Making a Propeller

I am looking for suggestions on how to approach making propellers. I’ve got to do 4- and 5-blades.

try with a plain surface, switching on edit points selecting one side to twist it to the angular needed and to trim to the shape you need. you can also try twist that may be even easier. then you just order them circular triangular or square trim and join it together. its pretty fast, not sure if its accurate enough in matters of blade twist but i believe it could be a first step.

First i would create a profile curve and revolve to get the centre bullet shape …

Then face on I would divide it into the amount of blades, here 4. Then draw the shape of my blade planar, closed and extending into the main shape …

Create surface from planar curves …

Rebuild surface, with point on so you can see how many you will need, for future point editing …

I would move and rotate points just with GumBall. Once it is how I like and if you need some thickness, offset surface as solid …

I didn’t filet the edges here, but next I would get some intersecting curves to use to trim the main shape for a nice blend surface between the blade and housing …

Offset those curves on Surface …

Trim back some of the blade to make a nice blendSurface …

Once the hole is made on the main shape, I would then run blend surface to make a nice join between the blade and the housing.

Then polar array the blade and the curves to trim the main housing …

IHTH «Randy

If Grasshopper script works on MAC you can test that

I used a lot for my 3D models.


@bigjimslade How accurately does your Rhino propeller model need to match the physical propeller? What data do you have - photos, dimensions, general drawing, detailed drawing, etc?

It looks like you have VBScript in your definition. To work on a Mac it would need to be Python, I believe. Script seems to work, that is great.

I didn’t get any errors, and it didn’t crash Grasshopper. Stepping out, but I will check it out tomorrow, merci !

I thought I would look again and once I changed the file to NACA, voila. I am using v4.

I am happy it works, the option that didn’t work search for a file profile. A dat file, there are some huge database on Internet.

Here are some experiments I have tried:

From faded microfilm I reproduced the frame at the hub and one other frame. I guessed at the rotation of the hub frame (30 deg from rotation axis) and had the rotation of the other frame (28 deg. from normal). The black line is the rotation axis. I knew the diameter of the blades allowing me to create an black curved outline.

This path appears to be a dead end. I can create an edgesrf using the outline and one side of the hub profile:

Or I can do it using a line drawn through the hub profile:

Here is what happens with a NetworkSrf:

If I split the outline curve at the end of the blade axis I can get a nicely shaped top and bottom surface

However, there are an excessive number of control points and I have to use MatchSrf to get the two sides to join.

Here is the same thing with Sweep2. Fewer control points and it the edges join.

However, I am still not yet able to get the blades to join the hub.

Thread on Boat Design Forum about modeling propellers:

Interpreting propeller drawings may not be obvious.

Propeller blades follow a helix or modified helix. They are not planar or simple twist.

This is what I got so far:

any suggestions on literature about propellers anyone?

If you really want to know…