When good tuning goes bad.

[the rifleman]

Thought I would share this unique tuning issue I ran into.  Last year prior to hunting season my buddy got a new 3piece longbow.  The bow was cut past center and wanted a heavier spine arrow than he had.  We did a couple things to get his bow tuned to his 600 spined arrows--- built the sideplate way out and swapped the d97 string for a b55.  His 600s tuned well, but I told him we were leaving some performance potential on the table that we could revisit after hunting season.
Following hunting season he came over w some full length 400s.  We put the d97 string on and a much thinner sideplate.  Day 1--- nothing was working--stiff, weak,  at times.  After awhile we hung it up.  The next day we started again and when arrows were hitting 2 feet left (we're both lefties), I reduced tip weight-- the problem only got worse.  I suspected the arrows were so stiff they were bouncing off the riser giving a false weak.
I picked up the bow and after a couple shots a light bulb went off.  I noticed that each time I drew the arrow moved a good distance away from the riser and I'd use my index finger to push it back against the riser.  I had him shoot again and it was doing the same for him and he hadn't noticed.
The culprit was the rug rest which had a groove in it where his old 600s rode on it because of that very thick sideplate.  This groove positioned the 400arrow far from center shot and caused it to act dynamically stiff.  I put a new rest on and we had his 400s bareshaft tuned within a half hour. 
I always enjoy the puzzle of tuning, but this was a new twist for me.  Thought I'd share it in case it could help someone else.  One of the reasons I like leather or beavertail or calf hair rests.

[McDave]

Interesting story.  I've also had screwball things happen in tuning that have sent me off on a wild goose chase in the wrong direction.  Always a welcome discovery to find out what really is going on.  I probably also would have jumped to the false weak hypothesis, after jumping a spine group from .600 to .400.  .500's didn't work?

I always place my sideplate and arrow rest so there is a gap between the two for the feather to pass through, so my arrow groove is always right next to the edge of both.  I am told that this is a fallacy: that the feather doesn't really go through the gap.  I'm also told that it is a fallacy that helical mounted feathers fly any better than straight mounted feathers.  But old habits die hard, so I still leave the gap and still use a helical clamp.  Oh well….

[the rifleman]

McDave, the 500s had shown weak with his set up the previous fall prior to putting on the thick sideplate and retuning the bow for his 600s, so I couldn't understand why the 400s wouldn't work.  One of my biggest downfalls in this sport is my constant fascination with tinkering/tuning and seeing what I can get to work out of each rig---then when things are going well I change it up again---this past season I shot 2 deer with 2 different arrow weight/broadhead combinations out of the same bow.  My goal is to get one arrow/bow combination tuned and stick with it throughout 3D and into hunting this year---we'll see .  Fortunately my buddy in the scenario above does not have this affliction and he will be using his combo now that we've tuned it.
I've seen those videos in extreme slow motion where the properly tuned arrow flexes so far around the riser that the fletchings are no where near the sideplate and even outside of the shelf edge.  I have no idea what mine are doing at that point so I don't think placing the sideplate and rest so there is a gap would hurt a thing.  I do sometimes rotate my nocks for feather to touch my nose (again this is a constantly changing dynamic for me) so my feathers aren't always in the same position.  I have not noticed wear on any of my hen feathers (except on one occassion where the bow showed positive tiller and I shot 3 under), so my tune seems to working.
As far as the helical deal---I used to shoot in offhand muzzleloader competition and when I built my first smoothbore and began shooting it I realized that when you don't spin things, accuracy can be iffy if it exists at all.  Not saying this is the case with arrows, but putting a helical on my feathers doesn't cost me a thing and is good insurance, if only from a confidence standpoint.
Always good to hear your thoughts.

[kerry]

Thanks for posting this.  I will check my shelf plate this evening.

[the rifleman]

Welcome sir.