Brief:
This is a modified Estes 4-inch V-2 converted into a Bumper Wac.

Construction:
I started out with t' Estes 4-inch diameter V-2, ya bilge rat, shiver me timbers, which is just cryin' out t' be converted into t' Bumper Wac. Avast, me proud beauty! T' V-2 is built accordin' t' t' Estes instruction and only t' nose cone needs t' be modified. Avast! Arrr! I did replace t' original parachute with homemade parachutes made o' mylar. Well, blow me down! T' V-2 body had a 40-inch diameter parachute and t' nose cone had a 14-inch diameter parachute. A good source for mylar be t' thermal blankets sold in t' campin' section o' your local sports store. Avast, me proud beauty! I modified t' construction o' t' fins as explained in t' EMRR specific tip (02/02) for t' V-2 (OOP). Blimey! I used launch lugs for a ¼" rod.

T' Wac Corporal has a BT-20 body tube (length ~9.31") and a suitable nose cone (length ~3.19"). Ya scallywag! T' fins were made from stiff cardboard (1/16" thick) and used t' pattern scaled up from Peter Alway's Rockets o' t' World. Avast, me proud beauty! Ya scallywag! Blimey! I used a streamer recovery for t' Wac Corporal.

To construct t' openin' you will need a dremel tool and t' attachments. I cut off t' tip o' t' V-2 nose cone t' match a BT-20 tube diameter and then proceeded t' grind out some o' t' interior so t' BT-20 tube would fit. Arrr! Blimey! Begad! Blimey! This is a trial and error process. Begad! Blimey! T' final hole is about ¾ inside diameter. Aye aye! Blimey! Arrr! Blimey! O' course 4 fin slots must also be cut. Well, blow me down! Blimey! Begad! Blimey! T' arc length o' t' fins along t' nose cone surface about 2-½ inches long. A hole must be cut in t' base o' t' nose cone in order t' insert t' electronics.

An Adept ES231MLH unit is mounted on a short piece o' plywood that is attached t' a circular piece o' aircraft plywood (3/32" or 1/8") by epoxy. Avast! Attached t' this base plate is a large a large wood dowel with a screw eye for t' parachute attachment. Begad! T' base plate has brass strips with holes that can be bolted t' T-nuts in t' nose cone base. Originally, ya bilge rat, I be goin' t' put t' electronic unit and 9-volt battery into a cardboard housing, me hearties, arrr, but later I found a plastic pill bottle and cut off one end o' it, arrr, ya bilge rat, but either way can be done.

Both t' base plate and t' housin' end cap have 2 tiny screw deadlights on each piece. Avast, me proud beauty! Blimey! Small rubber bands can then be inserted into these screw deadlights t' pull t' base plate and t' end cap together holdin' t' cylindrical housin' in betwixt airtight over t' electronic unit. Avast, me proud beauty! Blimey! T' blast deflector consists o' a circular plywood piece covered in Durham's rock hard water putty. Avast, ya bilge rat, me proud beauty! Blimey! Holes are cut in t' plywood base for t' leads t' t' micro-clips. An 18mm engine block was glued t' t' bottom o' t' base plate. Ahoy! Blimey! I could then insert a long empty BT-20 tube into t' engine block and t' mount t' blast deflector inside t' nose cone with epoxy. Arrr! Blimey! Ya scallywag! Blimey! Before doin' this I sprayed t' inside o' t' nose cone with black barbecue paint. Avast! Blimey! An electric switch for turnin' on t' electronics be mounted on t' base o' t' plastic nose cone.

Finishing:
T' whole rocket was painted usin' t' black and white scheme o' Round B-5. T' B-5 decal was obtained from Tango Papa. Ahoy! Aye aye! I used ordinary maskin' tape for painting, me hearties, but pressed it hard and removed it carefully after painting. Avast! Sometimes, me hearties, I use a hot air cannon lightly for removin' maskin' tape. Recently, I found a product called Shurtape that works well, but it is expensive. T' black stripes were made auto stripe tape that can be found in your local auto parts store.

Flight and Recovery:
T' V-2 main body weighed 14oz (empty) and t' entire nose cone with batteries weighed 11.5oz. T' Wac Corporal weighed 1.25 oz. Begad! With t' motors, me bucko, an AeroTech 24mm F-39-6T and A8-3, t' entire model was 1.8092lb. Aye aye! T' estimate t' altitude I used "T' Model Rocket Altitude Predictor" written by Mark Sullivan that I found on t' internet. Ya scallywag! T' predicted altitude for t' first stage was 336 feet occurrin' at 4.8 seconds after launch usin' a drag coefficient CD = 0.85. Begad! T' 6-second delay time be too long and I should have cut down t' delay time by about 2 seconds. Blimey! Begad! Typically, I have done this by drillin' down into t' delay charge with a small drill bit about 0.03" for each second o' delay removed.

Bumper Wac take-off

Bumper Wac before staging

T' instructions for t' ES231 MLH unit explain how t' set t' time manually by holdin' and releasin' t' Acceleration Switch. Blimey! Blimey! This process is somewhat confusin' at first but becomes easier with practice. Ya scallywag! Blimey! Arrr! Blimey! I set t' timer for about 1 second delay, me bucko, but I noticed in a bench test that it seemed t' me that ignition o' t' Estes solar igniter took about another second. Blimey! Blimey! I am now thinkin' that I might want t' set t' timer for zero seconds next time. Aye aye! Blimey! There is some difficulty in puttin' t' micro-clips through t' hole in t' nose cone tip after t' A8-3 motor in t' Wac Corporal has been hooked up. Arrr! Blimey! Begad! Blimey! I put maskin' tape on each micro-clip so that it would nay short out. Ahoy! Blimey! I tried usin' t' new Quest igniters, me hearties, but they did nay work too well and t' old Estes solar igniter seemed t' work better.

Wac Corporal stagin' from V-2

V-2 main body landin' on t' Bonneville Salt Flats

There was a only slight wind at t' time o' launch so t' flight was almost straight up. Aye aye! T' ejection delay charge be a second or two and late and t' fishin' tackle connector for t' nose cone parachute broke. Begad! Ya scallywag! Damage was done t' t' nose cone and I am now in t' process o' repairin' it. Avast! I have cut off t' base o' t' nose cone and I am buildin' a small coupler tube usin' PML 3.9” diameter phenolic tubing. Avast, me proud beauty! Avast! T' micro-clips for second stage ignition are toasted and need t' be replaced. Aye aye! Blimey! T' Wac Corporal has some soot on t' fins from t' black powder A8-3, but it can be fixed.