How Long Do Recurve Limbs Last?

QandA logoDear Coach Ruis,
I got my new limbs today, to replace the one that broke. I noticed that I now have to walk the string less, even though they have the same labeled draw weight as my old limbs. My new limbs are $230 carbon limbs, whereas my old limbs were $80 wooden limbs. Could this difference thus be due to manufacturing quality or the material of the limbs? Finally, how long do limbs last in general? My old limbs lasted 2 years. Could I expect my new limbs to last longer given the price?
Thanks

***

Limbs can and should last a lifetime. Two years is way too short. The usual procedure when a limb fails (In this case the lower limb had internal damage and just stopped functioning as well as the top limb. SR) is to approach the manufacturer for replacements. They want the defective limbs to examine so they can determine what the flaws were. So they send you new ones and you send them the old ones. Limb failures are more common for lighter weight limbs than more stout ones and some manufacturers have more problems than others although this is very hard to determine because we usually only find out about them well after the fact (manufacturers do not publish their failure rates) and limb designs change from time to time and errors are corrected.

The draw weight of a pair of limbs is just one factor in their ability to store and release energy. Think about it. You can make a bow of any draw weight out of PVC pipe. If PVC pipe limbs were as resilient as commercial limbs, why would anybody buy expensive limbs when $20 of PVC pipe would do as well? Draw weight is not the sole determining factor of arrow speeds.

The other two large factors are design and materials. The limb shapes are now just about all the same (or very close to one another), so the design factor reduces to how many laminations and what thickness those lams are. The material factor should be obvious. Most top end limbs have no natural materials in them any more (wood, bamboo, etc.) as synthetic materials can be made to be more consistent and less affected by environmental changes (temperature, humidity). Limbs which “restore” their position from “full draw” flex to “brace” flex fastest will be the fastest limbs. But we don’t want just fast limbs (to create smaller crawls, etc.) we also want stability in those limbs. We want the path the limb takes between those two states to be repeatable. If the top limb finished before the bottom limb one time and then behind it the next, you will not be consistent. So, we all want fast, stable limbs that last a very long time and that depends upon their design, the materials they are made of, and the draw eight specs they are made to.

Let me know how your new limbs are working.

 

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2 Comments

Filed under For All Coaches, Q & A

2 responses to “How Long Do Recurve Limbs Last?

  1. Jeromy Blevins

    How long will fiberglass/wood limbs last? Will they lose poundage over a certain time? How often should they be replaced or when should they be replaced?

    • Unless they are damaged, I do not know of any limitation on their use. Fiberglass is the critical material in recurve limbs. Before their were fiberglass limbs, all wood bows tended to “follow the string,” that is take a bent shape under the tension of the bowstring, which lessened the power of the bow. When fiberglass limbs were made, early on anyway, someone wanted to see if they, too, would follow the string, so an experimenter took a bow and measured its draw weight, then strung it and hung it on a wall for two years. When taken down from the wall that bow had the same draw weight as when first placed upon it.

      So, limb tip protectors can crack, limb butts can crack (if made of wood they can dehydrate and weaken) and they may break, but I have never heard of a limb failing due to failure of the fiberglass, even glass limbs that had surface cracks. (Surface cracks parallel to the limb are usually no threat to the limb. Surface cracks sideways on the limb may indicate an underlying fault that could cause the limb to break.)

      Of course, I am referring to high quality limbs made by reputable manufacturers. If you need more evidence, note that almost all compound bow limbs are now made purely of fiberglass and they stay strung 365 days in a year and can go many years with no hint of a failure.

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