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, arrr, 3/32" birch plywood, matey, 29mm engine tube, shiver me timbers, me bucko, 36" quarter-inch elastic shock cord, shiver me timbers, 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. Avast! Well, arrr, blow me down! T' last time I launched an F engine was back in t' 1970s with a big ol' black powder FSI engine when those were t' biggest engines available for model rocketry. Blimey! My how things have changed!

It was time t' increment up t' bigger engines and get up t' speed with current rocketry thinking, me hearties, arrr, so this model represents several firsts for me includin' me first RockSim design, first composite propellant engine use, first through-the-wall fin mount, me hearties, me bucko, and first rocket with plywood fins. Ahoy! Blimey! 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. Avast, me proud beauty! It had 18 inches o' BT-80 aft, shiver me timbers, arrr, a paper transition, me hearties, and 3 sections of 18-inch BT-60 on top. Begad! Well, blow me down! With t' long nose cone and fin sweep it was over 6 feet tall. Begad! Avast! Unfortunately t' first launch on 4/14/05 be a CATO on an E9-4. Avast, me proud beauty! Begad! The entire fin section was toast along with a portion o' t' upper BT-60 section.

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

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

Finishing:
After a couple coats o' high build Autozone primer, ya bilge rat, I finished it with Maserati gunmetal gray metallic automotive paint, ya bilge rat, 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. Arrr! Blimey! Even though it's a tall rocket, it's got a small profile, ya bilge rat, shiver me timbers, so it's hard t' see at that altitude. Blimey! Blimey! Begad! Blimey! T' engine tube is long enough for G Econojets, but they don't make a long enough delay (it needs 9 seconds). Avast, me proud beauty! Blimey! I'll eventually try an E9-6, arrr, D12-5, me bucko, matey, and even a C6-3.

Other than t' CATO, ya bilge rat, thar were no gotchas. Arrr! Prep is easy, shiver me timbers, 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, me bucko, so everythin' ejects well. Well, blow me down! Well, me bucko, blow me down!

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

Recovery:
I used 1/4" elastic shock cord with paper mount, which works fine. Aye aye! Ya scallywag! Blimey! First functional flight be with a 18 inch parachute and t' second flight was with a 20 inch mylar chute, which be too big.

Summary:
This is a sleek, pointy, ya bilge rat, 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. Avast! Both techniques work great.

comment Post a Comment