Boat Stability Test

Wondering if I can get some of you to perform a test for me. Regardless of how much I try to read on the subject, I don't have a clear answer. Ideally, if you have a flat bottom or modified V that has 36" to 52" width at the floor and carry at least 2 batteries.... I am trying to see how moving batteries outboard from centerline affects stability. Specifically, is it better to keep the weight close to centerline, outward (so long as it's equal), or does it matter.

In the case of my boat that will probably have 4-6 batteries, I'm trying to figure out if it's worth considering keeping the batteries on the centerline as much as possible, or if it matters or not.

What are your thoughts?

If I can't get anything definitive from someone, I'll test it myself as soon as I can get my boat to float. :LOL2:

I would say place them outside the center line toward the side of the boat. If you think of a teeter totter that is equally balanced on each side it doesn't matter how much weight is at the fulcrum in the center as it will not effect the its motion. By placing the weight outside the center line it will have a better effect as to counter balance each other. I'm no expert but this makes sense to me. I have one of my batteries mounted opposite my fuel cell and anchor storage and the other opposite for forward live well. This equals everything out pretty well.

Well, after a little more searching....

I see the answer is rediculously easy to understand. #-o

:BS:

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Interesting... Have to watch this later and plug in my numbers...

Or do it the redneck way, toss her out and see if she floats.

To toss an opinion on the original question - I don't know.

Simple enough Brine. IF YOUR A ROCKET SCIENTIST.
:?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?:
I think I'll try doing it Will's way,much easier.LOL

My thoughts are if the batteries are equal distance away from the center of the boat them it doesn't matter. But this comes from a guy that after a year of pursuing a mechanical engineering degree changed his major to something easier because I'm too dumb for all that fancy math

From experience, I can tell you to keep all you can on the center line for maximum stability. I can't tell you why this is from a physics point of view, I just know that the more outboard weight you have, the more leverage you put on the vessel when you get off center yourself.

I think much has to do with the fact that this is not a teeter totter. Its a boat. Floating in water. The hull pushes down on the water with less force than the water has pushing back. The more weight you move from the center, the more you're able to push the sides down.

The less weight you have at the gunwales, the less leverage you can apply to 'tilt' the boat. What keeps a boat from tilting all by itself is the hull design. It's the amount of 'tilt' resistance the hull has in the first place that will decide how stable the boat is. The more crap you put out to the edges, the more tippy it will become. It will sit there fine with a dead load, but add a live load, like you walking around and hang on! You're about to take a swim.

Not sure how it differs, but I know shrimp boats will hang weights from their outriggers to stablize the boat. This would contradict the centerline theory.

That said, I'm fairly certain I read somewhere from someone who knew what they were talking about subscribed to the centerline theory.

I think I'll just try to call someone from Grumman and ask.

Brine said:

Not sure how it differs, but I know shrimp boats will hang weights from their outriggers to stablize the boat...

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Were they doing this to to bring the boat back "level"? Maybe (just guessing), that perhaps they loaded thier outboard (of centerline) holds with shrimp and had to counter-balance to bring the boat back to level. On my last ship (while moored, port side to the pier) we had a small overboard discharge line (pipe), located right at the waterline, break off. We were taking water into the ship through this new hole from the broken pipe. We had to repair it so we lowered the starboard life boat (opposite side of the ship) to the water's edge in order to list the ship to starboard and bring the hole on the port side out of the water. Once that was done we welded in a new pipe, brought the life boat back into the davit, the ship leveled-off, and we were done. What we did was change the center of gravity by shifting weight outboard away from the centerline. I'd keep the batteries (4-6 you stated?) as close to centerline, and evenly distributed as much as possible.

I tend to agree with the Shrimp boat theory. Here's my reasoning. The further you have your weight from the center the less of a difference there would be if you move off center. Example. If you have 100lbs on each side of a teeter-totter, and you put 20 more pound to one end the teeter-totter dropps gradually. as you are only affecting the it by 20% more weight. If you have your 200 lbs in middle of the teeter-totter and you put 20lbs on one end it will drop like a rock because it is 100% heavier on one end. Head to the park to test the theory. :LOL2:

Nussy said:

Head to the park to test the theory. :LOL2:

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Waiting to get some holes welded so I can float the boat.