Modular Test Platform Maiden Flight

This week I took the Modular Test Platform (MTP) for it's maiden flight, I can't tell you how nervous I was to give it it's first throw, or how excited I was when I saw flying through the air! You all probably know what I mean.

I got 2 or 3 "OK" flights in (20-30 seconds) before it had gotten beaten up enough to not really fly anymore. With each crash though, I was expecting more damage, but those wooden dowels really add a lot of strength and rigidity, while the foam and hot glue give it some flexibility. Eventually, the motor section got so crushed that the motor was too unsecured to make additional flights.

The needed improvements are:

1.) Improve CG: at first it was tail heavy, causing the airplane to "high alpha" and not allow the wings to really generate lift. As I moved the battery toward the nose to shift the CG, things got better and better.

2.) Reduce control surfaces: even the smallest movement of my transmitter sticks would make the airplane almost lose control as it exerted a LOT of force. Either (or both!) the control surfaces need to be reduced in size or the throws need to be reduced.

3.) More power: the brushed motor, 10C NiMh x 7.2v battery, and 10 amp ESC set up has got to go. It was taken from a wild hawk, and while functional, the power system is heavy, weak, and inefficient. The new system will have a brushless motor, 20C 11.1v LiPo, and 30 amp ESC. I've already bench tested it and it has at least 5 - 6 times the thrust.

4.) Wing incidence: I also think adding a little angle on the wing will add natural stability and climb.

Next week I'll be making these and other improvements to the MTP. Anything I've missed?

Move the CG forward quite a bit. You are carrying alot of dead weight with your tail arrangement. I think you should shape the tail and make it solid, rather than detachable to save some weight back there. Then you can reduce the length of the nose on the other side of the CG. I suspect you have it like that to counter the weight of the tail!

If you do add weight ie the camera rather add it in front of the CG better than behind.

You don't need to worry about expos, just push the sticks less. Reducing the size of surfaces will help to move the CG and the over control issues, would be simple as well.

As I have said before the only thing to add is lightness.

Not sure but you might have tipped stalled in on that first incident, so a little more speed in the turn.

I predict at the end of this series you will have a very capable airframe.

Well done.

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Comments

Russell B. Sutton June 19, 2011 at 8:38am

CG point can be found anywhere from, say, 25% to 50% of the wing chord back from the leading edge. A CG point outside of that range is rare, but not impossible. I've started a new scratch built airplane using 1 1/2 thick foam and arrow shafts. I'm on my 2nd fusalage so far. As I was mocking up the tail fins to the boom and fusaage I noticed that I needed a longer nose to be able to move the battery and motor further forward to counter balance for the tail fins. when I build from scratch I constantly weight and check the balance of my design so that in the end I'm not adding dead weight to counter balance my plane. I start with a CG between 30-35% back from the leading edge. I use velcro on the battery so that I can us it to change the CG a little bit if needed.
Trent at MyGeekShow June 19, 2011 at 6:06am

I had a lot going on this week, and only had an hour or so to do my geek show. I tried a flight but didn't get the CG right and nosed it quick. I'll give it a better shot this week as well as start on the next airplane.
Brandin Sloms June 13, 2011 at 12:55pm

I like this kid
Trent at MyGeekShow June 12, 2011 at 7:26pm

Thank you all for your support and recommendations! Updated power plant is already being installed... Weight is 16 oz (450 grams)... My Tx doesn't have expos, too cheap! (But its all I have at the moment...).
Thon June 12, 2011 at 7:55am

Try this for an inexpensive motor/speed control combo:
https://www.graysonhobby.com/microjet-combo-microjet-p-765.html

or

http://www.graysonhobby.com/catalog/grayson-hobby-microjet-flight-p...

Which will also get you 2 servos, a battery and a 6x4 prop.
I have used the motor/speed control on a bunch of home designed aircraft.
Moderator

Gary Mortimer June 12, 2011 at 7:47am

Move the CG forward quite a bit. You are carrying alot of dead weight with your tail arrangement. I think you should shape the tail and make it solid, rather than detachable to save some weight back there. Then you can reduce the length of the nose on the other side of the CG. I suspect you have it like that to counter the weight of the tail!

If you do add weight ie the camera rather add it in front of the CG better than behind.

You don't need to worry about expos, just push the sticks less. Reducing the size of surfaces will help to move the CG and the over control issues, would be simple as well.

As I have said before the only thing to add is lightness.

Not sure but you might have tipped stalled in on that first incident, so a little more speed in the turn.

I predict at the end of this series you will have a very capable airframe.

Well done.
Russell B. Sutton June 12, 2011 at 7:22am

Whats the flying weight of ur setup? 700 grams?
Russell B. Sutton June 12, 2011 at 6:29am

Awesome! I love it Good Job man. I was so glad to see you really got it flying.
Brushless and LiPo setup would be the best improvement. CG needs to be moved forward a bit more. Remember keep it light and strong. Magnets are great but add lots of un-need weight. rubber bands or just some tape might be better. The more weight u add the faster the wing will need to fly to create the same amount of lift. Also the battery must work harder witch will reduce your flight times. Strong, light, and lots of un-needed power is good rule of thumb. 1 to 3 Thrust ratio is ok for large aircraft like a 737, but sux for RC. 3 to 4 thrust ratio is great for all basic craft.
S.G. Sutter June 12, 2011 at 5:52am

You're making great progress, Trent! Well done.

For point 1, a finely balanced CG will definitely help you. Point 2, could you adjust the expos on your transmitter to give you more fine control over the surfaces? Point 3, wow, yes, an updated powerplant will definitely help.

Personally I would hold off on #4 until you see how #1 - #3 impact your performance.
d-creator June 12, 2011 at 5:42am

I like it! in fact im doing something similar but not so modular (based on MAJA design). but first i need to finish my foam cutting machine, cutting circular forms by hand is way to difficult.

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