Hangar 9 T-34 Mentor
|Wing Area:||555 sq. in.|
|Weight:||6 lbs 2 oz.|
|Wing Loading:||25.42 oz/sq. ft.|
|Servos:||5 DS-821 control servos, 2 NS-791 retract servos|
|Available From:||Horizon Hobby|
In 1948 Walter Beech of the Beech Aircraft Company decided that his new Bonanza would make a perfect platform for a new military trainer, easier to fly and cheaper to produce than the trainer of the day, the North American AT-6/SNJ Texan. Out went the Bonanza's V-tail and 4-place cabin; in went a standard tail and greenhouse canopy. In 1953 the Air Force agreed with Mr. Beech and bought 450 of them, and the T-34 Mentor was born. Beech soon sold Mentors to the Navy, Marines, and Coast Guard as well. The Air Force moved to the jet-powered Cessna T-37 as a primary trainer in the late 50's. The other branches stuck with the Mentor, eventually moving to the much-improved T-34C, which are used to this day. Pretty much every Navy, Marine, and Coast Guard pilot you'll ever meet trained in a Mentor.
Hangar 9 came out with a yellow Navy version of the Mentor in 2003, then discontinued it; they have now re-released it with the striking white, red, and black color scheme. It is a fantastic-looking aircraft, particularly with the optional retracts installed. Throw in the 4-stroke Saito .82 and it sounds as good as it looks! If you're looking for a warbird-type airplane but don't want to be the 18th P-51 or 12th P-40 at your field, the T-34 might be the bird for you.
It doesn't matter how old you are, there's just something about opening up a new plane, especially a colorful ARF, that makes you feel like a 10-year-old on his birthday. The Hangar 9 Mentor is certainly no exception. Individually wrapped parts, several full bags of hardware, cowl, canopy - everything arrived in perfect condition.
This isn't an RTF or PNP model; rather it is a complex ARF. Even as an ARF, there is quite a bit to do - you build this kit, not just assemble it. That's great for those who miss the days of hands-on kit building but don't have quite that much time; but if you go into it thinking you'll throw it together in a few evenings and go fly on Saturday, you'll get frustrated. Figure on about 30 hours build time.
The only mild surprise was that the ailerons were not pre-hinged; but the slots are cut and hinging ailerons is not a big deal.
The Mentor uses internal tail linkages - which is a very nice look but kind of a pain to get right. We test-fit everything and thought it looked fine, but in fact the rudder control linkage stuck out of the slot in the fuselage quite a bit too high to successfully hook up a clevis without it binding badly against the slot. Unfortunately, once the control rod is glued into the rudder, there's no adjusting it. Faced with drastically widening the already too-wide slot, we chose instead to use a z-bend instead of the clevis, although bending it in place was tricky. It worked out fine.
The instructions advise to clamp the engine before drilling. We have probably 50 clamps of various sizes but none so small that they will fit between the mounting holes of a Saito .82. We had to hold it carefully with our fingers, measure 4 5/8" from the workbench to the thrust washer, square it, mark it, drill it, and hold our breath that we got it right. You only get one shot at mounting an engine right!
Another tip: if you are using a 4-stroke, which typically has the needle-valve on the right, reverse the carb if possible so the needle valve points UP rather than DOWN when the engine is installed. This will make it a lot easier and safer to tune your engine. Do this now before installing the throttle pushrod or you'll have to install the pushrod twice.
The instruction manual says to mix epoxy and alcohol to make a brushable fuel-proof concoction to paint onto the firewall. This is a holdover from the earlier version of the plane; this incarnation has a pre-fuelproofed firewall. However the inside of the plane, where the fuel tank goes, is open - to collect exhaust, oil, dirt, leaves, sticks, small woodland animals, and all the rest of the debris one picks up upon missing the runway. It's a very good idea to fuelproof this area, and it certainly isn't overkill to throw some balsa or light ply in there to seal it from the radio compartment.
And finally the fuel tank goes in sideways, at least sideways to our perception. The tank is rectangular. We figured it would go in vertically, i.e. tall and narrow; it actually goes in horizontally - wide and flat. This is critical because if you put it in tall and narrow, the fuel vent will point to the side of the tank rather than the top. This means you won't be able to fill the tank past half-way and you'll spend your first "flying" day messing with the tank (while your son stands around muttering disparaging comments about glow-addicted oldtimers, the pointlessness of internal combustion engines in general, and the lost art of reading instruction manuals, before going skipping off to fly his electrics.)
