Propeller Blade Thicknesses.....

[ThrottleUp Props]

Great points Rich! This is something we see with Cleavers.....I guess it is becasue they can have a longer span (more metal on the trailing edge). It is of great importance to consider the weight and the HP of the boat when determining the blade thickness or the recommendations we make. Some adjustments are permanent and some are only temporary as Rich has described! Another great example would be pitch changes, which are not always permanent.

Julie

 

[BRAD SCHOENWALD]

Interesting Stuff. This is/has all been in lesson plan four of our performance boat school. We have found numerous props with cracked blades on the pre checks of the students boats as well as boats with the wrong prop.

Keep up the great work!

 

[MattBMiller]

Sorry to hear you have had another prop issue, Matt. If it is a smaller sized crack, than a repair may be in order. But, you need to look into the root cause of the blade failure. Here is a very important thing to consider.

High Rake, Round Ear props were not designed to surface pierce. So for those of you installing shorties keep in mind that this may lead to or be directly causing your blade failures. Your asking a propeller to due something it was designed to do.

I mention this as you have now cracked labbed and stock props.

Julie

I tried a Hydromotive on my boat last year, but it just blew out at 2200 RPM's. Any suggestions on other props to try?

Thanks!

 

[ThrottleUp Props]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

Julie

 

[T2x]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

I bet you say that to all the boys...................



T2x

 

[MattBMiller]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

Julie

These are the only pics I have. Don't have a pic with the drive down. Propshaft CL is 2.5" below the bottom at neutral trim.

 

[ThrottleUp Props]

Eureka....good job Matt! You have just uncovered your problem with blade failures. So the good news is your boat is set up aggressively. The bad news is this is exactly what is causing your blade failures. You are surfacing a round ear, high rake propeller that was never designed to surface pierce. We have not even touched on the performance issues you are having. This is what semi-cleavers and full cleavers are for. So you have three options:

1) Switch to semi-cleavers
2) Space the drive down
3) So nothing and invest in props. You will need one on the boat, one in the mail and one on order. In other words tossing blades will be common place.

Sorry I don't have better news but at least you know the root cause of your blade failures.

Julie

 

[PARADOX]

Just love a Blond talking technical stuff.

Long ago, and far away, back and on Lake "X" we were drilling pin holes on the surfacing props, try to eliminate the T2X rounding/bending problems. The scheme actually worked a bit, allowing some stress and "gases" to escape releaving preasures at the tip.
I haven't seen any holes in the props for decades, but again, this was before the labbing era. Labbing back than meant putting a grinder or a drimmal to the edge and make them sharp as a rasor.

 

[Geronimo36]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

Julie

Julie, here's mine with the new setup. Sorry for the pic quality, I had the morning sun to deal with. It's hard to imagine they were 2" lower! I'm now measuring 5 1/4" propshaft depth at neutral position.

Your thoughts?

Thanks in Advance.

 

[Ratickle]

I tried a Hydromotive on my boat last year, but it just blew out at 2200 RPM's. Any suggestions on other props to try?

Thanks!

A four blade? That surprises me....


Should have finished reading before commenting.....


2.5 inches is high........

 

[ThrottleUp Props]

I bet you say that to all the boys...................



T2x

I cannot tell a lie.......I do!:biggrinjester:

Julie

 

[ThrottleUp Props]

Julie, here's mine with the new setup. Sorry for the pic quality, I had the morning sun to deal with. It's hard to imagine they were 2" lower! I'm now measuring 5 1/4" propshaft depth at neutral position.

Your thoughts?

Thanks in Advance.

At 5.25" below the hull your optimum propeller will be a 4B Propeller. It might be a tad to deep for a 5B propeller. However if you have modified motors the addition of a blade can assist at carrying the weight. Why don't you post your performance numbers and we can take a look at efficency.

Julie

 

[Geronimo36]

Will do Julie, thanks.

I may go testing this weekend...hopefully I don't blow it up.. lol

 

[Tomas Wallin]

GREAT THREAD JULIE!

What about my application?

I know I have asked you before but it won't hurt...

At what prop shaft height should you consider semi cleaver and cleaver props?

My prop shaft is at 3.15" below the bottom with a 10" notch and I would like to stick with 4bl props.

I'm going to try a std Bravo 28 and a std 30 next, with 825HP I had only 11% slip with a std Bravo 28 at 89mph - now I have some more boost and 870HP.

The two labbed ones I've got only gets me a lot of slip and no speed. The labbed Bravo 31 I tried last got me to 88.5mph with 24% slip and probably way to little bow lift since it chine walked like crazy. I will get some pics next time to see what it looks like at wot.

The props markings are Wood190 (29P) and FO1D127 (not completely sure about the "1" though. 15 1/4 X 31 R - blade thickness 0.135")

Will a Hydromotive do me any good theoretically? I assume the QIV-X would be my best bet with it's bow lift?

 

[KnotRight]

Hey Julie am I doing this right??

 

[KnotRight]

Oh yeah 1580 hp herrings 16.75 x 37.5,s
3.5 inch drive height. 46 Skater Turbines

 

[Geronimo36]

At 5.25" below the hull your optimum propeller will be a 4B Propeller. It might be a tad to deep for a 5B propeller. However if you have modified motors the addition of a blade can assist at carrying the weight. Why don't you post your performance numbers and we can take a look at efficency.

Julie

Julie, the verdict is in. The boat picked up 3 mph through out the entire RPM range. However, I'm still a little under propped spinning 5250-5300, I'd like to see 5400-5600 but I don't want to loose cruise speed by labbing..

Boat ran 87 mph!!!

Your thoughts?

 

[Padraig]

What about Cryogenic hardening a thinner blade. Weren't some racers doing that a few years back. Are there advandages or was it dropped because the benifit was not there?

 

[PARADOX]

Q: to July

Off the thickness issue we are going. but.

"X" dim? Deep "V" no step. 24 Deg. deadrise. The camera was pretty even and in line with the bottom of the hull.
Prop shaft center 5". Props are labbed with added cup for bow lift. Still looking for some hard to find additional speed. With the 28's and 32's pretty much same top end. (525's bravo XR, SM shorties)

Any thoughts?

 

[ThrottleUp Props]

GREAT THREAD JULIE!

What about my application?

I know I have asked you before but it won't hurt...

At what prop shaft height should you consider semi cleaver and cleaver props?

My prop shaft is at 3.15" below the bottom with a 10" notch and I would lika to stick to 4bl props.

I'm going to try a std Bravo 28 and a std 30 next, with 825HP I had only 11% slip with a std Bravo 28 at 89mph - now I have some more boost and 870HP.

The two labbed ones I've got only gets me a lot of slip and no speed. The labbed Bravo 31 I tried last got me to 88.5mph with 24% slip and probably way to little bow lift since it chine walked like crazy. I will get some pics next time to see what it looks like at wot.

The props markings are Wood190 (29P) and FO1D127 (not completely sure about the "1" though. 15 1/4 X 31 R - blade thickness 0.135")

Will a Hydromotive do me any good theoretically? I assume the QIV-X would be my best bet with it's bow lift?

Well with your prop shafts 3.15 below the hull you are marginal for being able to run them successfully with 4B props. I would try a Hydromotive P5-X I bet this propeller will perform pretty well for you. Labbed props are definately out with your new set-up. To much slip!~

Julie