The Great Planes Dazzler is what I would describe as a second generation fun-fly type airplane. When these special-purpose models first showed up, they were primarily built of thick open structure unsheeted wings, flat stick structure tails, oversize control surfaces, profile nose sections, and carbon fiber tail booms. The mission at that time was to rapidly perform wild gyrations at low altitudes while flying slowly, and to compete in timed events. Although those models and events eventually became very popular, the airframes were probably too specialized for general sport flying. The Dazzler is sort of a hybrid between the original fun-fly model and the traditional sport model. It has the thick wing, the light tail, and oversize control surfaces, but instead has a conventional fuselage. Also, the entire structure is somewhat more robust than the truly competitive fun-flyer. The result is a design which features the best of both worlds.
Ive been flying RC for a long time, so I have a natural inclination toward converting glow powered models to electric power. As I see it, there are four major concerns: 1) picking a design that fits your flying style, 2) choosing the proper power system, 3) determining how to install the electric power components, and 4) saving as much weight as possible. Obviously some glow powered planes are more adaptable to electric conversion than others. Frankly, I had some initial reservations about the Dazzler. It is a style of model that is meant to have a low weight and high power to haul around a rather high drag configuration. However, the conversion is likely to have greater weight and less power, and there is nothing we can do to reduce the drag of that fat airfoil. The challenge is to find a happy medium between expectations and reality.
I think we have a pretty good combination here. I used the Electri-Calc computer program to sort through some alternative power systems. I chose an Astro Flight sport wind geared 15 with a 11x8 prop on 14 cells to approximate the power of a glow .32 engine. This is somewhat beyond the manufacturers recommended configuration for the motor, but within its capability. The airframe is already designed for minimum weight, and I could not find any place to make a significant improvement. The completed airplane is a pound over the manufacturers target, due to the battery weight. I used two separate 7 cell packs to work around the wing that goes through the fuselage midsection. The plane has a large access hatch on the bottom of the fuselage, and I was able to get all the gear inside, without having to relocate any of the servos. With good throttle management, the Dazzler can be flown just about like it was intended. It is moderately fast, and very maneuverable. The Dazzler's flight performance has exceeded all my expectations.
The Dazzler kit uses very conventional materials. The ribs and fuselage sides were on die-cut balsa sheets, 1/16" and 3/23" respectively. The formers were on a die-cut 1/8" light plywood sheet. All of the die-cutting was clean. The 1/4" aircraft ply firewall looked to be cut on a saw. There was lots of 1/4"x1/2" balsa strip wood for framing the control surfaces plus some 1/4"x3/16" for internal bracing. The wing spar material was 1/4"x1/4" basswood, the trailing edge was 1/4"x3/8" balsa, and the leading edge balsa stock was a robust 5/16"x1-3/16". All the balsa strip stock was a nice medium density, and most pieces were straight. There were several light density 1/16" balsa sheets for the wing leading and trailing edges and turtledeck.
There was a nice heavy gauge clear canopy, wrapped in tissue. The pre-bent 5/32" landing gear wire was tucked in so it did not shift around. The included pushrods were 1/16" wire in plastic tubes. The hardware bag contained an ample supply of nuts, bolts, horns, clevises and such, plus a large strip of flex hinge material. The rolled plan sheet appeared to be generated on a CAD system. The 20 page instruction booklet was well organized, with numbered construction steps, and lots of clear photos. I would rate the overall kit quality very high.
Now heres a step that you dont see in every kit review, but is part of an electric power conversion. I started by laying out my system components on the fuselage side view of the plan. I mounted the geared Astro Flight 15 in a Stitzer Model Design Aero Vee mount, and placed it where the glow engine would go. I found a good match of thrust line and motor mount position, even the length was about right. Of course, the flat plate firewall did make motor positioning pretty easy.
Next I placed a couple of 7 cell battery packs end-to-end from the firewall to the fuselage midsection. Uh-oh, the wing goes through there. I decided that the minimum modification would be to remove the bottom leading edge sheet and shave about a 1/2" from the leading edge spar, but not remove any of the lower spar. Thus there would be battery clearance right through the fuselage, but not in a perfectly straight line. With this modification I was satisfied that the two 7 cell packs would fit with ample room to spare for other components. I also decided to make the bottom hatch more easily removable by using a tongue at the front and Goldberg hatch latches at the back.
