Raving about the RV4

At around 8:30am this morning I maidened my RV4 - the culmination of many (elapsed) weeks of effort. The wind was very light (2 knots or so), the sun was shinning brightly - maybe a bit too brightly, but I would just have to keep the plane out of the sun. She was ready to roll, I'd had the controls checked by another flyer, CoG was set, the taxi test on the grass had worked just fine. There was no time like the present...

Specs on My RV4




Controls: 4 Channels (I've mixed in 5 to allow Flaperon setup with those big wide airlerons)
Battery: Model Engines 3s 1500mAh LiPo
Power Plant: Towerpro BM2408-21 13A 1750kv Brushless Motor and TowerPro Mag 8 18A Brushless ESC.
Prop: 9047 I tested with (because I couldn't get the recommended 8x4 or 9x4 at short notice).
Receiver: JR RS77S
Servos: Hitec HS55 throughout (2 x airlerons, rudder, elevator).
Takeoff Weight: 544g including battery pack (402g without pack).



About the RV4

The RV4 is a balsa StevensAero kit that I purchased from Nitrodude (http://www.nitrodude.com.au). It is a scale replica of the real RV4 Kit Plane from Van's Aircraft (more info here http://www.vansaircraft.com/public/rv-4int.htm) which amongst other things was the first kit plane to be flown around the world by Australian Jon Johansen in 1995 (more info here http://www.vansaircraft.com/public/jj-persn.htm).

Building It

If you want to build a balsa kit these SA kits are simply amazing. They almost snap together and they self jig - this is the first balsa model I had ever built, and it built straight without me 1. knowing what I was doing, 2. worrying about whether or not I was building it straight.

There were a few mishaps along the way. For example, I put the airlerons together the wrong way round first time because I was so tired (which some careful cutting and regluing fixed), and I snapped a rib of the fuse twice (which straightening, hardening with CA and reinforcing with another bit of balsa fixed) due to heavy handling, but for the most part it was hard to go wrong.

Covering the model was another challenging thing to learn. Fortunately the photo resolution for pictures on the web wont let you see the ugliest parts, but this shouldn't make much difference to how she flys.

The model has two motor mount options, allowing you to fly her on a GWS350 geared setup, or install a brushless straight away. I went brushless straight away with a little TowerPro 2808-21 (my first brushless engine). I was unable to get the best props on short notice, so ended up using a GWS 9047. I was worried this might draw too much current, but some time on the desk with the new CLAMP meter showed she wasn't going to bust 13A (although she was at max throttle at around 75% of throw of the throttle stick.

Once assembled, pushing the flight battery, a 3s 1500mAh as far forward in the compartment left her perfectly balanced (for the maiden) a fraction forward of the main wing spar.

The day before the maiden I took her back down to Nitrodude for a final control and control throw check. After discussion we dialled back the throws another 30% (good call - thanks Paul), and I halved the flap deflection.

All the preflights were done - CoG well set, control checks done. Flaps on. I tried a test taxi on the grass at Curtin - all good. Look around the field, check the wind, deep breath then... advance the throttle.

The Maiden

With about 1/3 throttle she quickly built up speed and was airborne a few moments later. Putting throttle up to about a half I used some more elevator to get her to put on some altitude. At about 10 metres I had to turn her due to configuration of the park. Nice gentle roll rates thanks to backing off the throws. Fumbled round for the flap switch - flaps up - model looking steady.

Very slightly rolling to the right - dialed in 1 click left airleron - steady now. Slightly nosing down - 1..., 2... clicks up elevator and flying well..., in fact flying brilliantly. She was reacting absolutely perfectly to every instruction I was giving her.

Sailed her up and down the field and put her into high banked turns - she was inspiring confidence. Not wanting to get ahead of myself there are a number of things I wasn't going to do on the maiden - use high rates, or do any kind of aerobatics. Two things I was going to try were WOT (I was still flying her easily at 1/3 throttle), and vertical performance. I pushed to WOT, planning to leave it there for only 5 seconds or so - the extra thrust bumped the planes speed up, but very quickly I could tell the prop was not right for high speed (although she was still making pretty good pace). Brought her back to about 1/3-1/2 throttle, gave her WOT and pulled her nose up. Up she went to vertical. Hoping for her to keep on climbing I watched as she hung in the air - me using the controls to keep the nose straight up. She hung there for about 5 seconds before finally stalling away to a nice easy recovery.

I'd only been flying about 5 minutes tops, but I wanted to bring her in long before I had any battery issues. Eased the throttle back, check wind, work out approach, flaps on. She got a slightly nose down attitude with flaps on, brought her round and brought her in at about 1/4 throttle. Approach was no good, running too long, had too much airspeed at the bottom of the dive. Power on and pull away, and round we go.

Realised also that the wind had changed direction (although still very slight), flew to setup a new approach. Throttle down dive - too long again - probably plenty of room, but I want to be close enough to see contact point, and I want *plenty* of room. Call that one a practice, power on, round we go.

Next approach, much better, looks good, plane down from altitude much sooner - still running longer than planned, but there is the aforementioned *plenty* of room still available. Realise this is the one - flare, good contact, no nose over. Close throttle. Collapse.

Before starting the flight I had joked with my better half about whether my maiden flight perfect landing blessing would continue (The last four planes I've maidened, including the RV4, I have had perfect landings - planes that I later badly damaged due to poor landings such as my Tigermoth 400). Well it held - I was ready to live with a nose over landing and no damage, but in the end the landing was much better than that. Down safely for a perfect landing. Woohoo.

Closing Thoughts

Balsa does fly best. Well, and having enough power makes a plane fly properly also, but I couldn't believe how direct the RV4 was - it just went exactly where I wanted it too. I'm looking forward to getting it back out to the park.