Some cool prop history

[hydroViper235]

[David]

It took me a few days to watch it all.

[KIRCHNER]

It took me a few days to watch it all.

great stuff, i can relate to that era, everyone ran 2blds. i never considered a 3bld. a little late now. only 2 props,O,J. or michigan, mecury had the ELEPHANT EAR, think it was bronze.

[David]

I used to have a 32" pitch 2 blade bronze Mercury propeller. It was of no use to me, beyond a conversation piece. I gave it to a hoarder friend of mine.

One of the interesting bits in the video was a discussion about rake and diameter. Increasing either reduces the lift at the stern on the hydros. I always think of rake as increasing the bow lift. For example, I describe some propellers as having too much bow lift for my SS2000 - that causes spooky handling. I had read before that what rake really does is lower the stern. Apparently that is true.

Another interesting thing is that there are/were just 2 forgings that all the unlimited props were machined from. The size of the forgings set bounds for diameter, pitch, and rake. One of the forgings was/is bigger and could make more variation. Bigger means more machining though to get to the finished size, so more cost.

[KIRCHNER]

i found myself measuring rake/pitch with a snall straight edge. i have quite an assortment. i noticed a big difference from a hydromotive to a high rake scorpion. the hydro blade is flat from hub along trailing edge out to the tip. the solas is flat area is forward towards the leading edge. i suspect the hydro holdhas no progressive pitch where the solas has progressive pitch. apparently rake pulls the stern down, making the bow loose. im going to try a prop i have that has very little rake on my skater18 and see if the porpoising will be more manageable. the high rake on now i cant hold it w o t. too hairy. so much for the [LABBED] b.s.!!

[David - WI]

I think "labbed" means all the blades have the area, pitch & rake that's spec'd... not that it's "right" for any particular job. Grinding the blades down to match means you get thinner blades, too. Strictly speaking, five "lab finished" props would all be identical.

When people say they had a prop "worked" or "tuned" for their hull; they are having the pitch and/or rake changed to suit their boat/motor serup. Five "worked" or "tuned" props would all likely be different.

https://m.youtube.com/watch?v=iBZkgQ_bKj0

[KIRCHNER]

the rake relates to sku. was briefly mentioned at the prop school. a high rake while pushing forward tends to pull down and bite harder. its hard for me to get on plane with a low rake design, but great on the big end,