I bought a Mohawk (49# @28) and Centaur (47# @28) from the classifieds and shot them last night. (My draw is ~27"). Both make noise as if the arrow is hitting the shelf.  I tried GT1535's, Heritage 150's and 250's all with different points from 100 to 200 and none made any difference in the noise. If it were the arrow spine I would expect those drastic differences in spines to make some difference in the noise.  I wrapped tape and even velcro completely around the shelf and riser and that didn't seem to make any difference either.

I haven't noticed this at all with my recurves so I suspect this has something to do with my grip on the bow since they're both much lower than the recurves.  I read through a bunch of threads here and some seem to suggest that.  Playing with my grip didn't seem to change anything either.  Brace heights are 7" on both bows.

Would this be a case where I just have to change something in my form to adjust to the longbow?  I really like them.  The Mohawk puts those arrows right where I'm looking and loves the heavier the 250 arrow.  The Centaur shoots those way too light 1535's like a dart.

Try to concentrate on a cleaner release. It worked for me.

Do you know the GPI on those arrows? I was shooting GT 55/75's @ 8.4 GPI w/ 200 grains up front and they made the same noise you described. I switched to Easton FMJ's 500 spine @ 9.1 GPI w/ 200 grains up front and it went away

I tried a tab and my normal glove with no change.  I'll definitely try to work on my form since that's helpful all the way around.

Are longbows more sensitive to that?

I think so.

QuoteOriginally posted by Stoneyb488:
Do you know the GPI on those arrows?

The Heritage 150's are 10 and the 150's are 11.  The 150's are 30" and the 250's are 30.25".  The GT1535's are full length and are 7 GPI.

What length arrows are you shooting. You need a full length bare shaft to test.

I think I replied with the lengths while you were typing your question.  LOL

You may try raising your string knock slightly. to find out where the arrows are hitting the shelf. put some masking tape on the strike and the shelf base, and use a thin film of lip stick over the masking tape.... that should tell you the story. look at the arrows and the shelf after shooting it. some times just rotating your fletching will help. try a cock feather in for example.

Some times just building up a crown  point on your shelf and raising the knock will do the trick too.

food for thought.

I guess I didn't include all the things that I tried.  I both raised and lowered the nock point, pretty darned significantly, with no real change.  When I added the velcro to the shelf it really built it out.  I put tape on it as well but didn't see any marks.  I was going to try white electrical tape next so marks would show up better but I love the lipstick idea.  I'm definitely going to try that.  I think that's the next logical step other than trying to get a video and slowing it down.  I was kinda hoping for a magic answer here. LOL

What are the recommended brace heights for the bow? you can always increase the brace.

The Centaur should be 7 1/2 or more so I need to raise that.  I don't know what the Mohawk should be.

move your string nock up or down  a 16th of an inch at a time. you might have to move it a quarter of an or so   hope this helps

"you can always increase the brace."

Try raising the brace 1/8" at a time until the slapping stops. This has worked for me numerous times.

When I shot carbon and aluminum I had this problem.  Sounded like I was shooting a compound sometimes.  I never did fix it, but when I switched to wood arrows the noise went away.

Brian, I shot @a 525gr  poc shaft spined 65-70 out of her. I also used a four fletch as well.  I used a 6 3/4 brace height             keep me updated

Sounds like a tuning issue. Go slow when making changes.

I also don't think arrow material matters... arrow weight probably caused a difference in sound... and most compounds are whisper quiet these days. Just sayin...

Among other things I would pay attention if you are tourqing your grip on release.  Going from a recurve grip to longbow may affect it.

Btw Ive had 4 Mohawks you'll really enjoy it.  Good luck.

Eric

QuoteOriginally posted by parshal:
I tried a tab and my normal glove with no change.  I'll definitely try to work on my form since that's helpful all the way around.

Are longbows more sensitive to that?

I had the same problem, tried a lot of tuning.  Turns out it was my form.  I think I read about it later in one of the instinctive shooting books too.  The grip on the bow changes things, and I think you really have to step back and think about your form.  After I did that for awhile, it went away.  Now I can shoot different arrows and none of them hit.  (Some of 'em fly like crap, but they still don't hit unless I have a bad release as well.)

The last two posts were spot on.  I went to Rocky Mountain Specialties and we figured it out.  I wasn't torquing the bow but ws putting too much pressure on the web of my hand rather than even from the web to the heel.  This effectively took the bow out of tiller a bit causing the connexion hinge to pop.

Vince came walking in the shop while I was there and we talked for quite a while.  What a good guy.