RC Build: Clipped Wing Cub

[Younggun]

I was a little worried, but one I set the wing on with the engine mounted and it put weight behind the wheels I felt more comfortable with it.

That, and there's lots of room to move stuff to the rear of the cabin and I can't afford the super light high end servos, something like $70 each, so I get the heavier old school servos for $10. Quite a bit of weight to move around. Probably about 5oz between the servos and battery.


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[Younggun]

Progress!

Got the fuel check valve and remote glow igniter in the mail. Fuel valve will be mounted at the top of the firewall allowing easy fueling and will be in a similar position to that of a full scale J3, remote glow attached and will be mounted on the side of the fuselage.

Also got the top of the nose sheeted and sanded.

Vertical stabilizer is mounted, as well as tail wheel and longerons installed down the top of the fuselage behind the wing. Waiting to Dow the ones on the side for easier access when installed push rids for the control surfaces.

Got the wing and ailerons covered as well, only need to cover the access panels for the servos.

Will be working on the servo tray soon so the push rod situation can be figured out. Won't make it permanent until the plane is complete enough to be balanced since the servos and battery will be shifted to move CG. Can't install the Horizontal stab until after covering the rest of the plane. Need to paint the inside of the cabin and the firewall soon as well so the covering can happen. The push rods will be pulled out and cut to proper length.

It's getting close, but getting to where things need to happen in a particular order or they will prevent access to something else that needs to be done.


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[Younggun]

Far enough along to get an idea of where the CG will sit. With servos at the back of the cabin and battery just behind the mid point CG is at the forward most point on the range. Should move back by the time I get covering on and add push rods. Looks like I'll be fine with just a little room to play. I will have room to move the battery back about 4" if needed also.


Worst case I would have built the elevator and rudder servos in to the fuselage behind the cabin, but that won't be necessary.


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[orbitup]

Coming along!

 

[Younggun]

Yep.

Spent most of this evening working out the best path for the guide rods. It's a pain getting them to come through the side at a shallow enough angle to hit the control horn without bending too much. Using a flexible system but it can go far without support it flexes and looses travel.

Just though about a bell crank system that would be pretty cool though, so may redesign the whole thing.


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[vmax]

you can put the airplan on scales and do some rough calculations on your CG
you might be a little off if you do that, but not catestrophic

 

[Younggun]

I usually just go off recommender CG and put a couple marks under the wings with a dry erase marker, then pick it up on those marks with my finger tips.

Never bothered with balancing from side to side.


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[Jakashh]

Went to the Museum of Flight yesterday in Seattle.

Here's some inspiration

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[Younggun]

Need better pics. Climb up there and get pictures of the control linkage for the elevator and rudder. Get some pics of the cockpit too. Thanks!


Got my bellcrank system worked out. Used some extra servo arms. Drilled them out and used pieces of 1/8" brass tube for a bushing. Pics were hard to get of the actual bellcranks.

Will look a lot nicer than a pushrod sticking through the side of the fuselage.


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[Younggun]

Not much today, just some tinkering. Figured out where the mounting points will be for the cowl, got them cut and shaped. Cut out a servo tray, didn't cut the position for the throttle servo, marked where the rails will go that it will sit on. Looked at how the guide will work for the throttle push rod and kicked around a few idea for connecting to the carb and servo.

Nothing worth taking pictures of.


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[Younggun]

Oh, and I glued the bellcranks in and the backer pieces for the covering where the arms will come through.


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[Younggun]

Work got slow on this for a while but lots of updates.

Servo tray mounted and servos installed

Pushrods installed and set, floor glued it. Fuselage is pretty much done.

Partially covered the fuse, covered and installed rudder and elevator.

Horizontal stabilizer installed, tail section covered.

Finished cutting cowl and set mounting points.

Installed wood blocks at the top of the cabin. Finished painting cabin.

Cowl painted

Cabin door built with homemade latch

Windows and windshield installed. Spinner and prop installed to check fit.

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[Younggun]

Wing struts done, just need paint.

Ready to break in and tune the engine, will paint the struts and let them dry while that's going on. Going to do the taxi testing before finishing the landing gear cover in case I need to make any tweaks. Will put the cowl back on after tuning is done.


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[Davetex]

Oh Yeah, that's a cool little plane.

 

[Younggun]

Engine ran for the first time today. Aftter digging around and finding 3 separate glow igniters dead I eventually got enough of a surface charge on one to fire it off. Ran two tanks to break in the engine, hopefully start tuning tomorrow (with good batteries in the igniters)

Short vid due to crap service out here. 4 stroke sounds sweet though.



Gonna be tough getting the exhaust tight. Vibrated loose twice after tightening it down. Probably gonna have to cut another slot in the cowl to get a wrench in. The exhaust pressurized the tank and loosing too much will cause the engine to lean or stall.


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[Younggun]

Tried to tune the engine last week and the engine mount cracked. Mostly my fault. I thought it was regular plastic when I first mounted it and tried to thread the screws in, they cause it to chip. Thought it only cracked where the screws came out but I guess it was worse.

Ordered a new one from sig (planes) last wednesday, came home from vacation today and it was here. Nice fast shipping, esp considering it was $10 for a $3.50 part.

Thought I ordered the same as I had but I guess not. Looks like the mount that comes with the model is for an engine half the size of what I have on it. Holes didn't line up and had to do some extra work to get the engine as close as possible to the original position due to the cowl being cut for it. It's close, but maybe just slightly lower.

Got the engine tuned pretty well today, might use a tiny bit of adjusting, slightly lean the low end, but overall running really well. Taxied out of the grass, made a circle in the drive, and back to the grass. No nose over issues and the large prop and 4 stroke really pull well. Moved through the grass with ease at 1/4 throttle.

Will do some high speed taxi testing when I can, make sure it tracks straight and get an idea of how quick it will come off the ground. Probably burn a tank or two just back and forth on the runway, make any final tweaks to the tuning, mount the cowl back up and do any final trimming needed since the engine remount, and she's ready to fly.

Really nice the first time it moves and you don't have your hands on it (aside from the times it almost falls off the work bench).


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[Younggun]

Getting about 9,300rpm on the 12X6 wood prop. Probably be closer to 10Krpm once the engine is fully broken in.


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[Younggun]

Did some more tuning. Only pushing 8500 static rpm now but engine seems to run much more reliably.


Did some taxi testing earlier today and the wind was kicking it all over the place on the ground, couple times rolling on a wing tip, main wheel, and tail wheel.

Wind died this evening so I went out with my lovely daughter and videographer, Miss Kaylea.

Was pretty shaky but got the trims set and things settled down. Made a couple passes and came around to make a landing that wasn't pretty, but didn't cause any damage. Will upload the vid when I have better service.


I will say that it was unexpectedly nimble. Will be a fun plane, but madebit a handful until trimmed. Lots of rudder authority. Could use some downthrust, may have to shim out the top of the engine mount.


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[Younggun]

Vid of maiden




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[Coiled]

I've been watching this thread. Damn nice job on both you and Kaylea. Sweet plane!