Cluster Choice?

CJC-
Fat Boys are cheap enough, so buy a few and build ALL OF THEM!!!
...working on a two-stage Fat Boy myself.

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I saw some 2 stage fat boy launches last week. They were fun. Clustered boost and single upper.
Jerry

DONE!!!
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Got another one I mean.....not a 2stg Fats!
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And we're easy, too!
: P
Al (Sorry, couldn't resist...)

Thanks guys! Ok....here's my current plans for some kits I picked up last week.......
I have just ordered some more 24 & 18mm tubes. LOTS :-) A few couplers, some nylon chutes, more Kevlar line & blankets, all in different sizes..........AND another FatBoy!!!
I thought I had enough tubing left but I've used up most of the left over supplies I have from a few yrs ago. Nice fresh stuff coming :-) I'll follow my usual course of action and ditch the balsa fins and card C-Rings. Replace with ply.
With the peice of 24mm tube I got left........that'll get cut in half & go in the Patriot & a Baby Bertha. I'll knock up an 18mm MMT adapter to use with them aswell.
I have to do both a 3x24 & a 24+6x18 FatBoy. They look so cool in RSim 3D with all dem motors! The 7 motor Fatboy will be the most clustered rocket I've ever done. Gotta keep advancing :-)
I got a free Phoenix kit from the hobby shop with the order... :-) Someone had stolen all the recovery gear & MMT out of it. Crazy man? Has the NC, 2 BT80's, Coupler, Decals, Fins & instructions.
I'll single layer glass it or fill it with couplers and put a 29mm MMT in. May do a 4x24 or 24+4x18 deal. The cluster bug has bitten......sorry...
The Canadian Arrow is getting a 29mm MMT.

CJC wrote:
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Geez, cluster mania around here. :)
Almost half my current fleet is clustered BP, the most being a 7x18 bird (typical BT-20 with 6 outboards). A pain to prep. My 5x18 B in-line cluster altitude model experienced some, er, heat transfer anomalies on its maiden flight. (It burned up from bad ejection gas ducting design.) An embarassing way to start NAR competition.
How's your launch controller? Seven (Solar) igniters will draw some serious juice. I had to build a new controller when the cluster bug bit me.
Hmmmm..... usually I like long, skinny rockets, but a long burn (3xE9) stubby has a weird appeal. I might have to try this.

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Clusters rule! ; )
Randy http://vernarockets.com /

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I guess I'll have to dust off the two-stage clustered Fat Boy again....hehehe!
John

snipped-for-privacy@charter.net wrote:
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Amen, brother!
One of my favorite rockets is something I call Cheap Thrills, a cluster of 4 13mm motors. Flies great on 4 A3-6T's.
I also like flying my LOC IV on 4 E9-8's.
Bill Sullivan
"Yield to temptation; it may not pass your way again." - Lazarus Long

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Except A3-6Ts are long out of production and no longer certified.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
This is a country which stands tallest in troubled times, a country that clings to fundamental principles, cherishes its constitutional heritage, and rejects simple solutions that compromise the values that lie at the roots of our democratic system. -- Supreme Court Justice Thurgood Marshall, 1972

CJC wrote:
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Got a Fat Boy from Hobby Town. This is a stubby little thing, all right.
Simmed a 3x24 version with stock dimensions and it wants about 200g nose weight for one caliber of stability with three E motors.
I have a "feel" for longer rockets, but this stubby mod does not give me a warm fuzzy; one caliber is a significant portion of the airframe and I am not experienced with short, fat rocket flight characteristics.
Does 200 gms nose weight and one caliber margin seem appropriate for this? Any particular stubby rocket flight characteristics to be aware of?
TIA

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I've never built or flown a Fat Boy but I have seen dozens of them fly, stock and modified. My observations are that they seem to fly well, mostly down range. Seldom have I seen one break 200' in altitude and they also seem to be particularly vulnerable to winds over 7-8 mph, the higher the wind, the lower the flight. I can't dismiss my concept of their flight characteristics because I've seen them built by 8-9 different people and about 35 flights. Best flight I've seen so far was about 300' up and 500 down range.
Randy http://vernarockets.com /

snipped-for-privacy@charter.net wrote:
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Thanks, Randy. By "downrange", do you mean in the direction of the wind? Or, into the wind? I am specifically concerned about responses to wind. The short moment arm of the stubby airframe would tend to lower rotational inertia as compared to a longer rocket and also reduce the moments of restoring lift. I can envision a long, arcing trajectory as you seem to be describing.
I think a high velocity launch would help, but the E-9's are not known for their velocity off short rods. Rocksim says I just hit 13 m/s off a 3' rod with E-9's and 200 gm nose weight. This will be a long rod launch, at least.
I'll put in a 8mph crosswind and see what the sims say.

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Actually I've seen them go both ways, into and with the wind. If I were building a clustered Fat Boy, I'd go with a 4' x 3/16ths rod to be on the safe side and fly with less than 7 mph wind.
Randy http://vernarockets.com /

With a heavier build (Ply Rings & Fins) and 250g NWt. on 3 E9-6 I sim about 1330ft. On an E9 + 6Cs tops out around 1270ft.
Am I that far off? Still need to tinker with design but my sims generally run at +/- 5% on altitude.
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CJC wrote: <about a Fat Boy cluster mod>
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That's in the ball park with my sims. Check your launch details and look at the velocity off the rod. I sim a standard 3' rod and barely make minimum velocity (13 m/s) with 200 gms extra mass. As Randy says, its better with a 4' rod. Even with only 1 caliber of stability, the Fat Boy seems to definitely weathercock.
Check out a 3 x E-15 Aerotech SU launch. :)

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1 cal is overkill on short stubby rockets like the Fat Boy. Find a stock FB, and load it with a C motor, and see where it balances. Put your bashed rockets CG at the same place.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
... One nation under surveillance, divisive, with liberty and justice for none.

On 13 Jun 2005 11:55:28 -0500, kaplow snipped-for-privacy@encompasserve.org.TRABoD (Bob Kaplow) wrote:
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Right...do it like that, and G. Harry Stine'll be rolling over in his grave

On Mon, 13 Jun 2005 13:20:20 -0400, snipped-for-privacy@aol.com wrote:
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Why? It'll work just fine. Or are you trying to suggest that, if the CG of a heavy rocket is in the same place as the CG of a lighter rocket with the same external dimensions, that the heavy rocket will not be exactly as stable as the light one? If so, I call BS.
- Rick "Who's Ray Bolger, and what's he got to do with it?" Dickinson