Question about props.

[Clugh]

Halo Christian,

Haben Sie ein 3D-Modell eines Propellers mit dem Johnson 5-Tragflächenprofil?

Wenn ja, wäre es nett, wenn Sie es mir zeigen könnten, damit ich es für meine SAW-Projekte verwenden kann.

Gibt es noch andere superkavitierende Tragflächenprofile, an denen Sie interessiert sind? Ich habe Ihnen einige Dokumente mit späteren Tragflächenprofilen geschickt, falls Sie sie noch haben. Ich hatte sie mir noch nicht angesehen, als ich Ihnen das Dokument schickte.

Viel Spaß mit dem PDF, es ist sehr informativ.

Danke
Hubert

[Clugh]

The other thing Id wonder about is the leaf shape and BAR.

Thanks for your time and patience,
Hubert

[Clugh]

[Clugh]

In the meantime I'll see if Brenner can help me to create a few 3d models that we can possibly do a lost wax casting utilizing 3DP wax.



TTYL
Hubert

[Chxpress]

Hi Hubert,

i have not found today the pictures of the Johnson 5 Term suface profile , but there is the publication of it , https://archive.org/details/theoreti...0lang/mode/2up
Also the paper of the Hydrofoil SWATH-WIG , https://www.marinepropulsors.com/pro...2015/MB2-3.pdf

And do you know about the leading edge spoiler ? Look at the picture and other Spoiler that are at the trailing edge ?
This is what i have testet with some propeller when i didn`t know about this papers. They are not Open Source so i have only the copy from the search Site. The Spoiler makes it possible that the water will not touch the sucking surface of the propellerblade , so less resistance.

I use normal hand-made propellers and grind a hollow key in front of the tear-off edge on the pressure side of the propeller blade. Then I gently balance the course so that there are no too abrupt changes in flow. I've done this with a lot of propellers and it always results in a propeller that grips very well and accelerates very well. Here are a few pictures of propellers whose blades I have edited.

Happy Amps Christian

[Clugh]

Excellent post! It all gets filed!!

Here is a reference for Virgil. I found some profiles ill post them. No longer confidential.

Johnson, V. E. (1957), Theoretical and Experimental Investigation of Arbitrary Aspect Ratio, Super-cavitating Hydrofoils Operating Near the Free Surface, NACA RM L57I16.

Thank you for your time and patience,
Hubert

[Clugh]

Hi Hubert,

i have not found today the pictures of the Johnson 5 Term suface profile , but there is the publication of it , https://archive.org/details/theoreti...0lang/mode/2up
Also the paper of the Hydrofoil SWATH-WIG , https://www.marinepropulsors.com/pro...2015/MB2-3.pdf

And do you know about the leading edge spoiler ? Look at the picture and other Spoiler that are at the trailing edge ?
This is what i have testet with some propeller when i didn`t know about this papers. They are not Open Source so i have only the copy from the search Site. The Spoiler makes it possible that the water will not touch the sucking surface of the propellerblade , so less resistance.

I use normal hand-made propellers and grind a hollow key in front of the tear-off edge on the pressure side of the propeller blade. Then I gently balance the course so that there are no too abrupt changes in flow. I've done this with a lot of propellers and it always results in a propeller that grips very well and accelerates very well. Here are a few pictures of propellers whose blades I have edited.

Happy Amps Christian

That leading edge spoiler creates leading edge cavitation which is excellent for the slip side of the propeller. You understand. Supercavitating boat profiles are too complicated for JAVAPROP and a basic camera to work out...

😯

You have to have true 3d mapping software with real 3d camera. You understand the process. They have one at Daimler where I was. In the R&D department they have a very nice one and a full aluminum layout table with threaded anchors a in a cartesian layout. You could do everything from build a full conceptual 3d model of anything to a full test bench for any dream.

You know a real R&D lab looks like.

Hubert

[Chxpress]

Hi,
do you remember , the contra rotating props that i let Fabian Wunderlich manufaktur for his Offshore tunnel boat. This was in july 2012 . With this propellers he had 10 % higher top speed and 15 % less Input power. This workes excelent. So i do the same with the saw propeller .
The whole Powercroco Truppe looked at it an didn`t understand how and wy . Has no influence on them. So they become slower and slower.

Happy Amps Christian

[Clugh]

Hi,
do you remember , the contra rotating props that i let Fabian Wunderlich manufaktur for his Offshore tunnel boat. This was in july 2012 . With this propellers he had 10 % higher top speed and 15 % less Input power. This workes excelent. So i do the same with the saw propeller .
The whole Powercroco Truppe looked at it an didn`t understand how and wy . Has no influence on them. So they become slower and slower.

