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Author Topic: Show Your Newest Creation  (Read 96120 times)
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USch
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« Reply #925 on: July 25, 2016, 10:32:47 AM »

but the original idea was to add a "chin" on the underside near the leading edge to reduce drag.

Now you got me, Tony  Smiley
What means a "chin" Huh Even google translator fails on that  Sad

Urs
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PeeTee
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« Reply #926 on: July 25, 2016, 11:40:08 AM »

My chin is covered with whiskers Grin

Looking at LDA airfoils, I presume that it's a part of the airfoil that droops below a line between the centre of the LE and TE, close to the LE. I'll now wait for Tony to tell me I'm wrong Roll Eyes
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OZPAF
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« Reply #927 on: July 25, 2016, 08:09:11 PM »

Yes from I have read that's basically correct PT.

As I understand it -this particularly benefits aerofoil sections of moderate camber and low thickness percentage which would otherwise tend to be concave to a degree on the lower surface behind the LE - thus leading to early flow separation at angles of attack near zero and below.

By adding a "chin" to the lower surface - basically adding a convex section to replace the concave area, then separation on the lower surface is thus delayed to much lower angles of attack and thus allowing a fast climb at low angles of attack with low drag., and consequently more height.

John
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USch
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« Reply #928 on: July 27, 2016, 11:51:43 AM »

John and Peter, I was asking about the tailplane section. I extracted it below from Tony's drawing and put the center line on.  It has no undercamber and resembles more a symmetrical foil. It has already a lot of aerea below the center line.
So there must be another meaning in the "chin".

Urs
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FLYACE1946
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« Reply #929 on: July 27, 2016, 12:18:16 PM »

My latest build cover here with Brent's Connie is my Lockheed Starliner 1649 here on HPA Free Flight Scale.  Gotta get her into the air.
Sky9pilot
Do you have anything to report on your Connie flights? Hope so and the flights were as beautiful as the finished product.
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OZPAF
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« Reply #930 on: July 27, 2016, 08:23:15 PM »

Quote
John and Peter, I was asking about the tailplane section. I extracted it below from Tony's drawing and put the center line on.  It has no undercamber and resembles more a symmetrical foil. It has already a lot of aerea below the center line.
So there must be another meaning in the "chin".

Whoops! However the 'chin" I feel is still there Urs. It is what makes it appear to be close to a symmetrical airfoil. The thickness highpoint on this airfoil is quite a long way forward.
I'm not sure why separation on the lower surface would be an issue during the bunt launches it was originally designed for(as Tony mentions) however I'm sure there is a good reason.

John
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cman
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« Reply #931 on: August 08, 2016, 09:06:29 PM »

Here is my latest creation. It's the "Mojo" from plans I downloaded here.
I think it's a cool looking plane.  Covered it with silver paper and trimmed in colored tissue.
Got it out flying the other day and it flies real nice!

Chris
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OZPAF
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« Reply #932 on: August 08, 2016, 11:24:52 PM »

Neat. Is that a full size float in the background of the second pic?
John
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cman
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« Reply #933 on: August 09, 2016, 02:41:50 PM »

Close.
Those are snow ski's for my full scale 1946 Champ.
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billdennis747
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« Reply #934 on: August 13, 2016, 05:14:25 PM »

A Heath Super Parasol based on the Gene Thomas design. 37", DC Dart diesel. The structure was built by a late friend: I covered and painted it. A lot of masking tape involved. A few finishing touches needed but I suspect I shall have to build a bigger tailplane. My first YHWM.
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« Reply #935 on: August 13, 2016, 05:20:06 PM »

Cracking paint job Bill!  Grin

Andrew
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billdennis747
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« Reply #936 on: August 13, 2016, 05:23:06 PM »

Thanks Andrew - there's more to do!
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« Reply #937 on: August 13, 2016, 06:28:23 PM »

Not a colour scheme I have seen before ... looks great  Smiley
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OZPAF
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« Reply #938 on: August 14, 2016, 04:20:24 AM »

You've done your friend proud bill. Eye catching colour scheme.
john
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p40qmilj
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« Reply #939 on: September 15, 2016, 11:30:18 AM »

 Grin I  just finished PESCO SPECIAL which is starting to be have.  i am currently doing mustangs for a book i am writing hopefully to be published.  i also have a kids book under consideration.  we shall see i guess.  joining the mustang stable is a peanut profile and the GAR p 51 b . pics to follow

jim Roll Eyes Grin
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Prosper
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« Reply #940 on: September 21, 2016, 06:17:01 AM »

This is my Martin Baker MB5, built months ago but only recently put in flying condition. It's a rough (but dimensionally accurate) mockup. I meant to say on my Westland Whirlwind thread - but didn't - that I've nicked (stolen) this whole mockup idea from Rich Moore, who made a mockup Fokker Dr.I to test the viability of, and take some of the knocks for, his amazing Dr.I replica.

