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English Electric Thunderbird build

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delta22

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The English Electric Thunderbird is a very cool looking surface to air missile used by the British from 1959 to 1977. It has four drop off boosters with canted nose cones and engine nozzles.

FlisKits makes a nicely detailed kit of this rocket designed to fly on 18mm motors. Look for it under scale kits.
http://www.fliskits.com/index.htm

The first time I saw a FlisKits Thunderbird, I knew I had to build one. I bought the kit, then decided to supersize it.

A couple good links on the actual rockets:
http://www.36regimentra.org.uk/TLaunch/id16.htm
http://www.braw.co.uk/thunderbird/thunderbird.htm

The Vatsaas brothers built and flew one:
http://www.vatsaas.org/rtv/arsenal/bradrocs/tbird/thunderbirdconstruction.aspx

I used the references above, including the FlisKits kit and a RockSim file posted on EMRR of the Vatsaas Thunderbird, to work up the design for the rocket I am building.
 

delta22

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A RockSim 9 file of the build is attached, as well as a screenshot.

The build will match the RockSim model except the build will have canted booster nose cones and motors, which RockSim can’t model. The 12oz mass in the NC will be added for stability, the 16oz mass in the middle of the rocket is what I am estimating a thin layer of fiberglass will add. While this rocket does not need FG for flight, it will do better during recovery and travel with it.

This is both a 2x upscale of the FlisKits kit, and a 3/20 scale model of the English Electric Thunderbird surface to air missile.

The build is very similar to the FlisKits kit, except the nose cones and back of the center tube extend slightly further.

Build matches actual Thunderbird closely except for the very back of the rocket where the cluster of engines is installed.

I wanted a build that would fly on a cluster of 24mm engines and do a simple recovery. This will fly on 11x 24mm motors and use engine recovery. The boosters will be permanently attached.

Parts for the build are LOC tubing and central NC. Body tube is 3.1” diameter, boosters are 38mm. Using FlisKits baffles in the 7x 24mm central motor tubes. There will also be 4x 24mm canted outboards.

The flame effect when this takes off will be very cool.

View attachment 14 Thunderbird.rkt

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Pantherjon

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A RockSim 9 file of the build is attached, as well as a screenshot.

The build will match the RockSim model except the build will have canted booster nose cones and motors, which RockSim can’t model.
True about RS not being able to do the canted nose cones..However you can do the canted motors..You would need to edit the *.ENG files to give the nozzles the correct cant angle..I believe there is an article on Apogee's website on how to do it. The 3D model won't show the 'canting' of the motors, but with the edited ENG files should simulate correctly the thrust characteristics of canted motors.
 

delta22

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Pantherjon, thanks for the tip.

I upgraded to RockSim 9 because it adds the ability to easily do external pods.
Earlier versions required a workaround.

RockSim is very helpful planning out a complex scratch build such as this, among other things providing fin templates, stability calculations and flight simulations.
 

jflis

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Boris,

I was hoping you'd tackle this project :) Can't wait to see what you come up with! Any chance you would have anything together enough to warrant displaying it at NARCON???

jim
 

delta22

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Boris,

I was hoping you'd tackle this project :) Can't wait to see what you come up with! Any chance you would have anything together enough to warrant displaying it at NARCON???

jim
The goal I am shooting for is to have it 100% completed by NARCON.

I would be honored to have it as a display piece at your table(s) if there is space.
 

n3tjm

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Hmm. I wonder where you got the loc tubing for that project ;)

Sounds like an awesome project.
 

jflis

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The goal I am shooting for is to have it 100% completed by NARCON.

I would be honored to have it as a display piece at your table(s) if there is space.
"...if there is space".... Jeeze! That reminds me of the call I got from a university that had an event where I had a booth. They had a mix up on their floor plan and actually called me to ask if I would have any problem if the astronaut they hired for the show set up his book signing booth along side me....

Yep, I'll have room for it! :)

(Yo! Bill! 'gonna need another table at NARCON... :D )
 

delta22

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Epoxied and assembled the FlisKits baffles.

Glued the 7x 24mm motor tubes together, made them 17" long to reduce the heat the baffles see and move the chute higher. Also the length of the clustered motor tubes, in combination with the baffles, eliminates the possibility of an unignited motor being ignited at the wrong end by another motor's ejection charge.

Epoxied a piece of the very heavy duty 1/2" tubular Kevlar from Top Flight Recovery to the motor tubes. Went that heavy to reduce the possibility of tangling or zippering. One booster tube is seen on the table.

Then slid all but 1" of the motor tube cluster into the 30" body tube. Body tube, like the 4x booster tubes, has 2 wraps of 1.3 oz fiberglass for surface hardness.

My son Paul holding the center section of the rocket. The 3.1" rocket is 42.5" long. When completed, will likely weight close to 6 lbs with 11x 24mm motors loaded.

