T-Pain Is On A Boat: Re: [Electric Boats] Seahawk 17 Project

Tuesday, March 25, 2014

Re: [Electric Boats] Seahawk 17 Project

My personal feelings on all this is to motor at the slowest "comfortable", speed and to look for the sweet spot before discharge begins to quickly increase. 2 knots, or a hair more, should be around that sweet spot where minimal draw on the batteries take place..

The need for near hull speed might prove important in certain, possibly more serious situations and should always be considered, but the inland lakes in Ohio aren't that large .... Mosquito is about 5 miles or so(causeway chops it in half), Pymatuning is about 9 miles(if I remember right ... again, a causeway, the Grand Lake St. Mary, which is shallow, dirty and downright dangerous(pollution/algae). All the other lakes are smaller and very forgiving in nature.

If you generally want/need speed ... habitually, then you'll need more motor and more batteries. After all, it's a sailboat, and that should say something about the kind of boating you are pursuing.

John

Newport 28 on Portage River

On Sun, Mar 23, 2014 at 12:36 PM, <billj474@yahoo.com> wrote:

Thanks for the response PISQUE. I was shooting for a range of approximately 20 miles for days when we just want to totally relax, fish out of the boat or take a nice evening jaunt after the winds have died. I figured on 3 115ah batteries for a total weight of 150lbs or so which I'm not too concerned about as the weight could actually be used up front. I figured this out using Everstart 27DC batteries as a guide and they're what I'm referencing for amp hours & weight. I'm COMPLETELY guesstimating a draw of 25 amps to achieve a speed of 3 knots from the Endura 55 (max draw is 45 amps from what I can find) but it seems reasonable to me on seeing what other boats are posting. I think you are right that this would be overkill on a normal basis and I think I might start out with 2 batteries or even 1 and take the kicker along before deciding. Do you think a 25 amp draw for 3 knots is reasonable with my bilge keels? What do you think about a thru hull installation behind the keel in this boat? Here's what I came up with (thanks to all the great info here!) and what I was basing my idea on -

3x115amp hours=345 total available amp hours + 150lbs additional weight in boat at a cost of $240 (+-)

345amp hours/2=172.5 useable available amp hours (not draining batteries below 50%)
172.5amp hours/25amp draw=6.9 hours of use @ 25 amp draw
6.9hoursx3knots=20.7nm or 23.8 mile range @ 50% discharge which is close to what I'm shooting for as a max daily distance but doesn't take into account wind, current, less than perfect charge state, cd system, VHF etc.

2x115ah=230 total available ah + 100lbs of additional weight at a cost of $160 (+-)
230ah/2=115 usable available amp hours (not draining batteries below 50%)
115ah/25amp draw=4.6 hours of use @ 25 amp draw

4.6hoursx3knots=13.8nm or 15.87 mile range @ 50% discharge

1x115ah=115 available ah + 50lbs of additional weight at a cost of $80 (+-)
115ah/2=57.5 usable amp hours (not draining batteries below 50%)

57.5ah/25amp draw=2.3 hours of use @ 25 amp draw
2.3hoursx3knots=6.9nm or 7.94 mile range @ 50% discharge

Thanks,

Bill