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Old Aug 16, 2006, 09:55 AM
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Albuquerque NM
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Mini-Review
AT-602 Air Tractor from dV Flight Technologies

The oppertunity arose not long ago to review the dV Technologies AT-602 Air Tractor, so thought it would be worth a thread here too.

The kit is complete, less wheels, spinner, and the hardware required to connect the flaps and ailerons. However, a complete list of the additional parts needed is provided in the instructions.

The model spans 42" with a wing area of 205" with a recommended flying weight of 12 oz. Suggested power is a geared 350 or 2205BL. Control is 5 ch. (rud, elev, ail, flaps, throt.) Since I have one, I'll be using a Himax 2808-890 motor with a 9-4.7 prop, a Thunderbird 18 ESC (w/ 3 amp BEC) and a T-Power 1320 2 cell Lipo. The set-up is about the same weight as the geared 280, but will make a bit more power using 2 cells.

First impresions was that there's a TON of wood in the kit (17 sheets balsa, 2 ply), but after framing the fuselage and tail group, the weight of the finished parts truely defey the appearence. At this point, the design looks really good, and by using the "tab & slot" style of construction, makes for a light, strong, easy to build airframe.

Let's get started!
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Old Aug 16, 2006, 10:07 AM
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Framing the Fuselage

When building a new kit, I always follow the instructions to the letter to avoid trying to outsmart the designer and finding myself painted into a corner. And as with any kit, it's well worth the time to read and study the plans and instruction before construction begins.

Since a motor will be used that is not common to the provided mounting system, the changes were made to the effected formers before construction began.

The basic fuselage frame builds quickly and easily, and for the most part is self aligning. The aft section is built first, and is basically idiot-proof (I'm safe back there ). A drafting triangle was used to check the forward section was straight, and was also used to insure the center section was properly aligned as the forward section was glued in place.

Once the 3 sections were joined, the joints were filled with medium Cya and imediately sanded to fill the slight gaps. It doesn't get any stronger then that, and there's no additional weight involved.
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Old Aug 16, 2006, 10:22 AM
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Sheeting the Frame

Laser cut 1/32 balsa top and bottom sheeting was provided, and fit beautifully with very little trimming. The sheeting was spritzed with water to aid in bending around the formers and glued in place with Cya. Once done, balsa colored Micro Fill was used to clean up the small imperfections at the joints.

The landing gear assembly was bent, assembled and installed in the fuselage next. As it turns out, the provided 1/16 wire is exactly the right length to bend the gear as shown in the bending pattern, but using the DuBro 2" Ultra-lite wheels, the axle would be too short to secure the wheels, so I bent the axles 3/8" longer then shown, then split the difference at the middle bend. In the end, each side is 3/8" shorter then shown, but will still provide more then adequate prop clearance.
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Old Aug 16, 2006, 10:25 AM
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Framing the Tail Section

The tail section is made up of several laser cut parts. Once again, parts fit is great. When dry, the parts were sanded to shape. The elevator joiner was bent to shape and will be fitted into the elevators before covering begins.

Will begin framing the wings today, and will post up a table of finished weights when the major assemblies are finished.

PAT
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Old Aug 16, 2006, 11:00 AM
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Pat, glad to see you building this one! I've always been interested in crop dusters.

That looks like one stout, but light fuselage, although I can't tell how the motor stick mount is anchored.

Looks like one will need to handle the rear of the plane with care, with those skinny elevator balancers. Would be easy to crack one just by bumping something while handling.

Will be watching with interest.

