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

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

There are holes in both centerin' rings that are supposed t' be aligned. Ya scallywag! 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. Avast! T' sustainer fin can is held in place by small screws. Begad! Aye aye! T' booster fin can will eject and deploy t' booster chute. T' whole project is about 83 inches tall, me bucko, 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, shiver me timbers, but once it's painted it might nay be that noticeable. Begad! It *certainly* won't be noticeable on t' pad.

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

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

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

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

Setup Launch

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