Hobby Lobby Cessna 337 Skymaster Build Log w/Modifications - Page 4 - RC Groups
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This thread is privately moderated by gtfreeflyer, who may elect to delete unwanted replies.
Apr 19, 2007, 02:01 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
Appreciated. I'm still open to suggestions as this is my first foam plane, and 2nd electric plane.

I see what you mean about fitting it in the trunk. I didn't think of that since my trunk has been converted into an airplane hanger for my Super Sportster. Also, the CF tube is only 24" wide. My Skymaster gets the pleasure of riding on my cushioned backseat and enjoying my music and a/c with me. This is why I have to slide the CF tube over to one side; so that it doesn't poke into the seat.
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Apr 19, 2007, 06:08 PM
Women Fly Too
CrashCaley's Avatar

Flying the Skymaster

Guys, I hope you both get good weather coming through so you can fly your Skymaster. I got the chance a couple of weeks ago. Or should I say my resident expert flyer who always takes my airplanes up the first time or two to sort out the problems and let me know what adjustments I need. Even though it was in an unmodified state, it flew fairly well on stock stuff. Though it could lose a few ounces to pep it up. I'm still hoping like you that the weather will cooperate. Two weeks of wind so far. This airplane in stock mode can't be flown except in near calm conditions. Hoping for this sunday. Caley
Apr 19, 2007, 11:39 PM
No more Screamer
57_KID's Avatar
great thread . I recently bought the 337 on the sale , and mine was in worst shape than yours , the only control surface that stayed on was the left aileron , the glue ( silicone I think )that they used to assemble this airplane still isn't dry and I've had it for a month or more.
I got rid of all the plastic pieces that connect the wing and made it one piece with a carbon fiber wing spar, plane will fit in my car assembled so that's not a problem, pulled the elevator and rudder servo out to relocate them up in the wing , by removing all the bad stuff and replacing it with the good stuff I have saved almost a pound , mine weighed 46 oz's out of the box ready to go
I hope to keep it around 40 oz's not sure that I can build that light but I am trying.
other than the rear servos sounds like we pretty much will have the same setup only I will be using LI-Poly's and i will be posting a build thread after I have completed it and hopefully a video no matter what the outcome.
But all in all this plane is not for the beginner I have spent a lot of time just getting it to the point where I will feel that it should be a good airplane .
gtfreeflyer I am really glad to see that you have made this airplane a success.
Apr 20, 2007, 12:27 AM
Put a bigger motor on it!
gtfreeflyer's Avatar
I got to the field today and it was very windy again. We all just hung around, and about after an hour it died down a little, but not much. I spent the time reprogramming my SkyMaster. I can now shut off my front motor in flight! Since the plane is very bouncy and the front prop keeps hitting the ground on the bounces, I chose to use my aft motor as the "master". I also collected more data: Front motor by itself at full throttle pulls 175 watts, or about 14.5 amps! The same goes for the aft motor! This is not good since the motors are rated to 150 watts. However, with both motors on, I get about 275 watts for flight, and about 310 watts very briefly for takeoff. Not even close to the 350 watts I'd expect from the combined motors. I'm assuming I lose efficiency when both motors are running. Can anyone explain this to me as to why this happens? If my voltage stays the same whether I'm using 1 or 2 motors, and my combined amp draw is 27 amps instead of 29 amps (14.5 x 2), then my resistance must be higher. Why does this happen? Is this what's happening?

Anyway, after all that, I got my Super Sportster out and got 2 flights on it. After that the wind really came down to almost nothing! So I got 2 more flights on the Skymaster!

I taxied it out on the rear motor. This really seems to be the attention grabber. Everyone loved it. There were like 10 people out there today. When I had it set up pointed into the wind, I flipped a swtich and the front motor came to life. Full throttle and the plane flew awesome! The CF tube in the wing made a HUGE difference. The plane doesn't seem to "bounce" in the air anymore since the wings don't deflect anymore. I also did not use the nylon string for a wing spar today. No need for that.

