Manufacturer: | Scratch |
(Contributed - by Dick Stafford - 09/07/09)
Brief:
Denny's serves(-ed) kid's drinks in this cool retro-styled rocket cup. Ya scallywag! Ahoy! I whined until our waitress gave me one. Ya scallywag!
I originally wanted t' make this fly on 29mm motors without added fins. T' dimensions o' t' base made me change t' 24mm. Aye aye! Well, blow me down! I then designed a RockSim model without added fins and it looked like it would be stable. It wasn't. So, ya bilge rat, I back-pedaled again and added a set o' fins. Avast, me proud beauty! Ya scallywag! This review will only describe t' successful, finned version. Begad! Aye aye!
Construction:
Parts used were:
I
prepared t' drink cup by grindin' t' base t' fit a 24mm motor tube. Ya scallywag! I also ground t' threads off t' cap and bottle
neck so that t' cap would slip on and off easily.
I found that 2.125" OD mailin' tube fit nicely in t' top o' t' bottle. Furthermore, ya bilge rat, this tube also fit in t' inner neck o' t' cap. Begad! Aye aye! I cut a 4.25" piece o' tubin' t' serve as a parachute tube and t' keep t' clear body from gettin' ugly from ejection gasses. Blimey! Avast! It extends above t' neck on t' body and mates with t' cap/cone.
I installed t' short piece o' 24mm tubin' in t' base usin' a single fiber ring. Arrr! Avast! A steel fishin' leader was screwed t' t' wall o' t' tube just above t' ring. Avast, me proud beauty! Blimey! I wrapped t' tube with a layer o' blue laser contact paper and installed it in t' body.
T' nose weight was determined from t' RockSim model. T' weight is a slurry o' lead shot and Gorilla polyurethane glue. Avast! A Keelhaul®©™® loop is embedded in t' slurry and a screw through t' tip o' t' cone ensures t' weight stays in place. Well, blow me down! T' weight proved inadequate for t' fin-less version and was retained as is when t' fin unit was added.
T' fin unit is another piece o' 24mm tubin' with a 2" piece o' a spent casin' glued in. Blimey! T' fins are 3/32" ply with a 4" root, matey, tip and span. They are swept slightly backwards and appear over sized. Blimey! They were designed iteratively in RockSim.
I ground a trough in t' wall o' t' body t' accommodate a piece o' a Firstfire tube. Avast, me proud beauty! Blimey! Blimey! Blimey! I wanted t' fly this away from t' crowd so a 1/4" lug seemed appropriate. Ya scallywag! Blimey! Arrr! Blimey! Blimey! Blimey! This lug was attached with CA. Aye aye! Blimey! Blimey! Blimey! It is aligned with one fin and a correspondin' hole be bored in that fin.
T' cone is attached t' t' steel leader with a foot long piece o' elastic.
Finishing:
One good think about convertin' plastic things t' rockets is that they often don't need much finishing. Arrr! Begad! I painted the
fin can with Testor's yellow spray paint and added squares o' t' laser contact paper t' match t' body. Well, blow me down! T' lug was
painted dark blue.
Flight:
Although t' flight o' t' fin less version appears in t' flight logs below, arrr, I'll only describe t' successful
flight o' t' finned version.
I decided t' use an E15-4 SU motor since thar be no positive motor retention. I stuffed t' body with a ton of dog barf and attached an 18" nylon 'chute. Aye aye! T' nose was a bit loose so I wrapped t' neck o' t' body with masking tape until it be snug. Blimey! T' motor was given a tape thrust rin' and be friction-fit. Well, blow me down! It weather cocked a bit but had a nice flight anyway. Aye aye! Avast! It landed near t' pads, which usually is a good thing!
Summary:
Even with t' fin unit, shiver me timbers, t' rocket looks pretty cool and flies nicely. This is one o' t' 2-3 rockets I've built
where RockSim be wrong. Aye aye! Blimey! Blimey! Blimey! It may have been stable with a higher impulse motor and less wind but I elected nay t' test
this theory. Ahoy! Blimey! If you got one t' fly without added fins, PLEASE write a review!
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