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Old Nov 06, 2010, 12:48 PM
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Old Nov 06, 2010, 12:49 PM
Build it again, Sam!
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Old Nov 06, 2010, 01:16 PM
Build it again, Sam!
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Smooth and finished wings with ailerons
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Old Nov 06, 2010, 01:54 PM
built flown + crashed it
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Thank you, that will give me a few things to try out. Kept my first wing design fairly simple, rk40 foil through out, elliptical leading edge and a straight trailing edge with a kinked rear sweep towards the tip. Straight along the top surface at maximum thickness so just a little dihedral and no curved up tips to make a straight forward first wing mould to practice on. Will post up my results when I have made some progress.

Thanks again
Mark
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Old Nov 06, 2010, 02:06 PM
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Very nice layout & description Harpye. I would only add a few other points to consider:

1) On the imported airfoil coordinates, pay attention to the leading edge x,y coordinate points because it varies by author/method. In some case, the LE may not be defined by an x,y intercept point at exactly 0,0. There could be datapoints on either side, high or low. So even though the curve is going through all the points, you have to make sure you are properly aligning to your chord datum. So in that case you may need to split the curve at the outermost tangency point. Why is this a condieration? Because if you (falsely) assumed one of the proximity LE points was actually the chord datum (meaning 0,0) & aligned your airfoil curve to your chord datum as such, it would actually make your airfoil at some undesirable angle of attack.

1a) And the same goes for the trailingedge. It could be a 100,0 type point, or it could be a defined thickness. You may have to massage or manipulate the curve & points to get the desired results you want prior to surfacing. There are pros & cons to either - another subject.

2) I would also endeavour to add more rib sections down the span of the panel & encompass them as part of the surfacing command. If its the same airfoil down the panel, just use the 'scale 2D' command & plop some more reduced copies down the span. If you are blending airfoils outboard like root foil A to mid foil B to tip foil C, you need to do this operation anyway. Why more control foils vs a single root section? Because if you have funky, curvy planform shapes, the surfacing command can distort the surface as it attempts to make 'its' best surface. Unfortunately, that may not yield the desired original airfoil section if you 'slice' the surface & compare it to original.
The surfacing kind of shows this with varying angles.
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Old Nov 06, 2010, 02:06 PM
Build it again, Sam!
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you can find point clouds sorted by app on Martin Hepperle Aerotools
Thanks for the hint with the different definition of the point cloud ... I mainly use the Hepperle source and so did not have this problem until now ... but good to know!

PTX using a multi foil wing your method using more than one section necessary, but using a single/ mono foil wing you would have to exactly position the foil splines between the LE and TE . -without doing this you may get a gull wing or a dove. Will Have to check this out, but you are right that the foil is always aligned orthogonally to the guidelines ( related to the reference / foil spline). So for to achieve a higly defined parabolic lift profile you certaily would better go with your multi foil strategy ( I'm not that much in gliders and normally dont use winglets or bent wings, but straight ones so you I want to thank for that push on this issue!)

Picture below would mean that the outboard region of the better defined foil (Root region of winglet)in my case would be 0.15mm higher ( 1%..2%) this area would definitely create more lift in the better defined version.. maybe this would be more important on more critical foils than my low Re MH33 but is definitely something to put an eye on.. thanks again

