Could someone check my math please?

[roland stockham]

Quote - We presently have 375 Ah of FLA for the house bank and 75 Ah FLA for the starter all charged off an internally regulated 55A alternator on our 90 hp diesel. - End quote
The first thing you must do is change the regulator. An internally regulated alternator is designed to safely maintain full charge in the batteries while powering other systems. Fine in a power boat or car. On a sail boat where batteries are cycled daily it does not produce enough voltage to recharge the batteries. You need an externally regulated 3 step controller that has a program for recharging FLA's. The generally recognized size is around 25% of the amp hour rating of your house bank which would be about 100A so your alternator is undersized and almost certainly so is the wiring that connects it to the battery. With these changes you will go from never fully charging the batteries and seeing them die of sulphation to having around 80A charging on bulk. Once you have effective charging then yes you either need to reduce your energy budget or increase the bank size. The ideal is to have 48hr worth of energy stored without running below 50%. This give a decent reserve to get you through fixing charging problems or times when you need extra power. For the energy budget I would start with the autopilot as there are lots of ways of reducing its power draw, increasing dead band, improving sail balance etc but it depends a lot on the boat.

[Na Mara]

Wow. Lots of good stuff here. Waterman46’s point about refrigeration is excellent and well taken. I took my consumption figures in Sweden so fair cop there.

I really like the davit idea. I was planning on just blowing up the dinghy as and when and then deflating it and stowing it in its “garage” under the forward berth. That works well for us with summer cruising with only occasional anchoring but I can see how it would get really old over the duration of a year cruise avoiding marinas.

I would never tow a dinghy except in an emergency. I have seen way to many cockups that began with a towed dinghy.

And I can see how nice framed high quality panels over the davits would be relatively free of shade, out of the way, and would also protect the dinghy and partially shade the swim platform. Hell I could mount a shower head holder on it and use it to aid showering on swimstep which I think is just the greatest luxury. I can even accept hscrugby’s point that such a thing might be made aesthetically chic in a functionalist kind of way. However I’m sitting In my cockpit and I am struggling to see how to do it.

As you can see from the picture, the entrance to the swim platform is set quite far off to starboard and there is not much that can be done about that. Either the starboard davit goes right up against the pole with the radar on it or it goes very close to the centerline. In the latter case that would necessitate having the whole assembly asymmetrically off to port. Not very attractive or practical. In the former case it would mean the davits are spaced five feet apart. Maybe that’s a fine spacing for davits but it looks a bit wide to me. It would give me a big platform for panels though so it might work. Even so access to the swim step will be a little tighter than it is at present.

An arch is out as it would be major surgery, it would increase the airdraft with mast down (which is a problem for multiple reasons I won’t bore you with, the present pole folds down). I like the radar where it is as I can gimbal it manually to a fixed position by just reaching up from the helm, and I hate radars on masts (had several before and they always caught lines and worsened rolling).

If I also needed a Bimini then I could maybe see the point of an arch but Na Mara is a true pilot house with great ventilation. If it gets hot the pilot house roof is our bimini. Basically an arch is a sledge hammer to crack a nut in our case.

I have already come to the option that I will need more battery capacity and that my original estimate was low. Also I think I may be going to lithium for the big trip rather than just adding more FLA.

But no matter what I do with the solar panels I am going to need more, and more reliable, charging for underway. I need 200Ah a day over a four week period for the crossings guaranteed. The only thing that gives me that is the Watt and Sea, a fat alternator, a fuel cell, or a generator. Not doing a generator as one ICE on a sail boat is practical necessity, two and you might as well buy a trawler. Fuel cells are neat but their life expectancy is crap and they are as much as the hydro generator. I don’t like running the engine to power my electronics for sailing as it’s sort of admitting defeat. So that just leaves the watt and sea. Yes it’s an expensive extra set of holes in the hull most of the time, but being able to power the auto and instruments indefinitely on long trips without resorting to the engine is priceless for me.

It does however leave me short at anchor so I do need solar as well. I think I’ll talk to my guys and try and get something along the davit line sorted out. I’m now going to google image the hell out of it for inspiration.

Cheers and thanks from Na Mara

[Noisykate]

Just a suggestion - it may also be useful to look at the consumption side of the equation.

