillering it out. Don't feel bad, I had those little frets appear on several bows in december, all from the same jatoba board, nothing I could do would seem to avoid them. Steve
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thanks for the info guys.....albeit bad news....what will happen if I keep shooting this bow....will the oak belly break alone or will the bamboo snaap with it?....here are some close-up's of the limbs at the points where the crystals are....I used an arrow as a pointer.....
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You could try to saw the boo off the back so that isn't wasted.
Sorry about yer luck but it was a learning experience, now git back on that horse ;)
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Don't worry...already have....started on a piece of hickory yesterday.....Thanks again...Steve
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It does look like the bamboo was fairly thick in comparison to the belly wood. You want the boo to be no more than 1/3 the thickness of the limb. You boo wont be hurt. You can sand the wood off like Dana said and use it on another bow. It is best to use boo on real dense woods. Justin
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I don't think the bow will explode; it will just get more and more string follow and less and less draw and cast. Couldn't it be shot at a lower draw length and work?
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Been on vacation so I didn't get on this early enough apparently. Looked to me that you needed to get more near handle wood bending. You still should to relieve the chrysalled area. What I usually do is mark on the side where I want the bending to start and then work there until the wood is bending. Your bow chrysalled because it was bendiing too much in that area. Get more near handle wood bending. IMHO. Jawge
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Hey there, technically you are able to do a pretty good job both in tillering and and laminating. Please don't take this wrong, I love working red oak and have sold a bucket load of my Paddle Bows in red oak to maybe close to 200 people over the years, but you may want to consider another base wood for a boo bow. I'm sure this will be a great bow and it could be even better in some ways if you matched the boo with a wood stronger in compression. I make it a point to stay clear of message boards because of all the bow politics and stuff, so I hope this doesn't come off as negative.. You made a really nice bow. John
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Chrysals happen at a weak spot that is bending harder than the area just inside/outside of it. The node on the boo made that area especially thick, pluss it looks like the boo was thicker there anyway. I actually grind my boo backing down a little extra at the nodes, not a bunch but you are already fighting the extra thickness at the nodes and you want to avoid exagerating that.
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It sounds like I would have been better to have ground down the thickness of the bamboo before glueing to my belly wood....the only reason that I was using Red Oak was because it's alot cheaper to use to learn what I'm doing....I've since found a place to get Hickory and Ash boards fairly cheap so maybe I should try that next....So my final question on this bow is....Should I try to work the limbs on down thinner and use as a lighter poundage bow or save the bamboo backing and trash the rest.....are the crystals too deep to do this?? thanks for all the help that everyone has gave....Steve
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If it was me I would start over, save the boo and maybe get a hickory or osage slat for the belly.
Just my opinion though, its your call.
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I would star another. The crysals go most of the way through the oak. You can save the boo if you want to or you can go shoot the sucker till it wont shoot any more. ;D I don't think it will break, but the hinges will get real bad and soon it will be a 20# bow. I don't think I would back ash with boo either, maybe the hickory. What width is the boo. If it is to narrow, you might be better off to use it on Osage or some other really dense wood. Justin
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the bamboo was originally 1 3/4" wide.....I have a second piece of boo to use....I think I'll move on to osage or hickory....I may just hang this one up as a dust collector....thank for all the help and opinions....Steve