Octura prop pitch

[Dan_Cousin]

I've recently had two octura props measure several mm lower pitch than the old 1.4 X diamater calculation gave. I measured at 70% of the radius and used the 1/8" and 1/4" levels on the Hueghy pitch gauge.

The gauge has been trued up (point sharpened, squared and flat filed the two steel surfaces that contact the stair step shims, and made a custom caliper measured 0.250" and 0.125" aluminum spacers used instead of those stair steps that come with the unit. I believe these improvments take out a lot of slop in the original design and give a repeatable and accurate measurement.

I have a stock 1460 that measures 79mm of pitch instead of 84mm and a 1475 that measured 100mm pitch instead of 104mm

Has anyone found that octura props (in particular the 1400, 1600 series) measure slightly less than the theoretical or is there a specific way and place to measure them to match the octura numbers?

 

[Jim Allen]

Dan,

I found this to be true not only of Octura cast beryllium copper blades, but also true for other manufacturers, who sometimes use various alloys. I have found propellers with blades that are over pitched; under pitch; different pitches between blades of the same propeller & variable pitch differences on a single blade; from what the blade was supposed to be. I also saw this happen when I was casting my own blades, therefore I believe this happens when using the lost wax process to make thin section castings. It should be possible to read the correct pitch close to the blade root, because it is supported by the round shaped hub.

Jim

 

[Terry Keeley]

Sounds to me like you're on your way to going faster...

 

[Mike Hughes]

Dan

I have found that even between different people your pitch measurement will vary. That 70% usually only gets estimated. It is not an exact placement. So not everyone is measuring in the same place. This is fine. Don't get caught up in all the numbers. They are just for reference. What really counts is what the boat likes. I think I only run one boat with a stock prop. The rest have all been bent and cut. So if you are doing all the bending then you will be OK. If you have a few different people bending then you will need to measure them to get your reference number.

Mike

BTW I just measured a 1465 and it came out higher pitch than what they say it should be. 3.58 to 3.75

 

[Dan_Cousin]

I'm trying to figure out if error is in the prop itself or the measurement technique being different than octuras.

 

[Mike Hughes]

I would have to say that the error is in the techinique. You don't know at what point Octura measured theirs years ago. I just adjusted my pointer out from the hub and now I get 3.6. Much closer to what Octura says it is. I have measure props from Mark Anderson and Andy Brown with different results. I was going to add more pitch to those props so I came up with my reference number and pitch it from there.

Mike

PS Some of the props have come out of the bag different than what they are supposed to be. IE Blades are different pitches, over and under, one blade drastically heavier than the other. No matter which, after you run them, you will be changing them anyway because they don't work on your boat.

 

[Jim Allen]

It will not matter at which pitch point diameter; 10, 20, 30, 40, 50, 60, 70, or 80 %; the pitch is measured at, if the blade in question has TRUE HELICAL PITCH from its root out to its tip. If the blade in question has different pitches at different pitch point diameters, it will have variable pitch & will be very difficult to duplicate.

I have measured many Andy Brown propellers & found they have the indicated leading edge pitch as well as the indicated trailing edge pitch. The only area where Andy's propeller blades may be off, is at the hub. This happens when blades are pitched up or down from the cast hub insertion angle. This problem would be evident on any re-pitched propeller blade.

 

[1ernie lafleur]

Dan The pitch numbers that Octura prints in probably AVERAGE pitch . Try taking a pitch reading at 20% of the blade and at 80% of the blade and average the two numbers . This number should be closer to the printed pitch . ERNIE

 

[Dan_Cousin]

Dan The pitch numbers that Octura prints in probably AVERAGE pitch . Try taking a pitch reading at 20% of the blade and at 80% of the blade and average the two numbers . This number should be closer to the printed pitch . ERNIE

I will try that.

when you say 80% you mean from the trailing edge towards the leading edge (tongue) or 80% of the radius?

thanks Ernie

 

[1ernie lafleur]

Dan The pitch numbers that Octura prints in probably AVERAGE pitch . Try taking a pitch reading at 20% of the blade and at 80% of the blade and average the two numbers . This number should be closer to the printed pitch . ERNIE

I will try that.

when you say 80% you mean from the trailing edge towards the leading edge (tongue) or 80% of the radius?

thanks Ernie

Those percentages are of the radius. ERNIE

 

[Joe Warren]

Dan The pitch numbers that Octura prints in probably AVERAGE pitch . Try taking a pitch reading at 20% of the blade and at 80% of the blade and average the two numbers . This number should be closer to the printed pitch . ERNIE

I will try that.

when you say 80% you mean from the trailing edge towards the leading edge (tongue) or 80% of the radius?

thanks Ernie

Those percentages are of the radius. ERNIE

Ernie do you have a contact number for Jim Schafer @ ABC props? thanks Joe Warren

 

[dave roach]

Hi Joe

ABC props go to

www.abcprops.com and click on contact and this will give you his phone no.

Dave Roach

 

[1ernie lafleur]

Joe The number I use is 614-475-4247 ernie