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Ralsy · 29-06-2020, 15:03

Apologies given, as this post is based not on a sailing boat but on a powered cruiser, but I think the topic is still relative to both.
Electric magnetic field heath problems and sea sickness
In alot of boats, passengers sit very close to electrical systems (such as batteries) of significant power, usually for a considerable amount of time. Apparently the currents achieved in these systems and the short distances between the power devices and the passengers mean that the latter could be exposed to relevant magnetic fields. In my case approx 1000 amp 12v battery bank underneath the main cabins bed, around 12 inches below the bottom of the mattress. I'm wondering if the hazards of magnetic field exposure or electromagnetic radiation (EMR) must be taken into account?
Is it usual to put such a large storage of batteries under the bed you potentially spend 1/3 of your day on?
The previous owner of this particular boat has told the broker he doesn't want anything more to do with the boat as all his family members get sea sick on the boat and most other people aswell if they come aboard for any extended lenght of time.
The sea sickness could be enhanced by the relatively narrow beam to length of the boat aswell as the heavy steel superstructure which could make it a little rolley at times. It's a 55ft long, 15ft beam, 45 tonne steel displacement pilothouse cruiser. There is a stability report available on the boat which stipulates the necessary requirements for when cruising such as making sure water tank">fresh water tank is full, gray and black are empty, centre fuel tank is empty, the other 4 are balanced except for tank number 1 which needs to have 350 litres of fuel less than tank 4. The boat does have Naiad Stabilizers but still thinking it could potentially be quite rolley.
So there are 2 questions,
1 - could the close proximity of the batteries be a potential health problem OR add to the sea sickness of passengers through the EMF on a steel boat?
2 - could the build of the boat as described be a problem in anything but smooth cruising conditions?
I have been for a sea trial but unfortunately conditions were smooth.

**a64pilot** · 29-06-2020, 15:24

I don’t think you get much EMF from 12VDC, and pretty much zero from batteries themselves

**Jammer** · 29-06-2020, 15:25

Quote:

Originally Posted by Ralsy

Apologies given, as this post is based not on a sailing boat but on a powered cruiser, but I think the topic is still relative to both.
Electric magnetic field heath problems and sea sickness
In alot of boats, passengers sit very close to electrical systems (such as batteries) of significant power, usually for a considerable amount of time. Apparently the currents achieved in these systems and the short distances between the power devices and the passengers mean that the latter could be exposed to relevant magnetic fields. In my case approx 1000 amp 12v battery bank underneath the main cabins bed, around 12 inches below the bottom of the mattress. I'm wondering if the hazards of magnetic field exposure or electromagnetic radiation (EMR) must be taken into account?

Batteries don't create a magnetic field except when current is flowing.

A 1000 amp current 12 inches (about 1/3 meter away) will give you a magnetic field of about 0.003 of a Tesla which is about on par with a fridge magnet if you hold it in your hand.. However, since the positive and negative cables produce fields in opposite directions the field will cancel out to some degree.

There is no electromagnetic radiation because batteries are DC.

Quote:

Is it usual to put such a large storage of batteries under the bed you potentially spend 1/3 of your day on?

It's not unusual. I wouldn't give the magnetic field a second thought. Fire safety and ventilation would be my main concerns. ::shrug::

Quote:

1 - could the close proximity of the batteries be a potential health problem OR add to the sea sickness of passengers through the EMF on a steel boat?

No.

Quote:

2 - could the build of the boat as described be a problem in anything but smooth cruising conditions?
I have been for a sea trial but unfortunately conditions were smooth.

I can't help you there but I will note that with a large pilothouse there would be the temptation to stay inside where there is no view of the horizon which will make symptoms much worse.

Ralsy · 29-06-2020, 15:31

Thanks for your reply.

**Jim Cate** · 29-06-2020, 15:42

I concur about zero electrical interference with health, however the stability issues concern me. If it is necessary to have a certain distribution of loads between the various tanks, how can you reasonably maintain the balance during a voyage as fuel and water are consumed? Seems impossible, and that would be a deal breaker for me.

