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Old 30-07-2020, 17:04   #31
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Re: Could someone check my math please?

$129 from amazon - 110VDC, needs inverter to go 12VDC

https://www.amazon.com/Igloo-ICEB26A...s%2C377&sr=8-9


tons more on amazon for between $130 and $190
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Old 30-07-2020, 17:11   #32
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Re: Could someone check my math please?

Quote:
Originally Posted by carstenb View Post
You need to be aware that in daily use - FLA batteries shouldn't be run down more than about 25-30% - so your 600AH is, in reality, only 175 aH at best. AGM batteries will let you run them down to say 35% maybe 40%(but not every day).

There are some new batteries, Firefly, i believe that claim you can run them down a lot further but I'm not personally familiar with them. Lith-iron batteries will let you run them way down - much more bang for your buck.

There is nothing wrong with having an inverter (we have a 2000W) as long as you use it intelligently.

Were it me - I'd ramp up as much solar as I could and add the big generator. Solar requires almost no maintenance. we've sailed around in Scotland and now in the PNW and the solar charges our system just fine. ON really cloudy days, we have to fire up the engine for about a half hour to an hour. If you use the engine you also get hot water.
We ran Firefly Carbon Foam batts for several years. Twice the usable capacity than FLA because you can run them down very low. They don't sulfate so you can abuse them a lot.

The price per usable Ahr (not brochure max) came out even with Trojans. We had 400Ahr of Trojans and the same in Fireflys but you can run the Fireflys way below 50%. This gives you double usable capacity.

We actually got 10 years out of our Trojans but heating hot water killed them quickly. No problem with the Fireflys. They handle high rate discharges much better than FLA or any of the traditional lead plate sealed FLAs except for big expensive and very heavy 8Ds.
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Old 30-07-2020, 17:14   #33
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Re: Could someone check my math please?

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We ran Firefly Carbon Foam batts for several years. Twice the usable capacity than FLA because you can run them down very low. They don't sulfate so you can abuse them a lot.

The price per usable Ahr (not brochure max) came out even with Trojans. We had 400Ahr of Trojans and the same in Fireflys but you can run the Fireflys way below 50%. This gives you double usable capacity.

We actually got 10 years out of our Trojans but heating hot water killed them quickly. No problem with the Fireflys. They handle high rate discharges much better than FLA or any of the traditional lead plate sealed FLAs except for big expensive and very heavy 8Ds.
How would you rate them $ to $ per usable Ah against lith-i(r)on?
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Old 30-07-2020, 17:24   #34
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Re: Could someone check my math please?

I would buy an wind vane">Aries wind vane system, or a Cape Horn. Both are held in high esteem by deep water sailors, but in really tough conditions, the Cape Horn might be my choice. Both have specific advantages worth investigation. They save HUGE amounts of battery energy.

I am sorry about the crappy post, but this is not how it appears in the edit screen.
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Old 30-07-2020, 21:56   #35
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Re: Could someone check my math please?

Na Mara,
Well, color me a little confused here (and I'm a darn smart guy).... LOL

And, there is a lot to unpack from your post / questions....so, please bear with me for a minute as I unpack / decode some things, that will allow me (and others here) to better help.


Seriously, I will get to your questions/answers in just a sec....but, just want to give you a bit of background info and ask you for a clarification up front.



1) I professionally designed/sold/installed my first solar array/off-grid system (on land) in 1984....and had been playing with solar/alt energy for a few years before that....and in the late 80's/early 90's stated working on solar installs on some boats....


I designed/installed my current solar array on my current boat, in 2006....and I still keep up with changes/improvements in solar technology, etc...


http://www.c470.jerodisys.com/470pix/47004.htm



I also installed (and still use) a water-generator to use when at sea on passages (usually only when cloudy/overcast)....and while it's certainly secondary to solar, it does work and does serve a purpose, particularly on long passages...


http://www.c470.jerodisys.com/470pix/47074.htm

https://hamiltonferris.com/images/pdf/pdf_359.pdf


SO...
In addition to my professional background in communications/engineering, I have experience with both solar and water-generators on boats as well...so, I'd like to offer a bit more than checking your math.

