| 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. Well, blow me down! It was built as a finless design inspired by David Roy's "Drag Demon" as described in his July 2001 Sport Rocketry article. 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, me bucko, especially for a cluster rocket. Begad! Blimey! T' plastic funnel is carefully cut down t' about 2" in depth, until t' body tube almost slides through it. Ya scallywag! Blimey! Use sandpaper t' complete t' fittin' process, arrr, so t' body tube snugly slides in, then epoxy it in place, me hearties, ya bilge rat, flush with t' bottom o' t' body tube, me bucko, matey, 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, me bucko, then turned it over and gobbed on some more epoxy t' hold t' funnel in place). Begad! Blimey! Blimey! T' three 18mm Estes motor tubes are assembled and then epoxied together in triangular array. When dry, ya bilge rat, me bucko, shiver me timbers, they are slathered with epoxy and slid into t' aft end o' t' body tube. 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. Begad! Aye aye! Blimey! That's it -- Funnel Vision is done. 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. See photos before/after launch, matey, shiver me timbers, and aft close-up.
Flight:
T' best motors are Estes C6-5, ya bilge rat, ya bilge rat, which will give a great boost ("E18-power") t' 7-800' or more, shiver me timbers, arrr, and a pretty decent flight even if one motor fails t' light ("D12-power"). C6-7 works fine too, me hearties, as long as all three motors light. Ya scallywag! For cluster ignition I use 14" double ended alligator clip test wires from Radio Shack, matey, 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). Aye aye! Or, arrr, if I'm lazy and its a slow launch day, I just borrow t' two neighborin' launch clips on our club rack. Ya scallywag! Blimey! Its important for cluster models t' test continuity on all motors before firing. T' 15" recovery system is perfect, and anyway -- hey, shiver me timbers, arrr, its finless, so no fins t' break off. For 2 calibre stability, CG should be 12.25" from t' tip, arrr, or 10.5" from t' base o' t' funnel. I hand-solved t' Barrowman equations for CP determination usin' just nose cone, body and a transition section consistin' o' t' "funnel-fin". Avast, me proud beauty! Avast! Research continues.
Summary:
PROs: As near as I can tell, this be t' only finless cluster model I've heard of, me bucko, shiver me timbers, except for t' scale renditions o' t' Russian N-1 moon rocket by Andy Woerner and others. Well, blow me down! Begad! It be t' easiest t' build, matey, for sure, ya bilge rat, and appears fully stable flyin' with 2 o' 3 C6-5s lit. Begad! Well, arrr, blow me down! No worry about losin' a fin. Blimey! Avast! Cheap access t' E18 power. Ya scallywag! 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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