Hickory propeller twist-fix or no fix?

[critman]

I'm making a youth bow for someone for Christmas. Used what I had which was what I thought a piece of nice hickory. Cut her out, glued up riser, tiller looks good but....both limbs twist at draw, different directions. Some say fix, some say let it go. Not real bad but since it is a present for someone I would like to straighten her out. It is a continual twist at draw from just above fades to tips just in different directions. Never had to deal with this before. The string tracks straight down the middle at brace height. My plan would be to use shims like Gary Davis shows in his video, but the limbs look straight at brace so I would have to go back past straight at brace so the tips are straight at full draw? What say ye, fix or let it go? The young man getting the bow will not know any difference but it's a matter of pride.  

[Pat B]

If it lays flat unbraced and twists braced the limb thickness is probably uneven. Feel the limb thickness with your thumb and fingers. work your hand across the limb as you move down. You should feel the thickness difference. Reduce the thicker side and the limbs will straighten out. It's a pretty common problem.

[critman]

Will do. Thanks Pat!

[mikkekeswick]

Not always,wood can also twist when there is no difference in thickness. That's when you start scratching your head!
But Pat is probably right.

[Roy from Pa]

Fix it, Chris. Mike is also right about limbs twisting when they are even, but lets hope this isn't the case on your bow. It's amazing what happens when one side of a limb is just a tad thicker than the other side. The string will "always" drift towards the thinner/weaker side. Because that side of the limb is bending up a little more than the thicker/stronger side, causing the limb to appear like it is twisting. Visualize it as if you are looking at the end of a board/limb as it's being pulled upward. And one side of the board/limb is 1/4" thick and the other side is say 1/8th" thick. The 1/8th thick side is going to roll/twist towards the center of the board/limb. On your bow, it sounds like you have opposite sides of each limb thinner than the other side edge. In my earlier years of bow making, I was trying to string a self bow and the string wouldn't even stay on. There was a more experienced bow builder present and he ran his fingers up the limbs, like Pat suggested, and he said this side of the limb is thicker than the other side. After he pointed that out, I could see that was true. So I reduced the thickness of the thicker side to match the thinner sides thickness, strung up the bow and low and behold, it was fine..        DUH, LOL...

Another thing to check is your string nock depths. Those not being equal can cause limb twist also. Here is a neat chart to help you out. Print it out and save it..

   

[PEARL DRUMS]

It can twist with even thickness if the bow was forced from the stave and grain lines not followed.

[Bowjunkie]

Yep, concur with Pearly. It can be due to how the bow was layed out.

Also, folks tend to lean a tool to one side as they work, which can inadvertently cause more wood to be removed from that side. Then they flip the bow around and do the same thing to the other side which causes the limbs to twist in opposite directions.

Switching hands and/or directions with the tool, checking them often to ensure the limbs are a consistent thickness and being conscious of tool angle/leaning can help avoid problems with limb twist.

Sometimes though, there's just no way to get around it. Bows can shoot fine with some twist in em.

[John Scifres]

If twist is a part of a natural stave, I leave it assuming the string stays on.  

In this case, I would try to fix it.  Weird movements during the draw bug me and usually lead to some poor shooting characteristics.  Double-check your layout and do as pat recommends.  If all is well there, then look into thinning the stronger side of the limb.  Gently with lots of exercise each time you remove wood.

Pics would be a great help.

All that said, if it's a lightweight kids bow, I might not do anything drastic.

[bowmad]

Hey gang. I'm having this same problem with a maple bow I'm working on. Roy's diagram makes sense, but my tips are reflexed, and the side that the string is pulling to is actually thicker than the other side.  What's the deal?      Does is make any difference? I'm getting close to target weight so I need to figure this out before I ruin it. Not bein able to get the photo to load but here's the link. Thanks     http://s101.photobucket.com/user/Aaron_Ingram/media/443abe01-92be-4468-90fa-e3ebedd42ac6_zps4ccc9191.jpg.html

[critman]

Bummer bowmad. The bow I made is 20#@25" so I didn't have much problem fixing most of the twist and it shoots fine. Maybe try what Roy and others have suggested and file the opposite side of nock that the bow twist towards. This helped me more than anything. Good luck dude. BTW nice looking bows in your pics!

[Wolftrail]

Originally posted by John Scifres:
If twist is a part of a natural stave, I leave it assuming the string stays on.  

In this case, I would try to fix it.  Weird movements during the draw bug me and usually lead to some poor shooting characteristics.  Double-check your layout and do as pat recommends.  If all is well there, then look into thinning the stronger side of the limb.  Gently with lots of exercise each time you remove wood.

Pics would be a great help.

All that said, if it's a lightweight kids bow, I might not do anything drastic.

I agree 100% I really hate limb twist, as far as I'm concerned if I build a bow with twist its not a good bow.
And  poor shooting characteristics can be the outcome.

[bowmad]

Thanks critman. I'm still a newb for sure! Filing the nock did help some but it's still irritatingly off. Been taking away wood slowly from the opposite side too, but I can't tell any effects from it yet.

[Roy from Pa]

Make sure to work the bow at least 20 times after removing wood.