Cal 40, Aurora Electric Yacht Conversion!
It was a fortunate day in February 2008. Fortunate because hull number 82 of the legendary Cal 40 came my way and fortunate too because she came without an auxiliary. The diesel had expired and lay ashore somewhere waiting for yet another rebuild and more. Having had a couple of less than pleasant experiences with diesel motors in previous boats I had developed a phobia, an allergy even, to those belching complications. Normally I would go engineless or clamp an outboard on the stern but the Cal 40 was somewhat large and I did not want to remove a very useful Monitor vane to make way for an OMC. What to do?
I had heard of electric motors for sailboats but the task seemed daunting because I am a mechanical klutz and also with the boat in Malaysia and the electric units available only overseas, it appeared a mission impossible. Anyway, I plugged away on the Internet and on an off chance, sent an email to Electric Yacht and as they say, “the rest is history.”
Scott McMillan immediately came to grips with the complication of installing an electric motor in the Cal 40. The motor needed to sit backwards and down into the pan which housed the v-drive. It would be tight. Measurements and details went back and forth for a while. Amazingly all my concerns were addressed, all emails were answered and I knew this guy was several steps ahead of me. But was it doable? Scott thought the dimensions might work but was concerned the 48 volt system was too small for my boat, being 15500 lbs displacement on a 30’04” waterline length. The decision was mine. I knew I was in good hands and put trepidations aside and mailed a check for the deposit. It was done.
There was a delivery backlog which gave me time to remove the old tank and its 110 litres(29galls) of diesel, get rid of forty years of crud and grime and cut out the v-drive with an angle grinder. White paint followed and the bilge shone. Scott sent me a photo of my unit with the super short shaft and pretty soon a hefty parcel arrived at RLYC Langkawi. Duty free, of course.
Custom built motor, throttle, percent meter, master switch, 48 to 12 volt converter, custom cableing for the batteries and the controller which Scott had built separately so it would’nt get wet at the companionway foot, detailed instructions ; it was all there. He’d even upgraded me to a dual 48/72 volt system, in case I should need it.
Often times things just fall in place. My South African friend, Faith offered to help. A piece of 2 by 4 drifted by and made a stong back from which to hang the motor on a handy billy and within a week it was all hooked up. No engineering, no dry dock.
Fortunately Trojan T105 batteries are available in Langkawi and with the help of a two young and strong Burmese workers we placed them in the space where the diesel used to sit. Not exactly level but secure and unable to come adrift at sea.
Now for the results:
Conditions; no wind, flat calm, runs up and down tide and averaged. GPS speed.
1.1 knots @ 4 amps,
1.93 knots @ 11 amps,
4.0 knots @ 72 amps.
LOA ———————– 39’04”
LWL ———————- 30’04”
Long fin, spade rudder, flat sections.
The motor limit comes on at 75 amps. The pitch is not quite right. It should go to 100 amps which may deliver another half knot and give a little more torque. The extra pulley Scott sent along for the 72 volt system may do the trick and I will swap it around soon. Otherwise I will have to adjust the Max Prop (self feathering) at next dry docking. Manoeuvering with the electric motor is a snap. Plenty of torque and of course no noise, no smoke. I charge up the batteries from shorepower at the marina via a battery charger. It’s only pennies.
I have been in and out of the marina twice and the batteries are down 10%. When I extrapolate the data I come up with an endurance of 20 miles to a 50% discharge level and 30 miles to a 75% discharge level. Underway I will charge the batteries from the Air Marine wind mill; solar panels via Zahn’s 12 to 48 volt optimizer. Another option is to change to a fixed propeller which would let the regen work on passage but the price is high; 15% loss could add up to a 30 mile a day deficit. There is a good chance I can do it all without buying a generator.which like the diesel is a step in the wrong direction.
Weight comparison might be of interest:
Perkins 4.107, Walter v-drive, full lube oil and bunkers, 4 Trojan T105, 1 starting battery, exhaust/cooling paraphanelia
Total approx weight…………………………555kgs(1228lbs)
Electric Yacht motor complete, 8 Trojan T105 batteries, Battery charger.
Total approx weight…………………………258kgs(567lbs)
That’s it. I wish you, “Good sailing”. With emphasis on sailing. Ben Lexcen’s famous edict, “Fast is fun” got it right. Sailing is; motoring is not. Electric Yacht is a happy compromise.