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Very low aspect ratio planes?

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berridos

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madrid
For the firewall i will use a ceramic polymer that resists up to 1200 degrees celsius (ceramic matrix with basalt fiber cloth), but between that sheet and the composite structure there should be some insulating distance keeper.
 

Sockmonkey

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Apr 24, 2014
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Flint, Mi, USA
The remark about trying to keep all tubes similar. Yes, but ... hey ... we live in the modern world. Let all the tubes be cut by waterjet-cutter. Using hunderd different tubes is no longer a trouble. Just get them labelled. ;)
Sure but not everyone has access to one. A couple dozen 90 and 45 degree cuts is easy for anyone. Build a little jig and you're done in half an hour. I'd probably use square tubing too, just to make it easier.
 

Arfang

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Aug 10, 2014
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Switzerland
@Norman

I tried using XFLR5 today, the learning curve is quite steep.

If you don't mind, I would like to ask you a few questions:

When I try to open a .dat file I created, it says thickness 0% and the program is unable to run an anlysis, something about points being unconverged.

The .dat file contains the following

doublewedge02

0.0 0.0
0.5 0.1
1.0 0.0

1.0 0.0
0.5 -0.1
0.0 0.0

I tried to put the X coordinates in a different order:

0.0 0.0
0.5 0.1
1.0 0.0

0.0 0.0
0.5 -0.1
1.0 0.0

But no results.

When trying a known airfoil and comparing the results with airfoiltools.com data, there's no error message but the curves are not the same at all, I suppose it's due to incorrect settings?

Is there a way to import a .step/.iges/... file in XFLR5 to perform a plane analysis? Since the aircraft type I have in mind has no separate wing or fuselage and airfoils are actually slices of the aircraft volume.
 

Voidhawk9

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Mar 26, 2012
Messages
372
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Timaru, NZ
@Norman

I tried using XFLR5 today, the learning curve is quite steep.

I tried to put the X coordinates in a different order:
Yes it's a steep curve, it's not just you!
You are on the right track, though. Coordinates need to be like:
1.0 0.0
0.5 -0.1
0.0 0.0
0.0 0.0
0.5 0.1
1.0 0.0
 

Norman

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Grand Junction, Colorado
XFLR5 only reads one format correctly. Airfoiltools.com offers a couple of formats. IIRC you want the Selig format not the Lednicer format. If you try to load the wrong format it'll usually just fail but sometimes weird stuff happens, like zero thickness or drawing it upside down.
If you open the file with Notepad or some other flat ASCII text editor (not a word processor) it will look like this:

Name of airfoil [only 1 line above the coordinates]
1 0_______________[start with 1 0]
0.9 +_____________[then describe the top surface]
0.7 +
0.5 +
0.3 +
0.2 +
0 0_______________[one zero at the leading edge]
0.1 -_____________[then describe the lower surface]
0.3 -
0.5 -
0.7 -
0.9 -
1 0______________[end at the trailing edge]

Separate the coordinates with a space, not a tab or some other invisible character. No blank lines (returns). If there is a blank line that is interpreted as the end of the file.
 

berridos

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madrid
I would really like to research this position. Any software that allows to insert manikins? The solidwork human stuff module costs a lot.
82777566_10212303162934564_2675336971219369984_o.jpg
 

nestofdragons

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Jun 8, 2016
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Location
Near Antwerp, Belgium
I would really like to research this position. Any software that allows to insert manikins? The solidwork human stuff module costs a lot.
View attachment 103287
My word of advise: do not draw. Build mock-up and test yourself before drawing. I did a few tests in the past and i was surprised that some things i thought to be good were in fact very very bad.
You can read about the tests here: My own prone tests - Nest of Dragons
I took the Horten HXb as source of inspiration.
My best result was this:
2020-10-21 test prone.jpg
I could hold this position several hours if needed.
The secret of the good comfort of the "seat" was shoulder support. My chin was even free. No support there. And that takes a lot of uneasy feeling away.
 

Arfang

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Messages
117
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Switzerland
Yes it's a steep curve, it's not just you!
You are on the right track, though. Coordinates need to be like:
1.0 0.0
0.5 -0.1
0.0 0.0
0.0 0.0
0.5 0.1
1.0 0.0
It solved the thickness problem, the points are still unconverged but the thickness and max thickness position values are now correctly displayed. Thank you.

Name of airfoil [only 1 line above the coordinates]
1 0_______________[start with 1 0]
0.9 +_____________[then describe the top surface]
0.7 +
0.5 +
0.3 +
0.2 +
0 0_______________[one zero at the leading edge]
0.1 -_____________[then describe the lower surface]
0.3 -
0.5 -
0.7 -
0.9 -
1 0______________[end at the trailing edge]

Separate the coordinates with a space, not a tab or some other invisible character. No blank lines (returns). If there is a blank line that is interpreted as the end of the file.
Thank you but I don't understand, usually there's a X coordinatate and a Y coordinate, here you start with X1;Y0 followed by X0.9+ is + supposed to be the Y value or do we have to put a + sign before positive values?

Any way to import 2D curves from a CAD program instead of typing?
 

berridos

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Location
madrid
One nice thing is that in this position, in a delta, the tail wheel can be retracted with the feet and the frontwheeel pretty much by hand and stowed).
 

Norman

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Messages
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Location
Grand Junction, Colorado
Thank you but I don't understand, usually there's a X coordinatate and a Y coordinate, here you start with X1;Y0 followed by X0.9+ is + supposed to be the Y value or do we have to put a + sign before positive values?

Positive numbers on top and negative numbers on the bottom.

Any way to import 2D curves from a CAD program instead of typing?
See if you can get geometrical information about objects. There may be a command like <info> on the tools menu. Copy the spline info and paste it into a text editor. Then use search and replace to remove everything except the the cooridinates.
 

cluttonfred

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Fort Walton Beach, Florida, USA
Norman and all, I don't think I ever did get an answer regarding a rule of thumb or rough approximation of the max CL to expect with a LAR design, say an aspect ratio of 1.0-2.0 which would cover circular, square and diamond (rhomboidal) designs?
HBA concept sketches (11).jpg
 

Riggerrob

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Sep 9, 2014
Messages
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Location
Canada
Dear berridos,
I only found three human factors suppliers for Solidworks.

CAD human packages range from $349 to $449 for designing cockpits around adults.

ergo-link's basic package starts at $449 for an SAE 5th to 95 th percentile human figures, based upon Natick Labs data. They also offer packages for industrial and military manikins.

Zygote goes into a ridiculous amount of internal anatomy and I did not find a price listed.
 
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Vigilant1

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Jan 24, 2011
Messages
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Location
US
Now I am confused. I thought one of the appeals of LAR was high lift at high AOA due to vortex effects. A CL of 1.0 is not terribly impressive.
From the PAV report (comparing the proposed Facetmobile follow-on to conventional aircraft) :

The conventional airplanes take off with the flaps retracted or at very small deflections, so their maximum lift coefficient is relatively low (about 1.35). Although the low aspect ratio airplane has a lower maximum lift coefficient (about 1.0) than either of the conventional airplanes, it is not enough lower to offset the effect of the low wing loading
Maybe the plane has a higher Clmax (Clmax max?) when it is in vortex lift at an exceedingly high AoA, but the drag at this AoA is so high that it could/would never be used for takeoff.
 
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