modelling an elevon

[Fabien R]

Hello,
I would need a parallelogram to model an elevon of this shape:

/ \
/ /
/__/

I used a rectangle with an angle in wing->sub but its LE and TE edges do not remain parallel.
Any hint ?
Is there any pointer about how to model an aileron with the GUI ?

--
Fabien

[Fabien R]

I meant a quadrangle.
--
Fabien

[Brandon Litherland]

I don't think the layout for your elevon was presented the way you meant.  Can you post an image, even just a camera picture of a paper drawing is fine.

[Rob McDonald]

If you want to use VSPAERO's capability to deflect the control surface, then you must use a 'control surface' type subsurface -- and it must be on a wing-type component.

The control surface parameterization should make sense for your needs.

Rob

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[Fabien R]

On 08/06/2022 17:48, Brandon Litherland wrote:
> I don't think the layout for your elevon was presented the way you meant.
> Can you post an image, even just a camera picture of a paper drawing is
> fine.

This is the right elevon.
Just for my curiosity, how should I have represented it ?
--
Fabien

[Fabien R]

On 08/06/2022 18:06, Rob McDonald wrote:
> If you want to use VSPAERO's capability to deflect the control surface,
> then you must use a 'control surface' type subsurface -- and it must be on
> a wing-type component.
>
> The control surface parameterization should make sense for your needs.

Thanks Rob,
This is exactly what I need.
The problem is that nothing happens when I click on Control surface->Add.
Sorry if my question seems dummy but on XFLR5, you have to create two airfoils with the TE up and down.
Tell me if I have to post on another newsgroup.
--
Fabien

[Brandon Litherland]

Fabien,

Sorry about the Control Surface bug.  I found and fixed it but that hasn't been pushed to 3.28 yet.  You should be able to get version 3.27 to add CS.

The trick out at the tip is that you're looking at a 5-sided polygon rather than a 'rectangle' per se.  However, in UW coordinates it doesn't really matter if there is a section split there.  You'll run into issues if you use Blending to create that curved tip.  Because the mapped UW surface is bent using Blending, the interpolation between a 'straight' edge at the TE and a 'curved' edge at the LE will cause a deflection at the section break.  You can get around this a bit by approximating the curve using multiple splits but you'll have to tweak the CS parameters to get something with a straight CS LE.

[Fabien R]

On 09/06/2022 14:53, Brandon Litherland wrote:
> Fabien,
>
> Sorry about the Control Surface bug. I found and fixed it but that hasn't
> been pushed to 3.28 yet. You should be able to get version 3.27 to add CS.

I'm a bit puzzled. Debugging v3.28, I noticed that there was no instruction
if ( type == vsp::SS_LINE_ARRAY) in SubSurface* Geom::AddSubSurf( int type, int surfindex ) of Geom.cpp
I checked out the tags OpenVSP_3.27.0 and OpenVSP_3.27.1-176-ge9bbe6b8 with the same result.
Which release are you using ?

> The trick out at the tip is that you're looking at a 5-sided polygon rather
> than a 'rectangle' per se.

I know. I was just focusing on the elevator part of the elevon to start.

> matter if there is a section split there. You'll run into issues if you
> use Blending to create that curved tip. Because the mapped UW surface is
> bent using Blending, the interpolation between a 'straight' edge at the TE
> and a 'curved' edge at the LE will cause a deflection at the section
> break. You can get around this a bit by approximating the curve using
> multiple splits but you'll have to tweak the CS parameters to get something
> with a straight CS LE.

I'll try that when I can.

Thanks for your support,
Fabien

[Brandon Litherland]

There was a missing pointer in src/gui_and_draw/WingScreen.cpp where the Control Surface option is added to the GUI.  Line 397.  If you are building your own copy of VSP, change that line and rebuild and it will work fine.  You can still add CS to wings using a script in the release version.

- m_SubSurfChoice.AddItem( SubSurface::GetTypeName( vsp::SS_CONTROL) );

+ m_SubSurfChoice.AddItem(SubSurface::GetTypeName(vsp::SS_CONTROL), vsp::SS_CONTROL);

[Fabien R]

On 10/06/2022 11:53, Brandon Litherland wrote:
> There was a missing pointer in src/gui_and_draw/WingScreen.cpp where the
> Control Surface option is added to the GUI. Line 397. If you are building
> your own copy of VSP, change that line and rebuild and it will work fine.

I thought I could do a cherry-pick from the git repo.

> You can still add CS to wings using a script in the release version.
> - m_SubSurfChoice.AddItem( SubSurface::GetTypeName( vsp::SS_CONTROL) );
> + m_SubSurfChoice.AddItem(SubSurface::GetTypeName(vsp::SS_CONTROL),
> vsp::SS_CONTROL);

It worked fine.
I tried to use a CS to model the attached rudder, without success.
I suppose it is not that easy.

Anyway, thanks for your support Brandon.
--
Fabien