A hydrovane or aries self-steering system would eliminate the draw of the hydraulic steering system.
We also managed 2 atlantic crossings with no freezer. It can be done - fresh food all the way both times...
Also, we switched off most of our instrumentation most of the time, except AIS. Switch radar and charts on when you need them.

[Na Mara]

As to the external regulator and alternator we just had to replace our alternator in a hurry because of engine troubles and it was a PITA sourcing a new one that would fit the mounts on the engine. I did ask if they could source a bigger one without an internal regulator and it was a no go.

Do you know Roland where I can get a 100+ Amp alternator without internal regulator that will fit a yanmar 4JH2 DBTE engine from 96?

[Na Mara]

noisky,

I can see us doing without radar, instruments and one of the plotters. But the other one is needed for AIS reception and weather info. No refrigerator might also be doable, but the auto pilot is essential. I’ve looked into hydrovanes and discounted them. We have a wraparound helm with a table on its back side. To fit the lines for the hydro and we would have to loose the nice table. Also, I want to fully use my pilot house and that means being able to make steering modifications from below. Can’t do that with the hydrovane. Finally I just don’t like the look of them on sugar scoop boats like mine. On classic reverse transom they look the business but on scoops they just look wrong.

But it was a good suggestion and if I had a classic sterned Malö or rustler without pilothouse I’d have taken your advice.

[carstenb]

Originally Posted by Na Mara

As to the external regulator and alternator we just had to replace our alternator in a hurry because of engine troubles and it was a PITA sourcing a new one that would fit the mounts on the engine. I did ask if they could source a bigger one without an internal regulator and it was a no go.

Do you know Roland where I can get a 100+ Amp alternator without internal regulator that will fit a yanmar 4JH2 DBTE engine from 96?

try mark Grasser

https://markgrasser.com/

I sourced a 160amp alternator plus new belts/pulleys etc & sophisticated regulator - best money I ever spent -

But you really should look at getting an arch. The davits alone will save you god awful hours of screwing around with pumping up the dinghy. Our 700W panels sit on our arch and don't bother us at all. Our radar is mounted right at the middle of the panels. The panels are wired series/parallel so the shadow only cuts out the charging on one side not both

[Na Mara]

Looked at the grasser site and it looks good but

1 does he export to Sweden and

2 I would need to check these for our mounts.

But good tip.

[carstenb]

Originally Posted by Na Mara

Looked at the grassed site and it looks good but 1 does he export to Sweden and 2 I would need to check that these for our mounts. But good tip.

1- yes he exports to sweden (he exported to me in denmark)

2- he manufactures the mounts to fit your engine - he makes these mounts himself - so you get a box with a regulator, custom made mounts and pulleys. a serpentine belt, an alternator and a regulator.

you need to buy some wiring and hook it all up. Took me most of a day.

[Na Mara]

Excellent. I will definitely be following this up.

Thanks

[Hesti]

Nav lights are LED? Bulbs in lights below deck are replaced with LED? It is surprising how much traditional bulbs take. Stereo - on our boat, there is a car stereo. Amazing how much electricity that thing takes.

[hscrugby]

My super fancy drawing of where I would put the rear solar.
This would kick over the transom about 4' total, give or take, and you could probably even fit 3 large panels. Just have a second pole on the port side, tie into the radar pole, and you're golden. the diagnol supports for strength, and should be super easy and "cheap" to add, then you could fit plenty of solar and have some shade on the scoop.


IF you wanted to beef it up more, then tie it in, reinforce the radar support etc, and then you'd have a place to lift a dinghy, AND keep the dinghy out of a lot of the sun from solar. (I've yet to talk to anyone that regretted adding more solar and said "man, I really wish I hadn't added that extra 600w of solar" to their camper, boat, house, garage, hunting shed, etc. I HAVE talked to tons that said "I really wish I HAD added another 300/500/1000w of solar"

[carstenb]

I like the drawing and it shows what you should do - get it made beefy and you can hang your dinghy.

regarding your owed generator ......................

I'm going to tell you the best kept secret in cruising. No one else will tell you this. No one will mention it unless they have unimaginable amounts of either G&T or rum. They will deny ever having told you. You will not find it written down anywhere.

