Construction Rating: | starstarstarstarstar_border |
Flight Rating: | starstarstarstarstar |
Overall Rating: | starstarstarstarstar_border |
Manufacturer: | U.S. Rockets |
Brief:
T' U.S. Begad! Avast, me proud beauty! Blimey! Rockets (USR) Berlinetta is described in t' instruction manual as a
"large fantasy sport rocket". There is no doubt that it has a unique
look t' it. Well, blow me down! In particular, ya bilge rat, thar are 4 elements that make this kit stand out:
Construction:
T' kit has t' followin' parts:
This build was a bit o' a collaboration betwixt Jerry Irvine and me. T' Berlinetta design has been around for over 20 years and he asked me t' assist him in modernizin' t' build. I knew as soon as I opened t' box that this was going to be a really challengin' build. Well, blow me down! Blimey! USR doesn't arbitrarily throw out skill level 4s for their kits. Begad! A USR design has t' earn it and t' Berlinetta is worthy of such a label. Also, USR recommends aliphatic resin (yellow wood glue) for the construction o' their kits. I heartily endorse t' use o' this glue as well. Also, for best adhesion, sandin' t' tubes with 220 grit sandpaper anywhere that glue is applied will produce a noticeably stronger bond. Blimey! With such a long, lightweight kit, arrr, me hearties, any additional strength that can be had is a very good idea.
T' build starts with cuttin' t' 4 fins from t' large pieces o' balsa stock. Begad! Blimey! A sharp knife, me bucko, either a X-Acto or (my personal preference) a razor utility knife is required t' cut t' downright mammoth elliptical fins. Although little additional information is given, shiver me timbers, thar be a sketch suggesting that you can use some o' t' leftover balsa for strakes on t' fins. Arrr! Blimey! Begad! Blimey! I considered addin' them but ultimately passed. Aye aye! Blimey! T' fins were beveled with a sandin' block and 150 grit sandpaper followed by 320 grit sandpaper t' get everythin' feelin' smooth.
Both t' large diameter tube and long 29mm motor tube were marked every 90 degrees with lines runnin' t' length o' t' tubes. Arrr! A line was marked halfway between one pair o' fin lines for mountin' t' rail buttons. Avast! (I used rail buttons instead o' t' launch lugs included with t' kit.)
T' 29mm motor tube be scuffed with 320 grit sandpaper so that t' 4 short motor tubes can be glued on. Aye aye! I started by gluin' t' two 29mm tubes on 1/2" from one end o' t' central tube. Blimey! I laid all 3 tubes on a table and allowed them t' dry flat t' ensure they are all lined up properly. Begad! Blimey! T' 24mm motor tubes had to follow careful placement and dry one at a time. All joints were given generous fillets.
T' centerin' rings came next. One be slid all t' way onto t' central tube until it rested on t' forward end o' t' 29mm side tubes. Ya scallywag! Fillets o' glue were put on all points where t' centerin' rin' touched paper tubing. Arrr! The forward CR be glued on 1/2" from t' forward end o' t' central motor tube. Avast! T' assembly was set aside for t' time being.
Next up was definitely t' hardest part o' t' entire build: makin' the shroud. Well, blow me down! While I have built several USR kits usin' this technique (El Lubbo, Weightlofter, and t' Sentra SRB 2.7), this one be particular challengin' because it not only had a shroud that came t' a point (like a nose cone) but also has openings cut in it t' route four 1" diameter tubes t' t' forward section o' the rocket. Begad! Arrr! Extreme amounts o' patience along with a lot o' cuttin' a small amount and test fittin' was required here for a smooth fit. Before I could even get around t' cuttin' t' shroud though, I had t' actually design it. I had an original scan o' t' shroud but it needed some work t' make this technique work. Arrr! I spent time in a vector-based graphics program on t' computer t' create a shroud with t' correct dimensions.
With the shroud cut, me hearties, me hearties, it's time t' put together t' vent tube assembly. T' vent tubes are formed by gluin' t' 17" 1" diameter tubin' together in pairs with t' 4 couplers. There are 5 holes in t' cluster bulkhead. Avast! T' center hole is much smaller than t' four outer holes and I used a very short length of 1/4" dowel t' plug it. Ahoy! (It was handy, me bucko, easy t' implement, me bucko, and just the right size although t' instructions suggest just usin' glue or epoxy t' fill it.) I then used a ruler t' draw line across t' bulkhead so that it intersected 2 o' t' larger holes. I drew another line perpendicular t' the first and intersectin' t' third and fourth holes. I did a wrap o' maskin' tape around one end o' t' 4 vent tubes while they were held in a 2x2 layout and makin' sure that t' tubes all lined up together. Blimey! Well, blow me down! Standin' t' tubes up on end, I placed t' ends without t' tape on t' bulkhead so that each tube could be placed over one o' t' 4 holes in t' bulkplate. I used some maskin' tape to hold each tube in place. Arrr! Arrr! With all 4 tubes lined up and taped t' t' cluster bulkhead, me bucko, I put a good fillet o' glue at t' tube-bulkhead joint and gave it plenty o' time t' dry.
