Primitive Archer
Main Discussion Area => Bows => Topic started by: burtonridr on January 30, 2017, 11:09:18 pm
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I'm working on a pyramid bow.... And I'm pretty sure I've got a major hinge on the top limb right off the fades. But I'm having a really hard time telling if it is actually a hinge, or if it just looks that way because of the shape of the wood. The top hinge leaves the handle slightly angled towards the string. But the pics and the tiller jig seem to be telling me it needs some shaved off the mid to upper mid limb.
I have a couple questions,
-Can it be saved? I've already pulled back to full draw because at 20" everything was looking really good.
-What are the cracks on the belly? Compression failure?(see pics) They are right at the fades on the belly. I did heat treat the belly.
-Can the cracks be fixed? Will wrapping with thread and super fix this problem?
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Here are the belly cracks
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Looks like it's toast. It's only bending in the fades. How thick are your limbs? Learn from it and build another! Cheers- Brendan
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Upper limb near the handle is doing way too much work. You can save it if you reduce the weight in the bottom limb and get the upper half of the top limb bending. Then match the bottom tips.
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it's at least chrysalling, if not worse
did you trap the back?
r/d pyramid? Someone said r/d bows should have even width limbs for the first 1/3 or 1/2 :-\
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What did you use to bend the recurves? It looks like you have two indentations where the recurves start... maybe you used a hard corner of a work bench or something? My eyes could be playing tricks. She's firewood either way I'm afraid. Onto the next!
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I've never had any long term durability luck with a limb or limbs that have chrysals or compression fractures as you've got there.I'm not saying it can't be done but it'll be a lot lighter weight bow in the end.I'd say just to scratch it up to experience and start over.It got pulled too far to save now IMHO.Parallel limb widths to mid limb for an R/D next time too.Plenty wide also.Flat belly and a little shorter draw length too for the length of bow there.
If a pyramid is wanted an Ishi style bendy handle would work a lot better at the draw length you want for the length of the bow you got.Starting out very wide with a flat belly also.
Either style would work but combining them does'nt IMHO.At least not with maple anyway.Might hold up a while with osage but I would'nt bet on that either long term.Good learning experience though and just my two cents worth of experience.
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Well, look on the bright side, you've learned what chrysals look like and where they form. On to the next one.
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I'm afraid she's on her way out. Not a terrible effort, though. I see what you were going for in the strung profile.
Strictly, the minute you flipped those tips to reflex, it was no longer a pyramid bow and required a different tiller. If you started with pyramid "specs" like an even side taper and essentially even thickness, that little reflex in the tips pushed all the strain, and hence the bend, toward that inner limb right off the fades.
I've done the same a couple times (at least) early on. Next time, if you keep that front profile, you have to adjust thickness along the limbs, going much thinner mid-limb, say the middle 50% of each. Currently, all the bend is right off the fades, in the first 25%, and concentrated in the first 15%. Right where the frets are.
Keep it up, though!
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I'm afraid she's on her way out. Not a terrible effort, though. I see what you were going for in the strung profile.
Strictly, the minute you flipped those tips to reflex, it was no longer a pyramid bow and required a different tiller. If you started with pyramid "specs" like an even side taper and essentially even thickness, that little reflex in the tips pushed all the strain, and hence the bend, toward that inner limb right off the fades.
I've done the same a couple times (at least) early on. Next time, if you keep that front profile, you have to adjust thickness along the limbs, going much thinner mid-limb, say the middle 50% of each. Currently, all the bend is right off the fades, in the first 25%, and concentrated in the first 15%. Right where the frets are.
Keep it up, though!
Crap that is exactly what happened.... And explains why it tillered out so nice until the very end (when I flipped the tips). :-\
I took all kinds of measurements and just could not figure it out, everything was real nice and even. I was concerned to start shaving off to much mid limb, I've been to hasty in the past and suddenly had a bow 20lbs under weight real fast. I didn't realize that by flipping the tips I would increase work on the lower parts of the limb and completely mess with the tiller. I figured the upper limbs would still be working through the draw as before, just a slightly different shape. I will keep what you said in mind on the next one and reduce the limb thickness accordingly.
I really appreciate all comments, at least I know what happened. I will experiment with this thing until it fails, maybe learn some more in the process.
Good thing I still have the other half of this log to work with, and I like building them almost more than I like shooting :)
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I've never had any long term durability luck with a limb or limbs that have chrysals or compression fractures as you've got there.I'm not saying it can't be done but it'll be a lot lighter weight bow in the end.I'd say just to scratch it up to experience and start over.It got pulled too far to save now IMHO.Parallel limb widths to mid limb for an R/D next time too.Plenty wide also.Flat belly and a little shorter draw length too for the length of bow there.
