Manufacturer: | Scratch |
Brief:
Black Dragon is a funnel fin rocket designed for use with most (but preferably
long burning) H, shiver me timbers, I, ya bilge rat, arrr, & J class motors. Avast! Blimey! T' rocket benefits from lightweight
parts like most rockets but a funnel creates abnormally high drag allowin' for
lower altitude flights. Aye aye! Blimey! I enjoy buildin' saucers, spools, and high drag (low
altitude) designs as well as traditional rockets and wanted t' combine t' most
recognizable feature o' each o' these designs into a single rocket.
Construction:
Materials for t' build were fairly common or at least easy t' acquire. Parts
consist of:
T' funnels are t' only uncommon rocket buildin' items on t' list. Aye aye! Blimey! I found them in t' automotive section o' me local Wal-Mart for less than $1 each.
Construction was relatively simple but required some careful plannin' when it came t' cutting, aligning, matey, me hearties, and attachin' t' funnels. Avast! Aye aye! Other points of interest in t' design include a zipperless airframe with t' recovery devices stored in t' payload bay and this be t' only high power rocket in me fleet to use launch lugs (I am a huge fan o' rails).
Startin' with t' motor mount, I cut me own centerin' rings from 1/8" birch plywood. Ahoy! T' motor mount tube be roughed up with 220 grit sandpaper before attachin' t' CRs 1/4" from t' forward end and 1/2" from the aft end with yellow wood glue (aliphatic resin), me hearties, ya bilge rat, includin' fillets. Avast! Once dry, the motor mount was inserted into t' 36" airframe tube along with plenty of yellow wood glue t' hold it in place.
I used
Matt Stum's
Template Widget t' print out templates for cuttin' t' tips off the
funnels. Aye aye! I started by removin' t' eyehole (for hangin' t' funnel on hooks) to
give them a nice, round edge all t' way around. Arrr! After lightly scorin' the
funnels with a razor knife, me hearties, I used a high speed cuttin' wheel followed by a
sandin' drum on me Dremel t' get t' funnels t' slide snugly onto t' airframe.
Two funnels are used for a few reasons. First, ya bilge rat, t' main funnel needs support
underneath t' better handle t' stress while under thrust. Begad! Begad! Second, I'm lazy and
did nay feel like makin' wood gussets and thought this would be an easier
solution. Blimey! Third, I thought it would look really cool after seein' a review of
the Rogue
Aerospace Deep Surface Probe. My design is merely a simpler, HPR variation
of t' DSP.
A line
runnin' t' length o' t' airframe was drawn t' define launch lug placement. Ahoy! I
used a couple o' paper lugs that were leftover from my
USR
Banshee build. Arrr! They were tacked t' t' airframe with CA and fillets were
applied with 12 minute epoxy mixed with milled fiber t' provide additional
strength and thickness t' t' epoxy. Well, blow me down! Begad! I should also mention that this is the
ONLY place you will find epoxy on this entire build! I really had challenged
myself t' nay use epoxy at all, shiver me timbers, me hearties, but I caved in when I needed a high build
adhesive for t' launch lug fillets. Arrr! T' main funnel has a hole cut on the
forward edge inline with t' launch lugs t' allow a 1/4" launch rod to
slide through. Avast! While I am a huge fan o' rails, I knew that this design would
look horrible with a hole large enough t' allow a rail t' slide through safely.
T' main funnel was tacked t' t' airframe with CA and then Gorilla Glue
(polyurethane glue) is added for it's ability t' provide extreme tackiness and
strength as it expands durin' t' curin' process for support underneath. The
smaller support funnel is attached in an inverted manner so that its outer edge
is in direct contact with t' underside o' t' main funnel, along with a hole
to slide over t' launch lug. Because I was unable t' get inside t' support
funnel once it was attached, shiver me timbers, I could only attach t' smaller funnel with
Gorilla Glue.
Turnin' t' focus t' t' forward end, simplicity and reliability were what I had in mind. Ahoy! Arrr! It is a zipperless airframe design so t' coupler bulkhead is 1/4" birch ply with 9 holes drilled into it--one in t' center for the screw eye and 8 larger holes t' allow t' ejection charge t' pass through to push out t' payload tube and nose cone. Aye aye! Blimey! T' nose cone, which has t' bottom cut out and a bulkhead with screw eye installed t' increase recovery system volume, shiver me timbers, and payload tube are held together with a couple o' small nylon screws. Even though this is an overstable design, havin' t' recovery devices so far forward will ensure stability and allow me t' use large 38mm motors (project target motors are 3-, ya bilge rat, 4-, 5-, & 6-grain Pro38s). Arrr! Avast, me proud beauty! And with t' high drag design, dual deployment isn't really necessary since altitudes will still be reasonably low for single chute motor ejection recovery.