AmpAce
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Old Aug 16, 2006, 07:29 PM
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Framing the Wing

The wings are framed around the upper and lower 1/16 sheet spars with a 1/8 sheer web in between. The ribs are supported by the leading edge and sub trailing edges with an additional hinge spar. The interesting thing is that both wings are identical, except that the end ribs are swapped to create the basic LH & RH frames.
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Old Aug 16, 2006, 07:34 PM
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Adding the Sheeting

With the basic frames together, the center sheeting and the turbulator spars are added. The panels are then joined using a 1/8 spacer rib sanded to a bevel to set the dihedral. The tip was blocked up 3 1/2" on one end while the glue dried. Then a 1" wide strip of .6 oz. fiberglass cloth was laid in with thin Cya, top and bottom, to secure the joint. The wing dowels were added just before the center section was joined.
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Old Aug 16, 2006, 07:37 PM
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Installing the Servos

The rudder and elevator servos were glued in place on the mounting former in the aft fuselage. The wing servos were cut into the center section and all were secured with silicone. Ther is mounting hardware for the wing servos, but I just couldn't bring myself to let the servos protrude out the bottom of the wing. Will deal with the push rod routing when the time comes.
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Old Aug 16, 2006, 07:47 PM
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The Last of the Details

The ailerons and flaps were built up, shaped and hinged into the wing next. Then the wing dowel holes had to be drilled into the LG mount former, which turned out to be far easier then I would have guessed. The hold down bolt plate was glued on place and the hole drilled and tapped for the 8-32 bolt.

With all that done, it's time for the first dry run. With all four servos in place, the motor mounted and the wheels, cowl and conopy in place, she's tipping the scales at 11.4 oz. With the addition of covering, Rx, ESC and all the pushrod hardware, there's no way we'll make the advertized weight of 12 oz. I'm guessing 14 - 15. Will see how it goes. But in spite of that, it looks like the model will be a good flyer -- it just has a friendly appeal about it!

Amp, the motor mount stick glues into holes in the first and second formers. The motort will be secured to the stick with a screw through the aluminum mount.

PAT
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Old Aug 16, 2006, 08:11 PM
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Sweet Build. I'm going to try and pick one up from Gary at Chilliwack in about 2 weeks. (Well he's going to Europe so he's going to leave it with someone that will be there)

--Paul
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Old Aug 23, 2006, 10:00 PM
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Getting the Flaps and Ailerons Hooked Up

The Flap and aileron servos are mounted in the wing Center section, and the controls hooked up using push rods and belcranks. So far, this was the trickiest operation of the build, mostly because I mounted the servos high so that they would not protrude out the bottom of the wing, but the system went in just fine, and works good. Both flaps actually dropped the same amount on the first try!

I did have a problem with push rod clearance around the servos, and rather then add any addition twists and turns into the push rods, I opted to reverse the effected bellcrank and relocate the control horn. Definitely the easiest way to solve the problem.
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Old Aug 23, 2006, 10:08 PM
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Fitting the Rudder and Elevator Push Rods

Nothing complicated here. The push rods are .032 wire connected to the servo at the front and the control horn at the back. By crossing the push rods, the rods run straight down the fuse with no interfearence. The exit points were marked on the plans so there will be no guess work once the cover goes on.

The kit instructions recommend using micro easy connectors for all the servo conections, but since the weight was coming up rather quickly, I opted for the "weightless" z-bends with a "V" bend for minor adjustments of the individual flaps and ailerons if needed. If there are minor adjustments needed for the rudder and elevator, the sub-trim in the radio should be sufficient to handle it.
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Old Aug 23, 2006, 10:12 PM
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Now, We're Ready to Cover

With all the systems in and working, the model was torn down and given a final sanding to prep for cover. Will be using Litefilm for the base colors, and will go see Callie for the graphics.

Stay tuned, it won't be long now! PAT
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Old Aug 24, 2006, 10:34 PM
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The Cover Is On

Went rooting through the Litefilm stash this morning and came up with enough red and yellow to get a good "Crop Duster" scheme laid out. The goal was high viz, and this one should work.

Then once the cover and most of the trim was on, went ahead and started the final assembly. Got the tail section glued on and the Rudder Elevator, Motor and flaps hooked up. Still need to paint the cowl and canopy, and get the ailerons hooked up. Other then that, she's pretty well done. Very nice kit so far, will detail the impressions when she's done and flown.

PAT
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Old Aug 25, 2006, 12:10 PM
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Looking good Pat! I think your "hi-vis" color scheme worked!

AmpAce
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