What software do you use?

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orion

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I'd be willing to bet that mechanical shapes are probably created in a bit more optimal fashion in a package like SW since that was originally developed as more of a mechanical design product. The demo I saw concentrated more on "styling" rather than mechanical development. Since things like auto-body development and airplane lofting both fall under more of a styling category, the demo was a bit more appropriate for that end use.
 

Dana

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I've never used CATIA, but by all accouts it's an excellent package for aircraft design (that's what, after all, it was made for), but it's out of reach (financially and in terms of complexity) for 99.9% of the users here.

At the risk of repeating myself, the parametric solid modelers are wonderful when you have the design pretty much worked out before you start modeling it, and/or when you expect to make many minor revisions later. They're much less useful for doing preliminary design where you're likely to make large sweeping changes as the design progresses... you may find yourself boxed into a corner by the original base constraints you chose and have to start the modeling again from scratch. With the direct modelers, you can't change a parameter and watch the changes ripple through the design automatically, but you can chop off half a design and replace it with something completely different without any difficulty, and the initial modeling goes a lot quicker because you don't have to set up constraints and everything.

-Dana

Exceeding the legal fun limit on a regular basis!
 

Woodenwings

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Hi Dana

I agree and disagree. I can model up a whole plane in a few days without any constraints and then push and pull to my heart's content.



After that I can constrain things as I choose. The way you design a thing is very much left in the hands of the designer. I will also make several iterations that I can return to if I F**K up. I find the lack of "hard constraints" disconcerting.



I also have designed many a thing (that will be later handled in the computer by others) where I break all associativness to ensure that they don't inadvertently screw it up and blame me.



Solidworks is cheaper than Catia and easier to use. It sells for around 3K to 1.5K depending on options. it's worth it!



 

Dana

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Solidworks is in the $3-4000 range.

-Dana

1. Programmers are expensive.
2. Press releases are cheap.
3. Therefore, it's cheaper to explain the bug than to fix it.
 

Dana

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Dana, you have old prices, current 2009 version prices are 4995$-7495$. But I would say it's worth every $, it's really good software.
I'll stick with KeyCreator, thank'ya very much. SWX is indeed good software, but also very cumbersome for the kind of design work I do. But as I said earlier, if I were starting from scratch on a limited budget, I'd get the free version of CoCreate.

-Dana

"Naked" means you ain't got no clothes on; "nekkid" means you ain't got no clothes on - and are up to somethin'.
 

autoreply

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Any ideas about flutter and stress calculations? I'm particularly interested in the first since that's a pretty impossible job to do easily by hand/excel/java/mathlab.

Any thoughts?
 

orion

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There are quite a few FEA systems out there that will do a reasonable job of doing stress analysis. But the list gets considerably smaller if you're looking for a package that does composites, especially if you're looking for one that is relatively user friendly. Personally, I use COSMOS/M, which BTW I consider downright user hostile. But it does a fairly good job of handling composite structures so I've kept at it for all these years.

I am probably going to change to something better and so far it looks like Strand7 is going to be my package of choice. I am also looking at several Nastran derivatives but given that the analysis side is relatively consistent from one to the other, it's the user interface that will most likely drive my decision more than anything else.

As far as flutter is concerned, I would leave that to someone who is well versed in the science and who has a verifiable track record of experience. This is nearly a black art and certainly nothing that I would leave to chance if it's something that you're really concerned with. To the best of my knowledge, there is no package out there (at least not in the affordable public domain) that has the ability to do complete flutter analysis and I would have serious reservations about anyone or anything claiming otherwise.
 

autoreply

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As far as flutter is concerned, I would leave that to someone who is well versed in the science and who has a verifiable track record of experience. This is nearly a black art and certainly nothing that I would leave to chance if it's something that you're really concerned with. To the best of my knowledge, there is no package out there (at least not in the affordable public domain) that has the ability to do complete flutter analysis and I would have serious reservations about anyone or anything claiming otherwise.
I agree on that point.
Do you consider yourself to be enough of an expert to analyze flutter behavior of the typical high-end homebuilt or do you outsource this too?

For a 250 KTS IAS VNE composite aircraft, would it be advisable to just design for the basic flutter cases (different frequencies, springconstant and stiffness ok) and make sure they're far away from your VNE?
 

orion

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No, I do not consider myself to be a flutter analysis expert. I know how to design for it (or against it) but do defer to others in their expertise to model and analyze said behavior.

Regarding the aircraft, for that speed range and normal Part 23 derived loadings, no, I personally would not be too concerned with flutter. But that is based on my own experience - I think that if a designer does not have a significant background in designing for this speed range it might be pertinent to undertake some level of flutter analysis or ground vibration testing to verify the design assumptions.
 

