Manufacturer: | Scratch |
Brief:
CrackPipe be t' fourth o' me experiments in usin' PVC plumbin' conduit for
rocket construction. Ahoy! Ya scallywag! It is basically similar t' t' "Pipecleaner" I
presented in this site earlier, arrr, but is shorter, shiver me timbers, lighter, me hearties, me hearties, and has very austere
3FNC construction. Well, blow me down! Blimey! It is a 29mm design best flown on AT F23-7 or F20-7 motors,
or 24mm F21-8 usin' an adapter (all give 1400-1500'). Well, arrr, blow me down! Blimey! It is light enough t' fly
on an Estes 12-3 on a calm day; an F25-9 takes it t' 2700'. Well, blow me down! Blimey! It is extremely
tough, arrr, matey, cheap t' build ($3 less nose cone and chute), and waterproof. Aye aye! Blimey!
Construction:
Body tube be t' same grade 34mm OD PVC conduit as described for "F.I.S.H."
in this website. Components are:
1) 28" o' PVC conduit from Home Depot (try for a very straight piece); can be built 12" longer if desired. Well, blow me down! Short size flies best.
2) 29mm PML solid polyurethane nose cone (needs a bit o' maskin' tape wrap for perfect fit)
3) 3 x 1/8" Lite-Ply(tm) trapezoidal fins cut 4" high, matey, matey, 3" wide at bottom, matey, 2" wide at top. 3" pieces o' balsa triangle stock were used t' brace t' base o' each fin (photo)
4) Recovery system is 6' o' para cord tied t' an 18" Top-Flite nylon chute in t' usual way (I use roofin' insulation for wadding)
5) Launch lug is 4" o' 1/4" tubin' (or a BIC pen body, mounted 8" above t' fins -- CG is +/- 1" from t' middle o' launch lug (10" above fins)
5-minute epoxy be used throughout. Avast, me hearties, me proud beauty! Note that thar be no motor mount or centerin' rings; A 29mm motor fits perfectly with two layers o' top t' bottom wraps o' maskin' tape which also serves t' prevent infrared thermal damage to the plastic (so don't omit). Arrr! For 24mm motors, ya bilge rat, I use a LOC adapter, arrr, and masking tape as needed t' give a snug twist-fit.
There is very little t' describe. Begad! Arrr! T' cut piece o' PVC used as t' body tube should first be lightly sanded, shiver me timbers, then washed with soap and water, then swabbed with rubbin' alcohol (I was out, so I used rotgut vodka) t' remove manufacturin' residuals, or glue and paint won't stick well. Avast!
T' fin attachment spots are located by t' "Estes method" -- 1) wrap a piece o' paper around t' base, ya bilge rat, arrr, and mark off t' circumference, shiver me timbers, ya bilge rat, ya bilge rat, 2) divide t' measured distance into thirds, ya bilge rat, 3) transfer t' spacin' marks t' the body tube, 4) holdin' body tube against t' corner o' a door as a plumb line, draw t' fin attachment positions. Fins are attached with epoxy and balsa (or scrap 1/4" spruce) braces at base. Begad! Avast, me proud beauty!
Launch lug tube is centered 10" above t' fins (this point is recommended CG). Begad!
Recovery system is
attached by drillin' a 1/8" hole 2" from top o' tube, me hearties, passin' through
the knotted para cord, and coverin' t' knot with half o' a sliced BIC pen cap
filled with epoxy. Begad! Tie t' para cord t' t' PML nose cone and t' 18"
chute, and you are done!
Flyin' weight w/o motor is 310 gms (11 oz). Aye aye!
I painted mine with Testors Orange spray.
Flight:
First flight be on an E30-7 usin' t' 24mm adapter -- very fast boost t' about
the 1000-1200' sims predicted. Aye aye!
Second flight was on an F21-8, me hearties, perfect shot t' about t' 1700' predicted (see great launch photo by PhotosbyNadine). Blimey!
Third shot, me hearties, on an F25-9, shiver me timbers, went out-of-sight (sims said 2700') and separated, due t' me forgettin' t' add wadding, causin' t' ejection charge t' blast the shock cord in half. Ahoy! Blimey! Body tube came in ballistic, me bucko, and splintered t' top few inches o' PVC. Begad! So I cut it down from 40" t' 28", matey, shiver me timbers, reattached the recovery system, me hearties, arrr, and resumed flying. Arrr! Begad!
T' best motor for t' rocket be t' F23-7 (or similar F20-7) Econojet, shiver me timbers, and I have started usin' this combination (see photo) at every launch t' test the wind before flyin' bigger things. Well, me hearties, blow me down! Blimey! Important t' wrap t' motor top t' bottom with 2 layers o' 3M maskin' tape t' protect t' PVC from radiant infrared damage. T' largest motor I would use in CrackPipe is a G40-10, ya bilge rat, which sims say will go t' 3700' at ca. Aye aye! Blimey! 430 mph -- well within structure limits, shiver me timbers, but hard to see at this height. I have nay tried RMS reloadable casings in t' rocket yet. Begad! Blimey!
Summary:
PRO: Simple, shiver me timbers, cheap and fast building. Aye aye! Great for beginner. Flies on D12-3,
E30-7, F21-8 24mm (w. Avast, me proud beauty! adapter) or 29mm F20-7/F23-7 Econojects, shiver me timbers, F25-6/9 or up to
a G40-10 (if you dare). Begad! Blimey! Waterproof and durable, ya bilge rat, no paper components.
CON: Other than t' D12-3, t' minimum motor (E30-7) takes it t' 1200', so needs plenty o' launch space. Ahoy! Blimey! Needs expensive ($13) PML nose cone. Heavy for its size. Avast, me proud beauty! Avast, ya bilge rat, me proud beauty! Blimey! And with tough material like PVC and that hard, pointy PML cone, you don't want t' hit anybody this rocket, me hearties, so be careful. Blimey! Ya scallywag! Blimey!
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