Speedmaster 20 mono, good day testing

[dwilfong]

It makes sense that the front of the blade makes a difference. The whole cross section of the blade is moving threw the water. The wright Brothers understood this with a airo prop. that is what got them off the ground. If you look at pics of a prop running in the water the front side of the blade pushes water around the prop. That takes power. I always spend a lot of time on the back side of the prop as this is what the water hits first. Bending the leading edge dose two things holds the water on the prop and lets the water go around the prop easer.

I love Franco's gauge. Not as fast to use as some but the info is better.

David

 

[Tim_Duggan]

Terry,

Nice tip on the gauge, did you make that?

I wondered the same thing when I saw that pic. I like my Orlic prop guage, but dislike the ball tip on the dial indicator.

Question for the guys adding pitch much earlier in the blade than just toward the T/E where there is some give - are you doing this by hand or using a mandrel?

 

[Terry Keeley]

Terry,

If you go just ONE MPH faster than 3.6" X 28,000/1057 you are PUSHING the 3.6" blade face into the water in front of the prop.

3.6" X 28,000/1057 = 95.4 MPH, therefore you are PUSHING that blade surface into the water at 8 mph when you ran 103+ mph. Can you say Plowing water?!?!

3.89" X 28,000/1057 = 103 mph. So there you have it. The first 5* of the LE is Plowing water and the next 5* will plow more water if you exceed 103 mph. That takes Horsepower!

In reality you have already reached that prop's Limit like Aaron said. Take your time with a file and work that prop by hand to increase that pitch.

Looking forward to seeing how much pitch you can get on it and if the boat speed increases accordingly.

Ahhh, thanks Andy, I see it now. Thought I had the blades nice and thin but obviously I need to do some more homework!

 

[Terry Keeley]

Got my homework done, the first 5* of the LE of the 2170 I am running is about 5.04" at 75%. Turned the blade over and got a big surprize! The first 10* is 3.89" and 5* is only about 3.60".

Using 3.6" the slip reduces to next to nothing, but I'm not sure I understand how the back side of the blade comes into play when the face is doing the work. :blink:

Here's a pic of Franco's gauge and the 2170 I'm working on:

You are observant Ian! It's a Mitutoyo part, I'm sure someone can find it if they look.

Using the standard ball isn't real accurate especially on high pitch props.

 

[Ian Inverarity]

You are observant Ian! It's a Mitutoyo part, I'm sure someone can find it if they look.

Using the standard ball isn't real accurate especially on high pitch props.

Terry, I will try and find the Mitutoyo part. I agree about the issue with the ball, I unscrewed mine and use the end of the shaft, but your pointer is even better.

Ian.

 

[Tim_Duggan]

You are observant Ian! It's a Mitutoyo part, I'm sure someone can find it if they look.

Using the standard ball isn't real accurate especially on high pitch props.

Terry, I will try and find the Mitutoyo part. I agree about the issue with the ball, I unscrewed mine and use the end of the shaft, but your pointer is even better.

Ian.

Ian,

When you track it down, LMK a price please.

TD

 

[dwilfong]

look at MSC. I Got a set of 12 different kinds for next to nothing.

David

 

[Ian Inverarity]

Who is MSC?

 

[dwilfong]

Who is MSC?

http://www1.mscdirec...ItmDtl-_-PypClk

This is the place to get all your tooling. If thy don't have it it don't exist.

Check out the carbide tool at the bottom of page 669. This makes some real nice chamber profiles.

David

 

[Ray Sametz]

http://mscdirect.com

 

[Andy Brown]

Who is MSC?

Manhattan Supply Company.

I don't think they are in OZ

David just didn't know you are South of the Equator!

 

[dwilfong]

Who is MSC?

Manhattan Supply Company.

I don't think they are in OZ

David just didn't know you are South of the Equator!

Thy will ship there too. As long as your not on a different planet. I order at 11:00PM and it's in my mail box when I get home from work. no extra charge for the small stuff.

 

[Terry Keeley]

Top middle of page 2, think I got 137413 which has the finer point:

http://pme.co.kr/cyboard/data/smalltool/190-901312.pdf

 

[Ian Inverarity]

Top middle of page 2, think I got 137413 which has the finer point:

http://pme.co.kr/cyboard/data/smalltool/190-901312.pdf

Thanks Terry, I will try to get one! B)

 

[Ian Inverarity]

Ian,

On this 2260, I just measured the center 20% of the blade and took the sweep at about 60% out. The LE on that same prop was only 4.1" That averaged with the TE gives and average total pitch of 6.3" Way above the Octura pitch claim. What a crazy prop! Over 100% progression!

