After having the BlueCor material on hand for almost a year, it was finally time to do something with it. Thanks to Rod Baron & Ron Teke of SPARCS for demonstrating just how well flat pate airfoil airplanes can fly; & thanks to Keith Brown for the neat CD-ROM type motor I ended up with at this year's SPARCS Christmas Party gift exchange...
I needed something on which to fly this impressive motor, and after seeing Rod's BlueCor planes flying so impressively earlier this year, and then seeing Ron's Red & Black BlueCor plane flying just Saturday morning (Dec. 18th) at Farmer's Korner, & then talking a bit more with Keith, I decided that it was time to finally get busy!
(Winter is building season for me- it's when I take a bit of time now & then to work on a project. So I thought I'd pass along a few details on how easy it can be to build one of these airplanes. If it gets some of you interested in building your own, then my time writing up these brief notes will be rewarded!
(There are no 'plans' as such- it doesn't really take any- but I did lay out cutting template paterns on poster board so that more parts can easily be marked. SPARCS Members can contact me if they are interested in building one of these airplanes after the flight testing is actually completed.The building process is very straight forward, and will be well illustrated in these photos & text. More photos will be added to this page after I complete the next stage; the ends of this page has the latest updates.)
Keith said that a 12 Ounce plane would have great performance with the 16 Ounce thrust motor,(& I certainly agreed!), so that was the target weight limit if possible. BlueCor fan fold panels are 23-1/2" between folds, and 50" wide, so length of the fuselage horizontal panel was dictated at the 23-1/2" length by the material. This is what should be considered as 'close-coupled'; a longer tail moment would result in a smoother flying aircraft... but hey, I'm the guy that enjoys flying the "Short Hare"... this layout is not as close-coupled as that plane, and I have a lot of fun flying it...! After doing a rough layout on graph paper, I started my final layout directly on the foam sheet. I cut the bevels on the aileron / wing joint in the main cutting session, and merely swapped the ailerons to the opposite sides to use them as they came out.
The result of my efforts it a total of about one day are in the photos I've attached.
The entire wing, horizontal fuselage member, and horizontal stabilizer are kept together, cut in one continuous piece. The Vertical fuselage is longer by another 2-1/8", surrounding the motor. Fuselage finished length is 30" from the front of the prop mount to the trailing edge of the elevator.
Wingspan was designed at 30", with a single 1/8" diameter CF tube wing spar (which was installed in a slot made with a Dremel cutter bit in a Dremel Tool equiped with a router head setup. I installed it in the 1/8" deep slot with 5 minute epoxy.
The motor mount ( a 5/16" diameter dowel to insert into Keith's motor mount) was epoxied in place next. (I actually replaced the one in these first photos with a longer one that extends back farther through the core of the fuselage past the battery pack mounting area, to firmly transfer the motor thrust and the battery weight to the rest of the airframe.)
The top fuselage piece was then epoxied in place, (using one toothpick piece as a locating pin close to the tail to help alignment while the epoxy set up.)
The elevator was then tape-hinged to the horizontal stabilizer (after having the center section reinforced with some 1/2" wide .007" C.F. material.) I use Scotch multi-purpose transparent tape for hinging purposes, applying the top side tape first, then another layer from the underside second, so that the tape pieces join to each other in the middle of the hinge line.
The lower fuselage was epoxied in place next, again using a short toothpick piece as a locator pin at the tail end.
The rudder was next reinforced with CF material in the control horn area, then tape-hinged to the vertical stabilizer.
Finally, the Ailerons were tape-hinged to the wing.
I plan to glue the 1/32" birch plywood control horms into place in custom slots through the BlueCor foam. Ordorless CyA was used & worked well for this job. (Since I'm intolerant of solvents, but like quick setting time, the epoxy and the odorless CyA glue are my choice for building. I'm also using a bit of low temperature hot melt glue in certain areas; it's likely only suitable for places where you can work fast before the glue cools too much to bond well. I'll use 1/32" music wire for aileron control linkage ends, attached to the ends of .060" solid CF rods for all control rods.
Result?: Airframe is at about 3-7/8 Oz, before painting.
So this is the progress I made in less than one day, starting from scratch & laying it out before starting the cutting.
[Once the painting was completed it was 1/2 ounce heavier, ready for the control system installation.)
I tested some bright spray paints, and confirmed what others say; only certain products can be used on the BlueCor without damaging the material. I had a 3 Oz. can of PACTRA spray paint designed for painting polycarbonate bodies on RC cars; it did not attack the BlueCor's plastic surface film, but did bond well to it. (It does attack the core foam, however, so use it carefully & don't try to pain too 'wet' ; use mist coats with the spray can held at a distance, and let dry between coats.) I used this on the entire lower surface of the aircraft.
I used the inexpensive CERAMICOTE acrylic paints from WalMart's craft section in Purple and black to dress it up a bit on the upper portion; these colors were applied with a brush. The result isn't too hard to look at...! It's definitely highly visible from below when it's in the air!
I used three of the inexpensive Blue Bird .21 Oz servos, installed with low temperature hot melt glue.
I custom made 1/32" birch ply control horns, and glued them in place with odorless CyA glue.
I installed a .3 Oz. GWS 6 channel receiver, then mounted the 1-1/2 Oz motor, 1/4 Oz. Phoenix 10 ESC, & a prop. With a 3 cell Li-Ion 1200 mAH battery which weighs 4-1/8 Oz, the completed aircraft is ready to fly at 12-1/8 ounces. I used an APC 9x4.7 slowflyer prop for the first flights, then later switched to an 8x6 GWS slowflyer propeller; this motor performs well on this prop on 1 3 cell Lithium battery.
