Issues with loft function

tom_bog

Hello, I’m quite new to Onshape, and I’m having some issues with the loft function.

I’m trying to create a propeller blade (3 cm wide) and add a twist to it. I’ve made curves that the profile should follow, and I used airfoil generators to create the NACA profile. However, whenever I try to use the loft tool to make the propeller solid, it doesn’t work, even though I can see it in the preview.

Here is the link to my project: https://cad.onshape.com/documents/e7419fdbceeb1aedf5a14aee/w/d63c0ac54948ba9f04a9457f/e/974e939ac7dedc81f3eca5e5?renderMode=0&uiState=67e00fb6c2a50f63c220a707

Can someone please help me?

Thank You

GregBrown

It's a little hard to tell all we need to know from the view-only link (can you make it so we can copy?)

But there are a few obvious things starting with the profiles:

• the curvature is extreme, in fact goes more or less to infinity, at the trailing edge. This won't go well in your loft…

• looking at the leading edge, the curvature is also suspect, but the diagnostic combs can't capture the full extent since they are being scaled by that trailing edge….
• You have a single spline for the full profile. It is much better to have 2 splines, one for top surface, one for lower surface of the blade. This is especially true if you are using a zero thickness (sharp) trailing edge (and the reason for your bad curvature at the TE currently)
• the spline has a very large number of points. It would be better to do some smoothing and reapproximation. What was the data source you sampled these points from?

I think with cleaner profiles the loft would be much more successful, so I suggest looking at that first. The path with 50 sections will be the next thing once the profiles are addressed…

For clean aero profiles there is a custom feature I helped develop last year. Give it a try, there are some links on the description page to provide more background. While there are many (about 95) different profiles included, I don't believe NACA8710 is one of them currently. You might want to contact Holbrook Aerospace if that one is vital.

MDesign

Your document is set to view only. Cannot inspect it with out being able to copy it.

GregBrown

It's a little hard to tell all we need to know from the view-only link (can you make it so we can copy?)

But there are a few obvious things starting with the profiles:

• the curvature is extreme, in fact goes more or less to infinity, at the trailing edge. This won't go well in your loft…

• looking at the leading edge, the curvature is also suspect, but the diagnostic combs can't capture the full extent since they are being scaled by that trailing edge….
• You have a single spline for the full profile. It is much better to have 2 splines, one for top surface, one for lower surface of the blade. This is especially true if you are using a zero thickness (sharp) trailing edge (and the reason for your bad curvature at the TE currently)
• the spline has a very large number of points. It would be better to do some smoothing and reapproximation. What was the data source you sampled these points from?

I think with cleaner profiles the loft would be much more successful, so I suggest looking at that first. The path with 50 sections will be the next thing once the profiles are addressed…

For clean aero profiles there is a custom feature I helped develop last year. Give it a try, there are some links on the description page to provide more background. While there are many (about 95) different profiles included, I don't believe NACA8710 is one of them currently. You might want to contact Holbrook Aerospace if that one is vital.

tom_bog

Thank you so much !

You really helped me with my school project!
As you said, the problem was that I hadn't enabled both splines, and the profiles weren't perfectly aligned.
The result looks great : https ://cad.onshape.com/documents/7a13792ef5967edf864ba0a3/w/176362cd9af67624d0ce8a57/e/b2e99b6f42bc41343b1f6acb?renderMode=0&uiState=67e18b0d1fd24658c07fb50b

I will check out the custom feature.

Have a nice one!

NB: I don't know if my previous answer was sent so excuse me if I wrote two times the same thing!