Prop Pitch Measurement - WHERE is it Important to measure on blade??

[Darin Jordan]

I've been really getting into documenting all the props I currently have and trying to understand how the different pitches and cups and bends and back-cuts affect the performance of my boats.

One thing that has been puzzling me a bit is WHERE on the blades is it important to measure the pitch profile in order to get a real sense of how a prop is as far as overall and effective pitch??

Most of my props are for FE use, so they are under 50mm generally. On a 45x55, for example, I would measure in from the tip about 1/4" or so, and then about mid-blade. I often get wildly different "average" pitch readings this way, with the tips showing over 4" for 0 to .3750 step (in .0625" increments), and the mid-blade showing just over 3" for the same blade, over 0 to .4375" step.

Can someone please give me an idea on WHERE I should be focusing my measurements to get consistent comparisons from prop to prop, or otherwise highlight their methods and what I should be looking at?

I'd appreciate the input.

Thanks,

 

[dave roach]

Darin

Around 70% from the heal of the prop.

Dave Roach

 

[Terry Keeley]

 

[Mike Hughes]

Yep

70% That is where most of the water is coming off the blade doing the most work.

Miek

 

[Mark Leyde]

I am with ya Terry.

 

[Terry Keeley]

I am with ya Terry.

:lol:

Here's another one, define "cup". :blink:

 

[Darin Jordan]

I am with ya Terry.

:lol:

Here's another one, define "cup". :blink:

That one is easy... Here is a good read: http://www.hydrocompinc.com/knowledge/publications/PropellerCup.pdf

 

[Terry Keeley]

I am with ya Terry.

:lol:

Here's another one, define "cup". :blink:

That one is easy... Here is a good read: http://www.hydrocompinc.com/knowledge/publications/PropellerCup.pdf

Yup, that's how HE defines it alright! :lol:

 

[Darin Jordan]

Yup, that's how HE defines it alright! :lol:

Gotta be one in every thread on these fuelie sites...

 

[Terry Keeley]

Yup, that's how HE defines it alright! :lol:

Gotta be one in every thread on these fuelie sites...

Hey, I resemble that remark! :lol:

 

[Darin Jordan]

Hey, I resemble that remark! :lol:

Hahahahaha....

 

[BigChuck]

70 % coming of the prop...............OK.. So what is the water doing the rest of the time it is on the Blade.............?????

Food for thought. Most full size racing props are being milled 5 axis. Because of the precise measurement 70% is only part of what the props job is.

Ok..........you can continue with your thread.

 

[Tim_Duggan]

On a 45x55, for example, I would measure in from the tip about 1/4" or so, and then about mid-blade. I often get wildly different "average" pitch readings this way, with the tips showing over 4" for 0 to .3750 step (in .0625" increments), and the mid-blade showing just over 3" for the same blade, over 0 to .4375" step.

Darin,

Any chance you could tell me what the leading edge pitch is on the 42x55? I don't have one of those and am interested to know.

Thanks,

Tim.

 

[Chris Wood]

what about leading edge center of blade 70% mark and very trailing edge. oh and then the vary outter edge

i am not PROP guy.. i won't comment much about this as if i do i will get scalled by whom ever. so take this for what you want.

what works for one.. don't always work for the other... i have props that look like a meat clever worked on them.. they are my best props.. i would say bend on them. try it once you get something you like.. measure ALL OVER the prop.

I have done that.. copyed them and they still are not the same so all that goes out the window for ME.

i am going to the back row now.

chris

 

[aaron alberico]

Tim

i cant remember exact, but i do remember at 35000+rpm it is good for approx 3-4mph

over the 40x53,

i have one for my outboard...

regards Aaron

 

[Mike Larson]

Where's Mark?.... Andy?..... many more...... help us to understand. MD's RcBoat.com articles on props are floating around in ethernet, too......

I've been chopping up props for awhile, and learned a few things..... The gauge is just that, a gauge.... any gauge any maker....

Used for reference to an existing set of numbers known to improve.... maybe...... Chris hit on it, and it's almost impossible to duplicate a favorite, exactly. no matter.... close..... OK.

70% and a guess, at that, from the hub, for me. Documentation( microscopic number lowdown) as it progresses, maybe, if it's one that tested off the charts.....

Bag props are bad.... consistency out of the mold, almost is nominal, and i have theory on which side it released on usually.....

Bottom line, i've determined that no two will ever be the same, ever....... the gauge will drive you insane if you let it.....

Testing the weeks latest butcher, bend, cup, backcut, whatever, after knowledge of last weeks numbers and hopeful performance gain is all it's about.... well, that didnt help...... that did! Gauge and another experiment, or five, next week......the possibilities are infinite. Been around Chris, or Mike Z?...... the prop pliers, and gauge sit to the right of their chair, at the lake..... and they work them... every time.

Mark's one guy, that either has a serious database on props for each guy, each boat/motor/pipe/infinite, or just plain that good, to send his best guess across the country all the time...... i'd be nervous, beyond compare, but, i've never failed to see gain usually after he asks questions on the particular hull/motor/pipe, and prepares the prop accordingly..... pukin? send it back. I've never had to!

IMO, the cost for bag props is almost minimal, and, I make a trio of any given size for a new boat.... likes it, sags, likes it more..... quickly whittling down based on 70 from the hub on the one or two that showed promise..... upwards next week.... faster, maybe. Gaining the tools you need to know where a given prop is at for your boat, based on test session 900, and taking it up from there, currently has my attention, factly due to: A, my engines are getting old, and pulling what they did early just isnt there, B, I dont run the ultra high nitro content most men do, among all the other factors drive people nuts...... pipe, whatever....

No two boats anywhere the same.... ever.... too many variables to mention..... pile up some beryllium, so what if it's what, an 11 dollar prop?..... 15?.... if you gain..... dont you smile?....... Work 'em up.... you never know..... no butter on my popcorn, please. Mike

 

[Terry Keeley]

Get an Eagle Tree with RPM and GPS, use that information with your pitch gauge and you'll never look back.

I was turning lots of rpms and not going as fast as I should, now I'm starting to. h34r:

 

[Darin Jordan]

Get an Eagle Tree with RPM and GPS, use that information with your pitch gauge and you'll never look back.

Have all that... Just working to understand all the info I'm gathering...

 

[Grimracer]

Let us know when you get the tech paper done on this D ..



Grim

 

[Terry Keeley]

Get an Eagle Tree with RPM and GPS, use that information with your pitch gauge and you'll never look back.

Have all that... Just working to understand all the info I'm gathering...

K.

Take your speed and rpm from a couple of the graphs, measure the LE pitch of the prop at 70% out from the center of the hub (1st 1/3rd or so of the blade) and using the formula: mph = pitch x rpm / 1057 figure your slip.

Come back with some hard numbers and I'm sure you'll have lots of advise on what to do! :lol: