Pushing 100 RoadRunner Twin 90s VACs

[Marty Davis]

I go faster with T.E. cup. I could care less about leading edge pitch. I normally cut as much of the leading edge off that I can......

Joe,

Cutting off the leading edge of progressive pitch props increases the leading edge pitch. You may not care but you are changing it.

Ian.

Ian, we must use what we have & Must do what we have to do...... I agree, removing the low leading edge pitch..... will advance the prop to a New leading (higher Pitch # ) But Laying to thrust cone down to a much lower angle 30 or lower is the ticket to Speed. Prop Cupping has been done for ages to advance the T E numbers.

I hope that you paid attention to this statement: "But Laying the thrust cone down to a much lower angle 30 or lower is the ticket to Speed."

This is IMPORTANT.

 

[Scott Norris]

I go faster with T.E. cup. I could care less about leading edge pitch. I normally cut as much of the leading edge off that I can......

Joe,

Cutting off the leading edge of progressive pitch props increases the leading edge pitch. You may not care but you are changing it.

Ian.

Ian, we must use what we have & Must do what we have to do...... I agree, removing the low leading edge pitch..... will advance the prop to a New leading (higher Pitch # ) But Laying to thrust cone down to a much lower angle 30 or lower is the ticket to Speed. Prop Cupping has been done for ages to advance the T E numbers.

I hope that you paid attention to this statement: "But Laying the thrust cone down to a much lower angle 30 or lower is the ticket to Speed."

This is IMPORTANT.

Keeping up with this thead but "Thrust Cone" lost me. Can you enlighten me?

 

[Rick Doane]

OK............It has been pointed to me that I need to be more direct.

How do you measure Cup?..............Well. I have an answer. It's Bullship. What is the error in a measurement based on travel of .125 or .187 compared to .687 travel? It does not matter which prop guage you use!

I have never been shipped a prop that is what I have specificaly ordered. I only order props with a specific diameter. Period. I am resposible for the rest of the numbers. I expect it to be at least balanced which it is rarely the case. The individuals that provide this service take on a responsibility that none of us want. It is a HAZZARD and THAT is what we pay for.

Does anyone here know how to measure CUP? If you do ..........please let me know.

 

[Tom Foley]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

 

[Piston1]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Mr. Foley with respect, Mr. Doane is not wound up at all. We are simply pointing out the inconsistencies that we have found. As you pointed out you might not be a prop technician and nor am I, but Mr. Doane is a prop technician. We very seldom find so called props that are ready to run, properly balanced, etc. We too have to do the extra "tweaking" that you refer above and we also run many CMDI, Sholund, etc. beautiful and well crafted props. It should be pointed out that we struggle with finding out the claimed cup pitches across the props that most of the suppliers claim. Rather than cupping I am more concerned with full blade pitch. You might be happy with your deliverable but I am trying to improve it.

 

[Rick Doane]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

 

[Michael Costanzo]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

hi rick,so can you tell us how much real world pitch these big 91vac can pull?thanks,mike.

 

[Joe Warren]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

Rick are you saying you Do not Measure C.O.B. pitch? or consider T.E. cup? are you changing it to Cup Geometry or Propeller Calculations? the C.O.B. number or T.E. numbers are Only Reference Numbers. Just like the set up number on your riggers. Most are still trying to find where it is........ Not What it is?????? Propeller Cup: Definded as PROPELLER CUP IS SIMPLY THE DEFORMATION OF A PROPELLERS TRAILING EDGE TOWARDS THE PRESSURE FACE OF THE BLADE ... Plain & simple. Take a look @ Larry Boat Again in the video. Marty had the prop shafts index to T.D.C.. Too.... it is HAULING ASS....... I would take a set of those props over a Mountian of BS......... :lol: :blink:

 

[Joe Warren]

Most of the prop experts have some type proprietary systems of rating cup & Where it is measured @...... Most of us own a Steve Wood pitch gauge that suggest measuring @ 70% off center of the hub I know Sholund uses this same tool..... Maybe we need Steve Wood or Mark here to tell us all about the Woods measuring device Marty, are you using a Huey tool?

 

[Joe Warren]

Maybe we have the wrong tools to measure with? I have a set of Small Radius guages that could work for measuring props.If you want to Measure the Cup ONLY? These same tools are used to measure given radiuses on Annual OSHA Crane Inspections. Facts are you need Many More tools Tuning props for a Twin......... For a Single Rigger or a Mono I just need a $8 pair of Prop Pliers....... B)

 

[Piston1]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

hi rick,so can you tell us how much real world pitch these big 91vac can pull?thanks,mike.

