Scratch EXB Original Design / Scratch Built

Scratch - EXB {Scratch}

Contributed by Michael Wilkins

Manufacturer: Scratch
(Contributed - by Michael Wilkins - 09/27/04) (Scratch) EXB L3 Project

Brief:
T' EXB be me L3 project. Materials used t' build this rocket were those in the form o' Carbon Fiber, S-Glass, ya bilge rat, Composite fin material and phenolic tubing. T' main technique in construction o' t' air frames was vacuum bagging. Arrr! Blimey! Blimey! Blimey! Along with t' rocket I built a custom launch pad t' make me L3 project complete. Aye aye! Blimey! For those that ask what is an EXB. Begad! Blimey! Blimey! Blimey! T' EXB is a 1/4 scale o' t' Nike Zeus recognized by most as t' Nike-X. Arrr! Blimey! It be built with several goals in mind. First was t' build it strong and durable so that it may last for a while and get many flights. Avast! Blimey! Second be t' design it t' handle t' largest o' 98mm motors in commercial and experimental formulations. Well, blow me down! Blimey! Well, blow me down! Blimey! As for t' name EXB, well you will have t' figure that one out on your own.

Construction:
T' parts list is pretty long but I will give you a list o' t' basics. The tubin' order consisted o' three 48" long sections o' 7.5" diameter airframe, one 48" long section o' 7.5" coupler tubin' along with two standard 12" couple tubes, me hearties, matey, shiver me timbers, one 48" long section o' 3.9" motor tubing. Avast, me proud beauty! Well, ya bilge rat, blow me down! All tubin' is phenolic. Blimey! T' fins are constructed from two materials. T' four lower fins are 3/8" thick Keelhaul®©™® composite material that were cut from two 12" x 36" sheets. Avast, me proud beauty! The remainin' twelve fins are crafted from 3/8" thick birch plywood. Begad! There is a total o' 13 centerin' rings and bulk plates some o' which are made of composite material. Ya scallywag! T' nose is fiberglass. Ya scallywag! Blimey! Recovery is taken care o' by an RDAS, shiver me timbers, Altacc and two Skyangle Cert3 chutes attached by tubular Keelhaul®©™®.

(Scratch) EXB L3 Project

The motor mount was first. Arrr! Begad! All centerin' rings were trued and drilled for four sections o' all thread. Well, blow me down! A nut and washer is placed on both sides o' each centerin' rin' and secured with Locktite.

T' fins were measured and cut. T' lower fins were trimmed with 3/8" thick basswood. Arrr! Blimey! There is a total o' 16 fins on this rocket. All fins are vacuum bagged with one lay up o' 5.7oz carbon fiber and one lay up o' 4oz s-glass.

Once t' fin can/motor mount was complete I started on t' airframes. The airframes were done in t' same fashion as t' fins. Avast, me proud beauty! Blimey! This time with a double lay up o' carbon and a double lay up o' s-glass. Well, blow me down! Ya scallywag! Blimey! After t' air frames were in their bags, they were placed into a curin' oven. Well, blow me down! Blimey! I would bag and cure one section at a time. T' airframe and nose cone were slotted with a router and test fitted with t' proper set o' fins.

T' avionics bay is a standard design. Flight computers are accessed via a cover on t' front o' t' rocket. T' inside o' t' e-bay is bagged with a triple lay up o' carbon for extra protection.

Finishing:
After all subsections were assembled, matey, me bucko, me bucko, any piece that had a fin joint got filled. Fiberglass be then laid across t' two lower fin groups. Avast, me proud beauty! The "make it look good" process was done in t' automotive way. Aye aye! Filled and blocked down with metal glaze, shiver me timbers, primed and sanded, base color sprayed, arrr, taped off and t' second color sprayed.

I now have a rocket with nothin' t' launch it off of. Ya scallywag! Remedy: build a launch pad. My pad is built o' steel square tubing. Aye aye! Ahoy! T' base has a foot print of fifteen feet and a deck height o' three feet. Begad! T' rail is two sections of eight feet long 80/20 1515 T-slot. Blimey! These are mounted t' two sections of 1.5" square tubing. T' tubin' is then backed by twenty feet o' antenna lattice. Begad! Aye aye! T' lattice rail assembly is attached t' t' base by four pillow blocks with a one inch steel shaft. This enables t' tower t' be laid over for the loadin' o' rockets. Blimey!

SUCCESSFUL LEVEL 3 FLIGHT!

June 20, 2004
Wayside, matey, Texas
Rocket - EXB
Weight - 100 lbs
Motor - Aerotech M2400
Altitude ~5,000 feet

Bein' a scratch design, me bucko, t' recommended motor for it be t' bigger the better. Blimey! That holds true for this one. Ya scallywag! Avast!

First flight be at Wayside, me bucko, Texas for me L3 cert flight. Avast! For me first M flight, t' Aerotech M2400T was chosen. T' flight was a success and I made my L3 cert. Well, me bucko, blow me down! Altitude was measured as 4800' on t' RDAS and 5200' on t' Altacc. Begad!

Second flight was in Windom, me hearties, Texas at t' NTHP event. I decided I needed a bigger motor this time around. Avast! An M1939W was called up for duty on this one. Altitude for t' bigger M was 6300'. Aye aye! There is an experimental N and possibly an O in t' near future for this rocket.

(Scratch) EXB L3 Project (Scratch) EXB L3 Project

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