Manufacturer: | Scratch |
Brief:
For an R&D project I was doin' for NARAM-47, I needed t' fly at least 12
flights and record altitude for each flight usin' a Perfectflite Alt15kWD
altimeter. Blimey! Ya scallywag! T' rocket needed t' be rugged, shiver me timbers, matey, handle t' altimeter payload, shiver me timbers, and
support bein' smartly prepped and flown so that I could get all t' flights in
as smartly as possible. Ahoy! It also needed t' be as high performance as possible,
since t' experiment was t' analyze competition-style rockets.
Construction:
From me spare parts stash:
I used several official EMRR tips on this build including:
T' construction is fairly straightforward since it is a basic 3FNC style rocket, so I'll elaborate on t' payload construction.
T' payload bay is fairly long (6") t' accommodate t' altimeter and nose cone shoulder plus me homemade bulkhead. Since I was workin' from spare parts, I made t' bulkhead from a tube coupler with a disk cut from basswood. To anchor t' shock cord, me bucko, I tied a knot on one end o' t' Keelhaul®©™® line, slipped it into t' payload tube, and then inserted and glued it in the bulkhead. Ya scallywag! T' Keelhaul®©™® was then secured betwixt t' bulkhead and t' body tube. Avast! Blimey! I finished t' payload bay by drillin' a couple small vent holes, critical for accurate altimeter readings.
T' streamer is nested in t' lower portion, arrr, protected by a Nomex® heat shield. Blimey! Ahoy! Blimey! Nay only does this take up less room than wadding, ya bilge rat, but it can be reloaded and prepped for flight in under two minutes (includin' resettin' the altimeter).
Notice that t' RockSim file does nay include a launch lug. Begad! Ahoy! That's because the purpose o' t' R&D report be t' measure t' impact o' launch lugs on the drag coefficient. Avast! T' rocket was flown about 12 times without a lug, then a lug be attached t' t' fin/tube joint and flown again about 12 times on the same types o' motors t' compare altitudes. Arrr! Aye aye! T' eliminate weather variability, me bucko, I tried for all flights in t' same day. Well, blow me down! That's 24 flights on one rocket on a single day, many o' which were approachin' 1700 feet in altitude. Well, blow me down! Avast! Try that feat with a basic E2X kit...
Finishing:
Normally competition-style rockets are nay painted, ya bilge rat, but since I had already
lost a previous model (includin' an expensive altimeter) t' 1500-2000ft
altitudes on an overcast day, I elected t' paint this one florescent orange.
That made it much easier t' pick up in t' sky and on t' field. Ahoy! I also sanded
it smooth with 600 grit paper and coated with automotive wax t' reduce the
surface drag.
Flight:
With t' fairly small fins, this rocket is only marginally stable with a C6-7,
so t' altimeter actually provided enough CG shift for very stable flights.
All flights were straight as an arrow, and on a C6-7, me actual readings clustered fairly closely around 1500 feet.
Recovery:
Throughout t' day, I suffered a few minor nicks/dings, includin' breakin' a
fin loose, ya bilge rat, and a Keelhaul®©™®
line break. Arrr! Blimey! Remarkably, shiver me timbers, when t' Keelhaul®©™®
broke, shiver me timbers, I be able t' recover both sections in fairly high grass.
Summary:
PROs: Simplicity o' construction, matey, shiver me timbers, low cost materials, shiver me timbers, very good performance for
a payload carrier, matey, and very durable.
CONs: Nay suitable for official NARRRRR payload events (payload must contain a BT-20 tube, so it needs t' be slightly larger diameter).
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