+# Altus ARCAS
+
+## Motivation
+
+This airframe started as an on-sale 4.5" HV ARCAS kit with 98mm motor mount
+from [Composite Warehouse](https://compositewarehouse.com/).
+
+## Design Details
+
+As the prototype ARCAS included a boat tail but the kit did not, I decided
+to modify the kit. I added a a fabricated-in-place epoxy tailcone about 3
+inches long, which shifted the fins aft by that amount. This in effect gave
+me another 3" of length to play with in the fin can part of the airframe, which
+meant a CTI Pro98 6xl case would fit very nicely.
+
+I also did a thing I'm growing to like where the "electronics bay" is just a
+stepped bulkhead with stuff hanging behind it, which also serves as the forward
+end of motor retention using all-thread into the forward closure and a lifting
+eye ahead of the electronics. This allows for hard attachment of the forward
+airframe tube in flight, with dual deploy from a single airframe break at the
+back of the nose cone
+
+The plan was to complete the project in time to fly at Airfest 2022 when my
+son would be in attendance. A CTI N3301 White motor which was in stock at
+Chris' Rocket Supplies was purchased for the flight, and a high altitude
+flight request was filed with and approved by the Kloudbusters. The motor
+was delivered to us on the flight line during setup on Thursday evening in
+the Rocket Pasture (to avoid hazmat shipping charges).
+
+Sadly, a glue-bonding disaster occurred that night in our hotel room, as the
+Gorilla Glue recommended for use in glue-bonding the grains in the liner
+"kicked off" before we could get the last grain in the liner, leaving us with
+an utterly un-flyable mess!
+
+To avoid just tossing the motor, my big plan then became to use my huge 1930's
+era metal lathe to cut the liner off the grains, cleaning them up to be glued
+in to a replacement liner. Thanks to help from Chris, we managed to procure
+an exact replacement liner assembly from CTI.
+
+I hoped to get the motor rebuilt in time to fly on the Argonia Cup weekend in
+2023, and the Kloudbusters re-approved my high altitude flight
+request. Unfortunately, my father passed away in March before the motor work
+could be done, throwing that plan out the window.
+
+Fortunately, I was able to make time to extract the grains from the original
+liner over the summer of 2023. The only problem is that at one point, the
+cutting tool on the lathe got loose in the holder and jambed into the end
+of one grain, forcing me to trim that grain to get a non-damaged end. I lost
+about 303 grams of propellant in the processing, leaving 98.1% of the original
+propellant mass. With a third high-altitude flight approval in hand from the
+Kloudbusters, my business partner Keith and I managed to get the grains
+bonded in to the replacement liner before leaving for Airfest 2023, and the
+rest of the motor assembly went smoothly.
+
+The recovery system plan was a 2' Giant Leap TAC drogue to be released at
+apogee by blowing the nose with 2 2-56 nylon shear pins off using 2.5g primary
+and 3.0g backup 4F BP charges in CPVC charge cannons, then releasing the main
+in a deployment bag witn a Tender Descender slightly modified to fit two of
+the Chinese e-matches I prefer so both flight computers on board could have
+a chance of getting the laundry out.
+
+The OpenRocket design file is
+[ARCAS_ala_Bdale.ork](/rockets/airframes/AltusARCAS/ARCAS_ala_Bdale.ork),
+and that design file plus all content on this page are released under the
+[Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/legalcode) license.
+
+### Electronics ###
+
+One each TeleMega v3.0 (primary) and TeleMetrum v2.0 (backup).
+
+## Build
+
+## Photos
+
+## Result and Lessons Learned
+
+The airframe was 49 lb 13 oz on the rail, and flew on Saturday of Airfest
+weekend, reaching Mach 2.2+ on the way to 36555 feet above ground! This was
+a new personal best for Bdale.
+
+Recovery went well, except that the main parachute was clearly under-sized.
+The ground hit appears to have been at about 47.5 ft/sec. One fin popped
+loose as a result of the hard hit on landing, and later inspection revealed
+that the fin can airframe tube "banana'd"! There is a clearly pronounced
+bend in the tube starting a bit aft of the front of the motor case. Since
+the motor mount is fairly short and it's a 98mm case inside a 4.5" inside
+diameter tube, it sure looks like the tube really was bent on landing. It
+could not have bent during ascent, and the hard hit plus long moment arm
+plus very high temperatures on the day and from Mach 2+ flight must have
+contributed to soften the tube enough to let it bend!?! None of us have
+ever seen anything quite like it!
+
+I'm still satisfied in considering the first flight of the airframe a success
+since my mission objectives of a new personal best altitude and proper
+operation of the recovery deployment were achieved. However, the fact that I
+clearly will need to rebuild/replace the fin can before I can fly again (on
+a larger main parachute next time!) is annoying.
+
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