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Jan 17, 2013, 09:58 AM
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Build Log

Art Tech T6 Harvard

Imported from the USA because unavailable in Europe, I was able to free it from customs after paying a substantial sum for import duties and taxes, and opening the box showing them there was no radio equipment (requiring Belgian radiowave testing) in this PNP version (on the box you saw only pictures and info about the Ready To Fly aircraft with a Tx pictured next to it). After getting home I quickly dry assembled this model and found it very attractive and much more scale than expected.

I had ordered the silver version because the base colour seemed closer to the version I wanted to make, the Belgian registered OO-DAF owned and operated by Eric Vormezele from EBBT since a few decades (and I got a ride in it).

Stripping the decals took away a lot of the paint so I had no choice than to remove it all. The silver was extremely brittle and even working outside, I looked more like a Folies Bergères artist glittering on stage, than a model builder. The red paint on the vertical tail was very difficult to remove because of the fabric compound curves in the foam. The red wingtips were brittle and navigation lights just lose without glue. With the knowledge of today I think if you want to make any particular T6, it is better to order the gray version, remove the decals and apply a gray primer over the whole airplane, but you’ll need some patience to paint the frames of the greenhouse. Further dismantling the model I discovered it had a complete sound system just thrown loose in the fuselage without fitting instructions.

After reading the 300+ pages about this aircraft on R/C groups I knew this was no ARF model, but that it needed detailed attention to change into a reliable flying platform with more attractive sound than just the electro engine. I first straightened out the landing gear problem, then connected the three flaps the way I had done on my DC3 (because of the wing dihedral angle). Next I structurally connected both wooden wing spars to eachother and to an adjacent torque tube. I replaced a failed aileron servo and tightened up everything that was loose (and that was a lot!).

Having read the mishaps of other pilots (including inflight folding wings and catching fire due to the sound amplifier heat dissipation sink reaching over 100°C), I analyzed the possibilities to mount the sound system. Testing the sound proved the system acceptable with a nice startup sequence and idle RPM. I was convinced it would attract much attention on the ground and I like to taxi from the pilot area and back so I figured having the heat sink under the wing might be ideal in flight, but risked melting the foam around and above during the long ground operations (we have a 270x60ft asphalt runway 100 ft behind the safety fence). The length of the provided electric wires and eventual connection problems between the wing and fuselage led me to opt for mounting everything in the cockpit. I therefore opened up completely the space between the dummy engine cylinders (also molded in foam), made the port air scoop fully functional and cut out the lower portion of the pilot dashboard to allow adequate cooling air for the battery, esc and sound amplifier.

I made carbon pieces to install the speaker firmly below the cockpit (using copious amounts of permanent thread locker and strong nuts and bolts because you can imagine it produces serious vibrations. The complete assembly then became sandwiched by the wing being bolted below, with a hole to allow the sound to pass through the wing, and the narrow slits on the cover panel were cut out and replaced by a larger circular hole with a mesh wire glued flush. It had been very difficult to remove that panel because the Chinese had applied liberal amounts of glue on the flat part and it was almost impossible (but doable) to pry it loose without damaging the thin panel.

After completing the changes I dry assembled the 3 large wing panels and checked the many electrical connections between them. Navigation lights and landing lights drew their power from the aileron cables in a kind of printed circuit mounted between the center flat wing section and the cranked outer section. Flaps only have 2 servo’s on the outer portion, the center split flap originally being driven only by non-notched pins close to their pivot points. I modified that by gluing a short lenght of carbon hollow tube on the trailing edge of the center flaps, and piano wire to the outboard flaps. These slide into each other after assembly, allowing synchron movements during flap operations despite the dihedral (similar to what I had designed for my Dynham DC3).

The only practical place in the cockpit to mount the soundcard and heat sink (factory mounted electrically and mechanically at a 90° angle) was on the left side of the pilot seat (just behind the cooling exhaust from the airscoop).
This necessitated the amputation of the pilots’ left leg and his reproduction organs. His left arm would have been too close as well so I cut it off and glued it back on in a position like he’s waving at the crowd.

I initially thought the back window I cut away from the canopy would have provided sufficient hot air exit, but I later decided on an even better cooling on the ground by cutting out the sliding pilot canopy and gluing it back on in an almost open position. This reduced the strength of the removable top so I had to reinforce the bottom part with some carbon strips on the sides. The spectrum AR600 receiver found a place on the right side of the back cockpit seat so all cables are accessible without ever having to remove the 130mm span wing. I put a black paper on top of it (below the lower instrument panel and the back seat floor pan) and except for the receiver light in my AR600 everything is invisible.

Having made the necessary incisions in the foam I then pulled the cables around to keep them away from the amplifier and heat sink, made the connections and performed a last audio test before gluing the sound card to the seat with non-conductive (electro or heat) epoxy. Next came the pilot and stick against his right thigh, his right hand was later bent for a realistic grip on his stick.

Because the airplane I choose to reproduce (I had a flight in it around the turn of the century) is equipped with a long exhaust with combined cabin heater I had to dremel out a portion of the fuselage and custom-build this very visible system.

