T-Pain Is On A Boat: Re: [Electric Boats] Electra Glide Data and updates

Wednesday, December 16, 2015

Re: [Electric Boats] Electra Glide Data and updates

Numerous examples online ... prop calculators for std use.

For best efficiency, or in commercial use for most thrust (tugboats),
drive ratios go to 4:1 - 6:1 vs typical 2:1 on pleasure boats
sizes go 3-5x larger in diameter
and thus speeds go down to 200-600 rpm.

Thus;
5 Hp in use (ICE) for 30 ft boat, 6 knots speed.
10" prop, 6" rise, std prop (at 2500 rpm)
Relative area= radius squared, or 25 inches square.

Probably:
16-18" prop, 3" rise (2-4")
8 pwr 2 = 64
9 pwr 2 = 81
81 / 25 = 3.24 difference.

2500 / 3.27 = 771 rpm.

My (guess)estimation, based on physics and lots of anecdotal evidence.
About 18" D prop, and a 2-4" rise, at 600-700 rpm at prop, would be "better".
18" is little, compared to keels on sailboats.

This will likely be more efficient by 20-40%.
If this is actually true, a 20% efficiency gain is huge.

It would also point out that my calc re: range, for circa 10 m boat / 34 ft.
6 knots at 3kW, 18 hr x 3 = 54 kWh needed, vs 80 kWhr, or 60% less.

Data point.
This seems likely or at least possible, since the prop calc indicated 5 Hp used (ICE), at 6 knots, for the example data.
Data point.
It also seems likely since very little power is used on small sailboats at 5 knots, and the props are usually undersized and anemic.

On 16/12/2015 16:12, 'Sdolan' sdolan@scannersllc.com [electricboats] wrote:

I'm checking with the Prop Designer for more info but I think they only did a balance on the ones used not make them from scratch.

www.wildcatprops.com in Chesapeake, VA

I have little info on the props but the boat is being hauled out in a few weeks and I'll see if the Yard can give me some visual data on the props themselves. I'm no were near knowledgeable on props but think it's deserving of my attention if there is improvements to be made in performance.

Steve in Solomons MD

Lagoon 410 SE