From: Bdale Garbee Date: Wed, 6 Sep 2023 20:13:09 +0000 (-0600) Subject: add Altus ARCAS to the airframes list X-Git-Url: https://git.gag.com/?p=web%2Fgag.com;a=commitdiff_plain;h=fa5b1e8a8c860b7449912978dd014800bcb61e51 add Altus ARCAS to the airframes list --- diff --git a/rockets/airframes/AltusARCAS/ARCAS_ala_Bdale.ork b/rockets/airframes/AltusARCAS/ARCAS_ala_Bdale.ork new file mode 100644 index 0000000..128d607 Binary files /dev/null and b/rockets/airframes/AltusARCAS/ARCAS_ala_Bdale.ork differ diff --git a/rockets/airframes/AltusARCAS/index.mdwn b/rockets/airframes/AltusARCAS/index.mdwn new file mode 100644 index 0000000..4d83011 --- /dev/null +++ b/rockets/airframes/AltusARCAS/index.mdwn @@ -0,0 +1,98 @@ +# 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. + diff --git a/rockets/airframes/index.mdwn b/rockets/airframes/index.mdwn index bf0e9c8..a69d7ba 100644 --- a/rockets/airframes/index.mdwn +++ b/rockets/airframes/index.mdwn @@ -35,6 +35,9 @@ the meantime, these are a few of the projects that mean the most to us: ### Others +* [Altus ARCAS](./AltusARCAS) + 4.5" ARCAS with 98mm motor mount + * [V2-8](./V2-8) 8-inch V-2