Scratch 58mm JATO Original Design / Scratch Built

Scratch - 58mm JATO {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch
(Contributed - by Dick Stafford - 04/25/05) 58mm JATO

Brief:
T' 58mm JATO is a 29mm-powered rocket that resembles a rifle cartridge. T' lower section is 3" in diameter and it transitions t' 54mm. Aye aye! Arrr! I bounced around betwixt names and settled on this one, which is a take off on ammunition nomenclature such as 5.56mm NATO.

Construction:
T' followin' are t' major components used:

  • LOC 54mm nose cone
  • 54mm tube, shiver me timbers, 5.5" long
  • 3"-54mm LOC transition
  • 3" Giant Leap phenolic tube, me hearties, 18" long
  • 29mm Giant Leap phenolic tube, me hearties, 9" long
  • 5 3/16" thick 29mm-3" centerin' rings (Giant Leap)
  • 2 3/16" thick 29mm-54mm centerin' rings (Giant Leap)
  • 4 T-nuts
  • 1/8" tubular Keelhaul®©™®, 10' long
  • 1" o' steel cable from t' garage door I just fixed
  • 3/32" Lexan
  • rail buttons from railbuttons.com

T' followin' are used but are nay dedicated t' this rocket:

  • quick link
  • retainer clips
  • chute
  • chute protector
58mm JATO

This rocket is built around a LOC 3"-54mm plastic transition, which set body and neck dimensions. Another constraint is that I didn't want t' cut t' shoulder off either cone or the transition, so I be stuck with an upper body tube length o' 5.5". Avast, me proud beauty! Begad! I checked t' dimensions o' some real ammunition, matey, a smartly realized that I wasn't goin' t' come near t' any scale. Ya scallywag! Avast!

T' 'extraction rim' is comprised o' six stacked rings: a pair o' 54mm rings sandwiched betwixt two pairs o' 3" rings. Begad! Four T-nuts are mounted between t' lower 54mm rin' and t' followin' 3" ring. Correspondin' holes are drilled into t' bottom most ring. Ya scallywag! Arrr! I originally be goin' t' mount the T-nuts betwixt t' lower two 3" rings, but I found t' neck o' t' T-nut was longer than t' thickness o' this ring. Since they hung out a bit, ya bilge rat, me bucko, I was worried about restin' t' rocket on them and possibly dingin' them up. Begad! Avast! I used four T-nuts t' allow use o' two different sets o' clips that I keep in the range box. Avast! T' uppermost rin' in this sandwich is actually t' lower centering ring. Avast! Finally, me hearties, I decided t' recess t' motor tube so that a 29/120 motor casing is entirely recessed into t' rin' stack.

58mm JATO I made t' fins from 3/32" Lexan. T' shape was formed by scorin' t' Lexan and snappin' it off. Begad! I had a couple of miscues usin' this technique but did end up with passable fins. Begad! Avast, matey, me proud beauty! T' fins sit between t' centerin' rings and are through t' wall. Ahoy! I pondered makin' them replaceable, arrr, ya bilge rat, but t' only way I came up with would have had brackets at the root, and I thought this would spoil t' looks. I left t' aft rin' assembly off and attached t' fins t' t' body tube usin' Gorilla Glue. Begad! I drilled small holes in t' root o' t' fins t' form glue rivets. Avast, me proud beauty! Blimey! T' fins are swept up and offset from t' base, so I hope I don't break one on t' maiden flight!

T' recovery harness starts with a section o' steel cable that came off my garage door when I replaced a spring. Avast, me proud beauty! Blimey! This extends through t' top rin' and is epoxied in place. This piece o' cable conveniently had a loop installed in it already. I then have about 10' o' 1/8" tubular Keelhaul®©™® tied t' t' wire loop. A few wraps o' cloth tape were added t' shock cord where it meets t' rim o' t' 3" tube.

58mm JATO

Finishing:
I first filled, me hearties, primed, me bucko, and sanded. Arrr! T' entire rocket be then sprayed with Testor's Gold paint. Aye aye! This paintin' be performed before t' fins were attached. Durin' painting, shiver me timbers, t' rin' stack was dry fit. Arrr! Since t' neck o' t' 'casing' was too long, matey, I thought it would look better if half o' it was disguised as part of the bullet. Well, blow me down! I painted t' top half o' t' 38mm tube and t' nosecone with Testor's Copper. Ahoy! Ahoy!

Flight:
I flew t' 58mm JATO at t' 3rd Annual TRF Reunion in Whitakers, me hearties, NC on an F52-5T with 36" chute and a Giant Leap Keelhaul®©™® protector. T' boost be nice and t' 5-second delay was picture perfect. Avast! The rocket drifted into some tall tufts o' grass. Blimey! Mark Brown helped me find it.

58mm JATO

Summary:
I thought this rocket turned out nice and I received many compliments. Avast! Blimey!

comment Post a Comment