Optimal weight distribution, how relevant

[MapisM]

I am talking of about 250kg worth of domestic batteries, on a 56' boat.
Original placement is inside the e/r, just in front of a w/tight bulkhead that separates the e/r from the stern section (which aside from giving access to rudders, flaps and s/thruster, is essentially a large locker).
My first thought was that the batteries were placed in the e/r in order to leave more space in this stern locker, but while space for all sort of useless stuff is always welcome in a boat (well, that's what swmbo keeps telling me, anyway ), I'd rather have the batteries anywhere else than in a pretty warm e/r, if given a choice.

But as it happens, I have the opportunity to cross check directly with the builder all my refitting ideas, and he told me to forget this one, because it would affect the finely balanced weight distribution - something he's rather proud of, as I discovered.
All well and good in principle - I understand that on a P boat this is a somewhat relevant factor.
But the shift would have zero effect laterally, and less than three feet longitudinally (it's just a matter of moving the bank from very close to the e/r side of the bulkhead, to equally close to its opposite side astern).

Gut feeling tells me that the effect on weight distribution and boat attitude/behavior would be negligible, but wadduthink guys?
And those who agree with my gut feeling (if any), would you bother shifting the batteries in the cooler area, or do you think that I should not bother regardless?
TIA!

 

[jrudge]

Sounds a lot of work for at best a marginal benefit.

To find out the impact take 3 decent size guys and move them round the boat. Same weight shift !

 

[Portofino]

I would not do anything yet
Where are the tanks ?
Wait until you have plenty of experience to get the feel of a full ( heavy) boat and a light -empty boat
Learn trim , min planning speed , rpm etc
On the face of it shifting 250 kg in a what 35 ton boat -guess ? -does not sound much , but you got it from the horses mouth.
Btw -where is the tender now ?

There are a lot of boats about FB in particular who appear to put NASA to shame -launching to the moon
When underway ---- so you don , t wanna inadvertently end up in that club

Aside I was thinking L of connectors issues
Cock that up in the chain(s) -then despite a theoretical better temp -you have moved into premature bat failure territory actually faster than OEM , set up
They spend most of the time sat in an ER with the E off
Work out how many Hrs /year the engines are ON -then % that 24x365

Then consider potential gas extraction /ventilation --ER is best
Nah -You are making hassle for your self
Wait -if it ain't broke -------

Put the € in the man maths war chest for 1st Y
Unplanned repairs ---- there will be some once you get afloat and start to use it

 

[vas]

P.,

assuming you do have e/r extractor fans, and considering that we are talking for 3-4h a day max that temps are going to be high in that e/r, I'd not bother with the move.

Spent the same amount of time in thinking how you're going to fit solar panels without distorting the image of the DP instead. That alone is going to transform the experience and save the batteries (imho)

cheers

V.

PS. not seen many pics as yet!

 

[MapisM]

Put the € in the man maths war chest for 1st Y
Unplanned repairs ---- there will be some once you get afloat and start to use it

LOL, I already began using that war chest even before hitting the water...!
...hopefully trying to put 99% of things straight beforehand.
Ok, make it 95%. I'd be already happy with that.

Ref. your questions, I don't think they are so relevant for the alternative I'm considering, because what I'm assuming is simply a longitudinal weight shift of 2 to 3 feet, AOTBE.
But here's the answers, possibly just out of curiosity:
- tanks are one each side of the engines (700L each) plus one (same capacity as both side tanks) right at the center bottom of the boat (structural, integrated in the hull bottom);
- tender is on the swim platform, but I'll use a pretty light one (there are sisterships around with MUCH heavier 3.5m jetribs)
- cables length would be practically the same (they already run along the top of the bulkhead, just a matter of going through it and then down, rather than just down)

Ref. the planing AoA, during the seatrial I was very impressed by how flat the boat remains - also at her lowest P speed, and during the transition. Btw, at these speeds she's very sensitive to tabs regulation, and even if almost fully loaded, she never needed them fully down.

All that said, you (and also jrudge+vas) might as well be right that if it ain't broke etc...

Any other views?

 

[MapisM]

Spent the same amount of time in thinking how you're going to fit solar panels without distorting the image of the DP instead. That alone is going to transform the experience and save the batteries (imho)

This is a good point, V. Surely not something for this year, but possibly for the next.
Btw, no need to think a lot, 'cause there's a decent space for panels just about in the same position used by Hurricane in JW.
Besides, I was already thinking to replace the existing battery charger+very small (250W) separate inverter with an integrated Victron unit, so I might as well consider one capable of handling panels too.
If available, coming to think of it: does anyone know if panels require a separate box for recharging batteries, or is there such thing as a unit capable of handling both "traditional" recharge from AC and from panels?
As far as inverter goes, I'm not after a huge power, 2 kW would be plenty, but also 1.5 would be fine.

 

[vas]

not sure i've seen victron doing an everything charger/inverter.
Others will be more helpful, but imho keep them separate, buy a decent MPPT Victron solar panel charger (same as Hurr and myself and lots of others...) and buy a dedicated charger/inverter thing.

