I can now say that we have extensively sea trialed the Manta Drive. We started with a little trip around Lake Union then stepped it up to a few overnight cruises.
First Trial – Cruise on Lake Union
Ava and I motored off the dock one faithful summer night here on Lake Union to test her out. I completed tightening the bolts holding the belt tension and said, “Alright! let’s take her out!” Ava looked down at me skeptically from the cockpit. The sun had set, so it was going to be a nice night time trial cruise, maybe 30 minutes or so.
The first thing I noticed was how responsive the boat was, I can now turn the propeller at 1 rpm if I so choose. This is a very nice perk for backing Cinderella out of the slip. I could use quick bursts to overcome wind drift and keep the bow under control, yet go back to a very cautious slow speed in an instant. This was not the case with the Yanmar, the Yanmar did not like shifting from neutral to reverse, and would die occasionally during the shift. This kept me on high alert in close quarters, and I tended to over throttle to compensate making close quarters tricky. (To enter and leave the slip I have to slide Cinderella between two boats with about a foot on either side, and the same goes for reversing out of the slip)
We then proceeded to motor around the lake and I let Ava take the helm so I could go below and look at the gauges, I could not believe that under full throttle, not only were we hitting 5 kts (the same max speed as the Yanmar), but we were only drawing 25 amps! I was expecting closer to 100, so this was huge. Backing her down to 10 amps Cindy would hover right around 3 kts. I was taken aback by how little energy this was taking (though I shouldn’t be too shocked, I managed to row the boat to 1kt when we were out of wind Sailing around Canada). Let me tell you, the motor sure beats rowing!
At full throttle, the belt was slipping and smoking. There was no trouble motoring around at 3kts, but if we pushed it, the belt would slip and smoke. I first wrote it off as bad tension, but on further inspection I was sold a A type drive pulley and a B type driven pulley from the bearing house. The B type belt was not getting enough purchase on the A type pulley and slipping under load. I called McGuire Bearing here in Seattle, and they remedied the situation by swapping my pulley at no charge. The belt no longer slips under a load, and all is well.
Next Trial – Afternoon of crabbing, and a day sail to Poulsbo
The first decent cruise with the Manta Drive was to Poulsbo, WA with 5 friends aboard. 3 of us had the afternoon free, so we headed out the lock early to do some crabbing until the rest of the group could get free. At this point I was completely unsure of the range of my battery bank. To get through the locks out of the lake and into the Puget Sound its about an hour trip, and I bought the cheapest batteries you can find, they aren’t even full deep cycle batteries, but the plan is to test inexpensively and upgrade prior to departure.
We sailed most of the way to the locks, only motoring under the two bridges and through the locks themselves. It was a beautiful summer day, and we were tacking like crazy to get up the canals and across the bays. The wind was perfect 15 kts or so, so we played around setting the crab traps and retrieving them while under sail. (This was actually good practice for a MOB drill, knowing how to heave to where you want to, and how the boat reacts). After a delicious crab lunch, we headed to Shilshole Marina to pick up the rest of the crew for the trip. I still had only motored the boat for a grand total of maybe 30- 40 minutes and had 67% of my battery bank remaining.
After picking up the crew, we sailed on towards Poulsbo (approx a 17nm trip), but the wind decided to stop just as the sun was setting with about 4 miles remaining to the destination. We were out of the strongest current area of Agate Pass, but we were going to fight a slight current most of the way there. Based on my rough calculations, we did not have enough battery remaining to make it…. We motored slowly for about an hour until the battery was toast. Unfortunately, I did not really pay attention to the amps or the time, so I am not entirely sure of the capacity of the bank. We drifted close enough to shore to drop anchor and everyone crashed out for the night.
I spent the night in the cockpit fearful of the anchor. I was not able to set it adrift, so as soon as the wind picked up I was going to weigh anchor and set sail. Sure enough, I awoke around 6am to a very slow dragging of the anchor, and I hoisted the sails and headed out before the crew woke up. The wind was gentile, and I sailed under main alone back out Agate pass. My plan was to sail slowly and arrive at the pass just as the current started build into an ebb. After we got out the pass I again dropped anchor, this time along with crab pots and went back to sleep for a few more hours.
When we all woke up, I told everyone of the new plan to sail to Kingston due to my fear of losing wind in Poulsbo again and not getting back to Seattle on time. We continued on and the wind was perfect, 15kts and Cinderella was charging along at 6kts to windward, the perfect time to test out the regeneration from the propeller. I gave the motor a quick burst in reverse to open up my folding prop, and put the motor back in “neutral”. The prop was now spinning and recharging my battery bank. We sailed on for about an hour alongside a half dozen orcas playing all the way to Kingston.
Upon arrival, I was unsure how much battery I had to dock. I decided to come in under sail, and use the motor only minimally to stop us neatly at the dock. (It’s also fun to engage a bunch of non-sailors in the group challenge of dropping sails on command while coming into a marina). The motor performed admirably stopping our forward motion at the dock. I again didn’t have the for-thought to check the charge level of the bank when we arrived, this was the first time using regen on the motor, and my regen amp gauge wasn’t hooked up yet, so I couldn’t get a good feel for how much power was going back into the batteries.
I paid for a few hours at the marina in Kingston and plugged into shore power to recharge the bank. We wandered around, had lunch and set sail again to Seattle. After dropping everyone off, I motored back through the locks, all the way back to my slip, about an hour and a half of motoring, and there was still plenty left, at this point, I was pretty happy with the motor. I could get out of the locks from my slip, and the regen seemed to work enough to handle docking in a marina. I called it a win even though I drained the batteries to dead on the trip.
Remaining Trials – A couple cruises and a few races
Over the course of the late summer, fall, and so far this winter I have taken a handful of trips to further my understanding of this new electric motor drive. We entered a Duck Dodge race last minute, I participated in the Race Your House, and attempted to first of the Snowbird Series. The latter two showed me that I have right about 3 hrs worth of usable motoring on my battery bank at about 3-4kts, just enough to get out of the locks and back into my slip. We also cruised a bit further to Port Ludlow (again anchoring when the wind died to sleep for a few hours) and later to Port Townsend over Thanksgiving (through a gale on the way there, and navigating micro wind bursts on the way back)
Manta Drive Overall
I am happy with the manta drive, it serves the purpose I wanted when I came up with the idea. I have a simple, clean drive system with no maintenance, and very minimal points of failure. I can motor into the Sound and back from my slip, and I have opened up my cabin allowing for me to build a better layout for our living space.
1 – I can drive the boat the the same max speed as I could with the yanmar (I believe this can be bettered by modifying the propeller)
2 – I have a bout 3 hours of motoring available or approx a 9 mile range as a slow cruise with the cheapest batteries on the market (after upgrading to Oasis Firefly’s we should have about 4x the range) 12 hrs is going to be plenty for what we plan to do with Cinderella
3 – Regen seems to work well, I was able to charge my battery from 57 to 75% over the course of a couple of hrs worth of sailing. I still have an issue where the controller stops the motor if we sail too fast which is kind of annoying, but I am sure there is an easy solution.
4 – I was able to repurpose the seacock for the engine water inlet for my sink drain along with regain lots of room in the boat.
5 – NO MAINTENANCE!! Being a permanent magnet DC brushed motor, the only maintenance I may have to worry about are changing a belt if it wears out, changing brushes if they ever wear out, or changing the motor bearings if the wear out. 3 simple parts that I can carry in about 1 L of space. I won’t need spare alternators, starters, exhaust fittings, fuel filters, gaskets, pump impellers, and so on. The best part is that the components I may need can be easily be found anywhere in the world as they are standard parts used in many different applications.