Propeller Blade Thicknesses.....

[ThrottleUp Props]

Hey Julie am I doing this right??

WOW.... nice KnotRight!

I am going to post a diagram for you all today. This will give all of you with Micromoeters something to measure by.


Julie

 

[Ratickle]

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

All right, now you really lost me.......


A labbed prop made specially for the boat is not the best?

 

[ThrottleUp Props]

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?

At what RPM is your peak HP produced? If you ran 5200 and your looking for 5600 (your range is too wide) Then you may not even be in the power band of the motor. If this is the case your currently getting a false sense of cruise speed and possibly lugging the motor.

Julie

 

[ThrottleUp Props]

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?

I have spoken with a few companies about this as well. It has been around a long time. Some say it works while other say it makes the propeller too brittle. It works well on fixed parts that experience little to no flex.

Julie

 

[ThrottleUp Props]

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 lookng for some hard to find additinal speed. With the 28's and 32's pretty much same top end. (525's bravo XR, SM shorties)

Any thoughts?
View attachment 31624

View attachment 31625

If you can post ALL of your data I can take a look. To be able to run 28P props and 32P props in the power band would surprise me.

Julie

 

[ThrottleUp Props]

All right, now you really lost me.......


A labbed prop made specially for the boat is not the best?

During the process of labbing a good amount of the cup is cut out. This is part of the reason why your RPM increases with a labbed propeller. However some boats just do not respond well to this modification and need the cup put back in. By doing so the RPM will come back down. Now one may not be achieving their RPM goals. So it is not always the answer.

Julie

 

[BradH]

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.

I've heard of a few fairly recent commercial propellers that a few holes have helped. Most of the time the propeller is overloaded and begins to cavitate on the back of the blade. Drill some holes and allow the bubble to fill, rather than collapse on the blade. Same thing that you experienced, just on a different scale. Simple solution for a complex problem.

Out of curiosity, when was this? Michigan wheel made some major changes to blade design in the mid 80s to combat this problem and I'm wondering how many manufacturers adopted these.

 

[ThrottleUp Props]

Lab Finishing propellers is typically more successful on progressive or aggressive hulls. Conventional Deep Vee hulls with no steps or notches, so not respond as well to labbed props.

Julie

 

[PARADOX]

I've heard of a few fairly recent commercial propellers that a few holes have helped. Most of the time the propeller is overloaded and begins to cavitate on the back of the blade. Drill some holes and allow the bubble to fill, rather than collapse on the blade. Same thing that you experienced, just on a different scale. Simple solution for a complex problem.

Out of curiosity, when was this? Michigan wheel made some major changes to blade design in the mid 80s to combat this problem and I'm wondering how many manufacturers adopted these.

Brad.

It was during the early and mid 80's. We were racing a Donzi hull with a single Bulldog, and a OMC cobra drive. The hull/keel was rounded. That boat wanted to go everywhere but straight. We put 2X4's under the engine blocks to raise the "X" dim. and ran Merc. "cleavers" and drilling holes in the tip, try to dial in the goofy set up. Good times tho... :26:

Julie.. Thanks.. I will try to get some specs and running RPM's / speeds.

 

[Ratickle]

That boat wanted to go everywhere but straight.

:sifone: :rofl: :sifone:

 

[Tomas Wallin]

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

During the process of labbing a good amount of the cup is cut out. This is part of the reason why your RPM increases with a labbed propeller. However some boats just do not respond well to this modification and need the cup put back in. By doing so the RPM will come back down. Now one may not be achieving their RPM goals. So it is not always the answer.

Julie

Yes I can definately see that the props have very little cup.

What if I put the cup back in. Shouldn't a labbed, thinned and sharpened prop with a cup perform better than a std prop?

 

[Geronimo36]

At what RPM is your peak HP produced? If you ran 5200 and your looking for 5600 (your range is too wide) Then you may not even be in the power band of the motor. If this is the case your currently getting a false sense of cruise speed and possibly lugging the motor.

Julie

I'm looking for 54-5600. I have 5250-5300, not 5200. Pk torque was at 4500, pk hp is 5800 and made about 10-15hp less @ 6k. It's within a few hp of peak from 54-5800 and valvetrain is set up for 5600.

I've run smaller props to get to 5700 rpms and the boat is/was slower. It seems to like bigger wheels.

Thanks for the input.

 

[Geronimo36]

Lab Finishing propellers is typically more successful on progressive or aggressive hulls. Conventional Deep Vee hulls with no steps or notches, so not respond as well to labbed props.

Julie

Good talking to you today Julie. For now i'm going to leave it stock and just enjoy myself.

I'll be sure to refer Brett over to you.

Frank

 

[ThrottleUp Props]

Thanks Geronimo36. I enjoyed our conversation as well!

As I said I will help you freind in any way that I can and try to make it fun along the way!

Julie

 

[ThrottleUp Props]

Yes I can definately see that the props have very little cup.

What if I put the cup back in. Shouldn't a labbed, thinned and sharpened prop with a cup perform better than a std prop?

Yes it certainly can! I would recommend adjusting the cup for starters.

Julie

 

[KnotRight]

Julie what thickness is sufficiant for 1500hp plus?
pleasure use.


You may not agree here but on occasion I inspect my blades and take small nicks out with a sharpening stone.

 

[ThrottleUp Props]

Julie what thickness is sufficiant for 1500hp plus?
pleasure use.


You may not agree here but on occasion I inspect my blades and take small nicks out with a sharpening stone.

What hull are the 1500 + HP motors in?

Also taking care of nicks on the leading and trailing edges, at the ramp, is really an good thing to do. At least your cognizant of the trailing edges and the leading edges overall condition, prior to running them. But, I must clarify that there is a BIG difference between a nick on the leading edge or trailing edge and shark bite or a missing chuck on either of the edges.

I would only recommend lightly cleaning up the edges, do NOT try to be a propeller repair technician at the ramp!!!!!

Julie

 

[KnotRight]

46 Skater


I just try to stay on them when I notice a nick.
You really cant take to much off with a stone I,m worried about balancing.

I would never run a damaged prop.


They are hair under a 1/2 inch in thickness?

 

[ThrottleUp Props]

I will get you some info to check the thickness. Give me a bit and I will pm you.

Julie

 

[KnotRight]

I will get you some info to check the thickness. Give me a bit and I will pm you.

Julie

Tank you!!!!

I will be a good boy!