{And, to be clear, the biggest issue I saw right up front with your math, was that you're assuming some things about energy generation (and consumption) that is not consistent / repeatable (which effects the math) and you're combing A/H's (what you're representing as Ah's) with A/H's per-day, etc., which also effects your math....see below for some details.}





2) A North Atlantic circuit / circle is something I've done multiple times, and understand well....sailing from US to Europe....and back from Europe to US/Caribbean....having done my first crossing decades ago (in the pre-GPS days, when we used a sextant and DR), and my most recent crossings on my current boat, just a few years back.
BUT...

But, I think we may be referring to two different things, as you mention sailing between anchorages? Nowhere to "anchor" in the middle of the North Atlantic....so, I suspect that you're writing about coastal sailing? Or are there language issues confusing me?

So, could you please let us know where you are located, where you are planning on sailing, and just as important, when you will be sailing in these areas....('cuz sun angles, and hours of daylight, vary greatly in different areas during the year....as well as ambient temps / water temps, effecting refrigeration energy consumption.)



3) As you can see, I have both the professional/engineering experience and the offshore sailing experience, with solar and water-generators....
So, I hope you will take my generic recommendations/advice seriously? (and then we can discuss / help with your specifics)



a) Install as much "unshaded" solar panels as you can afford, and as much as you can fit on-board....(also allow adequate ventilation under / around the panels, as their output drops off when they get hot)

{Since you mentioned the "Watt & Sea" water-gen, I'm assuming you have a decent budget to work with? So, I highly recommend SunPower panels.....the SunPower X-22 panels, such as the X-22 360 watt panel is 41" x 61", and because of their cell design is not only very efficient but also produces more power at lower sun angles, which translates to more power per day....more A/H's per-day...so, go with Sunpower panels and one or two Morningstar MPPT controllers, and you'll be very happy....and you'll save many $$$$ versus buying/installing a watt & sea system or two!}

b) Make sure you reduce/eliminate any shading of the panels....(a small/minor shadow from a stay or halyard is usually not a major problem, but shading is a big problem)

c) Use quality MPPT controller(s) (Blue Sky or Morningstar)

d) Improve insulation of your refrigerator (and freezer, if so equipped)...reducing energy consumption

e) Manage sail trim / helm balance, as best as you can (improve as much as you can) reducing autopilot energy consumption.


If you do those simple things, along with a decently sized battery bank (larger than you have now), it's highly likely that you'll be 100% (or at least 90%) energy independent, meaning no diesel needs to burn for you to sail for days (or weeks) and relax at anchor for days/weeks as well....at least with good sun angles of summertime (or wintertime in lower latitudes)



4) Those are the generic recommendations, that apply to 99% of sailors out here... and now, here are some specifics (but these depend on where / when you're sailing?)....


a) You don't need to build an "arch", nor do you need davits to mount panels on (although, if you are thinking of davits, they do make a good place to mount solar panels)....but, you can use the space you have more effectively....first off, remove / move the TV antenna that is on your radar pole....you will find it will work just as well if you move it a foot below the radar scanner, or even on the stern rail...

Then move the GPS antenna / receiver outboard, place the GPS antenna on the TV antennas old mounting....

This gives you a nice open/clean space to work with, in order to better design a solar array....with your radar scanner being the one thing to design around to keep the panels from being adversely shaded (usually by placing the panels/array at this same height of the radar scanner).



b) Your pictures do not show much of your boat, and you've not said what boat, so it's difficult to say....but, it appears that you do have room above the helm area, aft of the boom, for a decent sized solar array?

Even if some of the array extends forward, so some of it is under the boom, as long as you move the boom outboard a bit (not close-hauled), you would avoid boom-shading?

