Pushing 100 RoadRunner Twin 90s VACs

[thomaselkins]

Some dam good stuff has come from this posting, learning curve high.

 

[Marty Davis]

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...

Terry:

I agree on heat treating. I bought a heat treating furnace and electonic control MANY years ago and it gets a lot of use.

Look at the tongue area of Terry's prop. It is cut off at about a 90 degree angle to the hub. Lots of leading edge pitch removed. Even better look at the current Mercury Marine props and almost all of the leading edge pitch is removed. They must know something

 

[shoboat]

Marty,

If I had the time to type out a book on propellers here I would.

I have 32 orders on my bench right now and I am adding aprox.

3 to 5 more orders a day right now. I work two jobs about 80 hours

a week right now, just no time right now to type about propellers.

If anyone wants to learn more about propellers: pitch,cup,rake,etc.

Like I said I am available to talk on the phone. I would hate to upset

anyone on this forum about misunderstood terminalogy on propellers.

Mercury Marine has a great book on propeller basics and most of it applies

to our boats just in a scaled down manner. If people want to go faster, think

about pipe length and less exhaust timing in their motors. RPM = SPEED

and more leading edge pitch will get you faster if you can pull it with good RPM.

I am more than happy to help any and all that want to learn more about propellers.

Back To The Shop,

Mark Sholund

231.590.3023

 

[Wes James]

Mark-

Your attitude and willingness to help anyone who wants to learn shows you're a really world-class guy!

Wes

 

[shoboat]

Wes,

I think most that know me will tell you that I am always happy to help people out in this hobby.

I have done it for over 20 years now and it is something I am very passionate about, you can ask

my second wife. The first one couldn't handle the passion.

Thanks For Your Reply,

Mark Sholund

 

[Rick Doane]

Dang it...................I just lost the page I was typing so I will try to remember.

I believe where all the confusion is the term cup. Terry K. hit on it by stating he measures many different points along the blade. I do the same to get the average pitch value and use this in the following equation. RPM x PITCH / 63,360 x 60 (0% slippage) = MPH. When I tell customers that their pitch is not what is on the bag they get confused. One should not use the cup pitch to calculate MPH.

I want to say that no one here and certainly not me is trying to discredit anyone. All of us approach this hobby in different ways. However, the nomenclature and physics of our props have not changed. I would like to see more consistancy in our definitions.

By the way.......TK...Will you describe the numbers on your props?

Rick

 

[Terry Keeley]

By the way.......TK...Will you describe the numbers on your props?

Rick

Sure, number near drive dog is the diameter in mm, other 3 are all pitch, if you look at my post you'll figure out which is which.

We've found a good formula (again, from Andy years ago) is:

MPH = (Pitch (in) x Rpm) / 1057

You must use the LE pitch and the hull has to run "clean".

BTW, that blade shpe came from Marty years ago and looks like the 1400 blade here:

http://rcboat.com/prop.htm

 

[Terry Keeley]

Terry:

I agree on heat treating. I bought a heat treating furnace and electonic control MANY years ago and it gets a lot of use.

Yup! Was running 1662's on a 60 boat years ago and it's started acting goofy, went nuts trying to figure it out. Got home and put the prop on the pitch gauge and one blade was way out, hard to see just eyeballing it tho.

That was the last "soft" prop I ran.

Now they're kinda like my carbon sponson booms, they're either straight or they're broken.

BTW, Gary Preusse's "blow torch and kitchen oven" method works well too.

 

[Rick Doane]

By the way.......TK...Will you describe the numbers on your props?

Rick

Sure, number near drive dog is the diameter in mm, other 3 are all pitch, if you look at my post you'll figure out which is which.

We've found a good formula (again, from Andy years ago) is:

MPH = (Pitch (in) x Rpm) / 1057

You must use the LE pitch and the hull has to run "clean".

BTW, that blade shpe came from Marty years ago and looks like the 1400 blade here:

http://rcboat.com/prop.htm

Terry :

Beautiful props. Thank you for the explaination. The 1057 number is 63,630/60. Acutally 1056 less extended decimal places. Still 0 slippage. I must try the blade shape. Do you have any data for this shape in a heat racing configuration?

Regards..........Rick

 

[Terry Keeley]

Beautiful props. Thank you for the explaination. The 1057 number is 63,630/60. Acutally 1056 less extended decimal places. Still 0 slippage. I must try the blade shape. Do you have any data for this shape in a heat racing configuration?

Regards..........Rick

Thanks!

This shape works very well for hydros on 16 series props, add just a bit of cup to the tips to keep it hooked up "in the marbles".

