Yes, the Searunners which are not light weight racers but blue water cruisers do move along quite well. Here is a link to "my" boat (sister ship by designer) Scrimshaw Part 7 which will give you an idea what they are all about. Mine is newer and a bit nicer inside but Jim has the new swept transom and some other bells ans whistles I don't have. The 40 is a BIG boat! Searunner 40.
My 9.9 gas OB is enough to push the boat along at 6-7 knots. Certainly 5 knots easily. Any time the water is choppy there is wind so except for motor sailing with a tiny bit of prop I am sailing without engine. In very calm conditions I can move along at 3-4 knots with a light reacher where a Catalina 42 I sailed would be motoring in anything less than 10 kn wind! And that is a light mono as monos go.
I've had my boat for 9 years. I bought it in Toronto and thought maybe I'd reall go cruising with it but I haven't and at 63 I am being pragmatic - I may not. So, I put it on the market along with Scrimshaw (My Boat, Jim's Boat - scrolldown to see Jim's boat). So it may not sell so fine I will just keep on enjoying it as much as possible therefore the electric stuff - why not?
But yeah, you got to have any of these you are thinking about buying surveyed - they are wood!
I am really ignorant of electric. I don't even understand the language that well. But I have seen stuff like this Pod Master that really inrtrigued me because it would fit nicely right under the double in the stern and would be a simple retro. So I wonder about doing a conversion. If the Lithimums can take 2000 cycles that seems pretty cost effective. Again - the weight still may be the deal breaker.
Thanks for the reply,
Jim McComb s
On Thu, Feb 21, 2013 at 12:14 PM, Michael Mccomb <mccomb.michael@yahoo.com> wrote:
read about your trimaran with great interest as i have done a lot of studying on doing such a conversion... a trimaran seems like the perfect candidate to me as it takes so much less to push them through the water and that CAN translate into a pretty nice range at decent speed... where a mono tops out at 6 or 7 knots a tri really isn't requiring too much power to attain that sort of speed....while i don't care about the currently included engine at all i've been looking for a Searunner 40 in good shape hull wise.... unfortunately they CAN be ridiculously compromised by rot if EVER neglected.... i read with great interest your generator idea as again, this matches my conceptions.... there is a German company that builds a really nice diesel engine that is mated to a dc generator and used to power north sea oil rigs as reliable backup.... these Hatz gensets are rated at continuous duty and burn around a quart an hour while putting out about 10hp/7.4kw which will probably move a trimaran along rather nicely.... so at least somewhat paralleling your concept i figure a battery powered motor with diesel backup for emergency situations for either boost or long range/duration capabilitiesi'd really be interested in communicating as you plan for and perhaps begin your conversion.... where/how did you find the searunner 31?
From: JAMES MCCOMBS <jimske49@gmail.com>
To: electricboats@yahoogroups.com
Sent: Thursday, February 21, 2013 10:03 AM
Subject: Re: [Electric Boats] Re: Converting a small trimaran to electric drive
Interesting stuff. Nice battery.I am going to find out what weight my 6000 lb trimaran can easily carry. This is a blue water cruiser so it expects to carry at least 2 adults, 75g water, 20 g, plus food and other necessary stuff. So I suppose it could take some weight without compromising too much. As it is the boat with fuel, water and one person (me) does half the wind in any wind. Will do 10-12kn in a 25kn blow pretty easily so maybe sacrificing some speed wouldn't be so bad. Cost is still a concern.
On Wed, Feb 20, 2013 at 7:57 PM, Carter Quillen <twowheelinguy@yahoo.com> wrote:Followed the link to check it out. Nice battery and made in America, (mostly), to boot.Wish I had an extra $8 grande, I'd buy one tomorrow. Puts my 8 pack of Trojan T-125s to shame but since I only paid about a thousands bucks for an 8 kW pack I don't feel that bad. Looking forward to the day when you'll be able to buy Lithium for the cost of lead and it's coming. In mean time, I'll have to be content with my horse and buggy and wait for the model 'T's of batteries to hit the market.CarterFrom: James Sizemore <james@deny.org>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Cc: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Wednesday, February 20, 2013 7:24 PM
Subject: Re: [Electric Boats] Re: Converting a small trimaran to electric drive
Here is a 20kw lithium pack with bms and case for the below 8000, total package.Hi James,
I converted my 30' ketch to electric a few years ago and had the opportunity to convert my F-27 trimaran to electric when the old 2 stroke outboard gave up the ghost. After considerable analysis, it seemed that converting to electric would be too large of a hit to the sailing performance for the trade to slower motoring capabilities with considerably reduced motoring range, not to mention the cost. And this was with a LiFePO4 battery bank like the one that I installed in my ketch.