Flight tests were finally flown on Sunday, December 26th, 2004 in a small area just off the end of my driveway; this plane is flying great, and does not need a lot of area to fly. It is close-coupled enough to flat spin nicely; because of this ccharacteristic, it's definitely not a trainer! But it flies inverted nicely, rolls smoothly & loops tightly, and glides under reasonable control with the motor off, for predictable landings in a modest amount of space. (A flat plate wing is certainly not intended as any form of 'glider', but power off landings are essential on a no-landing-gear aircraft, so I'm very satisfied with the no-power maneuvering capabilities.
Note: 1-18-05: I'm now using a KOKAM 1500mAH LiPo battery to fly this aircraft; it's producing more RPM than than it did when using the surplus Li-Ion cells on which I first flew it.)
They say 'A picture is worth a thousand words", and since I type slowly & do not have time to write up a lot of the details right now, I'll simply offer the following photos.
Balance on a flat plate winged aircraft works well at about 29% to 30% of the wing chord. I had installed the C.F. tube spar at 30% of chord, and flying with the balance on the spar at the 30% location works well.
Receiver Antenna: this is taped on top of the wing, rather than draging out behind.
Battery Update 1-18-05: the location of the battery was the last item I dealt with, to finalize the balance. It is now held in place in it's cutout with a couple of clear plastic covers (made from salvaged packaging materials) which are taped in place on either side. One side is tape hinged, so that it can be swung open for battery placement / changing, and taped shut for flight.
LINKAGES: Note the 'safety pin' front ends on the control linkage rods; these are formed from 1/32" music wire, and installed on the ends of the C.F. rods with heat shrrink tubing. Once final trim alignment is adjusted with the radio trims centered, a drop of CyA glue locks these links to the rods. (The other end uses a short Z bend coupler, anso heat-shrink & glue mounted to the control rod.)
Parting notes: For a novice pilot, making a longer fuselage would smooth out the handling, but you would have to use a different layout, with a separate wing, and separate fuselage members, to extend the length. (Keep in mind the dimensions of the fan-fold sheet.) In the process, you would likely loose the flat-spin capability, and find a bit smoother handling.)
After installing the spar with ordorless (foam safe) CyA glue the 10mm square motor mount stick is glued in place; it extends back to the wing spar. The top surface of the motor mount stick is placed flush with the top surface of the wing section of BlueCor- it extends 1/8" below.
Once the vertical fuselage section is split lengthwise and trimmed out to match & clear the motor installation, the top piece is glued in place. Toothpick sections are used as 'locator pins' when gluing the top section in place; (match the trailing edges at the hinge lines for the elevator and rudder.) Once the 5 minute epoxy I used was set for a few minutes, I did a final fit on the ailerons and then tape-hinged them in place. The elevator was tape-hinged in place next. (Tape top first, then bottom after.)
Above is a closer view of the upper nose section; the motor stick was installed at an over-long length, then trimmed back to leave the motor recessed enough to be protected by the lower fuselage section once it is all together.
After fitting the lower fuselage section to the under-side of the horizontal wing section, I added 'doublers' on either side of the lower forward fuselage section, from the nose back to the wing spar area. This will make this area, which not only carries the flight battery, but also inevitably takes the most wear & tear on landings, much more durable. It also brings it out to a full 3/4" thick, so the 3 cell KOKAM 1500 LiPo battery I am using will fit within this thickness, and not protrude out the sides. I'll determine the battery location last as the final 'balancing act', and make a snug fitting cutout. For winter flying, a clear plastic cover will be permanently taped in place on one side, and another clear plastic battery compartment cover will be tape-hinged on the other side, and closed with tape to keep the battery in place.
(Protecting LiPo batteries form damage on landings is a high priority!) For warm weather flying, the solid cover panels may be modified to allow for battery cooling air flow; but for winter flying here in the central Colorado Rockies, keeping the battery warm enough to perform well is an important consideration.)
You can also see the toothpick 'locator pins' I installed which will index the lower fuselage section into it's exact desired position while the epoxy glue is setting.
Once the epoxy had set, I used a bit of low temperature hot melt glue to lightly reinforce the forward joining area. Then I did an overlay along the bottom forward edge with 1-1/2" wide cross-fiber nylon filament tape. 3/4" wide nylon filament tape is used on the aft lower fuselage bottom edge to add durability.
The photo above shows the BP21 motor installed, mounted on a trimmed down GWS motor mount (which is included with the BP21 motor.) You do have to figure out where to drill the lower two holes for mounting the motor to the mount, but it is a good fit, with the prop shaft center line just above the upper surface of the motor mount stick. I trimmed away as much excess plastic as possible; the results are shown in this photo.)
good deals I'm aware of as of 1-31-2005
BP12 Brushless Motor with 18 Amp Brushless ESC combo: $56.95; From Clay's Hobbies on this page
Also best price on Bluebird BM306 micro servos for $13.99 each: from Clay's Hobbies on this page
Long range light weight 4 Channel Receiver: 1500 foot minimum range, auto shift detect: Plantarco DSP4 receiver (& order a crystal seperately) .21 Oz available from Balsa Products
KOKAM 1500 maH 3 cell 11.1 volt Li-Poly battery pack with Deans Ultra connector: (Also offer GWS pico receivers with ~600 foot range; and offer the Electrifly Polycharge LiPo Charger for $24.95) available from Aeromicro