Although, you would have some minor shadow from your backstays, if you use two panels here (one on each side) in parallel, or two panels each with their own controller (the best approach) these would have little effect on array output...

{note that if you used only one panel there, and then had two shadows on it, the output would probably be measurably effected.....please understand that this is something that many/most "professionals" in the alternative energy business know little, to nothing, about....and neither do most sailors....and here again, is another reason why it is VERY difficult to make specific recommendations for a boat we know nothing about... }



c) If you don't mind a small aesthetic effect, it appears you could place a decent sized array, aft of your helm / above the transom area?

Using your radar pole as the starboard-side support (with some added hardware / brackets), and then adding another "pole"/support on the port-side? Keeping the panels up high, so that the radar scanner itself would only shadow the panel(s) when sun angles are very low?


Or...or depending on the space you have (I have NO idea, as I don't know your boat), you could have panels here (aft of the helm / aft of the backstays) AND other panels above the helm area (forward of the backstays), as I described above in "b"...



d) Take note that rigid panels (of reputable manufacture, usually not made-in-China) will not only be more efficient than flexible panels, but they also last a LOT longer! (some with flexible or semi-flexible panels find they get 5 years out of the, but many find they only 2 to 3 years, before serious power degradation or total failure....those with good-quality rigid panels typically get decades of life....and Sunpower panels have 25 year warranties where they guarantee spec'd output at specific ages....fyi, Kyocera does this too....but it's darn hard to find Kyocera panels these days....)
So...

So, while many folks these days have jumped on the "flexible panel" bandwagon, usually this is a diminishing return....and many regret it....fyi, those race boats you see plastered with flexible panels have repair/services crews in various ports to repair/replace things, we cruising sailors don't!

And, we just want something that works, works 24/7/365, for years! And, that means high-quality rigid panels (Sunpower, Kyocera, Sanyo, Shell / Seimens, etc.)...

So, again not knowing your boat nor the dimensions you have to work with....nor the constraints you have regarding aesthetics...nor even the most important variable, your budget for all of this....it makes it very difficult to make specific suggestions....except for the above recommendations, and the strong advice here to use rigid panels...



e) Now, for someone (me) that has successfully used a water-generator on passages, you may be wondering why I haven't mentioned this as a priority?

The answer is four-fold:
--- Solar is much better overall....a decent-sized solar array (and good quality MPPT controller) will produce more power in a day than you will typically get from a water-gen (unless you sail at 10+ kts, and its always cloudy where you sail)



--- A water-generator only works when moving (and no matter what watt&sea says you will only see significant power at speeds of 4 kts and higher....and please figure about 60% to 70% of their factory output specs, as your actual real output...so figure about 6amps at 5 kts, and 7 - 8 amps at 6 to 7 kts...so, let's just be generous and say you'd get 6 to 8 amps for 24 hours, that's ~ 150 to 190 A/H's per-day....you'd get that much from a decently-installed solar array of ~ 360 to 450 watts...please read my article I wrote a while back, referenced above...)


--- Solar is maintenance-free....all you need to do is splash some water on them from time to time, and wipe off any bird-poop....and they will last you a couple decades or more, with no issues at all!



--- Solar is silent.....now, you think a water-generator would be quiet, too....but, it's not... Depending on how it's mounted/installed, you can find it a bit noisy (mostly vibration)....understand that the "towed-water-generators" (like I have) have much less vibration issues, as the prop is 75' aft of the boat, and the line connecting it to the transom-mounted motor/generator absorbs most of the surges/vibrations....


Now, I'm not saying a water-generator is bad....but they should always be secondary to solar....and the Watt & Sea is notoriously a maintenance issue....ask around, and you'll find many that have found the mounting / hinge system to be prone to early failure (within months) as well as other issues....

