PZL Wilga for .5cc diesel

[Squirrelnet]

an absolute plumber's toolbag

  That phrase is going stay with me for sometime !!! 

[TimWescott]

...I've added a gnat's more downthrust too in anticipation of an increased  angle of climb under power...

I would expect that after trimming for the further-back CG the thing will have less of a tendency  to go pitch-up under power -- here's my wish that if you're surprised, it's not a BAD surprise!

[Squirrelnet]

Thanks Tim, I'll keep you posted

[OZPAF]

Good luck with it Chris. Here's to good weather, sunshine and little to no wind! Asking a bit I imagine Good luck to all you fellows flying in the Nats.

John

[DHnut]

 Chris,
        Well done the Wilga looks very realistic with a good sit in the air. Just a thought, but the real aircraft will usually have a steep approach as all the slots and flaps are deployed with a lot of power on so you are not out of scale in flight terms. Even when clean I doubt if the real one has any sort of glide, probably like the average WW1 aircraft of about 1 in 3. 
Ricky

[Squirrelnet]

Thanks Ricky.

Despite its rather too STOL final approach I'm very happy with the Wilga, it looks great under power and well worth continuing with the slats and flaps. In the Flying Only Comp at the Nats I came a very happy 4th, which considering its death wish glide at Old Warden, I can only thanks you guys for the help particularly with the CG position.

It's currently 45% and think I will try a tad further back still, stability was very positive under power in the blustery conditions and I'm also thinking of more downthrust as my power speed my still be less than the gliding speed, which will always end in a bad transition.

My epoxy glassed undercarriage fairing failed again so before I attempt something more radical I'll try the same design with a 1/32" ply reinforcer and layer of epoxy glass over the top

[ZK-AUD]

Chris I've been lurking and quietly liking this build as it has progressed.    Those steep arrivals are a challenge but I was looking at this problem and wondered whether you could try going the other way and make the leg extremely rigid.  (liteply leg covers epoxied on and silk bound with a piece of carbon rod running through the middle parallel to the existing wire) Then articulate and spring / damp the trailing arm section as per the real one  - a clothespeg style spring would do it.

Here's a rough-as-guts sketch of how I would approach it.  Ideally the articulated section would be silver soldered to the brass tube but you'd get away with soft solder with a good fillet.  The step in the brass tube is your forward stop against the spring tension

[Yak 52]

Very glad to hear it flew well Chris! 

At 45% you have a static margin of 16%, still fairly forwards in general terms. 5-15% is normal, depending on the model, with FF scale models tending towards the high side. Considering the generous tail volume (what you have is more like a duration model) you could afford to go a bit further back still.

Jon

[OZPAF]

That's good news. I'm glad it performed well and as Jon mentions you still should be able to come back a little further. Mike's suggestion of an articulated, sprung trailing section to the UC leg is possibly a solution to your UC problems.

John

[DHnut]

Chris,
        Your use of the 1/32" ply reinforcement should work. I am building (slowly) a Broussard and have used a similar approach with two facing pieces of 1/32" ply and a core of 1/8" epoxied around the leg and a torsion bar in the fuselage. The reinforcement should allow the trailing section to give a bit as the leg will be significently stiffened. The video was great and the glide reminded me of watching an RAAF Caribou on approach at Amberly where the nose seemed to point at the ground. Great spectacle. The way it coped with what appeared to increasing wind was impressive, clearly the slats were working.
Ricky     

[Squirrelnet]

Nice design Mike thanks.

My first step is a 1/32" ply reinforcer in addition to the balsa fairing wrapped in epoxy glass from last time. Its very similar to Ricky's thoughts.  There is a little movement allowed in the wheel and axle thanks to the triangular section cutout in the centre of the fairing.( see pic in post 205) . The right hand leg has survived fine but in inside leg with a left hand 'glide' did not.

 If this one fails I'll try your idea Mike, as I'd already repaired it   

Jon - That's good to know next step is a bit more tailweight

[TimWescott]

I think you may find that more spring is required than the original had.  If I could figure it out, I'd recommend something that lets the LG collapse completely, then spring back.

But then, I fly control line because I'm not smart enough for free flight, so...

[Squirrelnet]

I think you're right Tim it needs more springing. If I was going to build another...I'm not.. I would use a torsion bar on the main former which I would beef up to 1/8' liteply to cope. I would forget the thinner gauge front supports on the plan, they are not even scale anyway.

I have had to make some changes to the Wilga though.

I tried some more trimming at the Eddie Riding event a few weeks back but I couldn't get enough power out of the .5cc Redfin to haul the model into a decent climb. I tried again at Old Warden last weekend but despite fresh fuel there's not enough power to produce a decent climb out.

I think after the initial burst of power from the freshly run in 030 Redfin, the edge has just gone off the engine and I can't quite squeeze enough out it. The cure is hopefully an easy one - I bought the 049 version from Alex Phin at Old Warden. This really is a big brother to the 030 and the hope is, it will be able to warble away quite nicely to carry the Wilga aloft.

The downside is it's a bit heavier ! what was the wing loading again... oh well let's not worry about that 

I fitted the original engine using metal plates attached to much wider spaced bearers than would be usual. This means a couple of hours work making new plates for the new engine and the 049 is installed.

The engine is a tighter fit in the engine bay but no major surgery was required and even the cowling still fits, though it will need hole in it now to clear the compression screw. I have substituted a hardened steel allen bolt as it gives a cleaner more scale like look than the supplied comp screw.

Pic 1 The Redfin TBR 049 compared to the Redfin TBR MK II 030

pic 2  Engine fitted with 3mm Aluminium plates

Pic 3 and Pic ... it fits !!!

The only 'downside' so far is now have a spare Redfin 030 TBR... Hmmm a reduced size John Watters Albatros CIII perhaps ??....

[DHnut]

The joy of using engine mounting plates. I am sure the extra power will be sufficient and a steeper climb will not be out of place as it is a STOL aeroplane. How much is the weight gain? Surely not too much. Lok forward to seeing it in August.
Ricky 

[OZPAF]

Good luck with the trimming Chris. Hopefully that should do the job.

John

[3view]

There's no replacement for displacement