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Main Boards => The Bowyer's Bench => Topic started by: bownarra on January 19, 2022, 04:51:01 AM
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Can't get my lam stack calculator to work until I pay microsoft some money....:0
Can anybody give me some numbers for the new stack please.
Original stack - 0.286" - 42#
Looking for 49# off the form on this one.
Thanks in advance.
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42/49 = 1.16 cu. = 1.05 x .286 = .300
I also have used the stack calc. Most times they a right on or a couple thousands difference.
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Many thanks for that .300" it is.
Just off to grind that last parallel lam to get the stack dead on.
Will post some pics when I get her done :)
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42/49 = 1.16 cu. = 1.05 x .286 = .300
I also have used the stack calc. Most times they a right on or a couple thousands difference.
X2
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😲🤔 stack calculator. Didn't know there was such a thing. JF
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(https://i.imgur.com/pEdFIoq.jpg)
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😲🤔 stack calculator. Didn't know there was such a thing. JF
Yup that's what ole KennyM uses. Ya didn't thunk he wuz dat smart did ya?
LOL
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Ughh...Ugh... I missed something...
The additional data in the bottom of that chart says that increasing riser length will increase bow weight....
That is backwards...
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Not really...you are shortening the working limb.
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She is in the hotbox now :)
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Ughh...Ugh... I missed something...
The additional data in the bottom of that chart says that increasing riser length will increase bow weight....
That is backwards...
????
I think it's correct. It’s the equivalent of shortening the limb.
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Ok, as long as bow over all length stays the same? I know for a fact on take down bows that longer risers of bows with same limb length makes weight less and vice versa.
My medium limbs on my 25" riser pull 30 lbs.
On my 17" riser, they are 38 lbs.
I guess "all other things being equal, refers to over all length". I took it the other way, all other things being equal such as limb length being equal...
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So does this stack calculator work for longbows also. I like to keep my fade outs about no less than 1.090
My original stack .430 original pounds of 42 desired weight 45 lb what would it be? Math was never my favorite subject. JF
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So does this stack calculator work for longbows also. I like to keep my fade outs about no less than 1.090
My original stack .430 original pounds of 42 desired weight 45 lb what would it be? Math was never my favorite subject. JF
.440
This is for glass bows only I think, R/D and long bows, seems to work on recurves too.
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If you have Microsoft excel
I think all I have to do is copy it and send it to a email, and you open in Excel
If anybody want's it?
BJansen is a member here and he sends it out to us :thumbsup:
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.440 is what I used and it will end up 45# I'm almost there now.
Mine was just a guess going off my records from previous longbows built. JF
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Here is more Info he gave me
1/4" narrower limbs = 14% loss in weight--55lb x 14%=7.7lb
I went from 1-3/4" wide to 1-1/2" wide on a recurve and got 8.5#--55# to 46.5# :thumbsup:
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Ole kennym don't even know how to excel at Microsoft... :laughing:
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Ole kennym don't even know how to excel at Microsoft... :laughing: me neither
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Ole kennym don't even know how to excel at Microsoft... :laughing:
Me nitter:)
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I would like to have it.
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I would like to have it.
I sent it to you
Let me know if it works Bue
I'm not a big computer nerd so I don't know if it will work :pray:
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This may work too
http://www.mediafire.com/file/ckul4wdru1oq97o/Stack_Calculator.xls/file
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Thank you Max. Will see tomorrow if I can load it up to Exel.
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Thank you Max. Will see tomorrow if I can load it up to Exel.
:thumbsup:
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I think all I have to do is copy it and send it to a email, and you open in Excel ?
If possible, could you please send that to me? I’d like to see how it compares, if my iPad will open it.. its supposed to I think.
Thanks!
Noah
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My phone opened it but I only got the lower half on an Excel graph sheet. I can't read anything on the top to slightly left of what I got. JF
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.440 is what I used and it will end up 45# I'm almost there now.
Mine was just a guess going off my records from previous longbows built. JF
Changing limb width is linear. IOW, a limb 2" wide and 50# would be reduced to 25# if the limb were reduced to 1".
As regards limb thickness, the changes in thickness effect draw weight with a factor of eight.
I have two stack calculators and they both function based on that math. They aren't perfect but they are very very close.
For the type of bows that you mostly build, as do I, the Bingham chart is very close but you have to remember that it's based on the width of the Bingham design. But, it's very easy to use the linear aspect of the width formula to calculate weight.