Jim

SVHarmonie · 29-06-2020, 15:55

Quote:

Originally Posted by Ralsy

It's a 55ft long, 15ft beam, 45 tonne steel displacement pilothouse cruiser.

55 feet and 45 tonnes? Awwww, come on. I don’t think so! That’s 900,000 lbs!

Let’s do some quick calculations here:

55 ft * 15 feet * 0.75 (prismatic coefficient) gives us a water plane area of about 619 sq feet. So each foot of immersion would displace 619 cubic feet. At 64 lbs/cu foot, that’s 39,400 lbs. JUST to float the boat would have to draw 900,000/39,400 = 22 Feet. No wonder it has “stability issues.”

You don’t need to pull the sharpest pencil from the box to know this is BS.

If I wanted to troll the forum, my post would look an awful lot like this one...

Kelkara · 29-06-2020, 16:08

Quote:

Originally Posted by SVHarmonie

55 feet and 45 tonnes? Awwww, come on. I don’t think so! That’s 900,000 lbs!

Are you sure about that?

IslandHopper · 29-06-2020, 16:14

Quote:

Originally Posted by Kelkara

Are you sure about that?

I bet they think they are

Ralsy · 29-06-2020, 16:28

Quote:

Originally Posted by SVHarmonie

55 feet and 45 tonnes? Awwww, come on. I don’t think so! That’s 900,000 lbs!

Let’s do some quick calculations here:

55 ft * 15 feet * 0.75 (prismatic coefficient) gives us a water plane area of about 619 sq feet. So each foot of immersion would displace 619 cubic feet. At 64 lbs/cu foot, that’s 39,400 lbs. JUST to float the boat would have to draw 900,000/39,400 = 22 Feet. No wonder it has “stability issues.”

You don’t need to pull the sharpest pencil from the box to know this is BS.

If I wanted to troll the forum, my post would look an awful lot like this one...

45000 kg = 52.91 US ton and 47.24 imperial ton.

Ralsy · 29-06-2020, 16:32

Quote:

Originally Posted by SVHarmonie

55 feet and 45 tonnes? Awwww, come on. I don’t think so! That’s 900,000 lbs!

Let’s do some quick calculations here:

55 ft * 15 feet * 0.75 (prismatic coefficient) gives us a water plane area of about 619 sq feet. So each foot of immersion would displace 619 cubic feet. At 64 lbs/cu foot, that’s 39,400 lbs. JUST to float the boat would have to draw 900,000/39,400 = 22 Feet. No wonder it has “stability issues.”

You don’t need to pull the sharpest pencil from the box to know this is BS.

If I wanted to troll the forum, my post would look an awful lot like this one...

Why would anyone want to troll this forum? What could they possibly gain other than information relating to boating? Isn't this one of the reasons why this forum exists, to discuss boating topics.
Seriously!

Ralsy · 29-06-2020, 16:37

Quote:

Originally Posted by Ralsy

Why would anyone want to troll this forum? What could they possibly gain other than information relating to boating? Isn't this one of the reasons why this forum exists, to discuss boating topics.
Seriously!

Oh yeah by the way. My calculations put 45 ton at approx 99,000lbs not as you mentioned 900,000lbs.

Ralsy · 29-06-2020, 16:38

Quote:

Originally Posted by SVHarmonie

55 feet and 45 tonnes? Awwww, come on. I don’t think so! That’s 900,000 lbs!

Let’s do some quick calculations here:

55 ft * 15 feet * 0.75 (prismatic coefficient) gives us a water plane area of about 619 sq feet. So each foot of immersion would displace 619 cubic feet. At 64 lbs/cu foot, that’s 39,400 lbs. JUST to float the boat would have to draw 900,000/39,400 = 22 Feet. No wonder it has “stability issues.”

You don’t need to pull the sharpest pencil from the box to know this is BS.

If I wanted to troll the forum, my post would look an awful lot like this one...

Oh yeah by the way. My calculations put 45 ton at approx 99,000lbs not as you mentioned 900,000lbs.