Last winters project included our first high power rockets. Both of which were BSD kits, a Horizon and a Sprint.  This winter I've decided to get ready for a possible Level 2 cert attempt in spring of 2004.    The rocket I choose for this was again a BSD kit, the 4" THOR.

The Thor is a split finned rocket with a 54mm motor tube taking motors in the I, J, and K range.

Below will detail the building and finishing of this rocket.

The above pictures show the parts that came for the kit.  The kit includes motor retention, parachute, tubular nylon for the recovery system, body tubes, couplers, rail buttons, nose cone, ply centering rings, and ply fins. The directions for these kits are of Estes quality only for high power birds, numerous illustrations, well written and in logical order.

I did have one problem with the directions as they stated the lower fins were 6 3/4" in length, but they only actually measure 6.5" so if you don't catch that before cutting fin slots it could cause a little trouble.

The first step in the directions was the assembly of the motor tube. This consisted of a 54mm motor tube with three centering rings.   The bottom centering ring included 2 blind nuts for motor retention, I deviated a little and added a third.  I may possible put all three on the motor or if using an adapter I'll use one for the adapter and two for the motor.

The upper centering ring includes an eye bolt for attaching the recovery system. The centering rings were attached with 30 min epoxy. I did not attach the bottom centering with epoxy at this point as I wanted to add internal fillets for the bottom fins, a little extra insurance for hard landings.

The next steps consisted of finishing assembly of the booster section.  The tube was premarked for fins slots which you have to cut yourself.  With a sharp hobby knife it's not too bad of a process.

Next the fins were attached through the wall to the motor tube, again with 30 min epoxy. A bit of care has to be taken to insure the fins line up.

After attaching the fins I then applied generous fillets with 30 min epoxy, this was probably the longest step just waiting for the epoxy to dry.

After fillets were completed the supplied rail buttons were installed, as well as two 3/32" holes were drilled into the body tube near the top for pressure relief holes.

After the booster section was completed the electronics bay and payload bay were built.  This was simple, and consisted of epoxying in the bulkhead plates into the tube couplers and then epoxying the couplers into the body tubes.

Each bulkhead was setup with dual eye bolts one to either side to give me as many options as possible for later flights.

The first bay which is 10" in length will be setup as an electronics bay, and the upper bay which is 24" in length will be used for the main parachute in dual recovery applications.  The payload bay received two 1/8" vent holes. The electronics bay received 4 port holes and one additional hole for the altimeter arming wires.

After the above steps were complete we were ready to see what the rocket was going to look like assembled. As the BSD directions say, "It's starting to look like a rocket isn't it"

A day later after all the epoxy had thoroughly dried it was ready for paint. I've seen many paint schemes on this rocket but decided to go with the stock scheme that was depicted in the directions.  One of the reasons for this was to match the electronics bay color so that it would match my 4" Horizon.   That way I could use it interchangeably between the two rockets.

The paint dried and it was time for the finishing touches. 

BSD as always supplies outstanding vinyl decals, high quality and a pleasure to use.  As always they really set the rocket off after they've been applied.

Complete this dual finned rocket stands 85" tall and is 4" in diameter.  Our end weight with everything but the motor came in at 83 ounces. As always I went heavy on the epoxy, but I like them that way.

The plan as of this point is to obtain a Missile Works RRC2 altimeter, then fly a couple of test flights first thing this spring, hopefully with I211's.  After that we'll stick a J350 in it and go for Level 2 certification.

Simulations show approximately 1900' on the I211 and 3000' for the J350.  I'll use motor ejection for the drogue deployment on the cert flight with altimeter backup, then altimeter deployment of the main at 800 feet.

That's the plan as of this point, the first step is done, the rocket is ready, December 2003.

***January 2004***

Ok, I've got the altimeter bay completed now, it's a Smokin Rockets Alti-Tube slightly modified for my rocket.

The Alti-Tube is a interchangeable system that can be moved from rocket to rocket, which is what I wanted.

To the left is the Electronics Bay, and to the right is the Alt bay, the Alt bay still needs holes drilled into it however.

It is centered inside two centering rings to hold the bay centered in the rocket. The centering rings are not glued, rather they are a tight fit, plus a heavy wrap of 1/2" masking tape on either side. This makes the bay interchangeable between my 3 and 4" rockets. Pull the tape and slide the rings off and change out with 3" centering rings.  I can also make adjustments and move the rings to clear vent holes, or other items as needed.

In the middle is the sled which will have the RRC2 altimeter attached to it, it then slides down into the Alt bay which is closed on each end.

Another view of the sled which is G10 material. One of the centering rings had to be sanded down substantially as it had to fit inside the coupler tube on one end. This same end will have an eye bolt attached for backup attachment by kevlar to an eyebolt in the Electronics bay just incase the plastic rivets were to ever fail it would still be attached to the rocket.

It's a very good fit so I doubt it would slide out but better safe than sorry.

***February 2004***

With the arrival of my Missile Works RRC2 altimeter I now have the Altimeter bay completed and the altimeter mounted.

Below are pictures of the completed altimeter bay.

This is a view from the top of the Electronics bay looking down and seeing the top of the Altimeter bay.

Wire running out the top and through the body tube of the rocket is the power switch. This will be accomplished the K.I.S.S. way by just twisting and taping the wires then pushing them back into the rocket.

Here is the Altimeter bay sliding out of the Electronics bay. The main Electronics bay is 4"x10" and has four 9/64" holes for ports so that the altimeter can get it's readings. The altimeter bay has six 9/64" holes for readings. Here it didn't seem as important to me as long as the minimal amount of holes to get a reading are there, more shouldn't hurt by my way of thinking as these holes aren't in the slip stream.

The electronics bay empty, at the bottom is another 9/64" hole that the ematch will pass through, eye bolt to connect to the altimeter bay if desired for more retention.

Here is the top of the altimeter bay. Two loose wires are the arming wires and the terminal block is the connection for the main. The cord is kevlar and just there to assist with pulling the sled out of the bay.

Here is the altimeter bay completely removed showing two of the port holes.  The barometric sensor is in the bottom third of the tube so I'm trying to keep port holes away from and not right over it.

Here is the sled sliding out of the altimeter bay.

Here is the altimeter completely removed from the bay, bottom right black circular piece on the circuit board is the barometric sensor, you can now see how it's offset from the vent holes.

Here's the bottom of the altimeter bay, center hole is plugged/epoxied, off center hole is where the lead for the apogee ematch will come through.

Well that's all for now, the THOR is expected to fly in either March or April of 2004 for my Level 2 attempt.

Built 12-23-03

Diameter 4", Length 85", Weight 100 oz. 54mm motor and parachute recovery.

See THOR's certification attempt here.

Thor Flight Logs

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