Oh and to further answer your question some props hold the LE pitch across most of the blade and then only have a TE pitch increase. I prefer the gradual progression increase from LE to TE. All of my CNC props are that way as was this 2260 in question. This helps maintain water/blade contact across the full blade from LE to TE.

I think in Terry's case he is loosing contact and the last half of the prop is only seeing air!...maybe even the last 70%.

When I cup a 1400 prop, which is nearly constant pitch, I reach into the blade to the center and start adding progression there, not just the last 20% or so.

Andy, interesting stuff, thanks for your comments! But I have another question! How would the last half of the prop see air? As in a local bubble or entrained air? Surely for that to happen the pitch of the blades in that area would have to be less than the advance of the prop thru the water. Implying that the first half of the prop is doing all the work and driving the boat forward, but the leading half has less pitch, so how can the higher pitch portion of the prop move thru the water faster than its local pitch to create the air bubble?

Surely a prop creates thrust by accelerating a volume of water backwards. The amount of thrust would be dependent on how much water is accelerated, and how much the water is accelerated. The pitch progression is what would produce that acceleration, on an efficient prop the water meeting the LE would be met by a section of the blade that has similar pitch the actual advance or effective pitch, so wouldnt disturb the water greatly, and as the prop moves thru the water encountering higher and higher pitch sections of the prop the water would be accelerated backwards to create thrust. Surely, on a prop that isnt 'cavitating' on launch, there will always be positive water pressure on the working face unless a section of prop actually reduces in pitch, or is pitched so abruptly that the water cannot follow the blade profile?

Ian.

 

[Andy Brown]

Ian,

On this 2260, I just measured the center 20% of the blade and took the sweep at about 60% out. The LE on that same prop was only 4.1" That averaged with the TE gives and average total pitch of 6.3" Way above the Octura pitch claim. What a crazy prop! Over 100% progression!

Oh and to further answer your question some props hold the LE pitch across most of the blade and then only have a TE pitch increase. I prefer the gradual progression increase from LE to TE. All of my CNC props are that way as was this 2260 in question. This helps maintain water/blade contact across the full blade from LE to TE.

I think in Terry's case he is loosing contact and the last half of the prop is only seeing air!...maybe even the last 70%.

When I cup a 1400 prop, which is nearly constant pitch, I reach into the blade to the center and start adding progression there, not just the last 20% or so.

Andy, interesting stuff, thanks for your comments! But I have another question! How would the last half of the prop see air? As in a local bubble or entrained air? Surely for that to happen the pitch of the blades in that area would have to be less than the advance of the prop thru the water. Implying that the first half of the prop is doing all the work and driving the boat forward, but the leading half has less pitch, so how can the higher pitch portion of the prop move thru the water faster than its local pitch to create the air bubble?

Surely a prop creates thrust by accelerating a volume of water backwards. The amount of thrust would be dependent on how much water is accelerated, and how much the water is accelerated. The pitch progression is what would produce that acceleration, on an efficient prop the water meeting the LE would be met by a section of the blade that has similar pitch the actual advance or effective pitch, so wouldnt disturb the water greatly, and as the prop moves thru the water encountering higher and higher pitch sections of the prop the water would be accelerated backwards to create thrust. Surely, on a prop that isnt 'cavitating' on launch, there will always be positive water pressure on the working face unless a section of prop actually reduces in pitch, or is pitched so abruptly that the water cannot follow the blade profile?

Ian.

Ian,

The progression is needed for one purpose. To maintain blade contact with the water. The prop is a screw. But the water is not solid. When the LE penetrates the surface it screws itself forward according to the pitch of that LE. However, because the water is not solid it gets forced rearward by the initial contact of that LE. So, if the first 20% of the blade forces the water it just contacted rearward, then then next 20% of the blade must have a little more pitch to maintain contact with the water that is moving rearward. The heavier, more high drag hulls require more progression because the water is pushed back faster. Just like spinning your wheels in the dirt! Also the closer the prop is to the surface the more that progression is needed, because the water at the surface offers little resistance. A long prop that runs deep will require less progression because the water is more "solid" down deep.

I ran 114 mph with the Twin 84 using stock full blade 2170's. The progression of those props is no more than 10%, but since I used them at the full 70 mm length they still hooked up and pushed the boat well. If I had cut them to 60mm I would have had to add cup to get the same 114 mph speed.

