ilf upper limb noise

[Un-Cool]

Asking for some assistance.

I thought I posted this earlier today, but I clearly need help with that too.

Here's the cliff notes version:

I just acquired an ILF riser and 2 sets of limbs.  One light and one heavier, practice and hunting resp..

I have the bow tuned to what I think is as good as I can and the top limb seems to vibrate and recovers more slowly than the bottom.  Also, more string noise from the top.

Any ideas on why this is happening?

Thanks,
Ben

[Un-Cool]

here's the stats:

light limbs, 28.5 to 32 pounds at 28"
My draw length is 28"
62" bow with 17" riser
Arrow is 600 Axis approx 410 grains, with 20% FOC  =  13gpp
Arrow flight is excellent-- bare shafted, paper tuned, video tuned above arrow flight, center shot,
Brace ht is at the top of what I can gather as to recommended.  8.75 inches
Fast Flight flemish string
Two puff balls on string, one at 1/3 and one at 1/4 length of string.
4 arrow strap on quiver
Riser is a galaxy sear and limbs are wns bamboo glass
The bow shoots really nice, just not as quiet as I want.
I have not added any other limb dampening, or else..... yet.

[Sojurn]

Try adding the loop side of velcro in between the limb and the riser.  I've used silicone rubber in mine,  but it's really tough to get it to stay glued in place.  Anything to dampen some of the vibration from the limb should help.  Also make sure all the screws are tight and secured(lock tight or plumbing tape).  ILF bow can be very quiet,  you just have to dot I's and cross T's

[McDave]

On most ILF bows, there are many adjustments that can be made with allen screws of various sizes.  The first thing to check is that all of these allen screws are snugged down.  Snug, not tight.  On all of my ILF bows this means first removing the lock screw, and then snugging down the set screw.  Then replacing the lock screw and snugging it down.  All of these allen screws have a purpose, which you may want to explore at some point, but for the purpose of eliminating noise, they just need to be snugged down.  This includes any allen screws in your arrow rest, etc.

You didn’t mention what your tiller is set to.  Please provide that and whether you shoot split or 3 under.

[Un-Cool]

OH yeah, tiller

3/16" more on bottom, I shoot 2 under.
I tweaked it to there after shooting at even.  Seemed to fly better.

I will check LLA bolts and lock screws but I didn't need to change this.  The string is perfectly straight using beiter gauge.

This is my first ILF.
Thanks

[McDave]

I assume both sets of limbs have the same upper limb noise and vibration problem?  If the noise was different, or only was present with one set of limbs, that would be significant.  Just for fun, switch bottom and top limbs and see if that changes the noise/vibration.

[Un-Cool]

I am so happy you said that.

The other set I haven't put as much effort into, but if I remember right.  They don't, or it doesn't.

I will definitely do that, switch top and bottom.  I didn't think I could...

Figgered I'd get arrested by the international limb fit police.

Raining here now, finally.  I'll check back.

Thank you for helping rattle that nut loose in my head.

[McDave]

If the noise/vibration only happens with one limb, make sure the ILF fitting that is mounted on that limb is snug.  Might as well check them all while you're at it.  All the ILF limbs I have ever seen are the same top and bottom, so can be swapped without damaging the bow.  Since I haven't seen all the ILF limbs there are, it is possible that there are some than can't be swapped, so if there is any problem plugging the top limb into the bottom slot, or if they are a different length, then don't do it.  One would expect that the bow would shoot better with the limbs in the correct slots, but in one case I found that the bow shoots better with the limbs reversed.

[PrimitivePete]

What brace height are you using. I know my ILF rigs prefer a longer brace height than my other bows.

[Un-Cool]

Yes PP, I thought it was odd.  I walked it all the way up from about 7.5" and it smoothed out at just under 9".  All my other 62" takedowns have been around a fist and a thumb.  There's a word for that.  It could be brace. Hmmm
This bow is at least 1 and a half inches more.  Shoots fine tho, at that height.  Disregarding the slight twang.
McD I switched limbs and it's virtually the same.  I guess I will start over and retune from the beginning. Or add some dampening.
Thanks people for your help.

[Orion]

Seems to me the bow is out of tiller.  If you're shooting two under, the bottom limb should be even or negative tiller, i.e., less than the upper limb, not more as it is now.

[Kirkll]

Another thing that has not been mentioned is draw weight vs string tension at brace. The lower draw weight limbs have much lower string tension than higher draw weight limbs do and often will make a bit more noise. You will notice a much bigger difference on different arrow weights that you run through lighter draw weight limbs, than heavier draw weights too.

As a custom bowyer I’ve found The lower draw weights are the toughest ones to build and get balanced properly. They are also much more sensitive to requiring perfect alignment. So be very careful swapping limbs top and bottom, and check your alignment closely or you can easily ruin a set of limbs unknowingly drawing it too far with the tracking off, and cause a serious twist to the limb tips.

I’m getting to the point I will not build any more limbs less than 35 @ 28”. Anything less than that is a pain in the arse to keep stable.  I’d much rather build 80# hunting bow limbs that ultra light target limbs.   Kirk

[Un-Cool]

Thank you Mr Kirk,

I will keep an extra close eye on the alignment.  I am OCD when it comes to this as I might check and recheck alignment many times.  I did have a limb twist in the past that nearly removed my hand from my arm, well, it felt like that.  I am also VERY careful as to how I store my bows so as to not ever let that happen again.  The bow was actually an old Herters that a customer wanted me to try and straighten the limb.  Young and foolish, I was.

BUT,? That's also adjustable with this set up correct? Or can the lateral limb adjustment actually correct a slightly twisted limb?

Anyway, now that you say this, I think you've hit the nail on the head and this set up, which I just fabricated from two different manufacturers has no perfect way to tune. I just wanted to get into ILF and this was the least expensive way to start.  The limb flutter on the top limb is more than likely exactly what you say.  My days of shooting 50 plus pounds are over.

I reset the tiller to even with no appreciable change.

Also, thanks to all who offered suggestions.  I very much appreciate y'all taking time out of your day to help an old bow hunter tinker with this little bow. Its great fun!

[Kirkll]

BUT,? That's also adjustable with this set up correct? Or can the lateral limb adjustment actually correct a slightly twisted limb?

Absolutely…. If you adjust the lateral limb adjustment until it is tracking straight, then leave it strung up and put it in a bow rack in the house resting on the lower portion of the limbs, or even hang it on the string horizontally on two pegs will work… let it set and check it from time to time.

That is the beauty of an ILF set up… everything is adjustable….   

The down side is that you are constantly needing to check things to make sure nothing has moved. Not exactly what I would consider the best hunting rig, but I’ve hunted with mine now and then…. Higher maintenance bows for sure…. Kirk