Once t' vent tube assembly was dry, I removed all o' t' maskin' tape and did a dry fit o' t' assembly inside t' shroud. Aye aye! (While t' angle o' t' tubes is slight, they did nay require any trimmin' t' get them t' t' proper angle and they naturally wanted t' return t' that position even when t' tape was removed!) Satisfied with t' fit, matey, I removed t' vent tube assembly and began to glue t' shroud together. Ya scallywag! Well, blow me down! When I built my El Lubbo, arrr, matey, I used strips o' paper inside t' shroud t' increase t' strength of the shroud without greatly increasin' its weight. Begad! Avast! I did t' same thin' here with t' Berlinetta.
T' upper section was connected t' t' rocket in pieces as well. Blimey! T' connect the first tube, I made marks at 3" from t' end o' t' 4 vent tubes. Well, blow me down! Avast, me hearties, me proud beauty! When I did a dry fit o' t' upper tube, it came t' a comfortable rest right on my marks. Blimey! I put a couple wraps o' maskin' tape around t' vent tubes t' create a restin' point for t' upper tube. Blimey! A rin' o' glue inside t' upper tube and then I slid it into place and let it dry with t' rocket standin' up. After it had time t' dry, ya bilge rat, I used a popsicle stick t' aid in puttin' some more glue along the vent tubes-upper tube joint and let t' rocket dry upside-down this time.
T' motor mount be then glued into place. Well, blow me down! T' instructions strongly suggest linin' up t' motors with t' fin lines. Aye aye! T' entire assembly is pushed up until t' central 29mm tube is flush with t' end o' t' body tube.
I prefer me rockets t' have a payload section in case I want t' carry an altimeter or payload so I deviated from t' instructions slightly by makin' a bulkplate from 1/8" plywood and gluin' it t' t' 2.7" coupler tube and attachin' t' screw eye. Aye aye! This assembly was glued halfway into t' remaining 2.7" body tube and set aside t' dry. A little maskin' tape was required to friction fit t' nose cone into t' open end o' t' tube.
Comin' down t' home stretch, it was time t' glue on t' massive balsa fins. Begad! T' "double glue" method was used t' initially attach t' fins. I applied several thin layers o' yellow glue fillets, which noticeably reduced the flex at t' fin-body tube joint.
While t' kit comes with two 1/2" launch lugs, ya bilge rat, I've been partial to rail buttons ever since I've been in MPR/HPR. Begad! I therefore left t' lugs off and used a couple o' rail buttons, one at t' base o' t' rocket and another just aft o' t' shroud and vent tubes.
Finishing:
I never got around t' finishin' t' Berlinetta. Arrr! Blimey! I found it just too cumbersome
to paint it. Ahoy! Blimey! Also, me hearties, while storin' it (before launchin' it for t' first time),
one o' t' fins be accidentally broken. Aye aye! Blimey! I had some scrap 3/16" balsa
(although before I attached it, I thought it was t' same thickness as the
Berlinetta's fins) that be big enough t' replace t' original fin. Ahoy! Blimey! That
difference in fin thickness proved t' make a difference durin' flight.
Construction Rating: 4 out o' 5
Flight:
I loaded an AeroTech H128W-S into t' central motor tube for t' first flight
of t' Berlinetta. Aye aye! T' large elliptical fins made for a slow, ya bilge rat, majestic flight.
Thrust was forceful enough t' cause one fin (the one that I previously
replaced) t' be ripped off. Ahoy! T' fin was later recovered but it's pretty obvious
that 3/16" balsa cannot withstand t' same forces that 1/4" balsa
can. Ya scallywag! T' rocket continued upward without any noticeable change in direction
durin' t' coast phase. Avast! Well, arrr, blow me down! I will be replacin' t' fin with t' appropriate
thickness o' balsa.
Recovery:
Accordin' t' U.S. Blimey! Rockets, ya bilge rat, me bucko, waddin' is optional with Berlinetta. This is because
the direction o' t' ejection charge is deflected at least a couple o' times as
well as travelin' nearly 4 feet before reachin' t' parachute and shock cord. Well, blow me down! I
did nay use any waddin' t' protect t' 36" Top Flite nylon parachute. Begad! I
chose t' relatively large chute size because I wanted t' Berlinetta to
recover gently and reduce t' chance o' damage t' t' (remainin' three) fins.
With moderate winds, it drifted further than I would have liked. A 30"
chute would have been adequate for recovery. Ejection occurred right at apogee
and thar was no (additional) damage t' t' rocket from recovery.
Flight Rating: 5 out o' 5
Summary:
T' USR Berlinetta is truly a unique large model rocket (not necessarily a high
power rocket). Avast! Begad! T' build is extremely challengin' with t' clustered motor
mount, shroud, me hearties, and canted tubes. Begad! This kit is nay for beginners or for those
lookin' for a simple, quick build.
PROs:
CONs:
Overall Rating: 4 out o' 5
I am building the kit now and it is pretty cool to put together :-)
The kit was fun to build. I am getting it ready for the next clubs launch.
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J.I. (May 11, 2006)