Mac790

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If you are talking about flutter analysis, aeroelasticity, etc, check out this, unfortunately it's in Polish (maybe they will add also English version in few weeks), anyway it's a project made by students in my UNI (they are one year higher than I). In short first they created a 3-D model, based on a wind tunnel model (they used 3-D scanners) for CFD analysis, next they created a structural equivalent of the original plane in Solidworks/Femap, I would really like to say you more about it, but with my sh^$$ English I'm not able.

So, for a few pictures check out this page. I won't post those pictures here without their permission.
IWP – Inżynieria Wirtualna Projektowania » Projekt “Iryda”

Seb
 
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ultralajt

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..... I would really like to say you more about it, but with my sh^$$ English I'm not able..
My Polish/English on-line translator says:

At the beginning of April this year, started the project: "Development of methods for rapid estimation of the properties aerosprężystych aircraft during flight tests flatterowych", in which shall Poznan University of Technology (Department of Engineering Design Methods) and the Aviation Institute in Warsaw.

At Our School is a lot of projects, but this is particularly important on the grounds that their participation in it are also specialty engineering students belonging to the Virtual Design Student Research IPA.
University task is to calculate the aeroelastycznych Aviation Institute is part of the experimental one. Used a model of the existing Polish jet trainer-combat PZL M96 Iryda.
Work on the Iridium began in the late '70-ties, even when computers were not commonly used in the design process. All documentation, plans and drawings were made in a traditional way - on paper. Necessary thing to do numerical calculations is a virtual, three-dimensional model of the aircraft, which had to be created. Here begins our participation in the project ... With us came Reverse Engineering (Reverse Engineering), of whom we have recently. As a basis for mapping the geometry of the model served us a tunnel, which was borrowed from the Institute of Aviation. Its largest dimension of the standard-size more than 3m. Transporting him from Warsaw to Poznan proved usually difficult ... but not enough that the engineers could not solve it:)
We used contactless scanner prążkowy ScanBridge to obtain information about the geometry, in the form of point clouds. Measuring range, which is 450 × 450x120mm, was insufficient to obtain a single measurement of the geometry of the whole model. Information from the scans combined into a single cloud with a program Mesh3D. In the meantime, point clouds have been simplified, reduced the number of points and treated with the noise. Further processing of geometry took the Dr. Eng. Michael Rychlik, creating a surface in IGES format, which will serve later as the exchange surface.
What does it do ... a little theory

Aeroelastyka (or aerosprężystość) is a discipline of science that studies the mutual interaction between aerodynamic forces and the forces of inertia and the forces of elastic, deformable objects are affected by the flow of gas - usually air. When the deformation of an object affects the aerodynamic forces, then these forces may cause further deformation, which may further affect the change in aerodynamic forces. Such interaction appears to reach a stable state or lead to divergence and consequently the destruction of the object (source).

Simply speaking, is a combination aeroelastyka CSM (Computational Structural Mechanics) and CFD (Computational Fluid Dynamics), so the calculation is needed aeroelastycznych structural model, network flow and exchange surface, which is an important element responsible for providing information on pressures between the structure of the aircraft, and fluid omywającym it.

The next stage that is hard work continued;)

In Warsaw, trying to flatterowych in the wind tunnel model was flatterowy. So we visited the Institute of Aviation, to better be consulted.
This is the model takes into account the inertia and stiffness of the actual aircraft. Our next task was to create niskowymiarowego model belkowego, which will have the same dynamic properties. We used this program FEMAP, the problem of vibration own rozwiązywaliśmy using MSC Nastran solver. In addition, structural model was created in SolidWorks 2007, which greatly helped us to build a model belkowego in Femapie.
What's next ...

Successive stages in the project will build a network of flow and perform calculations aeroelastycznych. But first we need to identify a dynamic model belkowego that we have created. Already write about this soon ...
 

Mac790

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My Polish/English on-line translator says:
Mitja,

I never translate foreign pages (French, German, etc) into Polish with on-line translators. I always translate them into English, because usually I'm not happy with results, but this translation wasn't very bad.

Just a few more words/sentences:

niskowymiarowego- low dimensional
model belkowego- beam model
Aeroelastyka/aerosprężystość- aeroelasticity
Iridium - Iryda (plane name)
rozwiązywaliśmy- we were solving

In Warsaw, trying to flatterowych in the wind tunnel model was flatterowy - this one is a mess, in short it means, that a flutter model was created for the flutter test.
 

ultralajt

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My latest work in Rhino:

Gnome Omega rotary engine from 1912 (it is not yet finished.. work in progress):


Mitja
 
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ultralajt

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WOW Seb! Thanks for the link to your work! It is amazing!
Pretty poster!!

Yes, I have Deja Vu also...found on one russian forum, so that was the reason to start playing with the engine...making one part after another...

Mitja
 

Dana

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Speaking of engine CAD models, if anybody knows where I can find a 3D model of a 447 or Cuyuna or Kaw 440 I'd love to see it. No internal details necessary. I'm considering all of these for my new design, and it would save time modeling it myself.

-Dana

Press any key... no, no, no, NOT THAT ONE!
 
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