Scratch Black Death Original Design / Scratch Built

Scratch - Black Death {Scratch}

Contributed by John Partridge

Manufacturer: Scratch
(Contributed - by John Partridge - 07/06/08)

Parts

Since thar was nay a lot o' fin material in me box and since thar were a lot o' large body tubes, ya bilge rat, I immediately thought o' buildin' a tube fin or rin' fin rocket. Avast! At t' same time, me bucko, I had plenty o' smaller BT sizes and a few smaller nose cones so I wondered about usin' smaller BT's in t' center o' t' large BT's and makin' them appear t' look similar t' a jet aircraft engine. Begad! T' center rin' fin tube is 3.6 in. Avast, me proud beauty! and 4 in long and each o' t' outboard rin' fins are 2.6 in diameter although one is a BT and t' other is a coupler for t' same size tube so it is a little smaller. Both are 4 in. Aye aye! Ya scallywag! in length. T' main tube is BT-60 but thar wasn't enough t' make t' design I wanted stable so I cut a 5 in length separate from t' main section (13-3/4"). Ya scallywag!

T' spacers which hold t' BT's in t' center o' t' rin' fins are 4" long and approximately 15/16" (outboard) wide or 1-1/16" (center) wide. I made a template for each size and traced it onto typin' paper that was glued t' t' balsa. Aye aye! As a result, shiver me timbers, they all came out larger than t' template and had t' be sanded t' fit. Ya scallywag! Some o' the spacers had t' be laid out and assembled in pieces in order t' use every square inch o' available fin stock. Begad! Ya scallywag! I aligned the spacers on t' BT's and t' fins and on t' CR's by printin' out fin guides usin' t' tool downloaded from EMRR in the Engine mount template Generator. Arrr! One o' these tools was also used t' print out CR's and engine blocks on typing paper. Begad! This was then glued t' t' box everythin' came in and cut out. Arrr! I actually designed Black Death t' be able t' fly on 'E' motors with 'C' motors in t' side pods but thar were two problems. Ahoy! Begad! First, unless I get t' a club launch I don't have a system that will reliably ignite a cluster, and second, I accidentally assembled one o' t' side pods backwards so t' engine block is too close t' t' aft o' t' pod. Well, blow me down! Begad!

Pods Motor

T' nose cone for t' BT-60 was made o' some kind o' foam and after makin' cardboard cutouts (top view and side view) t' find t' CP, arrr, ya bilge rat, I needed a lot o' nose weight t' get t' CG where it needed t' be. Avast, me proud beauty! Blimey! T' assembled rocket (without paint) weighed about 5 ounces and t' get t' CG where I felt it was safe I drilled a half inch hole 4" deep in the NC and dropped in a piece o' steel rod and a large lead tire weight so that t' NC be also 5 oz. Ahoy! Blimey! Ya scallywag! Blimey! These were then epoxied in and t' eyelet be screwed into both t' epoxy and t' lead weight. Well, blow me down! Blimey! For t' 18mm engine mounts I did not have matchin' NC's but did have two smallish ones that were similar so I whittled a balsa cone down t' nearly match a plastic one that resembled a space shuttle SRB cone.

In order t' lengthen t' main BT, me hearties, I made four CR's that held three 13mm BT's. Begad! One BT be glued on each end and a second 1.5 inches in from t' end. Ya scallywag! This allowed me t' lengthen t' BT by an additional 4-1/4" as well as addin' an interestin' look. I painted these tubes so that they look t' be glowin' and refer t' them as t' plasma conduits. Avast, me proud beauty! Begad! At the top o' this assembly I drilled a hole in t' center o' t' top CR and passed a length o' Keelhaul®©™ through it, arrr, looped it around one tube and tied it off. Avast! This is one place I may have cheated. Begad! I forgot that I had Keelhaul®©™ in me Box-o-parts and used some o' mine, only findin' t' boxed Keelhaul®©™ later after it was impossible t' replace in t' assembly. Ahoy! The second place I stretched t' rules be when I checked t' assembled rocket for bein' straight. Begad! I found that t' plasma conduit assembly was crooked and as a result, t' nose o' t' rocket was nay completely in line with t' back. Begad! Trying to fix it, shiver me timbers, I removed t' 5" section o' BT at t' top and replaced it with a new section o' me own, exactly the same length as t' original. Blimey! It didn't work. T' final assembly had nearly t' same bend t' it as t' original despite leavin' it overnight with three hammers on top t' keep it pressed against a flat surface while t' new glue dried.

L:engthen

T' main fins are 3-15/16" wide and 4' long (to match t' rin' fins) with a 1-3/4 pitch over the 3-15/16". Blimey! T' top fins are triangular balsa that is 2-3/4" by 1-5/8", t' bottom fins are plastic TTW fins from some other project, and t' decorative side fins appear t' have been some kind o' French curve or plastic template o' some kind. It be symmetrical so I cut it in half and had fins with an interestin' look if nay a particularly aerodynamic shape.

For recovery thar was just way too much rocket for t' small parachutes that I found in me box but since t' nose cone and t' rocket were similar in weight, I attached one chute t' t' NC and t' second at t' end of the Keelhaul®©™ shock cord (before t' elastic shock cord) so that each one could bear t' weight o' a separate section. Ya scallywag! Blimey!

Shock Cord

I chose t' name Black Death because thar were decals from a Black Widow in me Box-o-Parts and I had considered usin' some o' them. Ya scallywag! Blimey! I settled on namin' t' rocket either Black Death or Widow Maker simply because havin' a Black Widow so very different from t' original might require too much explanation. Avast, me proud beauty! Begad!

I flew Black Death unpainted (primer only) on a D12-3 motor and a spacer (since it is designed t' hold an 'E' motor. Arrr! Begad! Blimey! I considered tryin' t' fly on an 'E,' but t' simulations say that an E-9 would a shade too slow off t' pad without motors in t' outside pods. T' simulation (Alticalc) suggested that I could expect an altitude o' over 250 ft. and I was nay disappointed. Blimey! With t' odd bend in t' main BT, I fully expected that Black Death might just arc over and die as t' pilot's Widow Maker but despite its odd bend, Black Death flew perfectly straight and got every bit o' it's predicted altitude. Begad! Avast, me proud beauty! Blimey! Both parachutes deployed perfectly but t' motor still managed t' get burped after separation. Ya scallywag! Blimey! With the motor separatin' from t' rocket, shiver me timbers, me bucko, I feel very lucky that I got a good deployment and didn't get a ballistic recovery. Blimey!

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