Hobby Lobby Cessna 337 Skymaster Build Log w/Modifications - Page 3 - RC Groups
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This thread is privately moderated by gtfreeflyer, who may elect to delete unwanted replies.
Apr 16, 2007, 01:49 PM
Women Fly Too
CrashCaley's Avatar
GT, Thanks for the information. I guess the red wire is the hot one and removing it allows the signals of the esc to work, but you get no juice from the flight battery. I think that the FRIO combo is a great deal from T.H. Hope I can scrape up the money for a couple of sets. Meanwhile, I will just have to fly the airplane as is and hopefully keep it in one piece. Caley
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Apr 16, 2007, 03:12 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
I just got this nice chart for the Frio motor I'm using off of www.peakeff.com The data has been collected by many different users.

The 9x6 wood Zinger prop is not on here, but I would expect it to fall around 15 amps. This means I'm pushing more than 150 watts into the motor at full throttle, and it's only rated for up to 150 watts. It looks like I'll have to change my prop sooner than later if I plan on keeping my motors around for a while.
Apr 16, 2007, 11:04 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
I got 3 more flights in today! I took some video with my cell phone camera, but I'm not going to even bother posting it on here. The quality is horrible. I'll have to find a camcorder.

My 2nd and 3rd flights today were all touch and goes the whole time. I'm still learning how to bring her down gently. I put about 10 more landings on my resume' today.

The landing gear is VERY SPRINGY! No matter how perfect my approach and touchdown were, the plane would hit a few pebbles and bounce around like crazy as the plane slowed down. I probably averaged 2 or 3 prop strikes per landing...lol. I'm surprised the wood props held up. This plane is meant for concrete. I did land on the concrete walking path nearby for one of my landings, and it was textbook perfect with no bounce.

My last landing of the day was a hard prop strike on the front motor that tore the firewall out. The wood prop still has no damage..haha. I'll reapply epoxy and she'll be ready to go again. No big deal, just annoying. Now I have to figure out how to build very light shock absorbers.

The plane is still a bit heavy for my liking, so I'll probably take out the rudder servo and enable one of the BECs so I can also eliminate the NiMH battery in the plane. The BEC should be able to handle 4 servos.

Alright, that's it for now. I'm still learning as I go.
Apr 16, 2007, 11:31 PM
RC Airplane Crasher
To be totally honest, this plane doesn't sound like the kind of plane I would like to own myself.

HOWEVER, I have really enjoyed reading about it. It sounds like a real interesting unusual plane and an interesting project for you. Keep us updated on how it goes, I want to see a video!
Apr 16, 2007, 11:44 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
To be totally honest with you, I would have never bought a plane like this if it wasn't for the $59 price tag. I'm not really into these scale flying planes. I need adrenaline. I like fast and inverted flight. However, this is my "Sunday Flyer"... that I've now been flying everyday and fixing every night...lol. It's also my first foam plane... something I thought I'd never own. I'm enjoying the modification process, it keeps me interested. It's a great feeling see it all come together and work out in the end knowing that you made it do what it does.
Apr 16, 2007, 11:56 PM
RC Airplane Crasher
Yeah I think the project aspect especially converting it to brushless, makes it interesting, especially with details and upgrades. It is a unique looking plane and a head-turner.
Apr 19, 2007, 12:54 AM
Put a bigger motor on it!
gtfreeflyer's Avatar
It was CRAZY windy today! I didn't get any flying in, but I used my time to make more mods and collect some data.
Apr 19, 2007, 12:59 AM
Put a bigger motor on it!
gtfreeflyer's Avatar

Static test with the 9x6 wood Zinger props:

I didn't have a full battery at the time I took this measurement, but for now you'll get the idea of the power I have.

From the reading...

290.4 Watts

I'm definitely pushing more than 300 WOT.
Apr 19, 2007, 01:10 AM
Put a bigger motor on it!
gtfreeflyer's Avatar


Everything in the fuselage except the NiMH battery & props: 20.00
Tail and booms with 2 servos: 8.25
Left wing: 3.65
Right wing: 3.50 (Don't know why they're off)
2 Zinger 9x6 props: 0.90
LiPo: 5.50
NiMH receiver battery: 5.85
CF tube for wing: .35

Total weight at takeoff = 48.0 ounces = 3.0 pounds! What a nice even number.

2 stock props weigh .50 ounces
2 APC electric props weigh 1.2 ounces.

I thought the wood props were heavier!

If I take out the rudder servo and use one BEC, I can eliminate 6.47 ounces and therefore add ~15 watts/lb. I may do this in the near future.

Conclusion: 100 watts per pound was acheived!
Apr 19, 2007, 01:30 AM
Put a bigger motor on it!
gtfreeflyer's Avatar

Carbon Fiber Tube for wing...

I'm using a .188 OD x 24" long CF tube here since it fits PERFECTLY in the wing.

