Manufacturer: | Scratch |
Brief:
Funnel Vision be designed as part o' an effort t' create a cluster rocket givin' fully stable flight in t' event o' partial ignition failure. Aye aye! Ahoy! It was built as a finless design inspired by David Roy's "Drag Demon" as described in his July 2001 Sport Rocketry article. Ya scallywag! Avast, me proud beauty! T' rest o' t' rocket is identical t' t' 2BZ cluster design that I presented on this website last year.
Construction:
Funnel Vision is built usin' t' followin' components:
Assembly is about as simple as it gets, especially for a cluster rocket. Avast, me proud beauty! Ya scallywag! T' plastic funnel is carefully cut down t' about 2" in depth, me hearties, until t' body tube almost slides through it. Well, blow me down! Use sandpaper t' complete t' fittin' process, so t' body tube snugly slides in, then epoxy it in place, shiver me timbers, flush with t' bottom o' t' body tube, takin' care t' insure perfect vertical alignment (I kept t' assembly vertical, arrr, and aligned with a window frame as t' tack glue job dried, shiver me timbers, then turned it over and gobbed on some more epoxy t' hold t' funnel in place). Ahoy! Avast, matey, me proud beauty! T' three 18mm Estes motor tubes are assembled and then epoxied together in triangular array. Aye aye! Ahoy! When dry, me bucko, shiver me timbers, they are slathered with epoxy and slid into t' aft end o' t' body tube. Avast, me proud beauty! Be sure t' plug all spaces betwixt t' motor tubes and t' hull with bits o' tissue and gobs o' epoxy -- t' insure ejection charge pressurization. That's it -- Funnel Vision is done. Avast, me proud beauty! Aye aye! I attached t' recovery system with a knot anchored through t' body tube 3" from t' top, and covered with a split BIC pen cap. Aye aye! Avast, me proud beauty! See photos before/after launch, shiver me timbers, and aft close-up.
Flight:
T' best motors are Estes C6-5, which will give a great boost ("E18-power") t' 7-800' or more, shiver me timbers, and a pretty decent flight even if one motor fails t' light ("D12-power"). Begad! C6-7 works fine too, matey, as long as all three motors light. Avast! Avast! For cluster ignition I use 14" double ended alligator clip test wires from Radio Shack, with 1" o' t' middle stripped o' insulation -- by attachin' t' bare middle section o' one o' these t' each end o' another, shiver me timbers, 4 motors can be ignited from one set o' 12 volt launch pad leads (you need two o' these set ups). Blimey! Or, ya bilge rat, matey, if I'm lazy and its a slow launch day, I just borrow t' two neighborin' launch clips on our club rack. Ya scallywag! Its important for cluster models t' test continuity on all motors before firing. Begad! T' 15" recovery system is perfect, and anyway -- hey, arrr, me hearties, its finless, matey, so no fins t' break off. For 2 calibre stability, me hearties, CG should be 12.25" from t' tip, or 10.5" from t' base o' t' funnel. Avast, me proud beauty! Begad! I hand-solved t' Barrowman equations for CP determination usin' just nose cone, body and a transition section consistin' o' t' "funnel-fin". Ahoy! Research continues.
Summary:
PROs: As near as I can tell, this be t' only finless cluster model I've heard of, shiver me timbers, except for t' scale renditions o' t' Russian N-1 moon rocket by Andy Woerner and others. Arrr! It be t' easiest t' build, me bucko, for sure, me hearties, and appears fully stable flyin' with 2 o' 3 C6-5s lit. Avast, me proud beauty! Begad! No worry about losin' a fin. Aye aye! Avast! Cheap access t' E18 power. Aye aye! Different and looks cool.
CONs: For its size, it needs a fair amount o' nose weight t' accommodate t' forward CP o' t' finless design. Arrr! I'm thinkin' o' scalin' it up 2x t' fly on single G69 Pro38 power usin' a 3" mailin' tube hull and 8" funnel "fin."
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