This is a cross posting from the Gallery section becaue I failed to realize that that was where I was posting it earlier.

It isof a fixed-pitch propeller (FP or FPP), but I plan to explore controllable pitch and controllable reversible propeller (CPP/CPP), too. I hope the array or rotate copy tools can accommodate when I get there.

Just last night, I figured out how to draw ship propellers better than I was doing horribly last year. I got the inpiration by warching a tutorial of a twisted vase and flower with petal and bulb. I should have mentally arrived at this in 2009, not last night in 2012. Worse, last year I wasted inordinate amounts of time drawing wires when I should have thought of deformations of prismoids and thickeneded surfaces. Cheers!

Consider initialy experimenting with a crude figure-8-like blade. Also, consider whether you will use one propeller or two. Also, consider whether they turn inboard or outbord as this will determine which way you prefer to draw, and whick way you mirror, as well as which side you manipulate the parent blade.

You will primarily use these key tools : the Extrude tool, Twist tool, Bend tool, Radial Copy [EDIT: POLAR DUPLICATE , not Radial Copy] with Associative copies setting on.

Change the view to looking down the long axis

Draw a line for the extrude path

Draw along that path a tube representing the diameter of the propeller

Remember that you will draw one blade but do so at the approximate intended position, NOT AT ORIGIN IN MODEL SPACE? Why not? Later, whenyou make radial copies and translate move the blades, they will for some reason expand or radially reposition away from their parent. (I am still troubleshooting why)

Explode the edge at the hub area to obtain a circle representing blade tip distance from the hub

If your new circle is segments, create a new one using the Circle, 3-point tool

Draw a smaller, concentric circle to represent the shaft diameter and attachment to the hub bossing

Hide the barrel/oversized tube

Activate a plane for keeping the first blade in line with the hub and bossing

From the hub outer curve, create one or two splines in the shape or profile of a raked, skewed blade (use the Internet to find relevant cross section examples), out to the maximum diameter or tip distance

At the hub, use another curved spline which is not joined operationally, but merely is snapped to the blade profile (do not join as joining introduces accurate but excessive amounts of control points)

Shape the blade such that a sharpish tip is a slight bit lower than the hub origination point

Shape the blade such that the leading edge or advancing piece has a surface are similar to your Internet findings.

Shape the trailing edge accordingly.

Add more control points in advance to later on avert vanishing solids if the model curvature is too tight for the manipulated cover surface tou will create shortly

Add a cover surface

Thicken the blade to some representative amount but one that allows you to see see what is going on

Hide the cover surface

RADIAL COPY TOOL

Radialy copy the blade to 5 copies, associatively, around a 360 deg path

USING THE TWIST TOOL

Test making finer adjustments without solid matter vanishing

Set the twist angles to somemthing such as 22 deg start and 65 deg finish

Notice that the associatively-created blades adjust. For cooler effect, place the solids on layers separate from the surface and radially copy the untwisted parent surface, noticing the geometry shift as the blades change orientation. More change can be observed if later on you create rotation or blade pitch rotation points to simulate putting the propeller blades in forward and astern positions.

Select a twist path experimentally, sampling from hub to mid point, hub to leading edge centroid, and hub to tip

Inspect it, and if necesary, use Ctrl Z or the Inspector to change values.

USING THE BEND TOOL

Use the Bend tool to add realistic bending of the blade to achieve raking and skewing wnd other effects

Use the Blend/Blending tool to round out or sharpen the blade leading and trailing edges, and to more realistically match the transition from blade root to shaft bossing.

ENJOY!

In the propulsion systems.pdf, on page 6 (IIRC, from the Davis Colt url) is a photo of a raked, skewed, twisted screw I am modeling for insertion into my drawing. I may try to sweep a cross section of a foil, to have more control of the curvature of the leading and trailing edges. To use two rail sweep, I have to segment my blade cross section near the tip, since some shapes "break" and lose the solid if the curvature is too dramatic, something approaching 90 deg.