(as well as it being wicked expensive....the "300" model is 2908 Euros / ~ $3500 USD, and the "600" model is 4990 Euros / ~$ 5900 USD....my Hamilton Ferris 200 (which is spec'd about the same as the watt&sea 300) cost me just over $1000 USD, plus a couple hundred dollars for spare line / parts (which are still brand-new, never used)






There is more to say, more to explain, more to do....but, nothing more I can do now, as I don't know much about you, your boat, your cruising area / cruising plans, your budget, your aesthetic constraints, etc. etc....

So, I think this will do for now...



I do hope this preliminary info helps.

Fair winds.

John

P.S. Bottom line here: Read all above again....and follow the recommendations in #3 (3a, 3b, 3c, 3d, and 3e), and you will save a lot of $$$ (or Euros), have a quiet/silent time on-board, with no extra maintenance, and not burn fossil fuels to generate electricity!
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Old 30-07-2020, 22:59   #36
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Re: Could someone check my math please?

Re hscrugby. Interesting design. I had been thinking about something lower that stuck out the back more and that was entirely separate from the radar pole, but your version has some benefits to it.

1 shorter loa so easier parking and less likelihood of bumping the panels.

2 less shading from the radar on the panels.

The only issue I see with this plan is when the dinghy is hoisted it would block the view astern from the helm unless it was only hoisted halfway and secured against the push pit which is doable. Also, as I said previously, minimizing airdraft with the mast down is important so all this would need to be removable.

A lower setup on classic davits could be made permanent and stouter and would not block the view from the helm though it would stick out two foot further and be more prone to shading.

But thanks for the image. It helps me visualize what is possible.

Re Carstenb .

I take the point about light winds but that is partly why I want enough battery capacity to meet boat needs for 3-4 days rather than the standard two. Also you guys have already convinced me of the need for more solar. However, at 7-8 kn from astern Na Mara will be flying the asymmetric during daylight hours and making 3-4 kn. At that speed the watt and sea is producing about 3-4 amp, or between 70 and 100 Ah a day. That is not to be sniffed at. It’s about what 300 w of solar will give you..

Leftbrain. I will be putting a good monitor on this year. Unfortunately a regulator for the alternator will have to wait until I get hold of an alternator without an internal regulator.
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Old 30-07-2020, 23:31   #37
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Re: Could someone check my math please?

Many thanks Ka4wja.

Na Mara is a Regina 43. The cockpit is set relatively high aft which leaves no room under the boom for panels over the cockpit. There is maybe 4 ft between the backstays and the end of the boom over the helm but I donít want a Bimini so I wonít be mounting panels there. Over the short aft deck between the radar pole and the back stay there is a good space for an arch for mounting panels but I really donít want an arch purely for panels. An alternative would be to mount panels directly on the back stays but I am Leary of them wobbling around in high winds and stressing the rig. Aft of the pole is about two feet of sugar scoop over which I could mount davits with panels on top. I think that is my first option as we need the davits anyway.

Finally I could mount panels on the life lines and pushpit. However, I have a lot of rope bins there at the moment which are really useful as a lot of lines come aft the either side of the cockpit. It would be a rats nest in the cockpit without them and they would need to be removed to fit the panels here.

I have also read about the issues with transom mount watt and sea which is why I want the pod version. I am also aware of the noise issue which is why it would be mounted in the engine bay which has excellent sound insulation. Our engine is the quietest installation I have ever had.
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Old 30-07-2020, 23:40   #38
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Re: Could someone check my math please?

Re Mike

I ruled out wind generators due to the master cabin being aft and SWIMBO’s light sleeping. I like them in theory but it’s noisy enough back there with the wave slap and backstay hum without adding a wind generator
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Old 31-07-2020, 08:32   #39
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Re: Could someone check my math please?

Na Mara,
You're very welcome!

Although, I still am not clear where you are at (Sweden?), and where are you planning on sailing (across the Atlantic, to Caribbean / US, and back to Europe?)...
Would you please confirm this, as this is a very important factor in making specific recommendations....and not just about solar, etc., but also important to know because of energy consumption such as from your refrigeration system (fyi, if you are sailing to Caribbean, you will want to improve your frig insulation!)

