Tuning education and headaches

[the rifleman]

I decided when I started this post to not name names on the two bows.  Just to note that they are both Left Hand reflex/deflex bows made by well known bowyers.  Bow A is the one that I have been shooting for several years---it is marked 50 pounds at 28".  Our scale showed it to be 48 and change at 28" and 42 pounds at my 26.25" draw length.  This bow absolutely needed a very week arrow to tune well.   I use full length beman MFX 600s and Gold Tip blems 1535s both with 200 grains up front.  Bareshafting and paper show them to be tuned.
Bow B is a longbow that I just got.  I bought it to have a lighter bow for practice as I always shoot too many arrows during stumping sessions and then am sore.  It is marked 43 pounds at 28.  Our scale shows it to be 43.9 at28 and 40 at my 26.25" draw.  This bow will not tune with the 1535 Gold Tips---even when I have cut the bareshaft down to 27" it shows weak with 125 tips and weaker still (as expected with 200 grain tips).  To verify that I was not getting a false reading I shot a new full length gold tip 1535 and it showed weaker still.  I had a carbon express 400 and tried it and it showed stiff (as expected).  I am figuring that in order to get a perfect tune with this bow I will need to move up to a 3555.  This has me puzzled as the bow is lighter in draw and the shelves seem cut to around same distance to center (although I can only eyeball this).  The same 1535s cut down even to 29" were too stiff for bow A.
At one point I gave in, mounted a Grizzly broadhead on a 29" 1535 and shot it---it shot where I was looking several times---should I give in and call this a tune?
Not sure what I plan to do as I had anticipated a 7 pound difference in draw weights, but ended up with a 2 pound difference.  I am guessing this is what "draw force curves" are.

[AkDan]

force draw curves is the application of weight per inch of draw with some sort of 'standard' base line as a reference.   I don't know the hole gimmic behind it, but to me any ways the only thing I'm interested in is seeing if a bow stacks or not.   These are not high performance bows, I don't expect them to be hot rods!  I wouldn't concern yourself with FD curves.   The curve will tell you if it stacks, has high early string weight etc.

As for tuning, tuning is what it is.  Bow lengths, handle designs (one being more forward or set back than the next etc), and how the relation of weight is transferred will all dictate spine.  Two different bows may want the exact same arrow, while two exact same bows from the same bowyer may want two different spine groups.   Don't get wrapped up too much about what people think it should be.    

In the end, you shoot what shoots out of the bow period!  Too many guys are wrapped around what should only to find out it doesn't.   There is no replacement for airtime.

[AZ_Longbow]

Be sure your nocks are not to tight, then feed the bow what it likes.

[Skipmaster1]

They like what they like.
Can't you just cut the 1535 shorter then the 29" and drop head weight if you need too.

If not jump up an arrow spine snd leave it long and front heavy.

I've found that trimming just a little carbon can change spine much quicker then changing head weights.

[kat]

"As for tuning, tuning is what it is. Bow lengths, handle designs (one being more forward or set back than the next etc), and how the relation of weight is transferred will all dictate spine. Two different bows may want the exact same arrow, while two exact same bows from the same bowyer may want two different spine groups. Don't get wrapped up too much about what people think it should be.

In the end, you shoot what shoots out of the bow period! Too many guys are wrapped around what should only to find out it doesn't. There is no replacement for airtime."

This has to be the best quote I have ever seen. Spot on.

[Sam McMichael]

Don't worry about what "they" say. Only pay attention to what your bow says. As those before have indicated, each bow has it own preferences.

[the rifleman]

Thanks for the posts.  This exercise did show me first hand that the only way to arrive at the correct arrow is by actually shooting/ tuning.  Sometimes reason doesn't work.  My lower poundage bow wants a stiffer arrow.  My 50 pound @28 dropped 6 pounds @ 26 while my 43 @ 28 dropped only 4 pounds @ 26.  Since scale showed my 50 to really be 48 and my 43 to really be closer to 44 I now have 2 bows within 2 pounds of each other.  My intent was to have a 7 or 8 pound difference.  Still have a lot to learn...

[GANDGOLF]

Ah, another wonderful reason to buy another bow !!  

[DaveT1963]

I use to really struggle to tune an arrow to the bow.  I attended Rick Welch's school a few years back and he taught me how to manipulate the rest and sight window, along with the nock set, to make a properly spined arrow shoot where I look.  I don't struggle anymore.

The thing is, fletching stabilizes the arrow's paradox.  stiffer/weaker spine just means how much it flexes thus moving the arrow right or left before the fletching stabilzes it.  The exact same thing can be accomplished with shelf material and building out/reducing the sight window.

