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awparran · Guest

Hi:

I am designing my own aircraft. My wings have different airfoil chords, lengths and heights.

I tried to do this in AutoLisp but the program kept bombing due in part to the number of variables. (Over 300)

I have all of my ordinate data in Excel and need to import them into my present AutoCAD drawings

I am self-taught in AutoCAD 3D, Visual Basics, aeronautics, and aircraft design, etc. I have previously built two full aircraft and flown them. I am still alive to ask these questions. I want to design my own but the repetitive airfoil plots are driving me crazy.

I have followed the tutorials on this site and they seem to work but on a limited scale.

The problem is, I cannot find any mention of how to include and use the COMMAND, LAYER, TOLERANCE function from autoCAD to plot a SPLINE or even a simple line.

And last, when I was running the tutorials and saved them, I later tried to open them but couldn't. i tried to open them with Visual Basic, AutoCAD VBAIDE. Nothing!!!! I was not very happy retyping all of the data I have done the day before.

I could have cut and pasted the examples, but I believe in entering things like this manually so that I understand the process. Is there a way to retrieve these files?

Can anyone help with the above?

Thanks in advance for your time

This site is great!

Tony

Jason Rhymes · Guest

<I have all of my ordinate data in Excel and need to import them into my
present AutoCAD drawings>

Can you post an example of what you have in Excel? I'm not real clear on
what you are trying to do but the excel sheet may help.

Tracy W. Lincoln · Guest

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"awparran" <nospam@address.withheld> wrote in message
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awparran · Guest

i need to add that I have finally been able to, in bits to get VBA to put data into my spreadsheet and also read the data back. What has really been driving me up the wall is when I go to plot the SPLINE.

My program plots a SPLINE but nothing that looks like an airfoil The plot points are 90 degrees out, and the center point is, well, weird.

I have tried to perform the same using a SCRIPT. Same results.

After a month of this I am sure it can be done, but at the same time I could have manually entered my data points and moved on.

Tony

awparran · Guest

Hi again Jason:

Since I am not sure the extent of your knowledge regarding aeronautics and airfoils, please allow me to explain and give a little background information and hopefully allow you to see what my EXCEL spreadsheet accomplishes.

Between the 30's and 40's NASA, or National Advisory Committee for Aeronautics (NACA) published a report (Bible) called NACA TR724 (824) or the summary of airfoil data found during extensive wind tunnel testing. The findings are published in percentages of location, height: both upper and lower. (my copy is yellow with age and well thumbed.)

Although a lot of new airfoils have since been discovered, a lot of the "new" aircraft still rely on this documentation, unless of course your name is Burt Rutan, Cessna, Piper, Beechcraft or Boeing, and have the money and resources to design and plot an airfoil to your diminisions.

Basically when you are ready to build your aircraft and have an idea of the weight, speed, and diminisions, you then look at the various airfoils and determine one that comes close to your needs. After finding the right one(s), you then look into other aspects and then a make a final decision.

It is not this easy and a lot of math goes into the decision, but you get the idea.

In my case, I have chosen the airfoil NACA 63 2 615 as the main wing, NACA 63 2 015 as the flaperon and NACA 5521 as the vertical and horizontal wing surfaces.

My airfoils are not of a constant chord or width, so I must calculate each. If I say my overall main wing is 63" at the root or the centerline of the fuselage, then the main wing is 85% of that length and the flaperon is 15%.

I already have a basic outline of my aircraft in AutoCAD 2000 3D.

So as I have done in the past, I have measured each wing chord and stations 24" through 144" to the wing tips and entered that data in EXCEL.

I have then painstakingly entered this data manually in AutoCAD using SPLINE.

The main wing leading edge is 21.32" in front of the center of gravity. The root overall chord is 63" and the chord centerline is 42" above ground reference.

If I make a mistake, then I have to start all over again. It took a week just to get the inner 8 airfoils, only later to discover that my tolerance was not as tight as I wanted it to be so each airfoil has a dip in two places.

Now I must delete these airfoils and enter them in again.

I had hoped to have a program in place by now to automatically plot these points.

I must add that since, at present each location has two faces 3/8" apart if I use my preset selection of materials, then I need to calculate each surface and plot it.

By the way, this does not include any lightening holes, stiffeners, webs, etc.

A lot of work.

I hope this helps understanding my EXCEL spreadsheet.

Tony

awparran · Guest

Hi Tracy:

Thanks for the input. I will look into these references. If you look above, I have added more information for Jason that might interest you.

Tony

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