Full Version: smoother lofting?

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You can cap the end of this with blend. Manually choose a number like 4 to get a more proportional looking result

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That's beautiful, but I haven't quite figured out how you did it. I don't think I've ever used the blend function, so I'll need to do some research. Is blend the only function you used, or something else first? Everything I try with blend just says calculation failed. Off to do some research.

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Hi Rusty,
To get that result, use the 5 section file.

I rebuilt the curves to clean them up a bit. Default setting

When you run loft, you will see a bunch of points in a line. These are the lofts seam edge. while in loft, drag each of those seam points down to the tip of the trailing edge of each section.

This will help loft with a uniform span.

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The blend option i mentioned was just for the "Cap" at the end of the prop. If you seperate the final surfaces edge into even segments, you can run blend on the 2 edges and generatea nice cap. In the blend function, you can manually enter larger numbers than the commands slider uses,

I'll make you a quick video to show you the process.....

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I made some progress on the lofting with the suggestion to move the point to the end of the curves. A video would make you my hero though :-)

I also tried it with the 25 element file and it wasn't necessarily better. There's always a point maybe 1/5 of the way from the hub toward the tip, but I'm thinking that might be the program. There are settings to change the thickness of the blade at the root and tip, then another slider for the curve between those. I'm still very much learning that program as well. "Mecaflux Heliciel"

Thanks!
Rusty

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Hey Rusty,
I created a couple vids, but posted them in their own threads.

The Blend Cap vid is here: https://moi3d.com/forum/index.php?webtag=MOI&msg=11890.1

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I made a vid of your 5 profile loft here: https://moi3d.com/forum/index.php?webtag=MOI&msg=11889.1

The 25 profiles have a couple sections that arent very good to add in. a size variation creates a weird result.

You'll want to revisit creating sections in the original app to check numbers. More isnt always better. It does give more finite control. But you have to be more precise in variations between sections

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I really appreciate the help, and videos. The most amazing thing about MOI is this forum. I don't think I've ever asked a question that didn't get a nearly instant response that's above and beyond what you'd ever expect.

I had never heard of the "rebuild" command, but I do see it in the list of additional commands that don't have buttons. I'm not sure I can see any difference from using that or not, but it's probably good practice in general, and probably required in some cases.

Part of the difficulty is in fact how the program created those airfoil profiles. When you pick an airfoil, it has a fixed proportion of length to height. That's the ideal way to use it, but it's not always possible. In the case of the prop blade, this makes it very thin at the root end where most of the stress is. If the prop is CF, that's fine, but when you choose wood as the material, the program tells you it's going to break pretty much everywhere but the tip. You can force the airfoil profiles to become thicker at the root to add strength without really effecting the prop function. The program then plots the transition of that extra thickness from root to tip in an ellipse that you can control to some extent. That elliptical transition seems to cause problems with how well the lofting works. Attached is another file where I left it set to constant thickness, and it's very clean. I'll have to find a work around for this, but at least I think I probably can now.

Thanks again!
Rusty

Attachments:
test prop 36 5 elements constant profile.igs

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Hey Rusty,

"""""""""""I had never heard of the "rebuild" command, but I do see it in the list of additional commands that don't have buttons. I'm not sure I can see any difference from using that or not, but it's probably good practice in general, and probably required in some cases.""""""""""""""""""""""

If you open your original 5 station igs file and select "just one" of the profiles and run extrude on it to view a surface, you cn "SEE" some seam edges. These are also HARD edges (edges which are not tangent.

Running rebuild is a method to remove seams like this and clean up hard edges

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Hamish in this forum created and NACA Airfoil Generator around 10+ years ago. It has a function to control the trailing edge coefficient a4

You should check it out to see if you can use it in tandem with your current calcs

Image Attachments:
NACA Airfoil.jpg 

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Seems remember that i have add something very recently (25 december) in the Naca thread! ;)
https://moi3d.com/forum/index.php?webtag=MOI&msg=7265.32

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Here is the link to the MoI command to work with. This link points at an updated version that works with current V5 beta....

https://moi3d.com/forum/index.php?webtag=MOI&msg=7265.27

Give this MoI command and workflow a try before you leave the forum and work with other software which has nothing to do with MoI....

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""""""""""Seems remember that i have add something very recently (25 december) something in the Naca thread! """"""""""""""""

That program is written for and designed for "Additive Manufacturing"....... (That means 3d printing)

A CNC Machine does not add.....

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I see what you mean about the rebuild. I'll definitely have to remember that.

As for generating anything naca related, I'll be dependent on the other program for that. They have a large database of profiles built in. It's amazing how many variables there are, and how much they effect the function of the propeller. Fortunately for me, this is more for fun than actual use, though I could potentially make a prop to use.

I think I'm past this particular hurdle, but there will be more I'm sure. CAD has always been a struggle for me, but at least MOI makes it much less painful.

Rusty

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Understandable....

Have fun Rusty!

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And no doubt that someone will make a Naca dynamic modeling with Elephant! ;)

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"""""""""""""There are settings to change the thickness of the blade at the root and tip, then another slider for the curve between those"""""""""""""""""""

These 2 values actually relate to each other mathematically in airfoil design. The changes have to be planned.

Changing the chord length from 1 station then back again right After it within just 3 stations will be a no no....

You can check your chord lengths. They usually taper from root to tip.

I think the trick is to choose a "ratio" as a percentage of lift coefficient, then stick to that as you change the thickness or chord length (Or Both)

Choosing this chactoristic allows you to pick and choose a change you want, but maintain the aerodynamics as you go...

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