Effect of refinishing on bow speed

[McDave]

I recently had one of my bows refinished.  It looks great.  Only problem is that the gap at 50 yards is more than it was before.  I wondered about that, so I comped the bow and compared with old records.  It seems that arrow speed has decreased about 5 fps since the refinishing.  I wonder if this could be because of the added weight of the new coats of finish?  Can't think of any other reason.

[PEARL DRUMS]

Its not from finish weight, not a chance. If anything the fella that refinished it may have hit the sides of the limbs a bit too much and knocked a pound or so off. Even so, a pound or two wont make a 5 fps difference.

[PEARL DRUMS]

Something just occurred to me. Did the new rug thickness change causing your "point on" to change?

[Orion]

Agree that it's not the weight of the finish.  Maybe the fella sanded too much off the back and belly of the limbs as well and actually reduced the poundage.  No way of knowing for sure unless you measured it before and after, though your change in speed is a pretty good surrogate for draw weight.

[Orion]

If not the rug, nock point and brace height might also have changed a little. Same string material?

[Orion]

[McDave]

Nock point and brace height are the same as before.  I put on a new Martin rug rest which may be a little higher than the old one, but I would think that difference would be taken into account when I set my nock point on the new string.  I did tell them to throw in a new string, since the old one had been on there a long time.  This is the same company that made the bow, and the new string is no doubt whatever they're sending out with their new bows.  I didn't give this much thought, and I don't remember what my old string was.  If it was one I made myself, it is possible that it was better quality than the stock string.  Maybe I should make another new string myself, and see if that makes any difference.

It hadn't occurred to me to re-weigh the bow.  As far as I can tell, the weight hasn't changed.  I keep notes on all of these things, and while the spring scale I use probably isn't all that accurate, I use the same scale for all my weight measurements, and so hopefully it at least is consistently inaccurate from one use to the next.

I could accept the fact that my chronograph could change, or my form could change over time, but the fact remains that my 50 yard gap hasn't changed with other comparable bows, while it has changed with this one.  And the change seems to be related to a change in performance of the bow, as opposed to other factors that could change my 50 yard gap, since there is a correlating change in arrow velocity from the last time I measured it.

BTW, I like to use the 50 yard gap because it is pretty close to point on with all of my bows, so changes are easy to see.  In the tournaments I shoot in, we have a 50 yard max distance for trad shooters, so I get a lot of practice shooting 50 yard shots.  Plus, when you blow a shot at 50 yards, it's pretty obvious, so you can ignore it when you're trying to measure things.

[Orion]

I'm betting on the string being the difference.

I'm with the string material being different than what was on it before. Changing string material CAN make a huge difference in tune and performance. Make a new string out of the same material you had on it before and report back!

Bisch

[McDave]

This morning I made a new string out of Dynaflight 10, 12 strands with 4 additional padding strands in the loops.  Initial chrono readings indicate the bow is about 2 fps faster with this string compared with the string supplied by the bowyer.  Possibly this difference might increase a little when the string is fully stretched.  The real test will be to see the effect on my 50 yard gap the next time I go to the range, which will probably be tomorrow.

My point on before the bow was refinished was about 50 yards. After being refinished, it was hitting about a foot low at 50 yards.  Not that I'm that precise of a shot at 50 yards, but I can tell that about 5/6 arrows are hitting below the bullseye rather than being loosely grouped around it.

[M60gunner]

I buy into the string material theory as well. Seen it happen going from old D-97 to 450+ years ago. Now with BCY X I get that and no stretch.

[Holm-Made]

Im betting the bow lost a pound or more during the refinish.

[McDave]

Originally posted by Holm-Made:
Im betting the bow lost a pound or more during the refinish.

That's very possible.  I doubt if my spring scale is accurate within one pound.  That's what I'm beginning to think as well: 2-3 fps due to a change in string and 2-3 fps due to sanding.

Oh well, I'm getting to the age where I'm having to go down in weight (bow weight, that is) anyway.

[katman]

Did it also effect arrow tune? If you lost performance should be a little stiffer.

Another thought, is tiller the same as it was?

[Orion]

I think you've got it Dave, perhaps a little due to reduced weight and a little due to string material.  Just shorten your arrow by 1/4-inch and you'll be back in business.  

[McDave]

Tiller is +3/16".  I don't know what it was before, but it tunes to the same nock height of 1/2" as it did before, so I would guess the tiller is okay.  It also tunes perfectly with no nock right or left with the same bare shaft as before, which is a little puzzling, since as Katman said, if it lost performance one would expect it to show stiff.  It is possible that it might have tuned a little weak before, since I will accept a little weak on a bare shaft assuming the feathers will stiffen it up.

At the range this morning, the gap at 50 yards seems to have decreased using the new string.  It still may be hitting a little low, but is within my level of confusion now, so I wouldn't say for sure until I shoot many more arrows at 50 yards and decide what's real and what are just day to day fluctuations.

Thanks a lot for all your help, guys.  This discussion has been useful to me.

[Orion]

If there was a reduction in draw weight, it's likely so small that I wouldn't expect it to show up in bare shafting.  On the one hand, most bows will shoot a range of spines well. Or, stated in reverse, the same spine arrow will shoot out of different weight bows, not hugely different, of course.  

On top of that, most of us don't have form good enough to tell the difference. However, if you're detecting small differences in impact at 50 yards, your form is no doubt pretty good. Seems as if the new string has recovered most of the small bit of performance that was lost. And, as you noted earlier, the bow might have lost a half-pound or pound of draw weight in the refinishing process. Just might be a matter of familiarizing yourself with the bow again.