Hansjoerg
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Last edited by Harpye; Nov 06, 2010 at 02:54 PM.
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Old Nov 07, 2010, 11:44 PM
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Quote:
Originally Posted by Harpye View Post
.. but using a single/ mono foil wing you would have to exactly position the foil splines between the LE and TE...
Hansjoerg
Positioning scaled copies of the chosen root rib along the varying chord length panel outboard is easy & quick:
- in the wing planform, just draw some construction 'rib' lines connecting the LE & TE (in the direction of airflow) along the panel
- select your airfoil curve & then the orient 2-point command (example point-1 = LE, point-2 = TE)
- then select the corresponding destination: point-1 = LE intercept on plan, point-2 = TE intercept on plan. Done! This makes a 2D reduced scale copy of the airfoil at the outboard panel & it is in the same orientation as the normal airflow.
- just repeat this for as many ribs as you like (it takes longer to type )
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Old Nov 07, 2010, 11:58 PM
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Quote:
Originally Posted by Harpye View Post
So for to achieve a higly defined parabolic lift profile you certaily would better go with your multi foil strategy ( I'm not that much in gliders and normally dont use winglets or bent wings, but straight ones so you I want to thank for that push on this issue!)
Hansjoerg
If your wing only uilizes a single root airfoil & 2-rail type surfacing command, Im not sure you could predict the distortion of the resulting rib section shape in the outboard panel. I suspect it would change based how the planform shape influences the surfacing -the more tapered & curvy, the more unpredictable the results. The bottom line is: even if you wanted the same MH33 section down the (varying chord) wing panel, why not force the surfacing comand to 'use' this profile by introducing a few more exact scaled copes down the panel & just include them in the same sweep 2-rail command?

Here is an example, maybe its representatitve?
- black = wing panel outline
- red = root section, its a perfect circle (horrible airfoil!)
- blue = 2-rail surfacing, rail1=LE, rail2=TE, also include outermost tangent point at tip so it closes nicely. Also notice top view where the iso-contours are leaning over at an angle deviating from the red root section 'airflow' orientation
- green = section slice the wing surface in a normal direction rib orientation
- purple, compare the section to a perfect circle. They are different!
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Last edited by ptxman; Nov 09, 2010 at 01:28 PM.
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Old Nov 08, 2010, 12:35 AM
Build it again, Sam!
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You are right - that is what I also feel ... I just had no necessity on bent up wings and for straight ones there is not really a problem if you would leave LE and TE at same length and model the wingtip section separately.... ..... only problem is, that you would probably have to go with a mesh from curves strategy not to get the overswinging extrusion of a multipline loft ...
in the picture I posted the front shows the auto aligned rib spline which is getting undefined in the bent up region - and the wing in behind shows the multi spline definition which is not ... just for comparison!

Hansjoerg
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Old Nov 08, 2010, 09:56 AM
built flown + crashed it
Pewsey, Great Britain (UK)
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Quote:
Originally Posted by ptxman View Post
Positioning scaled copies of the chosen root rib along the varying chord length panel outboard is easy & quick:
- in the wing planform, just draw some construction 'rib' lines connecting the LE & TE (in the direction of airflow) along the panel
- select your airfoil curve & then the orient 2-point command (example point-1 = LE, point-2 = TE)
- then select the corresponding destination: point-1 = LE intercept on plan, point-2 = TE intercept on plan. Done! This makes a 2D reduced scale copy of the airfoil at the outboard panel & it is in the same orientation as the normal airflow.
- just repeat this for as many ribs as you like (it takes longer to type )
Wish I read this a day or so ago, as struggled for a while with this very thing, but worked out to use construction lines in the end and my wings are now starting to look better. It also seemed like a good idea to split the wing profile in half through the 0,0 points so I could use end point snaps to locate the profiles onto the construction line / wing profile intersections easier. Am learning lots of useful stuff from this thread so thanks to you all and keep the tips coming. After some more wing drawing practice I am sure to have some questions on turning the wing into a positive mould also.

Mark
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Old Nov 12, 2010, 09:58 AM
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Svizzera, TI, Bellinzona
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Hello !

I've drawn a wing and cutted out an aileron.

Can someone explain me how i can cap the hole created by the split function ? (selected in yellow on the picture) i've tried with "cap planar holes", "patch", "net of curves"...
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Old Nov 12, 2010, 10:06 AM
Claus at Area 52
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have you tried the simple loft function.??
you might need to make the lines "open" at the corners. with the split function.
Claus
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Old Nov 12, 2010, 11:30 AM
Build it again, Sam!
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Dave loft is one possibility but requires separate edges ... what you also can do is to trim cut the aileron by a extruded polyline / surface and afterwards trim the extrusion with the aileron ... double this object ( strg +C / Strg+V) and unify each of the newly created objects with wing or aileron object...
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Old Nov 12, 2010, 11:32 AM
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Old Nov 12, 2010, 11:43 AM
Build it again, Sam!
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same as I mentioned
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