Sky Champ Lander 2 "Family"

[James Pierson]

Who would have ever thought that this design might fly on 18mm motors?? This
is my favotite version with the BTC-70 HZ which need just a little core sanding to
fit the Bt-55EE, 5.5" long, which is also a costom length BT. The balsa does add
the extra wieght forward that this design needed, and is easier to assemble and
finish. Test flight between the Balsa VS Paper will tell the story.
With this 2nd Version I have made a few improvements by adding an 1.5' Bt-70 to
the balsa transition to legthen the design for easier loading of the 12" Semroc
chute. The fins have also been adjusted for the same reason. Also, in the test
models I decided not to take the time to cut out the holes in the fins to save time.


My biggest question to you Rocksim experts is how to sim the drag on the Leg Landing
Pads. I just made them .75-.76 solid paper transitions with a thickness .05??
Should I have made them fins as it does not seem R9 is picking them up for drag?

Test Flights Pending, Mr. "Firey Underpants" has returned to rue the day! :D

Enjoy and Thanks Again, JP

James Pierson
NAR#77907

Sky Champ Lander 2 (18mm) Balsa Transition
Launch guide length: 36.0000 In

MOTOR.................MAX. ALTITUDE...........DEP. VELOCITY
A8-3..................148.83760 Ft.............17.3887 ft/s
B4-4..................341.67979 Ft.............17.0915 ft/s
B6-4..................345.59055 Ft.............13.4402 ft/s
C6-5..................712.05709 Ft.............24.4413 ft/s
.

[James Pierson]

This is the paper transition version of the Sky Champ Lander 2. It is basically the same build with the upper transition formed with paper instead of balsa. This is a cost effective way to improve this design.

Images same on pervious post.

Enjoy and Thanks Again, JP

James Pierson
NAR#77907

Sky Champ Lander 2 (18mm) Paper Transition
Launch guide length: 36.0000 In

MOTOR.................MAX. ALTITUDE...........DEP. VELOCITY
A8-3..................144.44718 Ft.............18.3496 ft/s
B4-4..................336.50919 Ft.............17.8185 ft/s
B6-4..................341.02362 Ft.............14.0557 ft/s
C6-5..................714.48819 Ft.............22.3126 ft/s
.

[James Pierson]

Since Carl came out with the beautiful BTC-60A why not try a 13mm version of the Sky Champ Lander?? So, here it be.

Enjoy and Thanks Again, JP

James Pierson
NAR#77907

Sky Champ Lander (13mm)
Launch guide length: 36.0000 In

MOTOR.................MAX. ALTITUDE...........DEP. VELOCITY
1/2A3T-2...............153.04199 Ft............20.0696 ft/s
A10T-3.................321.68668 Ft............1.0600 ft/s
A3T-4..................342.03740 Ft............23.5144 ft/s
.

[Pyro Pro]

I like it!

I wouldn't neccesarily trust RockSim's drag calculation for complex designs. When I tried to do a strap-on design with all the detail pieces added (lugs and fins to simulate the booster-holding mechanisms), it was calculating drag coefficients that kept the altitude to under 50 feet, for a 7-10 oz rocket, on ~50 Ns of power (manual Cd override of 0.8 made things jump into a reasonable range). There's no substitute for a few good flight tests to figure out the actual coefficient (unless you've got access to a CFD program and a supercomputer).

Then again, the leg arrangement isn't super-complicated, so someone ought to have some insight into simulating it (but not me).

[CPMcGraw]

James,

I don't know if you've tried this method before, but I changed the pads to body tubes, made them "paper", and gave them a 0.00" ID. I also added some impact braces...

Performance:


A8-3......145'......Dv 19 FPS
B4-4......331'......Dv 20 FPS
B6-4......334'......Dv 16 FPS
C6-5......689'......Dv 28 FPS......Not recommended


Going back to your original numbers, it looks like our simulation runs came out about even. Like Pyro said, I don't trust RockSim's drag calculations entirely. But I think they're close enough for this model.

[James Pierson]

Thanks David, that means alot.

James,
I don't know if you've tried this method before, but I changed the pads to body tubes, made them "paper", and gave them a 0.00" ID. I also added some impact braces...

On the original design the pads are the same using ST-7 CR knokout .05 fiber. Twice I broke a pad off because the paper delaminated and the Tightbond glue joint was fine. This time I drill a 1/8" hole with my x-acto knife for the dowel to fit into the knockout. Also painted the knockout with CA to help prevent the delamination. To watch this design decent was fairly easy decent. It's what it lander on, the nieghbor's fence, that caused the damage to the pads :o .


Going back to your original numbers, it looks like our simulation runs came out about even. Like Pyro said, I don't trust RockSim's drag calculations entirely. But I think they're close enough for this model.

The new Golden Rule: Nerver Trust Rocksim!

You are right guys that the test flight will tell the true story. :rolleyes:

Thanks for the input, JP.

James Pierson
NAR# 77907