Primitive Archer
Main Discussion Area => Bows => Topic started by: Sempertiger on March 08, 2012, 04:51:37 am
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I just wanted to post where I stopped for the night. This is a 68" NTN Merbau pyramid bow. 2" at the fades down to 1/2" at the tips. It's backed with three layers of pure linen..
I still Have a couple inches left to get everything looking right. but what do you think?
(http://i244.photobucket.com/albums/gg20/sempertiger/IMG_6824.jpg)
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The outer limbs are very slightly too stiff, and there's a flat spot on the right limb just past midlimb.
Someone with better eyes should correct me if I'm wrong.
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I agree with arjun. Especially the right tip looks to stiff to me. When you're checking the bows tiller I would make sure that the bow is level, makes things easier if you ask me...
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Maybe a little flat mid right limb and yes the outer limbs are a little stiff, some want
them to work more,I personally like mine a little stiff at least the last 6/8 inches so that don't look that bad at all to me. :)
Pappy
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Take a 6" straight edge and slide up and down the belly of your bow while it is braced. If the gap lessens you scrape there.
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Maybe a little flat mid right limb and yes the outer limbs are a little stiff, some want
them to work more,I personally like mine a little stiff at least the last 6/8 inches so that don't look that bad at all to me. :)
Pappy
I am also one of those who like the last 6" or so to be a little stiff, or rather I don't have a problem with it. It helps ease stacking, makes a slightly smoother draw. To me, the tiller doesn't look that bad, if I had to guess I would say the left limb is the stronger limb, and is causing the right limb to have potential hinges from being stressed more. (But that is just a guess, :laugh:) One potential spot to have a hinge looks to be right off the fade, and the other one about 6" or so from the tip. When it gets this close I think that judging a picture can be a bit harder and sometimes give not as good a idea of the tiller as really looking at the bow in person, so I don't know, and I could be wrong. Sometimes I think shadows play tricks with my eyes, even when I am tillering a bow with the shadows bouncing off the wall behind my tiller in my work room... Good looking work though! :laugh:
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Toomany have a look at the two trianlges the string, limb and tiller board makes. Do you see how the right side trianlge is larger? Thats generally the stiff side. And is clearly is this time around. I still say draw it by hand for the truths, the tiller stick and tree wont tell you much except glaring errors.
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Toomany have a look at the two trianlges the string, limb and tiller board makes. Do you see how the right side trianlge is larger? Thats generally the stiff side. And is clearly is this time around.
I think you got that one mixed up a bit. :laugh: But ya, of course you can't know for sure unless you draw it.
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Got what mixed up?
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The larger triangle is the weaker limb not the stiffer limb.
EDIT: Or maybe I got it mixed up. My brains not working too fast today.
EDIT#2: Yes, actually, the larger triangle would be the weaker limb, not the stiff one. Had to step back and think about that one for a sec. :laugh:
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Mr Tiger your right limb is stiff mid way, your left limb is darn close.
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Mr Tiger your right limb is stiff mid way, your left limb is darn close.
On this bow it is hard to tell, but in general if the "triangle" that is formed of a bow on the tiller is bigger, it means the limb is weaker and working more compared to the other limb. Just think if the bow was braced Pearl, and you made a "triangle" of a braced bow, the bigger one would obviously mean the limb was weaker. Can someone else please chime in/help a brother out here? LOL
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we're being quite critical, it bends fairly evenly and one of your limbs is stiffer, i just cant tell which one :laugh:
I'd probably just shoot it a dozen times or so and check tiller again. thats just me though
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we're being quite critical
True that.
EDIT: I agree that this bow is slightly stiff tiller wise on the right limb mid limb, but only a bit. What I was talking about is which limb is stronger (or more likely to be stronger) if there was any confusion. And not really talking about this bow but bows in general. Like I said I was guessing, and that it is hard to tell from pictures when the bow is this close to tillered. And it is a very nicely tillered bow. Sometimes I believe it is easy to go from helpful critical, to unhelpfully cynical, so I apologize if I was more of the later. If it was me, I would be happy with the tiller without thinking twice and make the weaker limb the top limb. Although it takes a while to get there, there is a line between perfecting a bow and just pointlessly inducing set by removing weight.
Pearl, you can see that the bow is tilting upwards to the right, and like you said the right side has a bigger triangle. This indicates the limb is weaker and working more on the right, coming to an asymmetrical balance similar to what you would see in the braced profile.
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I am an admitted rookie, but looks to me like the bow isn't level on the tree, tilting very slightly left. That would also make the right "triangle" a little larger.
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Slow day at work. So I've spent the last couple hours playing with my crooked picture and came to some realizations:
1. like many have said, the right limp has some flat spots, stiff mid limb, or the left limb has a bit of a hinge. I need to check it with a straight edge.
2. the right limb is the weaker limb, (pulls about an inch more than the left one.
3. The right limb is about an inch and a half longer than the left limb (still trying to figure out how I did that).
I stole this trick from Pearl Drums, without his knowledge, SHHHHH, don't tell him >:D... I took the image, selected a portion of it with the bow in it, mirror imaged it, made it kinda transparent and superimposed it on the original image. I had to do the whole bow because I found that one of the limbs appeared to be longer than the other when I did only one, so I did both and made the tips on both sides and the back of the handle match up. (I'm going to take a tape measure to it when I get home and make sure the image isn't hosed)
important note, the lower weaker limb is the limb on the right from the original image.
