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Scale BUSA Super Cub

TonyHallo

150cc
Spent most of today gluing in the side windows. Using .040" polycarbonate (Lexan) sheet. Much stiffer and more scratch resistant to PETG sheet. Using 560 canopy glue. The right side is already completed. Fuel tanks and batteries are next and I can put the plane on it's front paws and hind leg. Right now it is on saw horses. Might get it in the air for September. I really can't wait to start laying up the Cherokee mold.

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TonyHallo

150cc
The AR remote switch worked a few times then quit. I opened the fab and found the 27A 12v battery at 8 volts. Amazon delivered this today. Never heard of this size battery before, half the size of a AAA.

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TonyHallo

150cc
Aero Graphics cut the NO STEP, DO NOT PUSH, and NO HOLD graphics from their standard set of exterior graphics for the Super Cub. I know where the NO STEP goes, anyone have an idea where the rest belong? Only exterior I found on the Super Cub drawing site were for a military PA18.

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Attachments

  • Piper_PA-18_Super_Cub_Exterior_AeroGraphics_Placards.pdf
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TonyHallo

150cc
Have the engine installed and just about ready to fire it up. Working on the tail brace wires now. The initial weight and balance indicated a tail heavy condition so I decided to replace the stainless steel tail brace wires with titanium TIG filler wire. The wires on the top are the original SS wires, the bottom wire is a piece of 3/32" titanium filler wire. This is my first exposure to titanium, in machines and threads well. Putting 2-56 threads on the wire after reducing the diameter by .005". The total weight savings will be about 16 grams which leads to 2 ounces less nose weight or a total weight saving of 2 1/2 ounces. Two wires are completed, two to go.

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TonyHallo

150cc
Just got back from a week at Key West, the weather wasn't very nice! Scale contests are finished for the year and it is time to get with building. I need to get this Super Cub off the bench so that other projects can start. It is time to think about running the engine and I thought a tach would be nice to set the carb up. On four strokes you don't want the butterfly opening beyond the point where the engine speed no longer increases. It nice to observe the rpm reading after reducing the endpoint to where the rpm just begins to drop. Valach recommends opening the carb 60%., the Roto manual doesn't address this. There are two maneuvers that I was using that require a rapid increase in throttle position, the Chandelle and the Overshoot. During both of these maneuvers I would experience a bog when the throttle was advanced, never noticed this until practicing the maneuvers. I had the butterfly set to full open. I happened across the Valach recommendation by accident and decided to give it a try, I also put a 1 second delay on throttle opening while the throttle closing is full speed. Both of these changes eliminated the bog.
I could not determine what Roto uses to trigger the ignition so I decided to add a Hall sensor and magnets to the engine. I pulled the prop hub and surprised to find it is a straight bore and not tapered. It came off with a little heating with the puller engaged. 1 1/2" pvc pipe was used the make the Hall sensor holder ring as shown in photo below while actual holder was cut off a commercial ignition holder. This is attached with rubberized CA, seems to hold well. 1/8" x 1/16" rare earth magnets were ordered from Amazon and should be here on Wednesday, these will be installed after the hub is reinstalled since heat man damage the magnets. Installing two magnets 180 degrees apart to improve low end resolution. The tach in the Champ drops out at 1000 rpm.
I tested the Roto trigger sensor with a VOM and found a meg ohm resistance between each wire, also checked with a DLE ignition tester and could not get any trigger for both south and north magnets. Proping the engine over with while measuring the voltage found nothing as well. I don't knows what's inside but I sure hope it runs.

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ignition
 
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TonyHallo

150cc
Got the plane assembled and weighted, 33.33 pounds on the mains and 4.41 pounds on the tailwheel, 37.7 pounds total. Haven't checked the CG yet but low tailwheel weight is encouraging. Taking the boss's cat to the vets and it takes two of us to get her in the cage. Will check the CG later today.
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TonyHallo

150cc
Well the vet was a $700 trip plus $8 a day for special food to dissolve a bladder stone, hope it works. Even after getting two rectal exams at the vet's, cat still didn't want to get into the pet carrier!
Got the plane leveled and balanced checked. The CG is 6.42" back from the leading edge or 30.6% of span. The plans show the CG at 5 13/16 back or 28% of span, I'm happy were it landed.
I think I will run the engine today and set the carb.
 
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