Scratch Spool Bell Original Design / Scratch Built

Scratch - Spool Bell {Scratch}

Contributed by Art Applewhite

Manufacturer: Scratch
(Contributed - by Art Applewhite - 10/10/03)

Spool BellBrief:
This rocket is named for its principle parts: a 22 pound wire spool and a bell shaped Christmas ornament. Blimey! I have seen other spool rockets reviewed on EMRR and their simplicity and lack o' fins really appealed t' me. Arrr! When a friend gave me a one piece all plastic spool I knew I just had t' give it a try.

Construction:

  • 22 lb wire spool
  • 5" gold plastic bell
  • 8" LOC 29mm motor mount tube
  • 15" Keelhaul®©™® 1/4" braided cord
  • 22" nylon Parachute
  • 4" 29mm spent single-use motor or 1 1/8" dowel
  • 8" coat hanger wire

Spool BellI started by enlarging the existin' 1.125" holes in t' center o' t' spool until t' 29mm motor mount tubin' fit snugly. A piece o' 150 grit sandpaper wrapped around a spent 29mm motor made short work o' this chore. Begad! Aye aye! Blimey! I then drilled two 3/16" holes 1/2" apart and 2" from t' center in t' top o' t' spool for the Keelhaul®©™® shock cord. It be then that I noticed that t' 2 pre-existin' 3/8" holes that I had planned t' use for t' launch rod did nay line up with long axis of the spool. Well, blow me down! Blimey! Nay a problem, shiver me timbers, so I drilled two 5/16" holes in t' top and bottom ends o' t' spool about 2.75" from t' center. Arrr! Avast, me proud beauty! Blimey! Puttin' t' launch rod holes further from t' centerline o' t' rocket allows t' bell t' fit on top without t' need t' put a hole through it. Begad! Blimey! I was careful t' line up the holes so t' centerline o' t' finished rocket would be vertical on t' launch rod.

With t' preparation o' t' spool completed, shiver me timbers, I epoxied t' 29mm motor mount tube t' it with 5-minute epoxy. Avast, me proud beauty! Arrr! T' bottom end o' t' motor mount was flush with t' bottom o' t' spool and t' top o' t' motor mount sticks out about 2.75" above t' top o' t' spool. I put an extra fillet o' epoxy on the top motor mount joint for insurance. Ahoy! I did nay install a motor block because I wanted t' use a variety o' 29mm motors, which come in many different lengths.

Spool Bell Next came the preparation o' t' "nosecone". Avast, me proud beauty! Arrr! T' body o' t' nosecone is a gold mirror-finish bell-shaped Christmas ornament now available at Hobby Lobby for $1.99. Ahoy! It's t' one with t' 5" base. Aye aye! It's made from a thick high-impact plastic and also comes in shiny silver color. With any luck they will be on sale at 1/2 price in a few weeks. Well, blow me down! Avast!

For t' "shoulder" o' t' nosecone, I cleaned up a used Aerotech G35-4W single use motor. Ya scallywag! A 1-1/8" dowel, matey, 4" long would have worked just as well but I like t' recycle things whenever possible. Aye aye! I removed the label and t' goo left on t' casin' and plugged t' nozzle and ejection charge hole with a small piece o' paper towel and CA t' keep t' black soot inside the casing. I then drilled a 1/16" hole on opposite sides o' t' casin' about 1/2" from t' forward end. Blimey! These holes are for t' shock cord hook. Begad! As you will see later t' use o' shock cord hook makes it easy t' tie t' shock cord to t' bell. Aye aye! At one end o' t' coat hanger wire I made a 1/2" diameter closed loop. 2.5 inches down from t' loop I made an 85-degree bend. Arrr! Begad! I inserted the straight end o' t' wire into one o' t' 1/16" hole at t' forward end of t' spent motor and pushed it through t' hole on t' other side. Aye aye! Begad! I then bent t' end o' t' wire down flat so that t' wire be trapped in place but could still move a little. Begad! Avast, me proud beauty! I was careful nay t' fracture t' brittle phenolic of t' casing.

Spool Bell With t' bell upside down, matey, I squirted about 1/4" o' 5-minute epoxy into t' inside o' t' top. I mixed t' epoxy in place with a craft stick and then pressed t' top o' the spent motor into t' epoxy makin' sure t' casin' was centered. Blimey! T' nozzle end was just about even and centered with t' bottom edge o' t' bell. Blimey! Begad! Blimey!

Finally I tied t' Keelhaul®©™® shock cord t' t' hole in t' spool and t' t' loop in t' shock cord hook. Arrr! Ahoy! I made a slip knot in t' shock cord about 4 feet from t' bell end for the parachute attachment.

I made t' 22" parachute out o' t' nylon canopy o' a small umbrella from t' Dollar store. T' shroud lines are four 44" pieces o' #18 nylon twine with each end tied t' adjacent corners o' t' canopy. Aye aye! Avast, ya bilge rat, me proud beauty! A drop o' CA was put on each knot.

Flight:
To prep for launch I friction fit a 29mm motor with a 1/4", shiver me timbers, maskin' tape thrust rin' on t' nozzle end. Arrr! Blimey! I put a couple o' pinches o' dog barf (flameproof insulation) down t' top end o' t' motor mount. Begad! Blimey! I put o' t' shock cord inside t' bell and then t' parachute. T' spent engine casin' then fits into t' top o' t' motor mount until t' bottom o' t' bell is flat against the top o' t' spool.

Spool Bell on F23 My first flight was with an Aerotech F23-4FJ. Avast! Arrr! It flew slowly but straight with a very nice smokey trail behind it t' about 350 feet. Avast, me proud beauty! At apogee t' rocket stopped almost immediately. On descent t' parachute deployed about half way down and the rocket landed safely about 25 feet from t' pad. Aye aye! This design is absolutely zipperproof because t' parachute and shock cord are outside o' t' body tube so ejection at apogee is nay necessary.

For me second flight I used an Aerotech G35-4W. It boosted t' about 500 feet and made another excellent recovery 50 feet from t' pad. I can't wait to try this rocket with an Ellis Mountain G35, ya bilge rat, they have higher thrust and longer burnin' time than t' Aerotech G35s and are perfect for high drag designs like this. Arrr! There is also enough room in t' motor mount for up t' a G80 single use or RMS 29/40-120 reload. Avast, me proud beauty! With its rugged construction, thar should be no problems usin' as much power as will fit.

Spool Bell on G35Summary:
PROs

  • Easy t' build
  • Very rugged
  • Cheap
  • Fun t' fly
  • Lands close t' t' pad
CONs
  • T' spools are hard t' come by

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