The instructions don't mention the orientation of the tank specifically, nor how to disinherit ungrateful smart-mouth children, but the pictures do show the tank in its correct orientation. Of course, also make sure that the vent is on the top, not the bottom, when you install (or re-install or re-re-install) it.
Note: Be sure to install the tank with the proper orientation, with the vent on top...
We used a new technique to mark the cowl to cut it for the engine. The time-tested technique of taping a piece of stiff paper to the side of the plane has the limitation that it can't follow the contours of the cowl as it gets near the front. In a slight modification, we created a masking-tape mold of the cowl, cut that to fit, then used it in the same way. It was pretty simple and produced a good result...
Retracts, particularly mechanical retracts, are the tinkerer's best friend. But keeping that in mind, and in your first-gear, patient, Zen mentality, the Mentor installation isn't bad at all. The nose gear mounts to twin rails that stick through the firewall and into the second fuselage former. They seem plenty sturdy and haven't broken yet. The manual states to mount the gear with four 3mm x 12mm screws, the same screws supposedly provided for the fixed gear, but which weren't in our kit. We had 12 2mm x 8mm screws, which just didn't seem beefy enough for the job. We purchased the correct-sized screws rather than take an unnecessary chance. Also, don't take a shortcut and try to drive these screws without pre-drilling the holes for them. You'll split or at least weaken the rails for sure.
The wing retracts didn't quite fit the space made for them, so out comes the Dremel and after a bit of fussing, they fit fine. The same thing was true of the space for the wing retract servo - more Dremelling was necessary.
Is all this fitting and re-fitting and Dremelling a huge deal to us? No - we were in that go easy frame of mind, and welcomed the chance to really build a kit. After all, one of the last ARFs we built (the E-flite Mini-Pulse) had the dang wheels pre-installed on the axles. That's a nice touch but it ain't model-building. That's model-assembling.
The only other thing to watch for is the throw of the retract servos. It is important to remember that you can't adjust the throws of a retract servo with your fancy-schmancy computerized radio. They're binary: UP or DOWN. That's all you get. You have to limit your throw the old-fashioned way, with linkages.
Here's the trick:
Not that hard!
And whether you use retracts or the supplied fixed gear, be sure to file or Dremel a flat spot on the strut for the axle screw. Failure to do this will - not may, WILL - lead to one or both of the wheels rotating 90° upon landing.
The throws are pretty small, but Hangar 9 knows what they're doing here so trust them. We decided we knew better and increased the elevator throw by about half - and introduced a dangerous high-speed stall tendency -- just until we decreased it again. At the stock throws, the model performs exceptionally well, and does NOT have this stall tendency.
We all know that a stall occurs when there isn't enough lift to hold the airplane in the sky. Lift is a function of speed and angle of attack - increase the angle of attack at a constant speed and you increase lift - up to a point. That point is when the air can no longer follow the top curve of the wing; it separates, and suddenly you have no lift at all. Normally we witness this at low speeds, particularly landing, as we feed in elevator to slow the plane down. But it can happen at high speeds too, if you have a lot of elevator authority and use it improperly. When you put too much elevator in, or put it in too quickly, you'll witness the following: the plane pitches up, of course, but its forward momentum is too great to allow it to go up and it will drag its increasingly pitched wing horizontally through the air. This dramatically increased angle of attack will cause the airflow to separate from the wing, resulting in a stall and (usually) a snap roll.
All that remains to do is glue the canopy on (you can't screw it on, as the top of the plane is made of styrofoam), check the CG (which we achieved spot-on with no modifications -- YES!), set the control throws, and install the receiver.
There is a self-stick decal sheet to dress up your plane, but the sheet includes two intrument panel decals that we don't recommend using - at least not as supplied. They look great until the plane sits in the sun for half an hour, at which time (on our plane at least) the rear decal left its designated spot and went on a tour of the cockpit, where it eventually came to rest glued to the inside of the windshield. It took quite a bit of coaxing with a variety of increasingly serious tools to get it out from under the canopy. Unfortunately this left the canopy partially unglued at the front, which led to air getting under it during flight, which led to the canopy going its own way in the middle of our second flight. Our bad, that - we should have taken the time to re-glue it. Epoxying the decals in place might work better, or installing a balsa instrument panel on which to glue them, or leaving them off altogether (which is what we chose before re-gluing the canopy). Down the road sometime we might trick out the cockpit, but for now this airplane is all about flying.
