English Electric Thunderbird build

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Thanks Jim, that means a lot coming from you.

Anybody want to build a cool looking Thunderbird? FlisKits is selling them :)

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In the first picture can barely make out the 3/8" strip of masking tape sitting under the paint.

Masked around this area and peeled off the strip of tape that was under the paint.

Then sanded the strips of fiberglass surface now exposed.

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Removed the tape from the boosters.

Spread thick, fast epoxy (Locktite 5 minute) onto the exposed area on the center rocket body.

Removed the tape from the center tube, one area at a time. Then put boosters in place one at a time.

Used small pieces of masking tape with alignment marks to position front and back of each booster. Made sure the forward band that all body tubes have were all aligned.

When it came to making sure the angle of boosters' fins was properly aligned, I threw everything but the kitchen sink at that one, as failure was not an option this far into the project.

I used two different right angles (largest one pictured), a ruler and a level. Rotated between evaluation methods until the glue was set.

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The fins came out well aligned and the rocket looks cool.

This is going to look really nice going up on a column of fire and smoke from a cluster of 11 motors.

The nose cone that this rocket will fly with is still being painted. So I installed another (unfinished) nose cone that is the same shape for these pictures.

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Thanks.

Yes, definitely bringing it to NARCON.

It will be a display piece at FlisKits if there is enough space, or in the rocket garden. Also will bring this and the TOGinator to my "Fun with Clusters" presentation Saturday morning.
 
Thanks.

Yes, definitely bringing it to NARCON.

It will be a display piece at FlisKits if there is enough space, or in the rocket garden. Also will bring this and the TOGinator to my "Fun with Clusters" presentation Saturday morning.

Oh! Dude... We'll find the space... :)
 
Painted the nose cone Cream colored to resemble the unpainted fiberglass nose cone of the original Thunderbird.

It seems holding a model of a surface to air missile has a strange effect on a 12 year old boy.....

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In addition to painting the weighted NC (right), painted a light weight spare as well for display at NARCON.

Also made up a simple stand using a 2" band of LOC 7.6" tube and 1/8 plywood. Stand secures to the three threaded rods the rocket uses for motor retention.

I like the last picture as it make the rocket look twice its actual size.

Can see the hood I use for all paint and epoxy work, which has a work table and light, heat lamps and an exhaust fan.

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It is sweet looking in person, I can tell you that! Boris was kind enough to put it up on display at my booth at NARCON (I could scream as I had already taken pix of my booth and forgot to get another after he put it up...)

Surprisingly light too, considering the size...

Can't wait to see it fly!
 
NARCON was a blast, thanks to Jim Flis and FlisKits for sponsoring the event.

Picture of the FlisKits display of their many cools rockets, including my upscale of their Thunderbird.

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Used 1 inch stainless steel machine screws to attach rail buttons. These serve to reinforce the small plywood standoff the rail buttons stand on. The screws have a deep and snug enough fit that no glue was needed.

Left just enough slack so the rail buttons can rotate, making the ride up the rail as low resistance as possible.

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Using Top Flight Recovery parts for recovery:
45" chute for rocket body (4.2 lb recovery weight)
30" chute for nose cone (1.8 lb recovery weight)
12" square Nomex pad
1/4" tubular Kevlar

Used Robert DeHate's method to loop the tubular Kevlar onto itself for attachment to the main.
Shown here: https://www.geocities.com/rdh82000/Tips/kevlar.htm

My wife was kind enough to sew the Nomex pad to the 1/4 Kevlar, making it into a simple deployment bag of sorts.

Rolled the chutes into the Nomex as shown in pics 3 and 4, folding the bottom of the Nomex to protect the chutes from ejection heat.

The inside of the nose cone is open, and the space is needed for recovery gear. I repeatedly pulled NC off and confirmed that all recovery parts deploy smoothly and effortlessly. Will do tests with deployment charges later this week. Want to be very sure of a clean recovery after putting about 100 hours into this build.

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This is going up on the 24th?? Please, please,please... :)

I'm probably going to miss it though :( I have a class in Leominster at 2:00 so I am leaving around noon time...
 
Then I'll plan to fly it before noon on 4/24/10 (at the CMASS launch in Amesbury, MA).

....I love the smell of black powder in the morning.....

If all goes well, I'll send it up a second time in the afternoon.
 
T minus 2 days...

Saturday is looking good for the first CMASS launch of 2010.

Set up a Perfectflite HA45K altimeter in a 38mm booster tube. Featherweight switch on the other side of the board. For simplicity and easier access, ran wires to ejection charge outside rocket where they go from electronics to recovery compartment.

Test fired an ematch twice successfully and then a 1.0 g ejection charge which triggered a clean, quick deployment.

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Loaded with 11x D motors for the first flight.

The 7 central motors are D12-5, so the rocket will fly with both motor and electronic ejection.

At a total impulse of about 190 Ns, with 130 N of thrust, this will be equivalent to an "H130".

Flight weight is 6.6 lbs.

RockSim is predicting about 10 G acceleration off the pad and 480 ft altitude.

