Prop Indexing

[Derret]

Anyone have any experience or thoughts to relate regarding indexing (two blade) props to a piston @ TDC- or some point of rotation of the crankshaft on its power stroke phase?

Thanks-

Derret

 

[Joe Warren]

How would you counter the Shaft Wind up? Pipes, Head clearence, Boat set up, correct operating water temp, Will yield more results.... B)

 

[Tim_Duggan]

How would you counter the Shaft Wind up? Pipes, Head clearence, Boat set up, correct operating water temp, Will yield more results.... B)

Not disagreeing with you at all Joe, but the shaft will only wind up so much, and to the same amount every time unless the shaft turns into a pretzel, so offsetting from TDC by the correct angle would pretty much take care of the shaft wind-up aspect. Now finding that amount of offset would be the really tricky part...... and then - was it even worth the effort to find it?

I know of one well respected boater who swears by indexing his props. I won't say who - I'll leave that up to him if he wishes to comment.

 

[Charles Perdue]

I am just curious as to how much an engine would actually speed up on the power stroke part of an engine revolution and slow down on the compression part of the same revolution at say 30,000 RPM or 500 times a second. :unsure:

Charles

 

[Chris Wood]

marty davis and stu barr both do the prop indexing

i have tried it.. i seen absolutly no difference.. but that is me.. i know they swear by it.

i see and understand why they do it. one thing that from chatting with stu he has one blade with a little more cup pitch what ever you want to call it than the other.. that one is the blade he indexes..

that's about all i know on the subject.

chris

 

[Joe Warren]

How do you measure the Performance difference....... & what are you going to allow for shaft Wind up 15 Degrees 30 45 90??? & If wind up is not considered it is Not indexed.........it is a Guesstimate. Is it better to began the power stroke with the blade in the water or approaching the entry of the water? I know only very few (5 or less people) that have boats this critical....... Carbs, pipe, Boat set up,head clearence,head bowl volume, prop cup & nitro percentage increases are area`s for impovement. p.s some mfgers shafts wind up more than others....... if indexing was ever a factor???? Maybe when the flex shafts were HARD Shafts & you did not have all of the variables of tha flex shaft?? ...... Someone please let me know If the performance diff is measurable

 

[Chris Wood]

and to add to what joe said.. how does it work if the back end of the boat blows out of the water? does it find it's spot back to where it would have entered the water if it didn't blow out?

this is a good conversation.

chris

 

[Lennard Cuenco]

hah!

i agree with Joe here, seems like obfuscation of more important things at work...

to add fuel to the proverbial fire, let's not forget that the length of your flexshaft will also add another variable, not to mention the load differential at different rpms will vary length of the shaft AND "windup" amount.....

lolwut?..come on ...it's a toyboat fer gawds sake...

 

[Derret]

My three cents worth- I've been in boating (both with a long term business & as my hobby) & have seen & done a lot in this neat hobby.

My thinking has always been to try things- for every good idea we get, there has to be hundreds(?) that are just not useful. I have boxes full of stuff like that in my rafters in the shop.

I do know that when I have something working (a winner) I don't mess with or change anything on it till it usually (always?) blows up or breaks. Then I got to start again to get things back in tune.

I had an 3.5 hydro (Hughey) in the early days that was like that. (Held the NAMBA SAW record for three years).

Any real difference in indexing the prop? Can't truely say.....

But...I do know the boat tested better after I used the same setup drill every time I ran the boat...

I know I did get real close to that boat when it ran fast. Almost like it was happy with me on the day?

Maybe I just tricked my thinking it was better?

I believe in perfect practice to be perfect & this seems to lead in the direction of doing things the same (like indexing).

Thanks-

Derret

 

[Lennard Cuenco]

My three cents worth- I've been in boating (both with a long term business & as my hobby) & have seen & done a lot in this neat hobby.

My thinking has always been to try things- for every good idea we get, there has to be hundreds(?) that are just not useful. I have boxes full of stuff like that in my rafters in the shop.

I do know that when I have something working (a winner) I don't mess with or change anything on it till it usually (always?) blows up or breaks. Then I got to start again to get things back in tune.

I had an 3.5 hydro (Hughey) in the early days that was like that. (Held the NAMBA SAW record for three years).

Any real difference in indexing the prop? Can't truely say.....

But...I do know the boat tested better after I used the same setup drill every time I ran the boat...

I know I did get real close to that boat when it ran fast. Almost like it was happy with me on the day?

Maybe I just tricked my thinking it was better?

I believe in perfect practice to be perfect & this seems to lead in the direction of doing things the same (like indexing).