If a pyramid is wanted an Ishi style bendy handle would work a lot better at the draw length you want for the length of the bow you got.Starting out very wide with a flat belly also.
Either style would work but combining them does'nt IMHO.At least not with maple anyway.Might hold up a while with osage but I would'nt bet on that either long term.Good learning experience though and just my two cents worth of experience.
Thanks, this helps. I will keep this in mind on the next one and keep the limbs wide out to mid limb.
I'm not a fan of pyramid bows, this is my third try at one.... first one broke, second came way under weight, this one fractured due to poor design and planning. lol, not my cup of tea.
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Looks like it's toast. It's only bending in the fades. How thick are your limbs? Learn from it and build another! Cheers- Brendan
They are a little over 1/2" thick for the entire length
it's at least chrysalling, if not worse
did you trap the back?
r/d pyramid? Someone said r/d bows should have even width limbs for the first 1/3 or 1/2 :-\
I'm not sure what you mean by trap the back?
What did you use to bend the recurves? It looks like you have two indentations where the recurves start... maybe you used a hard corner of a work bench or something? My eyes could be playing tricks. She's firewood either way I'm afraid. Onto the next!
I used a piece of the log I cut this from.... I heated the portion with my little buddy propane heater with a wet piece of paper towel draped over it for about 5 to 10 minutes, bent a little, then repeated until I got it where I wanted it.
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I like pyramid bows best. But if you do leave them the same thickness all the way to the tip, the limbs will always bend more on the fade end that at the tip. It's because we can't actually taper the width to a point. So, we have to thin the limbs from about the middle to the tip, tillering as with parallel limbs.
Your thickness was probably about right, but longer limbs and more thinning as I said would have helped.
It's possible to cure chrysals by replacing the wood, but not worth the effort on maple unless you just want the practice. Here's a picture of replaced wood on the belly of an Osage bow.
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You could try peanutbutter and jelly on it, because as it has been said by others, it it toast. On the other hand, it's a lesson learned.
I had real problems with my first half dozen pyramid bow, too. And it was all pretty much what you are looking at here...top much bend too soon out of the fades. I now use a machinist's caliper to carefully measure thickness down the limbs with a goal of keeping everything within 10-15 thousandths of an inch until the limbs begin to bend a little for floor tillering. At that point, I thin the tips a little and start long string tillering. The bow starts out whip tillered when you are beginning to tiller on the tillering stick or tillering tree. Each inch of added draw as I tiller movesme to take wood off closer and closer to the fades. Clear as mud?
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You could try peanutbutter and jelly on it, because as it has been said by others, it it toast. On the other hand, it's a lesson learned.
I had real problems with my first half dozen pyramid bow, too. And it was all pretty much what you are looking at here...top much bend too soon out of the fades. I now use a machinist's caliper to carefully measure thickness down the limbs with a goal of keeping everything within 10-15 thousandths of an inch until the limbs begin to bend a little for floor tillering. At that point, I thin the tips a little and start long string tillering. The bow starts out whip tillered when you are beginning to tiller on the tillering stick or tillering tree. Each inch of added draw as I tiller movesme to take wood off closer and closer to the fades. Clear as mud?
Your description helps a lot, it sounds a lot different than tillering the two bows I built that didnt break. They werent pyramid style, one was an ishi paddle bow and the other is a standard r/d long bow. So, how the heck do you know you are going to hit your goal weight? at least in the beginning, say first 10 to 15 inch of tillering? It sounds like it would be super light out to about 10 inches, does it stack different?
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Learning to gently "floor tiller" helps. That is when one tip is on the bround, the other tip is in your hand, and the remaining hand pushes on the handle section. You are just barely trying to get a hint of bend in the limbs. From there, long string tillering. the string goes from nock to nock but does not require the bow to be bent to get the loops into the nocks. Now you can use a tillering tree or a tillering stick to pull the bow just a few inches. And when I say few, I mean starting with two inches, three at the most. Scrape a little wood off the flat portions of the limb and again test the tiller.
Ideally, you should have the bow coming to a beautiful and appropriate for design arc when your long string tillering is pulling the bow about 10 inches or so. Then you can put on a shorter string. As you tiller a few inches at a time you should hit full draw around the same time as you hit the intended weight of the draw. Maybe even sooner!
