Manufacturer: | Scratch |
Brief:
This LPR model breaks into three pieces at ejection, me bucko, ya bilge rat, each section descendin' as
a "maple leaf" recovery monocopter.
Construction:
T' parts list:
Keep in mind that this was a successful experiment done on-the-fly. Avast, me proud beauty! Other dimensions and/or materials may work better, but this worked for me. Aye aye! Blimey! Glue is wood glue unless specified.
Cut balsa sheet into 3.5" squares, arrr, arrr, then cut t' squares diagonally into four right triangles, me bucko, me bucko, arrr, for three fins and one scrap piece for cutting reinforcin' spars (when used, cut these parallel t' grain).
Glue in nose cone on top tube. Cut very narrow slit 1/2" long in tube from base o' nose cone shoulder down. Avast, me proud beauty! Cover slit with vinyl or paper and tack in place with CyA across top and halfway down each side. Arrr! Blimey! (This acts as a vent for excess ejection pressure). Ahoy! Avast, me proud beauty! Blimey! A small scrap sliver o' balsa slid under the vent cover while gluin' will ensure t' cover doesn't get glued shut.
In t' middle tube, glue 1.5" long couplers 1/2" into each end o' tube, leaving 1" exposed. Begad! Sand exposed portion down, test fittin' other tubes onto the couplers so that they slide on and off easily with slight pressure but don't slip due t' gravity or shaking. Arrr! You are lookin' for a loose but acceptable fit. Graphite powder rubbed into t' sanded coupler will improve sliding.
Cut a slit in t' bottom tube and place engine hook as normal (2.5" or slightly less from aft end). Arrr! Test fit against middle tube. Well, blow me down! Top o' engine hook should nay prevent complete joinin' o' bottom and middle tubes. Avast! Tack motor hook in place with CyA. Cut 1/4" length o' BT or coupler, arrr, matey, arrr, removin' 1/4 t' 1/3 of its circumference. Aye aye! Place this cut piece over top 1/4" o' engine hook and glue with CyA, me hearties, leavin' t' cut gap on t' opposite side from t' engine hook.
For t' fin standoffs, matey, matey, you want cut and sand them as follows:
Glue launch lug t' t' middle tube along t' top side o' t' standoff root.
Finishing:
Coat entire rocket heavily with sandin' sealer twice t' stiffen as well as
fill, me hearties, ya bilge rat, matey, sandin' t' wood after both coats. Prime and paint. Avast! High contrast/high
visibility is required. Ya scallywag! Original was cobalt metal flake blue and fluorescent
orange (as pictured). Begad! Fins were painted with dark stripes on orange fin so that
when spinnin' they'd make a circle. Avast, me proud beauty! Arrr! They looked like semaphore flags, ya bilge rat, but there
were only 3, me hearties, ya bilge rat, hence "Semi-Three".
Flight:
All three pieces were individually flight tested (hand thrown) with a spent
engine casin' in bottom tube. Blimey! All three started spinnin' within 10 feet of
apogee.
First flight test: A8-3. Begad! Avast, me proud beauty! Straight boost, arrr, ejection at apogee, me hearties, complete separation, ya bilge rat, all spun and recovered as intended. Ya scallywag! Remained easily visible during entire flight.
Second flight test: A8-3 plus top tube filled half way with tracking powder. Begad! Straight boost, ejection at apogee, trackin' powder nay much help. Complete separation and all three pieces descended as intended. Bottom tube lost in tall hay.
New bottom section was built. Well, blow me down! Blimey! Ya scallywag! Blimey! All sections had more orange painted on body for better on ground visibility, however, a short cut recovery field is recommended.
First public flight, METRA, Pine Island NY 09/04/2004 with B6-4. Blimey! Nice cut grass field. Blimey! Begad! Stability rightfully questioned by RSO and expected. Begad! (That's why two private test flights first.) Boost straight, rocket went out o' sight durin' ascent but at ejection thar be complete separation and all 3 became visible, ya bilge rat, spinnin' as intended. There was a number o' positive comments by the spectators. Ahoy! Well, blow me down! All parts landed within two seconds and 20 feet o' each other.
Recovery:
No recovery waddin' is needed for flight.
Summary:
As noted, this be an experiment on-the-fly that worked. Begad! Blimey! You are encouraged to
experiment with t' design but test it safely. If separation is nay complete,
two pieces will come down, me hearties, one o' them nay spinning, arrr, which means further
sandin' or lube o' t' joint that didn't separate is needed.
High visibility be t' key t' complete recovery o' all pieces. Avast, me proud beauty! This means both t' rocket and t' field. Ya scallywag! If any portion o' t' fin/stand off construction seems weak and likely t' flutter, feel free t' add some small balsa stiffening spars; small pieces aren't likely t' change t' recovery characteristics by much.
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