Thanks-

Derret

Derret,

I agree with repeating setup techniques that work over and over...I do the same...

there are many examples in life/this hobby where doing things that have worked in the past will work in the present...

bottomline:

methods that bring value that are measurable...you should continue to do...we can all agree with that...

when you are able to measure the value that "indexing your props" brings...please define it here so we can understand what you did and how it made your situation better.

thanx,

Len

btw derret, if you still have that 7.5 that you were running with me and Alfred a few years back, I'll take it if ur done with it

you talk to gonsel lately?

 

[Marty Davis]

How do you measure the Performance difference....... & what are you going to allow for shaft Wind up 15 Degrees 30 45 90??? & If wind up is not considered it is Not indexed.........it is a Guesstimate. Is it better to began the power stroke with the blade in the water or approaching the entry of the water? I know only very few (5 or less people) that have boats this critical....... Carbs, pipe, Boat set up,head clearence,head bowl volume, prop cup & nitro percentage increases are area`s for impovement. p.s some mfgers shafts wind up more than others....... if indexing was ever a factor???? Maybe when the flex shafts were HARD Shafts & you did not have all of the variables of tha flex shaft?? ...... Someone please let me know If the performance diff is measurable

Joe:

Measure your speed with the prop on the drive dog indexed and then rotate 180 degrees and check the speed. B)

AND, I agree totally with you about boat setup, etc, etc, etc. MUCH more important than prop indexing.

 

[Ron Zaker Jr]

How do you measure the Performance difference....... & what are you going to allow for shaft Wind up 15 Degrees 30 45 90??? & If wind up is not considered it is Not indexed.........it is a Guesstimate. Is it better to began the power stroke with the blade in the water or approaching the entry of the water? I know only very few (5 or less people) that have boats this critical....... Carbs, pipe, Boat set up,head clearence,head bowl volume, prop cup & nitro percentage increases are area`s for impovement. p.s some mfgers shafts wind up more than others....... if indexing was ever a factor???? Maybe when the flex shafts were HARD Shafts & you did not have all of the variables of tha flex shaft?? ...... Someone please let me know If the performance diff is measurable

Joe:

Measure your speed with the prop on the drive dog indexed and then rotate 180 degrees and check the speed.

AND, I agree totally with you about boat setup, etc, etc, etc. MUCH more important than prop indexing.

Indexing MATTERS

 

[shoboat]

Ron,

I am not so sure about that. I can tell you from a ton of testing that stagger or

two different pitches or cups is not faster. I think the indexing with a hard shaft

may help, but I am not so sure with a flex shaft. Ron do you care to share any of

your test results and how you go about setting it up exactly? We went 103 MPH without

indexing, so I know you can go fast without doing it also. Maybe we just didn't set it

up correctly? There are a lot of different ways to go faster, but I think propeller

work will give you the best results out there, just my opinion.

If it works for you we must be doing something wrong.

Thanks,

Mark Sholund

Props-4-U

 

[Buckshot]

I index also.



B

 

[Ron Olson]

I watched over Mark's shoulder at a race in Fort Wayne many moon ago while he was playing with his then almost new prop pitch guage. Just for laughs he threw an Octura X-440/3 prop on it. Come ot find out, all 3 blades had a slightly different pitch. Now, if you could put the highest pitched prop on where it could hit the water on the downstroke, in theory it should push the boat a hair faster.

Next, from Marty's old site I read where you lose 500 RPM on the upstroke so that would be where you'd want the lower pitched blade at.

 

[mark voorhies]

With a prop spinning 25000 RPM, that has one blade hitting the water 416 times per second. To gain anything with prop indexing,

it must have to do with better load on motor on power stroke, as a constant, with particular pipe and prop combo?

 

[HTV Boats]

If you look at a 360 degree rotation the maximum power in the stroke is somewhere between 10 degree after top dead center to when the exhaust port opens. A small window and the rest of the rotation is flywheel momentum. A propeller blade also has some point in the rotation through the water that it achieves it's greatest efficiency. Its only in the water 180 degrees in general. So trying to line those two point up seems logical. If you systematically change say 15 degrees at a time you might find the offset for cable winding. On our outboards with short cables and little flex and square drives you pick a spot easier. Also in a two blade prop one blade is going to be different than the other. Just can't match them that perfect, especially going through the water 400+ times a second. Is all this too much grasping at straws. More precision than you can measure and make changes? Well look at how much your engine clearances mean. How many guys use a setup board and adjust sponsons to the thousanth. More precision seems to go with the best of the best. So why not try to maximise prop efficiency. Take two props time 20 laps on each. Rotate them just the 180 degrees on the drive dog and time and record laps again. I will bet one prop will be different blade to blade. We all are looking for that edge over the competition and a lot of it becomes just mental health but systematic testing and measuring some format will be the key that you improve with.