Now I pretty much shoot the same 29 inch carbon arrow from ALL my bows.  I have just set the bows up to where it shoots where I look.  Yes you have to be reasonable with the spine selection - but the truth is I can make anything from 15/35s to 55/75s fly pretty dang good from all my bows.  I just settled on 55/75 and big nasty simmons out front.  I use three 5 inch feathers to stabilize the arrow and then use various materials on the shelf and build up the sight window as needed.  Now I can grab just about any of my longbows/recurves and the same exact arrow and shoot pretty consistently (to my ability) out to 25-30 yards.

There is always more then one way to get where you want to.  This methods works for me better then any other "tuning" process and made shooting multiple bows more fun and enjoyable. I no longer have to have a dozen arrows set up for each bow - I use the same arrow/broadhead in ALL my bows - ranging from 48 pounds to 65 pounds.

 Others may find traditional tuning works better for them?

[damascusdave]

I am forty or fifty bows into the process and still learning...I just bought a very nice 1961 Kodiak that is marked 45 pounds and was hoping it would be just over 50 at 30 inches...well it is more like 55 at 30 inches which just makes it another moose bow for me...I was hoping it would be more of a deer bow...the more I tune the more I find it is the string that makes the biggest difference

DDave

[the rifleman]

Dave,  I definitely agree with you on the string being a big factor is tuning.  The string on the lighter of my two bows is a dyna-flite 10 and it really sends that arrow downrange quickly.  Dave T--great post on changing sideplates and shelf material to tune.  I really like the concept of having multiple bows, but not having to come up with new arrows for each.  I am learning that there are lots of factors an lots of solutions in tuning...

[overbo]

If they are bows from 2 different bowyers, I would say there is a difference in cut past center. To try to see that by eye and not actually measure it can be inaccurate.

I have a 52lbs(27'') bow that tunes a 75-80lbs spine arrow cut to 27 1/2''. Another tunes a 55-60lbs spine arrow the same length and point weight but it's a 61lbs bow at my draw length. The difference is the 1st bow is cut 3/16'' past center and the 2nd is cut at center. Very difficult the see the difference by eye.

[Bob Morrison]

Your putting too much in what you read. Every bow will tell you what arrow you need for it to shoot the way you want it to.If it wants 35-55 that's what you need get.

[**DONOTDELETE**]

You've touched on a point about weighing bows that i thought i would try and explain.  There can be a big difference in an R/D long bow and a straight "D" long bow in the string angle at full draw. The limb design and how they bend determines the string angle at full draw.

When measuring two different bows weight & using a small steel hook, lets say you get 50# @ 28" on both limb designs..... But using a fingers hook the same width as the average size as 3 fingers (2.5")  you can, and will get different draw weights on these same two bows you just measured. How much difference depends on how different the string angle is.  

Note: All bows are not created equally in terms of efficiency and where the stacking point will be either.

If you take 2 bows marked the same draw weight and put them on a scale. Make note of the weight at 26" 27" 28" & 29" of draw. an average 45-50# long bow is going to have a steady increase of 2.5# -3 # per inch increase until it hits the stacking point and jumps to 3.5 to 4#'s in the last inch.
That stacking point will be a lot different on different length bows. Especially ASL designs, or straight "D" long bows.

Once you you get into R/D long bows where the working portion of the limbs can be manipulated, you'll find shorter bows can draw much further before your PPI  (pounds per inch) jumps up. You'l often find that the R/D long bows have a lower PPI for the same given weight at the tail end of the draw. But will have early weight at the front of the draw.

With a good recurve design, with a higher preload.
(tension on the string at brace height) this is amplified. Your early weight goes from 6 PPI to 5 to 4 to 3 in the first 4" of draw and continues to drop down to 2 PPI through out the draw cycle until it starts to go up again from 28-30" gradually to 2.5 ppi..... This is the draw force curve you hear about and can be charted..... There are exceptionally smooth drawing RC bows out there that will continue that low PPI and good string angle clear out to 32". The Sasquatch SS is a good example

Here is a little drawing that will help explain what i'm talking about....

The bottom line is that if you weigh a bow at 50# at 28" with a straight scale hook vs a fingers hook you can have as much as 4-5 pounds more draw weight with your fingers drawing the same 28". How much exactly depends on your bow design & where the stacking point is.

 

[**DONOTDELETE**]

Here is an example on a Sasquatch hybrid long bow. The amount of limb travel is another thing that determines the the string angle & performance level.