Very strange!! Arrow test.

[SEW]

I’ve been testing 6-7 different arrow configurations with my M380/1.5 TT/Optimizer/Airbrakes/Simms stabilizer/ T-36, Dr Stirrup everything, etc. IOWs, a true benchrest xbow. Testing at 70 & 80 yards in low to high winds.
I had a clear winner with near tie and the other arrows were performing very consistently. The arrows had consistent levels of accuracy,

That is until....


I decided to test them out of my BD400 with only Dr S string bumpers and Zeiss XB75. In repeated testing, arrow designs 1 & 3 reversed positions. Also, all 3 arrow sets grouped tighter. This is with multiple groups being shot and the differences being very consistent and repeatable.

I don’t think the arrow stress is much different between the M380 and BD400. Limbs are 54 and 54.5 respectively. I have no idea on why this disparity in testing has occurred.

Another finding. Shooting out to 80 yards, very little grouping size difference occurs whether a 2-7x crossbow scope is on a speed setting that is about 4 power or 36 power like the T-36 Weaver.

Basic findings: 20” seem more accurate than 18”, AL is at least as accurate as the best Spynal Tapps, Offset SK300s and Blazers are as accurate as helical Blazers when shooting field points and expandibles. Haven’t tested fixed BHs yet. Testing is in early phases.

The long inserts sold by Tapp Nation seem to help as does the insert in Dorge’s design (Firenock). Verdict is not conclusive concerning the Aerovane 2s compared to conventional vanes. Aerovane 2s and SK300s are the 2 vanes on the arrows trading places.



That’s all for now. More coming.

[janesy]

Interesting, I wonder if it has something the do with the more relaxed riser design the Bulldog uses over the Matrix..

Ive always though something launched slowly and or softly compared to a more harsh launch will have a possitive effect on ever aspect of arrow flight.
My theory is based on matrix vs micro. Seems the longer limbs allow for a softer launch and therefore less erratic effect on the arrow. Not very scientific, but makes sence to me.

[otisbrazwell]

interesting results sounds like 20" arrows for the bd 400

[Boo]

One thing worthy of mention is the physical weakness possibly created by the 6" long aluminim insert. The shaft will flex on launch and on impact. It will want to flex close to the center. This could cause a breakage or a spine loss where the insert ends. Conversely, the carbon insert allows some flex as does the epoxy that holds the inner tube.
Anyone have thoughts on this?

[janesy]

One thing worthy of mention is the physical weakness possibly created by the 6" long aluminim insert. The shaft will flex on launch and on impact. It will want to flex close to the center. This could cause a breakage or a spine loss where the insert ends. Conversely, the carbon insert allows some flex as does the epoxy that holds the inner tube.
Anyone have thoughts on this?

Interesting, or it could be the opposite effect and cause the first 6" to remain solid(obviously) essentially leaving only 14" to flex. Effectively creating a shorter stiffer arrow.
I'm not an arrow engineer, but I did stay in a holiday inn express last night.

[Boo]

One thing worthy of mention is the physical weakness possibly created by the 6" long aluminim insert. The shaft will flex on launch and on impact. It will want to flex close to the center. This could cause a breakage or a spine loss where the insert ends. Conversely, the carbon insert allows some flex as does the epoxy that holds the inner tube.
Anyone have thoughts on this?

Interesting, or it could be the opposite effect and cause the first 6" to remain solid(obviously) essentially leaving only 14" to flex. Effectively creating a shorter stiffer arrow.
I'm not an arrow engineer, but I did stay in a holiday inn express last night.

Badda book, badda boom! Free waffles!

[SEW]

There is definitely a difference in the launch feeling of the 2 riser/limb configurations. I expect the M380 is harsher on the arrow. More testing later this week.
Tiller is dead on as closely as I can measure.

[Boo]

Steve, was there any weather change? Front coming in? Temperature drop? Any environmental changes?

[Back strap]

:

Steve, was there any weather change? Front coming in? Temperature drop? Any environmental changes?