In conclusion, I only view the prop as the screw that it is. A screw turning into steel does NOT have to accelerate steel backwards to create thrust in order to move itself forward. Nor does a propeller. It only needs something to push against. I this case water. Again because the water tries to move "out of the way" rearward) the pitch of the blade must ever increase to maintain contact with that small mass of water that is moving in the opposite direction (rearward).

Andy

P.S. Ian, I will actually agree that the rearward moving water can be explained with the Mass X Velocity = Thrust equation. The Mass of water is a constant according to the blade area of the prop. So in order to get more thrust (force to push the boat), water must be accelerated to a certain Velocity. This final Velocity becomes the TE pitch times the RPM if the prop is progressed properly. The heavier and more drag the hull, the more the final water Velocity must be. This Velocity of the water is initiated by the LE contact according to the resistance of the hull. The more resistance, the faster the water moves rearward and the more progression of the blade that will be needed to continue contact with the moving water.

So, an LE of 4.0" and a TE of 6.0" @ 28,000 rpm would net out a boat speed of 106 mph( 4.0" X 28K / 1057) The final water Velocity off the TE would be 6.0" X 28K / 1057 = 160 mph.

So in fact the water would move rearward in relation to the boat at 160 mph minus 106 mph = 54 mph.

 

[Terry Keeley]

Wow, I think I'm finally starting to get it.

Thanks Andy for your time and knowledge.

 

[Tim_Duggan]

Ian,

On this 2260, I just measured the center 20% of the blade and took the sweep at about 60% out. The LE on that same prop was only 4.1" That averaged with the TE gives and average total pitch of 6.3" Way above the Octura pitch claim. What a crazy prop! Over 100% progression!

Oh and to further answer your question some props hold the LE pitch across most of the blade and then only have a TE pitch increase. I prefer the gradual progression increase from LE to TE. All of my CNC props are that way as was this 2260 in question. This helps maintain water/blade contact across the full blade from LE to TE.

I think in Terry's case he is loosing contact and the last half of the prop is only seeing air!...maybe even the last 70%.

When I cup a 1400 prop, which is nearly constant pitch, I reach into the blade to the center and start adding progression there, not just the last 20% or so.

Andy, interesting stuff, thanks for your comments! But I have another question! How would the last half of the prop see air? As in a local bubble or entrained air? Surely for that to happen the pitch of the blades in that area would have to be less than the advance of the prop thru the water. Implying that the first half of the prop is doing all the work and driving the boat forward, but the leading half has less pitch, so how can the higher pitch portion of the prop move thru the water faster than its local pitch to create the air bubble?

Surely a prop creates thrust by accelerating a volume of water backwards. The amount of thrust would be dependent on how much water is accelerated, and how much the water is accelerated. The pitch progression is what would produce that acceleration, on an efficient prop the water meeting the LE would be met by a section of the blade that has similar pitch the actual advance or effective pitch, so wouldnt disturb the water greatly, and as the prop moves thru the water encountering higher and higher pitch sections of the prop the water would be accelerated backwards to create thrust. Surely, on a prop that isnt 'cavitating' on launch, there will always be positive water pressure on the working face unless a section of prop actually reduces in pitch, or is pitched so abruptly that the water cannot follow the blade profile?

Ian.

Ian,

The progression is needed for one purpose. To maintain blade contact with the water. The prop is a screw. But the water is not solid. When the LE penetrates the surface it screws itself forward according to the pitch of that LE. However, because the water is not solid it gets forced rearward by the initial contact of that LE. So, if the first 20% of the blade forces the water it just contacted rearward, then then next 20% of the blade must have a little more pitch to maintain contact with the water that is moving rearward. The heavier, more high drag hulls require more progression because the water is pushed back faster. Just like spinning your wheels in the dirt! Also the closer the prop is to the surface the more that progression is needed, because the water at the surface offers little resistance. A long prop that runs deep will require less progression because the water is more "solid" down deep.

I ran 114 mph with the Twin 84 using stock full blade 2170's. The progression of those props is no more than 10%, but since I used them at the full 70 mm length they still hooked up and pushed the boat well. If I had cut them to 60mm I would have had to add cup to get the same 114 mph speed.

In conclusion, I only view the prop as the screw that it is. A screw turning into steel does NOT have to accelerate steel backwards to create thrust in order to move itself forward. Nor does a propeller. It only needs something to push against. I this case water. Again because the water tries to move "out of the way" rearward) the pitch of the blade must ever increase to maintain contact with that small mass of water that is moving in the opposite direction (rearward).