You didn't identify which type of trimaran that you've got, but I'm pretty familiar with a number of multihulls. First off, I'm going to guess that your typical motoring speed with the outboard is around 7kts with about 3/4 throttle. If this is true, then you could expect similar performance with a Torqeedo Cruise 4.0 (about $4000US) running at around 3.5-4kW. I believe that you would need the "high speed" prop, I think that the regular prop hits max speed around 6kts. In any case, you'll probably need close to the full 4kW to drive the boat past 6kts.
So 4kW at 50V is 80A. Let's guess that to go 6.5kts, the Torqeedo will take 75A, I'll base all the calculations on those figures.
If you used regular flooded lead acid (FLA) batteries, sixteen Trojan t-105 batteries would give you 22.5kWh of rated capacity, they would weigh 1000 lbs and cost about $2400US. Many people believe that FLA batteries should not be discharged past 60% on a regular basis, so your usable rated capacity is 13.5kWh. Now throw in Peukert's Effect (the loss of capacity due to high amp loads) using 1.25 as the Peukert's exponent and your 1000 lb battery pack will last 2.66 hours or a range of 17.3 nm on a full charge.
Using AGM batteries is better. if you had eight Odyssey PC1800 batteries, they would weigh 1060 lbs and cost about $5200. The rated capacity is 21.4 kWh but AGM can be discharged regularly to 70%, giving a usable rated capacity of 16.8kWh. AGM are less effected by Peukert's Effect and using 1.1 as the Peukert's exponent, this battery pack would last 4 hours giving you a range of 26nm on a full charge.
Now let's consider Lithium batteries. If you bought thirty two 200Ah Lithium cells, they would have a rated capacity of 20kWh, weigh 500 lbs and cost about $8500. LiFePO4 cells can be discharged to 80% on a regular basis giving a usable rated capacity if 16kWh and the Peukert's exponent is down to 1.03. Now your 500 lb (half the weight of lead) will last for 4.1 hours and give you a range of 26.6nm at 6.5kts.
You mentioned using your outboard to charge your traction bank. Your outboard probably produces 6-10A at 12V. If we use the more generous 10A, your total charging output would be 120W. If you could rectify that energy up to 48V nominal without losses (technically not possible but let's play along for the conversation) it would take at least 133 hours to replace the energy that you used in your 4 hour cruise. If you use a 2000W portable generator (50 lbs and about $1000) through an onboard charger (about $500), your max charging rate would be 1500W (probably less), and now it will only take about 11 hours to replace the energy that you used during your 4 hour cruise.
So ignoring the costs, how do you think that your boat will sail if you throw another 600 – 1200 lbs of driveline into it?
Because of the math, a two hour range allows you to cut the weight and costs in half, but you're still looking at 300-600 lbs and multis don't like the extra weight. And your cruise range under power is closer to 13nm. For a lot of money. That's why my F-27 has a new 4 stroke 9.8 gasoline outboard. Cheaper, simpler, much lighter, more powerful, greater range, etc. I struggled with the 30lb increase in changing from 2 stroke to 4 stroke, but you can't buy small 2 strokes in California any more.
I can do different calculations if you want to adjust your requirements (slower speed, shorter range) but you can see where this is heading. Feel free to ask for more info, I'm glad to share my experience. BTW I have heard of successful electric trimarans, but they have been in the 40'+ range, the larger boats are better equipped to carry the extra weight.
Fair winds and smooth seas,
Eric
1964 Bermuda 30 ketch, 5.5kW Propulsion Marine drive, 8kWh Lithium batteries
Marina del Rey, CA--- In mailto:electricboats%40yahoogroups.com, "jamesmccombs362" wrote:
>
> I am totally new to this electric concept, Mike, and would appreciate your opinion. I have a 31 foot trimaran at 6000 lbs. Currently I use a 9.9 outboard.
>
> What about keeping the outboard adding an electric motor and new prop (plenty of room for electric motor in the stern, enough battery power for 4- 6 hours cruising. Until litium prices come down I coould use the outboard to charge the batteries as it does now and make use of a genset for back up. ??? Any of this makes sense?
>
> Thanks in advance.
>
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