T-Pain Is On A Boat: Re: [Electric Boats] Dirty prop

Tuesday, June 4, 2013

Re: [Electric Boats] Dirty prop

FYI: Those "bubbles" are partial vacuum, as such, they collapse or implode.

--- In electricboats@yahoogroups.com, "cire" <cirejay@...> wrote:
>
> BTW, those tiny bubbles, exploding can wreck havoc with your prop.
>
> eric SV Meander
>
>
> --- In electricboats@yahoogroups.com, Julian Webb <julian.proto@> wrote:
> >
> > You might also be getting cavitation caused by the barnacles, which can be
> > seen as more "air" in the prop stream. this can see the prop or parts of it
> > anyway spin in an air bubble which partially unloads it but also means it's
> > not in as effective contact with the water as is a clean prop.
> >
> >
> > On 3 June 2013 14:28, oak <oak_box@> wrote:
> >
> > > **
> > >
> > >
> > > Interesting...
> > >
> > > I had something kinda' similar this weekend - went out to the boat to
> > > check on things... I have my Torqeedo 4R mounted on a C-22 now, and
> > > turned it on just to verify that the batteries were all good. The boat is
> > > not in the water, so the prop is just spinning in the air (the manual
> > > specifically states that one should NOT run the motor out of the water - so
> > > I only did it for a few seconds). The interesting part was that it hit
> > > full throttle, and the display was only showing about 250 watts - no where
> > > near the 4kw that the motor is capable of drawing.
> > >
> > > Since there was no resistance on the prop, I guess the motor hit max rpms
> > > and just quit drawing any more power.
> > >
> > > ------------------------------
> > > *From:* NIcholas Luker <nickluker@>
> > > *To:* electricboats@yahoogroups.com
> > > *Sent:* Monday, June 3, 2013 6:09 AM
> > >
> > > *Subject:* Re: [Electric Boats] Dirty prop
> > >
> > >
> > >
> > > That happens to my prop
> > > Being a small fantail launch thats still diesel :(
> > > I can see the wake from the prop easily
> > > When the props dirty the engine revs much higher and there is a tube of
> > > aerated water behind the boat at the height of the prop
> > > As the barnacles spin off the revs drop
> > > The engine works harder and boat speed increases
> > > The tube of aerated water also starts to disappear
> > >
> > > Nick
> > >
> > >
> > > On 03/06/2013, at 11:37 AM, Dennis Wolfe <wolfeboats@> wrote:
> > >
> > >
> > > The critters must be affecting the blade profile and reducing its "bite"
> > > on the water. More turbulence, less thrust, less power needed to reach
> > > whatever rpm corresponds to 48v.
> > >
> > > On 6/2/2013 9:07 PM, R&M Mair wrote:
> > >
> > >
> > > My prop is currently got some critters attached. I notice that instead of
> > > 20 amps giving me 3.6 knots I now need 25 amps to get 3 knots. This makes
> > > sence to me. The thing I do not understand is why full throttle now tops
> > > out at 45 amps. I get a about 4.8 knots at 65 amps with a clean prop.
> > > Should I not be able to hit max draw of 100 amps with the prop like this or
> > > at least get the 65 I got before. All at 48 volts. Electric Yacht 100ibl
> > > system.
> > > Richard
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> > --
> > www.proto.eu.com ltd
> >
> > unit 9 Somerton Industrial Estate, Belfast, BT3 9JP, U.K.
> > Phone; (+44) 02895 811251 - Mobile; (+44) 07427 696 796 - Fax;
> > (+44) 0871 9898296
> > Company number; NI067673 VAT number; GB975375474
> >
>