(http://i244.photobucket.com/albums/gg20/sempertiger/compare-1.jpg)
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Get your limbs evened up lengthwise before you go farther. Unless you want a shorter bottom limb as some guys do. Your right limb shows weak becasue its longer. If you equal the lengths out you will find that right limb is more stout due to flat spots and such. Equal them with a saw, not your computer. It may look even when photoshop an inch off. But that didnt change the bend qualitys of that limb, only the picture.
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I'm going to take a look at it with a tape when I get home and see how it looks. Not sure if I'll equal them out or power limb it, if it is off.
Equal them with a saw, not your computer. It may look even when photoshop an inch off. But that didn't change the bend qualitys of that limb, only the picture.
I didn't remove anything from the picture, I aligned the back surface of the handle vertically then moved mirrored section left and right horizontally till the limbs on the left were the same as the limbs on the right. this is shown with how badly the handles match up in the middle. As you implied, removing length in the picture won't show the outcome in real life. I would guess that by removing an inch and a half from the right limb with a saw would result in a significantly stronger right limb.
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Sometimes where the tips land isnt always an indicator of limb strength. Hopefully you dont feel like Im beating you up here. I swear its not my goal. When you start nit picking tillers you start filling your rack with good bows that will last a long time. Skip little details here and there and you heat your shop with them 0-1000 shots later!
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I've got thick skin, any criticism is a learning experience. I just wanted to make sure you didn't think I was a complete idiot. Keep in mind, this is my third bow, and first one over 15lbs
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Get your limbs evened up lengthwise before you go farther. Unless you want a shorter bottom limb as some guys do. Your right limb shows weak becasue its longer. If you equal the lengths out you will find that right limb is more stout due to flat spots and such. Equal them with a saw, not your computer. It may look even when photoshop an inch off. But that didnt change the bend qualitys of that limb, only the picture.
According to you 5 or so posts ago the left limb "clearly" was the weaker one, for some reason. ??? If the braced profile is fine, there is no reason to go chopping limbs shorter.
"I would guess that by removing an inch and a half from the right limb with a saw would result in a significantly stronger right limb."
It definitely would. If the weaker limb is too weak I would recommend tillering the bow to meet the weaker limb. You want to leave one limb just slightly stronger than the other though, and always make the stronger one your bottom limb. This is because the bottom limb is under slightly more stress than the upper limb. Over time, (sometimes) a bottom limb can become weaker from being stressed more, and make the bow uneven and unshootable. Especially if a bow hasn't been shot in yet. The easiest way to tell which is the stronger limb, if both limbs appear to be perfectly even, is to shoot the bow and see which way it shoots best. Can you post a braced pic semper? Oh, and one layer of 100% linen fabric should be enough for bows up to 50 - 55 pounds, maybe 60. I have made lots of 60# linen backed bows with one layer of 100% linen from jo ann fabrics. Although most people on this board consider 60#'s for a linen backed bow pushing it. That heavy glue on the linen is gonna slow down your bow alot. For your third bow it is a very nice tiller job! I foresee many more nice bows from you in the future!
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I've got thick skin, any criticism is a learning experience. I just wanted to make sure you didn't think I was a complete idiot. Keep in mind, this is my third bow, and first one over 15lbs
I never thought for a second you where an idiot! Thats not me. Keep on building man.
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"3. The right limb is about an inch and a half longer than the left limb (still trying to figure out how I did that)."
Didn't catch that. I know alot of people will make their handle an inch off center, which makes the nocking point, if right above the handle, about center. I've tried to start making mine that way so my handles don't always look so weird, but I just never can go through with it for some reason,... it's just a habit to center the handle for me. I need to break it someday. ;D
Pearl, you are wrong about the "bigger triangle" being the stronger limb. A bow will tilt like that when one limb is weaker, I'm sure you will sit back and be like "duh" when you think about how many bows you have made that might have done that when tillering. I feel I owe it to you to make sure you understand this as you always feel so obligated to correct me.
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She broke shortly after taking this photo...
(http://i244.photobucket.com/albums/gg20/sempertiger/IMG_6828.jpg)
I was holding it at 27" and 55lbs, making sure the tiller was ok, and I heard a crack, and suddenly The left limb delaminated at one of the courser grain lines mid limb and mid thickness for about 3 inches and before I could even start to let it down, the left limb completely separated and flew away...
At this point, I'm inclined to agree with Dark Soul about a post he made on a different thread. Merbau doesn't really have the qualities of a good bow wood. It's a diffuse porous wood, but the early and late wood are all kinda nasty.
(http://www.wood-database.com/wp-content/uploads/merbau-endgrain.jpg)
Oh well, I learned quite a bit on this bow.
1. don't trust your camera. the limbs were exactly, to the 1/16th", equal length.
2. Though it makes decent lighter weigh bows, Merbau should not be used for heavier weight bows (I think anything over 25 or 30 lbs is too much for it)
3. Heavier bows seem easier to tiller than light bows (less material to remove)
4. my tillering tree is too short to pull a bow to 28" with the clip attached to it. I need to lengthen it.
Time to move on to the next Project :) I'll post pictures when I get it ruffed out. Just not quite sure what to make my next one out of, but I'm leaning toward the new stick of Alaska Yellow Cedar that I picked up yesterday.
Cheers
JS