Above: This is the Voyager, a 36" span aerobatic aircraft built from Bluecor PP
Wing Chord: 12" at center, 8" at wing tips
Wing Area: 360 square Inches = 2.5 Square Feet
Flying Weight ~17.75 Ounces (after all modifications were completed and all of the colored trim was applied)
Flying weight with the EPP floats mounted: 22.5 ounces
Wing Loading : 7 Ounces per square foot without the floats; 9 Ounces per square foot with the floats mounted
Overall Length: 34.5"
Elevator Span: 16"
Materials Of Construction: Bluecor PP with internal Balsa Spar Structure, implementing a KFm3 variant airfoil
1mm solid CF rods used in opposing pairs as structural stiffeners throughout fuselage and tailgroup members (.043 ounces per 1 meter length)
1.5mm CF rods used for elevator and rudder control rods
Motor Used: Turnigy C2826 1500Kv Brushless Outrunner
ESC : Turnigy 20 Amp 'Super Simple' programmable
Battery: 3S 1050 mAH Rhino LiPoly
Propeller: APC 9x4.7 is my favorite - static current load = ~15.5 Amps = 175 watts power (Or Use APC 8x6 for higher speed flight)
Power Loading = 160 watts per pound
Radio Receiver: Corona 4 Channel Single Conversion
Transmitter Used: Airtronics RD8000
Servos: two Turnigy TG9 for elevator and ailerons; 1 HXT900 for Rudder
Optional Floats: 1.3# density solid EPP; ~24" L. x 3" H. x 2-3/8" wide at the hull's lower planing surface; 10 degree side cut
11-08-2009 - first flights. 11-10-2009: The Voyager is flying very nicely! It's very stable to launch from an under-handed hand launch. It also handles quite predictably at low speeds and in power-off glide, but since it has a flat-built wing, you do need to fly it all of the time; there is no dihedral to give it any positive roll axis stability.
The C2826 motor is flying the aircraft with good authority. (After the initial flight, I added some shim washers to shift the motor incidence, to give it more right thrust and less up thrust; there is ~2 degrees of up-thrust or less after this adjustment. This positive motor incidence counter-balances the rotational moment created by the motor being mounted above the center line of the wing.) The Voyager handles higher speeds easily and smoothly when flown with an APC 8x6, but it was leaving the area very quickly!!!- I prefer how it handles with the APC 9x4.7 SF prop; as you can see from the video, it still covers a lot of sky quickly at full throttle; yet it rolls cleanly at half throttle, and handles very responsively at very low airspeeds.
Aileron and elevator response are clean and smooth. The large rudder will be great for water handling on floats, but required mixing R>E to eliminate an opposite roll response to heavy rudder deflections at high airspeeds. It can be flown into and out of some nice flat turns and spins, as well as doing about all of the inside & outside aerobatic maneuvers you can think of. It will recover very quickly from any insane attitude that you put it into. Since the Voyager has a flat-built wing with neutral roll stability, you still have to fly it out of whatever you attitude you fly it into, but for experienced pilots, it's a very good performer. It also flies inverted easily with very little forward pressure on the elevator stick to hold it there- less elevator control input is used than is needed on many flat plate wing designs to hold in inverted flight attitude.
The wing on the Voyager is built from the Bluecor PP, ~6mm thick- the type with the plastic film on both top and bottom surfaces; It uses the fold between two panels as the leading edge, which is further heat-shaped after the wing is built out.
Wingspan is 36" and the chord tapers from 12" at the center to 8" at the wingtips. The center 1/3 of the wing has a ~1/2" tall main balsa spar, which is tapered to just under 3/8" tall at the wing tips. So maximum wing thickness in the center 1/3 of the wing is roughly 1", or 8.3% of chord. The high point of the airfoil is at roughly 30% of chord; The primary step runs from 50% of chord at the wings center, to 40% of chord at the wing tips. The Voyager handles very well with the balance / CG at about 32% to 33% of chord.
One of the somewhat unique features of this particular stepped airfoil wing build technique is how the secondary step layer is set at an angle; the photos of the build process show it better than I can describe it. This keeps the step height minimized to a maximum of ~6mm- the thickness of one layer of the Bluecor material. Thickness of the secondary step layer is thined near the wing tips, in an effort to keep drag to a minimum in this critical area.
