Author Topic: Limb twisting weird.  (Read 461 times)

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Offline aznboi3644

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Limb twisting weird.
« on: January 17, 2020, 08:31:13 pm »
This board stave is really making me scratch my head.

I thought to fix prop twist you remove wood from the high side.  Well on this bow Im working in the limbs are twisting towards the strong side.  And both limbs are twisting in opposite directions so the string is still tracking center. 

Could a board from a twisted tree cause this?  Its really messing with me. I really dont want to pull a splinter on the back corners at full draw.  Ive been hit in the face by broken bows before and it doesnt feel good.

I tried looking at the thread for fixing prop twist but all of the pictures are lost.
« Last Edit: January 18, 2020, 08:48:49 am by aznboi3644 »

Offline bradsmith2010

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Re: Prop twisting weird.
« Reply #1 on: January 17, 2020, 08:33:30 pm »
Maybe fix it with heat?
Maybe u r taking off wrong side

Offline SLIMBOB

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Re: Prop twisting weird.
« Reply #2 on: January 17, 2020, 09:00:28 pm »
Agree with Brad. Heat it and bend the prop twist just past straight if in fact it is prop twist.  You are trying to fix limb twist but you call it prop twist. Prop twist is present before the draw and can pull itself straight.  Limb Twist manifests itself during the draw.
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Offline Eric Krewson

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Re: Prop twisting weird.
« Reply #3 on: January 18, 2020, 07:58:32 am »
I have never had much luck getting twist out by taking wood off the high side except on bamboo backed bows, I get out my heat gun.

On thing to note is I make my bows with carefully measured guide lines down the sides, they are very even side to side, any twist is very rare and I almost never see it.

If you lay a bow out like this it is unlikely you'll ever see any twist.


Offline aznboi3644

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Re: Limb twisting weird.
« Reply #4 on: January 18, 2020, 08:51:21 am »
Sorry yes indeed it is limb twist and not prop twist. 

This is a board bow.  Limbs are flat across the plane.  I measured.  Limbs are flat but they still want to significantly twist in opposite directions as I draw. 

Note.  While rasping from the handle out to the tips one limb rasped smoothly while the other wanted to dig in which indicated to me that the board may have been from a twisted tree or twisted section

Offline bradsmith2010

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Re: Limb twisting weird.
« Reply #5 on: January 18, 2020, 10:49:29 am »
Probably not effecting the way it shoots

Offline artcher1

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Re: Limb twisting weird.
« Reply #6 on: January 18, 2020, 02:19:14 pm »
Was your board bias ringed?

I do like Eric, I lay my limbs out using very precise measurements. When taper tillering, one can forget about hinges. It just doesn't happen.....Art 

Offline George Tsoukalas

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Re: Limb twisting weird.
« Reply #7 on: January 18, 2020, 06:31:56 pm »
aznboii, did you cause the twist by uneven wood removal or was it natural? Jawge
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Offline Eric Krewson

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Re: Limb twisting weird.
« Reply #8 on: January 18, 2020, 07:41:48 pm »
Wood is wood, undulating grain can cause stuff you can't measure away, get out the heat gun.

Here is how I do it; heat the offending spot, put the limb in a padded vise past the twist, give the bows handle a quick twist, hold it briefly and take it out of the vise. Let the limb cool, string the bow and see if you corrected the twist. If not, repeat with a little more pressure on the handle and holding the counter twist a little longer. Repeat again as necessary.

I do the same for static tips that cant off to the side when I initially string the bow. I tweak them a little at a time until I have them perfectly true.

Offline bownarra

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Re: Limb twisting weird.
« Reply #9 on: January 19, 2020, 02:08:31 am »
It is twisting because the fibers are running through the board at an angle. Not properly straight grain.
Trying to 'untwist' it is likely to cause more serious 'issues' eg. it may be the final straw on the camels back.
Post some pictures of the grain of the board.
Board bows must be from straight grained wood. The same reason your other bows have broken likely as not.

Offline aznboi3644

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Re: Limb twisting weird.
« Reply #10 on: January 19, 2020, 04:12:35 am »
I suppose it is biased ringed. The rings run about a 60 degree angle from the back.  I checked for uneven wood removal and the belly is even from side to side.

I have experienced limb twist before but it showed up as uneven wood removal. One side of the belly was thicker than the other side. 

Im guessing the reason is in the actual wood fibers.  The tiller at the moment is quite smooth and elliptical.  No hinges.  Ive been using my torpedo level to check tiller.

If I continued to tiller this 62 bow out to my full draw of 26  and the limbs keep twisting would the tension stress be largely straining the high edge?

I was thinking of just purposely removing wood unevenly favoring one side so the limbs are still flat through the draw. 
« Last Edit: January 19, 2020, 04:16:20 am by aznboi3644 »

Offline artcher1

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Re: Limb twisting weird.
« Reply #11 on: January 19, 2020, 04:56:39 am »
OK, the bias ringed board is the problem. Wood only wants to bend in two planes, with and against the grain. Taking wood off one side or the other will not solve your problem.....Art

Offline George Tsoukalas

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Re: Limb twisting weird.
« Reply #12 on: January 19, 2020, 07:33:52 am »
Was the board twisted  when you bought it? Did wood removal start the twisting. Sorry. I am a little slow this morning.

I have made a lot of bows from bias (rift sawn) boards with no inherent twisting. I actually prefer them.

Yes, you adjust your wood removal to eliminate twisting and it does not take much.

Be sure to exercise the bow at short draws after each session.

Look. Check with your eyes; run your fingers over your work to guarantee evens of removal.

Patience.

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Jawge
« Last Edit: January 19, 2020, 08:10:50 am by George Tsoukalas »
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Offline George Tsoukalas

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Re: Limb twisting weird.
« Reply #13 on: January 19, 2020, 07:50:51 am »
I was gifted a beautiful yew stave by Jim Fetrow of eternal memory. You can imagine how much I wanted that bow to be a success and it was thankfully.

I was very careful to remove wood evenly from both sides of each limb. I even used outside calipers to make sure of that.

Yet, when I strung it both limbs were twisted in the same direction. So with a scraper I took a few swipes from the high side (ie the side closest to the string in the strung stave). Exercised at short draws between each session. Problem fixed.

Jawge
Set Happens!
If you ain't breakin' you ain't makin!

Offline aznboi3644

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Re: Limb twisting weird.
« Reply #14 on: January 19, 2020, 08:32:22 am »
Ive made bows from all but flat sawn boards.  This board was straight and true from the start. 

Note: this bow is 1 3/8  wide at the handle for 4 then straight tapers to the nocks.  So The width at mid limb is just a hair over 1 wide.  Hence why I am so confused as to why it is twisting so much with narrow limbs.


Ill slowly work one side to try and counter the twist. Jawge I stumbled upon your sight long ago and it was what helped spark the bowyer in me years ago. 

This 48 red oak short bow I recently finished to practice my tillering was made from a similar looking rift sawn 1/2x 1.5 board and does not twist at all.