Nice build without a single hole drilled into the mast !
@Gobbla Nice work, It looks amazing.
You have many fantastic features in your design !
One question what is the logic behind the long propeller shaft ?
Cheers,
Al
hello theone, for me the logic behind the long propeller shaft is to decrease turbulence after aluminium pipe.
i m not using princple of ducted proppler (Kort nozzle).
I m juste protecting proppler for user. It is less efficient than kort nozzle, but efficient of ready made aluminium proppler is 30% more efficient than 3D printed proppler (tested).
@SoEFoil you right i did not make any hole in the mast. i m planning to use fiber carbon mast without hole inside. ESC is cooled with air.
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Hello Gobble,
Good point turbulence / Cavitation = Reduced efficency!.
30% (TESTED) is a huge saving with a ready made prop.
As you know a Kort nozzle is not suited for high speed boats (or efoils)
What is the pitch & diameter of your propeller?
What RPM do you spin your propeller at?
Gearbox Ratio ?
Thank you Gobble
Best Regards,
Al
I want to go the same way, but I am not sure whether a tube or a cage design will be more “effective” (sure both will create drag, the question is which one will create less, cage has less surface area but more turbulences…)
Do you know, how much power you loose by the protection/duct? (test with ampmeter with and without duct, or maybe even different ducts?)
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for the test it is here : Propellers and Ducts - #72 by Gobbla - Props & Ducts - FOIL.zone
static trust is easy to measure
you right i dont have comparaison of drag, i have tried to reduce it with using 2mm aluminium sheet, (impossible to obtain with 3D printed part)
the best would be to test it on side of boat with scale at different speed, i will think about it for next autumn
that is not what I meant.
Okay, but my question was, is it better with intact tube or better with something like that:
Okay, but in my opinion best would be to just try it in the final setup and log everything (speed, RPM and Power). So you also see the effect of the spinning propeller inside the tube…
hum not enough specialist, sorry can not help you
i dont have data logger. (yet)
Definitely intact tube, no doubt about that. Better if you thin your trailing edge and round a little the LE… it reduces turbulences.
Long means more drag, this goes for the motor pod as well, even though good profiles of nose and back end could improve the situation. With Efoil the problem will be that the tube won’t run horizontal, almost never. You’ve to improve this by fine tuning wings AoA, this will reduce greatly the drag loss
Guys this is just a concept to stop a foot going into the propeller . Yes it still has risks albeit a little better than a foot into a propeller.
Do you think it would have lower drag? & improve safety just a bit ?
It may inspire some one to take the concept to the next step of hinging inwards when not in motion ???
@Gobbla Have you been inspired by this post ? http://www.efoil.builders/t/builders-how-not-to-drill-your-alu-or-carbon-mast/112
wood floor skirting solutions on the internet: PVC flexible skirting band, 10USD for 20 metres with 3M adhesive
I am fascinated by your metal work. My 3D printed parts look quite cheap in comparison 
May I ask why you built such a long tail, as the shaft to the prop is consequently very long and may accentuate vibrations ?
@SoEFoil, yes i take some ideea from this post, and adapt it to my round cable
@philgib i have made long tail to avoid turbulence before proppler.
At high speed for me it will reduce efficency of proppler.
I did not make calculation to define the best length
some of my inspiration :
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I would try to make much more room for the motor cable solder joints. Mine ended up about twice as thick as the cables because I had to make them waterproof. They are also very stiff.
I like the counter rotating propeller 
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Yes ! We need to make this! Pefect way to complicate things!? Started planning some months ago and orderd some gears and bearings but the project died a little.
Any one want to join in with CAD and R&D
We can do a open source build on the forum?
Efficiency of the system may be improved slightly, but it also removes the torque generated by a single prop drive. But most importantly it looks super COOL!
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2 propellers turning in the opposite direction on one shaft ? It is going be complicated for the gearbox… N6 and hollow shaft… It is crazy !
Yes two props on one shaft.
can be done this way
(red shaft is hollow)(green gear is held in place)
same as in the torpedo drawing. Will have to so something clever stuff with the seals and bearings.
Cool, I am in
Would it make sense to include the reduction at the same time?
Not possible for me ,blue same speed as red
For gear réduction , it will the same a car , propeller in front and in back , motor at 90 in line with mast …