Our maiden flight day dawned clear and sunny and cold, at least by Southern California standards - 37°! But we RCGroups reviewers are an intrepid lot, so with nothing more than a couple of double lowfat Toffee Nut lattes for warmth we braved the elements for our maiden. The reliable Saito .82 fired up on the second flip (we LOVE this engine), and after tweaking the engine a touch we took off.
With the engine well broken in and tuned properly, Quinn put it through its paces. This is a scale plane so we didn't try anything really dramatic, but it rolls very cleanly with minimal drop, and with the Saito .82 it plain scoots. The most fun we had with it was full-throttle low passes pulling up into a stall turn and back for another pass.
We thought visibility might be difficult, with not much to distinguish the upside from the downside of this plane, particularly with the gear up. But that big ol' greenhouse canopy and the red rudder are hard to miss, so we had no problem.
Takeoffs are very straightforward. Roll the throttle on gently, hold a bit of right rudder, and coax it off the ground with some elevator. She wants to fly, and fly she will! For those who opt to install retracts, there's a thrill to hitting the switch and feeling the plane speed up as the drag decreases.
The forum talk is that this plane doesn't like to land slow, and the forum talk is right. This plane needs to carry airspeed all the way to wheels-on-the-ground. Don't float this plane in; it isn't a trainer. But landing "fast" is no big thing. Hold a bit of throttle on final, keep a slightly nose-down attitude, and cut the throttle as you flare it into the ground at the last moment. Don't start your flare waist-high, nor wait for it to stall.
We didn't feel that the plane stalled prematurely or was particularly difficult to land - nothing for a reasonably experienced flyer to be afraid of, but keep your wits about you. Also, with the 13x8 prop recommended by Saito, this plane has very little ground clearance, so I see the occasional broken prop in our future. A 12x8 3-bladed prop might be a better choice.
This is a scale plane and it's good for scale aerobatics. Rolls are fantastic and straight. With all that power, loops can be as big as you want, but as mentioned we had a high-speed stall at the bottom of one loop from giving it too much elevator input too suddenly. (See the sidebar on trusting the manufacturer's throws!) It has plenty of rudder authority, so stall turns are crisp. Cuban-8s, Immelmans, spins - this plane will do whatever you want it to do, and look good doing it.
With the proper help and enough time on a simulator, a properly motivated beginner could learn to fly a garbage can lid. But that doesn't make it a good idea. Ironically, while the full-sized T-34 is a trainer, this model is not. Although it is quite stable in flight, its landing speed, low ground clearance, and (with the Saito .82 at least) relatively high speed would make it challenging. We don't recommend it at all as a trainer.
The plane was more work to build than most ARFs, but it was rewarding! Ultimately it resulted in a very nice-looking and great-flying plane. Mated with the awesome Saito .82 the plane is surprisingly fast and a great step up for someone who has mastered a trainer and a sport flyer. For a seasoned electric flyer this combination, with its ease of operation and throaty 4-stroke sound, could make a great introduction to glow flying. And if you're concerned that adding retracts will make it more difficult to build or maintain, rest assured: it will. But it is well worth the effort.
Hey Jon. That was Quinn landing. You can tell 'cause the gear is still on at the end. You can see my landings on our upcoming outtakes reel.
St. Anthony's field might be a TAD small for this bird. You ought to come up to Santa Ynez with us sometime soon. We'll hopefully be flying our .60-size Extra 300 e-conversion this weekend (shameless plug for our next article)...
Currently I am putting this kit together - modified for electric. In regards to the rudder linkage not being 100% correct to align with the fuse and the rudder push rod, probably the better solution (which is what I did) than to expand the openning in the fuse or z bending the push rod - was to cut the internal metal rudder linkage in half and sleave with an appropriate segment of brass tubing. If I remeber correctly the internal distance between each end of the arms is 52 and really needs to be 57mm - in other words 5mm longer.
In doing so - I found that the metal clevis would rub on the side of the fuse and the wooden push rod need to be orientated os the dowel did not snag on the internal formers. With the clevis - I used a dremel and removed from one side, some the clevis and also smoothed the threaded portion to reduce any tendency to bind or snag.
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