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Author Topic: PZL Wilga for .5cc diesel  (Read 8448 times)
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Squirrelnet
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« Reply #200 on: May 24, 2019, 02:51:18 PM »

Quote
an absolute plumber's toolbag

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

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TimWescott
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« Reply #201 on: May 24, 2019, 03:41:13 PM »

...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!
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Squirrelnet
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« Reply #202 on: May 24, 2019, 05:00:50 PM »

Thanks Tim, I'll keep you posted
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OZPAF
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« Reply #203 on: May 24, 2019, 07:38:14 PM »

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

John
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DHnut
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« Reply #204 on: May 26, 2019, 12:35:34 AM »

 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
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Squirrelnet
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« Reply #205 on: May 26, 2019, 12:59:35 PM »

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
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ZK-AUD
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« Reply #206 on: May 26, 2019, 04:05:49 PM »

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
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Yak 52
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« Reply #207 on: May 26, 2019, 04:54:04 PM »

Very glad to hear it flew well Chris!  Smiley

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
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OZPAF
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« Reply #208 on: May 26, 2019, 06:55:48 PM »

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
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DHnut
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« Reply #209 on: May 26, 2019, 07:35:00 PM »

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     
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Squirrelnet
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« Reply #210 on: May 28, 2019, 04:03:50 PM »

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   Wink

Jon - That's good to know next step is a bit more tailweight
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TimWescott
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« Reply #211 on: May 28, 2019, 04:18:33 PM »

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...
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Squirrelnet
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« Reply #212 on: July 21, 2019, 12:59:50 PM »

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  Undecided

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 ??....
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DHnut
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« Reply #213 on: July 21, 2019, 04:05:19 PM »

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 
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« Reply #214 on: July 21, 2019, 06:37:30 PM »

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

John
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3view
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« Reply #215 on: July 22, 2019, 07:07:07 AM »

There's no replacement for displacement Smiley
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« Reply #216 on: October 03, 2019, 02:08:19 PM »

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
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griffin10010
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« Reply #217 on: October 03, 2019, 02:47:53 PM »

Hello. Been reading the comments for the Wilga. The plan is mine, P Hayward. Nice to see it is still being made. This was probably my most successful model ever. I had no issues with the slats, trimming or flying. Indeed on one enthusiastic hand launch the port wing swivelled on its mounting wires resulting in anhedral on the port wing, I thought that would be the end but all the Wilga did was fly in right hand circles.no heavy landing at all. I never did any repairs to this model, it never crashed. I flew it do death. On the comment it Flew Like a Brick until the slats were covered
would suggest the flying problem lies elsewhere. I always thought Aeromodellers description, Ideal first scale model a bit ambitious considering
the fuselage construction. I built a free flight Dornier 28, twin Mills .75. if anyone is interested I could dig out some photos and do a write up on it, it only flew once though.
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Squirrelnet
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« Reply #218 on: October 03, 2019, 03:16:09 PM »

Thanks for posting P Hayward, very pleased to hear from the designer of the model

It's a lovely design and a great little model. I really enjoyed building it, though as you say the fuselage construction is not really suitable as a first model. It does fly very well under power but I'm struggling to get any sort of glide out of it as you have read.  Mine is a bit on the portly side though which is not helping - its around 14ozs from memory with not a lot of wing area to hold it up.. I would be very interested if you can remember the weight of your model...a lot less I'm guessing.

Did I read in the AM article that your first one run was over by a van at the Nats !!!

 I would be very interested to learn more about your twin Mills .75 engined Dornier as I'm sure would many members on here, photos would be great.

Chris
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billdennis747
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« Reply #219 on: October 03, 2019, 03:58:19 PM »

I built a free flight Dornier 28, twin Mills .75. if anyone is interested I could dig out some photos and do a write up on it, it only flew once though.

Yes please!
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griffin10010
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« Reply #220 on: October 04, 2019, 05:45:20 AM »

Yes. The first Wilga met its demise being run over by a van at the Nats, attempting its first flight, a R.O.G. smashed to pieces, salvaged the engine though.
The second I built in time for Old Warden. 6 weeks? Aeromodeller were originally to include it as a free plan then decided to do it as an article. I never weighed my planes, didn't have any scales. A guy came round from AM, draughtsman, and took my original plans, drawn on lining paper and these were reproduced for AM. When I did the model I never gave a thought to the slats or lifting tail plane, I just scaled up from the AM article. I can't understand the poor glide mentioned, I don't ever remember repairing the Wilga, I used to tend to throw the models away if they got damaged and the glide was fine. I can't understand the comment, flew like a brick till the slats were covered over. Very unusual looking plane though, very pretty I always thought, I had never seen one made before. Peter.
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Squirrelnet
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« Reply #221 on: October 04, 2019, 03:56:09 PM »

I admired the design in my youth but never got any further than looking at picture in the Aeromodeller Plans Handbook, it's only after returning to the hobby that I decided to actually build one. I was hoping to try it out again at the Selby Trophy this weekend but sadly the weather has put paid to that one.

 There must something I'm doing wrong, I did notice looking back at the original article that the slot gaps on your model look quite tight. Mine however look somewhat larger. Maybe that is having an effect ( see pics )

Are you still active in the hobby Peter ?
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griffin10010
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« Reply #222 on: October 05, 2019, 09:04:24 AM »

Hello. I see what you mean regarding the flap gaps, you might only be getting lift from the main wing, considerable difference in wing area, plus the gap may be interfering with the airflow and producing drag. Might be worth closing the gap and trying. It might also explain the apparent lack of engine power as well. Not sure if you are aware, there is a photo of me on the net holding the plane in plan view and there is definately no gap
along with a more comprehensive write up on trimming along with the comment that some models, scale and otherwise simply refused to fly!
I think the photo would have been Old Warden 1970.
The sink rate of your very pretty Wilga on the glide is alarming, there is very little suggestion of a glide at all, this was not my experience
so something is amiss. I am 75 now and no longer building models, we came to Spain 12 years ago, bought about a dozen R.C. models and gear with me thinking I would fly regularly, great weather, only to find the local flying sites had been lost, not that much difference to the U.K. f you haven't seen the photo let me know and I will tell you how to find it. Peter.
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Squirrelnet
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« Reply #223 on: October 05, 2019, 12:52:49 PM »

Quote
Not sure if you are aware, there is a photo of me on the net holding the plane in plan view and there is definately no gap
along with a more comprehensive write up on trimming along with the comment that some models, scale and otherwise simply refused to fly!
I think the photo would have been Old Warden 1970.

 Thanks for that Peter. I did google search with various permutations but I can't find the picture. I think you may be onto something with the slot gaps though,I will have a look at that.

I look forward to hearing about your Dornier 28 if you get a chance

Chris

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« Reply #224 on: October 05, 2019, 01:08:43 PM »

Check if an exit slot of the slots is smaller (thinner) than the entrance one. If it's opposite slots will produce a lot of turbulence and drag.
Living in Poland I'm quite familiar with Wilgas (I flew her mamy times). In real it is not a glider at all. The sink rate of any Wilga is high because she was designed for a tow plane, so fast descent enables quick return to the airfield for another glider.
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