Sunday, March 29, 2009

Yet Another Project Finished

It's been long awaited, it's been anticipated, it's been languishing on my list of "to do" projects long enough, and it's finally ready for a test flight. That's right folks, the Tea Racer is finished! Here's a few pics of the last build steps outlining some of the deviations I made from the plans.

This pic shows the aileron servo installation. Getting the servo and the linkages to clear the battery, as well as the other servos and their respective linkages was a bit of a trick, but luckily it appears that all will be well. I can't say that I'd recommend going the torque tube linkage route on your Tea Racer, but if you want to this shows that it can indeed be done. About halfway through I was starting to wonder if the mod was worth the effort, but I do think it contributes a cleaner look, and probably shaved a tiny bit of weight by eliminating one servo.

Here's a pic of all of the gear, minus the battery, and how it's laid out in the fuselage and wing. The empty servo lead protruding from under the white velcro square is the extension into which the aileron servo connects. The receiver is attached to the bottom of the fuselage right behind the wing opening. You can see the bundle of wires leading back to it although the receiver itself is out of sight. The battery attaches to the velcro strip barely visible at the top of the pic. No additional straps should be necessary, as with the wing installed on the aircraft it's sandwiched pretty good between the wing and the inner fuselage plate. This should be sufficient to keep the battery from detaching from the velcro on the wing. I attached my battery to the wing attachment tongue according to the plans, and found that the CG is correct with the battery even with the front of the tongue. Your results may vary, but there's a fair bit of room to move the battery, as well as the ESC, around in order to get the balance where you need it.

My insistance on using a single aileron servo limited me somewhat in this respect, but a good CG was still easily attained although I was forced to install the ESC in a manner in which it will be in constant contact with the battery. I don't particularly like this for reasons of cooling, but there isn't really another option due to the fact that I can't move the battery back any farther without hitting the aileron servo, and moving the ESC forward is limited by not only the length of the wires, but also the fact that my CG would then come out nose heavy. We'll see how this works, hopefully it isn't a problem, but I already have an idea of how to correct it if it is.

Also, my original hunch involving keeping the aileron linkages close together at the center of the wing paid off. They JUST clear the linkages from the rudder and elevator servos, as well as everything else.

Here is the landing gear. I think I showed earlier in the build where I attached two hardwood blocks to the bottom surface of the wing with 30 minute epoxy, just in front of the wing spar. This what the landing gear attaches to, and between the two screws, and the fact that the wire sinks into the coroplast rather nicely, the gear seems quite secure. The wheels were just some that I had laying around, nothing special, and the landing gear itself was salvaged from the wreckage of my P38 Lightning and modified to fit this application. The largest prop this thing is likely to see is a 4.75X4.75, so it doesn't need very tall gear for ground clearance. I kept them as short as possible for weight/drag reduction purposes. I haven't decided if I'm going to add a tailwheel yet, but if I do, I already have the plan figured out. I might fly it first and see about the ground handling, then make up my mind from there.

Here's the method I used to attach my wing, it varies slightly from the plans. Two hardwood blocks sandwiched together, and attached with 30 minute epoxy. A hole was drilled into the center, and threads cut into the hardwood to accept the #10 nylon wing bolt. Be sure to harden the threads with thin CA to prevent them from stripping.

When you thread your wing attachment block, run the tap THROUGH the mounting hole in the wing. Not only will it cut a better thread because the tap isn't wobbling around, but it insures that your threads will be aligned with the hole in the wing. Will save you a lot of time fiddling around trying to line up your wing bolt. Mine practically falls right to where it needs to be.

This pic shows my simple motor installation method. The motor mounting system outlined in the plans works famously, however it's a bit of a bugger to get the motor inserted in the front of the aircraft with the velcro in place. I simply wrapped my motor in a bit of heavy, clear plastic, inserted it into the nose, then carefully slid the plastic out from around the motor allowing the velcro to take hold. I tried a few different materials, including heavy paper, as well as a hunk of "bleach bottle" plastic, but this method seemed to work the best.

Here's the finished motor installation. Be sure to attach the wires from the ESC before installing the motor, and check the direction of rotation unless your motor has a lot longer wires than mine. Connecting them, or reversing the direction, would be impossible with my motor without removing it from the airframe.

And here she is folks, the finished Tea Racer! As I mentioned, there's a few loose ends I still want to tie up, as well as perhaps adding a bit more to the color scheme in the form of perhaps some yellow stripes on the fuselage, and some more black on the tail, but if the weather cleared up right now I COULD fly it in its current form. It's been a long time coming, but it's finally ready to go, and I can't wait to watch it accelerate down the runway and lift off, hopefully uneventfully.

Oh yeah, remember this bit of tangled wreckage that I bought oh so long ago?

This is what it looks like now. All of the crash damage has been repaired, as well as the addition of Futaba 9252 digital servos on the swashplate, a GY401 gyro with 9654 tail servo, Throttle Jockey Pro RPM limiter from Model Avionics with a Spektrum crank pin sensor, Spektrum AR7000 receiver, shiny new Mavrikk pipe from Heliproz, 600mm Mavrikk carbon fiber main blades also from Heliproz, a header tank, all new fuel lines, new carburetor for the OS .50 SX engine, as well as a new Sport canopy from Compass Model. Oh yeah, and stickers, can't forget the stickers. All it needs now is a receiver battery and regulator, and it's ready to take to the skies. I'm currently accepting donations for the purchase of the remaining parts. ;)

It's been a productive winter here at the Big J Aviation production facility, which will hopefully lead to an enjoyable summer of flying.

Next up: The Slope Monkey by Wyoming Wind Works. Stay tuned!


Morgan said...

Groovy! At last!
Nice looking bird there. Looking forward to the flight report.

BTW I've added a forum on Mugi but it's not yet 'live'. Could you have a look and see what you think. Thanks, boss!


Justin said...

Will do as soon as I get a chance Morgan, been a bit busy lately at work so my 'puter time has been nil. Along with the couple last minute projects I'm trying to finish up before the official start of flying season. It seems that winter just won't quite let go, so I'm trying to make the most of it while it lasts.

I think a forum on the Mugi site is long overdue myself, so I think it's a great idea. The Yahoo group serves us well, but an actual forum would be a little less cumbersome to navigate, and might prevent some of the same questions from being asked over and over again.

Glad you like the Tea Racer. Sorry it took me so long to get it put together, but I'm sure flying it will be worth the wait. I'm hoping to generate some serious interest at our club fly in this year with it, which shouldn't be a problem once people see it fly and learn about how easy and inexpensive it is to build one.

Oh yeah, I added a tailwheel too, and as soon as I get a chance I'll put up pics. I kind of did it the hard way, but I'll outline for everyone how to do it the easy way too, which I would've done had I been able to find that blasted 1/16" wheel collar that I knew was rattling around in one of my parts boxes. Of course I found it the next day when I was looking for something else, LOL.


Justin said...

The forum is awesome! I went ahead and registered, dropped a quick post, and of course added you and your dad as friends. I'll upload some pics and such when I get some time, probably this weekend. This is going to be SOOOOO much better than the old Yahoo group, I can't wait until it starts getting more traffic. I'll hopefully be putting another post up here with the Tea Racer tail wheel pics soon, so when I do I'll go ahead and remind anyone that may be reading that you have a genuine Mugi forum now and command all 3 of my minions to go check it out, LOL.

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