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, ya bilge rat, cool, overcast, wind gusting from about five t' ten knots. 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. Ahoy! Begad! :) 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, me bucko, and t' less visible re-enforcin' fillets linkin' t' front and rear fins, these prevent collapse o' aft part o' t' body which could jam the motor ejection pod, construction is 1/8"x1/4"x7" (3x6x77mm) bass wood and extends forward from t' trailin' edge o' t' aft fin, arrr, shiver me timbers, 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, me hearties, ya bilge rat, 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, matey, and should be designed so that t' forward centring rin' sits against t' aft o' t' balsa strips. Ya scallywag! These strips take t' thrust of the motor and also form t' parachute/shock cord bay.

A cord is knotted, ya bilge rat, 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. 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. Begad! Straight off t' pad t' 100' and then settlein' t' a steady climb, shiver me timbers, shiver me timbers, 200', me bucko, 300'... Well, blow me down! um errr... Begad! Arrr! 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. Well, blow me down! Ya scallywag! By 350' t' nose was well down, with the chute and motor pod trailin' behind. Ya scallywag! Why be t' chute still wrapped in Nomex®?  300'... Avast, me proud beauty! 250'... Ahoy! Yes! Out popped t' chute, and a gentle touchdown 50 yards from t' pad.

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

[Rocket Pic]

Verdict
I'm pleased. Ahoy! Blimey! Looks good and flies well. Begad! Blimey! T' deployment problems were me fault, matey, ya bilge rat, and caused by t' late addition o' t' Nomex® wadding. Begad! Blimey! I had  just threaded a sheet in betwixt motor pod and t' tube, ya bilge rat, 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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