recurve help (limb noise?)

[bowhunter22]

I hope i can give you enough info. I started building bows about a year ago.  I've built 4 recurves (60" nock to nock) out of the same form.  Two of them are fine and the other two have a knock sound when fired.  They all have the same lamination thickness and the same glass.  All are very close to the same draw weight.  The only difference i can think of is the type of wood used for the laminations.  The first one is maple inside and bubinga front and back.  The second one is maple inside and black walnut front and back.  The third one is black walnut inside and maple front and back.  The fourth one is maple inside and black walnut front and back. I used black walnut on the outside of two because i really like that type of wood but those are the two that knock when fired. I am thinking that because black walnut is softer, i am possibly getting some limb slap (if there is such a thing) when shot.  I was told that the material on the inside laminations isn't that important but it is the only difference i can think of.  I would like to build more bows with the form but am a little gun-shy with the noise i have from two of them.  Any help or advice would be appreciated because i really want to hunt with the black walnut bows but i think they are too loud when shot.  If any more info is needed to help with your diagnosis, let me know and i will try. Thanks for your time.

[bjansen]

Compare the brace height and the tiller between those bows.  I made a couple 60" recurves and noticed a significant amount of noise at a low brace height, which disappeared when I brought it up (a range of 7"-8" worked well on mind).  Additionally, if your tiller is off, and knock point is too high that can also contribute to noise (from my experiences)...

I cannot see how it would be the core lam material..I personally think that is it.  Best of luck

[bowhunter22]

I'm sorry i forgot to mention that i tried different brace heights.  It was quite loud at 7" and better at 8" but still too loud. I didn't want to go higher than 8 because i thought i would lose a lot of performance from the bow.  I also put on those brush buttons. They are apparently a string silence as well.  It didn't help. I'll try changing the nock position some more.  I tried this a bit but will pursue it more.  Thanks for your help.

[sulphur]

bjan has given some pretty good advice.  i would think since you have made 4 from the same form that tiller is the culprit.  all other things being the same that makes the most sense.  check your brace height and compare tiller and i bet you'll figure it out.

[bowhunter22]

Thanks so much for the advice. (bjansen and sulphur)  I'll check the tiller and hope that works.

[LPM]

If all else fails here is how I solved my own string slap problem many years ago.  I found out that a flemish twist string that was twisted to tightly in the area of limb contact caused sring slap noise.Also three bundle flemish strings are noisy on recurves because they are more rounded and hard.If you make your own strings,try this.  After twisting the loops, don't twist the first three inches of splice so tightly. then when you have only a couple of inches left to splice, twist it tight to finnish the splice.  It works believe me.  For fast flight strings use up to eight additional strands of B-50 in the loop and recurve contact area. It provides more bearing area for the string on the limb nocks and softens the string for a more quiet string to limb contact.  I hate to see people puting band aids on problems.  I don't believe that any bow requires a pad between the string and the recurved portion of the limb.  Get the string right first.  Brace the bow for performance.

[2treks]

What about the string popping into the groove cut into the belly glass?

[LPM]

Hmmm .......I'm not sure that I've ever considered this as a noise maker or ever heard it while shooting.  It seems to me that if a string has to pop back into the groove when shot and in doing so makes noise,  the bow has an alignment problem, and maybe a pretty deep and sharp sided string groove.  

From what I've learned making a few bows over the years is that a bowyer should first string and shoot a new unfinished bow with no string grooves filed into the limbs.  When it has been proved that the string will stay in the center, shot after shot, the string groove is then filed into the limb.  I don't see the need to file to deep for this groove because I feel that this groove only helps to keep the string from creeping to one side in the event of unwanted accidental side pressure, weed snags or what ever else we get ourselves into hoisting a bow or setting it down in a bad spot. Only a shallow groove is required.  Too deep in my humble opinion only weakens the glass.  

A good test on a suspected string groove noise, would be to draw the bow back to full draw, and let it back down as slowly and as straight as you can.  The string should track back into the groove.  If It won't and you have to "pop" it back in, you have limb alignment problems.  You will have to see if the limb twist can be fixed .......a whole diffrent topic.  

If the bow is aligned properly the string should fall into the groove silent. I try to keep the loops of my strings as small as possible to aid in consistant string alignment with the grove.

Man........ I ramble too much!  Sorry if I insulted anyones intel.  My spelling is painfull as well.

[2treks]

I agree with most of what you say LPM. But I have seen a number of recurves make this noise and it is always a result of limb twist, no doubt.It is not proper but it happens. The limb is twisted and the groove is goofy, I am just saying it is something to look at.
   How deep and how long is up to the bow maker and what they want. Bear and others would go through the belly glass, Howatt would add an overlay of wood and go through that and into the belly glass.
  And as you say, if things are made proper things will not make any noises.But we have alot of un-knowns to deal with and this is just one thing that is easy to look at and check.
   I think I may have trumped your rambling. No insult was taken or given(I hope) just looking to help.
   Chuck