Building a quiet/efficient bow

[Smguinnip]

I am new to bow building (built a handful of Kenny’s d/r bows and they shoot well) so now I would like to try my own design. The question that I have is: what do I need to focus on while trying to design a glass d/r longbow that help make the finish product quiet and efficient? As I understand, a heavy/dense riser and limb timing are important but I am sure that there are other thing to keep in mind. Any and all help is greatly appreciated.

[Crooked Stic]

Limb timing is most important. After the shot both back to brace at the same time. Kenny's designs are hard to beat. You might play with riser length to see what you like. The shortest working limb to suit your draw length is best in my opinion.

[Smguinnip]

Yes, I am very impressed with how well Kenny’s design performs, especially with my limited ability. Would the shape of the fades have any effect on the performance of a bow? Long and gradual vs short and steep? And with the limbs, narrow and thicker vs wide and thinner?

[kennym]

You can try a hardwood I beam riser to reduce riser flex, and G10 for that is even better. If the riser is flexing that isn't helping performance.

More reflex helps performance to a point, then I have trouble being accurate with it if you get too far. 

I like long fades, I hate to see a bow bending (hingey) hard off the blunt riser.  Has to shorten bow's life.

Thicker and narrower is supposed to help performance, I haven't done that yet, but it's been in the back of my mind for awhile.  so many ideas, little time...  I'm pretty sure it would be quieter , or at least change the tone to a deeper sound.

Between Mike, and if Kirk drops in, you should get some good pointers.

[Kirkll]

When you start playing with geometry , or the shape of your limb coming out of the form, there are many factors that can determine where your limb is bending. The width profile is one of them, but mostly its the length of your fades or wedges used, and the length of your tip wedge determines how much energy is stored in the working portion. a shorter working limb stores more energy with shorter draw lengths. longer working limbs allow a longer draw length without stacking....

Typically a deep core narrow limb always trumps a thinner wider limb in the performance dept. But..... And there are always a lot of butts..... Storing energy, and getting a nice string angle at full draw that is smooth, and eliminating hand shock, is always a main goal.  But transfering that stored energy to the arrow shaft is the key factor to higher performance.

That energy transfer is a whole different rabbit hole, and gets into string tension at brace, or preload when stringing the bow. You need enough preload on that string to stop the forward motion of the limbs dead, and transfer the energy to the shaft to accomplish this.  Another factor is limb travel distance.  How far is that limb actually moving when you draw the bow? Less limb travel makes it easier to stop the limbs dead.....The narrow deep core limbs typically weigh less in the tips, and are easier to stop clean.

There are many ways to manipulate your string tension. Limb pad angle, the reflex shape of the limb, taper rates, wedge locations and working limb locations, and even the string length all come into play ....
 
This is easier to learn to manipulate with R/D long bows where lateral stability is more forgiving. Once you get into recurve designs the difficulty is intensified dealing with lateral stability and tracking issues.       Good luck.... Its a hell of a learning curve.     Kirk

[Smguinnip]

Thanks guys, you have gave me plenty to digest. Just to clarify, I do not intend on building a high performance bow, but I figure that if I can start with some design aspects of a high performance bow, I might end up with something that is shootable. I’m sure that I will be back with some more questions. BTW~Kenny’s bows shoot as good or better than any of the other bows that I own. I just want to see if I can come up with one that I can call my own.

[Kirkll]

If you truly want to explore different limb designs in hoping to come up with something to call your own, I think you’ll find that it’s all been done before at one time or the other. But hey!  It’s still your own…

The best advise I could give you is to build a tiller tree that can hold your bow at various draw lengths and allow you to step back and look at the way the limbs are bending and even take photos. Sharing tiller tree photos with other bowyers can help give you insight for improvement.

Learning how to manipulate where that limb bends using different taper rates and different length wedges is an eye opening experience. Your width profiles will change automatically as soon as you come up with a 70# bow while shooting for 50#…      That’s when you narrow them up skinny as a whip , and learn about trapping.  Then you end up sanding a lot of glass too…. The end product is going to be fast on those…. Thinner glass, and narrow profile equals much less mass weight in the limbs. Depending on your preload, you can build a serious hot rod like that….


 Then experimenting with different core materials can offer various results. My advise in that department is to stay with rock hard maple and bamboo cores and save yourself some grief. Playing with softer core material can work fine, but the longevity will be questionable.

Going back to your original question about shorter steeper fades vs longer wedges or fades. Typically you will have much better luck with long lean wedges that push the working limb out away from the riser more. The steep short wedges seem to give you more of a hinge at the fades and increase your limb travel distance.

More food for thought… Kirk