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TheAviator

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This looks like quite the project! I read your article in SpRocketry a while ago and was thoroughly impressed with your cluster technique. Out of curiosity, what are you planning to use in the way of motors? I would say go for a bunch of AT White Lightning, but I know that would get really expensive very quickly. Also, planning on using Q2G2's?

Keep us posted (and as always, more pics are better :D!)
 

delta22

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Out of curiosity, what are you planning to use in the way of motors?
I'm very partial to BP clusters. Like the flame, smoke, smell, quiet hiss (and low cost). As an engine deployed rocket, I'm not going for much altitude, but more for liftoff effect.

RockSim predicts 450ft altitude with 7x D12-5 and 4x D11-P.

Substituting 1x to 7x E9-4 for the D12-5 puts the predicted altitude between 480 and 730 ft. The longer burn would be nice.

Also fun would be to put one central AT F32T in the center with BP motors all around.

While I do like the flame and smoke of White Lightning, I have found clustering 24mm WL motors to be a problem. The small nozzles are not compatible with any available igniters that work with clusters, and the small motors demand a long hot burn to fire. As you pointed out cost is also an issue.

I plan to use Rocketflite MF ematches to fire the Thunderbird. These work great for clusters.
 
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delta22

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I received a question about using 24mm AP engines in clusters.

The only motors is this category I have tried to cluster are the AT E15 WL single use motors. These seem to be good, low-cost motors for single engine flights that ignite well with the supplied Copperhead igniters.

However, the nozzles are so small that 26 awg wires fill too much of the nozzle opening. The wires can either CATO the motor or de-pressurize the motor causing the motor not to light. Both Rocketflite MF and (12 and 24 inch) ML igniters, as well as FirstFire Jr. igniters are all 26 awg.

I would expect a motor with 30+ average newtons thrust to have a large enough nozzle that these problems would likely be reduced or eliminated. Using a fast propellant like Blue Thunder would also help ignition reliability. I have used Rocketflite MF and ML igniters to successfully fire a wide range of 29mm AP motors.

I plan to try the AT 24mm F32T SU motor in some clusters this year. The AT 24mm F39T reload should also work well. The larger nozzle and the fast propellant should yield good results clustering with 26 awg igniters.
 

delta22

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Tried several different cones to form the four canted booster nose cones. The Thunderbird pictures appear to have more canted cones on the early rockets and slightly less canted ones on the later Thunderbirds, which was the effect I settled on.

Used an online tool on EMRR to make a conical cone about 10% oversized and 1.5 times as long and the base diameter. Placed these at a canted angle onto a 1" piece of 38mm coupler tube topped with a 1/8" piece of 38mm tube.

To strengthen this, put 8 pieces of overlapping fiberglass tape inside the cone assemblies.

Then spread a generous amount of thick, fast epoxy (Locktite 5 minute) onto the tape. Learned this method assembling Applewhite saucers, and applied it to a Sirius Rocketry Saturn V build last year.

After sanding the exterior, the cone is well formed in addition to being very strong. Paper and cardboard cone was 0.15oz, after tape and epoxy 0.65oz (each).

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delta22

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Cut and shaped 8 of the 12 fins on this rocket. Used 3/16" basswood for these.

Then discovered that the longer fins were too long when trying to place them on the body tube.

The RockSim template for those fins printed on two pages. I taped them together and used it. Apparently somewhere between RockSim, Windows, and the printer the split to the second page was not accurate.

Shortened and reshaped the longer fins again as necessary.

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delta22

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Initially used a jig to position fins for attachment. This jig has worked very well attaching 3 and 4 fins at a time to more conventional rockets.

However, I was not able to sufficiently control play in the jig setup pictured. Six times I glued on 2 fins and then had to snap them off at the glue joint after finding alignment off.

Resorted to aligning fins using eye and right angle which worked out OK. I carefully mark the end of the body tube on the line where the fin attaches and at 180 degrees. Then line right angle on both points and the fins.

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delta22

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Taped off fillet edges and used an 18mm spent motor case to form fillets, using Locktite 5 minute epoxy. Like it for the speed and ease of handling.

Then applied 2 layers tip to tip of 1.3 oz fiberglass using West Systems 206 epoxy. Using this on all tubes and fins to harden and strengthen the rocket without adding too much weight.

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redsox15

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boris,

the fins look great!...how did you get them so uniform.

Also, will this bird be flying at NERRF this year?

Looking great!

Matt
 

delta22

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boris,

the fins look great!...how did you get them so uniform.

Also, will this bird be flying at NERRF this year?

Looking great!

Matt
Thanks. I hope to fly this repeatedly at CMASS' Amesbury field and also at NERRF. Other than being very clustered, it will be a simple engine deploy flier that will normally fly to 400-900ft.

Below are pictures showing how I formed the fins. First cut out a paper or cardboard template and draw out the fins on the wood. Cut them with a fine tooth saw.

