Pacificmeister Build Info and CAD Sources


#122

Strange. Can you check the dimensions in he fusion model? Maybe something went wrong with the STL export.


#123

I also have the rocket foil, just made the mount a tad longer on each side Foil mount I can post the file if you like


#124

Thank you all for your help! Yes pacificmeister, I checked the dimensions and it really seems that the rocket foil is too long. So @Sourcecode yes it would be so nice if you could post this new file as I’m really bad in CAD! :slight_smile: What are the exact dimensions of your foil? Liquid Force says 124 x 13.5 on their website but mine is 132 x 19 in reality.


#125

@Fabien_n Yep is is 132mm. I think that measurement is for the 2016 foil maybe? I used 2 M6 130mm long stainless steel bolts to clamp them together i also have a water cooling intake on the mount but i removed it in this version of it
Rocket foil mount


#126

Thank you so much! Yes I think that’s the 2016 on their website, mine is a 2018 I got from a friend that has kite shop. I will use a water cooling system as well, but haven’t yet figured out exactly where to make the hole for in on the mast. Did you do it on the back, the side or the front of the mast on yours?


#127

@Fabien_n . No problem! i made a 6mm hole for a pipe going back up the mast to the ESC. The hole is on side of the mount where the cables come out of the mast. Im gonna use a self priming 12v/6v pump that can suck water from 3m and pump it 2m or so.


#128

Thank you! And here is my pump https://www.amazon.fr/gp/product/B016U4NIIA/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 about the same specs as yours! :slight_smile:


#129

pacificmeister, apologies if you have answered this already, but 1) what soil section is your duct? 2) you are twisting the water with the struts that hold it steady - is this to counteract the twist you get in from the prop? It doesn’t appear so if your prop is a CW screw… how does this work? 3) what section are you using on the prop, have you seen cavitation to date? Thanks.


#130

Hi Brent, i am not sure I understand all your questions. Regarding the angled duct struts, I took this idea from the @Hiorth duct. Worked well. Only thing is that it creates a CCW moment on the duct an I had it unscrew once while riding and it melted into the prop. That’s when I added the little set screws. Don’t know what the science is behind the angled struts. @Hiorth? Are you guys still doing that on your latest desing? I want to continue trying different duct shapes to see if I can reduce drag at highes speeds.


#131

Hey pacificmeister,

Thanks for reply. I did see your thread problem - that sucks. But if you mirror the thread it’ll probably over tighten though, just to be ironic and difficult. :slight_smile:

I don’t like ducts in theory, because they are lossy and eventually limit speed. Also, the chances of getting an accelerating duct like a Kort/Rice style nozzle right without CFD are pretty poor. Why don’t you try a pure 0012 with no angle of attack? The drag can be calculated quite easily. I think 0012 is about the lowest drag foil you’ll get.

The angled struts are interesting because at 0 m/s, they’ll do nada, but at higher speed they’ll turbulate and twist the water. The former is of no use since the Re of a fast blade isn’t a problem, but the twist could be opposite to the twist introduced by the prop giving lower wake turbulence/twist, perhaps an efficiency bonus. The water hitting the blade at the right angle for good ‘push’ essentially… ?

The main loss of energy and cause of inefficiency is pushing water. small props jet water backward. The shape of the wake you make is an expression of efficiency, and ordered directional wake means you’re doing it right.

The foil you are using in the duct is chunky and I’ve not seen it before. Curious to know what it is. I’ve tried naca4415 after reading a paper, but haven’t gotten too far.


#132

We are not experienced with hydrodynamics, we just read some theory and designed the prop and duct based on this (we are still using almost the same setup as our first design, will start to improve this when everything else is up and running well). The propeller profile on our prop is a B-troost .

The idea is to rotate the water prior to the propeller (that rotates the water the opposite direction). According to theory this will improve efficiency as less rotational energy is lost downstream (the downstream should now be more “linear”). We have not done any calculations, we only based the design on theory we read.

CFD analysis of this particular setup is really a pain, as there are so many variables. But we do believe the rice nozzle we use improves thrust and efficiency at low speeds (vs open prop), and cause drag in high speeds (10knots+).

In our later design, we have moved the twisted stators to the rear part of the Hiorth duct. Mostly because we wanted a guard against fingers/toes in the propeller on the rear part as well, but we also read that twisted stators at the rear of the propeller actually can give net positive thrust (which is nice). If we actually get net-positiv thrust is another story…

We are currently designing a high speed duct (and propulsion unit), with a profile similar to NACA 0012, will see how that performs.


#133

@pacificmeister got all my 3D printing done now and thanks again. Parts arriving now.
Just wondering if anyone has had issues with the ceramic bearing and lip seal surfaces. I got the latest seal mount. My seals are not a press fit and can fall out. The ceramic bearing is also not press fit tight. I am printing on a high tolerance work printer and was thinking maybe making the diameters smaller. Or did anyone glue them in ?


#134

Hiorth thanks so much for coming back to me on this!! All makes sense now.

Will u stick with btroost for prop?


#135

I’m very interested in the twisted stators behind prop. Can u share the reading reference?


#136

@morgansteven1970, my home printer tolerances are not great and I didn’t try to make it a tight press fit. It’s fits well but is not super tight. I use some silicon to lock seals and bearing in place.


#137

@pacificmeister ye its a trick one trying to work out the tolerances of bought materials and getting the model dimensions right to accommodate this and get the fit just right. Cheers for your feedback.


#138

The reason we choose the B-troost thrust section was to be able to 3d print the prop (thicker section in the center), and because it seems like a good propeller section. Our final goal is to optimize everything, so we can ride as long as possible (and SAFE!) on one charge.

We read about the stators several places (cant fint all of them now), here is one. We “need” the stators for safety reasons, so it was nice to combine them with net positive thrust.


#139

Hi
Where do you find motor reduction NEUGART PLE 40 5:1 , it’s very difficult to find it on used category or price is very high to buy new version !
It’s exist another solution or this reduction is very calibrate to this project ?
Regards


#140

I found my Parker 7:1 on Amazon for $64 new. Directly from Parker. No idea why it was that cheap. Got the Neugart on EBay for $120 used. Not easy to find cheap and get fast, lots of discussion on the form. Try the forum search. Also lots of discussion about other gears and direct drive. Keep reading :smile:


How I will make it true - some points to think about
#141

Actually when you started your project, I remember looking for a Parker and I found 2 options on amazon us. One was around the $74 and the other around the $400 price point. Both claimed to be Parker, but I’m pretty sure one was a reseller.