Help for Twisted Limb

[jdavis044]

New to this forum and looking for help.  I recently received a beautiful emerald green Bear Kodiak recurve bow from the 1960s via an estate sale, and unfortunately it has a twisted limb.  I am completely new to the world of bows and am looking for a professional in either the Eastern Washington, North Idaho, or Western Montana who has the skill to fix it.  Any help is appreciated.  Thanks!

[McDave]

Welcome to TradGang!

Limb twist is fairly common with recurve bows.  Most people who shoot recurve bows are aware of this, and check the limbs for twist frequently.  If limb twist is caught in the early stages, the limb can be reverse twisted until it is straight and the bow can continue to be used indefinitely.  Anything more than a mild twist that would be difficult to see at a glance means that there has been damage to the structural integrity of the wood, and there will be a tendency for the twist to recur more and more often in the future.  Trying to repair it would be like trying to repair a piece of metal that has metal fatigue.  The only permanent repair that I am aware of would be to rebuild the damaged limb, which would be possible if it were a takedown limb, but not practical for a one piece bow.

Since it would be only a guess as to whether there has been structural damage, if it were my bow, I would assume there was no structural damage and straighten the limb by reverse twisting it, over steam if necessary.  You will probably be able to straighten it.  The question is whether it will stay straight.  But you'll never know until you try.

Reverse twisting a limb is not rocket science, and I see no reason to hire an expert to do it, since if it does have structural damage, there's no way an expert can repair it anyway short of replacing the limb.

[Car54]

Do you reverse twist with the string on?

[McDave]

Yes, this shows the basic procedure for correcting limb twist.

[Orion]

Some folks twist with the bow strung.  Just as many don't.  I usually don't.  Depends on the amount of twist that needs to be corrected.  The more it's twisted, the more likely i am to twist it back with the bow unstrung.  It's easier to bend the limb to where you want it and to hold the limb in place with the bow unstrung. The latter is important if you use heat on the limb.  You want to hold it in position until the limb cools to normal room temperature.  I prefer to use dry heat from a hair drier, for example, rather than steam.  If there are any imperfections in the finish, steam can get under it and expand the wood, which can then begin to delaminate the limb. I only heat on rather severe, persistent twists.  When doing so, it's important to not overheat the limb.  Want to get it quite warm, but not too hot to touch. A minute or so with a hair dryer usually does the trick. 

Regardless.  It's not a biggie.  Easy to do. And, as McDave says, if there is structural damage, it's pretty much unfixable anyway. Most times, it's just a twist that's easy to fix.  Good luck. 

[Car54]

Thanks guys

[Kirkll]

 Quote from McDave:
"The only permanent repair that I am aware of would be to rebuild the damaged limb, which would be possible if it were a takedown limb, but not practical for a one piece bow."

Actually Dave, I have straightened out a few one piece bows that wouldn't stay straight by reworking the tip overlays, and deepening the string notches slightly on the weak side successfully.

Some of the older bows didn't use tip overlays at all and have been damaged with the used of modern Fast Flight strings. These can sometimes be saved by adding tip overlays, or just reshaping the tip notches. A flemish twist string with padded loops is recommended for these older bows. and a lot of guys swear by the B-50 or B-55  dacron for older bows.

Endless loop strings which use serving material on the loops can be hard on tip notches sometimes depending on what serving material is used and the shape of the tip notches.
Believe it or not, Just the shape of the tip notches can cause limb twist. Especially if the loops are too tight and are not centered properly after stringing the bow.

Fiberglass is pretty cool material and can be reshaped without loosing strength by heating it. The fiberglass backing is typically what holds these limbs straight. But.... i sure wouldn't recommend heating a limb with the string on it.

My .02 cents....    Kirk

[Orion]

Good point about the string notches, Kirk.  That's the first place to look. If they're not even, the string will pull the limb out of alignment.  And, as you note, it's an easy fix.  Just even their depth. 

Agree, too, to not heat the limb with the bow strung.  That's why I only use heat when the twist is substantial, in which case I always unstring the bow first. 

[Kirkll]

Something else i've seen on lighter draw weight recurves mostly is how the string loop lays on the back of the limb can make a difference if its applying pressure evenly, or more to one side.