Happy Amps Christian

I understand and will have to try a few. I guess the cleaver and the chopper are the most prominent leaf selections for hydroplanes.

Thank you
Hubert

[Chxpress]

Hi Hubert,
I used the propeller blades with the Cavitation Spoiler to be able to use thicker propeller blades. The very thinly ground propeller blades that are normally used are already very limited even with the best types of steel and can no longer withstand the very high torques when accelerating. Thicker blades can withstand it, but had more friction resistance. That has changed with the spoiler as the performance data shows.

Happy Amps Christian

[Clugh]

Hi Hubert,
I used the propeller blades with the Cavitation Spoiler to be able to use thicker propeller blades. The very thinly ground propeller blades that are normally used are already very limited even with the best types of steel and can no longer withstand the very high torques when accelerating. Thicker blades can withstand it, but had more friction resistance. That has changed with the spoiler as the performance data shows.

Happy Amps Christian

Right! I can see the idea is to be fully ventilated and avoid surface cavitation on the slip side of the prop. latest ABC is using newton radar series foils. They have enough option that you can get a thicker or thinner RAW prop. For me It is better to not modify them at all but simply remove all the casting overhangs sharpen and balance with the leading edge detail. I wonder what's achieved with then newer trailing edges I'm seeing. There was a time that we glass beaded the slip side and polished the suction side. See what we were after? Its similar but a different way to get there. It wouldn't be as affective as the LE spoiler. It would be cool to see a casting with a tru notch there at the leading edge.

It is also noted that Supercavitating actually translates to a LOWER cavitation number.

Switch gears for a second. Have you or is there any data from your friends like UWE Plettenburg or Hans Lehner that illustrates different amp draw based on BAR?

Also is the bose vented how FSRV props run?

Thank you
Hubert

[Clugh]

It is also noted about the 5 term Johnson profile .....too thin.


At finite cavitation indexes, the real cavity thickness is important and the shape of the back must be designed in order to obtain the maximum profile thickness at each chord station (to increase the section area modulus, for strength reasons) while ensuring that the back line is still laying inside the vapor cavity. From the comparison of the designed face camber lines (Graph 6), it was decided to discard the Johnson 5-terms line, because of its strong thickness reduction of the profile area close to the trailing edge, resulting in a rather poor sectional modulus of inertia. The largest inertia modulus for the profile is ensured by the Tulin-Burkhart camber line, so this type of face line was the first to be simulated. As in other conventional supercavitating profiles, the trailing edge was sharply truncated and with a trial and error procedure the thickness distribution along the chord was calibrated in order to obtain the maximum sectional area still remaining in supercavitating conditions, as from Figure 6.

~Super-Cavitating Profiles for Ultra High Speed Hydrofoils: a Hybrid CFD Design Approach~

[Clugh]

In the paper the three term Johnson version 4 is where they settled. You see the backside vapor cavity spans the entire chord length.

[Clugh]

This basic profile would likely need to be forged, casted, or printed. One wont modify an existing prop trailing edge into this.

[Chxpress]

Hi Hubert,
It's nice that you're going with me, the stupid flying heroes don't understand it. Also keep in mind that the images of flow and separation are created at high speeds. At low speeds, i.e. low propeller speeds, this condition does not yet occur. The spoiler enables detachment at lower speeds in partial load operation. As always, there is of course some kind of compromise that can be adjusted. But my experience is that the sooner you reach these conditions, the more efficient and energy-saving the propellers will run.

Happy Amps Christian

[Clugh]

I understand totally that the LE and TE addendums will help it grab in the sub cavitation zones. Low speed and hole shots.....and then perfrom really well at high speeds with no extra mechanical stress from the ultrasonic beat down of surface cavitation.

[Clugh]

Hi Chris,

I'm thinking about printing Jims gauge and the leaf lets to go with it versus the dial indicator even though I'm not fully versus how to use it in every way. I know he said it could also record the helical pitch which he determined to be a different thing. Most boat props we use have a progressive pitch.

JAGS props do not itz constant..

I need a way to measure it and the blade thickness before I start a sharpening and balance process.

Hubert

[Clugh]

For the thickness measurement.

[Clugh]

Sorry wrong thread.

[Chxpress]

Hi,
i have different mesurment tools .
the green i build during university to messure a glas fiber cylinder after production prozess.

Happy Amps Christian