Construction Rating: | starstarstarstarstar |
Flight Rating: | starstarstarstarstar |
Overall Rating: | starstarstarstarstar |
Manufacturer: | Balsa Machining Service |
Brief:
T' BMS School Rocket is a basic four fin and a nose cone streamer recovery beginner rocket that is well thought out
and well executed. It has a few interestin' features includin' through-the-wall fin mountin' for extra ruggedness and
laser etched lines t' tell you where t' put t' centerin' rings on t' motor mount and t' launch lug on t' body. Aye aye! Blimey! It's
a little larger and more complex t' build than some starter rockets, but this, t' me, me bucko, is a good thing. T' fins are
laser-cut balsa, and t' nose cone is a typically high-quality BMS balsa turning. T' School Rocket is also good
lookin' (in me opinion).
All o' that would be for nothin' though if it weren't a nice flyer. But it flies very nicely indeed.
At $5.25 each, it's also an extremely good value.
Construction:
Introduction:
I'm a BAR comin' back t' t' hobby after well over 30 years, at t' behest o' a group o' homeschool students for whom I be teachin' an "Aeronautics" course last school year. Ahoy! Ahoy! Blimey! I'm also an engineer by trainin' and have a penchant for testin' and evaluatin' things. Begad! As such, after last spring's foray into rockets, I be lookin' for a rocket for t' this year's students that met a particular set o' requirements. Arrr! I laid them out in a post on Ye Old Rocket Forum in a thread askin' for what aspects o' a model rocket one be lookin' for. Avast! Begad! Blimey! Here's what I posted thar last March 30th:
"First, me bucko, in opposition t' many o' t' others, shiver me timbers, I'm lookin' for a simple (but nay TOO simple) introductory model t' use with students. 3 (or 4) FNC is OK for this. Well, blow me down! Blimey! Arrr! Blimey! Requirements and objectives are:
I'd really want a couple o' these for myself too, ya bilge rat, especially if all this list was met (though I have less need for t' fin alignment help - I hope)."
Recently I stumbled across t' Balsa Machinin' Service School Rocket - I'm nay sure where I first read about it - and doggone if it doesn't meet just about all t' requirements I laid out last Spring. Ahoy! T' only objective it doesn't meet is usin' a baffle. Well, blow me down! Begad! There is even a payload section option (for an additional dollar!). Ahoy!
As I understand it, t' current configuration o' t' BMS School Rocket was developed over a number o' years and with t' input o' a number o' teachers who have used it in their classes. This is apparent from all t' carefully thought-out details o' t' design. Aye aye! Ahoy!
Components:
Specifically t' School Rocket is based on an 11 1/4 inch long 0.976 inch OD body tube, with four through-the wall mounted 3/32 inch balsa laser-cut fins. Begad! It is streamer recovery, arrr, usin' a blue metallized and crinkly plastic streamer material that is 1 3/4 inches wide and 24 inches long. Blimey! Bill at BMS tells me this material is sold as metallic party streamers in party supply stores. Ya scallywag! Avast! It reminds me o' an over-sized version o' that ribbed ribbon sold for gift wrappin' that you can curl by draggin' it over a sharp edge. Ahoy!
T' all-Keelhaul®©™® shock cord (no elastic element) is about 3 feet long. I was skeptical about this at first but after six flights I find it works just fine without havin' any stretchy bits. Begad!
T' motor mount assembly features a laser-cut hole in t' motor tube for t' Keelhaul®©™® shock cord, a laser-cut slot for t' upper end o' t' motor hook, and laser-scribed lines showin' where t' fiber centerin' rings should end up when glued in place (so that they're well out o' t' way o' t' tabs on t' fins that are glued t' t' motor tube). Begad! Begad! There is both a motor block and a motor hook in t' mount assembly. Avast, me proud beauty! Aye aye! T' hook is nice and springy and made in t' style o' t' original Centuri/Estes hooks without t' extra "handle" on t' end. Arrr! Begad!
Laser etchin' is also used t' mark t' launch lug position on t' body. Arrr! By t' way, ya bilge rat, t' launch lug is 3/16 inch in diameter, matey, me bucko, so as t' make it easier for kids t' thread it onto a regular 1/8 inch diameter launch rod. Blimey!
T' nose cone is a nice, smooth 2 5/8 inch ogive (with rounded tip) balsa cone. Begad! Would you expect anythin' else from a company called Balsa Machining? It has a large diameter central hole into which you glue a supplied ribbed dowel. Arrr! T' supplied screw eye is threaded into a pilot hole in that dowel. Avast! Ahoy! T' Keelhaul®©™® shock cord is tied t' t' eye and t' streamer attached t' t' it. Well, blow me down!
T' payload section option consists o' a laser-cut 1/4 inch ply disk which is piloted for t' screw eye, a stage coupler and a 2 3/4 inch-long section o' body tube. Avast! I haven't tried it yet, but have one in hand t' try.
