One for the money, Two for the show

[beantownJPL]

I've been interested in the Apogee strap on boosters since I first came across them a while ago. I recently ordered a pair and decided to scratch-build the sustainer. It's just a 4FNC, but it's my 4FNC .

Overall length of 33.25" using BT-60 tubes, and a 24mm mount. The booster pods are BT-50 with 18mm mounts. Fin planform is clipped delta. Some "niceties" are an Apogee ejection baffle and Estes 24mm screw-on motor retention.

Middle photo is just a mockup - currently I've got the fins attached and filleted and it's ready for primer coat. I'll post more photos later. Planning to maiden this one at the "October Skies" joint launch between CMASS and RIMRA in Kingston, RI this Saturday. It may still be in primer by then ... we'll see how productive I can be.


EDIT: Maiden flight report here - https://www.rocketryforum.com/threads/one-for-the-money-two-for-the-show.155516/#post-1928917

 

[BABAR]

Hope you get three straight trails!
Go light on the main for your first flight

 

[beantownJPL]

Hope you get three straight trails!
Go light on the main for your first flight

Planning on a C11-5 in the sustainer and B6-0 in the boosters for the maiden.

Should put me at a comfortable 621' apogee with a well timed deploy according to rocksim.

 

[beantownJPL]

So the wife took the kids to her Mom's house this evening, leaving my evening free.

Except for a few details, this build is done.

 

[beantownJPL]

After paint, I measured the CG and found that it would only give me ~0.45 cal of stability with the CP calculated by Rocksim. I added about 8g of weight to the nose bringing the CG forward enough to give me between 2 and 2.5 cal stability depending upon engine selection. I also made a correction in the nose cone dimensions which brought the sim's weight and CG calculations in agreement with my measured values. (New rocksim file attached for anyone interested...)

I maidened the rocket yesterday at the "October Skies" joint launch between CMASS and RIMRA at RIMRA's field in West Kingston, RI. It was a gorgeous Autumn day with cloudless skies, temps in the high 50's to low 60's and generally light winds (sustained winds probably 5-8 mph, but sometimes almost dead calm. Occasional gusts in the 15-20 mph range - all based upon my finely calibrated "hair in the breeze" anemometer).

The first flight launched with C11-3 in the sustainer, and B6-0's in the pods (Rocksim estimate at ~538') . Good flight, straight as an arrow, however the port-side pod's shock cord got hung up on the pod's hook and came along for the rest of the ride dangling below the sustainer. The streamer got torched in the main's exhaust plume and some minor damage to the top of the body tube.

Main chute ejection was a little early. I was actually amazed at how well the sustainer continued on with its "trailer". I'm guessing the captive pod remained in a reasonably aerodynamic orientation.

Ok, lesson learned ... take real good care packing the shock cord ... I basically used a "slip knot chain" and got it all nicely settled below the streamers. The mylar streamer of the "captive pod" got torched in the exhaust plume of the main engine, and lost about 1/2 its length, and there was some minor zipper damage to the top of the pod's body tube. Easily repaired with some thin CA, a bit of "thumbnail burnishing" and a little sanding.

For the second flight (video below), I used a C11-3 in the main again, and stepped down to A8-0's in the boosters (Rocksim estimate at 386'). Again, the rocket left the launch pad with authority and flew straight as an arrow. The only "knock" against this flight is the pods ejected at different times (maybe 1/2-second apart?). There didn't appear to be any negative effect on the flight.



While the pod separations add a nice level of dynamics to the flight, I was a little disappointed on how early the separation event occurs. So, for the third and final flight on this bird for the day, I opted for a D12-4 in the main, and A8-3's in the pods (Rocksim estimate at ~813'). I wish I recorded this flight, as it was the best of the three. The pods stayed along for the ride until probably 500' or so and ejected cleanly, while the sustainer continued on with ejection shortly after apogee.

 

[BABAR]

Congrats! Impressive to get three straight three motor cluster ignitions.
What did you use for igniters?

