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        Discussion Prop Diameter Size vs Pitch

#1 syncronized Oct 18, 2010 02:45 PM

Prop Diameter Size vs Pitch
 
Hey guys,

I'm trying to figure out this whole prop thing still….which has a higher effect... a larger diameter prop or higher pitch. For example….

45mm (1.7") diameter w/ 1.45 pitch = 2.48

VS

42mm (1.65") diameter prop w/ 1.6 pitch = 2.640

Which of these are faster, has more torque, has a higher amp draw?

#2 wparsons Oct 18, 2010 02:56 PM

You have to compare blade area and pitch to really figure that out.

Pitch doesn't effect blade are as much as diameter does, so changing diameter has a bigger influence over load.

You also have to look at blade shape to get the area though, which is where props like the M series (de-tongued) come into play.

As for what's faster, that's really trial and error or going by someone else's results. Some hulls might be faster and more stable with a smaller high pitched prop than a larger one, and others might need a bigger diameter to get it moving.

#3 siberianhusky Oct 18, 2010 03:11 PM

LOL the great prop question!
Depends on way too many things, most of us end up with a number of props because you just don't really know which one is going to work the best with your setup!
Theoretically they should be close in reality they could be miles apart, the extra blade are about equals the extra pitch between the two.
Your hull might like the 45mm prop because it lets the hull sit a little lower in the water because it has less lift, might run too wet though and your amp draw is high, the other with more lift might let the hull run a little free and draw considerably fewer amps!
Two different props you really can't compare them. an x445 is a much different prop than a 1445 even though both are octura both are 45 mm and have the same pitch. An x6 has both more pitch and lift than an x4 series. So you can't really compare those against each other either.
All you can really do is try as many props as possible in the size range until you find the one that runs the best.
So far I have tested 4 props on my rigger and just ordered another a couple of hours ago. Prop testing is an ongoing process depending on what level of performance you are after, eventually you will have the dead calm prop, the one that works best in choppy water, the best race prop etc!

#4 scorpion1 Oct 18, 2010 03:29 PM

I'm gonna say the x642 is faster than the x445. The way I see it, the 45mm 4 series pushes more water, but the 642 pushes less water faster.

#5 wparsons Oct 18, 2010 05:29 PM

^^ Depends on the hull.. A heavier/wetter hull will be faster with the bigger prop in most cases.

#6 syncronized Oct 18, 2010 06:05 PM

GRRRRRRRR......ok I figured there would be more variables in choosing props for my hulls.

Right now I only have 1 metal prop...an x642. But I have a bunch of CF props 40, 42, 45, 47, 48mm...and want to go with some other metal props but don't want to spend the money on buying metal props and find out they don't work well for my application.

So I guess I'll just throw on one prop at a time and see which yields the best results, and then match them up the closest I can with metal props

#7 scorpion1 Oct 18, 2010 07:08 PM

Thats the way most of us do it........start with a CF, then go to berylium. Keep in mind that the CF's are 1.4 pitch and that they flex under load. So a 45mm CF will not give the same speed or heat as a sharp berylium x445.


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