I planned to put the speed control in the fuel tank compartment, and the receiver, its battery and two servos in the mid compartment. Final locations would be based on achieving the proper center of gravity. It is common to relocate the servos further aft, so I planned to leave off the bottom sheet until I knew for sure. Later, I found that I did not need to move them. I expected to modify the construction sequence a little along the way, to keep my options open.
The Dazzler construction approach is pretty conventional. The permanent mounting of the thick wing through the fuselage is the most obvious departure from the norm. Some of us will remember this technique from our controlline days. I used the three viscosities of Great Planes Pro CA glues for all construction except the firewall and wing joiners, where I used their 30 minute epoxy. The overall construction process moved along rapidly. The parts fit was very good.
The booklet starts with framing the horizontal and vertical tail sections and the ailerons, using 1/4"x1/2" and 1/4"x3/16" balsa strip stock. The tail pieces also use corner gussets. These built-up structures were very light, yet strong and warp-free.
The wing panels are next. A section of the plan is to be cut out so the wing tip could be taped to the main drawing. I dont like to cut up my plans, so I traced it onto drawing paper and taped that into position. Even though there is no dihedral in the finished wing, the panels are built separately and then joined. This very thick wing has a flat section on the bottom of the airfoil so the wing can be build right on the flat board. It would be impossible to accidentally install a rib upside-down.
Wing construction starts with the lower 1/4" sq. basswood spar and TE sheet pinned down over the plan. The ribs are glued into position, followed by the 1/4"x3/8" balsa TE spar, 1/16x1" balsa sheet sub-LE, and top spar to lock things together. Then the large 5/16"x1-3/16" balsa LE piece is added, leaving a ledge for the top and bottom sheet to be added later. The second panel is then built to the same level of completion. The panels are joined with plywood braces at the LE, TE and main spars, and with a die-cut light plywood servo tray in place. At this time I left out the servo tray, since their final position was undetermined.
In the next step, four sheets of 1/16"x3" balsa are to be trimmed to 2-3/8" wide for the leading edge top and bottom sheeting, leaving the remaining 5/8" pieces for rib capstrips. I measured against the wing itself, and noticed that this only provided for a 1/16" overlap at the spar, about 1/16" short of the middle of the spar which is shown on the plan. So, I trimmed my sheeting to 2-7/16" wide, and later cut the capstrips from my own spare sheet. Note that you cant tell this by measuring on the plan, because the plan does not take the curvature of the airfoil into account. The top sheeting and capstrips are glued on, then the wing is flipped over to do the bottom. Finally the thick rectangular leading edge stock is planed and sanded to the proper contour. A template is provided.
The fuselage is started by applying some shallow balsa doublers to the side pieces. These doublers start at the nose and continue a little past the wing opening. Then the sides are joined together with the four formers. I deviated from the construction sequence a bit here, by fitting the wing before installing any of the fuselage sheeting or hatch framing. It was now that I removed the bottom leading edge sheeting and a portion of the LE within the equipment compartment, and then glued the wing to the fuselage sides. Next, I continued on with the firewall and hatch installation, but still left the aft bottom sheeting off until last.
The stabilizer and fin are installed next. Then it is time to fit the aft top deck sheeting. After a couple of failed attempts to mark the sheet in place, as shown, I resorted to making a paper template, which works best for me. Due to the slight compound curve, it was a struggle to get the 1/16" sheeting to lay down evenly over the formers, and to meet the fuselage sides. Mine ended up a little wavy, and I think that soft 3/32" would be a better choice here. With the bottom sheeting still off, I was able to apply glue fillets on the interior of the top sheeting for extra security. I used Model Magic filler to blend the sheet fillets to the tail surfaces.
I now needed to determine the location of the two servos in the fuselage. I temporarily assembled all the control surfaces to the model and loaded up all the gear where it fit best. Then I put the Dazzler on a Great Planes CG Machine, and was relieved to find that the servos could stay right in the equipment compartment. After this I glued on that bottom sheeting. I trimmed the light plywood servo tray for just two servos, then relieved the trailing edge sheeting for clearance, and installed the tray as far aft as possible.
Covering and Finishing
I really liked the color scheme on the box, but did not have the patience to duplicate it. I stayed with a pattern of lines and angles, and chose bright colors of Top Flite Monokote, pearl white, teal, and blue. Before covering I cut all the hinge slots with the new Great Planes Slot Machine. Wow, this was pure magic. You can believe all the rave reviews. Final sanding of the model was rather easy because of all the large flat surfaces. Covering was a bit tedious in the area of the wing to fuselage joint, but otherwise simple enough. What took extra time was splicing the colors together before applying the covering. I followed the Monokote instructions, and was very successful.
