since it is supposed to be the best thing for lightly loaded cruise conditions. I guess 10% different is significant, but the Autoprop has too much drag under sail for me. I am curious how much the flat blades do vs. the various planforms. The geometrically correct blade twist for a fairly high revving sailboat prop isn't really much - around 3 degrees from 1/3 dia to the tip. Because the blade speed is very high compared to the boat speed through the water its "apparent flow" direction doesn't change much. A high speed powerboat is very different, as is a workboat with a large slow turning propeller. More twist required on them. Also, most of the twist we are used to seeing on fixed blade props is near the hub. But a feathering prop has a large hub, a lot of that blade root area isn't there. I don't know what it all means, and I have discovered there is very limited study on it. Almost all the prop literature is on big ship propellers, and directed at different problems. I'm not sure how applicable it is to sailboat auxiliary props.