 

[Rick Doane]

Beautiful props. Thank you for the explaination. The 1057 number is 63,630/60. Acutally 1056 less extended decimal places. Still 0 slippage. I must try the blade shape. Do you have any data for this shape in a heat racing configuration?

Regards..........Rick

Thanks!

This shape works very well for hydros on 16 series props, add just a bit of cup to the tips to keep it hooked up "in the marbles".

HOOOOOOOOO WEEEEEEEE!!!! Just what I'm looking for . Let's go racing boys.

 

[BigChuck]

Rick

This is what the twin will run like on those props in a 1667. Joe and Jose have seem them before. Most thought they were to much load. I call them the "BIG" props.

Oh yes they work. :lol:

 

[Piston1]

Charles, or should I say "Superchicken" bring them over. You have a place to stay here in Knoxville. Let's go testing.

"Piston1"

 

[Piston1]

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...

Terry I see no cupping in those props. Nice, very nice!!!

 

[Michael Costanzo]

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...

hi terry, who is franko? and how does the average joe get his props heat treated?thanks,mike.

 

[Joe Warren]

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.....

This is Exactly Correct.... & V cutting your T.E. Hydro & Mono props out of the center of the hub makes the prop think it has more Rake another feature we would like to see in some newier designed props. I see Marty`s props have material removed all the way across the Trailing Edge. This effectively makes Rake too.... Has anyone seen the Sholund VX 467 props? It has all of these features. That paticular VX467 prop will rum more RPM & speed than ever before...... Only thing faster is a VX470!! :blink: :huh: B) I have recently received some 1662 5.5 5.7 cup from Mark that have a tiny barr cut.... Plus the center of the slight barr cut has a slight V cut. or a (swirl turbo) cut... I found the V cut helps the boat launch bigger props & turn great Rpm. But dont kill Lift as much & drop the back of the boat like a a Barr cut.. This is just my experience....... B)

 

[Joe Warren]

Charles, WE are testing TWINS in Huntsville this WEEKEND. Strap it to you back & BIKE IT ON OVER........ :blink: B)

 

[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...

Terry I see no cupping in those props. Nice, very nice!!!

There actually is a bit, you can just see the bending in the shiny spot on the nearest prop, you need a pitch gauge to really tell tho.

Actually should have used a bigger ball to get it smoother...

Lots of cup (or TE pitch or "kick" or whatever) in my mind is just a bandaid that robs power, usually you can go faster with more LE pitch . High pitch props wanna come out of the water w/o a little cup tho.

 

[Terry Keeley]

hi terry, who is franko? and how does the average joe get his props heat treated?thanks,mike.

That's fellow Crazy Canuck Frank Orlic, he's on here. His gauge is compact and uses a dial indicator to measure pitch.

Here's proper heat-treat info:

http://www.brushwell...AT0015_0295.pdf

As far as I know Octura uses 20C and to do it proper you need a kiln or furnace that'll go to 1500F.

Gary Preusse's "ghetto method"

is to heat the prop to a dull red color in a dark room (you can see it better) and water quench. Then stick it in the kitchen oven as high as it'll go for 3 hrs. or just run the self clean cycle if it has it. You'll get real close this way.

If you heat and quench first it'll be soft and easier to work, then put it in the oven to get a better finish.

Another benefit of hardening is you can thin the blades a bunch and they won't bend, the ones in the pic are about 1/2 of their stock thickness.

 

[Marty Davis]

hi terry, who is franko? and how does the average joe get his props heat treated?thanks,mike.

That's fellow Crazy Canuck Frank Orlic, he's on here. His gauge is compact and uses a dial indicator to measure pitch.

Here's proper heat-treat info:

http://www.brushwell...AT0015_0295.pdf

As far as I know Octura uses 20C and to do it proper you need a kiln or furnace that'll go to 1500F.

Gary Preusse's "ghetto method"

is to heat the prop to a dull red color in a dark room (you can see it better) and water quench. Then stick it in the kitchen oven as high as it'll go for 3 hrs. or just run the self clean cycle if it has it. You'll get real close this way.

If you heat and quench first it'll be soft and easier to work, then put it in the oven to get a better finish.

Another benefit of hardening is you can thin the blades a bunch and they won't bend, the ones in the pic are about 1/2 of their stock thickness.

Terry:

What is your exact heat treat cycle and anneal cycle for our props?

Which of the alloys do you consider our props on your tech sheet?

Also, do you bag the prop in a stainless package and put in a kitchen match to keep down the tarnish that comes with the heat?

I have been using 1200 for 1 hour and water quench to anneal.

Then, 600 for 1 hour and air cool to harden.

I would be interested in what you are doing and if you are having any fracturing. You can get a prop TOO HARD and then it is easy to snap. I have found that this recipe works well for heat race props.