I will most certainly be ostracized and drummed out of the cruising community, banished to exile for life for telling you this.

(gulp) here goes:

When you are sailing passages, you will spend more time becalmed that you ever will in heavy weather.

Thinking back on our passages, we've probably spent about 30% of our sailing time either becalmed or with winds less than 7-8 knots. At 7-8 knots from behind - guess what - you ain't moving or if you are then it is at say 2 knots.

This means that a towed generator won't produce dittily squat. As a matter of fact, it will slow you down even further.

buy solar, not towed arrays

[carstenb]

by the way - a good inverter will allow you to have an ice cube making machine on board. Mine cost me about $150 and makes 9 ice cubes every 6 minutes after it gets going. I pulls about 9amp at 12VDC when running. (90 amps at 220VAC)

You will find that an ice cube making machine is probably the best investment you have ever made (warm G&Ts taste god awful)

[hscrugby]

I just went to to Aldi's to get an ice cube maker that was supposed to be on sale and 12v (wall wart to go from 110) it was neither. Sigh.

[leftbrainstuff]

Originally Posted by Na Mara

Thanks all for the very valuable input!

Aside from a difference of opinion about the usefulness of wind, which we aren’t going to do due to noise in the master cabin, you all pretty much agree that my calculation on the solar panel is optimistic (it should be between 8Ah a day in winter and 40 in the summer) and that my figures for usage are a little low (I forgot about winter needs and generation). Say 200Ah a day for sailing worst case and 100 Ah a day at anchor in colder climes (I forgot about forced air heating).

I had already figured out that avoiding any need for inverters was the way to go but it’s nice to hear real world experience confirming that. The only real sacrifice this entails for us is hot water for showering is limited to a day or two after we run the engine or to minimal 5 liter showers using a camping shower heated by the sun or water from the stove. We can live with that.

Beyond fitting a refleks stove or similar (I have no where to put one of these) we aren’t going to be able to reduce our at anchor usage much and at sail usage is pretty fixed.

So going back through the numbers after what has been said. I need to distinguish two scenarios and cover both. 1 winter cruising in the northern latitudes and 2. summer cruising around the equator. In the latter case my figures and strategy work out. Our usage will be about 300Ah+-50 between trips and we will meet this with the setup proposed. However, during winter in the North we will need more like 600Ah between trips and we will only generate 300Ah on the proposed setup. In this latter scenario, adding solar won’t help much according to leftbrain

To cover life on the diesel heater when we go north we need about 100 Ah a day at anchor.

My choices to meet that need seem to be.

1 fit a diesel generator.
2 fit a wind generator (it’s windy in the winter months in the north but even so that might not be enough)
3 add a second alternator to the engine ( loosing 4 hp to a 160 Amp alternator out of 90 ain’t going to kill me as carstenb points out)
4 Fit another pod.

Option 1 is a non starter. I have space in the engine bay for a generator so it would be relatively quiet, but I don’t see the point in lugging around two ICE’s when the existing one is man enough.

I’m loathed to do option two as too many people have shared leftbrains opinion that they don’t give you much bang for buck or for that matter the noise and nuisance they represent.

That leaves upgrading the alternator so I can put 100-150 amps back into the bank when running the engine and or doubling the pods.

Doubling the pods would let me generate around 500Ah on a normal 10hr hop. Adding an alternator would also let me generate about 500Ah on a typical 10 hr trip in conjunction with the single pod. Either would meet the trip and anchorage needs even on the worst case if we can stow all that energy. I’m minded to do a second pod rather than the second alternator but that will cost 2-3 times the alternator.

Either way I will need about 400 Ah of usable electrical stowage as with this set up we will be generating hardly anything when stopped In northern climes. My 600Ah bank won’t be big enough. I’ll need to go to 900Ah by my reckoning.

So second alternator or second watt and sea pod? Which would you pick and why?

Upping your alternator capacity is low risk and lets you choose when you make power.

Make sure you include some good monitoring. This will help you identify actual consumption, let you find and remove parasitic loads.

It can take a bit of trial and error to match your actual multi stage charging strategy to your boat. Include a good modern, adjustable multi stage alternator regulator.

Personally I'd go for a cheap automotive alternator and spend more on my regulator. But temperature sensing will be needed too.