Having said that, I feel that with decent sized panels and of course some use of the craft, the victron charger would only work sporadically (if ever) On that grounds I'd question the need to install an new charger Just get a decent inverter and be done with!

cheers

V.

 

[Portofino]

Trim or lack of it sounds good .
Not wanting to ignite another "lifting strips " debate I did notice on the hull pic ,s it's got ,orMr"DP" is using a similar shape rail taken back to the transom .
There are not many owner occupiers left these days with lifetime of knowledge of designing /building boats --so I would say Mr "DP ,s " advise is priceless .
I can,t ring up Mario Amarti and ask this ,that or t,other .
So for me "Mr DP's counsel is gold .
I think these old boys ,s experiance counts for a lot .A of A is little mentioned but prob v important ,unless your designer worked @ Cape Canaveral once and got into a muddle planning boat and rocket ------ some have -look around


Btw as you prob guess I only use flap in big seas when I still want to bomb along --just to make the finer fwd sections cut -part a bit more .
Normal use the flaps are redundant and up =less draggy and like yours as she accelerates it just lifts up more /less equally --but then then those lifting strips do run all the way to the stern pushing it up stern wise as she speeds up ,keeping the bow level .


Yours being a V drive set up I suspect is ultra sensitive to any MORE rearwards Kg shift ,as MR "DP" has already shoved what he thinks he can get away with back ,hence the lateral tankage etc and not noticeably compromise the running angle .
I understand 4 % is optimal .
Of course flaps ,bigger flaps and stern boxes added on and huge centre protuberances tacked on post build are a get out of Jail for cocked up running angle Ao A issues ---there's a lot about

 

[BartW]

Can’t give much advice on the weight distribution

On BA we added quite a lot of weight on the stern,
Up to a point that you can see that the boat heels backwards,
To compensate for that,(to some extend) we store the dive weights (80kg) in the anker chain locker,
And the oxygen safety tank in the bow crew cabin.

Even without that, I didn’t notice much influence on the behavior,
In my experience a bit more bow up doesn’t change the behavior in a negative way. (but I agree that it doesn’t look so nice)

Re. temp of the batt’s
Coincidently, I have been thinking about that also on BA you know my batts are in the ER
We have installed a big ventilator with a hose, for blowing cold fresh air over our domestic battery’s,
Actually this year we will replace the batt’s, they were nearly at the end of their live span,
And for the (small) price I paid for them I decided to replace them now instead of one season later.
Physically loading them in my car today, for a friend to bring them to Italy

Next replacement of battery’s in 3-4 years will be li-ion.

In your boots, I probably wouldn’t bother changing the batts position.

@ Vas; not only during navigation, engine room temp is >60°C
But after stop, temp raises to >80°C because of the heat capacity of the engines and fuel,
And it takes them up to 12hrs to cool down completely (in BA)

Re. solar power battery charger,
You need a separate MPPT for that,
Just look at it as another charger in parallel to the alternator and the mains charger.
If you take all from Victron, you can add a display and a IP connection to see what is going on in the units.
They all integrate in the same network.

If you are planning to add a invertor, I would take the Victron multiplus or Quattro
They integrate charger and invertor, and are the best ” value for money “ devices from Victron.
Then you know you have a good and “intelligent” charger,
and keep the old one as a spare or connected to the engine bank

 

[MapisM]

Ok folks, thanks.
I guess I'll stick to the current placement - if nothing else, the e/r has a proper fire extinguishing system...

As an aside, talking of e/r temperatures:

@ Vas; not only during navigation, engine room temp is >60°C
But after stop, temp raises to >80°C because of the heat capacity of the engines and fuel,
And it takes them up to 12hrs to cool down completely (in BA)

Blimey B, 80°C is sauna territory, you've got a very hot e/r indeed!
Just for reference, at 93°C my fire extinguisher goes off automatically...

Since you mention "and fuel", do you possibly mean that the return fuel lines are not cooled, hence after a cruise you've got burning tanks due to the vicious circle or excess fuel constantly coming back hotter and hotter?
I used to have that situation on my old tub, because on the Cat 3116 there were no integrated heat exchangers for the fuel return.
But the situation improved radically after I installed a couple of small dedicated coolers, as I was suggested of the best Cat engineer I ever came across (RIP, old chap).
Btw, e/r temp aside, it's MUCH better to feed the engines with cooler fuel.

I didn't yet investigate the new to me MAN V8 engines in this respect, but if your V12 have no integrated fuel coolers, I suspect that also mine don't have any.
And if that is the case, fuel coolers are bound to go straight in the to-do list, based on my previous experience...
Damn, I didn't need yet another refitting item!

PS: thanks guys also for the suggestions ref. charger/inverter and MPPT.
B, I will follow up on that via email.

 

[MapisM]

I can,t ring up Mario Amarti and ask this ,that or t,other .

Yep, that's sad. According to what I was told, he would have loved to answer your questions...

 

[BartW]

Never measured the e/r temp, but when the engines stop running at operation temp 85c, and airflow stops, i assume the air wel get close to that temp. Swmbo doesnt like to keep the fans running after stop, because they make some noise

Some time ago I learned here on the forum about fuel coolers, but decided not to put them on my wish list, as the boat ran fine without them the past 25y ?