Propellers and Ducts

Cool did you try the hiorth duct with this prop?

-und momentum schon getestet? Ergebnis wäre interessant…:wink:

Hi Simon, my current values and speed come from my own personal arduino hacker set up and should be taken with a grain of salt. I’m pretty confident that the numbers I’m recording have alteast +/-10% accuracy. The prop was designed for me and my own setup to minimise slip and maximise efficiency. It will vary setup to set up.

Aaron

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Tunnelvision, where i buy this propeller? Thanks.

Which propeller? Mine? I used existing CAD and modified it to my needs then 3D printed it. Happy to share the file. Here it is.

Aaron

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Hey Guys, A backer of my Kickstarter Project found a really good program for wing foils and props both air and water. It helps you designed and test everything on the spot with JAVA based program. I have not yet read through the entire site but looks interesting.

You can even select the prop surface finishes…:
Smooth
Painted
NACA Standard
BUGS AND DIRT… yes, this is an option

https://www.mh-aerotools.de/airfoils/javaprop.htm

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@pacificmeister What pitch prop are you currently using with your 5:1 ratio model? Thank you in advance!

Hi @Graystorm44. I didn’t calculate pitch. Maybe you can? :slight_smile: Have a look at the CAD here. I have successfully used the 3 and 4 blade props created with this parametric prop setup and the default parameters. The Fusion setup was since improved by @Taylor here. You can quickly adjust all the curves to modify size, shape, angles… resulting in pitch changes.

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Hi VeFoil,

I’ve played around with that program in the meantime and find it very helpful. I would be really glad if someone with some propeller experience could have a look at it and confirm that for all of us. :slight_smile: Would be very cool to be able to reliably calculate the efficiency and thrust of a setup before buying and testing various parts.

Cheers,

Sascha

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yea, having similar thoughts, I’ve be at marine shops looking at small 3 to 8 hp outboard motor propellers plastic and aluminium, if we are aiming for around 3000rpm and maybe to have a amp current meter and a few temperature reading sensors, then it could help on the calculations,
i have played with different props on my 70hp outboard, and its just to not risk to over rpm by to light of a pitch (but it will get on plane faster) or to have a to aggressive pitch and risk stressing the motor (and for us electronics), i think trying different props is the only true way, and a way to read the data in real time

in an ideal world a servo controlled variable pitch propeller would be perfect, gentle pitch for start up, and then aggressive pitch for when up on the plane,
so its finding the sweet spot of compromise

I have a concern that some might automatically think that having a duct will make it safe. Nothing against any of the other comments but I have as many concerns about a duct setup as without.

  1. The duct it self can have many sharp edges if not designed right. Rounded trailing edges are very inefficient so we tend to make them thin
  2. A large duct is inefficient so we tend to make it as small as possible. This can create a scissor effect between the duct and the prop.
    I personally plan on running with no duct but will take other precautions to make the propeller as safe as possible.
  3. The leading and tip edges will be rounded.
  4. I want to use an out runner motor to keep the assembly as short and close to the mast as possible.
  5. I will have a disconnect with a lanyard. I have already accidentally bumped the throttle when falling.
    Regardless, there should be great caution from the rider about where their feet are. The mast and especially the trailing edge of the wings can injure a foot. Having flown model aircraft all my life I have see how little or much damage a spinning propeller can do to fingers and they are spinning at 30,000 rpm.
    Mike
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Thank you sir, You are an awesome resource! I enjoy watching your progression!!

yea i hear you, safety all the way, i am thinking of trying a 5 to 8 hp outboard engine propeller, or maybe the aliexpress thruster propeller assembly with the duct, trying to work out the best option,
so far i have the sss 360 kv motor a 240amp esc, and the neugart ple 60 5:1 (the ple 60 has a higher Nm range)
so do you think the open propeller is the best option?
its just rapid cutting off the power if (when) you fall off might make it safer

I don’t know what the answer but Dan and I plan on doing some safety testing this winter with different prop and duct configurations. I just want more open thinking and discussion on the subject.
Mike

Anyone try this software?

https://www.mecaflux.com/suite/en/heliciel.php

Looks better than the javaprop hah

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Javaprop is getton looking but it works well. Tested three pops today in thrust tank, and specs were almost exact to what javaprop said they would be. Really amazing and is a game Changer.
When using javaprop be sure to change the LAST TAB - OPTIONS. For water… or else all your props are being tested in air density.

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I think the wings in Javaprop become amazingly small. Is this realistic, that such a thin blade can withstand the thrust? I already double and tripled the chord length, but by this the efficiency goes down.
I would have to make these blades out of steel, at least carbon.


It is calculated with Dia:17cm, 5000RPM, 7.5m/s, MH116.
Analysed: eta 72%

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did you set the options tab for water prop settings?
SEE SETTINGS: http://www.diy-electric-hydrofoil.com/java-prop/#!/up

Is this really correct? I am missing one 0 in the kinematic viscosity compared to


http://www.viscopedia.com/viscosity-tables/substances/water/
It does not have much influence at the chosen RPM and velocity. So RPM is definitely too high.
I will try to get a motor with less kv, optimized for our needs. Maybe Alien 6384 with 65kv? What do you think?