Andy

P.S. Ian, I will actually agree that the rearward moving water can be explained with the Mass X Velocity = Thrust equation. The Mass of water is a constant according to the blade area of the prop. So in order to get more thrust (force to push the boat), water must be accelerated to a certain Velocity. This final Velocity becomes the TE pitch times the RPM if the prop is progressed properly. The heavier and more drag the hull, the more the final water Velocity must be. This Velocity of the water is initiated by the LE contact according to the resistance of the hull. The more resistance, the faster the water moves rearward and the more progression of the blade that will be needed to continue contact with the moving water.

So, an LE of 4.0" and a TE of 6.0" @ 28,000 rpm would net out a boat speed of 106 mph( 4.0" X 28K / 1057) The final water Velocity off the TE would be 6.0" X 28K / 1057 = 160 mph.

So in fact the water would move rearward in relation to the boat at 160 mph minus 106 mph = 54 mph.

IW post of the century! Thanks Andy and Ian!

 

[dwilfong]

Ian,

On this 2260, I just measured the center 20% of the blade and took the sweep at about 60% out. The LE on that same prop was only 4.1" That averaged with the TE gives and average total pitch of 6.3" Way above the Octura pitch claim. What a crazy prop! Over 100% progression!

Oh and to further answer your question some props hold the LE pitch across most of the blade and then only have a TE pitch increase. I prefer the gradual progression increase from LE to TE. All of my CNC props are that way as was this 2260 in question. This helps maintain water/blade contact across the full blade from LE to TE.

I think in Terry's case he is loosing contact and the last half of the prop is only seeing air!...maybe even the last 70%.

When I cup a 1400 prop, which is nearly constant pitch, I reach into the blade to the center and start adding progression there, not just the last 20% or so.

Andy, interesting stuff, thanks for your comments! But I have another question! How would the last half of the prop see air? As in a local bubble or entrained air? Surely for that to happen the pitch of the blades in that area would have to be less than the advance of the prop thru the water. Implying that the first half of the prop is doing all the work and driving the boat forward, but the leading half has less pitch, so how can the higher pitch portion of the prop move thru the water faster than its local pitch to create the air bubble?

Surely a prop creates thrust by accelerating a volume of water backwards. The amount of thrust would be dependent on how much water is accelerated, and how much the water is accelerated. The pitch progression is what would produce that acceleration, on an efficient prop the water meeting the LE would be met by a section of the blade that has similar pitch the actual advance or effective pitch, so wouldnt disturb the water greatly, and as the prop moves thru the water encountering higher and higher pitch sections of the prop the water would be accelerated backwards to create thrust. Surely, on a prop that isnt 'cavitating' on launch, there will always be positive water pressure on the working face unless a section of prop actually reduces in pitch, or is pitched so abruptly that the water cannot follow the blade profile?

Ian.

Ian,

The progression is needed for one purpose. To maintain blade contact with the water. The prop is a screw. But the water is not solid. When the LE penetrates the surface it screws itself forward according to the pitch of that LE. However, because the water is not solid it gets forced rearward by the initial contact of that LE. So, if the first 20% of the blade forces the water it just contacted rearward, then then next 20% of the blade must have a little more pitch to maintain contact with the water that is moving rearward. The heavier, more high drag hulls require more progression because the water is pushed back faster. Just like spinning your wheels in the dirt! Also the closer the prop is to the surface the more that progression is needed, because the water at the surface offers little resistance. A long prop that runs deep will require less progression because the water is more "solid" down deep.

I ran 114 mph with the Twin 84 using stock full blade 2170's. The progression of those props is no more than 10%, but since I used them at the full 70 mm length they still hooked up and pushed the boat well. If I had cut them to 60mm I would have had to add cup to get the same 114 mph speed.

In conclusion, I only view the prop as the screw that it is. A screw turning into steel does NOT have to accelerate steel backwards to create thrust in order to move itself forward. Nor does a propeller. It only needs something to push against. I this case water. Again because the water tries to move "out of the way" rearward) the pitch of the blade must ever increase to maintain contact with that small mass of water that is moving in the opposite direction (rearward).

Andy

P.S. Ian, I will actually agree that the rearward moving water can be explained with the Mass X Velocity = Thrust equation. The Mass of water is a constant according to the blade area of the prop. So in order to get more thrust (force to push the boat), water must be accelerated to a certain Velocity. This final Velocity becomes the TE pitch times the RPM if the prop is progressed properly. The heavier and more drag the hull, the more the final water Velocity must be. This Velocity of the water is initiated by the LE contact according to the resistance of the hull. The more resistance, the faster the water moves rearward and the more progression of the blade that will be needed to continue contact with the moving water.

