Cluster Duck Build

[tomsteve]

There is not a whole lot of room. The body tube comes down over the motor tubes quite a ways and covers the end of the engine blocks, so the vents need to be above the bottom of the BT. So, the only place to vent is on to the fins. It is why I painted all the fins black, I already figured they were going to have to deal with a lot of exhaust gases.

Couple pics to illustrate what I mean. The blue tape marks the top of the engine block inside the motor tube. The vent hole needs to be above that. As you can see, when the body tube is installed, it comes down to the tape line, so any vent hole that takes advantage of the space between the fins will have to vent the gases onto the fins.

Open to suggestions if I am missing something.

if you have access to the engine block you can drill through that. remember- the top of the motorbis below the engine block

 

[StanO]

Boris wrote his Cluster Box instructions quite a few years ago. I've gone back and found what I used to build mine, in case anyone is interested.

I found my Amazon order from Spring 2018 that looks like it was the Crown Vic solenoid and the 12v relay that I used:

Standard Motor Products SS598 Solenoid
E Support Car Relay 12v 40a Spst 4pin Socket Pack of 5

I really think any 1990 Crown Vic solenoid would work (probably along with many others). As Boris explains, the key is that the solenoid have a clamping diode so you don't damage the launch controller. I bought a five pack of relays on the assumption that they wouldn't last long with all that current, but I'm still on my first one.

The battery I use is from Hobby King, it looks like it has been discontinued, but I'm sure you can find something comparable:

Turnigy Bolt V2 1300mAh 4S 65~130C High Voltage Lipo Pack

The only other major components are a 300 Amp two position rotary switch to turn the whole thing on and off, a digital volt meter I had kicking around to monitor the battery voltage, and some very heavy gauge cables (2 gauge maybe?) to get from the LiPo battery to your rocket. The circuit from the launch controller to the 12v relay can be MUCH lighter weight. There are plenty of online calculators to help you figure out wire diameters for voltage/current/length.

I put the light weight clips that go to the launch controller on banana plugs to make it more easy to store/replace them and mounted everything in a cigar box:

View attachment 430610

I requested the copies of the issues from NAR that have the instructions for the Cluster Box a couple of weeks ago and haven't heard from them or received anything. Slow mail or whatever. If you don't mind could I get a copy from you? You can PM me.

Thanks, Stan

 

[mtnmanak]

I requested the copies of the issues from NAR that have the instructions for the Cluster Box a couple of weeks ago and haven't heard from them or received anything. Slow mail or whatever. If you don't mind could I get a copy from you? You can PM me.

Thanks, Stan

Do you need a print copy of the whole issue? You can always login to the NAR site, go to the Sport Rocketry Magazine Archive under "Member Resources" and then go to the JANUARY/FEBRUARY 2012 VOLUME 54, NUMBER 1 issue. You can either download the whole issue or print out the article only. It begins on page 16.

Boris's Cluster Box page at https://bpasa.com/Cluster-box.htm has almost the same info as the Sport Rocketry article, except Boris's site has more detail about the testing.

 

[Dugway]

I built my Cluster Box entirely from the information on Boris's web page. You have to stare at a couple of the pictures to figure out the wiring, but if I can do it, anybody can. Does anyone know of a good tool for creating schematics? It would be a hassle to do it the first time, but going forward there would be much less confusion.

 

[mtnmanak]

I built my Cluster Box entirely from the information on Boris's web page. You have to stare at a couple of the pictures to figure out the wiring, but if I can do it, anybody can. Does anyone know of a good tool for creating schematics? It would be a hassle to do it the first time, but going forward there would be much less confusion.

I often use Visio for schematics, it is usually enough for the things I need to do.

This tool is free and I played around with it for a few minutes, looks pretty good: https://www.circuit-diagram.org/

 

[StanO]

I often use Visio for schematics, it is usually enough for the things I need to do.

This tool is free and I played around with it for a few minutes, looks pretty good: https://www.circuit-diagram.org/

Thanks Dugway & mtnmanak, I use VISIO extensively so shold be able to figure it out. Appreciate your help.

 

[mtnmanak]

I have all the parts and pieces for my cluster box, but haven't put it together yet.

Also, I did fly my Cluster Duck this weekend! Great launch - went up about 400 feet on 6 x B6-0's and 1 x D12-5. It was a great day with almost no wind and all 7 motors fired, the Duck flew straight and recovered only 10 feet from the pad. Great flight. Next time, I will push the limits on it a bit, but great first flight.

 

[Back_at_it]

Kinda jealous of you guys that flew the Duck this weekend. I had a great outing myself but I was trying to get everything that had not flown up in the air so I left some of my favorites including my Duck clone at home. I've never flown it on a cluster but it's still pretty impressive on single E12-4

 

[mtnmanak]

Love this Cluster Duck. It flew so well, I am going to up the ante with the motors next time, but I am also planning to build a bigger clone on a 4" airframe. I also have a few US Rockets clusters in the build pile to get to, so will hopefully have a number of large cluster rockets to fly this winter / next spring.