Strange response

[DMc]

Sharp or large changes in weather can bring with them a change air density. This, in turn, can affect flight characteristics of fletching and other components.

[Back strap]

Been about a month or so since I talked to Steve. I would think this is recent fair weather testing. Might be wrong though

[SEW]

Steve, was there any weather change? Front coming in? Temperature drop? Any environmental changes?

Significant change.

All initial testing was with the M380 with every possible accessory, 36x #cope, Optimizer . A Hart Windage adjustable scope and rear bag was used . The testing was done in 50s and 60s F temps with moderate wind at most (below 10 mph).

The last tests were with winds over 10 mph, occasionally up to 20 mph. The major difference was the use of a BD400, TT 2.5#,
and an XB75. Temps were about 10 degrees(F) cooler, winds significantly higher but actual groups sizes were smaller . This is still inexplicable.
Tiller appears perfect on the M380. Group size differences could come from scope problems and/or Optimizer.

Whatever, groups tightened in spite of a much lower power scope (XB75 set on 350-375), and much windier conditions.

Unfortunately, this week is cram packed with obligations that will prevent any xbow shooting. More later.

[SEW]

Sharp or large changes in weather can bring with them a change air density. This, in turn, can affect flight characteristics of fletching and other components.

Only significant difference is the intentional testing in windy conditions the last 2 times out.

I’m testing arrows from a # of sources including self. One of the outside sources includes a vane and vane configuration that supposedly helps resist xwind deflection. Likewise, helical verses offset verses straight fletch supposedly helps.

Incidentally, for xwind deflection measurements a major complication presents.. The more an arrow spins the more it is displaced left or right from straight fletch. Therefore each fletching arrangement needs the scope to be adjusted to center the arrow in a no wind condition; then, that configuration can be tested with varying xwinds .

Example of the sighting problem, if a straight fletch hits dead on at 80 yards, then the vanes are set in left offset, the arrow may then hit 3-4 “ left, in radical helical such as Bolt fletched Blazers, then the arrow may hit 6-7” left, and if Dorge’s Aerovane 2s are used, maybe 8-10” left. What I’ve done is to record where the center of the group of each arrow design impacts left or right of the aimpoint in an almost no wind situation, and then measure
From that point for actual xwind deflection.
YES, the more the spin, the less the deflection. Additionally, the more the spin, the more consistent the shaft spine needs to be. Aluminum has the most consistent shaft spine.

[DMc]

Barometric pressure and humidity also have an effect on how things fly. I honestly can't see it making a difference for most of us, but you are pushing the limits of what is possible, it seems.

[SEW]

Barometric pressure and humidity also have an effect on how things fly. I honestly can't see it making a difference for most of us, but you are pushing the limits of what is possible, it seems.

Atmospheric conditions certainly affects things that fly or glide thru the air, but I don’t think that’s a factor. Nor do I think that aerodynamic limits are being stretched yet. I do think that launch stress and the faster speeds cause a rotational stress beyond what nearly all shafts can handle.

There a 2 schools of thought concerning arrows launch stress. One is that the entire energy (energy under the force/draw curve) is the major determinate on the arrow shaft’s stress. The other is that the maximum instantaneous stress is what needs to be considered. Examining an Easton arrow chart seems to support the latter in that a recurve bow of a given poundage(no letoff) requires a stiffer spine than a hard cam which requires more than a round wheel.
The M380 is releasing 260# instantly against the arrow nock vs #280 on the BD400 vs 24# on my BT Solution (120#/80% letoff).

In theory, a faster rotating projectile (arrow in this case) will be more stable in flight AND less affected by xwind. However, for this to hold true, the torsional rigidity and uniformity need to be excellent. Carbon arrows do not have a uniform spine nor are as compositionally consistent as desired. Aluminum arrows win in this respect. They are more inform in both respects.

The 2 xbows’ speeds and launch stresses should be close enough to not be any factor in any of the above.

I’m still at a loss.