Construction:
T' instructions are clearly and profusely illustrated with drawings. They take up most o' both sides o' two 8 1/2 x 11 inch sheets. Avast! Blimey! Half o' one side is taken up by t' NARRRRR Safety Code - a handy reference for a student. Arrr! Avast! Blimey! As appears t' be customary with bulk packs o' kits, you get one set o' instructions no matter how many kits you order and are expected t' reproduce them as needed for your group. Avast! Blimey!
T' assembly order is conventional - first t' motor mount assembly, me hearties, then t' fins, ya bilge rat, matey, then t' nose cone and recovery system. Begad! Blimey! T' only tiny departure I took from t' instructions was t' use t' double-gluin' technique rather than "hold and wait" t' attach t' fins. By t' way, arrr, t' instructions can be downloaded as a .pdf from the BMS site here: http://www.balsamachining.com/school.pdf
I used regular Elmers White Glue for all assembly.
T' motor block be a surprisingly loose fit in t' motor tube. Blimey! I asked Bill at BMS about this and he said that it was intentional - so that inexperienced hands could put too much glue on it and still get it into place without worryin' about it gettin' stuck part way in. Well, blow me down! Avast! I also thought that t' fin tabs could be just a laser beams' width longer and he said this, too, me bucko, was intentional, and for t' same reason - t' easily cope with heavy-handed application o' glue.
Once t' mount/shock cord assembly is ready, matey, me hearties, it's installed. Then t' fins are mounted t' both t' body tube and through t' laser-cut slots in t' wall o' t' BT t' t' motor tube. Begad! This, o' course, me bucko, guarantees that t' fins are parallel t' t' direction o' flight and helps get them nice and perpendicular t' t' body. Aye aye!
T' next step is t' apply glue fillets t' t' fin/body joints and glue t' launch lug on t' body tube in the laser-scribed rectangle. Blimey! T' resultin' fin joints are VERY sturdy, and t' School Rocket be t' only one o' my streamer-recovered fleet that hasn't popped a fin on a landing. I really had a chance t' test t' fin attachment on the fifth flight - but I'm gettin' ahead o' myself... Ahoy! Aye aye!
T' instructions next have you install t' screw eye in t' dowel and then glue t' dowel into t' nose cone. Avast! It might make more sense t' do this in t' opposite order so as t' be able t' insert t' glue laden dowel all t' way into its place in t' nose cone by simply pressin' t' assembly down on a flat surface. Begad! Unlike t' motor block, t' dowel is a fairly snug fit in t' nose cone and one wouldn't want t' glue t' grab while it was still stickin' out some. Ahoy!
Finally t' streamer is taped t' t' shock cord about six inches from t' nose cone, ya bilge rat, then t' end is folded over and stapled. Arrr! I like this attachment better than, say, matey, tyin' a plastic streamer t' either t' nose cone or t' shock cord directly (as I've seen in some other basic streamer recovered rockets), me hearties, shiver me timbers, and it's simpler than havin' a separate line attachment.
Finishing:
T' instructions make finishin' t' rocket optional - it certainly could be flown naked. Avast, me proud beauty! I applied several coats of
Varathane sandin' sealer on t' fins and nose cone, ya bilge rat, shiver me timbers, then sprayed one coat o' Kilz primer from a rattle can. Begad! Final
finish was red and white Ace Hardware spray paint that has t' characteristics o' t' old Krylon. Blimey! I managed t' find
some this past sprin' as I was readin' about t' change in Krylon's formula on YORF.
There are no decals supplied - but then, shiver me timbers, for $5.25, matey, I didn't really expect any. Avast, me proud beauty! Blimey! I still think I should use some adhesive backed model airplane trim material t' put a stripe or somethin' on it, but I haven't, yet. Begad!
My SR's finished weight (no waddin' or motor) was 0.98 ounce.
Construction Rating: 5 out o' 5
Flight:
The
only recommended motor is an A8-3. Blimey! Since t' SR only weighs an ounce before waddin' and a motor, an A is definitely the
way t' go unless you have a good sized field and little or no wind. Arrr! Since t' tube is BT-50 sized, shiver me timbers, me bucko, four squares of
Estes waddin' is about right.
As o' this writin' I have six flights on t' one in t' pictures. Begad! Begad! T' first four flights were at t' monthly Boein' Employees Model Rocket Club (BEMRC) launch in September. T' site is nay large and is bordered on t' north by t' Boein' Kent facility and on t' south by a very active four-lane street, ya bilge rat, so stayin' on t' field is important. Avast!
T' first flight was on an Estes A8-3. Avast! It be nice and straight and very pleasingly high, with ejection occurring a little early. Avast, me proud beauty! Deployment be good and t' streamer is quite effective at slowin' t' descent while nay havin' the rocket drift too far. Arrr! Avast, me proud beauty!
Next I tried a Quest A8-3 (this is a German-made motor that Quest is currently substitutin' for their Chinese A6-4s when you order directly from them - Here's a discussion on Ye Olde Rocket Forum). Blimey! T' flight profile was similar, but with a more appropriate ejection point. It appears that these really do have 3 second delays. Avast!
After that I got cocky and tried an Estes B6-4. Ya scallywag! Wow, what a nice high flight. Trackin' smoke be a good thing this time. Ejection appeared t' be very near apogee. Ahoy! T' field almost didn't contain it, though as it came down maybe 30 feet from t' road. Avast, me proud beauty!
