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, shiver me timbers, I decided t' build a two-stage rocket with composite motors. Avast! Since I had done a 2-stage before, I figured it would be easy. WRONG... Avast! Ahoy! I decided t' do a 3-inch bird with dual deploy and a 19-inch booster with motor deployment. Avast, me proud beauty! Begad!

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

There are holes in both centerin' rings that are supposed t' be aligned. 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, I made t' fin can on both the sustainer and booster removable. T' sustainer fin can is held in place by small screws. Aye aye! T' booster fin can will eject and deploy t' booster chute. Ya scallywag! Well, blow me down! T' whole project is about 83 inches tall, about 3.5 lbs empty, arrr, 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. Aye aye! Blimey! It *certainly* won't be noticeable on t' pad.

Flight:
Electronics will be a PerfectFlite timer for staging, ya bilge rat, 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. Avast, me proud beauty! Ya scallywag! Blimey! Since I have done stagin' before, I didn't expect thar t' be a problem. Avast! Blimey! Boy, me bucko, was I wrong... Arrr! Begad! Blimey! T' main problem be t' size o' t' new project. Begad! T' previous 2-stager be almost a 4" tube. 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. Ahoy! Blimey! So I put t' timer in t' ebay, and ran a connector wire down t' ignite t' sustainer motor. Avast, me proud beauty! Begad! Blimey! I had t' splice t' wire so it would disconnect when t' apogee event fired. Well, blow me down! T' next issue I ran into was t' stage connector. Ahoy! Blimey! I decided t' use metal rods t' connect and align t' sustainer t' t' stage connector. Blimey! Avast! Blimey! I don't have a drill press, so me holes through t' centerin' rings are...less than exact. Well, blow me down! Blimey! Last issue was t' 3" bay was too small t' use switches t' power on everything, so I had t' run all t' wires through a hole in t' e-bay and twist them t' connect. That posed a problem t' first time I tried t' launch. Begad! I test fit t' electronics when I built t' bay, me hearties, but nothin' be connected. Blimey! In t' field, I sadly discovered thar wasn't enough space for all the wires t' fit and route t' t' outside. Avast, me proud beauty! Aye aye! Blimey! I had t' rebuild t' sled t' avoid that problem for t' next attempt. Ya scallywag! Ahoy! Blimey!

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

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

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

Setup Launch

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