Not much of a challenge, actually. I've mentioned before that I am a 4-H project leader, and also that my budget doesn't allow for RockSim. Now, I'm happy enough on my own designing and testing rockets the "old fashioned" way; but for the kids, I like tested if not proven designs.

So here's the deal. I have a mess of A10-3T engines, courtesy of Wal-Mart. I'd like an optimal (3,4)FNC rocket design, using only parts available from Semroc. By "optimal" I mean (a) stable and (b) around 10 FPS at deployment (or less if possible). Altitude is not important; small field fliers are fine. Designs able to use Semroc laser cut fins would be a big plus, since these rockets will be built by kids (and hopefully, being posted here, not just by my students).

If I had RockSim, I'd crank it out and be done. But I don't. Anyone want to take it on?


Extra Credit: 2x and 3x cluster rockets designed for A10-3T engines, same criteria as above. Would be good for the more "advanced" students (2nd year and above). Of course, the centering rings would have to be handmade, but I did say "advanced" didn't I?

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NAR # 115523
Once upon a better day... SAM #0076
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Take a look at freeware like wRASP. I've been living off the Palm version for several years now.

But for some crazy reason, I'd say that an A10-3 in an adapter would be perfect in a Baby Bertha.



Well, if you want LOTS of extra credit, one of our section members built a rocket called the D80, a cluster of EIGHT A10-3T in a BT-70 body tube with the old balsa BNC70 nose cone. It's a pretty cool flier, and I keep thinking about building one myself.

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I fought the law, and the law LOST!

I'm intrigued by this one myself. Do you have an electronic version of the plans, or a link if they exist online?

It'd be a good complement to my Viva Italian (7 C's).

Thanks,

John B.

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John Buscaglia
NAR 27366
SAM 63
CMASS Member

Solo,

Here are three very basic, easily-buildable single-engine designs that meet your criteria. They are all ST-10 size models, which means they should have a nice "feel" in their hands. Not too small, like a BT-20 or ST-7 design, and not too large, like a BT-55 or ST-13 design. All of these use a standard 36" x 1/8" rod for launch.

The fin pattern is slightly modified from what RockSim offered. They are larger, and they are 1/8" thick balsa. That should also be a plus for small fingers, in that it has a bit more ruggedness when being handled.


XFNC Challenge #1:

Length: 21.10"
Diameter: 1.04" (ST-10)
Fin Span: 6.04"
Weight: 1.04 oz

A10-3T.....292'......Dv 8 FPS......Deploys on the way UP



XFNC Challenge #2:

Length: 31.10"
Weight: 1.42 oz

A10-3T......205'......Dv 8 FPS......Deploys on the way DOWN



XFNC Challenge #3:

Length: 29.10"
Weight: 1.36 oz

A10-3T......217'......Dv 5 FPS......Deploys AT APOGEE

Attached Thumbnails

           

Attached Files

	XFNC Challenge #1.rkt (112.3 KB, 130 views)
	XFNC Challenge #2.rkt (115.6 KB, 126 views)
	XFNC Challenge #3.rkt (115.6 KB, 123 views)

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Craig McGraw

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SAM 0044
AMA 352635

Solo, here's a two-engine cluster for your "advanced" group. I increased the diameter to ST-13, and used four fins of 1/8" balsa instead of three. The model takes a 16" parachute to recover at about 12 FPS on landing.

Length: 40.40"
Diameter: 1.34" (ST-13)
Fin Span: 6.84"
Weight: 2.50 oz

Launch rod: 36" x 1/8"

(2) A10-3T......256'......Dv 5 FPS

Hope these designs fit your needs!

Attached Thumbnails

   

Attached Files

XFNC Challenge #4.rkt (123.8 KB, 96 views)

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Craig McGraw

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BARCLONE Forum -- BARCLONE Forum

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SAM 0044
AMA 352635

Excellent, Craig, thanks! Can I ask a favor? A parts list would be nice. I can probably guess my way through it, but it would be much quicker with a list.

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NAR # 115523
Once upon a better day... SAM #0076
My site: http://rocketry.gonnerman.org

Mini Hydra?

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-Fred Shecter NAR 20117 (L2)
Southern California Rocket Association, NAR Section 430

What a cool idea! Do you think the 3 sec delay would be long enough for a 7 engine cluster launch?

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"AND I hope they are from the planet of the "Chunk spunky Mary-Lou Retton clones". - Ironnerd

"Those who trade liberty for security have neither" - Benjamin Franklin

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www.paulsavia.com

www.soundclick.com/paulsavia

Here's the basic #1:

BC-1031 Elliptical NC
ST-10180 Main Body
(2) CR-510 Rings
ST-530 Engine Tube
TB-5 or TR-5 Thrust Block
EH-1 Mini Hook
SE-10 Screw Eye
SCE-24 Elastic Chord
SCK-24 Kevlar Thread
CPK-12 12" Parachute
LL-122 2" Launch Lug, 1/8" x 2.25"
1/8" Balsa Sheet


For both #2 and #3, add:

HTC-10 Coupler


For only #2, add:

ST-10100 Body Tube


For only #3, add:

ST-1080 Body Tube



I didn't use a stuffer tube on #2 or #3, as the ST-10 is small enough that I don't think it would be necessary.


For the #4:

BC-1344 Ogive NC
(2) ST-13180 Body Tubes
HTC-13 Coupler
(2) ST-5150 Engine Tubes
(2) TB-5 or TR-5 Thrust Blocks
(2) EH-2 Standard-length Hooks
(3) Custom CR-513 Rings for 2-engine clusters
(2) LL-110 1" x 1/8" Launch Lugs
CPK-16 16" Parachute
SCE-24 Elastic Chord
SCK-24 Kevlar Thread
1/8" Balsa Sheet

This is a deviation from the given design, by using two 15" lengths of ST-5 instead of the short 3" lengths shown in the original design. Add one extra centering ring at the very top of the stuffers for internal support and to close off the volume around the tubes. Use the standard hooks instead of the mini hooks, as the second ring is used to "clamp down" on the hook. Use a touch of epoxy (or JB Weld) to hold the hooks down, and you shouldn't have them come loose.

The changes this makes to the design increase the mass to 2.79 oz, drops the altitude to 226', but more importantly, drops the Dv to a mere 2 FPS over the top. All of the simulation runs for this Mk II version show the parachute symbols with no arrows in any run. See the attached files.

Attached Thumbnails

 

Attached Files

XFNC Challenge #4 Mk II.rkt (125.8 KB, 103 views)

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Craig McGraw

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SAM 0044
AMA 352635

Hey, I like that cluster! Very cool. Thanks for the parts lists, also.

__________________
NAR # 115523
Once upon a better day... SAM #0076
My site: http://rocketry.gonnerman.org