Help on designing Fuselage

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pinkbigpig
Posts: 7
Joined: Wed Jul 23, 2014 8:24 am

Help on designing Fuselage

Postby pinkbigpig » Fri Aug 29, 2014 3:43 am

Hi all,

I'm trying to use FreeCAD to design some Airplane model. FreeCAD is a very interesting tool. It help me to save a lot of time to design a Wing. Now, I have some problem in designing a Fuselage. I had tried to use Loft, Sweep but I haven't got exactly the model I wanted.

I draw some circles and loft them but the surface isn't smooth. Is there any tool in FreeCAD help me to design a simple fuselage.

Because I'm newbie in CAD, I hope to get some advice.

Thanks for any help!

Leo
Attachments
fuselage2608.FCStd
Fuselage
(43.95 KiB) Downloaded 168 times
Last edited by pinkbigpig on Fri Aug 29, 2014 6:39 am, edited 1 time in total.
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NormandC
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Location: Québec, Canada

Re: Help on designing Fuselage

Postby NormandC » Fri Aug 29, 2014 3:58 am

Hello Leo,

Welcome here.

You thave way too many sections. The loft has to pass through everyone of them, which makes for a rough surface. You need to reduce the number of sections, there should only be a bare minimum. Also, your sections do not follow exactly the contour of the plane (the "Wire" object) which creates those bumps.
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NormandC
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Re: Help on designing Fuselage

Postby NormandC » Fri Aug 29, 2014 4:07 am

You can also make a series of Lofts rather than a single one. Here's an example using a limited number of your existing sketches. I fused them together with the Part Fuse (Union) tool.
Attachments
fuselage2608_normandc1.FCStd
(48.81 KiB) Downloaded 165 times
pinkbigpig
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Joined: Wed Jul 23, 2014 8:24 am

Re: Help on designing Fuselage

Postby pinkbigpig » Fri Aug 29, 2014 6:37 am

Thank Normandc! It's helpful for me.

I want my model follow exactly the contour, so I draw a lot of circles. And now I know it's not a good idea. Thanks again!

Leo
vrytar
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Joined: Wed Nov 21, 2012 10:08 pm

Re: Help on designing Fuselage

Postby vrytar » Fri Aug 29, 2014 12:29 pm

I generally begin with cross sections in the same positions that they were on the real aircraft.
pinkbigpig
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Joined: Wed Jul 23, 2014 8:24 am

Re: Help on designing Fuselage

Postby pinkbigpig » Thu Sep 04, 2014 4:35 am

Hi,
I try some models and I have some questions here.

How can I get this object
Image

instead of this in FreeCAD?
Image

Thank you for any advice!

Leo
Attachments
fuselage_with_xflr5_Loft.FCStd
(12.6 KiB) Downloaded 94 times
jmaustpc
Posts: 9406
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Location: Australia

Re: Help on designing Fuselage

Postby jmaustpc » Thu Sep 04, 2014 7:53 am

Your images are not showing...however if you change the very last digit in you url from 0 to 1, it seems to work. Like this

Code: Select all

[img]https://www.dropbox.com/s/9o9kgbw3373kpfs/fuselage_xflr5.PNG?dl=1[/img]

Image



and

Code: Select all

[img]https://www.dropbox.com/s/oyvv716e25jf1up/fuselage_freecad.PNG?dl=1[/img]

Image



Jim
jmaustpc
Posts: 9406
Joined: Tue Jul 26, 2011 6:28 am
Location: Australia

Re: Help on designing Fuselage

Postby jmaustpc » Thu Sep 04, 2014 8:00 am

in answer to your question....it will be more complex than just this but start by toggling "ruled" property of the Loft...assuming that you did a single multi profile Loft and not several different Lots fused together.

Also If your shape is symmetric about any axis, you might consider making a cross section either in sketcher or Draft if you need splines and then rotating it with either the PartDesign or the Part wb rotation tools.
pinkbigpig
Posts: 7
Joined: Wed Jul 23, 2014 8:24 am

Re: Help on designing Fuselage

Postby pinkbigpig » Fri Sep 05, 2014 2:05 am

vrytar wrote:I generally begin with cross sections in the same positions that they were on the real aircraft.
Hi vrytar, thank you for your advice.
Can you give me some example or some information to make it clear?
jmaustpc wrote:in answer to your question....it will be more complex than just this but start by toggling "ruled" property of the Loft...assuming that you did a single multi profile Loft and not several different Lots fused together.

Also If your shape is symmetric about any axis, you might consider making a cross section either in sketcher or Draft if you need splines and then rotating it with either the PartDesign or the Part wb rotation tools.
Hi jmaustpc, I'm sorry about my mistake.
I know it will be more complex than I did, so I really want to receive your advice. I try to find a way to design a simple fuselage in FreeCAD , which is not symmetric.

Leo
vrytar
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Joined: Wed Nov 21, 2012 10:08 pm

Re: Help on designing Fuselage

Postby vrytar » Fri Sep 05, 2014 9:09 pm

Not sure how well this works for modern planes, but historic aircraft was essentially made by lofting from a few sections. You can see the shapes and positions of the sections in any decent plan.

http://www.fiatcr32.rotorswings.com.au/

I try to create the sections shown in the plan as closely as possible and put them in the right positions. Then I hope the FreeCAD loft function will do pretty much the same thing as real life lofting in the factory. If this doesn't work, I tweak the model, but at least I have a starting point.