Saturday, April 11, 2009

Mugi Tea Racer: Another Hit From Across The Pond!

The Tea Racer has flown! Numerous flight tests this morning concluded however that I have too much positive incidence in the wing. Apparently I didn't cut the wing saddle out deep enough, however this is easily remedied by simply cutting it deeper. Now I just hope I can find the template that I made so I can keep the shape right.

On the first takeoff it appeared that the plane was tail heavy, even though I had purposely balanced it a bit nose heavy for the initial flight. It lifted off the ground by itself long before I was ready, then porpoised badly all the way back around to a rather disgusting but thankfully damage free landing. I moved the battery farther and farther forward on subsequent flights until the thing was so nose heavy that it would barely set on the landing gear without nosing over, still no joy.

I then greatly reduced the elevator throw and programmed in a ton of exponential, still it was extremely sensitive on the pitch axis. A closer look revealed that I had a ton of down trim in an attempt to attain level flight, even though the plane was now obviously nose heavy. This is a dead giveaway for excessive wing incidence. Also the plane would tend to want to climb more and more as speed was increased, which is another dead giveaway.

It did however, accelerate dead straight with no pitching tendencies on throttle application, so the thrust angle must be in pretty good shape. Also, even though the wing was running far too high of an angle of attack, the venerable Tea Racer showed absolutely NO tip stalling tendencies at low speed, which is truly amazing for a plane this small. This, coupled with the fact that even though this plane feels a bit heavy for its size it glides FOREVER, is a testament to Morgan's design ability.

When I get the wing incidence right, this thing is going to be an absolute JOY to fly. It already shows potential far beyond several factory made planes that I own with no doubt MUCH more money poured into their R and D. The takeoff run was basically uneventful, with only a tiny application of right rudder necessary to maintain a straight track, and once again, even with the incidence issues I can tell that this plane will practically land itself once it's flying the way it's supposed to. So far I'm impressed, and I can't wait to fly it once the wing is pointing where it's supposed to be.

Oh yeah, did I mention that it's FAST! I couldn't really open it up for obvious reasons, but I did manage one or two high speed passes with a victory roll or two thrown in for good measure. It's not called a Tea RACER for nothing! This thing is going to be a blast, and judging by the interest it generated at the field, I won't be the only person around here flying one for long.

So overall, my opinion of the Tea Racer at this point is pretty high. The incidence issue is my mistake, not a flaw in the design, and hopefully I'll be able to measure the actual incidence when I get it figured out so I can post it here as well as on the Mugi Forum. Even so, there are many variables when folding a Coroplast wing, so your mileage may vary.

The tailwheel? It performed flawlessly, no ground handling issues whatsoever unless you count the nose over tendency the plane had with the battery crammed too far forward. My main gear mounting methods are subject to review however. It seems that the hardwood blocks I used to secure the gear should've been anchored somehow to the wing spar for added stiffness. I'll revise that on version 2.0 and see if I can't come up with something better. For now they're getting some glue shot under them so the testing can resume.

What are you doing reading this? Get your butt busy and build a Tea Racer, you'll be glad you did!

Friday, April 10, 2009

Tea Racer Tailwheels and Monkeys From Wyoming

I mentioned in my last post that my current project is the Slope Monkey from Wyoming Wind Works. Thanks to my friend Mark for turning me on to this little gem. Considering he's the same guy that turned me on to the Mugi, I really should start listening to this guy a little more methinks. Basically, it's a non powered slope glider made of hot wire cut EPP foam with a balsa tail assembly and ailerons. As a testament to Adam and the gang at Wyoming Wind Works however, I won't be doing a build thread on this bird at all. The reason being that the included instruction manual is THAT GOOD! It truly leaves nothing to be desired. Follow Adam's instructions and this plane will virtually fly off of your build table. This is coming from someone who has never worked with EPP before. If you have some EPP experience, you could practically build it without the manual. This thing is truly a piece of cake, and should make a great sloper when it's done. Slope flying sites around here tend to be a bit rocky and treacherous, so a durable plane made of either EPP or Coroplast is basically a necessity if you don't like packing home chunks of busted equipment every time you fly. I think my little 'Monkey will fit the bill nicely when it's finished. All that's left is to cover it, and of course I'll post pics when it's done. Wyoming Wind Works has some other interesting projects in the works as well, so go check them out. Personally, I'm a bit stoked about the Orangutan, (larger version of the Slope Monkey), however Mark and I have decided it should be called the "Grade Ape". I'll be watching for a special on a roll or two of purple Ultracote just in case.