Then clamp all fins together and sand each edge to make fins exactly the same size. I only show two fins here because that is what I had ready when I took the picture. I will really sand these fins with all four fins clamped together later this week.

Mark a line on the center of the edge to be sanded down.

Then sand at an angle, repeatedly adjusting pressure but keeping angle steady until the pencil line just starts to dissapear.

I used 120 grit for the two sanding steps noted above and then did a final sand with 220 grit. It took me at least 4 hours to make the 8 fins completed so far.

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RocketFeller

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Great build!

I am really impressed by your craftsmanship on the canted nosecones - they look really good.
 

delta22

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Thanks.

This weekend cut out and sanded booster fins to shape.

Experimented with tapering the entire body of the big fins, as the scale rocket does and FlisKits suggests, but was not satisfied with the flatness of the taper or how long it was taking to achieve. So I went with leading and trailing edge tapers only, similar to the other fins.

Used more as it was intended, the jig worked well attaching the big booster fins.

Used a 24mm motor to form fillets from the big fins to the booster tube. This area of the rocket deviates from scale and Fliskits. In this build all of the fin's root chord meets the booster tube for greater fin strength.

"The Chinese Rocket Chair of Death!"
Well not really, it was a convenient place to hold fins while filleting the tip fins.

Fiberglassed booster fin system tip to tip, using heavier glass only here to strengthen these big fins. 6oz covered by 1.3oz.

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delta22

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Sanded down booster fins. With 7 oz of FG tip to tip on a shaped 1/4" basswood core, they are strong and light.

Glued on the bands which are the mount points on the actual Thunderbird.

Made up a plug and inserted it near the mid-point of one booster tube. That tube will have a removable nose cone and offer the option of housing an altimeter.

Glued on nose cones, painted the inside of the tubes with a thin coat of resin, and fiber glassed the tops of the tip fins, all using West Systems 206 epoxy.

Structurally completed boosters are 6 oz each. The four boosters weigh 1.5 lbs and the center rocket body is another 1.5 lbs. The weighted nose cone and recovery will add about 1.5 lbs more.

With 11x D motors, add another 1 lb. More If some E or F motors are mixed in. Projected flight weight 5.5 to 6 lbs.

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delta22

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Painted the exterior of the nose cones with West 206 epoxy, after internally reinforcing it with a thicker layer of internal epoxy and noted in post 13.

This saturated the paper cone that originally gave it shape to the point that light easily travels through it. The pictured cone is illuminated from the inside and is very hard.

After hours of sanding, rocket body parts are smooth and well formed. Even on the the very tip of the fin edges where I sanded through the fiber glass, the basswood is very hard due to being saturated with epoxy.

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kelltym88

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Wow Boris, fantastic skills! I never thought about adding the fillets first, and then laying the glass. I'll have to try that. and using spent casings as well, brilliant.
 

delta22

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Thanks. To be honest, all the fiber glassing techniques noted here for the fins and body are methods I read about online. Very glad the information is helpful. I did get creative putting together the booster nose cones.

Taped off the areas where the boosters will be glued to the sustainer, getting ready to paint them first.

Also shaped, epoxied and filleted in two mount points for rail buttons using 1/4" marine plywood. These are the two stubs coming off the booster in the last picture.

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delta22

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Brushed on two coats of latex primer. Also used Bondo spot putty to fill in rough spots.

I've used this method on a couple other rocket projects in the past with good results. The latex provides a thick fill covering many small imperfections. Followed by plenty of sanding, all trace of brush strokes is removed.

Epoxied in three 8-32 all thread rods for motor retention. Rods are 3" long of which 3/4" is exposed.

Next week will spray pain Krylon primer and final coats. Body will be Hunter (dark) Green and body Cream Beige, matching original missile.

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delta22

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In order to assure flight stability, added 18 oz of lead shot to nose cone.

Used West 206 epoxy to secure lead, an internal liner of 6 oz FG, and the Kevlar recovery line. The internal liner of FG is just to hold lead and Kevlar securely in place.

Inserted and inflated a balloon to help push FG against NC interior while curing.

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delta22

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After an afternoon of sanding down the Bondo and Latex primer, rocket parts are finally ready for spray paint.

Had some minor basement flooding to clean up first. Nothing important damaged.

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delta22

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Sprayed new Krylon grey primer on rocket body parts. Also rough sanded the LOC 3.1" plastic nose cone and sprayed with Krylon white primer.

Three days later lightly sanded the body tubes, sprayed again with primer, then with Krylon Hunter Green.

Primed and sanded the nose cone a couple more times.

I know a number of folks have expressed concerns about the new Krylon spray paints, but I like them. Compared to the old Krylon, they smell less, cover better and the nozzle is much easier to press for long periods of time.

It is necessary to keep the nozzle moving quickly and accurately over the work to avoid drips, but the reward is fast coverage.

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