Help understanding props...

[Alessandro Garabaghi]

So pretty new to the rc boat world.

Picked up the C1 Flowmaster HK Cat

Setup:
Neutral Trim
2x 3300kv
2x 3s 4000mAh
2x 60amp esc

Props:
Stock: 36x1.4 3blade (39.1mph)
2nd Set: 36x19 2blade cnc (43.9mph)

Reading on another forum other people have gotten much faster speeds (~58mph) the the stock setup and 38x1.8 3blade...

When i do the simple maths of 38x1.8 and 36x1.9 they equal 68.4 (which i believe is the number you look at to see how many mm 1 rotation will push?)

How come such a difference in speeds?

What are the main differences with 3 and 2 blade? From real boat world, 3 blades were for top speed, and 4 blades are for low end torque (wakeboard world).

[Tamelesstgr]

Great prop info in the Sticky section of Prop section:
http://forums.offshoreelectrics.com/album.php?albumid=991

My favorites for basic prop understanding:
http://forums.offshoreelectrics.com/album.php?albumid=991&attachmentid=87269
http://forums.offshoreelectrics.com/album.php?albumid=991&attachmentid=87336
http://forums.offshoreelectrics.com/album.php?albumid=991&attachmentid=86485

[Alessandro Garabaghi]

good reads.

Basically similar to real boat props...

Now i just need to find a way to get props for cheaper than $20 - $30 each!

Does anyone make 37-39mm 1.4-1.8p plastic 2 / 3 blades i could test with before dropping a bunch on cnc / metal?

[NativePaul]

Graupner make good carbon reinforced plastic low lift 1.4 pitch blades around that size, a few 1.6 pitch too.

[Jamey]

How come such a difference in speeds?
.

An extra 2mm diameter plus 3-blade is pushing more water and is slipping much less than the smaller 2-blade.