 

[beantownJPL]

Congrats! Impressive to get three straight three motor cluster ignitions.
What did you use for igniters?

Thanks! It turned out to be quite a crowd pleaser ... lots of folks coming to my table to ask about it after each flight.

Ignition provided by Estes "solar" igniters and a home-made clip whip.

 

[Bat-mite]

Definitely a unique challenge, sort of clustered, sort of staged. Nice patriotic look! Thanks for the video.

 

[beantownJPL]

Definitely a unique challenge, sort of clustered, sort of staged. Nice patriotic look! Thanks for the video.

Agreed ... this is my first cluster too. I can't be more pleased with the result. This has quickly become one of my favorite rockets in my fleet. I also enjoyed raiding my old RC supplies (which have been gathering dust for near a decade on a shelf in the cellar) for wire, shrink wrap tubing and 'gator clips to create the clip whip for the cluster.

The paint job was completely inspired by the colors RockSim chose for the components ... and the fact that the nose cones provided with the Apogee boosters were already red, and the BT's were already white ... so I didn't even have paint the boosters! A happy accident that resulted in a pretty smart-looking rocket on the pad.

I just ordered some inkjet waterslide decal stock, so I'm going to spruce it up a bit with some decals (and my somewhat suspect graphic design skills). It doesn't really show in the photos, but the red on the sustainer's nose cone, and the blue on the aft section of the airframe is actually metal flake (oooh, sparkly!). So, I'll paint the pod nosecones to match, as well as fill and paint the BTs and shoot the whole thing with a coat of clear.

 

[BABAR]

Make sure everything is dry with no paint odor before you throw clear on anyting

 

[beantownJPL]

Make sure everything is dry with no paint odor before you throw clear on anyting

Yeah ... I've learned my lesson with clear enamel the hard way ... too many times.

I'm saving up for an airbrush compressor so I can switch over to acrylics and greater control and the ability to work indoors without sending myself on a trip to the moon . I've played around with the cheap Testors single-stage external mix airbrush with the canned gas. I don't like the canned gas much (expensive, doesn't last, loses pressure as the can cools, etc..), but have liked my "experimental" results so far.

That'll be a new learning curve to be sure, but rattle cans don't offer much control of spray pattern and paint flow which is a challenge for more detailed paint jobs on smaller models. Then there's all the chemistry...

 

[BDB]

I saw all three flights on Saturday. They were definitely impressive. Congrats!

 

[beantownJPL]

I saw all three flights on Saturday. They were definitely impressive. Congrats!

Thanks for hosting us! It was a lot of nice, relaxed flying and a friendly group.

 

[Mugs914]

That is awesome, Bean! Congratulations! This thread has been pretty inspirational. I'm going to have to try a parallel stager now!

As for an airbrush compressor, they sell a pretty decent one at Harbor freight, if you have one of those near you. As I recall, they sell the compressor as a stand-alone with a pressure regulator installed, or a set with the compressor and an airbrush, but no regulator. Get the one with the pressure regulator on it, you really will need that adjustment. It sells for something like $75 - $80 if memory serves, and is actually a pretty nice. They also have a good internal mix airbrush for about $19. Can't beat that deal!

Thanks again for sharing your project! Well done!

 

[beantownJPL]

That is awesome, Bean! Congratulations! This thread has been pretty inspirational. I'm going to have to try a parallel stager now!

As for an airbrush compressor, they sell a pretty decent one at Harbor freight, if you have one of those near you. As I recall, they sell the compressor as a stand-alone with a pressure regulator installed, or a set with the compressor and an airbrush, but no regulator. Get the one with the pressure regulator on it, you really will need that adjustment. It sells for something like $75 - $80 if memory serves, and is actually a pretty nice. They also have a good internal mix airbrush for about $19. Can't beat that deal!

Thanks again for sharing your project! Well done!

I'd definitely recommend it ... fun rocket.

We do have a HF nearby, I'll have to take a look at their airbrush stuff. Kida bananas that they don't include the regulator in the kit, but do in the standalone. Odd...