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Saturday was beautiful in Amesbury, MA, with no clouds, light winds (at least until about 2pm) and temperatures in the 70's.

I prepped the Thunderbird with 11x D motors, using 7x D12-5 in the center as planned. As the pictures show, used small wads of tissue paper first to retain the Rocketflite ematches in each motor. Then taped each igniter in place.

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The liftoff was very straight and dramatic, unfortunately it was also very slow.

I knew it was in trouble when the motors finished their burn well under 100 feet up.

The last picture below was 4 seconds into the flight, when the rocket started to fall. It gradually laid over flat as it fell onto soft ground. Motor ejection popped the NC just before it hit the ground, but there was not nearly enough time for the chutes to deploy.

The Perfectflite altimeter never armed the ejection charge, as the altimeter needs to see at least 160 ft altitude change to do this.

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Damage was moderate. One booster pod separated cleanly and one has a tear mid-section.

I joked after the flight that the rocket was going for authenticity by separating a pod.

Will not take long to repair. However, the next flight will have to wait until the next launch at a big field, 2-3 months from now.

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Examination after the flight showed that 7 of 11 motors had fired. With D12's this just wasn't enough total thrust or impulse to get a 6.6 lb rocket up very high.

I had been very careful placing and retaining the igniters, and had expected to fire more motors. 3 of the 4 motors not fired showed signs that the igniter had fired but failed to start the motor, the in the fourth it did not appear the igniter fired.

Next time I will:
1) replace some of the Estes D's with E's
2) use more pyrogen when dipping these igniters
2) load a soon to be available AMW/CTI 24mm F or G reload in the center motor tube

I think if one more motor had fired the altimeter would have armed and the chutes would have deployed. Went with all D motors for the first flight to minimize weight at the back of the rocket and confirm stability. As the rocket proved very stable, slightly more motor weight should not be a problem for future flights.
 
The Perfectflite altimeter never armed the ejection charge, as the altimeter needs to see at least 160 ft altitude change to do this.

Get a Pico altimeter from DeHate. The single event is accelerometer based and would have worked on your flight. You may have seen it save one of my hybrids last year. I don't think it made 100 feet and the chute popped right at the top.
 
Examination after the flight showed that 7 of 11 motors had fired. With D12's this just wasn't enough total thrust or impulse to get a 6.6 lb rocket up very high.

I had been very careful placing and retaining the igniters, and had expected to fire more motors. 3 of the 4 motors not fired showed signs that the igniter had fired but failed to start the motor, the in the fourth it did not appear the igniter fired.

Next time I will:
1) replace some of the Estes D's with E's
2) use more pyrogen when dipping these igniters
2) load a soon to be available AMW/CTI 24mm F or G reload in the center motor tube

I think if one more motor had fired the altimeter would have armed and the chutes would have deployed. Went with all D motors for the first flight to minimize weight at the back of the rocket and confirm stability. As the rocket proved very stable, slightly more motor weight should not be a problem for future flights.

Not to be a troll, but did anyone else see any issues with this rocket? I mean, a 6.6 pound rocket on a cluster of Estes motors? It was marginal AT BEST if they all fired, because you got 7 of the 11 and it didn't even get high enough to arm the altimeter. Imagine if it had tipped off the rail and towards the crowd.

Let's do some quick math:

7/11 = 125/x
x = 196.4 feet

where:
7 = number of motors burned
11 = total motors in rocket (most possible to be burned)
125 = assumed altitude (looks to be generous)
x = altitude had all motors burned (linear assumption)


We know that this is not linear, so let's assume another 50 feet on top of this. So that's 250 feet. Even assuming another 100 feet gives you 300 feet, which in my mind, is still very generous.

I just don't see how this was allowed to fly. There is underpowered, and then there is underpowered with a cluster entirely reliant upon every motor firing to be a successful flight. Had it not been fiberglassed (overkill), it may have been a little less obese and could be a decent flying model. It's just too heavy, too draggy, and too underpowered to fly reliably, IMHO.

Cool design, though.
 
Dave

Boris is an experienced L2, and has flown many flight with up to 30 motors with an extremely high percentages of engines igniting. His Rocksim of the rocket had the apogee at 480' and a peak acceleration of 10 G (the T/W is 11 or 1 per engine) so even with 4 engines out he would have expected to exceed 160' and trigger the altimeter, and there was no wind when he launched.

Most importantly, there was the required 200' separation distance between the rocket and the closest spectators and the launch rod was angled away from the spectators.

Rockets do occasionally fail to operate properly and that's why we have range safety procedures to handle the failures. The required separation distances and angling the rod away from the spectators toward a cleared ballistic recovery zone are two proven methods to mitigate flight failures and insures that no one will be injured in the event of a failure.

I was not the RSO but IMO, the planning of this flight and the launch pad location met all reasonable criteria for oking the launch. The ballistic impact zone was clear so if there was launch or recovery failure the rocket would land in the designated ballistic impact zone. And that's what happened.

Bob Krech, CMASS Senior Advisor
 
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