Pitch progression on 19 degree rake 38% BAR AMC props

[Ian Inverarity]

Ian,

I will check one tonight and see what I come up with.

The design pitch report will show the mapping of the blades.

If it was me I would just reduce the cup a little at a time and go

test it. The on- the- water- testing is what is all about anyways.

I have some pretty good numbers that seem to work rather well

on most Road Runner Twin set ups. I have been working with a

few of the Team Road Runner Twin Pilots recently and we are

starting to get more performance out of their boats. I will share

with you to possibly lower the strut settings a little deeper into the

water so the angle of attack is more neutral on your set up. A lot

of people are leaving the strut angle and depth how they had it with

another propeller and then the boat gets very light at the end of the

straightaway and sometimes blows off the water. This is due to the

blade design not lifting the transom as much as some other propellers

have in the past. If you adjust the angle of attack with the new ABC

propellers I think you will see better handling and lower lap times if you

are heat racing them.

Thanks,

Mark Sholund

Thanks for the tips Mark.

I have seen a design inspection report, so was interested to measure one of the 19 degree rake series to see for myself. The point of my original question was my measurements did not conform to what I had expected from the design report, hence I was wondering what others get. It seems that David Wilfong gets similar measurements to me.

 

[dwilfong]

Ian

I have a different way of comparing props than most.

I take the shaft from the balancer and put two props on it to compare.

Look at the props from the side with the hub blade leading edge attaching points lined up.

You can see the heal to tip progression and the lead in rake comparison this way. also can see the pitch difference.

Do this to a few props and you will see a different world than just numbers.

 

[ABC PROPS]

Keep in mind that we do a pitch reduction from the .4-.5 radi to hub on all Abc Props

The 45 bar and 38 bar also have a S-Camber from LE to TE

All Props have a Progressive Rake

The 45 and 50 bar have a 2% of Dia drop in cup at 30 Degree angle

The 38 bar is 1.5% of Dia Drop

Also the 38 and 45 Bar have a progressive cup up the TE from hub to tip

The 50 Bar is straight

All this makes Blade Mapping more difficult

 

[Tom Foley]

Dumb question , BAR ?? Blade Area Ratio ???

 

[ABC PROPS]

Yes

Blade area ratio

Or

The place most of the best designs come from

 

[dwilfong]

So the blade rake dose progress as it goes to the tip?

Very interesting........................

 

[Ian Inverarity]

Keep in mind that we do a pitch reduction from the .4-.5 radi to hub on all Abc Props

The 45 bar and 38 bar also have a S-Camber from LE to TE

All Props have a Progressive Rake

The 45 and 50 bar have a 2% of Dia drop in cup at 30 Degree angle

The 38 bar is 1.5% of Dia Drop

Also the 38 and 45 Bar have a progressive cup up the TE from hub to tip

The 50 Bar is straight

All this makes Blade Mapping more difficult

Jim,

Thanks for chiming in! I don't know what an S-Camber is, is that the distribution curve for the pitch from LE to TE?

When you say they have progressive rake, you mean more rake at the tip than at the hub? So is 19 degree rake an average?

What do you mean by 1.5% of diameter drop in cup at 30 degree angle, angle of what?

 

[Tom Foley]

This looks like a good visual .

http://www.mercuryracing.com/prop-school-part-3-blade-rake/