High Tech Trad(chrono testing)

[Kimall]

I was lucky enough today to get a chrono for a day or so and was able to test my trad bows through it with some interesting results.It is very hard to guess how fast a bow is just by shooting it and this is a real bull@#$% stopper when it comes to talking about how fast a bow is.
I tried a couple of differant set ups on the Robertson and the Defiant so here are the results.I weighted both bows on the scale first and at my drw lenght of about 27 1/2-28 they both pulled around 61 pound so this made it easier to compare results with them being so close.I tried the Robertson (which is a recurve) with the string that came on it and one of my own I made this week and this string is made out off 8125 with 12 strands and the supplied is fastflight of about 16 strands both with woolies on them and both sound very quiet.The longbow has a 8125 string also but no other string and this helped it a bit in the test I believe.Arrows where the same carbons shot out of both bows in two differant weights.29 inchs with 4 four inch sheild cut feathers and 200 grain points with rubber up the hv ones.Arrow weights are 740 grains which is about 12.2 grains per pound and the lighter ones being only 480 grains which is only just under 8 grains per pound.I am not going to hunt with these lighter arrows as I feel they are a bit unstable in flight but it was an interesting weight to uses as a bottom weight for testing.I checked with the bow maker and he said it would not harm the bow in any way.
Recurve Supplied string
740grn-----164 feet per sec
480grn-----188 fps
Recurve Kimall String
740grn------172 fps
480grn------196fps :shock:
Longbow
740grn------150 fps
480grn------190 fps
These figs are the averages after at least 10 shots with each setup and it started to show a very clear picture.A couple of things the suprised me a bit was that my string was consistantly faster by enough to make a differance on arrow flight down range.The other thing that is often said is that longbows really shine with a extra heavey arrow and they do but as shown here they do REAL well with a lighter arrow as the weight of the arrow got less the speed diff was not as great between the two bows.The very fastest I got with the lighter arrow was from the curve at 199.5 fps.
and as much as I would like to say I cracked the 200 it was not to be and I may have to change the name of the bow to "ALMOST" or "199" :D
I have some heritage shafts coming in a softer spine so I should be able to make up some arrows about the middle of these and should give me about 180 fps with 10 grains per pound and these should be a nice hunting and field shooting balance.I hope this was of interest for some and thanks for reading.Any question just shoot.
Cheers KIM

[Piggy]

thanks mate that was an interesting result

[rory]

Nice tests mate, interesting 8) Thanks for sharing :wink:

[ed]

Thanks Kim, an interesting result. I will have to start making different strings (bye bye dacron!).
A bowyer I know in Adelaide says that for most longbows the glass is too thick and impedes performance. I also think the main thing about longbows for the heavy arrow debates was to do with deep cross section vs flatbow. So it may have some bearing depending on what type of longbow you have.
Aren't most chrono's these days basically standardised at 500gns? I like your idea better, and maybe best if it was standardised at 10gns per pound draw. Both bows performed very well for 61#s eh!

[perry]

It is always interesting to watch an arrow zap through a chronograph but it is best to have an accurate bow first if it happens to shoot fast thats a bonus . I must be a miserable bugger forgive me I just think that to much emphasis is placed on speed a hangup from the compounders . regards Perry

[Kimall]

Perry the time was not spent to get faster arrow flight only to find the best balance of weight and speed.There are so many that just go down the heavier the better path because that is what has been said for so long but when I settled on the mid weight arrows I also found that they seemed to penertrate better than the real heavy ones.There must be a point where the two lines cross between speed and weight for best results and I feel I have found it with this bow now.
Cheers KIM

[perry]

Im pleased you have gone out to findout for yourself Kimall instead of following the crowd , you can learn so much of this great sport of ours simply by a bit of experimentation . regards Perry

[pete w]

Glad to see you tried good strings.
This is the cheapest boost to performance you can get. That $20.00 string gives what would take a new bow to deliver.

I shoot 10 strands of DF97 or8125 and always pad the loops to 16 or 18 strands for tip insurance.

If you want to compare bows shoot a measured arrow at 28" and mark the riser where the 28" mark has to be , {1 3/4" past the low point of the grip}use a spoter to coach your draw . Hold and release at 28".
Use the standard 9 grains per pound drawn, and you will be able to compare any weight bow to any other bow.

The chrono is a great tool to see how consistant your normal draw is. 10 Fps spread is not unusual to see with many shooters.

Also when a bow is first strung it will shoot 6 to 10 FpS faster after 10 shots than it will on the first shot.

Silencer choice / placement can vary the speeds up to 8 or 10 FPS and have the same silencing effect.
Tied nock points are about 2 FPS faster than brass ones.

None of these are earth shaking, but ad them all up and the gain can be. The eye can not detect the small changes alone, but all together they can be very signifigant, and only a chronograph can tell you when you gain or loose.

Sometimes raw numbers are misleading. We may draw one bow up to an inch farther than another design. Slip a marked arrow on the bow and have a spotter tell you how far you draw that bow, or slip a cardboard piece on the arrow, draw and let down, then measure the shaft. This can explain why one bow sems faster or slower if you draw it diferent. The bow may be letting you draw farther and you gain because of the riser design.