small holes drilled in prop

[RodneyPierce]

Hugh, there was no holding it with my hand and rotating. I used the 25* sweep to get the above numbers, so i didnt have to undo the prop and rotate it. Then compared to Frank's chart. Im just curious if the above numbers are close to the "advertised" or what others have measured. And just for reference, each of those 3 props above, are all from different people..... So I dont have a "propman" so to speak.

 

[hugh hargett]

Oh okay thats cool then . I wasnt trying to be funny. Id check the stock numbers on impba's website prop charts and see if youre within reason. So you have possibly found a way to do it accurately thats not exactly his method???

 

[RodneyPierce]

I forgot about the charts there! Will look at that in a minute here. No issues man!

 

[Ian Inverarity]

Andy, Jim, John, anyone. Here are the numbers I came up with when measuring LE pitch as David described a couple pages back. If any of you guys can confirm numbers or let me know if they are close or correct that would be awesome.

These are numbers from 3 props that I have here that I just pulled from my prop box.

ABC 1914 - 2.375 LE pitch

ABC 1816 - 2.74 LE pitch

Octura 1450 - 2.59 LE pitch

Just curious if these are even close to the advertised or actual??? Thanks in advance!!!

Rod, measuring at 50% radius with an Orlic gauge, 5 degrees, I get one blade of my 1816 as 2.66 LE pitch, the other blade 3.02. My 1450 has 2.59 LE pitch on one blade, 2.66 on the other, I checked two 1450's and they were the same. I don't have a 1914.

 

[RodneyPierce]

awesome, thanks Ian!!

 

[RodneyPierce]

except i dont think its so easy to achieve zero slip.....

 

[hugh hargett]

I think within 3 percent on a rigger some say 85 percent of the mph number it kicks out. It should get you pretty close.

 

[shoboat]

Slippage will most likely be in the 30 to 35 % range.

 

[RonShaw]

Slippage will most likely be in the 30 to 35 % range.

Mark,

I agree, especially with the "slippage holes" that were added........

I personally use 20% slippage for my tipped props, and 25% slippage for my rounded tipped props, when using my prop calculator. The holes will add more slippage, and the amount will be determined by the placement, (leading/trailing edge, closer to hub or tip). Again, not an exact science, just works for me.....

 

[Christian Lucas]

It´s a crazy thing with slip.There are some prop out that do 80% slip and they are realy good propellers .But they run most on tuggboats giving big trust . Remember , No slip ,No trust and without trust no speed .and some prop working with high slip can do there job with high efficancy.

 

[hugh hargett]

Andy, Jim, John, anyone. Here are the numbers I came up with when measuring LE pitch as David described a couple pages back. If any of you guys can confirm numbers or let me know if they are close or correct that would be awesome.

These are numbers from 3 props that I have here that I just pulled from my prop box.

ABC 1914 - 2.375 LE pitch

ABC 1816 - 2.74 LE pitch

Octura 1450 - 2.59 LE pitch

Just curious if these are even close to the advertised or actual??? Thanks in advance!!!

Rod, measuring at 50% radius with an Orlic gauge, 5 degrees, I get one blade of my 1816 as 2.66 LE pitch, the other blade 3.02. My 1450 has 2.59 LE pitch on one blade, 2.66 on the other, I checked two 1450's and they were the same. I don't have a 1914.

Getting your blades pitches to match as closely as possible is a good idea no?

Andy/Christian Im interested in more conversation about the tether pitch props and what it would take to run one.

Hugh

 

[Terry Keeley]

Here ya go, found a post we jacked from Phil, lot's of good info there:

http://www.intlwater...peedmaster&st=0

 

[Andy Brown]

Andy, Jim, John, anyone. Here are the numbers I came up with when measuring LE pitch as David described a couple pages back. If any of you guys can confirm numbers or let me know if they are close or correct that would be awesome.

These are numbers from 3 props that I have here that I just pulled from my prop box.

ABC 1914 - 2.375 LE pitch

ABC 1816 - 2.74 LE pitch

Octura 1450 - 2.59 LE pitch

Just curious if these are even close to the advertised or actual??? Thanks in advance!!!

Rod, measuring at 50% radius with an Orlic gauge, 5 degrees, I get one blade of my 1816 as 2.66 LE pitch, the other blade 3.02. My 1450 has 2.59 LE pitch on one blade, 2.66 on the other, I checked two 1450's and they were the same. I don't have a 1914.

So at 30k rpm that give you approx 80mph for the 1816 (2.84 ave) and 74 mph for the 1450 (2.625 ave) at 0 slip

That's right on, but you will still find yourself using the Slip/fudge factor because you are not using the true leading edge pitch number.