Thank you.


Using some new info you provided, I can add some specifics here:

Quote:
Originally Posted by Na Mara View Post

Na Mara is a Regina 43. The cockpit is set relatively high aft which leaves no room under the boom for panels over the cockpit.
Okay, understood...
And, btw, this would not be a good place for panels (shading, cumbersome to work around them when needing to work on mainsail / boom, and easier to damage panels), even if you desired to mount panels there, I'd recommend against that.


There is maybe 4 ft between the backstays and the end of the boom over the helm but I don’t want a Bimini so I won’t be mounting panels there.
I understand your decision here, assuming you're in Sweden and sailing the Baltic Sea, North Sea, and/or Gulf of Bothnia, etc., where having sun on you during the day is important (and you have a pilothouse/dodger to protect you from weather)....BUT..

But, if you are sailing south (across the Atlantic to Caribbean, etc....even just summertime Med), you're going to want sun shade!!
And, while we can all debate skin cancer issues, let's just look at comfort for a moment....
{I grew up in S. Florida...and sailing the Bahamas, Caribbean, the N. Atlantic, and summertime Med....except for a few weeks in Long Island Sound, I've never sailed higher than 39* - 40* Latitude (and that was summertime), although my parents did sail into the 60*'s, I'm a low-latitude sailor....
And I know a good deal about how hot the sun is down here! And, not just hot on your skin, but hot in your cabin (makes sleeping difficult for many), and hot in your refrigerator/freezer, hot on your feet, etc..
Fyi, unless the bottoms of your feet are like leather, you'll not be walking on a unshaded teak deck without shoes!}

So, while I read your words and understand your decision, and as I write above if you're in Sweden, I understand...
But again, if you're heading south, you are going to want a some shade over your helm / cockpit, and shade over your aft cabin (which I assume is like my aft cabin, below the cockpit?)...

If I was heading north, I'd ask you about diesel heating, cabin and hull insulation, locations to purchase/refuel camping gas (Butane) for portable heaters, etc...as I have no first hand experience with those things...
So, please take a moment and have a look at every sailboat in the Caribbean or southern US....and you'll see bimini tops and sun shades!!
And, then re-read what I write here and above....and you might take another view on a bimini top and solar panels....}

Please take another look at my solar array and bimini top....and you may come away with some good ideas...

Article on my Solar Array
Solar Panels

Article on my Bimini Top
Bimini







Over the short aft deck between the radar pole and the back stay there is a good space for an arch for mounting panels but I really don’t want an arch purely for panels.
I understand this, as I also do not desire an arch (nor davits)....
Just remember that you can mount panels above the aft deck / transom, using your radar pole and another support (on port-side), so no arch would be needed....
Although this design is very specific to your boat, it can be done quite easily by any competent engineer or yourself (if you take your time in design)



An alternative would be to mount panels directly on the back stays but I am Leary of them wobbling around in high winds and stressing the rig.
No, do not use the backstays to support your panels....a bad idea all around....in addition to stressing the rig, the vibrations of the rig transmitted to the panels would serious shorten their life span...


Aft of the pole is about two feet of sugar scoop over which I could mount davits with panels on top. I think that is my first option as we need the davits anyway.
Bingo!
You've got a winning location!
Using this location allows multiple uses....davits and solar array...
{fyi, just to be clear, I'm not a fan of davits....but, if you want them, that's fine with me}

Please take into account here how high up you mount the panels will have an effect on possible shading....but...
But, since you can place a decent sized array back there, you can accept shading of one panel at a time (be sure to wire panels in parallel, or even better, have one controller for each panel!)
And, again, use high quality panels and make the mounting strong/secure!



Finally I could mount panels on the life lines and pushpit. However, I have a lot of rope bins there at the moment which are really useful as a lot of lines come aft the either side of the cockpit. It would be a rats nest in the cockpit without them and they would need to be removed to fit the panels here.
That's fine....few people place panels there, so that's good that you do not desire to...
Lifeline and/or pushpit mounting of solar panels is generally a bad idea anyway!
(in addition to much greater shading possibilities, they have a much greater chance of being damaged! as well as just being "in-the-way" of sailing / docking / boarding your boat!)



I have also read about the issues with transom mount watt and sea which is why I want the pod version. I am also aware of the noise issue which is why it would be mounted in the engine bay which has excellent sound insulation. Our engine is the quietest installation I have ever had.
The "pod" version....okay, I understand....
But, how in the world are you going to "un-foul" its prop?
Understand that if your main propulsion prop snags some Sargasso weed, it will rip it off in a second or two, when you place the engine in gear at any significant RPM....but, a fixed underwater prop turning a water-generator will stay fouled until you dive over the side to clear it...

And, at 3737 Euros (~ $4500 USD), plus installation (another thousand or two euros?), that's a wicked expensive "secondary" energy source?
In my opinion here, not a good choice / not a good use of $$$...again, this is opinion...

Also, using their figures (giving you 8.3 amps charging at 5kts) I think are generous....I'm going to assume in the real-world that will end up being 7 amps at best, at 5 kts, and maybe a bit less...and, certainly more power will be generated as boat speed increases...
But, this system (being a rather large power generator, in terms of electrical power and physical size) will create underwater drag....and while I'm not a racer and doubt you are either, you must take into account that this thing is going to slow down your boat all the time, not just when you need some electrical power (which is one of the advantages of a transom-mounted-hinged unit, or a "towed-water-generator")

Further, permanently installing an electric motor (generator) in a sealed unit, under the sea water? Permanently?
Hmm...again, just my opinion here....just looks like an issue/problem waiting to happen....and at best, reduced life of the unit...

As long as you're aware of the downside of this approach, and you have the money to waste....then okay, I understand...
But, I highly recommend spending your time (and $ / euros) designing and installing an efficient unshaded solar array, first and foremost....and only after that, and only if you find your solar energy output inadequate, only then consider this watt & sea....
(actually, I'd like to write: Don't Do It!! Just forget the watt & sea! But, I'm trying to be polite.... LOL )
I do hope this helps....
But, again....could you please tell us where and when you're planning on sailing / cruising?
Because I feel you're getting some well-intensioned advice, but that some of it might be moot or simply poor advice for your application / your cruising plans...
But, I'm not clear where you are at, and most importantly where you are going!

Fair winds

John

P.S. I also have recommendations/advice on refrigeration insulation, and autopilot use/energy consumption....but, I cannot be specific if I don not know where you will be sailing....
Frig/Freezer
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Old 31-07-2020, 10:32   #40
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Re: Could someone check my math please?

The big trip is as you describe. Down the Atlantic seaboard of Europe in time to catch the trades over to the Caribbean then up through the Bahamas and up the eastern seaboard of the US to cross back over via Greenland, Iceland, Svalbard or alternatively Bermuda, Azores and west coast of Ireland depending on the Iceberg situation and how brave we feel.

The autopilot is a hydraulic unit. It’s one of the best bits of kit on board. Really powerful and trustworthy but a power hog. Boat has excellent balance under sail and it is easy to get her tracking true.

What is your opinion about panels on deck? We have the top of our pilot house that we only ever walk on to hang washing off the boom. We could equally do that off the guard wires. Otherwise it’s empty real estate as we have in-mast reefing. What about mounting sunpower panels or the like there. See an earlier picture of the area. There is space for about 3-4 m2 of panels. I know it will be variously shaded by the boom, the main, the mast and even the sprayhood but wouldn’t the extra area make up for that? A lot of boats around here have panels on the coach roof. About half of those are rigid framed panels mounted on wooden rails to maintain an air gap under the panel for cooling. Some even have these on areas that would typically see foot traffic. Ours at least would not.

Finally, we don’t need a Bimini in the cockpit because we have the pilot house. It’s very well ventilated and works as well against hot weather as it does against bad weather. If it gets to hot we just retire into the pilot house and watch the world go by from there.

Oh and I just found out from watt and sea that a pod will not work on our hull. They need mounting aft of the keel on the center line to protect them and there is nowhere to do that on Na Mara as she has a long fin keel with shaft mounted propeller and half skeg hung rudder. If I want one of these it will have to go on the transom. On our transom that’s would either mean a custom made mount or their own universal one. I don’t trust the latter after what I have read.
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Old 31-07-2020, 11:51   #41
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Re: Could someone check my math please?

I’ve been doing a bit of surfing to identify the best panels for a coach roof installation and they seem to be Black Lensuns with rubber edges mounted with 3M ( they won’t be walked on so ....).

I’ve measured and I can comfortably get 220W on the pilot house roof. 4 x 30 w panels and 2 x 50w. Under perfect conditions that should cover about 100Ah a day of use. As these panels will suffer from some shading let’s assume 50Ah on average. Now add a single 90W panel over the radar dome. That will rarely be shaded so here we are talking about maybe 30Ah covered. So I would have 310W generating about 80ah a day.

That is more than I need at anchor but it’s less than half what I need at sea. I’m still going to need the watt and sea or some other hydro generator.
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Old 31-07-2020, 12:34   #42
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Re: Could someone check my math please?

A 200w is only a little longer than a 90 watt. And a 350w is still not that big.
Personally I'd at minimum put a 200w on the radar dome and unless it's separate for something wouldn't even bother with 50w panels.
From messing around and playing the smaller than 100w panels are really susceptible to shade and quickly just add nothing. I tried two then 3 50w panels for when motorcycle camping to charge a "solar generator" (aka battery with an inverter attached). It would "usually" charge if I left it almost all day. I was given a cheaper folding 100w and that would charge it within a few hours. If each panel had a separate controller, maybe?
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Old 31-07-2020, 13:21   #43
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Re: Could someone check my math please?

Hscrugby

I could do that! The two ariels sticking up are a defunct TV antenna and a defunct gps Antenna. I could take them off and mount a panel over the top. The 90w was the max I could get between the ariels but if I got shot of them then there is no reason I couldnít put a 175w panel measuring 150cm by 65cm. With the two mount points 80cm apart that is almost a perfect size with the same overhang everywhere. Feel a bit of an idiot for not considering this before as the ariels are just dead weight. Why did I not think to junk them?

I could have it so it could be tilted forward and back by about 45 degrees and in that location itís almost never shaded. I could get some serious ah out of that Even in northern lattitudes with a bit of active management and it would be a cheap and kind of cool installation. Single panel means single controller which I get for free with a watt and sea and the cable run is a doddle

The aesthetic impact is minimal and this works with what I have. And it will be way cheaper than doing the coach roof and probably will even give me more than 80 ah a day.

Am I missing a downside here because Iím not seeing any?
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Old 31-07-2020, 13:38   #44
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Re: Could someone check my math please?

Still say add more solar...
My goal is 900-1000w cause I like buffers. Tempted to go 1250-1400 and be able to run the AC some. As a fat man cooling off the sleeping area sounds brilliant. But lots of other "requirements" before that project.
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Old 31-07-2020, 14:03   #45
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Re: Could someone check my math please?

Quote:
Originally Posted by carstenb View Post
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)
I suspect your numbers are wrong-way-round? 9A @ 220v = 1980W. 1980W @ 12.7v DC is about 156A.

My watermaker (for example) also draws about 9A on mains and pushes my 12v amps draw into the 150ís. I have to run a big alternator while the watermaker is running if I want prevent my batteries taking a beating after an hour or two.

Or maybe I need to re-educate myself?
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