Friday, January 28, 2011

Review: Three Estes MODifications

This post includes:
  • Big Dipper Daddy
  • Fat Boy 7x18mm Motor Eater
  • Phinagain Cruise Missile


Big Dipper Daddy

I bought this Big Daddy (on sale, of course) as a test-bed for a Micro-Hybrid motor. This required an extension of the motor mount, and the capability to house electronics in the nose cone. Before flying it on a Micro-Hybrid, I'll probably try it on a conventional motor with motor ejection (1st flight) and with electronics (2nd flight).

Construction:
Since there are already several articles on the Big Daddy, I will describe only the modifications that I made. Because the Micro-Hybrid is just over 6 inches long, and I wanted the full motor enclosed by the motor tube to protect it from ejection gasses, the 24mm motor mount tube is 7" long. I used the stock cardboard centering rings and made small notches in them to allow a Kevlar® shock cord to extend to the rear of the rocket. I also added a single T-Nut for positive motor retention. This is mounted on the inside of the rear centering ring to make sure it doesn't pull out (the ring is fairly thin cardboard, after all). The retention bracket itself is a metal picture frame hanger.

To allow the mounting of electronics in the nose cone and to provide more room for the recovery components, I cut the off the nose cone shoulder in front of the stock parachute hook. When looking for a method of attaching the recovery system and electronics in the modified nose cone, I borrowed a tip from The Rocketry Forum (TRF). I sanded a spare 38mm-to-3" centering ring so that it fits in the nose cone just ahead of the shoulder. It rests against the shoulder, which provides a mechanical lock. I added a loop of tubular Kevlar® for chute attachment, and glued the ring in with Liquid Nails. I used this concept on my Standard Cray-ARM , but never had thought of it for a standard nose cone (vs. the tip of my Crayon rocket). My thanks to John Coker on this one!



To control where the ejection charge gasses go, I built an ejection cannon from a piece of 24mm tubing and the motor spacer provided with the kit. This assembly is glued to the forward centering ring and fits nicely between the extended motor tube and the airframe.

The final two mods were an addition of 3' of 250lb Kevlar® twine (I also used the elastic that was provided with the kit) and a pair of rail buttons from railbuttons.com.

After building this rocket, I weighed it along with my G-Wiz altimeter, mounting assembly, and a standard 9v battery. The results are not encouraging. The Micro-Hybrid's reported thrust ranges are between a D12 and an E24. If my Micro-Hybrid comes in on the high end, all will be well; if on the low end, I will need lighter electronics. I am currently thinking of buying a Perfectflite mini timer. Another concern is that the G-Wiz requires a certain level of acceleration to begin operation. They have been known to fail on flights that are too slow off the pad.

Finishing:
I had been wanting to try an Easter egg paint scheme and this rocket provided the opportunity. I will refer you to The Rocketry Forum Archive for the details, but this method basically just involves spraying paint into a plastic trash can filled with water and dipping the rocket - just like coloring Easter eggs. This time I have to thank Lee Reep, the inventor and undisputed master of this technique! The painting technique also inspired the 'Dipper' in the Big Dipper Daddy's name.

One caution: don't dip in direct sunlight, the paint dries too fast!

Flight/Recovery:
I chose an E9-6 to see how the rocket would fly on a motor with a low average impulse. I wrapped the end of the motor with tape for retention going up, and used the retaining bracket for retention going down. The speed and altitude were respectable. I used a 12" Mylar chute and, in the place of wadding, a chute protector that I made from a discharged car air bag. The airbag material seems to work great after several tests with both BP and composite motors. I'll be sure to nab more of these if I get a chance!

This has flown four additional times on E9-4's and once each on an E9-6 and D12-5. All of the flights have been successful. Even though I envisioned using this for the MicroHybrid, it has yet to fly on one.

Fat Boy 7x18mm Motor Eater

This is a Fat Boy that flies on seven 18mm motors.

Construction:
Parts list:

* Estes Fat Boy kit
* 18mm tubing for the 6 additional motor tubes
* ~3’ of ¼" elastic
* ~5 “ of ¼" tubular Kevlar®
* First Fire igniter tube
* Lead shot
* 2-part foam (Giant Leap or equivalent)
* Epoxy and wood glue
* Elmer's Fill ’n’ Finish
* Krylon X-Metals purple and red Monokote

I'll start with the business end. The center mount is held in place by the fin set. I dry-fit the stock centering rings and then removed them. Next, I added 6 more motor tubes at the fin-body tube joints. These were placed there vs around the center tube because I wanted more separation between them. I'll be igniting the cluster with quick match and the extra room can be useful. I also extended these 1/2" below the body tube so I can wrap tape around the motor tube/motor boundary. This hurts stability a bit (i.e., will make the rocket heavier), but the coast time will still be too long for some motor configurations. The top section of the motor mount area was plugged with wood glue-soaked tissue and I then backfilled it with 2-part foam.

I used long pieces of 1/4" elastic (from the "use what I got" rocket building philosophy) for separate nose cone and body shock tethers. The body tether is routed through the body tube at the top of the 1/4" lug. It is epoxied to the body tube and the lug is epoxied on top of that. I cut the shoulder off the cone and embedded a Kevlar® loop and lead shot (~6 oz) in 2-part foam. About 1/3 of the cone is available for a second parachute.