Flemish twist strings are very popular on Trad bows. But sometimes just flipping the loop 180 degrees can effect a slight limb twist, or help it. This depends on the shape of the tip notches and how big the loop is, vs the width of the tip notch and limb tips.  With limbs showing very slight limb twist, i would always try flipping the string loop first before any corrective measures.   

If the shape of the tip overlay is tear drop shaped properly, the string should self center after its been drawn a couple times. But often times on older bows i've seen a more rectangular transition that requires checking your string carefully for centering after you string the bow. That's a good plan anyway and most RC shooters do this automatically.

food for thought...    Kirk

[McDave]

“Flemish twist strings are very popular on Trad bows. But sometimes just flipping the loop 180 degrees can effect a slight limb twist, or help it. This depends on the shape of the tip notches and how big the loop is, vs the width of the tip notch and limb tips.  With limbs showing very slight limb twist, i would always try flipping the string loop first before any corrective measures.”

That's pretty amazing, Kirk.  My newest bow, with carbon backed limbs, has always shown a slight limb twist in the lower limb.  I tried straightening it the usual way, but it wouldn't move.  Finally, I decided that the torsional stability of the carbon limbs was keeping it in the same position, not allowing it to be straightened.  So I just decided to watch it to see if it would get further twisted or not.  It didn't, so I just decided to live with it, but I didn't like it.  After your post, I rotated the string loop 180* on the bottom limb, and lo and behold, the limb twist was gone!

[Kirkll]

Isn’t that something Dave?

 I started ordering all my strings with RC loops on both ends for all my limbs designs. I’ve found that the larger loops have less tendency to put uneven pressure on the tips, and self center much easier.   

Most string builders tie smaller loops for the bottom limb for ease of stringing them I presume. If they are too tight they can bind up just enough to cause problems. Keeping things waxed regularly  and supple is helpful.

 9 times out of 10 limb twist on a newer bow is caused by a slight limb alignment issue when the bow is built. It can easily go unnoticed until a later date. Also stringing up a bow and not exercising it and checking that the string is laying straight, and leaving it like that can cause a slight limb twist.

I’ve got a hybrid long bow I’ve hunted with for 10 years that has a very slight limb twist That has never moved and it shoots excellent. So I just quit looking at it.    

  I actually never expected this bow to survive bro…. It was an experimental set of hot rod limbs with both uni carbon and bias weave carbon cores that I put .020 glass over the back and seriously thin .008 veneers to protect the carbon but enhance performance. Besides the thin glass splintering on the edge after a fall. I’ve never had a problem with these limbs, and it has more than 10,000 arrows through it….. go figure…. I did repair the glass and did a camo paint job on the back of the limbs, but she’s still going….. 

Here she is…. My go to bow….built in 2011.    Kirk

https://photos.app.goo.gl/boRxTmzDXiovf45AA

[McDave]

She's a beauty, Kirk.  You were a little ahead of your time, weren't you!

[Kirkll]

Well I don’t know whether I was ahead of my time or not bro, but when I got into prototyping limb designs I took everything to extreme until they blew up, and then backed it off a bit….

I ran the carbon gauntlet for a few years and produced some impressive high performance bows. Some of those carbon limbs are still going strong after 10 years too. But…. The carbon itself is rather fickle. Just about the time you find the perfect combination of uni carbon and bias weave, the next batch you purchase has a significantly different strength. Hitting draw weight accurately on a custom bow was a nightmare using carbon backing.

So I drifted away from using carbon backed limbs completely, and tweaked my limb designs to the point I was very close to the same performance I was getting with carbon, just using glass….. Save my customers money, and give them a product with better longevity.  I still use it in the core occasionally by customer request. But that’s about it.

granted…..I’m not building the super hook RC designs either. Those do require a bias weave carbon to keep them stable. But the Sasquatch SS RC with glass limbs shoot very close to the same speed those super hook bows are getting and they last much longer in the field. So why mess with carbon?

But I must say this about that super hook design. Those things have some incredible engineering and an unbelievable draw cycle. I’ve shot a few of them over the years and I can see the novelty, but not the price.    Kirk