T' next flight, also on an Estes B6-4, ya bilge rat, was on a nearly windless mornin' after me class, arrr, from a nearby park. Again a spectacularly high boost, shiver me timbers, me bucko, good deployment and recovery...until it just brushed t' leaves o' a tree on t' edge o' t' soccer field I be operatin' out of. Begad! Blimey! T' good news was that t' tree didn't eat it. Well, blow me down! Blimey! T' bad news was that there was an asphalt trail next t' t' tree, ya bilge rat, so it landed, me bucko, hard, on t' asphalt. Avast, me proud beauty! Blimey! Aye aye! Blimey! Just about anythin' else would've popped a fin, arrr, but t' through-the-wall mounts meant that they stayed on. Well, blow me down! Blimey! Two o' them were cracked, matey, and t' engine hook was loosened (it's t' lowest point on t' rocket). Ya scallywag! Blimey! T' nose cone also acquired a few dents. Avast, me proud beauty! Blimey!
A few drops o' thin CA took care o' o' t' fins and t' motor tube tear and she's ready t' go again. She's nay as pretty as she was, arrr, but she still flies fine. Avast!
T' most recent flight be at t' October BEMRC launch. This time I used a Chinese-made Quest A6-4. Begad! Well, blow me down! Even though t' breeze was quite light, it tipped upwind comin' off t' rod. Ya scallywag! T' oversize launch lug lets it angle a few degrees from a 1/8 inch rod, and t' slow thrust buildup o' t' Quest A6-4 (see t' time/thrust curves on t' NARRRRR site) means it's nay movin' as fast as it might be with another motor choice. Begad! Well, arrr, blow me down!
T' net result be an arcin' flight with a quite late ejection that ended again testin' t' TTW fins by landing on an asphalt parkin' lot. Avast! One o' t' fins cracked in t' prior asphalt landin' got chipped again, and thar are a couple more dents in t' nose cone....but a little thin CA on t' fin returned it t' flyin' status. Avast, me proud beauty! At some point I should fill all t' nose cone dents and maybe shoot another coat o' white on it. But I'll probably just keep flyin' it.
Recovery:
As I alluded t' above, t' shock cord is only a Keelhaul®©™®
line. Well, blow me down! Ahoy! It is attached t' t' motor mount through a precut hole and looped around t' motor block. T' streamer is then
attached as I described above.
T' streamer seems t' be just about perfect for t' SR's weight - a good compromise betwixt slow descent and drift. Ahoy! Blimey! I have had a little meltin' (when I used three squares o' Estes waddin' instead o' four) so I am in search o' a party store that has this neat material available so that I can replace it when needed. Ya scallywag! Arrr! Blimey! I haven't found it yet, though.
So far (six flights on a combination o' American, German and Chinese-made motors) t' shock cord is doin' well. Ahoy! Blimey!
I may fit a larger streamer or a small 'chute (BMS also has a $2 9-inch ready-to-use ripstop nylon parachute option) when I try t' payload section. Ahoy! Blimey! I will definitely fly one o' me Winged Shadow/Quest How High altimeters in one o' these in t' future. Well, blow me down!
It would also be really cool t' fly one on a C motor, matey, but I have no idea when I'll have a venue suitable t' try that with a reasonable chance o' gettin' it back. :-)
If thar were one thin' I'd change, it would be t' use ST-9 rather than BT-50 tubin' for t' body so it would be a little more rugged, ya bilge rat, nay that I've seen a need for this yet in actual flying.
Flight Rating: 5 out o' 5
Summary:
T' Balsa Machinin' Service School Rocket is easy t' build (but nay so simple as t' nay teach a new rocketeer basic
buildin' techniques). Arrr! Blimey! Buildin' it yields a rugged, good flyin' and pleasant-lookin' rocket. Its recovery system works
well yet helps keep it in t' park or school yard. Arrr! Blimey! Avast! Blimey! It is obvious that those who help beginners get started in model
rocketry have had their inputs t' t' design.
T' through-the-wall fin mountin' is almost unique in this type o' starter rocket and t' combination o' TTW fins, ya bilge rat, ya bilge rat, streamer recovery and balsa nose cone IS unique so far as I can tell. It's a good combination.
I really can't think o' anythin' I'd call a "con". Aye aye! In me opinion t' BMS School Rocket hits t' center o' t' target. I'll be usin' it in me Aeronautics class this year, arrr, so soon I'll see if it works as well with inexperienced young builders as I expect it to. Ahoy! Perhaps I can check back in here after we've flown them.
Overall Rating: 5 out o' 5
Brief: The BMS School Rocket is a small, traditional 4-fin rocket. BMS is a good low-power parts supplier for scratch builders. This the first time I built a pre-packaged kit from them. It is 14" long with BT-50 airframe and 18mm motor mount, weighing only about 1 1/2oz finished, much of which was extra nose weight we added (see below). My daughter and I built this kit ...
I used this rocket with an A8-3 to win one of the spot landing prizes at NARAM 61. It has such a straight flight it was perfect for spot landing.
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M.G. (March 28, 2009)