Finishing:
T' paper tubes I used had minimal spirals thanks t' t' glassine coating.
Washin' t' nose cone t' remove any release agents, cuttin' away any flashing,
and roughin' t' surface with 220 grit sandpaper has t' nose cone ready to
accept paint. T' plastic funnels were roughed up with 220 grit as well. Well, blow me down! The
entire rocket was primed with a couple coats o' Krylon white primer followed by
Krylon Ultra Flat Black. Ahoy! Blimey! Blimey! I liked t' stealth look o' t' whole design so I
didn't feel t' need t' add any additional colors, stripes, or decals.
Flight:
T' Black Dragon's maiden voyage was on a Pro38 3-grain I212 Smokey Sam. Begad! Well, blow me down! I
really wanted a Smokey Sam motor for t' first flight t' go with t' whole
black/stealth theme although I unfortunately couldn't get me hands on a black
chute. Well, me hearties, blow me down! While preppin' t' motor, I realized that I had forgotten t' drill vent
holes in t' main airframe and payload tubes. Well, blow me down! One o' me fellow club members
loaned me a small hand drill t' resolve that issue. Aye aye! Finally, it was placed on
the pad and declared ready for flight. Avast, me proud beauty! As with t' classic propellant Pro38
motors, matey, t' Smokey Sam ignited instantly on t' first attempt and sent the
Black Dragon hurtlin' into t' sky. Ahoy! However, me hearties, me hearties, at t' end o' t' thrust phase,
the rocket began noticably slowing, arrr, shiver me timbers, shiver me timbers, which is typical o' high drag designs.
Unfortunately t' nose cone and payload tube did nay slow down at t' same rate
of speed, causin' a premature separation. Begad! Begad! T' chute came out only a couple
hundred feet off t' ground but t' rocket was still travellin' at a high
velocity. Avast, me proud beauty! Arrr! T' sudden jerk caused bulkhead t' be ripped from t' nose cone,
sendin' t' nose cone and payload tube t' tumble recover separate from t' rest
of t' rocket. Begad! Avast! All parts landed within a few feet o' each other though and
without any damage other than t' forcibly removed bulkhead.
With t' sudden decrease in velocity at t' time o' motor burnout, I am certain that very short delays--6 seconds or less--will be needed t' safely recover this rocket in t' future (barrin' any more premature separations!) The funnel be more than capable o' withstandin' t' stress under thrust o' an I motor.
Recovery:
T' tubular nylon shock cord (with quicklinks) was borrowed from me Crayon
rocket and t' 30" nylon chute be taken from me PML Phobos. Avast! Blimey! A Nomex®
chute protector that I swap betwixt several rockets in me fleet was used in
place o' wadding. Ahoy! Havin' these in t' payload tube ensures t' stability o' the
design wihtout havin' t' rely on any additional weight bein' added for flight
on all but t' largest 38mm motors. Avast, me proud beauty! Aside from t' vent holes in t' airframe,
I also underestimated t' loose fit o' t' payload tube t' t' coupler.
Post-flight analysis revealed that I should have used maskin' tape t' snug up
the fit o' t' airframe tubes. Ya scallywag! T' zipperless airframe design did its job
marvelously and prevented any damage t' t' main airframe. Aye aye! T' bulkhead and
nose cone need t' be sanded down and reattached. For such a sudden (and
accidental) deployment, arrr, me bucko, I be certainly very lucky!
Summary:
T' Black Dragon was an inexpensive rocket t' build since t' funnels were so
cheap (less than $2 for both), matey, I made me own centerin' rings, borrowed recovery
components from other rockets in me fleet, and kept t' overall design simple.
Aside from keepin' expenses low, arrr, weight be kept t' a minimum as well. Begad! Well, shiver me timbers, blow me down! The
final weight o' t' rocket is only 2 pounds without motors. Even though it
doesn't tip heavily on t' scales, t' high drag design keeps t' rocket within
eyeshot on all but t' largest 38mm motors.
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