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Hell Boy > 19 motor cluster

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delta22

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Always wanted to build an upscale Fat Boy, and Polecat's 5.5" Fat Man is a good kit to do it with.

The kit comes with a fiberglass nose cone, pre-glassed body tube (looks like LOC 5.5"), bevelled fins, 2 CRs, 54mm engine tube, plus some other hardware and instructions. Flier supplies chute. A good deal at $99.

The very wide body is ideal for clusters, 24mm motors are economical and 19x of these fit well in a 5.5" airframe, so that is what I am going to do.

Robert DeHate built a nice 10" Polecat Fat Man, which had a slide out motor mount. Had a nice flight at CMASS and then went up on a P motor at LDRS which CATO'ed and took the rocket with it.

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sylvie369

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After a moment of "Does this guy know what he's doing?", I looked at your avatar, and remembered ("yes, he does").

I am starting to wonder if you're aware that you can fly a rocket using only one or two motors, though. ;)
 

delta22

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Decided to go with a solid bulkhead 6" from the bottom of the airframe to separate the engine compartment from deployment area (first picture on right). For deployment plan to use altimeter and rig for possible dual deploy.

Started by weighting the NC with 8oz of lead, with a 54mm tube to slide in more weight as needed. First picture on left is the bulkhead that attaches to the 4 Tnuts on NC.

Judging by the smell as I sanded the NC it seems to have been build with polyester resin.

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DAllen

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I cannot wait to see how you do the motor mount.

*DAllen subscribes to thread*

:pop:
 

UPscaler

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I'll subscribe too, I can't wait to see this!
 
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judo

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Smoooooke!
Lot's of smoke!
 

Rocketeer Gator

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Reloads or Estes??? I just did the math for Estes D12's (At Hobby Lobby bought a 3pack @ 30% off $9.10) 19/3=6.33 6.33x9.10=57.607
Holy crap $58 per launch....hope they all ignite!! :jaw:

also subscribes :pop:
 

HotRod Rockets

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Excellent Name.

what no -In-ate-or? you can always nick name it.... Smoke-in-ate-or..

What's the ETA on this one Fall '10 or Spring '11 ? I don't want to miss this one.

------
Rocket -E-Gator
I just did the math for Estes D12's (At Hobby Lobby bought a 3pack @ 30% off $9.10) 19/3=6.33 6.33x9.10=57.607
You can't measure it in dollars and cents. Or in Newtons of Thrust.

You have to measure it in Gigawatts!

.
 

gdiscenza

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1.21 Gigawatts?? This thing'll recover in 1985!!!

G.D.
 

powderburner

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delta22,

Was there any particular reason to arrange the outer dozen MMTs near the circumference, instead of "honeycomb" dense-packing them together with the center seven?
 

rstaff3

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I don't know how he actually plans it but the chances are this is just what popped out of RockSim and, for that, was close enough.
 

delta22

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delta22,

Was there any particular reason to arrange the outer dozen MMTs near the circumference, instead of "honeycomb" dense-packing them together with the center seven?
I don't know how he actually plans it but the chances are this is just what popped out of RockSim and, for that, was close enough.
Exactly correct.

To model this complex a cluster mount in RockSim I had to add:
1) one central motor
2) a ring of 6 around that
3) a ring of 12 around that one

Interlocking of motor tubes is not depicted accurately in the model.

It is a "honeycomb" in the real thing, for simplicity of build, motor density and strength.
 

delta22

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Reloads or Estes??? I just did the math for Estes D12's (At Hobby Lobby bought a 3pack @ 30% off $9.10) 19/3=6.33 6.33x9.10=57.607
Holy crap $58 per launch....hope they all ignite!! :jaw:

also subscribes :pop:
Yes, launches won't be cheap.

However, big clusters are typically about the price of a single motor with twice the impulse.

As David noted above, it's really more about effect than altitude in a project like this.
 

DAllen

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D12 = 16.8 newtons

16.8 x 19 = 319.2 newtons

One H268 = 320 newtons or roughly $30

Yeah, it's about effect. I love big honking clusters like that.

-Dave
 

delta22

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Used a jig from BMI to align fins.

For this mod I glued a 6" coupler tube at the bottom of the body tube. Trimmed the tabs on the TTW fins. Then epoxied them into the slots in the body tube, butting them up against the coupler tube.

Generous fillets with thick, fast Locktite 5 minute epoxy.

Then glassed very lightly using thin 1.3oz FG layers. Three layers where fins join body, one layer everywhere else. West 206 epoxy.

Just enough to help anchor the fins and provide a hard, smooth surface to the exterior.

After plenty of sanding, applied a topcoat of epoxy and then sanded that down.

