Barnstormer in Depron.

[Colin Leighfield]

Conflicting advice here chaps, it's doing my schizophrenia no good at all! It's dry here right now, but forecast is for rain tomorrow and probably Saturday, we'll see. Sometime between now and Sunday I'll try it again.

[Colin Leighfield]

Here it is, last shot. After yesterday's heavy rain, today has been nice but very windy. If I'm going to make Greenacres elaectric fly-in next weekend, it must fly satisfactorily this week, I'll do my best.

[Colin Leighfield]

At last, it flies! Here it is:- Not perfect yet though. Lateral control is good with differential on the ailerons and 40% coupled aileron and rudder. Stability is good in that sense. It looks a touch tail heavy though, even with more lead than I intended to get the cg to 25%mean chord and some packing under the trailing edge it still need 30%down on the elevator sub-trim. So, although it goes against the grain, there will be a bit more nose ballast yet and I will fix the reduction in the angle of attack. Basically though, it looks good and in spite of the heavier than intended weight, it shows no sign of being under-powered and the stalling sped is very low indeed. The undercarriage is too short though, even with a reasonably normal landing the nice wooden prop has caught and splintered. Might need to do something about that. However, I'm now pleased that I resisted the temptation to jump on it last week.

Edited By Colin Leighfield on 08/08/2014 18:26:14

[Martian]

Great stuff Colin

[john stones 1 - Moderator]

Very good Colin

What's your thoughts then, whats been the remedy ?

John

[Stephen Jones]

Well Done ,

I am pleased for you, and see perseverance pays off in the end

Well done twice

Steve .

[Tony Bennett]

well done colin

told you it would fly well.

[Colin Leighfield]

Thank you chaps, I'm amazed that you didn't give up on this one long ago! John, basically it's because it seems to need a cg far further forward than I expected. Initially I looked on this as being a variation on an old free-flight theme, with a fairly rearwards cg and a big tailplane damping out a lot of instability, intrinsically stable and fairly tame. The Baby Barnstormer plan that provided the starting point shows the cg at 30% mean chord and I thought that with the large tailplane and strong trimming capability of the elevator that any rearward cg problems would trim out easily. Because I was over enthusiast about keeping the weight down I was suffering from wishful thinking as far as a cg around one third of mean chord was concerned.

Even now at 25%chord it looks as though it could go slightly further forward. I think also that when I altered the wing attachment method from the hook and elastic band method on the Barnstormer plan to nylon bolts in a liteply platform that I might have unintentionally increased the angle of incidence slightly.

This is all fine tuning though, it looks as if it's going to be the nice durable sport model that I originally hoped for. The biggest remaining change could be lengthening the undercarriage a bit. Not too big a problem. I know enough now to do a better job of anorher one if I ever decide to do so!

[Colin Leighfield]

Tony thank you. It looks promising now and looks the part in the sky.

[Colin Leighfield]

In the shed at 06-30. Added another 70gms of Lead up front (gulp) and made a proper job of reducing the wing incidence with 6mm balsa on the wing platform. As a temporary expedient to improve ground clearance for the prop I swapped the 57mm wheels for a pair of 70mm that I had lying around. Also I bent the tail wheel wire back to increase the ground angle a bit more. Later I might lengthen the undercarriage by 25mm or so. Here it is with the splintered prop still on. I have to try and get replacement props (back to plastic) this morning to have any chance of getting a final test flight in today. If I can do that successfully at Fradley, I might then be able to get over to Greenacres for an hour or two, which would be great. It doesn't look as if the weather will be helpful tomorrow, otherwise that would have been much easier than trying to do it all today.

[Colin Leighfield]

After the last posting I got this to Greenacres on 10 August but it was pretty windy and I decided not to chance it. I showed it to Chris Bott though and I think he felt the 6mm lift on the trailing edge was a bit much. When I took it home I reduced it to 3mm. Later in the week I flew it again at Fradley.

Conclusions were that it doesn't like any cross-wind for take-off but get it straight into wind and it's fine. It's both very stable and responsive. Despite the forward cg and reduced incidence it was still asking for elevator down trim under power. However power off it was dropping its' nose, so the conclusion of all present was that it needed more down thrust. On the fourth flight it lost power about five minutes in and I had to land it. I was surprised to find that the 2837 1250kv motor had virtually seized and the aluminium rear mount had fractured. I don't understand this because the prop was balanced. However, here it is with a new motor from 4Max and washers under the top bolts to increase the down-thrust. Hopefully I will fly it again on Wednesday, in time for our electric fly-in at Fradley on Sunday.