Thanks to a number of pictures of the original, the painting ended up ok, spraying the silver and yellow, brushing the orange, self-made Belgian roundels on Testor white decal paper, hand painted nose art pinup, letters cut from self-adhesive black paper, hand painted wheel cover disks.

My model needs a bit of weight in the nose but I maidened it with one of my heavier (3S2200 batteries) at the aft recommended cg with a 1580gr takeoff weight. I’ll try a 3S3000 soon. I’m against adding useless lead, this heat producing sound system uses considerably more power than the system of, and my stock engine needs about ¾ throttle or it stalls with a hefty wing drop, so I can use some extra battery capacity. The model is prone to tip stall so I brought it in for a 2-point landing with half flaps, but it still dropped a wing on me without causing damage (when I attempted to cut the glide-angle in half about a foot over the runway).

It showed no other bad vices and needed almost no trim changes, even extending the 3 position flaps required only minimal elevator movement (that’s the advantage of split flaps). After this maiden I will now further refine the handling and balance it out, and finish the details of this attractive model. The Chinese sound system works very well and together with very strong (landing) lights make this model a head turner well worth its money. I threw-in various pictures of the assembly progress and and it resembles the original airplane well.
Last edited by BAF23; Sep 17, 2015 at 06:25 PM.
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May 12, 2013, 05:25 PM
The sky is the limit
BAF23's Avatar
Thread OP
Spring 2013 I added a Hobby King Orange RX3 Version1 stabilizer to facilitate takeoffs and landings. More details about that and its installation can be found on the dedicated page of my blog.
Stay tuned for some recent flight videos and in the meantime have a look at my model compared to the real airplane

I finally got some video shots from my Harvard from two people with cameras. One has a nice HD camera but without a viewer so I only got some ground shots with the noise of the original sound system
Harvard groundops (0 min 52 sec)

The other guy has a viewer but a lesser quality camera, but at least I can show you some airborne shots. Hopefully I will be able to replace all those videos with a single good quality edited version of the highlights of a flight soon. In the meantime bare with me with the following taken on a windy day.

When I first installed the Orange V1 flight stabilizer I had the pitch-gain a tad too high which resulted in occasional dolphin movements, the worst happening just at liftoff and immediately after gear retraction. I immediately reduced speed and setup a landing pattern, not daring to even extend the flaps. Needless to say, I was apprehensive landing it but I managed.
Harvard gyro probrem ok (1 min 49 sec)

After making minimal adjustments to the throttle and gyro settings I started-up and taxied-out again for another check flight
Harvard startup and taxi (0 min 49 sec)

This time the stability problems had been eliminated and the takeoff was uneventful except for some yawing movements due to the crosswind, which I was able to correct in time to maintain the runway heading. After trimming the plane I first made some photo passes, trying to fly the Harvard as realistic as possible, but when I started a looping the cameraman lost the plane in his viewer.
Harvard to gyro ok (2 min 46 sec)

He finally picked me up again in the bright sky and continued filming some maneuvers. Note the realistic roll rate for a T6
Harvard flybys ok (1 min 0 sec)

Before coming in for landing I always perform a visual check on the gear and flap extension. That landing certainly wasn't my best one but hadn't a cameraman been available that day, I even wouldn't have flown my T6 due to the wind.
Harvard landing ok (1 min 17 sec)
Last edited by BAF23; Sep 17, 2015 at 06:33 PM.
Jul 22, 2015, 11:01 AM
The sky is the limit
BAF23's Avatar
Thread OP

Video compilation

Summer 2015, the model is still going strong and has been reprogrammed on my Taranis FrSky equipment. I also made a compilation of various shots of this charismatic model.

harvard model compilation (9 min 9 sec)

By the end of 2015 I noticed during a gyro-off CG dive check that the model just continued straight down which indicated the CG being at the aft limit. This was probably caused by multiple small changes and repairs (all aft of the CG), plus one impact on the nose that pushed the engine so far back that the prop touched the cowling. High time for some maintenance but before that I first took note of the balance and was chocked to see it aft of the most aft recommended 75-85mm range. No wonder I had so many problems landing the model lately, even with the gyro stabilization active. About 50gr on the nose restored the balance.

After removing the prop and the cowling, I pried off the fake engine to obtain access to the engine. This was bolted to a nylon cross that was uneven in thickness to create the required side-thrust. After adding a few metal rings between the wooden firewall and the nylon cross the engine was mounted again and the drive-shaft protruded out at its original distance again. Foam was then carved out from the lower fuselage front and the back of the fake cylinders in the lower quadrant. This allowed me to insert a curved piece of flattened lead weighing 51gr. It is totally invisible and well situated at the extreme front lower side of the model, unable to get loose during wild maneuvers or hard landings. After the cowling and prop were bolted on again, the CG was exactly in the middle range at 80mm from the leading edge and the model with battery weighs 1660gr, resulting in a 76gr/dm² wing load.

Spring 2016 will require complete trim flights with the gyro switched off to get all the controls neutral again with zero trims. I also mechanically adjusted both ailerons to a little up neutral position (2°reflex) hoping this will help reducing the tip-stall tendency.
Last edited by BAF23; Jan 10, 2016 at 04:26 PM.

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