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delta22

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Cut LOC 24mm tubing into 18 pieces 5.5" long and one 6" long for the center. The 6" tube in the center will contact the solid bulkhead, other tubes were shorter to avoid interference with the bottom parts of recovery hardware.

Glued into a honeycomb using yellow, quick-tacking Elmers.

Originally, I was planning to mount this into a stiffy tube until I weighed it, 8oz!

Cut strips from a stiffy at 6 contact points. These 6 strips plus the top of the center motor tube hold the motor mounts into the rocket.

Painted West 206 epoxy on the outside of the motor honeycomb and inside of the space they mount into, to bond and fire-harden.

Rocket body (no NC) went from 2.0lbs to 2.5lbs with addition of motor tubes.

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delta22

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rstaff3

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Boris, with all those plugged tubes, what are your plans for the D12's? Or are you actually thinking about D11's? On my 10 D cluster, I plugged D12-0s for 9 of them and then used the other for ejection. I ran into a hobby shop which found a huge box of D12-0s and they were dumping them for $3.50!
 

delta22

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Boris, with all those plugged tubes, what are your plans for the D12's? Or are you actually thinking about D11's? On my 10 D cluster, I plugged D12-0s for 9 of them and then used the other for ejection. I ran into a hobby shop which found a huge box of D12-0s and they were dumping them for $3.50!
Only the center tube is plugged (against the bulkhead).

The 18 surrounding tubes have a 1/2" gap from the bulkhead and could vent their ejections through the open spaces surrounding the motor honeycomb.

That said, I will use D11-P motors to avoid scorching.

For some flights will put one ProX 24mm F30 White in the middle. The effect of the white AP flame surrounded by BP jets is very cool.

pic 1: A motherload of D11-Ps (150 motors) I picked up from Hangar 11 recently when Estes told me they had done a production run.

pic 2: Upscale (2x) FlisKits Thunderbird going up on a central F30 and 10x Estes D motors. Also planning to repeat this flight on 11/6.

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rstaff3

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Here's the only launch shot I have of my Massive Gassive.

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troj

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How do you ignite all of these? Test igniters, and build a serious clip whip? Or do you do something else?

-Kevin
 

rstaff3

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I personally cheat....quickmatch all the way for bug BP clusters. Lit with an Estes igniter.
 

delta22

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How do you ignite all of these? Test igniters, and build a serious clip whip? Or do you do something else?

-Kevin
I have used Rocketflite MF ematches and ML igniters with very good results. For bigger clusters I have started using a cluster box to supply lots of current.

I never use a whip clip, as they create many points of electrical failure. The Rocketflite products, and some of the others, have long insulated leads, allowing them to be directly joined.

A number of threads I started have pictures of the igniters and cluster box in action.
 

delta22

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I personally cheat....quickmatch all the way for bug BP clusters. Lit with an Estes igniter.
I've only done a few experiments with quickmatch, with mixed results.

How do you set yours up?
What have your results been?
 

rstaff3

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I have had good luck with the quickmatch. The 10-motor Massive Gassive is my biggest 24mm cluster and my 12-Pack is my biggest 18mm (check out the video link in the EMRR review). I can only remember one failure...on a 2-motor Deuce :y:

Here's my set up. I insert two ~6" strands of quickmatch (it comes packaged with 5 pieces sheathed in an outer covering) in the nozzle of 24mm motors and one strand in 18mm. The extra strand in the 24mm motors is overkill but I have a lot of it. I'll probably eventually regret not conserving :eek:. I use another short piece to wedge the long strand(s) in. I then use masking tape to hold the match in place. After the motors are installed, the strands are pulled together and taped about one inch from the bottom. An igniter is then slid into the bundle. Earlier, I said I used an Estes igniter but actually usually use something else since the short leads don't work well with big clips on HPR pads.

I think the one failure was because only one strand lit on the pad. On small clusters, I now stick some extra in the tape bundle to make sure there is a nice fireball to get all of the strands lit.

Like I said, this is kinda like cheating (and of course, will only work on BP motors). I've also used a central composite, which ignited the quickmatch for the outboards.
 

delta22

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Thanks for the info Dick and CJL.

Painted the inside of the recovery area with thinned epoxy for fire resistance (West 206 + 25% alcohol by weight). The 38mm internal tube is for the altimeter and the 3" internal tube is for the main.

Started to build the altimeter sled. Alt vent hole can be seen mid-body. It directly enters internal 38mm tube.

Added 7x threaded rods for retention, 3" long 8-32, with 3/4" exposed. Also painted the inside of the motor tubes with thinned epoxy for physical and fire hardening.

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