I got some altitude and then shut of the front motor expecting the worse. At half throttle the plane still stayed level! Full throttle on one motor and I was climbing!

The landing was nice with only the aft motor on and flaps down. As the plane slowed down and rolled over the pebbles, it started its little dance and bounced all over the place, hitting the freewheeling front prop and stopping its rotation. No stress on the motor with the prop strike! This is the reason why I wanted to cut off the front motor.

For kicks, I taxied all the way back to the pits with the front motor off. I heard numerous, "Hey, the front motor is off, look! Neat!"

On the second flight, I did my first roll with this plane. It did it with no problem, but let's just say the plane does not like to roll. The plane just kind of falls back around once it makes it past half way thru the roll. I'll probably stay away from that again just to minimize crash risk. Besides, I have a Sportster for that stuff.

Now a warning for you all. I learned this today: Tip stalls are very common and happen easily! When turning the plane around, I banked it at about 80 degrees and pulled back on the stick to get a nice tight turn. This kills airspeed fast! My wing dropped, the plane was headed straight down, and my heart sank! You can't just pull back on the stick hard to get it level again. It needs to build it's speed back up first. So I had to add throttle while nosediving! Well, I had about another 20 feet to spare when I got it level again. Once I learned that, it never happened again. I never would have thought scale planes needed to actually be flown like scale planes...lol. I'm going to stick to 60 degree max banks from now on and make my turns lazy and wide. This plane actually looks better doing that anyway. It's a neat look when it comes around the turn. I ordered the CVS videocamera. I'll fix it up and get some footage for you all soon.

The second landing was, again, with aft motor only and flaps down. I got a really nice flat glide out of the plane just inches off the ground before touching down smoothly.

I taxied back again, and got the same reactions. People like to see something different.

Today was a good day.
Apr 20, 2007, 12:39 AM
Put a bigger motor on it!
gtfreeflyer's Avatar
...In response to Steve...

Nice post Steve. All my control surfaces also pulled out very easy and all the glue was still wet. Have you pulled the horizontal stabilizer out from the booms yet? Mine came out too easily. I epoxied it back in. 40 oz seems like a challenge! Are you using a rudder servo? It's nice to have the option of yaw control, but I still don't use it! With the twin fins, you really don't need it. Anyone want to back me up on this? The rudders are just not effective enough to make a difference on this plane.

After today I think of this plane as more than a success. I am really enjoying this plane more than I thought I would. It's nice to take it easy and relax from the high speed aerobatics at the end of the day and just cruise around with the SkyMaster. The flaps and separate motor control really added to the fun of this plane. I have to thank Vantasstic for that idea. Thanks!

Next up: Lights for evening flights!

These mods never stop! Help me I'm addicted!
Apr 21, 2007, 03:56 PM
Put a bigger motor on it!
gtfreeflyer's Avatar

We have monkeys!

These monkeys actually piloted the plane pretty well today. I got 2 more successful flights. I also got some video of a takeoff, flyby, and landing with my CVS camera. Now I need to hack it so I can download to my pc. Standby for that.
Last edited by gtfreeflyer; Apr 21, 2007 at 04:27 PM.
Apr 21, 2007, 04:44 PM
Women Fly Too
CrashCaley's Avatar
GT, Great to hear that you got two nice flights in. How were they power wise. Did you have sufficient power to take off without having to use 200 feet like the brushed system? What was the cruise throttle setting? Very interested as I'm still debating on whether to shell out the money to purchase the power system that you used. Caley
Apr 21, 2007, 05:18 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
Yeah, power is plenty. I do my flybys at 1/2 throttle while lighty pulling back on the elevator, not much at all. It doesn't stall like this. Otherwise, I'll cruise at 3/4 throttle. It's no rocket plane, but it's not too slow either. You can always try out different props til you get the speed you want. I don't want it to be any faster because I have another plane that takes care of that need. It will climb at 3/4 throttle too, but I like to push full throttle and climb at about 60 degrees. It will continue climbing like this until the air gets too thin. I don't think I can go vertical with this setup, but then again, this plane isn't built for that. I'm happy with this setup and I like the motors so far. I'm sure you'll like it too. No problems with them yet and I hope I won't see any problems. $54 for the motor and 25A ESC combo is a great deal from towerhobbies.com. My takeoffs could be about 20 feet if I wanted, but I like to slowly accelerate the plane. It looks more scale and I enjoy the scale aspect of this plane. Pushing the throttle forward slowly, I take off in maybe 75-100 feet. I'll get more videos next time.