Remove the bottom wing panels on the center section (see picture)

Drill 3/16 holes (.188 holes) in the middle of the plastic piece that plugs into the outer wings. This must be drilled perfectly in the middle for everything to slide together nicely. One of my holes was a little off and I had to enlarge the hole a little. Now my fit is not as snug as it could be.

Take a .188 OD brass tube and insert an exacto knife in one end of it. Keep turning it and sharpening the edge. When done, insert it into the center wing section thru the hole you just drilled. Now push it thru and make a path for the CF tube to slide into. You will have to go thru where the wing mounting bolts go.

Now you must reattach the center wing section to the fuselage with the 4 screws.

The center section has dihedral built into it, so it's going to be tricky to insert the CF tube all the way thru. However, just follow this easy procedure to do it easily.

Insert the CF tube in thru one end. It will pass directly over one of the screws holding the wing on. You can probably push it over to the next screw easily. You can look into the screw hole to make sure it is there. Keep the end of the CF tube in view over that 2nd screw. Now from the other end of the wing, insert a wire. I had a threaded pushrod wire of a small diameter. Insert this all the way thru, and INTO the CF tube. You can look into the screw hole to get them aligned. Now you can use it as a guide as you push the CF tube all the way thru the other end!

You don't have to do ANYTHING to the outer wings. They have a .188 ID tube already in them!

The wing now feels ROCK SOLID. I can not wait to go fly it. It is almost feels like a rigid balsa wing now.

I'm curious as to how the plane will fly with less dihedral now. It may be more agile and fun to fly. I'm going to hope for that.

The only down side to this mod is that the outer wings are now very hard to remove at the end of the day. Everything is such a close, tight fit. It took me about 5 minutes of slowly pulling, twisting, and doing whatever to get the wings off. In my opinion, this is a small price to pay for the added insurance I just got on my wing!
Apr 19, 2007, 01:37 AM
Put a bigger motor on it!
gtfreeflyer's Avatar

The guts

Here's a picture of my plane's guts.

From top to bottom of the picture:
-Wing leading edge.
-Receiver wrapped in 1/4" foam to protect from vibration
-5 cell NiMH battery for electronics
-Nosewheel steering servo and piece of velcro for LiPo battery
-Custom plywood firewall. You can now see how much right thrust I had before I shimmed the front motor.
-Frio 10/10 motor with Zinger prop.
Apr 19, 2007, 01:42 AM
Put a bigger motor on it!
gtfreeflyer's Avatar
When I replaced the bottom panels on the center wing sections, I could not get the original tape to stick back onto the foam. I used electrical tape to hold it on there and it sticks really well. I then noticed that it looked really awesome! It looks like I now have a de-icer for my wing, so I applied electrical tape to the entire leading edge of the outer wings too. This should also help lessen the amount of "dings" I get on the wing. I didn't plug the wing in all the way for the photo just because it's a P.I.A. to get it back off. Check it out.
Apr 19, 2007, 12:40 PM
Always Ready!
warhead_71's Avatar
Originally Posted by gtfreeflyer
The only down side to this mod is that the outer wings are now very hard to remove at the end of the day. Everything is such a close, tight fit. It took me about 5 minutes of slowly pulling, twisting, and doing whatever to get the wings off. In my opinion, this is a small price to pay for the added insurance I just got on my wing!
You got me thinking... perhaps it would be easier to cut your CF in half and glue each half permanently into the outer wings. Then make a "joiner" inside your fuse that could fasten both halves together. The joiner could be something as simple as a piece of copper tube, with holes drilled through it and the CF ends so you can use set screws or cotter-pins to secure them.
Apr 19, 2007, 01:48 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
No, that wouldn't make it any easier to remove the outer wings. It is tough to get the outer wings off because you can really wiggle them much as you pull. With the CF tube connecting the outer and center wings, the only degree of motion you have is to pull the wing straight out. You can't really get any rotation (a.k.a. wiggle the wing). It is the nice, snug fit that makes it difficult to remove. In the air, a snug fit is much better than easy removal!

I like the idea of the CF tube remaining in one piece. No need to cut it. The CF tube stays in the center section of the wing and does not get removed. The outer wings plug onto it.

I can slide the CF tube left or right as much as I need to get it to fit in my car properly. I'll just recenter it before flying. Hopefully I don't slide it over too much or else I'll have to use the wire pushrod trick again to get the CF tube back thru.

I was looking at the wing as a whole, and it does still have a little dihedral in it. The CF tube does curve slightly in the middle due to the way the center wing section was formed. The CF tube is slightly preloaded like this since it wants to be straight. This keeps it from sliding out on its own.
Apr 19, 2007, 01:52 PM
Always Ready!
warhead_71's Avatar
I just thought it would be easier to fit in your trunk if the CF came out with the outer wings instead of sticking out of the fuse. Plus, you can still have dihedral by bending the joiner tube... it was just a thought.

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