Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: longrifle on December 30, 2014, 12:27:00 PM
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Looking to build a 66" 55# @27" hill style
With 1" at fades to 3/8" at nocks, but want to make it out of 3 lams of boo plus glass any suggestions you guys?
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What's your riser length? Planning on 0.040 glass? Straight, backset, or string follow?
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14" riser, .040 glass, straight
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I've made a few hill styles with 4 tapered lams.
That were .002 tapered and I guess that's too much of a limb taper. So I wanted to have 1 parallel and 2 tapered but don't know where to start.
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figure your stack---figure your taper--say .005per inch = one.003 plus one.002-then one parallel on the belly ramps
I like three lam bows and try to keep the thicknesses similar-[divide by 3] true or not I feel that I have one lam in tension -one neutral-and one in compression
by the way if I'm reading your post right it sounds like you used ,008per inch IMO twice what I would try--good luck!!
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Your right Mike they were .008 per inch, that's why I want to get to a .004 per inch bow so hopefully there's a little less bend in the tip area. Do you have any stack info that you have used on your own bows?
I'm thinking I would like to have my stack as follows:
.040 glass
.002 taper
Parallel
.002 taper
.040 glass no belly ramp lam all on back.
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The number of lams shouldn't matter as long as the total stack is correct.
For a 66" straight longbow 55# @ 27" I would use:
14" riser, .005 total taper, 1 1/8" at the fades, .040 glass with a total stack of .400 measured at the fades.
Good luck and post some pics when you get her built
James
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I run .002 taper on mine [no help]
James's sounds like a good starting place to me
is that stack measurement @the butt or fade?
james do you trap that bow?
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Didn't make it to my formula book last night. James' numbers sound about right for stack at the fades, but I usually meaure mine at the butt. You will get variation with wood. I know yew for instance comes in 10% lighter for the same stack (perhaps unless it's old-growth, tight-grain yew which I hear has the opposite effect.) So be a little flexible on your final weight or just narrow up at the fades until you get to weight.
But I definitely recommend 5-6 thou taper. Otherwise you're carrying a lot of extra weight in a design like this at the tips which just makes the bow shocky. I also like trapping the limbs, especially towards the tips for the same reason.
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you are correct skyboy, :) the yew will produce a lighter bow, but yew is pretty much all old growth- well the stuff we are using for bows , that is. it is an understory tree- and grows in the old growth- and i have used stuff from 35rpi to 70 rpi- ( remembering good aircraft , or music wood grade spruce is about20 to 30rpi) seems to consistently need a 10% add to the stack- it just seems that some particular yew trees just seem to yield different results, to other yew trees- as i use more and more of it, i will get more defined answers to this, and let people know- i do believe chackworth uses a lot of yew- would be interesting to hear what his results are on using yew
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i know nothing about hill bows, besides what i have read on here- but from what i understand that hills that work more in their outer 1/3 's as apposed to closer to the fades, are better and smoother shooters- is this true Dave?, and if so, why?
but guessing that will concur with your methods of taper rate and trapping , esp towards the tips--am i barking up the wrong tree here???
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yew drives me crazy!!makes a really nice bow
...but I've been inconsistently coming in low!!!
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Canopy Boy and JamesV have good advice with a 5- 6 thou taper rate especially since its 66" and 3 lams. This is a personal choice as the bow will feel different between the two. Having built many I would opt for the faster rate. Dropping to .30 on the back would also enhance speed and add smoothness to the draw and reduce thump.
A slower taper like 4 thou will not only make a sluggish bow due to excess core material but also risk breakage due to undue stress at the belly ramps.
Also going slightly over an inch to 1" 90-125 thou will give you a more stable bow especially if you trap.
Good luck with build and lets see some pics!
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yup bamboo- i have the same problems- some will be 10% light the next might be 15%- it does seem a tad inconsistent!- trying to find a pattern???
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So from what your saying I should use 3 tapers at .002 per inch to get the proper taper rate.
I looked at a Miller ASL over the summer and it had 2 tapers and 1 parallel ?
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Here's the stats of one I made this fall
66"
14" Riser
64#@28"
.545 Total Stack
3 - .155 actionboo tapers .002 taper
and .040 black glass back and belly
1-1/8" at fades
1/2" at tips
3" .030 tip wedges
trapped back
I would think you could reduce the total stack by .015-.020 and be pretty close to 55@27
But then you want to have it 1" at fades and 3/8" at tips so maybe lean towards the .015 reduction so .530 total stack with .040 glass
Good luck, post your results
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Michels.................
Everything on your build sounds spot on except the .545 total stack. Maybe a typo or you might be doing this from memory. From my charts a 66" straight long bow with a .445 stack would be in excess of 75# and at .548 on a 68" bow you would be pulling 140#
James
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James...
My numbers are correct.
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Thank you all you guys for the info, this gives me a good place to start. Now it's time to grind some lams. I know I'll have a curly maple riser and black glass but not sure of the core woods. Thinking about bamboo but would like a contrast between the riser and lams so I might go with walnut or eastern red cedar or a combination of the 3. Any thoughts on my combo choices? Opinions?
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I have searched and referenced this post so many times to figure out a stack recipe or answer a question.
http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=011162
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I got to thinking, so I went back and looked at my last several Hill bow specs. Here are a couple that are 66" with 13.5" risers. A bit light, but shows that Ben's numbers are quite reasonable. James, I'm not sure what you're looking at to make sure we're all talking apples and apples here.
Exhibit A: 0.524 total stack at the butt yielded a 44@28 bow with 0.005 taper and 0.043 glass, 1.15" at the fades to 0.47 at nocks.
Exhibit B: 0.536 stack w/ 0.043 glass and 1-1/8 at the fades yielded 50@29.
For reference that we're definitely in the over 1/2" stack ballpark: I also have dimensions on a Big 5 built by HHA. It was a 15" riser and 70" nock to nock, but was 0.0066 taper and 0.603 total stack at the butt, or about .59 at the fades. It was marked at 65#, but measured about 60.5@28 on my scale.
I've got a bunch more, but that's what is in front of me at the moment.
-Dave
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I'm gluing up the form for one of these today.
Just out of interest are you going to be tapering width in straight lines from the fades to the tips?
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Michels/canopyboy
The chart I was using is the Longbow chart posted by Bingham. Their chart says a 68" longbow with a .435 stack will produce a 70# bow. The chart doesn't give taper rate, limb width or riser length. The chart that Michels posted gives all the details of the build and if it is measured from an actual bow then it has to be correct. I recorded your numbers and specs to my personal book.
Thanks Guys for your post and you probably saved some of us from a very disappointing build,
James
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4 lams 0900 tapered 001 (3 on back of riser, one on belly), .040 glass may get you close
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I'm currently making a hill bow at 66 tip to tip though. I went with bamboo core and my stack I figured would be .475 and I am looking to reach 45# at 28 inch draw. My bow is 1.25 wide right now but at the end I figure I will be around 1 1/8 wide at the end of the riser to .5 tips. I really round the heck out of my edges so I always make my stack a little thicker than what I need. I'd rather take away more than not have enough. I am about to cut the nocks in and I will let you know where I stand now later on maybe tonight.
Good luck!
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I just finished a longbow [HH style] and with 1 x .o40 black glass, 1 x .043 clear, and 4 lams each .001 taper the total stack was .525. Result was 50# at 28'' and 66 NTN.