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Dec 19, 2019, 09:40 PM
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Stevens RV-4 laser cut balsa kit

Some of you may have seen my just finished built-up balsa kit of the Stevens RV-4. Here are some notes I've put together while building and after the first couple flights... Garry Finlay

This is a neet little 1/8th scale model of the Van's RV-4 high performance "home-built" sport plane. It's an open framework, laser-cut balsa kit covered with polyester film, making it straight, strong and light. With a 35" wingspan and 11oz/ft wing loading it's maneuverable and easy to fly in small spaces. An inexpensive power system and flight components make this a good plane for intermediate experienced builders and pilots

This kit is 100% user built, and it's a bit of a challenge. The instructions have a few "soft spots". Study the plans carefully and double check each step before gluing and moving forward. If built well, it will look good and fly great. Here are a few things to pay extra attention to:

Build light, don't add extra features, reinforcements or use too much glue.
When assembling laminated parts, be sure of the correct orientation.
Be careful to select the correct strip-stock (8 very similar sizes) for each step.
Install the hinges and glue them from the inside before covering.
Sand the laser cut burn edges to minimize "show-through" after covering.
The wingtips can warp when covered; reheat to straighten.
Assembling the landing gear is a challenge, go slow, check alignment as you go.
Secure the cowling with clear tape instead of screws.
Build a cockpit hatch of balsa sheet, hinge with tape, latch with a magnet, tape canopy on top.

Power is from a 22X12-900Kv motor, 3S-950mAh battery and 9X4.5" prop. This produces about 150 watts of power and 24oz of static thrust with 6 minutes of flight time. The published flying weight of 17oz is optimistic. But at 21oz, mine flies great. It takes off and climbs out with a roll at ⅔ throttle and cruises comfortably with throttle. With a semi-symetrical, lifting airfoil and mild dyhedral, it is a smooth, steady and very stable flyer. Combining big loops, rolls, and spins into graceful sequences is a joy.

Full throttle vertical climbs are strong with a fresh 3S-950mAh battery. High control rates produce crisp aerobatics. With a slightly rearward C-G, snap roll, spins and inverted maneuvers are very impressive. It responds well at low speed and has a smooth, straight-ahead stall. Recover by adding power then pull the nose up. The stall speed is low enough to make landings smooth if you approach with very little power, keep the nose and wings level, then cut power and flare carefully. Be quick with the rudder as the tail settles.

This plane is a bit more rugged than other Stevens high performance ultra-light kits. It fits in a small car without taking the wings off and takes very little support equipment. It can be flown from a smallish (baseball-size) field with as little as 30 feet of smooth surface. It's a very convenient plane to have.

This build:
Span: 35"
Length: 30.5
Wing area: 250 in
Flying weight: 20 oz
Wing Loading: 11.5 oz/ft
Motor: 22X12, (900KV) = 150 Watt
Prop: GP 9X4.5" = 24 oz static thrust
Power Loading: 120 W/lb
Servos: Generic 10 gr micro (Tactic TSX5)
Battery: NanoTech 3S-950 mAh, 25-50C
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Dec 20, 2019, 04:48 PM
Denny the "Finger"
D_Wright's Avatar
I was fortunate to see this the field the other day. Very nice!

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