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I think all I have to do is copy it and send it to a email, and you open in Excel ?
If possible, could you please send that to me? I’d like to see how it compares, if my iPad will open it.. its supposed to I think.
Thanks!
Noah
Reply #22 has a link
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For these things to work you have to have a bow already built and know its stack. Everything the same except the stack. I have found that if the desired weight is is a bunch more say 20 lbs. you might be off some.
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For these things to work you have to have a bow already built and know its stack. Everything the same except the stack. I have found that if the desired weight is is a bunch more say 20 lbs. you might be off some.
I found the same. Using 1# for every 003 seems to be pretty much the same.
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I think all I have to do is copy it and send it to a email, and you open in Excel ?
If possible, could you please send that to me? I’d like to see how it compares, if my iPad will open it.. its supposed to I think.
Thanks!
Noah
Lets see if the copy for Bue works
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(https://i.imgur.com/pEdFIoq.jpg)
That’s a good calculator but….. that other good data info on the bottom is bogus.
Lengthening a riser with the same limbs will decrease the draw weight, not increase it.
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Ok so how does the calculator work. Need to show your work, to come up with the boom. JF
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Ok so how does the calculator work. Need to show your work, to come up with the boom. JF
Bending stiffness of a rectangular section beam of a homogeneous material is proportional to the thickness cubed. The calculator uses that to calculate the new stack height. It isn't strictly accurate because the fibreglass lams carry much more of the load than the core material, but it is close enough to accurately predict small changes in weight.
Mark
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Ok so how does the calculator work. Need to show your work, to come up with the boom. JF
Weight increase % =(C9-C8)/C8
Target Stack increase =-(1-(POWER(1+C10,1/3)))
Target Stack Thickness =C7*(1+C11) Boom
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Ok so how does the calculator work. Need to show your work, to come up with the boom. JF
Weight increase % =(C9-C8)/C8
Target Stack increase =-(1-(POWER(1+C10,1/3)))
Target Stack Thickness =C7*(1+C11) Boom
Phew. Finally someone simplified it. :biglaugh:
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Oh yeah now I get it 🤣🤓 much easier to understand
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Bow came out right on inteneded weight. One veneer moved so had to narrow it a mm or two more than I would've wanted but hey....I've still hit weight and she has pretty limb edges now haha...
Osage and Honduras Rosewood - not too shabby.
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I was able to move it to Exel and could plot in the numbers I wanted, but I can’t make it calculate. I have to find someone who knows this stuff.
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Yeah clear as mud.
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Phew. Finally someone simplified it. :biglaugh:
You need to calculate the % increase (or decrease) in weight you want, then take the cube root of that to get the percentage change in the stack height.
For example:
Existing stack is 0.500", weight is 50# @ 28". Say we want the new bow to be 55# @ 28".
% change in weight = 55/50 = 1.10
Take the cube root of that = (1.10)^1/3 = 1.032
New stack height = 0.500 x 1.032 = 0.516"
Works the same way for reductions. Say we want the new bow to be 45# @ 28" instead of 55# as above.
% change = 45/50 = 0.90
Cube root = (0.90)^1/3 = 0.9655
New stack = 0.500 x 0.9655 = 0.483"
I was able to move it to Exel and could plot in the numbers I wanted, but I can’t make it calculate. I have to find someone who knows this stuff.
That is bizarre, it should automatically recalculate when opened in Excel. Do you want to try the copy I have? I could email it direct to you if you want.
Mark
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Yes Mark, that would be great. I sent a PM
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Yes Mark, that would be great. I sent a PM
Email has been sent. Hopefully this one is more successful for you.
Alternatively, you could use the method I showed above with a scientific calculator to crunch the numbers if this file won't work either.
Mark
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It works, thank you. :)
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The cube root method is what I us .
You can Google cube root calculator that will ease your brain. :bigsmyl:
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Like I mentioned. I'm not good at math. I'll use my bowyerscore math. Time X's trial and error - a few errors + keep records ÷ 1 decade ## = I'll stick with how I've been doing it.✓ works for me 😂🤣🤓
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Sorry Bue
I must have missed something :knothead:
Did anyone try the link I posted on Reply 22
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Sorry Bue
I must have missed something :knothead:
Did anyone try the link I posted on Reply 22
I just downloaded it and it works for me. Ad Aware did give me a security warning for that page, though.
Mark