Above is the fuselage cutting template laid on a 1" grid cutting mat.
I started work on the new " VOYAGER" aerobatic float plane design on the afternoon of November 2nd, 2009. This is another wing design which utilizes the 'Kline-Fogelman' stepped discontinuities on the wing's upper rear surface. These are structures which are theorized to minimize air separation from the wing's surface when implemented properly. When building with the DOW Bluecor fanfold foam, these types of stepped discontinuities are easier to implement than when building with other materials and airframe construction approaches. The Slim Beagle, Dancer, and Me163-e Komet designs feature lifting airfoil wing designs which all effectively implement these "KFm" stepped discontinuities in various ways.
The Voyager's wing and horizontal fuselage are laid out in one continuous piece directly on two joined panels of Bluecor fanfold foam with a fine tip sharpie pen, with the fold between the two fanfold panels forming the leading edge of the wing. The upper wing surface layer is firsst cut from the attached upper panel. A narrow (~2" wide) secondary step layer is cut from the material left after cutting the upper layer, so that it follows the contours of the first cut easily.
Above: The layout for the upper layer is where I started on these joined panels of foam; it's center trailing section will be extended later in the build all the way to the rudder hinge line. I used straight-edges, rulers, and french curves to end up with the sweeping curves you see in this build.
Above: The primary top step runs from 50% of chord at the center of the wing to 45% of chord at the wing tips. I slip the cutting mat in between the layers of foam so I can cut only the upper layer first.
Above: Once the excess is cut free and removed from the left section of the main upper wing layer, it is possible to complete the layout on the lower layer of foam.
Next, I work from the material I just cut away to form the secondary step layer, cutting the secondary step panel that is roughly 2" wide- refer to the photos; it is cut so that it will extend 1/2" under the edge of the upper layer. The trailing edge of this secondary layer extends back behind the primary step by 1-1/8" at the wing tip, widening to 1-3/8" just above the inboard end of the aileron.
Above: I have cut away the left aileron, removing a wedge of foam to allow plenty of room for travel when it is hinged with the tape.
Above: Next, I fit the aileron back in it's space, leaving a 1/32" gap so that the tape hinging will not cause binding of the hinge, and weight down the sections so they do not move while I apply the 1/2" wide Scotch transparent tape as hinge tape.
Then I proceed to complete the cutout of the right side of the wing panels.
Above: Next, I position the wing so that I can easily apply the 3/4" wide transparent hinging tape to the under-side of the hinge line. (This photo shows doing both sides at the same time.)
Above: This shows the state of progress on the main wing structure after these steps. It is shown sitting loosely on top of the EPP floats.
Above: Some tapered foam strips were cut and glued in place with hot-melt glue to raise the leading edge of the secondary step piece up to where it will contact the underside of the upper layer when everything is completed. Once the tapered strips are in place, the secondary step pieces are thinned at the rear ends and at the outboard ends; they are then also glued in their places.
Above: Another cross-filler piece is cut to fit, then glued in place.
Above: The balsa spars are being epoxied in place. First, the 1/4" square balsa spar is placed; it's center is ~1/2" behind the fanfold foam's fold at the center. by placing this spar in this location, the foam of the lower layer is curved upwards towards the leading edge, resulting in a fair amount of 'Phillips Entry". I also do some slight rolling and bending of the front ~1" of the lower panel's foam to help form this curvature. The outer ends of this front spar are curved back away from the leading edge another 1/4", to end up with a slightly thinner leading edge near the wing tips when assembly is complete. (Some tapering of the outboard ends of this front spar might be appropriate on future builds to keep the wing tips from being too thick; arcing the outer ends of this front spar back away from the leading edge of the wing does result in the same affect.) Pins were used to hold this spar in place, and lead weights were set no top to hold it in place against the foam while the 5 minute epoxy set up.
The main spar is 1/4" thick firm balsa; it is 1/2" tall across the center 10" of the wing, while each end is then tapered down to just under 3/8" tall at the ends. The center is actually arced back slightly, relative to the outer ends. In the photo above, it's weighted down while it's epoxy is setting.
Above: To provide more structural support for mounting floats directly to this wing, a third spar was added; This one is 1/4" thick x 1/2" high balsa, 17" long. It's outer ends are tapered down on the outer 3-1/2" to match the wing airfoil contour.