So, an LE of 4.0" and a TE of 6.0" @ 28,000 rpm would net out a boat speed of 106 mph( 4.0" X 28K / 1057) The final water Velocity off the TE would be 6.0" X 28K / 1057 = 160 mph.

So in fact the water would move rearward in relation to the boat at 160 mph minus 106 mph = 54 mph.

You make it seam so simple when you explain it. That is the mark of a true master of his trade.

Thanks for sharing your insight it is very help full to many.

David

 

[Ian Inverarity]

Ian,

The progression is needed for one purpose. To maintain blade contact with the water. The prop is a screw. But the water is not solid. When the LE penetrates the surface it screws itself forward according to the pitch of that LE. However, because the water is not solid it gets forced rearward by the initial contact of that LE. So, if the first 20% of the blade forces the water it just contacted rearward, then then next 20% of the blade must have a little more pitch to maintain contact with the water that is moving rearward. The heavier, more high drag hulls require more progression because the water is pushed back faster. Just like spinning your wheels in the dirt! Also the closer the prop is to the surface the more that progression is needed, because the water at the surface offers little resistance. A long prop that runs deep will require less progression because the water is more "solid" down deep.

I ran 114 mph with the Twin 84 using stock full blade 2170's. The progression of those props is no more than 10%, but since I used them at the full 70 mm length they still hooked up and pushed the boat well. If I had cut them to 60mm I would have had to add cup to get the same 114 mph speed.

In conclusion, I only view the prop as the screw that it is. A screw turning into steel does NOT have to accelerate steel backwards to create thrust in order to move itself forward. Nor does a propeller. It only needs something to push against. I this case water. Again because the water tries to move "out of the way" rearward) the pitch of the blade must ever increase to maintain contact with that small mass of water that is moving in the opposite direction (rearward).

Andy

P.S. Ian, I will actually agree that the rearward moving water can be explained with the Mass X Velocity = Thrust equation. The Mass of water is a constant according to the blade area of the prop. So in order to get more thrust (force to push the boat), water must be accelerated to a certain Velocity. This final Velocity becomes the TE pitch times the RPM if the prop is progressed properly. The heavier and more drag the hull, the more the final water Velocity must be. This Velocity of the water is initiated by the LE contact according to the resistance of the hull. The more resistance, the faster the water moves rearward and the more progression of the blade that will be needed to continue contact with the moving water.

So, an LE of 4.0" and a TE of 6.0" @ 28,000 rpm would net out a boat speed of 106 mph( 4.0" X 28K / 1057) The final water Velocity off the TE would be 6.0" X 28K / 1057 = 160 mph.

So in fact the water would move rearward in relation to the boat at 160 mph minus 106 mph = 54 mph.

Andy,

Thanks for taking the time to explain your thoughts on the workings of pitch progression! I am having trouble with some points tho.

In terms of the analogy of a screw into metal, the screw does have constant pitch, or of course it would bind up! But also if the screw had only one turn of thread it would pull itself into the steel with the same thrust (actually more as less torque would be wasted in friction). On the other hand, cut away most of a prop but the LE (which is suggested screws itself into the water) and apart from the obvious structural problems, the prop wouldnt screw itself thru water at the same speed. From the above I would think you would suggest that would be because the prop would not be contacting the water moving back from LE contact?

I wish to understand the mechanism by which water would move away from the working face of the blade after initial contact with the LE. Surely to move away from the working face of the blade which is increasing in pitch means the water must actually be accelerating away from the prop? What makes it accelerate after it is no longer in contact with the blade? What makes it accelerate in response to the drag load of the boat, ie more acceleration with more drag load?

Looking at the example raised of the full blade stock 2170's running 114mph and 2170's cut down to 60mm. If the blade chord of the 2170 is reduced as the diameter is reduced then the total progression of the cut down prop is reduced. But the rate of change of pitch on the prop remains the same, that is the pitch change from one 5 degrees of measurement to the next 5 degrees stays the same, as this hasnt been changed by cutting away blade area. So on the same boat making the same drag load surely the water would move away from the blades at the same rate? So why would the rate of pitch increase on the full blade 2170 be adequate, but inadequate on the smaller blade where the rate of pitch increase is still the same? Why would the water move away from the working face of the smaller blade faster? Surely the smaller blade needs to have its pitch increased because it is moving less mass of water, so needs to accelerate that smaller mass a greater amount to create the same thrust?

I hope my questions are not taken as an attack, I certainly dont mean them to be taken that way!

Ian.