Polikarpov U-2 / Po-2 test flights.

by alibopo | November 10, 2014 | (3) Posted in Projects

Polikarpov U-2/Po-2

UPDATE 16/01/2015 - Here's a link to the plans; Polikarpov Po-2/U-2

UPDATE 28/03/2015 - I've been collecting and updating all my articles, planes and plans on my own website on this page; RCplanes It's still a work in progress, but there's a few extras and beta-stage projects that don't appear here yet.

We've had some very good weather around Edinburgh (Scotland) over the last few days. Perfect flying weather, so here's a quick video of the test flights and fine tuning following the Po-2's maiden. This is a tremendous plane to fly, with great presence in the air.

COMMENTS

raydar on November 10, 2014

Alibopo, do you think changing (specifically, decreasing) the wings angle of incidence would accomplish the same thing as increasing the down thrust? I suspect a much smaller change in wing incidence would be more effective. Beautiful build, by the way!
Log In to reply

alibopo on November 11, 2014

Hi raydar, swings and roundabouts I think. (And probably worth trying both. I did actually slip a tongue depressor spacer under the back of the top wing at one point to see what difference that made during the maiden.) Here's my take on it. Reducing the angle of incidence will reduce the 'Newtonian' lift, requiring the plane to fly slightly faster to stay in the air. Most of these 'slower' flying planes have quite larger angles of incidence - push them too fast and they start 'porpoising'. I think that was the problem a lot of folks had/have with the FT Old Fogey - they were/are trying to go too fast. The Polikarpov has a fairly large angle of incidence (relatively speaking) of 2.5 degrees, but it's not outrageous, and nothing like the 7-10 degrees you see on real old early-era planes. Reducing the A of I would require the plane to fly a little faster, which might 'spoil' the plane for me, I quite like its slow-speed 'treacle-in-the-air' performance, especially considering how heavy it is - I need something to keep it in the air! I had very little down/right thrust on my motor, so it was worth trying that first. After a little more research I saw one model design that suggested 3 degrees down and right. I've maybe 'overcooked' the downthrust very slightly, the plane actually starts to rise a little as I slow down from speed, but settles quickly. If I'd only changed the A of I, I might have ended up with a plane that flew faster, but still had the bat habit of nosing up under power. I do have a science/engineering background, but I've only been at this model flying lark for coming on two years, and I am getting better at understanding some of the empirical 'science' behind keeping the planes in the air, but I also still rely on what wisdom I can gather from other sources. Any insights are valued, thanks.
Log In to reply

jrvalentin62 on November 10, 2014

Downloaded the plans this weekend. Going under the knife this week. I'm making it as a Xmas gift. Excellent detail work. Edinburgh is beautiful (I was at RAF Edzell back in the 80's.) Thanks again for the share. Clear Skies, Calm Winds. Cheers!
Log In to reply

alibopo on November 11, 2014

Good luck with the build, it's a lovely plane to fly.
Log In to reply

alibopo on November 27, 2014

Hi, you'll maybe curse me, but I've just updated the plans and adjusted all the slots and cut-outs for a more 'common' 5mm thick foam board.
Log In to reply

Sidlaw Soarer on November 14, 2014

Hi Alistair, Your model looks great in the air especially when slowed up a little. Well done. Where do you fly from? I learned to fly models at Macmerry but flew for many years with the Penicuik club before I moved north of the River Tay.
Log In to reply

alibopo on November 14, 2014

Hi - I fly down at Musselburgh lagoons. There's a nice big field there, well away from foot traffic ...and no problem with noise issues, as these are all electric. If you're more into the flying than the precision modelling side, working in foam board is a real winner. Cheers.
Log In to reply

You need to log-in to comment on articles.

alibopo

(79)

Polikarpov U-2 / Po-2 test flights.