The rocket was assembled with wood glue except for the lug. There is no fin reinforcement since the body should come down slowly under its own chute.


Finishing:
I covered the fins with Monokote. Unfortunately, my skills have deteriorated from their already low level so they aren't very smooth. The body and cone were painted with Krylon X-Metals primer. The body was left with this already pretty layer and the cone was painted with my remaining X-Metals purple. The first time I used this paint, the purple clouded badly, however, I'm happy to report that despite the high summer humidity, it came out great.

Flight:
I prepped the rocket with two Fat Boy chutes. The nose cone's chute was packed in the body and the body chute was packed in the cone, so they'd tend to pull each other out.

The unloaded rocket weighs 12oz and will have 1 caliber stability when loaded with C6's. RockSim says:

* Seven C6-7's will push it to 1488' and the optimal delay is 9.6 seconds. The motor delay is a bit short!
* One C6-7 and 6 B6's will go to 691' and the optimal delay is 6.8 sec. A much better match!
* One C6-5 and 6 A8's will go to 316' and the optimal delay is 4.9 sec. Also a good match.
* Three C6-7's and 4 B6's will got 953 feet with an optimal delay of 7.9 sec. Also OK.

The Motor Eater flew nicely on a C6-5 and six B6-4s, all lit with quick match. The boost was a bit slow, but man, did it generate some smoke! The 2nd flight was on a full load of C6's - 3x C6-7 and 3x C6-P. This was a faster, higher flight and also required a long walk.

Summary:
This Fat Boy is a good way to get rid of those extra 18mm motors. I might have been able to get away with a bit less nose weight, but this model is mostly about the smoke and fire rather than performance. If I want performance, I’ll fly my 29mm version.

Phinagain Cruise Missile

I generally scavenge whatever rocket parts I can for future use. This is the story of such a rocket. It is BT-60 based and flies on 24mm motors. I also installed two outboards, although now that it's built, I don't think I will use them. I may add LEDs to the outboard pods, since the cones are translucent and are not solid.


Construction:

1. Fins from the Estes S.W.A.T. This kit was purchased years ago at a close out sale and was used as parts. I recently ran across the fins and went from there. While I was thinking about finishing, I ran across the decals sheet too. I used the 'fins again', hence the silly name.
2. One Mean Machine. Destroy/lose it as you see fit, but make sure the nose cone is recovered undamaged.
3. Caps from the current style of Air Wick® air fresheners fit a BT-55 nicely and look good on the strap-ons.
4. You also need some BT-55.
5. I used two pieces of Totally Tubular T-2 tubing, both for trim and to use as a launch lug.
6. One FlisKits Deuce's Wild! cone, which becomes the tail cone.
7. Three pieces of Totally Tubular T-50mf (thick wall, foil lined) for the motor mounts.
8. Kevlar® twine, elastic and a hook eye for the shock tether.
9. Parachute from the range box.
10. Scrap junk for the payload shoulder, motor blocks, etc.
11. Clay nose weight.

The fins were already cut out (I forget whether they were die cut back then) and three had dowels already installed on their tips. I tried various orientations before I decided on this configuration. The side fins both extend downward and rest against the side pods.

The BT-55 pods have a 24mm motor mount installed. This is not centered but rather rests against the side of the tube where it meets the main body tube. I improvised solid motor blocks by capping the end with a cardboard circle and backfilling with Gorilla Glue. If I ever used these, I'd also have to use a tape thrust ring. I used some scrap tubing to make a shoulder for the plastic caps to rest against. These caps were eventually glued in with Liquid Nails, but only after all the painting and decal sealing was completed.

I had had a couple of Deuce's Wild! cones for a while and decided to use one as a tail cone. I split it in half and hollowed it with a combination of a wood carving knife, a Dremel grinder, and a spent casing wrapped with sandpaper. I installed an eye hook in the balsa as an attachment point for the Kevlar® leader.

I had two smallish pieces of BT-60, so one became a payload section. The shoulder is a small scrap of 38mm tubing with a lengthwise section removed. A paper cap keeps the ejection from blowing through and a piece of elastic was epoxied to the inside of this shoulder.

Finishing:
The nose and tail cones are painted black and the body tube is blue. Both are Painter's Touch paints. I added many of the decals from the original sheet. These match the paint scheme nicely, although the yellow decals seem a bit washed out with the dark background.

Flight:
I added clay to the nose cone until the rocket passed a swing test. It's weight grew, so a D12-3 was required. I angled the rocket into the wind a bit to keep it from the tree line. This resulted in a near perfect ejection and a nice recovery. I flew it four more times of C11-3's, D12-3's and D12-5's, before...loading up a central C11-7 with two C11-3 outboards! I used Quest Q2G2 igniters and lit them with the Cluster Buck relay system. That was overkill, but you can't argue with success. It was another great flight.




Summary:
In my opinion, this rocket looks pretty good considering it was cobbled together from various parts from other rockets--and even air fresheners! Since it will fly on a D12, I may eventually add LEDs to the side pods for night launches. If so, I will also add another BT-60 to move the cone forward, which would allow me to remove some or all of the nose weight.