 

[mtnmanak]

Also, a couple notes on some of the discussions earlier in the thread:

I did drill the vent holes in the 18mm tubes, but I flew at a Tripoli launch last weekend that allows research motors, so all the 18mm motors were plugged with epoxy. Small amount of tape gave them a friction fit. All fired properly and had no issues with the ejection charges. All motors stayed in place. So, I didn't really test the vent holes this time around. Will check out their performance if I bring it to a NAR event or forget to bring plugged booster engines. It is nice to have zero residue in all those motor tubes at the end of the launch! For the heck of it, I may try a flight next time with the ends of the 18mm engines stuffed with dog barf and sealed with aluminum tape. Would like to know how that config works out.

I thought the parachute may be too big, but, since there was virtually zero wind, it was difficult to judge what the drift/descent rates would have been like on a windy day. For this launch, the 36" Dino chute was exactly perfect, so will stick with it for the time being

 

[Dissonance]

I'm building this model. (I'm going to paint it yellow and green, and put a University of Oregon duck sticker on it.)
The length along the fins and the 24mm tube is 3 7/8", but the 18mm tubes are 3 5/8". The picture in the instructions looks like they should be the same length. Please advise.

 

[mtnmanak]

The tubes should be longer. I would contact NCR and let them know. I imagine they would not have a problem sending you new motor tubes.

 

[Dissonance]

@mtnmanak Thank you for confirming what I suspected. I contacted NCR, and they said they were traveling and didn't seem understand the problem. I have some 18mm tubes, so I will just cut my own. It's not a big deal.

 

[mtnmanak]

@mtnmanak Thank you for confirming what I suspected. I contacted NCR, and they said they were traveling and didn't seem understand the problem. I have some 18mm tubes, so I will just cut my own. It's not a big deal.

Good interim option - I usually have plenty of 18mm tubes on hand, so cutting my own would also be my choice to continue the build. However, I would stick with it trying to get NCR to make it right. 18mm tubes aren't expensive, but they aren't free either!

The picture in post #11 of this thread gives a pretty good idea of how long the 18mm tubes should be.

 

[Dugway]

Just plug the ends of the zero delay outboard motors, and then there is no need for vent holes. Mount the motor tubes flush with the fin ends instead of against the bulkhead. The gap is hidden when the whole assembly is slid into the main body tube anyway.

 

[ECayemberg]

I'm building this model. (I'm going to paint it yellow and green, and put a University of Oregon duck sticker on it.)
The length along the fins and the 24mm tube is 3 7/8", but the 18mm tubes are 3 5/8". The picture in the instructions looks like they should be the same length. Please advise.
View attachment 508020

If you slide the 18mm mount tubes aft so their aft end is flush with the 24mm motor tube, the gap between the forward end of the 18mm tubes and the 2.6" to 24mm bulkhead is your vent. No need for additional vent holes, etc. Ejection gasses will go out the top and be diverted aft along the voids between the outboard motor tubes and inside of the main airframe.

 

[ECayemberg]

The tubes should be longer. I would contact NCR and let them know. I imagine they would not have a problem sending you new motor tubes.

Disagree, see my post about venting. You don't want those tubes to intersect/seal to the bulkhead (even for -0 engines).

 

[afadeev]

Disagree, see my post about venting. You don't want those tubes to intersect/seal to the bulkhead (even for -0 engines).

I agree with your suggestion, and having built on ClusterDuck (CD) myself recently, what you are recommending will work.
With one caveat - you don't want to allow the FWD end of the 18mm motor to sit flush with the bulkhead. You need to leave room for ejection charges to dissipate (unless you will epoxy seal the FWD ends of all 18mm motors). Otherwise, the ejection charge will have no place to go and will instead expel the spent motors back out towards the ground. Basically, it will be a low-powered Gutling gun ;-).

The confusion arises from the fact that NCR's own CD instructions call for abutting the 18mm tubes to both 24mm tube and the bulkhead, and cutting vent holes into 18mm tubes facing away from the 24mm motor tube. NCR produces detailed instructions with color illustrations, but sometimes does not update them as parts and designs evolve over time:
https://cdn.shopify.com/s/files/1/1...uctions_Master_010615.pdf?9826273292200455441
One area of the CD kit that I did not like was lack of positive motor retainment of any kind for the 18mm engines. There is just no room for it. I tape motors in place, but the exposed surface areas are barely enough to ensure secure attachment.

I forgot if the CD kit includes engine blocks for 18mm tubes or not (most of my recent NCR kits came with missing bits), but if they are included, you coudl use them without fully seating them inside the 18mm tube. Then drill vent holes into the exposed engine blocks surfaces. The sum length of the partially exposed engine block + supplied 18mm tube should be just about the right length.

Having said that, I think I did all of the above: cut my own 18mm tubes of proper length, glued engine blocks to the FWD ends of the tubes, and drilled vent holes into the outward facing area of the 18mm tube.

YMMV,
a

 

[mtnmanak]

I don't have the issues listed above because I always plug my 18mm motors in the Cluster Duck and use the 24mm motor for ejection. If you plan to let the 18mm motors have an ejection charge, then you will have to figure out a way to vent them. How you do that is your choice.

 

[Dissonance]

With the 1/4" space for venting, will the -0 engines still eject? If they don't, then it doesn't seem like they need to be -0 engines. If they do eject, then the rocket will be lighter and should go higher with it's momentum.