Mic

 

[Marty Davis]

I watched over Mark's shoulder at a race in Fort Wayne many moon ago while he was playing with his then almost new prop pitch guage. Just for laughs he threw an Octura X-440/3 prop on it. Come ot find out, all 3 blades had a slightly different pitch. Now, if you could put the highest pitched prop on where it could hit the water on the downstroke, in theory it should push the boat a hair faster.

Next, from Marty's old site I read where you lose 500 RPM on the upstroke so that would be where you'd want the lower pitched blade at.

That rpm loss was on only one engine that was being tested by Brian Callahan and his people at Queens University Belfast. He also did some photography of the explosion of the charge using some sophisticated instrumentation. The loss in rpm was significant since the rpm's were in the 33k area and a loss of 500 rpm is huge on each stroke.

I would say this....

IF your boat is not set up almost perfectly with sponson angles within .1 degree, a great prop, perfect pipe/engine combination, etc, etc. then prop indexing is not something that you should work with. It will not be something that will make a poor boat a good boat.

An example of this indexing that I have stated for MANY years is a true story:

I had a Beardslee prop that was a cut down 2.8 Octura. (Back then I was doing some SAW stuff). It had rounded tips and was cut down a bunch. I used it on my 40 SAW boat (20 Crapshooter with 45 K&B on mini-pipe). I would run 80-85 mph in 1979. I let Fred McBroom run the prop one day and he ran his boat up on a big boat launch ramp. Bent the prop up. His brother, Hilton, a terrific mechanic and builder said he could bend it back and make it perfect. He did, only thing one blade was substantially different in pitch. I ran the prop and it worked just OK. Put it back in my box and one day I ran it again, and it was awesome. Ran 89.9 mph. Couldn't figure out what had just happened. Started thinking about it and running it again and again. It ran different sometimes at 80 and sometimes at 89. Decided one day that nothing had changed and MAYBE I should put it on the drive dog one way and test it and then reverse it 180 degrees. THAT WAS IT. From that day on I started working with indexing props. True story and one that amazed me in its simplicity and result.

Stated this several times with many including Andy Brown saying I was nuts. That was true, but the indexing was also true.

I currently run props that are the same pitch and index blades so that the pitch is going in the water at TDC. I will someday re-visit the different pitch prop indexing. My best heat race prop (a 1450 with different pitch) is still my favorite heat race prop on my Intrepid. I made a pair of duplicators that are available from Frank Bonanno that are for each of the two different blades. With the new Cougar, the boat is so much lighter that I runn different props on it that have much more pitch and have not explored staggered pitch. Probably won't get back to that anytime soon as I have so many things that I want to test that i just don't have time. Need a few guys to test stuff for me I guess.

You noticed the short and sweet answer that Ron Zaker, Jr gave on this topic. I taught him about this a long time ago and he has beaten me consistently since. That is not why, but only part of the story.

Take this an use it if you wish, and if not, throw it in the trash can.

 

[Marty Davis]

If you look at a 360 degree rotation the maximum power in the stroke is somewhere between 10 degree after top dead center to when the exhaust port opens. A small window and the rest of the rotation is flywheel momentum. A propeller blade also has some point in the rotation through the water that it achieves it's greatest efficiency. Its only in the water 180 degrees in general. So trying to line those two point up seems logical. If you systematically change say 15 degrees at a time you might find the offset for cable winding. On our outboards with short cables and little flex and square drives you pick a spot easier. Also in a two blade prop one blade is going to be different than the other. Just can't match them that perfect, especially going through the water 400+ times a second. Is all this too much grasping at straws. More precision than you can measure and make changes? Well look at how much your engine clearances mean. How many guys use a setup board and adjust sponsons to the thousanth. More precision seems to go with the best of the best. So why not try to maximise prop efficiency. Take two props time 20 laps on each. Rotate them just the 180 degrees on the drive dog and time and record laps again. I will bet one prop will be different blade to blade. We all are looking for that edge over the competition and a lot of it becomes just mental health but systematic testing and measuring some format will be the key that you improve with.

Mic

Mic:

Very good analysis.....

This is the second posting that I have seen you write in the past couple weeks that have very analytical testing approaches. You are on a great path with this type analysis.

 

[Steve Anderson]

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