Pusher cowling ideas

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Eugene

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Never really had a problem of doing things. Finding correct recipe and talking to correct people was very difficult on this project. Once you have a direction, at least approximately, you can start working on it. I was talking nonsense for number of years and didn't know what to do. Now it is actually turning into a very cool project!!!
 

BJC

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I’m certain that you will enjoy it. I’m also certain that it will take lots of time go get it just the way that you want. That is not a comment on your skills, just a comment about how much time it takes to get a form “just right” if you haven’t already done several.


BJC
 

Eugene

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I’m certain that you will enjoy it. I’m also certain that it will take lots of time go get it just the way that you want. That is not a comment on your skills, just a comment about how much time it takes to get a form “just right” if you haven’t already done several.


BJC
I understand. I am only 53. I hope to see this project completed during my lifetime yet. It should take less than 10 years. I hope. In my next life I will be so much smarter and so much faster!
 
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AdrianS

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I understand. I am only 53. I hope to see this project completed during my lifetime yet. It should take less than 10 years. I hope. In my next life I will be so much smarter and so much faster!
I plan on coming back as a bird in my next life.
Or maybe a bat, so I get built-in sonar.
 

Eugene

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This is looking really great, Eugene. You might consider making the fillet on the top side as an expanding radius (as it appears you have done on the bottom). As a way to finish off the fillets at the back (where we see a little pink foam), you could consider an extension that completes itself something like this:
View attachment 116390
View attachment 116391
I received another recommendation from Russia today. I was told that any bumps or dips should be in line with airflow. Spot that needed improvement marked with dark lines. I am not sure if I could've done it different, but I will take a look next time.

tempImagelD.jpgtempImag.jpgtempImagesnV.jpg
 

Voidhawk9

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The flow there may be more downward than you have indicated - downwash off the wing? May not require change, but a smoothing of the 'bump' may reduce the chance of separation there if the flow is crossing.
 

AdrianS

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I don't know if it needs to be 'pinched in' as much as it is where the round prop spinner base meets the lower rectangular area below.
About where that top black line is - I think it could be filled in a bit.

Either way, we're talking about the last few percent of improvement - I reckon what you've got already will make a huge difference.


Mad thought - can you get a big fan in front or behind and do some tuft testing?
 

henryk

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OK, correct spinner for pusher from what I see has high and low pressure zones. Why do we need to do that? Why couldn’t we just simply make nice tapered cone and stay below 7° to avoid separation?

View attachment 115252
=some numbers ? (pressure) .

 

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Vigilant1

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Additional reference material:

View attachment 116508
Maybe Eugene should apply more graphics and gingerbread? 😉
It seems, with regard to the area between the spinner and the top of the wing, that the aerodynamicists largely throw in the towel and cry out: "That's the best we can practically do, and it's much better than it was."
I think we all get to that point on most projects.
 

Eugene

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"That's the best we can practically do, and it's much better than it was."
I agree! I realize sometime ago that my airplane with this kind of configuration will never win any speed trophies. Every airplane is list of compromises. My list is simply very long. This is price for helicopter like visibility and smell of fresh air in the cockpit (vs fuel or CO). But smart people tell me that I should be able to create good flying aircraft. Yes, slow maybe, but pleasant to fly.

That is precisely why I am trying to do as best as I can in those areas that I can do something about. But I do understand my limitations and practicality. But there is always voice inside of me keep repeating - "if you do it anyway, might as well do it right". But I get it, if you start splitting 1% of improvement, at some point you have to say "it's good enough".

And don't worry, I will find pretty colors to paint my creation when it's all done
 

Eugene

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After looking at my sketch in the living room for several days my wife made a comment that she doesn't like my new tail boom sticking up high at such aggressive angle. My quick, confident and educated response was: "This round tail boom will be working inside of propeller discharge at 19° angle. Cross-section of 8 inch tube at this angle will become approximately 26 inch long and aerodynamically very beautiful with very low drag!!!"

She was very impressed, but now I need you guys to tell me if I am correct on this.

tempImagekj1arX.pngtempImageQVirgz.png
 

wsimpso1

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You are correct that at that angle, even a circular section is pretty good.

It would be even better as an ellipse no wider than needed for the loads from the vertical tail and no deeper than needed for the horizontal tail loads. It would naturally start rather small at the tails, and grow as it goes forward. Keeping its minor and major diameters minimized along its length would make it even lower drag.

Billski
 

WINGITIS

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Yours is a 3.25:1 ellipse, so a little worse than the 4:1 ellipse listed here at 0.35 CD, the ellipse ACTUALLY shown there is about the same ratio as yours...

CD SHAPES.jpg
 
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mcrae0104

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I wonder what "BASED ON THE FRONTAL AREA" means?
Coeffiecient of drag is a coefficient--a ratio--the denominator of which can be based on any measure desired (e.g. frontal area, planform area, total wetted area, etc.). I, for one, always believe everything I see on the Internet, so I believe that an elliptical shape has less drag than a streamlined body, because the Internet told me so.
 

AdrianS

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Coeffiecient of drag is a coefficient--a ratio--the denominator of which can be based on any measure desired (e.g. frontal area, planform area, total wetted area, etc.). I, for one, always believe everything I see on the Internet, so I believe that an elliptical shape has less drag than a streamlined body, because the Internet told me so.
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