Author Topic: Mass principle handle mass and working limb, help  (Read 1435 times)

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Offline redbow22

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Mass principle handle mass and working limb, help
« on: January 31, 2018, 06:45:01 am »
Hi everybody,

I have been reading carefully Steve Gardner article in TBB vol 4 again and again. I am not shure about my target mass ...

There are some things i don't understand :

This is my fourth osage 61" recurve, it is significantly lighter ( i don't tell the weight on purpose) than the previous ones probably because i managed to reduce outer limb mass.
(Despite this it has some hand shock with 9 gpp arrows.)

But handle width and thickness are not the same everytime and can easily make a one ounce weight difference...

I don't understand also : Draw length/ working limb length

Considering Draw length/ bow length standards for example :

Standard : 26"/62"
minus, 8"handle fades, minus 12" stiff tips equal 42"/2 =  21" working limb versus 26" draw length

I mean that draw length ALWAYS exceeds working limb length on stiff handle bows so correction must ALWAYS be added to the chart ??

I would like to know what would be the target mass on this bow :

Osage recurve bow 61" 47,5#@26"

Handle and fades : 8"
Here handle is : 4,92" long, 1,26" thick, 1" wide.
working limb 19 or 20" not shure about that ...
String follow : zero, right after unstringing.

limb width fades : 43 mm (1,7")
limb width mid : 31 (1,22")

See page 92 TBB vol 4 :

CHART :
 61" 48#@26" = 17 Oz

A draw weight : -0,5oz
B handle fade : 0
C induced reflex : recurved (about 2inches) yes but now 0 reflex so ?
D Draw length/ working limb : 26/19 or 20 = + 3,5 Oz or 3 Oz

Something between 19,5 or 20 ?

Thanks for your help !
Jérôme   
Location : France

Offline redbow22

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Re: Mass principle handle mass and working limb, help
« Reply #1 on: January 31, 2018, 06:53:51 am »
Do i really need to fill the 7 parts verification every time i post ?

I heard there was a mass calculator, i found a dead link, nothing else .. is it still on line somewhere please ?

Thanks !

Jérôme   
Location : France

Offline Selfbowman

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Re: Mass principle handle mass and working limb, help
« Reply #2 on: January 31, 2018, 07:05:22 am »
I don't know about the mass theory but that is a nice recurve. Arvin
Well I'll say!!  Osage is king!!

Offline Pat B

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Re: Mass principle handle mass and working limb, help
« Reply #3 on: January 31, 2018, 07:18:26 am »
Welcome Redbow. You might only have to put up with the verification a few more times. We did this to get rid of spammers.
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline PatM

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Re: Mass principle handle mass and working limb, help
« Reply #4 on: January 31, 2018, 07:22:02 am »
Steve has revised his mass theory so  I wouldn't get too fixated on that.

Offline redbow22

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Re: Mass principle handle mass and working limb, help
« Reply #5 on: January 31, 2018, 08:45:49 am »
Thanks Arvin, Pat B and Pat M !
Jérôme   
Location : France

Offline barebo

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Re: Mass principle handle mass and working limb, help
« Reply #6 on: January 31, 2018, 12:32:57 pm »
I second the nice recurve comment!! Tiller looks great.

Offline Badger

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Re: Mass principle handle mass and working limb, help
« Reply #7 on: January 31, 2018, 01:18:54 pm »
   The mass theory is primarily useful when doing designs and draw weights you are not so familiar with. Once you know the proper dimensions you are usually good to go. I would say the bow you are showing above has handshock because the tiller is too round and it is all coming to brace at the same time instead of unwinding a little bit. Message me your e email and I will send you a copy of the calculator. I still use it religiously because I still make a wide variation in styles weights and different woods. I will do a calculation on your and come back and post it. 

Offline Badger

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Re: Mass principle handle mass and working limb, help
« Reply #8 on: January 31, 2018, 01:34:56 pm »
   I just did a work up

 Length- 61"=3.5 oz
 Set back behind handle 2"= 1 oz
 Stiff handle and fade area  10"= 5oz
Draw length 26"= .25 oz
Draw weight 48#= 9.6 oz

  Total- 19.35 oz

  If you have a longer than normal handle and fade area I usually add a couple of inches to the draw length when I figure it.

Offline redbow22

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Re: Mass principle handle mass and working limb, help
« Reply #9 on: February 01, 2018, 12:35:59 am »
Thanks a lot Steve i will send you an email !

About the handshock i think the tiller is quite right, limbs are sub pyramidal and i  tend to too much elliptical or whiptiller bows sometimes because i am focused on minimum string follow.
(Which is also wrong when you end with heavy limbs and no string follow).

I made it work more close to the handle so i would say it's 8" and not 10" like you seem to say ?

Beside this, on release, the string touch the recurves maybe not simultaneously generating then some handshock and it maybe felt more noticable as i shoot these days mostly a fiberglass straight bow with very little handshock ...

I recently removed a total 125 grains of outer limbs sides, lost 1# and felt the hand shock was better.

I am sorry i don't understand this :

Length- 61"=3.5 oz     you mean the same :  "Draw length/ working limb : 26/19 or 20 = + 3,5 Oz or 3 Oz" ?

Set back behind handle 2"= 1 oz      you mean recurve ?

 Stiff handle and fade area  10"= 5oz      (from picture you saw i guess) What about width and thickness handle variability ?

Draw length 26"= .25 oz      ?

Draw weight 48#= 9.6 oz      i don't figure how you get this number ?

  Total- 19.35 oz .... This bow actually weights : 19,28 oz !
« Last Edit: February 01, 2018, 01:02:27 am by redbow22 »
Jérôme   
Location : France

Offline redbow22

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Re: Mass principle handle mass and working limb, help
« Reply #10 on: February 01, 2018, 01:00:35 am »
limb width fades : 43 mm (1,7")
limb width mid : 31 (1,22")

Base of recurve is 21 mm wide (about 7/8" wide)
Jérôme   
Location : France

Offline redbow22

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Re: Mass principle handle mass and working limb, help
« Reply #11 on: March 12, 2018, 05:39:57 am »
FINALLY DONE !! and delivered...

19 OZ (without leather)



Jérôme   
Location : France

Offline BowEd

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Re: Mass principle handle mass and working limb, help
« Reply #12 on: March 12, 2018, 06:52:05 am »
I have a friend that had a skill saw injury on his had and deep scar tissue test my bows if I have a suspected hand shocky bow.
I usually don't feel it myself unless it's obvious.A bow like yours looks like it should'nt have much hand shock.
BowEd
You got to stand for something or you'll fall for anything.
Ed

Offline NorthHeart

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Re: Mass principle handle mass and working limb, help
« Reply #13 on: March 12, 2018, 08:17:47 am »
Lovely bow.  For bow mass weight what kind of a scale does one use?  Would the same scale be the one for measuring sinew weight?

Offline redbow22

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Re: Mass principle handle mass and working limb, help
« Reply #14 on: March 12, 2018, 09:16:30 am »
Thanks 240m3srt !

Just an electronic kitchen scale...

BowEd, Finally with 5,7" brace height and 28,5 grams arrows (440 grains) (9,3 grains/pound) the bow is fine without excessive hand shock.
As i said there is not such a relative thing as hand shock, when you shoot with different kind of bows ...modern ones and go back to selfbows.

The bow was made as narrow as possible and thin in the recurve part  and outer limb. The previous identical 61" recurve osage bows i made were 21 ounces instead of 19 here...but came with a more elliptic tiller ...
Jérôme   
Location : France