Hi Mike, 100mph approach is claimed in this thread . Simple math, assume RPM and slippage variables.... Play with fantasy world, not real world....

 

[Ian Inverarity]

Joe,

Thanks for the tip on the low thrust cone! B)

I was making a comment that another boater Had stated that we cannot go any faster than Leading Edge Pitch X RPM....... I go faster with T.E. cup.

Are you saying here you go faster than the leading edge pitch by cupping the T.E? How much faster? How did you work out you were going faster than the leading edge pitch? I must admit that in testing with a rpm logger and a Stalker radar I havent been able to do this with props I have been cupping.

Ian.

 

[Tom Foley]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

Rick , what I was trying to say is that this term "Cup " means different things to different people . It seems that in the RC world " Cup " is a term used by some to describe the pitch in a generalized area of the blade for reference purposes to have a baseline of measurement . Surely these props are recieving GRADUAL increases in pitch from leading to trailing edges and not just an abrupt trailing edge cupping . Many people have gone over 100 mph with CMDI 1667's (not me lol ) , thats for sure . So I think that really the term "Cup " is subjective and really depends on how one uses it to apply to what they do and what they have in terms of their props . Thanks for the discussions here of course , we all need this info .(gotta catch those VAC powered boats ! )

 

[Rick Doane]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

Rick , what I was trying to say is that this term "Cup " means different things to different people . It seems that in the RC world " Cup " is a term used by some to describe the pitch in a generalized area of the blade for reference purposes to have a baseline of measurement . Surely these props are recieving GRADUAL increases in pitch from leading to trailing edges and not just an abrupt trailing edge cupping . Many people have gone over 100 mph with CMDI 1667's (not me lol ) , thats for sure . So I think that really the term "Cup " is subjective and really depends on how one uses it to apply to what they do and what they have in terms of their props . Thanks for the discussions here of course , we all need this info .(gotta catch those VAC powered boats ! )

Tom.........I agree with you on that. Too often people use the wrong term to describe their prop pitch. Most props I get are at stock or "as advertised" pitches. The largest problem I am having is finding the advertised "Cup" pitches anywhere on the blade. And when I do, this number is based on a travel of .125 to .187. There is a bunch of error in those numbers. This can be dealt with by recording these numbers with whatever measurement device you use as long as you do the same thing every time. Then any changes that are made to the prop can be controlled better.

Another subject I have been looking at is rake. Whenever I repitch a prop and especially bend more pitch (1-2 inches or so), it changes the rake angle dramatically. Generally, a lower rake angle is used for lighter boats and higher angles for heavier ones. I believe there is a lot more to learn here. Maybe the prop finishers can chime in on this.

Rick

 

[shoboat]

Rick,

Give me a call and I can help you understand my work and the Wood propeller gauge.

Cup is very easy to understand, I would be happy to explain it on the phone as I am not

a big typist. I am home after 3:00 PM E.S.T. I would like to talk to whoever has an interest.

Thanks,

Mark Sholund

231.590.3023

 

[Marty Davis]

OK............It has been pointed to me that I need to be more direct.

How do you measure Cup?..............Well. I have an answer. It's Bullship. What is the error in a measurement based on travel of .125 or .187 compared to .687 travel? It does not matter which prop guage you use!

I have never been shipped a prop that is what I have specificaly ordered. I only order props with a specific diameter. Period. I am resposible for the rest of the numbers. I expect it to be at least balanced which it is rarely the case. The individuals that provide this service take on a responsibility that none of us want. It is a HAZZARD and THAT is what we pay for.

Does anyone here know how to measure CUP? If you do ..........please let me know.

Rick:

I have heard the prop sharpeners and benders talk about cup for years. I found out when I got the Steve Woods pitch gauge that they are using the lowest step on the gauge as cup and the second step as pitch. Most everyone measures out 70% from the centerline of the prop along the trailing edge as the place where pitch and cup is measured. Since that seems to be the standard, I am not using he same definition.

I made an Excel spreadsheet that converts all the measurements to useful data and a great place to keep records. If anyone has one of these gauges I would be happy to share the spreadsheet with them. Just send me a message and put in your email address and I will send it to you.

PLEASE DO NOT ask for it if you don't have one of the Woods Gauges as it will not do anything for you at all.

