Cherokee DD First Flight Report

[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. 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.

[Ltvscout]

Cool stuff, Maynard. Did you happen to get a core sample picture before pulling it out of the ground? ;)

[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!

[CPMcGraw]

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...?

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...

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.

[Eagle3]

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. ;)



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.

C11-6...?

You're right, it was a 5

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! ;)


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.


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.


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.

[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? :cool:

[Eagle3]

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? :cool:

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.

[CPMcGraw]

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?

[Eagle3]

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.

[CPMcGraw]

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...

[CPMcGraw]

The most downrange distance I could get was 100' when mine flew at least 300' downrange at ejection.

On the 20-degree-tilt simulation, the model flew 800' downrange...
On the 10-degree-tilt simulation, the model flew 480' downrange...
On the 5-degree-tilt simulation, the model flew 214' downrange...

Sounds like you were between 5 and 10 degrees from vertical...

[CPMcGraw]

Looks like 8 degrees...

Here's what RockSim shows:


Long-Payload Cherokee Double-D - Simulation results

Engine selection
[D12-0] [C11-5]
Simulation control parameters
Flight resolution: 800.000000 samples/second
Descent resolution: 1.000000 samples/second
Method: Explicit Euler

Launch conditions
Altitude: 0.00000 Ft.
Relative humidity: 75.000 %
Temperature: 80.000 Deg. F
Pressure: 29.9139 In.
Wind speed model: Calm (0-2 MPH)
Low wind speed: 0.0000 MPH
High wind speed: 2.0000 MPH
Wind turbulence: Fairly constant speed (0.01)
Frequency: 0.010000 rad/second
Wind starts at altitude: 0.00000 Ft.
Launch guide angle: 0.140 Degrees from vertical (RockSim came up with this number based on my input of 8 degrees)
Latitude: 31.000 Degrees

Launch guide data:
Launch guide length: 48.0000 In.
Velocity at launch guide departure: 46.8769 ft/s
The launch guide was cleared at : 0.307 Seconds
User specified minimum velocity for stable flight: 43.9993 ft/s
Minimum velocity for stable flight reached at: 43.8339 In.

Max data values:
Maximum acceleration:Vertical (y): 344.773 Ft./s/sHorizontal (x): 75.067 Ft./s/sMagnitude: 360.050 Ft./s/s
Maximum velocity:Vertical (y): 262.5643 ft/sHorizontal (x): 61.5565 ft/sMagnitude: 269.6709 ft/s
Maximum range from launch site: 356.43826 Ft.
Maximum altitude: 1028.80608 Ft.

Engine ejection charge data:
Using a delay time of : 5.000 Seconds
Velocity: 59.5263 ft/s
Altitude: 1021.48746 Ft.

Recovery system data
P: Parachute Deployed at : 7.462 Seconds
Velocity at deployment: 59.5263 ft/s <<<----- This is the killer figure. Instant shread...
Altitude at deployment: 1021.48746 Ft. <<<----- You should have pegged 1000', if only by a little margin!
Range at deployment: 314.46184 Ft. <<<----- Matches your estimate...

Time data
Time to burnout: 2.463 Sec.
Time to apogee: 8.005 Sec.
Optimal ejection delay: 5.542 Sec.

Landing data
Successful landing
Time to landing: 64.756 Sec.
Range at landing: 356.43826
Velocity at landing: Vertical: -18.1257 ft/s , Horizontal: 0.8891 ft/s , Magnitude: 18.1475 ft/s

Competition settings
Competition conditions are not in use for this simulation.


A lot of data to wallow through...

Some of these parameters might need adjusting based on your location, like wind speed and temperature (and humidity), but I don't think you'll see a tremendous change from what I got here.

[Eagle3]

Yep, no weight on the payload and it's 7.5" long. Payload weight is phase two next month unless I get a good day to fly it from the field next to my house.