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Building Tips and technical articles. => Building techniques => Topic started by: jerry v on September 23, 2021, 09:53:49 PM
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I was presented with Brodak P-40 ARF kit for my birthday.
It was sitting in the box since the spring. And then I decided to build it for participation in Cleveland, Ohio competition in profile event on September 25-26 .
Project took me four days.
Jerry
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I started this project on Monday September 20th. First test fit all components. Tighten the covering, cut all openings for stabilizer. I used Du-bro nylon hinges #117 for flaps and for elevator. I used CA hinges only on adjustable rudder. I replaced the kit flap wire jointer with .093 in music wire. Flaps installed on Monday.
Jerry
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Tuesday was for glueing the wing in place. Cut the covering in the joint area, used 30 minutes epoxy, set the wing on the glass tabletop. 1/2 inches spacers/blocks under the wing spar in the area of the ribs on the closer to wing tip flap end. Square blocks to hold the fuselage perpendicular to table. And square to check perpendicularly of the fuselage sides and the hinge line.
Jerry
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On Tuesday I glued hinges and the jointer in the elevator and stabilizer. I replaced kit jointer wire with 3/32 (.093) inches music wire.
Jerry
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Wednesday. Glued all tail in place. Cut the block of balsa to slide stab in place. Used 30 minutes epoxy on stabilizer. Jig was the same for the wing and fuselage. Only blocks of the same height and equal distance under the stabilizer .Used 5 min epoxy on the vertical fin, CA on the rudder hinges. Used bamboo 1/8 sticks to pin vertical fin, stabilizer and fuselage together with epoxy. Rudder is adjustable with Du-bro 4-40 ballinks.
Jerry
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Jerr-O,
I have seen those fly really well! I hope you are pleased with it!
Divot
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Rudder.
Assembly of the undercarriage in the time of glue drying.
Jerry
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Thanks, Dave!
Thursday was just assembly of everything)). I used one single piece of 2mm (.079 inches) music wire to connect flap and elevator control horn. O, I forgot, I reinforced the belcrank plywood bracket with balsa sticks and epoxy between wing sheeting and ribs. I saw the belcrank being pulled out before.
It is better to use offset control horn on the flap. But I used one from the kit and bent the push rod wire to clear the flap in the “flap up “ position.
Jerry
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Engine - OS .40 FP with stock muffler for the correct CG. RC carburetor with permanent linkage to keep “full throttle “. Recommend tank. Used the clear scotch tape to cover the openings on the 4-40 blind nuts installation. 5 min epoxy smeared in those pockets.
Weight without fuel is 51.5 oz
Jerry
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Thursday 4 o’clock PM I was at the field to break in the engine and to do the maiden flight. CG was in the recommended position without any lead. Tip weight as recommended- 1 1/2 oz. First flight was regular settings on the tank, as recommended. Now I use muffler pressure for more consistent engine run. Line length 60 ft, lap time 4.9 seconds now, handle spacing is 3 3/4 inches. It’s a bit tail heavy in the end of flight on empty tank. Even with line spacing 3 3/4 inches sometimes I over control this P - 40 on landings. But it makes corners easy.
Jerry
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It’s a nice model! Quick and easy to assemble.
Jerry
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In Cleveland Area Stunt Championship on Saturday September 25 my P-40 flew to the 3rd place. In ARF/ARC category. It was its 6th and 7th flight since maiden, flew tail heavy, not properly trimmed yet)). Engine is still under work to performance.
As glow version this model flies great, it goes where you control it. I did not see any vertical CG problem, as described by some pilots who flew it as electric.
For now I will try aluminum spinner to shift the horizontal CG forward.
Jerry
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Congrats on 3rd, you should get extra points for a warbird. Is that your Tanager? just wondering how much it weights.
Motorman 8)
Motorman,
Thank you!
P-40 weight 51.5 oz dry. Tanager is my brothers work horse. He flew it in profile and in intermediate category. Tanager weight is 47 oz dry. Both models have OS .40 FP engines and APC 10x6 props. In windy conditions they performed well.
Jerry
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Motorman,
Thank you!
P-40 weight 51.5 oz dry. Tanager is my brothers work horse. He flew it in profile and in intermediate category. Tanager weight is 47 oz dry. Both models have OS .40 FP engines and APC 10x6 props. In windy conditions they performed well.
Jerry
From my experience ( both with the P-40 and the OS 40FP), the FP will be much happier with something more like an 11x4.5, it likes to turn rpms, running it 4-2-4 is not generally going to give you consistant runs, nor will the engine be happy
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Looks great and a good report. Now trim it to fit your style of flying and have fun. H^^
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Thanks, Dave!
Thursday was just assembly of everything)). I used one single piece of 2mm (.079 inches) music wire to connect flap and elevator control horn. O, I forgot, I reinforced the belcrank plywood bracket with balsa sticks and epoxy between wing sheeting and ribs. I saw the belcrank being pulled out before.
It is better to use offset control horn on the flap. But I used one from the kit and bent the push rod wire to clear the flap in the “flap up “ position.
Jerry
Hi Jerry,
How did you bend (90 degree) the pushrod from belcrank to the flap control horn?
Did you just use pliers? Or did you use some other tools?