I decided to go ahead and add a tailwheel to my Tea Racer. Why? Cuz it looks cool that's why, and because I get annoyed by planes with crappy ground handling. Tailwheels don't add much weight, and they definitely improve ground handling, so why not? Here's how it's done.

First of all, there's an easy way, and there's a hard way. I did it the hard way, simply because I couldn't find one damn elusive wheel collar in one of my many small parts boxes. Of course I found said wheel collar the next day after the deed was already done, but that's the story of my life so we won't go into that.

The first step, is to locate a length of music wire, doesn't really matter what size as long as it's capable of supporting the weight of the tail of the aircraft and is large enough to fit at least somewhat snugly into one of the flutes of a piece of 2mm Coroplast. It also helps if you happen to have a small wheel, and a wheel collar or two that isn't buried in the bottom of a box of little parts that will fit on said piece of music wire as well. The wire needs to be long enough to reach through the rudder fin and protrude out the bottom of the aircraft far enough to bend it, and attach the wheel. If it's a little short, no big deal, it only needs to be about halfway inside of the fin when you're done but if it's longer it'll be a lot easier to work with.

From the top of the aircraft, insert the wire into the frontmost flute of the rudder. You want it going through the part that moves, right behind the hinge. When you have it inserted, double check that the rudder is straight, then press it through the coroplast until it protrudes inside of the fuselage. DON'T press it all the way out the bottom at this time! Remove the wire, disconnect the rudder linkage if it's connected, and swing the rudder off to one side. When it's out of the way, enlarge the hole that you just made in the horizontal stabilizer enough so that the wire can swing with the arc of the rudder. I used a small phillips screwdriver and just pressed it through. Try not to get the hole too large or it'll look like crap.

After the hole is enlarged, reconnect the linkage and recenter the rudder. Place the wire back in the foremost flute of the rudder and press it down through the hole you just enlarged. Now look in through the hole in the back of the fuselage and see if the wire is pointing toward the center of the bottom of the fuselage. If it is, it will be aligned with the carbon rods you used to secure the fin. Also check that it's not colliding with your elevator linkage. When all is well, and you're sure it's straight, go ahead and press it on through the bottom of the fuse. DON'T enlarge the hole in the bottom of the fuselage.

Now, if you have an appropriately sized wheel collar, and you haven't lost it yet, place it on the wire that is protruding from the bottom of the aircraft. Slide it up to the bottom of the fuselage, and gently pull the wire downward until the upper end is about halfway through the rudder fin. Leave a little more if you want more strength or happen to need tail weight, just make sure the wire is inside the leading edge flute of the rudder where it can't be seen. The wheel collar will reside against the bottom of the fuselage acting as a thrust bearing so that the rudder fin itself is subjected to the shock exerted during rough landings. The collar will transfer said shock to the bottom of the fuselage instead.

When everything is situated, tighten the setscrew in the wheel collar, then bend the protruding wire into a typical tailwheel holder like shape, attach your wheel by whatever means you choose, and you're almost done. The only thing left is to attach the wire to the rudder so that your new tailwheel is steerable. Simply look at the plane from the rear and ensure that both the wheel and the rudder are straight, then drip a few drops of thin CA down the flute with the wire in it. I find that when securing things inside Coroplast in this matter it helps to gently squeeze the coroplast against the wire or carbon rod inside. It seems to set the glue faster and provides a stronger bond. Let the glue cure and voila, you have a tailwheel.

Or, you can do it the way I did. I couldn't find the right size wheel collar, but I did happen to have a Dubro Micro Tailwheel kit handy. Either way, you're Tea Racer is bound to taxi a lot better. With a little luck, I'll know tomorrow morning how it effects the takeoff run.

Also, Morgan has placed a discussion forum on the Mugi site. It's not going full steam just yet as it's rather new, but it will no doubt soon be filled with a wealth of information regarding Mugi aircraft. Go check it out and don't be afraid to contribute if you have something other Mugi flyers may find useful.

Until next time . . . . . .