Cluster Choice?

The lady who does all the early work with my race horses has given me permission to launch from her new 50 acre property. Hardly any trees!!!! Horses in the top paddocks but........

She knows 100's of other people in the industry (Most have large, good launching properties) and all their kids are in the pony clubs....

I'd like to put on a good show for her kids & the neighbours kids...and maybe get them all interested in rocketry.

I'm sure they'd flip over a cluster!

Reply to
CJC
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DONE!!!

Reply to
CJC

My choice would definitely be the 24+6 cluster! Way more flight options, which means more variety and less boredom. Plus it's handy if you can't afford to fly it fully loaded everytime, or if certain motors become hard to get for some reason.

@
Reply to
raydunakin

Got another one I mean.....not a 2stg Fats!

Reply to
CJC

And we're easy, too!

: P

Al (Sorry, couldn't resist...)

Reply to
Alan Tuskes

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.

Reply to
Gary

So will the horses :-(

NEVER launch around horses, especially horses being ridden. It will spook the horses, and could injur the riders. Even if they are fenced in.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

Reply to
Bob Kaplow

Clusters rule! ; )

Randy

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Reply to
<randyolb

Heh heh heh...... Yeah I learned all about launching with animals.

My first launch as a Youngish BAR.......Lemonator on a C6-5 in the front yard. Horse paddock begins about 30m away. Being as smart as horses are they were milling about watching what I was doing. Something new going on here they thought.

3,2,1 launch........I spent the next few seconds worrying & watching the horses disappear down the other end of the paddock....If they could only run that fast in the race! Wasn't concerned were the rocket went.....

Since that experience (Scarred Me) I do the following...-

.. Never launch within 100m of flighty animals (My dogs luv it) .. .. Give a few loud claps & whistles to let them know what's about to happen. .. (Since I've been doing this it has helped a great deal) .. .. And I would NEVER launch when a person's on top..

Reply to
CJC

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

John

Reply to
John Stein

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

Reply to
The Rocket Scientist

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!

Reply to
Bob Kaplow

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

Reply to
Gary

snip

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

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Reply to
<randyolb

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.

Reply to
Gary

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.

Reply to
CJC

snip

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

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Reply to
<randyolb

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. :)

Reply to
Gary

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!

Reply to
Bob Kaplow

Right...do it like that, and G. Harry Stine'll be rolling over in his grave

Reply to
Dodo

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