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  #1  
Old 08-14-2005, 10:59 AM
Eagle3 Eagle3 is offline
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Default Cherokee DD First Flight Report

I flew my Cherokee DD yesterday at the JMRC launch held at Michigan International Speedway (MIS). It flew with a D12-0 / C11-6 stack and nothing in the payload bay. The wind had picked up a little by the time I got to flying it, so I gave it a slight launch angle to try and counter any weather-cocking. It launched straight and true. It began falling over midway through the C11 burn and was moving pretty fast at ejection with just a slight nose up angle. The chute shredded and after falling parallel for ~200' it became stable and cored in with the payload trailing close behind. Amazingly it missed a paved path by 2'! Even more amazing.... zero damage! I had soaked the front 3" of body tube with thin CA and it had no problem cookie cutting the wet sod. I owe the lack of tube crimping to the Flis kits ejection baffle.

Next test will be a D12 / D12 stack and dummy payload equalling the weight of the boostervision cam. Here a couple pics.

PS - that's also my Cox Shuttle America on the red rack. I had three great flights with it on C6-3's.
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  #2  
Old 08-14-2005, 12:39 PM
Ltvscout Ltvscout is offline
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Cool stuff, Maynard. Did you happen to get a core sample picture before pulling it out of the ground?
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  #3  
Old 08-14-2005, 12:45 PM
six-o-one six-o-one is offline
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Eagle, congrats on being first up. Glad there was no damage. Anxious to hear about the payload flights. And, hey, great photos!
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Old 08-14-2005, 01:06 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by Eagle3
I flew my Cherokee DD yesterday at the JMRC launch held at Michigan International Speedway (MIS). It flew with a D12-0 / C11-6 stack and nothing in the payload bay.


C11-6...?

Quote:
The wind had picked up a little by the time I got to flying it, so I gave it a slight launch angle to try and counter any weather-cocking. It launched straight and true. It began falling over midway through the C11 burn and was moving pretty fast at ejection with just a slight nose up angle. The chute shredded and after falling parallel for ~200' it became stable and cored in with the payload trailing close behind.


RockSim gives the following numbers for deployment V:

D12-0/C11-5 combination deploys at ~47 fps, while still in the upward half of the flight.

D12-0/C11-7 combination deploys at ~18 fps post-apogee.

Sounds like this was a 5 second delay, and it shredded pre-apogee...

Quote:
Amazingly it missed a paved path by 2'! Even more amazing.... zero damage! I had soaked the front 3" of body tube with thin CA and it had no problem cookie cutting the wet sod. I owe the lack of tube crimping to the Flis kits ejection baffle.

Next test will be a D12 / D12 stack and dummy payload equalling the weight of the boostervision cam. Here a couple pics.


Sounds like it was still a good flight up to deployment...

Unless someone else has flown without crowing...er, I mean, without speaking up, I think you have just qualified the first flight of a Cherokee Double-D anywhere. Congrats are in order. For the record, RockSim suggests you crossed the 1000' line with that flight. Even with the tilted rod, you may have done it, or come very close.

You're going to hate this, but if you had gone with the C6-5 you would have gained another 150', and your deployment V would have only been ~27 fps. Probably wouldn't have seen the shred.
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  #5  
Old 08-14-2005, 01:58 PM
Eagle3 Eagle3 is offline
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Quote:
Originally Posted by Ltvscout
Cool stuff, Maynard. Did you happen to get a core sample picture before pulling it out of the ground?


I had dropped my camera off at my car on the way to pick it up or I would have.


Quote:
Originally Posted by six-o-one
Eagle, congrats on being first up. Glad there was no damage. Anxious to hear about the payload flights. And, hey, great photos!


Thanks! I'm working on the rest of the launch photos and will post something in Mission Control when they're online.

Quote:
Originally Posted by CPMcGraw
C11-6...?


You're right, it was a 5

Quote:
Originally Posted by CPMcGraw
RockSim gives the following numbers for deployment V:

D12-0/C11-5 combination deploys at ~47 fps, while still in the upward half of the flight.

D12-0/C11-7 combination deploys at ~18 fps post-apogee.

Sounds like this was a 5 second delay, and it shredded pre-apogee...


