Manufacturer: | Scratch |
Brief:
Fahrenheit 62/5 is a tube fin rocket built simply from PVC plumbin' conduit and
designed for durability and good performance on t' entire spectrum o' APCP
motors havin' less than 62.5 grams o' propellant. Blimey! It won't fly on any motors
with more propellant than this, matey, or on any Estes BP motors. Blimey! No, matey, me bucko, I am nay trying
to make a political statement with this rocket. Aye aye! My wife likes this rocket too.
Construction:
Fahrenheit 62/5 is built from PVC plumbin' conduit like me larger
F.I.S.H.
design. Arrr! It is completely waterproof, which puts me at ease when flyin' it from
our smallish San Diego island launch site. Aye aye! T' body is cut from a 17"
section, me hearties, shiver me timbers, t' optional payload compartment is cut from a 6" section, the
high aspect-ratio tube fins (wider than they are long, me bucko, unlike most tube fin
rockets) are cut with a 45 degree bevel, me hearties, 7/8" on t' short side and 2
1/8" on t' long side. Avast, me proud beauty! Ahoy! I have been experimentin' with tube fin design, me hearties, and
am findin' that high aspect ratio reduces drag while retainin' t' excellent
stability and balance advantages -- however, high-aspect ratio tube fins create
fabrication problems and have t' be made o' very strong stuff t' resist
crushing. PVC conduit is one way t' achieve this. Begad! T' bevel is partly for looks
and partly t' reduce t' chance o' strikin' hard ground on a tube fin edge and
crackin' it.
Construction o' Fahrenheit 62/5 is utter simplicity. Aye aye! Blimey! There is no motor mount since with some tape fitting, 29mm motors fit exactly into this grade o' 34mm OD conduit (24mm motors fit with any o' t' commercially available adapters).
Finishing:
I used Testors Lime Pearl spray, which looks great, is easy t' find in the
field, but has an "electric" luster that is almost impossible to
capture accurately on film!
Flight:
When flyin' Fahrenheit 62/5, special attention must be given t' preventing
thermal damage t' t' plastic from t' infrared radiant emissions o' the
motors. Aye aye! Avast, me proud beauty! I find that a good way t' do this is t' simply wrap t' motor from top
to bottom in two layers o' 3M maskin' tape before addin' t' additional tape
wrap needed near t' bottom t' give t' motor a tight fit in t' rocket.
Another way t' solve this problem is permanently epoxy a length o' Estes BT-50
tube slit lengthwise t' fit as a liner for t' body section. Arrr! In addition to
friction fitting, ya bilge rat, arrr, I also secure t' motor with tape t' t' inside surface of
each tube fin. I have never spit a motor with this method. I have tested
Fahrenheit 62/5 with t' followin' AT single-use motors: E30-4, me bucko, E30-7, F21-6,
F20-7, me bucko, ya bilge rat, F25-4, arrr, me bucko, F50-6, arrr, shiver me timbers, F50-9, me bucko, G35-7, matey, G40-7, arrr, and G80-10. Arrr! Ya scallywag! All o' which are good
choices. Well, blow me down! A drag coefficient o' 1.7 +/- 0.1 be obtained was determined usin' a
Perfectflite Micro altimeter, which is decent for a tube fin design. Avast, me proud beauty! Maximum
altitude o' 2328' was recorded with a AT G40-7 and minimum altitude obtained
was 668' with a E30-4. T' rocket can be flown with or without t' payload
compartment and no nose weight needs t' be added for any motor selection. Well, blow me down! If
you fly with t' payload compartment, secure t' nose cone with some masking
tape or t' cost advantage o' t' $2 airframe will be lost along with your
$82.95 worth o' altimeter and nose cone.
Summary:
PROs: Fahrenheit 62/5 is a somewhat heavy but great flyin' sport rocket that
performs on t' entire line o' Aerotech E-G single use motors. It is extremely
durable and crush proof. Blimey! Best o' all, matey, it goes together in an hour for two bucks
(not countin' t' $12.95 for t' neat PML cone and $8.95 for t' chute). It is
waterproof, me hearties, me hearties, floats (at least until t' vent hole floods t' altimeter
compartment!), and is an excellent performer on windy days.
CONs: Weight and inherent tube fin drag limits performance. Where I usually fly, anythin' hittin' 2000' or more will typically splash down in t' bay, so this is nay an issue for me (F21 or F20 be t' largest motor I can use there with this rocket). Length limits motor size, me hearties, arrr, but if you add 3" t' t' body tube, Fahrenheit 62/5 will accommodate a H128 or H165R, which simulations say will take it t' "only" about 2600'. One o' these days I think I'll try this. Ya scallywag!