SA re-Run Chuck Glider RC Conversion

[rockyboy]

Two weeks ago at an indoor fly-in I talked to a guy (forgot his name - not good with those) who converted a re-Run chuck glider from Stevens Aeromodel into a radio controlled flyer with electronics from a busted up Champ UMX. And I just happen to have been gifted a busted up Champ UMX recently. Serendipity strikes!!

The main points of the conversion are adding a pylon motor mount above the wing with the motor hanging forward to give the propeller plenty of clearance in the cut-out section of the fuselage. The receiver brick gets recessed into the side of the body (it's plenty thick) and some slicing and hinging create control surfaces on the existing tail section.

So the kit arrived yesterday, and sanding and glueing is coming soon. Just need to find an old floppy disk for hinge material...

 

[Amcknight31]

Nice! You might be able to change it to a sloper or even a motorized one...

 

[NatefromOgden]

We obviously think very much alike because I would happily build that and make it powered. I don't have a gimme Champ to cannibalize but if my Sport Cub S ever fails me, I'd have the guts for a powered version.

 

[Amcknight31]

Haha, yep, that's the way!

 

[rockyboy]

So my memory of looking at the other glider that worked, and how I ended up building mine were quite a bit different as it turns out. The biggest thing was I didn't realize he switched the propeller out for a tiny 3" one from the original Champ prop. So I had the motor mount pylon way too high for the bigger Champ prop, which put the center of (thrust/pressure?) way up - possibly even above the airfoil.

So as a result, it wouldn't track straight on the wheels to take off, and the maiden hand launch flight was an instant flop into the gym floor. The only damage was the motor pylon snapped - which is handy really, cause it was too tall anyway. I have new 3" props on order and will reconstruct and re-maiden soon.

Pictures of what not to do - because it looks pretty but doesn't work - below.

Also, the control surfaces were way too small compared to the other model. I'm going to increase the size of both elevator and rudder before putting her back in the air again.

 

[Amcknight31]

Looks great! Where do you buy the actuators?

 

[rockyboy]

I used a PKZ3352 receiver/servo "brick" from a Horizon Hobby UMX Champ that crashed one to many times. These can be found as replacement units on eBay, Amazon, Horizon Hobby, etc for about $50us

There are some cheaper receiver/servo bricks (think $10-$14us) available on Banggood or Gearbest made by WL-Toys that aren't Spektrum compatible - they require a FlySky transmitter or radio module (anywhere from $15-$40). I'm using those for a couple other micro-indoor builds and they work OK, but they are a lot taller with traditional style rotary actuators instead of the lower profile linear styles.

 

[JohnRambozo]

I used a PKZ3352 receiver/servo "brick" from a Horizon Hobby UMX Champ that crashed one to many times. These can be found as replacement units on eBay, Amazon, Horizon Hobby, etc for about $50us

There are some cheaper receiver/servo bricks (think $10-$14us) available on Banggood or Gearbest made by WL-Toys that aren't Spektrum compatible - they require a FlySky transmitter or radio module (anywhere from $15-$40). I'm using those for a couple other micro-indoor builds and they work OK, but they are a lot taller with traditional style rotary actuators instead of the lower profile linear styles.

Looks great. Don't forget to angle the motor some to prevent another nose in. Even with a lower mount, a tractor above the wing need the thrust angle up a bit to compensate for the tendency to pitch around the cg.

 

[rockyboy]

Thanks for the tip John! I was wondering about that. I have it all rebuilt and ready to go for another test flight, just waiting for an indoor fly-in or a really calm day to test out the changes.

 

[JohnRambozo]

Thanks for the tip John! I was wondering about that. I have it all rebuilt and ready to go for another test flight, just waiting for an indoor fly-in or a really calm day to test out the changes.

No problem. Josh talked about it in a video I watched recently. But it makes sense once its pointed out.

 

[rockyboy]

All fixed up and ready to try again - next indoor event nearby in two weeks.

Smaller prop...


Larger control surfaces...


I only had so much scrap balsa of the right thickness in the baggie, so I built elevator extensions instead of replacing the whole piece. I like the way it looks, we'll see how well it works soon enough.


Again using the TLAR (That Looks About Right) method of adjusting motor angle. Like the bottle says, lather, rinse, and repeat.

 

[Joker 53150]

That is really a neat looking little plane, hopefully the changes work well!

 

[rockyboy]

So I finally made it to a gym for some indoor flying last weekend.

Things didn't go as well as I hoped for this model.

When I brought the motor mount down closer to the wing to line up the thrust angle better, I also switched to a smaller propeller so it would clear the fuse. Turns out the smaller prop I used just doesn't produce enough thrust to get this up in the air. With a ROG takehoff, it moved across the gym pretty quickly but never did the 'takeoff'. I tried a low toss, it immediately went in for a bumpy landing, and then the motor mount glue broke free.

So it's back to the workshop for this one. Time to make a stubbly little motor mount (with just a touch of up angle) to give it just enough clearance to go back to the stock prop. Since I just got my new 3d printer working this weekend, I might try designing a thin wall mount with a couple different height options so I could switch between them in the field.

 

[rockyboy]

SUCCESS!!!

And of course, today the video camera battery was dead so no proof. But she flew great! I took the motor mount a little bit taller than the last run, and moved back up to a standard sized UMX Champ prop with about 1/2" chopped off the tips to create a bullnose prop. Plenty of power now!

I need to get a tail wheel installed as the drag of the tail hook causes it to spin in crazy ground loops when trying to take off. My working technique is to lift the tail off the ground, give it half throttle, and give it a push to get some speed going. With that crazy ROG process, she takes off smoothly and flys excellently! Will get video next time