Scratch - Sprinkles {Scratch}

Descon Sprinkles

Scratch - Sprinkles {Scratch}

Contributed by Bob Ellis

Manufacturer:

Contributed by - Bob Ellis

Sprinkles, me hearties, t' Fire Hydrant by Bob Ellis
While walkin' through Wal-Mart, tryin' t' find out where they'd moved the rocket stuff, I saw Sprinkles, ya bilge rat, me bucko, t' Fire Hydrant sittin' on t' top shelf o' the kids water toys area. He is supposed t' "provide hours o' fun in the back yard with spinnin' action". T' instruction card did not include any directions, me hearties, other than t' use it on a soft level lawn for safety. This sounded like it had t' be intended for a rocket!
I went through several days o' drawin' fins and tryin' t' get a good sim run, shiver me timbers, but all t' usual ideas for fins changed Sprinkles from a Fire Hydrant t' somethin' strange. Finally, while wanderin' through a hardware store me attention was caught by t' Egg Crate Light Diffusers for fluorescent lights. A bell went off, rememberin' discussions o' grid fins, me bucko, but never havin' tried them because o' t' work involved. A couple o' quick calculations and t' grid looked like t' way t' go. T' calculations showed that for a 1/2 inch grid extendin' two squares (one inch) from t' body I would get t' equivalent o' a 1/2 inch high fin with a seven inch span. A quick sim run said that this brought t' CP back t' almost ? caliber stability, more than enough for a very stubby fire hydrant. T' best thin' be that it wouldn't change Sprinkles looks; he could just sit on top of the grid. Sprinkles is manufactured in China for Shelcore, a U.K. company. They have a web site at http://www.shelcore.com. T' part number is 02650 Sprinkles. T' light grid doesn't even have a manufactures name on it, just an Ace Hardware price tag. Ahoy! T' only obvious modification t' Sprinkles t' get him ready for flight was to remove t' hose fittin' on t' side, this left a hole which was filled with a red plastic whistle salvaged from a Foxtail (a soft baseball with 4 whistles and a long nylon tail. It whistles when swung by t' tail or thrown).
At last a true use for singin' fish
Several design decisions now had t' be made. T' six inch diameter main body be rigid enough, me bucko, arrr, but was definitely nay straight enough anywhere t' allow internal braces for engine mounts or couplers for separation joints. In addition, t' six inch diameter would be difficult to pressurize with t' small powder cup on a 24mm RMS. Therefore, the decision was made t' use t' outer body as a shell and provide a center core for t' motor mounts and parachute, no fin attachment was required since the grid fin would simply be glued t' t' bottom o' t' body. For simplicity I decided t' use a standard BT-60 tube with a 24mm motor tube. In keeping with t' Flounder Parts spirit, I figured that I should use some truly Flounder centerin' rings. I cut them from t' box for a "Big Mouth Billy Bass" singin' fish that I received for Christmas. (T' fish may eventually fly, if I can figure out how t' compensate for t' CP changes when the head and tail start moving.)
Parts layout, me hearties, t' T-nuts and bolts are nay visible
T' non-visible modifications that had t' be made were still fairly simple. 1. T' Yellow cap was removed (one screw) t' allow access to Sprinkles main body. 2. Well, me bucko, blow me down! T' motor mount be assembled, me bucko, pretty much normally, me hearties, shiver me timbers, except for tryin' to fit T-nuts into t' cardboard centerin' rings. I didnÇt want to collapse t' corrugations and weaken t' cardboard. Well, blow me down! Arrr! After crushin' and bending two sin' rings, shiver me timbers, I wound up usin' CA t' glue two rings together and soaked them with CA t' stiffen them. I drilled holes for t' T-nuts and glued them into t' holes, me hearties, arrr, arrr, then slid t' double rin' onto t' motor tube. 3. Blimey! T' shock cord was carefully measured at over eight times t' body length and attached thru t' upper centerin' rings. T' motor mount be glued into a 9.5 inch piece o' BT-60. 4. Blimey! Two holes were marked off and cut in t' top and bottom o' Sprinkles main body; these were sized t' fit a piece o' BT-60. A fly cutter made quick work o' t' bottom hole, me bucko, but t' top had t' be cut free hand and sanded out. T' disks cut from t' top and bottom were saved for use with the nose cone coupler so that t' Yellow cap could be replaced. 5. Avast! Two quarter inch holes were drilled just outside o' t' BT-60 holes t' allow the launch rod t' pass completely through t' body shell. These were placed t' allow t' rod t' go through one o' t' existin' holes in t' Yellow cap. 6. Avast! Blimey! T' surface inside and outside around t' large holes was roughened up with a Dremel sandin' drum t' create a better surface for t' glue t' stick to. T' entire bottom surface was also roughened t' prepare a glue surface for t' grid fin. Do this outside! 