Problem is it was tipping over and had gone ballistic. I wish I had used a D12-7 in hindsight, but glad I didn't go with a C11-7. It most certainly had been going down at ejection and somewhat faster. You know.... there's always the chance that I forgot to connect the chute.... nahhhhhh!

Quote:
Originally Posted by CPMcGraw
Sounds like it was still a good flight up to deployment...


It was straight as a rail during D12-0 boost and I'm guessing if I had launched it with a zero angle it might have stayed straight with the C11, but I'd be worried using a C11 again if it ever weathercocks.

Quote:
Originally Posted by CPMcGraw
Unless someone else has flown without crowing...er, I mean, without speaking up, I think you have just qualified the first flight of a Cherokee Double-D anywhere. Congrats are in order. For the record, RockSim suggests you crossed the 1000' line with that flight. Even with the tilted rod, you may have done it, or come very close.


Thanks, but I doubt it came that close due to the tip over under C11 power. Maybe 800', but I'm just guessing.

Quote:
Originally Posted by CPMcGraw
You're going to hate this, but if you had gone with the C6-5 you would have gained another 150', and your deployment V would have only been ~27 fps. Probably wouldn't have seen the shred.


I want to play with this in Rocksim and see how it handles launch angles and payload weights.
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Old 08-14-2005, 02:09 PM
A Fish Named Wallyum A Fish Named Wallyum is offline
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How is it flying at MIS? I know it's a big track, but it seems that it would be easy to wind up outside on recovery. Is this strictly ModRoc, or do they also allow HP?
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Old 08-14-2005, 02:48 PM
Eagle3 Eagle3 is offline
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Quote:
Originally Posted by A Fish Named Wallyum
How is it flying at MIS? I know it's a big track, but it seems that it would be easy to wind up outside on recovery. Is this strictly ModRoc, or do they also allow HP?


We fly on the North Campgound and it's HUGE!!! We've flown dual deployment M's out of there for sure. I don't know if there's been anything launched larger than that before I started flying there. The only place we have to worry about is the track itself (because there's a driving school going on almost all the time) and one fussy neighbor to the west. Southwest winds are prevelent, so we usually don't have to worry too much.

There's a farmfield that's even bigger that we fly on once the crops come up amd until they seed.
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Old 08-14-2005, 08:28 PM
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Quote:
Originally Posted by Eagle3
It most certainly had been going down at ejection and somewhat faster. You know.... there's always the chance that I forgot to connect the chute.... nahhhhhh!


I don't know what you were using in addition to the parachute shroud lines to make the connection, but recently on a Quest Gamma Ray, the chute opened at a high-enough V to break a connecting line between a snap link and the base of the transition. My guess is still that you suffered a shred due to exccessive V at the moment of deployment.

I still think you crossed 1000', based on my quick-n-dirty numbers game:

Motor combination: D12-0/C11-5...

0 degrees tilt, 1052', 47.35 fps, 10' below apogee, moving upward
5 degrees tilt, 1050', 48.19 fps, 10' below apogee, moving upward
10 degrees tilt, 1002', 65.73 fps, 7' below apogee, moving upward
15 degrees tilt, 968', 75.68 fps, 4' below apogee, moving upward
20 degrees tilt, 862', 100 fps, 2' below apogee, moving upward


Unless you had the rod more than 10 degrees from vertical, you pegged 1000'. Notice how rapidly the deployment V goes up, and how little altitude there is remaining in the flight. Good indicator that the model is bookin' it horizontally. Also notice, all of these sim-flights deployed pre-apogee...

I'm not at all surprised the chute came apart. Did anyone ever find it's remains afterward?
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  #9  
Old 08-15-2005, 07:48 AM
Eagle3 Eagle3 is offline
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I just wonder how accurate Rocksim plots the flight angle for the entire trajectory. In the few sims I ran it looks like it doesn't. The most downrange distance I could get was 100' when mine flew at least 300' downrange at ejection. I'll weigh my model and see how close it is to the sim.
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Old 08-15-2005, 11:44 AM
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I based my sims on the long-payload version, which is what I recall your version as being (7.5"). Also, I just re-ran the simulations using RockSim's calculations (the ones I posted were Barrowman), but the numbers don't really change that much.

You didn't include any weight in the payload section, did you? My figures were based on a no-payload flight. If you had any weight at all up there, that would change the simulation.

Empty weight of this model should be about 6.5 oz, give or take a fraction of an ounce...
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