I wanna build something that goes up on more than one engine, something ive never done before.....i was going to build something that uses the little A10 motors as someone else did a thread on, and it was really cool....BUT.....i found a BT-80 body tube and a balsa nose cone for a length of about 22" maybe a little more if i make stand up fins, SOOOoooo, i wanted to know....
1)Should i use 3 18mm motors, 2 D12 motors, or 3 D12 motors?
2) Will 2 D12 motors even work?
3)Am i being foolish for even attempting this project?
4) ANYONE with cluster experience, PLEASE feel free to chime in with ANY advice.....im all eyes- n- ears....ive built alot of rockets, but no cluster stuff what so ever!!
Many Thanks! Bill

Hi Bill!
I know you have that BT-80 and nose cone but here's something else to think about.
You might want to cluster 18mm engines first, then build up to 24mm.

Buy a Baby Bertha with a 40% coupon at Hobby Lobby, maybe $6.50.
Cut the Baby Bertha tube down to 7" long.
Add a 11" length of BT-60 tube, a coupler, two more BT-20 tubes and you've got a three engine cluster Ranger!
It's the cheapest 3 engine cluster bash out there.

Granted the Baby Bertha fins are slightly different than the Ranger fins but nobody will know or care!
Flys great with three A8-3s, B6-4s or C6-5 or 7s.

Here's the blog posts:
http://modelrocketbuilding.blogspot...?max-results=20

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Hans "Chris" Michielssen
Old/New NAR # 19086 SR

www.oddlrockets.com
www.modelrocketbuilding.blogspot.com
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Your results may vary
"Nose cones roll, be careful with that."
Every spaceman needs a ray gun.
Look out - I'm the Meister Shyster!

We love clustering! Clustering AND staging, is even better!

Clustering is a natural progression in this hobby and it's not all that difficult but there are a number of factors to account for while learning; like an upgraded launch system. When you build your cluster you may need to go up in lug size or use rail buttons and of course, a larger diameter rod or a rail. More igniters equals a need for more power from the launch system so you need a heavier pad and controller and lead acid battery or gel pack.

If you modify a kit you'll have to account for changes in cp/cg relationship, maybe some nose weight, depending on the rocket. Just a few items here, but it's worth the effort and lots of fun.

Many people here are experienced at clustering. Our stuff is here: www.vernarockets.com. Just scroll the pages in the menu and follow the links for build threads, photos, etc. I'm sure you'll have more responses shortly.

Just remember, almost anything can be clustered!

Good luck!

Randy
www.vernarockets.com
http://www.amazon.com/dp/B00HHJHOK6
https://www.facebook.com/RocketBabeDustStorm

The ABSOLUTE #1 thing to remember when clustering is to wire the igniters in PARALLEL, NOT in series !
If you dont understand what that entails, refer to the Estes Technical report on Clustering.
Wiring in Series virtually guarantees only one motor igniting, causing off-center thrust and a crash.

You will need a launch controller a lot more powerful than a 'throwaway' AA cell electron beam. the old Estes Astron controller hooked to a 12V car or motorcycle battery works great. I use a 8Ah gel-cell with mine usually. It only measures 3"x6"x5".

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !

All you need to get started in clustering is:

Quest Q2G2 igniters
(Sunward) clip whip

I use my regular Estes 6V launcher and launch pad. I hold the button down and insert the safety key to launch. Very reliable.

Sure a 12v system is the way to go but this works well too.

http://v-serv.com/usr/instaship-visual.htm

http://v-serv.com/usr/kits/fwithmultipledpods.htm

http://v-serv.com/usr/kits/weightlofter.htm

The Baby Bertha is a good idea. You don't actually need to modify anything except the motor mount. Three 18mm motors in a triangle fit just right. Read the Handbook chapter 9, or Model Rocket Design and Construction chapter 10.

__________________
Clear skies and fair winds,
Mike

NAR 31689

Hi Bill;

With a BT-80 you certainly have some clustering flexibility. An airframe that size will comfortably host up to four 24 mm motors or up to seven 18 mm motors. The following formula can be used to quickly calculate the maximum number of engines that will fit inside a given airframe:

n = INT{180/arcsin[M/(AF-M)]} where

AF is the inside diameter of the airframe
M is the outside diameter of the motor mount tubes (assumes all the motors are of the same diameter)
INT is the integer function (whole numbers only, so any decimal fraction is dropped)

Good Luck, and let us see the final creation!

__________________
John
YORF #003
SAM #004

I like the faux Ranger idea. But I'd recommend using your BT 80 and get a twin 18mm mount from Uncle Mike's. Two 18s are just fine for the size rocket you suggest, being about the same size as a twin 18mm powered Centuri Saturn 1B.

If you're learning, why not do it cheaply? Two 18s are a lot cheaper than two 24s.

And if you really want to go nuts on the inexpensive learning rocket, give it enough room under the rear bulkhead for a staging coupler. Once you master clustering, you could move to Steely-Eyed Missileman status with clustered staging like a D12-0 to twin B6-6 or twin 18 booster to twin 18 sustainer.

But I digress . . . .

__________________
NAR 79743
NARTrek Silver
I miss being SAM 062

Awaiting First Launch: Too numerous to count
Finishing: Zooch Saturn V; Alway/Nau BioArcas; Estes Expedition; TLP Standard
Repair/Rescue: Cherokee-D (2); Centuri Nike-Smoke; MX-774
On the Bench: 2650;
Dream Stage: 1/39.37 R-7

Once n >= 6, you have room in the middle for another motor of the same size.

With a BT-80, you can have a 24mm motor surrounded by a ring of 7 18mms.

It is important that you seal around the motor tubes so that the ejection charge cannot escape.

While prepping, stuff a small ball of wadding into the front of each motor so that a misfired one will not be tempted to light from the wrong end when the others eject.


Bill

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