Once that spar was set, filler blocks shaped from 1/2" x 3/4" balsa stock were added into the four locations shown. These offer float mount options through these hardened areas.
Above:The last of the foam blocking is all in place in the rear center area of the wing. It's now ready to have the 12 minute epoxy applied to the tops of all of the interior structure so that the upper foam layer can be glued in place.
Above:Once the epoxy was mixed and applied, I used a LOT of assorted pieces of lead to keep the upper wing surface firmly held in place against thwe interior structure while the epoxy set up.
Above: This is the "first cut" of the upper fuselage core layer, contoured to follow the top surface of the wing. It is simply set in place for this photo. It will have doublers and some structural reinforcment added to solidly tie the motor mount bulkhead into the airframe. (Note: the upper fuselage profile was later modified from what is shown in this photo.)
Above: Here is the completed elevator; it is 16" in span, and 4" deep behind the hinge line. I have used a 1/32" soldering iron tip to make the tight slots for the 1mm solid C.F. rods which are inset flush with the surface of the Bluecor to form the joiner and to stiffen the entire elevator. The center narrow section was then wrapped with two layers of 3 mil document laminating film to furtherr stiffen this area; the film was applied with a covering iron at about 290 degrees F.
Above & Below are two shots of the final upper fuselage shape, laid over the 1" grid for scale.
Above:After setting some temporary spacers between the wing and the floats, I decided I could swing a 9" diameter prop with good clearance if the motor was mounted with it's shaft at about 2" above the center line / chord line of the wing; this was lower than where I'd first considered, so I reshaped the nose of the fuselage. I also lowered the overall fuselage upper profile line back to just in front of the vertical stabilizer. Next, I began the process of making the shallow slots and of installing the 1mm CF rod stiffeners in the upper fuselage. These will eliminate flex in the fuselage; also, the forward CF rods will be tieing the motor mount ply bulkhead back into the entire upper fuselage, as well as tieing it down into the leading edge of the wing.
With the lower motor mounting position relative to the wing, I have decided to start with the motor mount bulkhead set at about +3 degrees incidence, relative to the bottom surface of the wing. This can be adjusted further if desired after test flying by adding shim washers under the legs of the motor mount.
Above: This is the ~43 gram motor I will be mounting on this aircraft; it is a Turnigy 2826 1500 Kv motor. A 9x6 prop is set in place for this photo. I'll use a Turnigy 'Super Simple' 20 Amp programmable ESC.
Above: Ready to fly with 3S 1000 mAH battery pack at 16.5 ounces, for a wing loading of 6.6 ounces per square foot.
Above& Below: Once the location for the Rhino 3S 1050 mAH LiPoly battery had been determined during the test flying, a snug friction-fit cross slot compartment for the battery was created, and two more doublers were prepared. Two more 1mm CF rod stiffeners were also inset into the Bluecor before this last layer of doublers was glued in place.
Above: This battery carrying compartment allows the battery to be carried directly on the lateral centerline.
Above: The result leaves very little of the battery protruding from the sides of the 5 layer thick nose section, so drag is minimized with this modification.
Flying weight after all of the trim tape was added and the last nose modification was completed is now at 17.6 ounces, for a wing loading of 7.0 ounces per square foot.
Follow-up flight report: The Voyager handles even smoother and more predictably with the battery installation modification completed!
Above: more trim added to the tail for better visability. The wing tip plates have also been enlarged on their lower edges by about 7/16". This seems to improve the flight tracking stability.
Solid EPP floats can perform very well for both water flying and snow flying. They need adequate structural strength to handle the takeoff and landing structural loads, and they need to be sealed to prevent water from getting into the foam cores.
The photos below show how I set up to cut them out with a bandsaw.
The upper right piece is one of the cutoff pieces from the T-Ball's set of floats.
First cuts are made with the band saw's table set at zero degrees.
[NOTE:] Depending upon how you plan to mount your floats to your aircraft, you may need to add a top center spine for stiffness and other structures for mounting. Keep in mind the fources which may be exerted on these floats during rough landings, and build in enough strength to handle these forces and the mass of the aircraft on which they are being mounted.
12-16-2009 Update: The KFm3 winged VOYAGER aerobatic aircraft is starting to get it's floats completed and mounted. Here's a quick look at the start of the process. I'll post updates as this project continues.
