Weight distribution question

[Jdege]

Suppose you're trying to place 400 pounds of battery on a boat. This is heavy enough to affect trim on any but the largest boat.

You want it centered both side-to-side and fore-and-aft, to keep the boat in trim. And you want it low to maintain stability.

But what about rotation?

Placing 400 pounds on the centerline and or splitting it and placing 200 pounds at each rail have the same effect on trim, but the latter has much more angular momentum. Would the hull begin a roll more slowly, but continue it longer?

What effect will having more weight on the beams have on sailing characteristics than having the same weight on the centerline?

[thomm225]

I'm about 190 lbs. and used my weight distribution on my 300 lb. beach cats when racing as it had quite an effect.

I doubt you have much to be concerned with on a boat like yours though that weighs in at around 12,000 lbs. unloaded.

The 400 lbs. of batteries is a tiny percentage

But some folks like details......

I have my 140 lbs of golf cart batteries all on one side on my 6600 lb. sailboat and it still sits in the slip with mast straight up

[Jdege]

Originally Posted by thomm225

I'm about 190 lbs. and used my weight distribution on my 300 lb. beach cats when racing as it had quite an effect.

I doubt you have much to be concerned with on a boat like yours that weighs in a near 12,000 unloaded with 400 lbs of batteries

But some folks like details......

I like understanding.

What effect does increased angular inertia have on handling?

[Montanan]

Depends on which axis of rotation you are assessing.

[thomm225]

Originally Posted by Jdege

I like understanding.

What effect does increased angular inertia have on handling?

No much on a boat that weighs as much as yours does and as slow as the movements will be.

But you have come to the right place!

There are threads here with over 127 replies on how to paint rough surfaces which sort of explains why some of these cruisers don't get bored at anchor.

I used weigh distribution for pointing in the past and would be trapped out forward of the front beam on my Nacra 17 with the leeward bow almost buried.

Luckily they were very narrow in the front and wouldn't cause a pitchpole

Photo is of the boat but on a different day

[rslifkin]

I'm not sure the difference will have a noticeable impact on sailing performance. However, I'd expect a slightly different rolling motion at anchor. The batteries out to the sides should make the boat stiffer against small waves, as there's more inertia to resist roll. It's likely to be a fairly small difference, however.

[Jdege]

Originally Posted by Montanan

Depends on which axis of rotation you are assessing.

In my original post I said I'm wondering about roll.

I understand the effect in the abstract, but how that affects the handling of a boat is unclear to me.

I'd expect it to be slower to start a roll, but also slower to recover. What does that mean in terms of stability? Helm? Etc.?

[pjShap]

Changes in the rotational inertia will change the period at which the boat rolls most easily. It's not a matter of which is better, but only very slightly different for such a minor effect. The mast and keel dominate the rolling moment of inertia. I would put the batteries where they are most convenient and safe.

[Jdege]

Originally Posted by pjShap

Changes in the rotational inertia will change the period at which the boat rolls most easily. It's not a matter of which is better, but only very slightly different for such a minor effect. The mast and keel dominate the rolling moment of inertia. I would put the batteries where they are most convenient and safe.

True enough. My masts weigh only 100 pounds or so, but they operate on a much longer moment arm. And there's 4000 pounds in the keel. Moving 400 pounds three feet further out would be a minor change.

[Don C L]

you can always take 4 friends out sailing, put 2 on each side and see what happens. My bet is, while sailing, not much, if anything, noticeable. At anchor you may notice less rolling but I am skeptical. And you won't have the batteries that far out.

[Benz]

Skene's "Elements of Yacht Design" advocates bolting some of the ballast to the underside of the decks to make the roll period longer and thus more endurable. Rolling at anchor is not as bad when it's long and slow rather than whippy.
Although any rolling at anchor is a bummer....