Hi Innes,
Yep we all want it all, quiet, clean performance with free energy and a low, low purchase price. But it really doesn't work out that way.
Concerning prices, the assembled drive systems are not much more expensive than buying "all of the bits", I don't think that the vendors that visit this site are operating with more than a 25% mark up on their goods. What you get for that mark up is a tried and true solution that is appropriate for your boat, one that has already gone through multiple rounds of trial and error. The vendors also provide support after your purchase, helping you solve the issues that will inevitably crop up during your installation.
Or you can buy one of the "kits" online. They are cheaper, but they leave more of the engineering to your expertise with electric boat conversions. You get some of the major components and then you're on your own. Some people here have made it work right the first time, other have purchased multiple versions of similar components as they learned what worked and what didn't.
Or you can source each component seperately. That's where previous experience really helps. Some folks would rather tinker than sail, I'm more interested in sailing.
I built a number of electric cars in the 1990's. I've built a number of small boats and refurbished some larger ones. When it came time for me to repower my 30' ketch, my experience led me to purchase a complete drive from Propulsion Marine in Santa Barbara, CA. With the boat operating beyond my expectations, I believe that my money was well spent. The installation was quicker and easier, and I only had to do it once. With what I know now, I could easily build a drive from scratch, but I would probably still buy a complete drive solution for the time savings and support.
Talking about regenerative charging, you're just not going to get much in a boat that small. We've had many discussion about the topic here, and the bottom line is that regen barely starts around 5kts. With a 17' LWL, your hull speed is less than 5.4kts and I would assume that your typical sailing speed has been 4.5 to 5kts on good days. Add in that you want a folding prop (which are worse at collecting regen) and I would be surprised if you ever saw 20W coming in from your driveline and that would be in 20+kts of wind. For a reference point, my 30' ketch with a fixed 4 blade propeller has generated almost 60W momentarily while sailing around 6kts. At 5kts, I get no charging current at all.
Hopefully, I helped adjust your expectations. As for picking a drive that is the right size for your boat, our guideline is 1kW of drive per ton of displacement, so your Hurley 22 with 3900# of displacement works out to a 2kW drive. You can put in bigger for more money, but your boat doesn't really need it. I would check out the Mark II B drive from Advanced Marine electric Propulsion, it's a very clean 2kW drive that should be excellent for your boat.
I'm just a member here, I don't sell electric boat gear. But I have accumulated a little bit of experience over the last few years, so you can take my advice for what it's worth. I will say that as one of the stronger proponents for electric sailboats, I know that they are not the right answer for everyone. I did not convert my 27' F-27 trimaran when I had the chance.
In any case, good luck with your project.
Fair winds,
Eric
1964 Cheoy Lee Bermuda 30, 5.5kW Propulsion Marine drive, 8kWh lithium batteries
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Innes" <innesgshutton@...> wrote:
>
> Hello All,
>
> I've just joined this group with a view to finding out a bit more about electric drive systems for boats. More specifically I'm looking to build an electric inboard to power my Hurley 22 sailboat. It needs to be comparable to an 8hp motor and be capable of recharging batteries when sailing, and have self folding prop(to reduce drag) when sailing but not charging I have looked at full kits on the net for sale but they all seem to be rip-off prices! I am not an electrical expert but if I had a plan with a listing of all the bits necessary, I think I could fit this myself. Any ideas anybody?
>
> cheers from Scotland,
> Innes.
>
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