Next step is to cut the tops of the riser blocks to follow the lower wing surface contour, and to provide the 2.5 degree positive wing incidence. The riser blocks will then be aerodynamicly streamlined somewhat.
Above: Starting the setup for the KFm3 VOYAGER's floats. These floats have an overall length of 24" on a 35" long fuselage; (wingspan is 36")
Above: The riser blocks will be cut to give the wing a 2.5 degree positive angle of attack, relative to the float's bottom planeing surface.
Above: Wide stance setup; interior wing structure was blocked out with balsa filler blocks between the wing spars to provide solid attachment for these solid EPP floats mounted in these locations.
Above: Voyager's floats : top mount plate and four 1.5mm CF rods per float installed to attach these floats into the wing structure, and to transfer loads deep into the EPP foam.
Above: Four #6 x 1.25" screws run down through wing structure into each float's mount plate- easily removable when desired.
Above: Underside of wings show clean mount, no extra struts or braces needed. Float system, with 3 mil laminating film and mounting hardware adds a total of only 4.75 ounces to the VIKING's flying weight. Final flying weight on floats = 22.5 ounces
Above: Voyager on floats, ready for snow flying; Works GREAT- ~30 takeoffs & landings on it's first outing, no problems at all. (Water flying delayed until we get down into AZ later this winter.)
The Voyager is flying great with the floats mounted, flying from our wind-packed snow. First takeoff was smooth and uneventful- just as it should be. Takeoff run is about 15 feet before it's airborne. I added about two or three clicks of down trim on the elevator- that's all it wanted.
With 4.75 additional ounces and the added profile drag of the floats, the flight speed is not as fast as when flying without the floats, and while the vertical climb performance is still very adequate, it's not in the 'unlimited vertical' class with the motor / prop / battery that I'm flying. Rolls to either left or right are still smooth and predictable, and (as would be expected), the roll rate is reduced form what the Voyager had before the floats were mounted; they do have a lot of surface area, after all.
Glide is still very impressive, and landings really need to be dead-stick to ever settle in a reasonable amount of room; with low throttle, it'll continue to glide for a lot of distance. Aileron response is very clean down below reasonable deadstick landing speed. So dead stick landings are easy & fun- just what you would want.
Rudder response is very good; without the floats mounted, there is some adverse roll response to rudder deflections on the VOYAGER, so I had added in the rudder > aileron mix to balance this out. With the floats mounted, I'm finding that I need less on this mix- there's less adverse roll response to rudder deflection now.
Doing takeoffs and landings and touch-n-go's is a lot of fun with the Voyager on floats on the snow; I did about 30 this morning in a modest amount of time.
These solid EPP floats are covered with the 3 mil thickness document laminating film; it comes in up to ~27" wide rolls. This covering, with an extra layer on the float hulls for durability, added 7/16 of an ounce to each float- very reasonable for a totally waterproof and very durable float covering!
(LaminatorWarehouse.com is a good source for the CP product. This is very similar to what Lee is now using, & what the Slope Combat guys from Colorado started referring to as "The New Stuff" a couple of years ago. It's available in several different thicknesses- I use the 1.7 mil for lighter jobs, and the 3 mil for the applications which need more toughness.)
Balance was shifted back only about 1/8" with the floats mounted, so adding these floats is a ~ neutral proposition. The VOYAGER flies great with a wider range of CG positions, so that was not an issue. There's plenty of vertical stabilization in the airframe as designed- absolutely no need for any changes in that respect.
So I'm VERY satisfied with the VOYAGER on the EPP floats- the entire design and installation is working as planned, and promises to be very resilient and durable. EPP is great stuff for many applications, and this is one of them!:D
The FUN continues!!
[5-28-2010 Update:] I finally had a chance to fly the Voyager on floats from water - and it's performing superbly! It tracks well on the water, comes up on step smoothly and easily, and lifts off the water very predictably. Landings are also smooth and predictable. When taxiing on the water, with a bit of throttle advance it assumes the 'hump' attitude, with the nose higher and the tails of the floats down; when in hump attitude, the air rudder serves well as a water rudder. Once you power up a bit more to come up on step, the aircraft planes in a level attitude, with the tail well clear of the water.
With the generous side cut on the EPP floats, there is very minimal spray from these floatsa. And with the wide-stance setup, the Voyager is very stable on the water in cross-wind conditions.