Conclusion: Plenty of power to get you off the ground quickly, or out of a stall quickly.
Apr 21, 2007, 10:38 PM
RC Airplane Crasher
Awesome! Those monkeys really make the plane!
Apr 22, 2007, 12:28 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Love the monkeys. The flap sound neat too.

I flew my 337 again yesterday with two paralleled 1500mAh packs (older). Yech, my single 2100mAh 20C pack flew the plane much better. I guess I'll be sticking with the single pack from now on. I perfer having rudders though. I don't really use them much in flight on this plane, but I do use them to line up with the runway on landings. My rudder servo sounds like it may have a stripped gear, but seems to work fine. I'll have to look into replacing it...and probably replace the elevator servo at the same time. What size servos match these no-name ones?
Apr 22, 2007, 01:17 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
Don't know what servos match the stock ones. When I pulled the stock ones out of the plane, I plugged one of them into my receiver to test it out. When I moved the transmitter stick all the way over to one side, the servo arm seemed to "bounce" a few times when it hit its endpoint. I don't think I'll ever use the servos in anything. The Hobbico CS-12 servos are what I'm using. They have a lot of torque for their size and they aren't too expensive and they seem to be pretty accurate in matching your transmitter output.
Apr 25, 2007, 06:41 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
Add 2 more successful flights for the monkeys.

The flaps really bring her in gently. I'm going to try more flaps today since I think I'm only using about 20 degrees of flaps.

Anybody have any thoughts on using folding props for this plane? Are they as good as regular props? Do I lose efficiency? I've never used folding props before. Perhaps I'll just get one of those prop savers that the flying wing guys use. I don't want one on the aft motor, but I want the props to be the same and I thought it would be a good idea to put one on the front motor. The field I fly at is just too rough and the front prop hits the ground quite a bit on my landings. I don't want to add shock struts to this plane, but I may have to!
Apr 26, 2007, 02:36 AM
Put a bigger motor on it!
gtfreeflyer's Avatar

Eye Candy!

Got another flight in today in the strong winds. I didn't fly again because I just wasn't comfortable with those winds. Adding more flaps was no good. The model did not handle well at all. I had to land without flaps. I would say 20 degrees of flaps is ideal for landings with this plane.

Now for some pics I took while the wind was blowing...
Apr 26, 2007, 10:05 AM
Always Ready!
warhead_71's Avatar
PICS OF THE FLAPS, PLEASE!!!!! I was thinking of losing the rudder controls (just pinning them straight) since they seem to be mostly ineffective and it would be one less servo in the tail, and adding flaps instead - which seems almost necessary given the wing loading. Did you make full flaps or split flaps? Maybe even "spoilers" like a P-61.
Apr 26, 2007, 11:19 AM
Put a bigger motor on it!
gtfreeflyer's Avatar
I did not cut new flaps. I simply set up flaperons on my radio. When I flip the flap switch, both of my ailerons drop down about 20 degrees. This becomes the new neutral position for the ailerons.

To do this, you have to cut one of the preinstalled aileron wires since they are soldered together in parallel. Next, you add a connector onto the end of the wire you just cut. Now, one of my ailerons is plugged into the aileron channel on my receiver, and the other aileron is plugged into the flap channel. Most every computer radio has the preset mix for flaperons.

I know this is not as cool as real flaps, but there is just no weight to spare for extra servos.

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