Prop shape help again...

[larryrose11]

OK guys,
No spitting venom this time please.
I have a lot of respect for the people on this forum.

The Octura X series Has a big tongue. I understand that this feature helps with acceleration, but serves as a governor that limits top speed.
cat__09_05_2007_23_28_x4-series-icon.JPG

The Octura M series has a smaller tongue., and is generally regarded as a prop that can give more top speed
cat__09_05_2007_23_19_oct-m-series.JPG

If this trend of removing the tongue s continued, you could get to something like this: a SS 32 x 36 prop from Tenshock
prop4mm.JPG
something similar to this is the Octura N series
cat__09_05_2007_11_26_oct-n-series.JPG

So...here is the question: Does removing more an more tongue give you more top speed? What is the downside?

[kfxguy]

I'm still learning myself but i'll tell you what i have learned. I have been doing lots of prop testing so this is my real world experience and not me just repeating what someone else has said.

Removing the tongue will give you more speed. i have not gone very far with it yet...as in remove much more than an M series just yet....I'll do some experimenting to see how far i can go soon. Having more tongue helps you get on plane faster....seems to be more helpful in a mono....

I havent has any problem getting on plane except with that octura 20 series prop. It took about 10 feet to get on plane and when it did...it turned into a plane because the boat would launch into the air out of the water. not cool.

What i suggest to you is doing the same thing im doing. Start slow. buy a few props to experiment with. buy a couple m series and practice turning an x series into an m. If they offer an x series and an m series in the same prop...buy both. make the x series match the m series in speed. Youll be able to tell what works and what dont. gps is your friend so you can see definate results and not guessing. Its takes time...and is a leaning curve but the outcome is priceless...you wont have to rely on someone else to do it for you anymore. Its quite fun too...except the retrieval part when you have a nasty prop that dont act right...lol

[SweetAccord]

Cavitation is the problem if there is too little tongue if you go too small, and when you remove the tongue area more and more, you are losing torque as there is less bite for the prop area, giving you more top end.

[kfxguy]

Cavitation is the problem if there is too little tongue if you go too small, and when you remove the tongue area more and more, you are losing torque as there is less bite for the prop area, giving you more top end.

Welcome! Haven't seen you around in a long while!

[kfxguy]

So....would those tongue less possibly be faster top speed?

[SweetAccord]

Thank you, I've been lurking. Thank you for the warm welcome.

Yes they are faster, but to a point for any hull. The tongue in the X series are like a high speed limiter. This area (tongue) has been found to greatly limit the top speed of all props. That is why they created the M series that has less tongue to gain more speed but of course to a point, and the other side of the negative is that hole shots are reduced.

[kfxguy]

Thank you, I've been lurking. Thank you for the warm welcome.

Yes they are faster, but to a point for any hull. The tongue in the X series are like a high speed limiter. This area (tongue) has been found to greatly limit the top speed of all props. That is why they created the M series that has less tongue to gain more speed but of course to a point, and the other side of the negative is that hole shots are reduced.

I have a big problem with having too much out the hole. My boat will jump a fit or more into the air unless I'm very careful. M645 prop. I didn't cut any more tongue off than factory tho. Maybe I should.....

[NativePaul]

Personally I take a little more tongue off my X series props than Octura did with the M series, but I am an endurance racer and anything I can do to reduce the amp draw is important.

I have seen folks running those low pitch Tenshock props with amazing results, spinning decent sizes at insane RPM and still getting 5+ minutes runtime, I've not tried one myself though.

I love the N series blade shape, and have cut several N940s down to different sizes with good results, but I wish they did them in a full range of 1/8" and 3/16" sizes, and with a more reasonable 1.4-1.6 pitch rather than 1.9 which is a little extreme for racing.

[SweetAccord]

I have a big problem with having too much out the hole. My boat will jump a fit or more into the air unless I'm very careful. M645 prop. I didn't cut any more tongue off than factory tho. Maybe I should.....

Well with M series, they are a different animal to gain speed. With M series you want to do what is called a barr back cut fig#4. Use a ball mill or dremel to make a round cut and accomplish the same reduction of load in the trailing edge. The area you remove it the upper side. You can get the same effect with a back cut. See Fig #3.

untitled2.pnguntitled.png

[srislash]

I have had good success with the backcut #3 on M447's and M645's. I have not tried the barr cut yet, I know there are concern of hub weakening with that one.

[kfxguy]

I guess I'll try it