Originally Posted by argosail
I'm looking down the line to convert to electric a 27 to 30 ft monohull
around 7k to 9k. From the person I spoke to at the Annapolis boat show
, a 10ah system should work
with abt 300 watts solar for a good few hours a day.
Now I'm guessing the less wetted surface the better for getting longer range on electric, so I imagine a fin keel would be better than full. Does that make sense?
Regarding the shape, would a flat bottom equal less resistance as well or would a V-shape be more efficient?
Intended vessel would be for coastal cruising eastern seaboard and caribs.
I designed and built an electric propulsion system for my last boat, so I know what I speak of.
Repowering a 27 to 30 foot sailboat with EP is very smart. Under certain circumstances.
1. You already own the boat.
2. It has a dead or dying ICE engine
3. You use the boat mostly for day sailing
, weekending, and marina hopping coastal cruising.
4. You don't like to motor very much and you do not have to motor very much.
5. You know quite a lot about electricity, electronics
, motors and controllers, wiring
, particularly wiring
that must be able to carry very large current
, and BATTERIES. Don't mess with this if you are not a reasonably competent engineer
, even with a turnkey system.
I am not seeing how you are checking all of those boxes. If you just want to go EP because it is cool, don't. The novelty will wear off and there you are.
I repowered a Cal
2-27 for well under $3k, including batteries. I had been thinking about it because I was not exactly in love with my Atomic 4 gasoline engine. However, I could not justify it as long as the Atom Bomb still ran. When the fuel tank
sprang a major leak and spilled 15 gallons of gasoline into the bilge
, something had to be done. In order to remove the fuel tank
I had to either cut a huge hole in the boat, or pull the engine. I pulled the engine. While it was out, I started thinking about simply repowering. I had already done a lot of research
and had a pretty good idea of what components I would want and how to make them all play nicely together. So I cleaned everything up, got rid of all wiring, hosing, and piping related to the engine, sold
the old Atomic for $400 which actually brought the total cost down even more, and went ahead. I ended up with over 10kw/hrs storage and a 10kw motor that pushed the boat nicely, at a brisk pace for a short time, or at a very sedate pace for long enough to cross Lake Pontchartrain under power. You can have a reasonable size bank. You can have low cost. You can have high speed. You can have long(ish) range. You only get one or two of those, not all. The main limiting factor is the batteries, which are your fuel
tank. After studying the matter carefully I decided that GC-2 size golf cart batteries, 220ah capacity, bought from Sams Club for $85/each, were the best solution for me, for too many reasons to list here. Motor was Motenergy, originally a 5kw unit, later a 12k one. Controller was Kelly, originally square wave, later upgraded to a sine wave unit. Reduction gear
was a fully enclosed gearbox
but if I had to do it again I would do what most do, and use a belt drive.
I find turnkey systems horribly overpriced, and even having it installed professionally still elaves you with a propulsion system that you do not understand, and do not know how to maintain, troubleshoot, or even operate properly, if you are not well read in the subject.
is a great way to rescue
an old 70's built fiberglass
boat like what I had. Lots of these boats around being practically given away, with dead diesels or A-4's. EP offers tremendous advantages for small boats where motoring is not a priority and shore charging
is readily available. A resourceful DIY-er can do the conversion for about 1/3 what a new Beta diesel
costs. No fuel
to buy, smell, or spill. Quiet. Some systems are VERY quiet. No minimum idle speed, so you can ghost into your slip at just a few dozen RPM
, or glide by a placid shoreline and observe wildlife. Instant on, no warmup. No complicated start sequence, or crossing your fingers. The big bank necessitated by the propulsion motor can be quite useful for other things. Recharging such a big bank with 300w of solar isn't going to happen. But when you can just go out for a day of sailing or an overnight, return to your slip, and plug
in, that is a sweet deal.
If you want to go electric, first of all learn about electric. There really is a lot you should know, particularly about batteries. For instance, do you know how to manually equalize your FLA batteries? Probably not. It is rumored that there are smart chargers that will equalize, but I have seen NONE, ZERO, NADA, that will charge at the proper equalizing voltage. None. So you need to know how to do this manually. You need to know about charge algorithms, how to do Peukert calculations, how to water your batteries and why you don't want batteries that you don't have to water. You need to become an engineer
, basically. Then think about taking the plunge. Until then, you are quite frankly better off with a good outboard mount and a long shaft Tohatsu or Mariner on your 30' boat with the dead engine. Even so, you really need to know a few things about gasoline safety
as well as outboard operation and maintenance
The more you know, the less you fail. Learning
from your failures is hard, frustrating, and expensive, so learn as much as you can without the trial and error process before you play for keeps.
I like EP and have no regrets at all with the repower
, but it is not for everyone, and there are a lot of ways to screw up in designing, installing, or using it. The diesel
is mature technology and very well engineered, with plenty of competent service
people, and lots of excellent books
about them. EP has been around in a big way for about 140 years but still has not achieved the same status that the infernal combustion engine enjoys today. Be aware that it is a fringe technology and there are reasons why all boats are not electric. Outboards are very practical in the same set of circumstances that allow EP to shine, and they are like the diesel, familiar technology. Well, that is, if you are familiar with them.
Study, do your homework, and instead of looking for a boat to repower, just wait until you happen to own one that would be a good candidate. All standard sailboat hulls are of good shape for pushing with electric, so no worries about that.