I am using a Futaba 6XA radio system, with programmable functions such as flaperons. The two aileron servos each plug into a separate receiver channel and are coupled as ailerons and can also be coupled to act as stunt flaps. I plan to try the flaps later, when I am more used to the already responsive nature of the airplane. All four servos are the regular size S-3003 model. With such large control surfaces, I dont think that mini servos would be sufficient. All control throws were set according to the manual.
The forward 7 cell 1700 Mah battery pack is held to the nose floor with a couple of double sided Velcro straps. The aft pack is held to the cockpit floor with the same arrangement. I have an AI Robotics FX-35D speed control above the battery in the nose. In the equipment compartment, the 500 Mah flat radio battery is positioned vertically along side the 7 cell battery. The receiver is placed flat along the power battery and just in front of the servos. There is some room to shift components to alter the center of gravity point. A final check on the Great Planes CG Machine indicated that the Dazzler was balanced right in the center of the range shown on the plan. The final weight was a fraction of an ounce over 5 pounds.
Main equipment belly compartment - servos at the rear just ahead of the training edge; receiver is shielded in aluminum foil; aft 7 cell battery is underneath the receiver; radio battery is along side of the power battery.
My AST-15G turns a Rev Up 11x8 prop at 7,300 RPM and draws about 24 amps. This is a little below the computer prediction, which is fairly common. Initial testing of the power system showed some interference getting into the receiver. Ive seen this before when a receiver is laying up against the motor battery. I wrapped the receiver in household aluminum foil, and the problem totally cleared up. This may vary from radio to radio.
With my chosen power system producing about 67 watts per pound, I was starting to get quite optimistic about this model's aerobatic capabilities. During takeoff, the Dazzler accelerates quickly and tracks well, although a little right rudder is needed. The tail comes up early, and the plane lifts off in about 30 feet with just a touch of up elevator. Top speed was predicted at 55 MPH, and that feels about right. This is all roughly equivalent to a glow .32, which is one of Great Planes' recommended sizes. All flights so far have been from a hard dirt field with scattered clumps of grass.
The Dazzler has a wide speed range too. I was pleasantly surprised at how slow it would fly, at a high angle of attack with the motor just above idle. I was even amazed at how far it will glide with the motor off, if the nose is just lowered a bit. All the while, those big control surfaces provide excellent authority. This makes it easy to drag it in on the final landing approach and set it down on the spot.
I feel that the higher of the recommended control throws are still on the conservative side for this style airplane. The Dazzler will roll quite rapidly, do fairly tight loops, and good stall turns. It will do continuous rolls or loops until the pilot neutralizes the controls. All maneuvers are initiated and completed crisply. This requires good pilot concentration, yet is satisfying because the plane does exactly what it is told. Any maneuver that can be flown upright can also be flown inverted, with confidence. Now that I am getting used to the Dazzler, I plan to set the higher of the recommended control throws on my transmitter low rate and dial in greater throws on high rate.
I am also impressed with the AST 15G motor. It is a good match for this airplane and on 14 cells delivers power in excess of what I would have imagined. The Dazzler's vertical performance is more than acceptable. I can pull up from fast level flight, and get about four rolls before leveling off again. And, it doesn't just fall out of this maneuver, it flys off in the chosen direction.
This has been a very rewarding electric power conversion. It's a quality kit that I would rate as a good value. The required structural modifications were minimal and the Dazzler's sport fun-fly design objectives have been preserved. It is a step up in aerobatic performance from the average electric powered subject. However, it is not too advanced for an average pilot with sufficient aileron experience. For those of us who also fly with wet power clubs, the Dazzler should fit right in.
|Feb 19, 2007, 09:09 PM|
Ottawa, Ontario, Canada
Joined Jan 2002
Stitzer motor mounts come in two sizes MM1 Astro 05, 15 cobalt; and MM2 Astro 25 cobalt. New Creations RC. Great place to deal with.
|Feb 12, 2010, 08:31 PM|
Joined Feb 2010
I got a friend a dazzler 40 equal to the model that you are teaching motar, except that my plan did not come to build step by step. You would send me?
I will be very grateful.
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