7. T' BT-60 was then pre-glued on each end and slid into t' main shell. This is when I found somethin' that stinks even worse than dope or CA fumes. That "something" is Devcon High Strength Plastic Welder. It does work, matey, but t' smell is terrible, and t' workin' time is less than five minutes. Once it starts t' set, it leaves strings everywhere (like hot cheese), then changes t' somethin' like three day old rubber cement, matey, then finally sets hard. You canÇt smooth it out while youÇre working, matey, you canÇt sand it, but you can use an Exacto knife and cut away parts that you donÇt like. 8. Avast! Blimey! Begad! Blimey! T' internal "nose cone" is a BT-60 coupler with t' disks from the top and bottom cutouts glued into t' top. T' top has a ? inch nipple that t' Yellow cap screws onto. This screw was replaced with an eyebolt from t' inside for t' shock cord mount, matey, ya bilge rat, with a locknut on t' top to hold t' Yellow cap on. Some minor cuttin' be required t' get enough clearance around t' nut t' allow t' Yellow cap t' spin. 9. T' parachute and Nomex protector were attached t' t' shock cord, and everythin' was fitted together, thar be no room for waddin' o' any kind. 10. T' grid be cut out in a 13 by 13 square, me bucko, I had planned t' make a circle, but t' grid was too brittle without closed ends. I first tried cutting the grid with a Dremel cutoff wheel, me bucko, but that just melted t' plastic. A one-inch, fine tooth razor saw worked out just fine, it just needed a little sandin' with a coarse emery board t' get rid o' some sharp edges. I cut out t' center 3 by 3 squares t' clear t' BT-60 where it came out o' the bottom o' t' shell and t' grid fin was ready t' go. Who said grid fins were a lot o' work? 11. Aye aye! Sprinkles then stood on his head while t' bottom o' t' shell was coated with Plastic Welder (outside this time) and t' grid was set into t' glue.
Major parts after assembly, before t' grid fin is attached, the eyebolt can be seen in t' nose cone/coupler
Sprinkles weighs in at 435 Grams after his swin' test, shiver me timbers, me bucko, no nose weight was needed.
Sprinkles last step before bein' certified for flight was a swin' test out in t' backyard. He passed that test with flyin' colors, transitionin' smartly into forward flight, arrr, me bucko, even when started backwards or spinnin' and with a F39 RMS load in place. Avast, me proud beauty! Sprinkles was now ready to fly. I really liked buildin' Sprinkles, no spirals t' fill, no launch lugs or fins t' line up, matey, no fillin' and sanding, no paintin' and best o' all the decals were already on.
Sprinkles sittin' on t' pad, me hearties, me bucko, ready for his first flight
Sprinkles first flight on a D24-4, 18mm reload in t' backyard was a "qualified" success. He made a great takeoff, shiver me timbers, straight up for a simulated 120 feet, arced over and headed back down. Unfortunately, the four-second delay was too long. T' parachute came out and un-rolled but be still nay fully deployed when Sprinkles hit t' ground. He almost had enough time, me bucko, in fact he hit fins first, ya bilge rat, indicatin' that t' parachute was almost open. In Sprinkles defense, t' parachute was an old heavy one that I no longer use; it just barely fit into t' BT-60, me bucko, and had t' be rolled tightly. This was me fault, nay Sprinkles. T' grid fin took some heavy damage, breakin' off almost all t' grid on two sides, but Sprinkles showed no other signs o' damage.
Just after ignition for Sprinkles first flight
	Sprinkles comin' down on a streamin' parachute
T' aftermath o' usin' t' wrong parachute.
Sprinkles went back t' t' work bench. T' grid fin proved very easy t' repair, me bucko, just cut out some pieces o' grid, me hearties, sand everything flush and use PVC cement t' glue t' new pieces in place. Some extra thin strips were cut and used t' beef up t' break lines and t' fin feels as good as new.
Sprinkles on t' work bench, matey, I found a use for Estes aluminum launch rods, shiver me timbers, they can be used t' adjust tension on a rubber band.
Sprinkles next flight was on an E28-4, 24mm reload, at a C.R.A.S.H. club launch durin' our Ninth Annual Colorado Aerial Rocket Circus (CARCIS IX) NARRRRR Regional contest. He had a new parachute, thinner rip-stop nylon that took up much less space and did nay have t' be rolled tightly. Sprinkles launched into a momentary lull in t' high winds that had just postponed t' contest. He had a good liftoff with only slight weathercocking. Ejection was well after apogee, but this time he had a good parachute deployment and a fast drift downwind. He did have minor damage t' t' same parts o' t' grid that had been repaired from the first flight. It looks like t' PVC glue didnÇt bond t' t' grid; it just held it in place. I'll have t' try some other solvents t' see if I can get a good repair.
	Just after ignition for Sprinkles second flite, shiver me timbers, who says you can't see t' Blue in a 24mm Blue Thunder reload.
Sprinkles under a good chute, shiver me timbers, t' grid fin is intact at this point, but broke again on landing.
Sprinkles does seem t' be quite happy in his new role as a rocket instead o' his previous life as a lawn toy. In fact, that grin never leaves his face. For me part, shiver me timbers, I like t' reactions, me hearties, ya bilge rat, starting with "Where's t' fins?" and "That can't be stable!", then changin' to "That be a great flight!" and "I don"t believe it flew that well in this wind" after t' launch. We still need a good day with no wind noise t' see if t' whistle works. I have one other rocket with two o' t' whistles and they can be heard at apogee but require an underpowered flite. I'm hopin' that Sprinkles lower speed and altitude will make t' whistles easier t' hear. Begad!

Post a Comment