Scratch 2-Stage EMRR Challenger Original Design / Scratch Built

Scratch - 2-Stage EMRR Challenger {Scratch}

Contributed by Eldred Pickett

Manufacturer: Scratch
(Contributed - by Eldred Pickett - 09/01/09) (Scratch) 2-Stager

Brief:
For t' EMRR Stagin' Challenge, I decided t' build a two-stage rocket with composite motors. Since I had done a 2-stage before, I figured it would be easy. Begad! Ya scallywag! WRONG... Avast! I decided t' do a 3-inch bird with dual deploy and a 19-inch booster with motor deployment. Ahoy!

Construction:
This time I decided t' use alignment rods in t' stage coupler t' keep t' rocket aligned. Aye aye! Avast, me proud beauty! I didn't have any 'sleeves' for t' rods t' slide through, arrr, ya bilge rat, so I went with spaced centerin' rings with holes t' guide t' rods. Aye aye! Ahoy! I've discovered that I really need a drill press. Begad! Because I was usin' a handheld power drill, shiver me timbers, arrr, I wasn't that accurate in drillin' holes through t' 2 sustainer centerin' rings and t' stagin' coupler. It still works, but it isn't pretty. Aye aye!

There are holes in both centerin' rings that are supposed t' be aligned. Well, blow me down! That didn't work out as smoothly as I had hoped.

(Scratch) 2-Stager(Scratch) 2-Stager

T' motor mount is recessed into t' sustainer t' provide a connection for t' top half o' t' stage coupler. Since a 3" tube won't allow me t' get me hand in t' connect t' shock cord, shiver me timbers, shiver me timbers, I made t' fin can on both the sustainer and booster removable. Begad! T' sustainer fin can is held in place by small screws. Aye aye! T' booster fin can will eject and deploy t' booster chute. Aye aye! T' whole project is about 83 inches tall, matey, shiver me timbers, about 3.5 lbs empty, and can fly on 38mm motors.

(Scratch) 2-Stager

Finishing:
T' fit/finish betwixt t' booster and t' stage coupler is a little rough, but once it's painted it might nay be that noticeable. Well, blow me down! Blimey! Begad! Blimey! It *certainly* won't be noticeable on t' pad.

Flight:
Electronics will be a PerfectFlite timer for staging, and a PerfectFlite MAWD for deployment. Begad! RockSim says it will get t' a little higher than 2000 feet with a CTI 153 stagin' t' a CTI G79ss.

For t' 2-stage challenge, arrr, I decided t' build one that used composite motors. Since I have done stagin' before, I didn't expect thar t' be a problem. Arrr! Boy, was I wrong... Ya scallywag! Blimey! T' main problem be t' size o' t' new project. Begad! Arrr! T' previous 2-stager be almost a 4" tube. Ahoy! Begad! That left room for t' timer betwixt t' sustainer fins, and a standard-type ebay. This one is a 3", me bucko, and thar's no room in t' fincan. Begad! So I put t' timer in t' ebay, and ran a connector wire down t' ignite t' sustainer motor. Avast, me proud beauty! Blimey! I had t' splice t' wire so it would disconnect when t' apogee event fired. Begad! T' next issue I ran into was t' stage connector. Well, blow me down! Begad! I decided t' use metal rods t' connect and align t' sustainer t' t' stage connector. Begad! Blimey! I don't have a drill press, so me holes through t' centerin' rings are...less than exact. Last issue was t' 3" bay was too small t' use switches t' power on everything, arrr, so I had t' run all t' wires through a hole in t' e-bay and twist them t' connect. Well, blow me down! Avast, me proud beauty! That posed a problem t' first time I tried t' launch. I test fit t' electronics when I built t' bay, but nothin' be connected. Begad! In t' field, me bucko, I sadly discovered thar wasn't enough space for all the wires t' fit and route t' t' outside. Aye aye! I had t' rebuild t' sled t' avoid that problem for t' next attempt. Arrr! Ya scallywag!

T' field we used has a waiver o' 5000', but I wanted t' make sure I kept t' flight much lower than that. Aye aye! RockSim 7 showed an altitude o' about 3800 feet on a CTI H143/G79ss combo.

Electronics: ARTS board for apogee/main deployment o' t' sustainer, me hearties, PerfectFlite timer for sustainer motor. Begad! T' booster recovers under its own chute by motor ejection. Ya scallywag! Payload: BoosterVision GearCam taped t' t' side. Crude, shiver me timbers, but effective. Blimey!

Launch day: I racked t' rocket, ya bilge rat, set up t' breakwire, and twisted t' wires for power. Well, matey, blow me down! Since I didn't have enough room t' push t' wires back into t' bay, I taped them t' t' outside. That was a mistake... Arrr! T' launch was beautiful! Straight, and staged on cue. Avast, me proud beauty! Begad! T' booster chute came out and it drifted down safely. Arrr! T' sustainer had a good apogee event(drogueless), but I lost sight o' it while followin' t' booster. Avast! There was no main deployment, me hearties, and fellow club members pointed me in t' direction they saw it fall. Begad! While walkin' out for recovery, I tried t' figure out what went wrong. Well, blow me down! Begad! Too many sheer pins? Nay enough BP? When I got t' it, arrr, I immediately knew what happened. Arrr! Begad! T' armin' wires were taped t' t' bottom o' t' sustainer. Blimey! When t' apogee separation occured, it ripped t' wires out o' the altimeter, killin' power. Avast, me proud beauty! Ya scallywag! AUGH! I powered up t' ARTS board later, arrr, and t' data showed 1700 ft accel, shiver me timbers, 1500 baro. Arrr! WAY short o' Rocksim's prediction, ya bilge rat, so t' loss o' power probably scrambled t' data. Begad! But other than t' ebay being crunched, and t' booster bein' scorched by t' sustainer motor, it didn't come out too bad. Ya scallywag! I can replace t' ebay and fly it again.

Setup Launch

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