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Looks to me like you have a little thin spot right at the hinge area, either way Sorry to say but I would
cut it up and cook Brats with it. I always stay mostly off the fads area until the last few inches, they all want to bend there when you first start bending them, just natural, it wants to bend in the center. :)
Pappy
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MMM...Brats
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It would be interesting to see a front profile just for the heck of it.
I agree it is a good lesson, but knowing myself, I would probably shorten it a few inches, scrape it way down to a kids bow with a shorter handle and spend way to much time fixing it instead of moving on ::)
Good luck any way you go.
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Guess this is the first time I've disagreed with you in a big way Pappy. Brats have way too much fat and cholesterol. ;)
Jim Davis
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:D :D :D Mine are Venison Jim with little fat. ;) :)
Pappy
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So let's talk how to avoid hinges, which is what I see just off the handle on the upper limb.
This is for a bow with parallel limbs. Not pyramid of which I am not a fan for beginners. Getting the tiller right for that limb shape is difficult.
First and foremost, rarely confine wood removal to one area, count your strokes and check tiller often.
Second, a handy way to make sure you get a decent taper is to measure off the limb in 6 in. increments. Get an outside caliper. Just off the fades, I start at 3/4" or a little less. Probably too this but you can't put wood back.
Give the dial a turn, slide it to the next 6 in. mark and remove wood until it fits. Continue.
Then you can begin to look tiller.
Perhaps, stick with straight limbed bows until you get some experience. Also, go to the Bow of the Month club and look at the tillers of bows.
Check my site.
http://traditionalarchery101.com
Jawge
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I like pyramid bows best. But if you do leave them the same thickness all the way to the tip, the limbs will always bend more on the fade end that at the tip. It's because we can't actually taper the width to a point. So, we have to thin the limbs from about the middle to the tip, tillering as with parallel limbs.
"Eiffel tower" limb tips are probably best :P
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Doing what George says for parallel limbs will get your bow to brace from floor tiller every time in good shape not stressing the limbs any.
Doing what ash arrow says for pyramids will put your pyramid bow where it should be for tiller too.
Doing what loon says about the tips can be learned later but work great too.
Doing what Springbuck says is on the money too.
Doing JW's method works great too.
Doing what Pappy says can get you some fulfillment from it yet anyway at the moment.
Dong what DuBois says might be worth your while too if so inclined.
Sorry if I left some fellas out.
Some smart fellas on here.I'd take their advice.
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Asharrow has a good point. I approach the pyramid thickness differently, but it's true that an exact consistent thickness will make the pyramid bend more toward the handle, less toward the tips.
When you mark out the dimensions of a pyramid bow, since, as Ash said, you can't ACTUALLY, taper to a point, most guys just mark the sides, tapering to a 3/8"-1/2" wide tips. In this case you will need a slight front/back taper to make the limb bend evenly.
I usually DO mark the sides taper to a point. Then, I add some width to those last few inches with parallel sides. So, the side taper ends, say 5-6" from the tip, and the sides become parallel. This let's me not have to specifically try to taper the thicknesz, but as I tiller, I end up doing it anyway, working the bow toward tiller.
BTW, the best way to hit draw weight is to pull the bow only about that hard as you tiller. If you want a 50 lb bow, only pull the bow on the tillering tree with 50 lbs of force. Lots of guys use a spring scale to do this. I have a pulley system to watch limbs bend, but I also have a bar and weights from an old barbell set I hang on the string and step back. Early on this will only bend the limbs a bit, but that's ok. Correct what you can see, and check again. The weight will pull it 3", then 5", then 8", etc. By the time it's pulling a real string 20" or so, I'm usually happy with the bend, and just have to bring it in.
Lastly, "trapping", is the practice of reducing the limbs to a trapezoid cross section, the back being narrower than the belly, and the sides angled. Most woods are stronger in tension than compression, so you help the belly a little doing this. It also reduces physical limb weight while maintaining stiffness. You lose weight faster than you lose stiffness, if that makes sense.
On a pyramid bow, this might be used to take the weak inner limb/stiff outer limb problem. If you narrowed the back by 1/4" by angling the sides, you'd be removing PROPORTIONALLY more width at the tips, since the inner limbs are wider and the tips narrower. Handled properly, this might let you get away with less front/back taper.
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Oh, and what flipping the tip did is to GEOMETRICALLY stiffen that bit, which is already stiffer, so, beat up inner limbs.
Man, this is a long, boring surgery I'm sitting in on.
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Pyramid limbs are wider at the fades and narrower at the tips so why would the fades bend more?
Jawge