MAC Performance - Black Fly Upscale Survey Poll + Build Thread

gfunk said:

I did have initial concerns, but so far I've seen 2 ground tests and 4 flights with this configuration and they all came out fine. It's a snug fit in the NC, but I think of it like a plastic injection mold with draft angle to promote release. As soon as the chute/nomex move a little, it's definitely coming out (unlike a straight walled payload tube).

I make a longish bundle of the Z-folded kevlar and secure it with one of my wife's hair ties. Since the ground testing I have started I placing the kevlar bundle under the last wrap of the nomex burrito roll, so that probably helps it all come out together. I will document my packing the next time I prepare this rocket (for a K695R).

I considered placing the charge in the nose tip, but this seemed like a PITA and more likely to damage or tangle the wire running up to the ematch. I like the simplicity of wiring ematches directly to the altimeter and didn't want to extend the leads to reach the nose tip.

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mpitfield said:

Am I correct in noting that you tested without the brass tip? I will be doing my ground testing in the next couple of weeks and I plan to use the aluminium one for this.

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gfunk said:

Busted.

Ahem, neither. I ground tested my 4" FiberMax NC and convinced myself the WM NC with metal tip for the Black Fly was the same diameter, coupler engagement, # shear pins, bulkhead charge cups, chute and harness, similar cone volume, etc and didn't warrant additional testing. Hey, it worked!

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• Live with it? It still seems to deploy chutes as expected.
• Would over sizing the baro ports help?
• Further sand the NC/vent band/booster interface? (ugh)

• The thin air at Hartsel (8,800') helped? Ha.
• That tail cone is slippery!
• AeroTech had a really potent batch of Redline propellant?

gfunk said:

Video from the 4" Fly's K695R flight yesterday in Hartsel. Really fun flight, super straight. Recovered 1.35 miles away.

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rfjustin said:

That still near the end of the video with your son (im assuming?) is awesome!

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gfunk said:

My 4" Black Fly has flown twice now, and both times the dual RRC3 altimeters are reporting altitudes well over my Open Rocket sims. Both were wonderfully straight, beautiful, nominal flights.

J540R: Expected ~6,000, reported 6,900'
K695R: Expected ~8,000, reported 10,600'

With the K695 flight there are spikes in the velocity data so I wonder if something is funky with my baro ports. They are certainly drilled perpendicular to the tube, the holes are clean, and were sized appropriately based on port calculators. There are 3 holes, a little over 1/8" dia, IIRC I drilled with a #29, 0.136". The #2-56 shear screw heads are 60 degrees offset from the 3 baro ports. I sanded the NC, vent band, booster tubes as pinned to make them as smooth as possible, but there is a little irregularity here where the canvas tubes meet the fiberglass NC.

I fly the exact same HED electronics sled in my AMW Fibermax and see great agreement with sims, and no spikes. Same size/number of baro ports and pins. That has a different NC profile though and even with a K456 hasn't gone *that* fast.

Thoughts on what I should do?

• Live with it? It still seems to deploy chutes as expected.
• Would over sizing the baro ports help?
• Further sand the NC/vent band/booster interface? (ugh)

Unlikely:

• The thin air at Hartsel (8,800') helped? Ha.
• That tail cone is slippery!
• AeroTech had a really potent batch of Redline propellant?

RRC3 data and ORK file attached. Appreciate any advice!

View attachment 358562 View attachment 358563 View attachment 358564 View attachment 358565

Click to expand...

gfunk said:

My 4" Black Fly has flown twice now, and both times the dual RRC3 altimeters are reporting altitudes well over my Open Rocket sims. Both were wonderfully straight, beautiful, nominal flights.

J540R: Expected ~6,000, reported 6,900'
K695R: Expected ~8,000, reported 10,600'

With the K695 flight there are spikes in the velocity data so I wonder if something is funky with my baro ports. They are certainly drilled perpendicular to the tube, the holes are clean, and were sized appropriately based on port calculators. There are 3 holes, a little over 1/8" dia, IIRC I drilled with a #29, 0.136". The #2-56 shear screw heads are 60 degrees offset from the 3 baro ports. I sanded the NC, vent band, booster tubes as pinned to make them as smooth as possible, but there is a little irregularity here where the canvas tubes meet the fiberglass NC.

I fly the exact same HED electronics sled in my AMW Fibermax and see great agreement with sims, and no spikes. Same size/number of baro ports and pins. That has a different NC profile though and even with a K456 hasn't gone *that* fast.

Thoughts on what I should do?

• Live with it? It still seems to deploy chutes as expected.
• Would over sizing the baro ports help?
• Further sand the NC/vent band/booster interface? (ugh)

Unlikely:

• The thin air at Hartsel (8,800') helped? Ha.
• That tail cone is slippery!
• AeroTech had a really potent batch of Redline propellant?

RRC3 data and ORK file attached. Appreciate any advice!

View attachment 358562 View attachment 358563 View attachment 358564 View attachment 358565

Click to expand...

mpitfield said:

George how are the altimeter logs since you last launched, still spikes, if not what did you do to mitigate it?

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gfunk said:

After drilling the 3 baro ports larger (11/64" dia) and re-aligning the NC/vent band to be as smooth as possible I still had spikes in the velocity data for both RRC3s. Altitude data was much closer to the simulations, and was supported by what I saw on the MW T3 GPS track points. I kind of think AeroTech had an extra hot Redline batch in October 2017 which contributed to outperforming sims. Both those K695R and J540R motors had similar date codes.

By the way, here's the L1000W launch video:


Next flight for this 'Fly will be a K375NW to about the same altitude but slower, whenever A/T 2560 cases are available (pre-ordered since June). I'll likely make the NC/vent/booster transition smoother this winter and repaint.

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