Prop pitch on the Stealthwake 23

[Davey80]

I’m sure this could be discussed in the prop talk section as well, but since it pertains to the Stealthwake, I’ll start here.

I just picked up a Stealthwake recently and am interested in swapping out the plastic prop for a metal one. I’m working on understanding pitch better and how to pick a new prop.

On the Stealthwake main page, under specs, it lists the prop as 1.6 x 2.5

However,

Under the Stealthwake parts list, it’s prop is listed as 1.6 x 1.6 x 1/8

The Horizon tech I spoke to on the phone wasn’t sure himself why they were listed different but after going to check with someone, said they basically represented the same thing but written differently.

I’m clear on the first 1.6 being the diameter of the prop, and the 1/8 being the shaft size, but hoping someone can better explain the relationship between the 2.5 and/or 1.6 pitch designations and why those numbers could interchangeably be used.

Mark






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[fweasel]

2.5 is the total pitch, 1.6 is the pitch ratio. Diameter x pitch ratio = total pitch. 1.6 x 1.6 = 2.56. A 1.6" diameter is 40.6mm.
Most often, prop sizes are represented by diameter and pitch ratio. Octura, for example does |pitch ratio in inches||diameter in millimeters| ex: x640. ABC lists there's as |diameter in inches||pitch ratio in inches| ex 1616

[Davey80]

2.5 is the total pitch, 1.6 is the pitch ratio. Diameter x pitch ratio = total pitch. 1.6 x 1.6 = 2.56. A 1.6" diameter is 40.6mm.
Most often, prop sizes are represented by diameter and pitch ratio. Octura, for example does |pitch ratio in inches||diameter in millimeters| ex: x640. ABC lists there's as |diameter in inches||pitch ratio in inches| ex 1616

Great, thank you. So to follow that up,

I’m looking at picking up a 40mm CNC prop that has a pitch of 2.2.

Is there any kind of general rule of thumb when going from a plastic prop to a metal prop as far as getting the same pitch, or would the performance difference between a 2.2 pitch and the stock 2.5 pitch not be very significant?




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[fweasel]

You're going to be shopping using the pitch ratio, not the total pitch, more often than not. If the stock plastic prop is indeed 1.6x1.6, that equates to an octura x640. What you're proposing to search for (2.2 total pitch, 40mm diameter, i.e. x440) would be a prop with less pitch than a x640 which will be a slower prop on the same electronics.

Switching from plastic to metal props, all else being equal, the prop will flex less and hold its pitch under higher RPM's which should provide more speed. They also tend to be sharper, making them more efficient with less torque roll (causing the hull to roll in the opposite direction of the prop spin) that is, assuming you're using a CNC or sharpened prop.

[Davey80]

Thanks for the solid info. It’s helped quite a bit.


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[fweasel]

Happy to help when I can

[Bp9145]

Very nice on your explanation Ryan. .very concise and straight to the point. I couldn't have explained it better.