The MB5 model uses the torque-tube method of contra-rotation. Span is 21" (1/20 scale). The MB5's wings were short so for a 21" span model it's quite big. The wings have the RAF34 section and are made of EPS foam with balsa reinforcement, covered with pre-painted tissue. The tailplane likewise but this has a symmetrical section with 9% thickness-to-chord at the root. The fuselage and fin/rudder are 0.8mm (1/32") balsa sheet. All the flying surfaces have scale area and the wing dihedral is scale. Because of the meagre dihedral I've used pendulum ailerons. The propellers are scale diameter.

The model as shown weighs 60.8g, the airframe making up 37g and the powerplant 23.8g (including the noseweight in the spinner cap). That gives a wingloading of 0.097g/cm2 or 0.63g/in2. It's galling that it needs noseweight, but for pitch stability the CG has to be right forward - it's currently at 23% of the wingroot chord.

The video flight was lucky in that a flat evening calm coincided with a brief absence of cattle from the field (they were in a corner noshing their supplemental feed. They seem to prefer eating this than eating model aeroplanes). There were 840 turns on board and the flight used them nearly all: this gives an average RPM of about 2400. The contra-prop provides a lot of thrust, but boy it uses up turns fast. 840 turns is a bit over half the available turns of the installed motor (24" long loop of 7/32" rubber). Anyway, it now looks as if it might fly over 30 sec which is a tolerable flight time for the wingloading, and I hope to save some few grams on the fully-finished version.

Stephen.
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Pete Fardell
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« Reply #941 on: September 21, 2016, 07:23:25 AM »

That looks fantastic in the air- rock steady! Don't know how you do it.

(And please will you stop making 'rough mockups' that look so much better than my proper models!  Grin)
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dputt7
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« Reply #942 on: September 21, 2016, 07:48:47 AM »

Very impressive Stephen. great presence in the air, Kudos.
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Prosper
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« Reply #943 on: September 21, 2016, 08:31:56 AM »

Pete - the "rock steady" is not my doing - it's the wind's doing (or the absence of wind in this case Smiley ). Also, you're obviously not seeing the sticky tape holding the wing on, and the sticky tape wing fillets, the EPS canopy with paper patches on it etc. I asked the dog what he thought of it and he said "ruff".

Thanks Dave, hope your shoulder is mending! I'm now up to date on your 'Precious Metal' thread - very interesting reading, and very relevant to this little beast.

Stephen.
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USch
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« Reply #944 on: September 21, 2016, 10:09:03 AM »

Great flight, Stephen!

Urs
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OZPAF
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« Reply #945 on: September 21, 2016, 10:51:33 PM »

That's a pretty good flight Stephen - calm air or not. The combination of the contra rotating props and pendulum ailerons seems to be working well.
You also have a built in blast tube Smiley
Good to hear from you Dave - well on the mend I hope.
John
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DHnut
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« Reply #946 on: September 22, 2016, 12:24:37 AM »

Stephen,
            Looks great and it is interesting to see the ailerion positions. Tempts me to get the Mark Drela designed MB5 peanut out and move the CG to your setting. No contra prop though. It is definitely an outdoor model. I will check out the CG and start from scratch. The power when last tried was a loop of 1/8" about 1.5 times nose to peg length. The prop is a Tern Aero 6" and no ailerions.  All I need now is for the wind to stop. It is spring. The Magister is also waiting a calm morning as it now has more lead in the nose.
        Ricky
      
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Sky9pilot
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« Reply #947 on: September 22, 2016, 12:25:57 AM »

Prosper...very impressive MB-5!  I would like more info in the torque tube contra rotating prop setup please.  I have several models in mind that I would like to try this propulsion on!
Sky9pilot
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Sky9pilot
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« Reply #948 on: September 22, 2016, 01:15:25 AM »

Very nice Steven. And now I also see where you use your contra rotating tube discussed in the Hiller thread.
It seems to work now nicely. Flies like on rails Smiley

Looking forward to see the finished model.

Roman
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Prosper
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« Reply #949 on: September 22, 2016, 09:23:10 AM »

Thanks fellas. Roman, I remember now you asked me on your helicopter thread what the contra unit was for - and I never replied! Sorry about that. Ricky, this particular MB5 model seems to demand a well forward CG for acceptable pitch stability. The hz stabiliser is very big (nearly 26% of wing area) but it's on a very short arm. Also the contra-prop is probably much more destabilising than a single prop, and it's on a long nose. An MB5 model with a single prop may not require the CG so far forward - you might be able to save on uneccessary noseweight.

Tom, the idea is very simple but putting it into practice less so, and each installation will raise its own challenges. I guess the details of this system don't belong on this thread so I've opened a topic on the Outdoor General Discussion forum.

Stephen.
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