Thread: Prop Depth
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Shawn Gibbs
 
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Default Prop Depth

In article , matt colie
writes:

Boy, you gadda set don n' figur o' What cher doin.


Wish that were the first time I'd heard that!


A propellor will stay working until it aspirates (sucks air in from the
surface). This is not a real big problem for trolling motors and not
even a big issue to IC outboards until SHP gets up there (~50). Not to
mention that you are trying to mix three completely different animals.


It gets worse. The design is a prelim to making it submersible.


Now,
Are you investigating 1-Wing in ground effect, 2-surface piercing
hydrfoil or 3-fully submerged foil with active control??


Yes! This version is a hydrofoiler, probably surface-piercing for control
simplicity's sake, using a WIG structure on the struts as an adjunct only. The
wing-foils are inflatable (think closed-cell parafoil/parasail) and will use a
foil profile incapable of actual lifting the craft from the water (true WIG)
except under high wind velocities when the wing would be deflated. With the
foils inflated, the craft will only be practical on fairly smooth water unless
equipped with fully-submerged foils due to the changes in angle of attack that
would result when it encountered a swell. The wingfoils are also intended to
act as hydrobatic diving planes for the submersible when that time comes.


The motors of electric powered cars are not a lot of horsepower, but the
starting torque is real good and that almost does not matter to the
propellor. Electric machines tend to be "made out of heavy" and
batteries won't help you out there either.


My goal is not a high top-end velocity, but one of efficient use of batteries
.... eventually with the goal of reaching a dive site using the least amount of
energy and without having to have a surface tender. In that respect, EV motors
are a good choice in terms of weight and efficiency. For that matter,
everything has to be considered in terms of weight. When it comes time to
consider the final transition to submersible, I'll unquestionably have to
convert to a hybrid electric due to a relatively substantial increase in weight
(ballast and mixed-gas/rebreather tanks, etc.).


I think you might think about this a little longer.


Me thinks thou art being kind and tactful. I'm of the mind that I'm going to
be thinking (and dynamic modelling and calculating and recalculating and ...)
about this one for a *lot* longer! Truth be known, I'm still not completely
convinced that it can be done as it's currently envisioned -- especially since,
as you so poignantly pointed out, I'm melding several different
technologies/principles not normally mated (and possibly for good reason).
But, since I love designing for designing's sake, that's okay. Sometimes
science is advanced as much from the mistakes/failures as it is by the
successes. Although I very much prefer success, it's still just different
sides of the same coin to me.

Warm Regards
Shawn