Stiffer than expected tuning question

[Skidkid]

Bow: Habu Vyperkahn, 62", 51#@28, hybrid recurve. I have 28.5 draw, RH

I just picked this bow up used, bow is from 05 and in like new shape. I'm trying to get various arrows tuned up. Looking at more lightweight set up for 3d and 10gpi arrows for IBO Trad Hunter which I would also use for hunting set up which I prefer 175 up front. Arrows I have GT Traditional 400s and 340s, as well as Black Eagle Carnivore 350s. I was expecting the 400s to work but ever length/weight variation comes up weak. So I started working with 340s and 350s. I was able to bareshaft the 340s with 30" and 135 up front. The BE 350s flew great at 30" and 150. This is much stiffer than I had expected. This causes a few problems for me. 30" arrow is as short  as I can go to clear shelf for broadheads. This leaves me no room to get to 175 up front, which is the set of Zwickey Eskimos that I like. This also leaves my arrows light on the 10gpi target.

What could contribute to the tune requiring arrows so much stiffer than one would expect, based on charts and Three Rivers spine calc? I have always needed arrows a bit stiffer than you would expect for a particular draw weight, but with bows in low to mid 40s, it wasn't an issue. I could tune arrows up that worked without problem. In this instance, I don't have the room for adjustment to make arrows that fit my need. What might I be doing as a shooter that would influence the arrows this way?

I have heard Big Jim talk about arrows too stiff that get false positive clean flight. I tried every combo from 500s to 400s and all are consistently weak. With the 340/350 arrows I have bareshaft tuned, they fly clean from 10-30 yards without issue, so it doesn't seem like a false tune. Any insight is appreciated.

[LookMomNoSights]

I will be watching this because it seems very odd to me and I'm curious now............
All day long,  a 500 spine arrow should be your poison I would think......especially with only 175 up front. At your desired arrow length I think you'd be on the edge heading to a 400 only if you were to be heavier at the point,  say 250 give or take.
I can't imagine how a 400 would be too weak, never mind the stiffers you mentioned.
Interesting.   Something doesn't seem right.
Is that Habu cut past center?  I don't know much about them at all other than them being sought after ...........

[LookMomNoSights]

Have you checked draw weight with a scale at your draw length just for grins?

[Skidkid]

I have not checked draw weight with scale, I will next time I can. Draw weight "feels" consistent with 51 for what its worth

[Smguinnip]

my guess is that this bow is cut further past center that your other bows, i have had luck dynamically stiffening arrows by adding string silencers such as beaver balls and para cord sleeves.

[Orion]

I'm a bit puzzled by your draw length/arrow length statements.  If your draws length is 28.5, you should have 1 1/2 inches of arrow behind the broadhead in front of the riser.  You should be able to go an inch shorter and still have adequate clearance from the front of the bow. 

Might try taking a half inch off of the 400s, which will stiffen them up quite a bit and still give adequate clearance.  Or, perhaps your draw is longer than 28.5 inches, and you're actually drawing a little more weight than you think.  Regardless, I agree with LM.  Good idea to check the draw weight at your draw length.   

[Skidkid]

I am using the throat of the handle as reference point for draw length. 30" arrow insert comes to very front of shelf

I talked to Chris Cox, he also believed that a 400 spine would be the right arrow for tuning.

[McDave]

How is your nock high/low bareshaft indication?  We tend to look at nock high/low and nock right/left as being separate tuning adjustments, but I have found that they work in tandem.  If one is off by more than a little, it also affects the other, sometimes in unpredictable ways.

I agree with others that a good next step would be to start trimming length off the .400 bareshaft until you only have 1/2” sticking out in front of the bow.

Is your experience that in general you can successfully bareshaft tune without issues?  If that's the case, I think we can rule out form issues as being part of the problem.

Edit: I just saw your post above mine.  Draw length is equal to the distance to the pivot point of the bow (i.e., the throat) + 1 3/4”.  By that measurement, your draw length is really 30” (or possibly even a tad more), not 28.5”.   This changes things and could explain why a .400 spine shaft really could be too weak, because your “51#” bow could really be a 57# bow at your DL.

[Skidkid]

For form reference, I can group a set of "tuned" bareshafts at 30 yards in 3" circumference. I certainly may have form problems but I atleast have same problems pretty consistently from shot to shot.

Nock height is the first thing I work on, I start higher than I expect and work my way down. I believe nock point is good to go right now, sometimes I tweak nock height to try and manipulate trajectory but right now flecthed and bareshaft are on same plane

[Kirkll]

I’m having a tough time seeing the need for 350 spine shafts on that draw weight and length. If you are showing weak on 400’s I’m thinking you must be  3/16” cut past center on your bow. All ya need to do is pad your strike plate a bit to tune those things just fine….

[Skidkid]

Well my misunderstanding on draw length certainly contributes to the issue. Based on the reference point being the back face of the bow, my DL would be 30". So that explains the discrepancy in expectations for calculator. With that being said, I suppose I will need to figure out some weight adjustments to rear of arrow to increase overall weight and increase point weight.

[Kirkll]

If your draw weight is 50-51 @ 28 and you are drawing 30" you are looking at 56-57 pounds.  That's exactly my draw weight and draw length, and i tune 400's just fine. I use a brass insert about 75 grains and 160 grain tips @ 30.5" length..... You should be fine...

[Orion]

OK, now that we've established that your draw length is longer than we thought and that you're pulling more weight, the .400s become a little more iffy, perhaps not so much iffy as at the end of its spine range.  If memory serves, the Vyperkahn is cut at least to center.  If it's cut past center, and even if it's only city to center, you might build out the side plate a bit to get the .400s flying well, as Kirkil suggests. Or, accept the fact that 350s work nicely for you regardless of what the charts say.  Good luck.   

[Skidkid]

Thanks for the help everyone. I might try building out the strike plate, as of right now there is only soft velcro material

[McDave]

I understand that building out a strike plate can compensate for overly weak spined arrows.  My question is, why would anyone actually want to do that?  It seems to me that there are advantages in keeping the arrow close to the centerline of the bow that would be lost by building out the sideplate.  Wouldn't it be better to just keep tuning until an arrow was made that was in tune close to centershot?

[Vroomvroom]

OK, now that we've established that your draw length is longer than we thought and that you're pulling more weight, the .400s become a little more iffy, perhaps not so much iffy as at the end of its spine range.  If memory serves, the Vyperkahn is cut at least to center.  If it's cut past center, and even if it's only city to center, you might build out the shelf a bit to get the .400s flying well, as Kirkil suggests. Or, accept the fact that 350s work nicely for you regardless of what the charts say.  Good luck.

Kirkll, I notice this post.  I’m pulling I think about 53 lbs. the Savannah I have is a 55 lb Martin at 28”.   I think I’m 26.5-27”.       It’s a little lighter than you, but also noticed my tips are 125 grains and insert is 50 grains, about 60 grains less than you. But the  arrow is the same length and spine.  So very close.  Mine seem to fly ok.  I posted a day or two ago as I purchased 500s this time for a roots recurve, 49@28.   B55 string so I’m hoping they are not too weak.  The Savannah arrows are gt trads.     These 500s will be gt trad classic xts.  Which are heavy and x as mallee diameter. So hoping that stiffens them up as well as the Dacron string

[Orion]

McDave.  As I indicated in my last post, the op could either build out the side plate or use the heavier spined arrows.  I suppose it would depend on how many 400 shafts he has and if he wants to use those instead of 350s.  One wouldn't build out the side plate and then order arrows on the weak side, but if most of the arrows one has are on the weak side, building out the side plate makes them usable.