 

[Marty Davis]

Joe,

Thanks for the tip on the low thrust cone! B)

I was making a comment that another boater Had stated that we cannot go any faster than Leading Edge Pitch X RPM....... I go faster with T.E. cup.

Are you saying here you go faster than the leading edge pitch by cupping the T.E? How much faster? How did you work out you were going faster than the leading edge pitch? I must admit that in testing with a rpm logger and a Stalker radar I havent been able to do this with props I have been cupping.

Ian.

Ian:

I agree with you on that....

Joe said he gets rid of the tongue (leading edge pitch) as much as he can and that changes the effective leading edge pitch. That is correct. If you want to see this REALLY in play, run an X Series Prop and measure the speed. The remove some leading tongue and check again. You will see that the speed is way up. Remove more and the speed goes up more. REASON: on an X Series Prop they are essentially a prop that has increasing pitch from the first part in the water to the trailing edge. When the water shoots off the trailing edge the next thing in the water is the super low pitch part of the other blade. That acts like a governor and removing that area removes that effect to a large degree.

Joe says that he removes the leading part of the blade on a 1400 or 1600 series prop to do the same thing. Those props are called true pitch props because the pitch is the same across the entire prop. BUT, after adding pitch and cup to the rearward part of the blade it is no longer a true pitch prop. It is more like the X Series Prop and will benefit from removal of the tongue part of the prop.

I would suggest that it makes sense to use the definitions that the prop guys are using so that we all talk the same language. Right or wrong....

Hope this helps.....

 

[Marty Davis]

Rick rather than get all wound up trying to find the specific , all encompassing meaning of this word as to it's application here ,I think that for the discussion and description of the basic meaningful pitch in the part of the prop blade that does the "most work " , to my understanding "Cup " is the term used to describe this condition . Mostly all of the awesome 1667's that i have came from Andy Browns shop and measured almost right on using my pitch gauges both Woods and Hughey in the manner described .

After hammering the props for several races sometimes they need a little tweak to the original condition ..and this is very easily done because the difference between 5.6 and 5.8 " at roughly 70 % blade is VERY minor in terms of effort . I am not a prop technician but have learned a little along the way . The CMDI 1667's and the Sholund 1667's are beautiful and very well crafted ..and fast !

Tom:

In my previous posts concerning "Cup", this is only a means to make a bad prop "ok" and does increase speed. By this, I mean that true prop pitch (full blade) is the number you have to use times the RPM of the motor (including slippage if known or calculated) to dertimine MPH. I always start with zero cup. This way I know how much torque (ie. pitch) I can pull. You would be surprised how much full blade pitch these new motors really pull. I use cup to make the roostertail lay down.

"Rick rather than get all wound up trying to find the specific "

I deal in specifics. This is what makes our boats perform and I do not mind sharing this information. Some of the manufactureres of the props we use have shared their collective information with me just because I asked them. They are wonderful people that have forgotten more about props than I will ever know in my life. Therefore, it is what it is.

Regards.........Rick

hi rick,so can you tell us how much real world pitch these big 91vac can pull?thanks,mike.

Hi Mike, 100mph approach is claimed in this thread . Simple math, assume RPM and slippage variables.... Play with fantasy world, not real world....

I built a speed calculator into the spreadsheet so that I can look at efficiency. Not very well defined but interesting.

I believe now that you can't add an efficiency factor to all props and it will be predictive. I have found that finish of the prop, bend smoothness, etc etc etc etc changes efficiency so that it is not at all useful except as something cool to look at.

 

[Marty Davis]

Rick,

Give me a call and I can help you understand my work and the Wood propeller gauge.

Cup is very easy to understand, I would be happy to explain it on the phone as I am not

a big typist. I am home after 3:00 PM E.S.T. I would like to talk to whoever has an interest.

Thanks,

Mark Sholund

231.590.3023

How about posting your thoughts on here so that we ALL can understand your ideas.

 

[Terry Keeley]

Here's a couple SAW props I'm working with:

I like Franko's gauge mainly 'cause it's small and very accurate.

For my records I take the pitch at 75% and measure LE and TE (or cup) as the first and last 10* of the blade, then measure an "average" pitch over the full blade. Just look at all those numbers.

Testing with FAST bro's Mike Nowicki and Mikey Ross show the boat will only go as fast as the first 1/3rd or so of the blade, think Andy Brown turned us on to this a few years back on Marty's forum.

ps: I won't run a prop unless it's heat treated...