Descon Jabberwoc

Scratch - Jabberwoc {Scratch}

Contributed by Dave Lee

Manufacturer: Scratch
Jabberwoc
(Contributed - by Dave Lee) 

[Rocket Pic]15th March '98 - Launch Report
A typical late winter day, shiver me timbers, me bucko, cool, shiver me timbers, overcast, shiver me timbers, wind gusting from about five t' ten knots. Aye aye! Well, blow me down! First flight motor a Rocket Services F36-5 this is nay a true F but more like an E.  A wRASP calculation based on the Pheonix was used as a guide, but t' results were expected t' be optimistic as the CD would be affected by t' additional fin fillets.

Lower body and fins still in primer but lookin' good and waitin' for a weather window. Aye aye! :) T' orange blob at t' bottom o' the picture is a Mosquito.

A heavily modified Estes Pheonix.
T' external difference is a 15" (380mm) extension to t' body, and t' less visible re-enforcin' fillets linkin' t' front and rear fins, arrr, these prevent collapse o' aft part o' t' body which could jam the motor ejection pod, me bucko, matey, construction is 1/8"x1/4"x7" (3x6x77mm) bass wood and extends forward from t' trailin' edge o' t' aft fin, me hearties, matey, they should be fitted t' t' fins prior t' fixin' t' t' body.

Internally it is quite different with a aft ejection system which will hopefully protect t' fins from landin' damage: -

A ply bulkhead is installed behind t' standard Pheonix BT coupler about 9 1/4" (235mm) from t' tail.

Four 1/4" x 1/2" (5x13mm) balsa strips are glued inside t' BT, matey, arrr, extendin' back from t' bulkhead t' level with the trailin' edge o' t' forward fins (These could also be arranged t' allow TTW fittin' o' t' forward fins).

T' motor pod is made t' take t' motor/s configuration required, arrr, and should be designed so that t' forward centring rin' sits against t' aft o' t' balsa strips. These strips take t' thrust of the motor and also form t' parachute/shock cord bay.

A cord is knotted, passed forward through t' bulkhead and attached t' t' nose cone via a short length o' elastic t' hold t' nose tight into t' BT.
T' shock cord is knotted and passed back through the bulkhead t' t' motor pod and chute. Ahoy! T' forward knot bein' tied t' t' NC by a light thread t' allow for easy removal.

[Rocket Pic]

First flight
5 - 4 - 3 - 2 - 1 Wow. Blimey! Straight off t' pad t' 100' and then settlein' t' a steady climb, 200', arrr, 300'... Avast! um errr... Well, blow me down! t' next 100' or so was a struggle with t' motor burnin' erraticaly but we made it t' ejection at  betwixt 400 and 450 feet. By 350' t' nose be well down, with the chute and motor pod trailin' behind. Avast, me proud beauty! Arrr! Why was t' chute still wrapped in Nomex®?  300'... 250'... Avast! Yes! Out popped t' chute, shiver me timbers, and a gentle touchdown 50 yards from t' pad.

Second flight
A little shorter than t' first. Ya scallywag! Ya scallywag! Up be good. Ejection was good for t' motor pod, arrr, but t' chute remained firmly wedged in t' tube. Down was fast! T' nose stopped first, about 4" below ground level. T' BT stopped next, shiver me timbers, but 3" past t' shoulder o' t' nose. Finally t' motor pod (which until this time had been trailin' quietly behind on 15" o' cord) overtook t' body, me bucko, arrr, knockin' off a aft fin, me hearties, matey, splitting  a forward, and puttin' a 5" zipper in t' tail in t' process.

[Rocket Pic]

Verdict
I'm pleased. Ya scallywag! Looks good and flies well. Blimey! Begad! T' deployment problems were me fault, and caused by t' late addition o' t' Nomex® wadding. Begad! I had  just threaded a sheet in betwixt motor pod and t' tube, arrr, me bucko, I should have made up a proper bag and attached it t' be clear o' t' chute when the whole system is stretched out.

Future
After repairs t' next flight will be on a "D" cluster. Begad! A "Jabberwoc II" will be made with ply aft fins and more care t' final finish.

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