Scratch Gunslinger Original Design / Scratch Built

Scratch - Gunslinger {Scratch}

Contributed by Jeff Lane

Manufacturer: Scratch
(Contributed - by Jeff Lane - 06/14/05)

Brief:
Tall scratch mid power rocket.

(Scratch) Gunslinger

Construction:
Materials: Magnum nose cone, 3 BT-60 tubes, 2 couplers, me hearties, 3/32" birch plywood, arrr, 29mm engine tube, shiver me timbers, 36" quarter-inch elastic shock cord, matey, 21" mylar parachute.

Sometime ago I found a 2-pack o' Aerotech F23-7 Econojet single use motors for $12.95 on clearance at Hobby Lobby so I snapped 'em up. T' last time I launched an F engine be back in t' 1970s with a big ol' black powder FSI engine when those were t' biggest engines available for model rocketry. My how things have changed!

It was time t' increment up t' bigger engines and get up t' speed with current rocketry thinking, so this model represents several firsts for me includin' me first RockSim design, me bucko, first composite propellant engine use, first through-the-wall fin mount, ya bilge rat, me bucko, and first rocket with plywood fins. Arrr! I also used two buildin' and flyin' tips from t' EMRR database which were new t' me.

T' first iteration o' this rocket was bigger and taller than what's shown in t' photo. Ahoy! It had 18 inches o' BT-80 aft, a paper transition, and 3 sections of 18-inch BT-60 on top. Aye aye! With t' long nose cone and fin sweep it be over 6 feet tall. Begad! Unfortunately t' first launch on 4/14/05 was a CATO on an E9-4. Blimey! Aye aye! The entire fin section be toast along with a portion o' t' upper BT-60 section. Avast!

I wound up with 39.125 inches o' body tube topped off by t' long, arrr, sleek 8.375 inch plastic nose cone originally from an Estes Magnum. Begad! Ya scallywag! With t' fins sweepin' back a little less than half an inch, me hearties, ya bilge rat, t' total length is 4 feet.

It's a pretty simple build. Aye aye! Blimey! T' BT-60s were glued together with couplers, the fins were cut out with a razor saw, matey, t' slots for t' fins were cut with a hobby knife, arrr, and t' engine tube/block/ribs/centerin' rin' unit was glued in place with Elmer's followed by t' fins. Aye aye! Blimey! I love havin' t' fins glued t' the engine tube and t' body tube. It results in a much more sturdy assembly. Ahoy! Blimey! The 3/16" launch lug was offset .25" in case I want t' add a payload in the future. Blimey! Blimey!

Finishing:
After a couple coats o' high build Autozone primer, I finished it with Maserati gunmetal gray metallic automotive paint, some self-adhesive reflective holographic mylar, ya bilge rat, and a custom Lazertran waterslide decal/body wrap.

(Scratch) Gunslinger

Flight:
Rocksim predicts almost 2300 feet on an F23 and both F flights certainly looked that high. Ya scallywag! Even though it's a tall rocket, me hearties, it's got a small profile, so it's hard t' see at that altitude. Ya scallywag! T' engine tube is long enough for G Econojets, but they don't make a long enough delay (it needs 9 seconds). Aye aye! I'll eventually try an E9-6, D12-5, me hearties, and even a C6-3.

Other than t' CATO, thar were no gotchas. Begad! Blimey! Prep is easy, me hearties, me hearties, engine is friction fit (even though it's composite and heats up a lot, it works fine), and thar's plenty o' room for t' parachute and wadding, ya bilge rat, so everythin' ejects well. Begad! Blimey!

T' second launch (with t' shorter configuration) was on an F engine on an open range south o' Ellicott, me bucko, shiver me timbers, Colorado. Ya scallywag! Begad! You can see Pikes Peak in the background o' t' animated .GIF file. Well, blow me down! T' black smoke, altitude, me hearties, and quickness off t' pad were most impressive. Ahoy! As far away as it was, t' ejection charge was still a loud pop. Aye aye! A couple o' shroud lines broke but thar was no damage to the rocket. Begad! Third launch be at C.R.A.S.H. Aye aye! Begad! on 5/21/05. Aye aye! It had a barely discernable corkscrew, but t' mylar chute held up and it was a perfect flight.

Recovery:
I used 1/4" elastic shock cord with paper mount, which works fine. Avast, me proud beauty! Begad! First functional flight was with a 18 inch parachute and t' second flight was with a 20 inch mylar chute, which was too big.

Summary:
This is a sleek, shiver me timbers, pointy, me hearties, small-finned rocket that has people concerned about its stability until it disappears off t' pad.

Other:
T' two EMRR tips used: paint t' tip o' t' nosecone usin' a paper centerin' rin' as a mask and split t' end o' a Copperhead igniter with a flame t' use mini clips. Both techniques work great.

comment Post a Comment