Try putting you prop on the gage upside down and see what kind of L.E. pitch you find. Different huh?

When you find the True L.E. pitch and you adjust the progression to match the drag of the hull, you will find ZERO slip at the L.E. and XX,XXX RPM times X.XX" L.E. pitch equates to the exact speed your boat is running.

 

[Ian Inverarity]

On my 1816, measuring on the back face of the prop the LE pitch (at 50% radius, Orlic gauge, 5 degrees) of one blade is 2.3", the other is 2.16". On my 1450, one blade was 1.8", the other 1.73"

 

[hugh hargett]

Just wondering Ian why you took the numbers at 50% versus 2/3rds out? No one has talked about it but to get a good image of the blade seems like youd take measurements at several rake line and pitch line intersections? What would be nice is using a 3d imager that could import directly into cad then you could look at any aspect or the prop and get fairly accurate results all for 30K in cash.

 

[Terry Keeley]

Does a certain prop's slip stay constant throughout the rpm range?

Is it the same at 20K as it is at 30?

 

[hugh hargett]

I doubt it. Terry it seems at a lower rpm there would be less slip . In FE you can see what im saying if you launch with very little throttle the prop would cavitate less. At speed I dont know how it would work out. Based on what John Beardslee was saying about props some time back about the props that seem to have almost a second gear as they stopped cavitating at a higher rpm range - opposite of my scenario, but still leaning towards the fact that props may slip different at different rpm ranges. Either way I still doubt it stays the same.

 

[Andy Brown]

Does a certain prop's slip stay constant throughout the rpm range?

Is it the same at 20K as it is at 30?

Look at the extremes. A very blunt prop turn 1 rpm would go though the water without disturbing the water much. Tur that same very blunt prop at 20,000 rpm and it would stir up very agitated mixture of air and water. So it seems the answer to your question would be, Yes.

 

[hugh hargett]

Andy, Terrys question suggest that the slip stays constant your scenario suggest otherwise so is the answer to his question yes or no? Yes means that yes slip is the same at different rpm. I thought the same as you did with the lower rpm scenario but that would make the answer to his question "NO" slip is not the same at different rpm ranges right?

Hugh

 

[John Finch]

Rodney were just asking questions here anything else is imagined. Dan simply shared his experience with props. What you speak of with MS is an issue between he and I and has zero to do with this thread. Andy Brown likewise has zero to do with this thread or my source of information. If we need to open a seperate thread on pitch gauges feel free to do so but the issue between Mark Sholund and I is best left between Mark Sholund and I. I would have asked the same question of any other prop man that threw this guage in the mix. Its absolutely un-personal and the AB thing is imagined. Ive only talked to Andy through email corresondence in months in reference to purchased propellers - not that its anyones business.I will leave up to others to explain how the pitch guage made it on this thread and why???? :huh: I just figured since it went there lets talk about them....... Please pm me this kinda stuff coz it really has no place here and is a perfect way to kill a good thread where I an others are looking for answers.

thanks,

Hugh

- On Andy Brown - Andy Brown is a pioneer,teacher, and mentor of rc boats. He has perfected many props(abc h & s) and boats before some of us were born and likely while we jabber here is doing more of the same. When it comes to him comparison is stupid and ill advised. He is a "one of a kind" propeller guy whos stats speak for themselves.Andy is a well respected rc boater in my book. No matter what differences he may have had with this or that one when it comes to rc boats the man is the tops... and likely a Hall of Famer. He is also one willing to still learn and that in my opinion is his strongest asset -

with that said lets let it go coz theres nothing to argue unless you can find 10 people to disagree which I doubt you can. Enuf about Andy Brown, guys ears gotta be on fire by now dang.

FYI record books show there are other people that do not sell propellers that do excellent prop work. Kenny Stone,Terry Kelly,Don "Hackmaster" Ferette,Doug Smock, just to mention a few. Lets stay away from the prop guy competition and learn about the various pitch gauges strenghts and weaknesses.If thats what were gonna do.

I saw the gauge Keven just sold on IW. This is the type you speak of? Tell me what are its strenghts and weaknesses if there are any????? Were going to need a pitch gauge thread. Im not the only one here that has never used one. Im just not ashamed to admit it...... <_<

Hugh

Hugh,

Just read this for first time. Interesting reading. Note, Don ferrette is not the Hackmaster. He doesn't do props at all. He hates working on props. The Hackmaster is Steve Sutton. Just wanted to get that one straight.