Prop problem

[lgaytan]

I don't have documented information but I saw in a youtube video that aluminum props loose 25% of pitch due to deformation, is tha true? If that is like that it seems a big difference in efficiency I guess, but well as explained before I will stick with my old prop just rehubbed, I think it worked good until now, after all being the hub a sacrificial component this seems to be a normal maintenance procedure.

 

[Chris1956]

Not to discredit Utube, but aluminum props do not loose anywhere near 25% of their pitch. That would turn a 21P aluminum prop into a 16P prop.

I have always heard that aluminum props flex a bit under load but have never witnessed it.

 

[tphoyt]

For what it’s worth I think you have made a good decision getting your prop fixed. You can go into a rabbit hole trying to gain an extra bit of speed. Unless your way way off on pitch and your likely not it’s not going to make a big difference unless your trying to win a race. Get one of those cheap tacks that wrap around the plug wire someday and see what your rpms are at wot and go from there if you need to. I can’t remember what those dam tack are called at the moment. Brain fart.

 

[lgaytan]

I have a tinytach in other outboard, I will try it in this one, only downside is that cables are too short so I need help from somebody to see the readings or drive, anyways theres alwas a way to do things.

 

[airshot]

I don't have documented information but I saw in a youtube video that aluminum props loose 25% of pitch due to deformation, is tha true? If that is like that it seems a big difference in efficiency I guess, but well as explained before I will stick with my old prop just rehubbed, I think it worked good until now, after all being the hub a sacrificial component this seems to be a normal maintenance procedure.

If they flexed 25%, the blades would break off.....don't believe anything on youtube...!!

 

[lgaytan]

Prop is back looks good I think was good decision to send it to a repair shop, they changed the hub, fixed dings with welding and balanced it, will try It soon.

 

[jimmbo]

I have hit many things, but only when I had a SS prop on did I end up with a Bent Propshaft

 

[dingbat]

If they flexed 25%, the blades would break off.....don't believe anything on youtube...!!

Suggest you read up on the “modules of elasticity”, “yield strength” and “Poisson's ratio” in particular.

Didn’t do the math, but 25% deformation of aluminum under load doesn’t sound outlandish.

Pretty easy to model with a program like SolidWorks or any of the other FEA programs on the market

 

[flashback]

Prop is back looks good I think was good decision to send it to a repair shop, they changed the hub, fixed dings with welding and balanced it, will try It soon.

Sounds like you found a good shop!

 

[jimmbo]

If there is any flexing of the Blade it is likely in the Range of 1/100" on an Aluminiun Prop.
That bit about Blade Flex has sold Hundreds of Thousands of SS Props

 

[airshot]

Suggest you read up on the “modules of elasticity”, “yield strength” and “Poisson's ratio” in particular.

Didn’t do the math, but 25% deformation of aluminum under load doesn’t sound outlandish.

Pretty easy to model with a program like SolidWorks or any of the other FEA programs on the market

Built dies for diecast aluminum and for investment castings for over 30 years, especially propellers for a local casting company. I can assure you the a cast aluminium m prop will not allow a 25% flex without breaking off....no where near 25 or even 20%. Watched numerous tests over the years, most would allow less than 10% before fracture. I came from hands on days, long before some computer program said differently. We often celebrated when we could prove the computer wrong !

 

[Chris1956]

Remember the internet is still insisting that perpetual motion machines are real. They want the clicks, likes and subscribes, for the $$.

Actually, I think you can find most any alternate fact on the internet, without looking too hard. (BTW- alternate facts are lies.)

 

[cyclops222]

S S props bend at WOT !!
As do Titanium Props.
Everything bends at FULL LOAD.

Worry about the EFFICIENCY of any prop !! That can easily waste 25 % of WOT power.
YAAAWWNN

 

[lgaytan]

That 25% pitch lose information came from a prop shop YouTube channel this guy is trying to convince to buy only OEM SS props from his shop, although 25% seemed not feasible I don't think anybody fun the industry will fabricate those knowing about that loss and I don't think anybody would buy them if that was true, how ever I do have consistently read and seen that SS are more efficient to some point, and when I brought this topic was too take a decision rather to fix my SS prop or buy a new aluminum one, so the decision was easy for me once I found the right shop.
Now the question would buy if I had to buy a new propeller no matter what an OEM aluminum or a Chinese SS would buy my choice?

 

[Texasmark]

If they flexed 25%, the blades would break off.....don't believe anything on youtube...!!

Since they are made of "cast" aluminum, cast anything metal and surely some other materials oppose flexing. I agree with "airshot" and figure the percentage at a single digit value. On the other comment by Cyclops222.........Prove it!

 

[cyclops222]

Flexing is totally different from bent.
Any body have ...Efficiency charts .....of different companies and their props ? Post them.

 

[dingbat]

Built dies for diecast aluminum and for investment castings for over 30 years, especially propellers for a local casting company. I can assure you the a cast aluminium m prop will not allow a 25% flex without breaking off....no where near 25 or even 20%. Watched numerous tests over the years, most would allow less than 10% before fracture. I came from hands on days, long before some computer program said differently. We often celebrated when we could prove the computer wrong !

Structural/design engineer by education.
Metals/alloys properties analysis for a living the past 40+ years.

What aluminum alloy are you considering?

 

[jimmbo]

If the Blades Flex, the Magnitude is very small, in the range of Fractions of a Millimeter. Put a Pair of Vise Grips on an Aluminium Blade, and see how much Flex you get...

 

[airshot]

Structural/design engineer by education.
Metals/alloys properties analysis for a living the past 40+ years.

What aluminum alloy are you considering?

Whatever they are making props out of today.

 

[cyclops222]

Yamaha had bad O B exhaust casting inside of motors. They were using SCRAP ALUMINUM.
No company posts they are making bad products. Web sites and posting people tell what is happening.