If it's rocking...? [ballast question]

[Sir Percy]

I've just added ~1.47 metric tonnes of ballast to my boat, and while it's all nice and level, it feels more prone to rocking when i step on/off the gunwale. What should I do? 

[lifeintheslowlanes]

Could that potentially be just because it now has more weight lower down that the righting movement is more noticeable? Might be completely wrong...

[Sir Percy]

1 minute ago, lifeintheslowlanes said:

Could that potentially be just because it now has more weight lower down that the righting movement is more noticeable? Might be completely wrong...

I still have some of the old ballast (pavers) on board which I haven't yet removed, but...too much ballast? I'll see how it behaves when it's removed.

[ditchcrawler]

1 minute ago, Sir Percy said:

I still have some of the old ballast (pavers) on board which I haven't yet removed, but...too much ballast? I'll see how it behaves when it's removed.

Are you adding or removing?

[lifeintheslowlanes]

3 minutes ago, Sir Percy said:

I still have some of the old ballast (pavers) on board which I haven't yet removed, but...too much ballast? I'll see how it behaves when it's removed.

Would be interested to know how you get on with that as i've had hell lately trying to balance everything out onboard to stop it rolling around quite so much. A couple people had suggested maybe removing some ballast could help but I haven't had chance to try it out yet...

[Sir Percy]

4 minutes ago, ditchcrawler said:

Are you adding or removing?

Removing remnants of old pavers which now don't fit into the spaces between the new bearers, and added steel block ballast.

Edited October 16, 2019 by Sir Percy

[Sir Percy]

19 minutes ago, lifeintheslowlanes said:

Would be interested to know how you get on with that as i've had hell lately trying to balance everything out onboard to stop it rolling around quite so much. A couple people had suggested maybe removing some ballast could help but I haven't had chance to try it out yet...

Boats are going to rock, there's not too much you can do about that...it's just that mine feels more reactive to my weight than before, which was unexpected.

 

Have you recently installed anything of significant mass above the waterline?

[lifeintheslowlanes]

1 minute ago, Sir Percy said:

Boats are going to rock, there's not too much you can do about that...it's just that mine feels more reactive to my weight than before, which was unexpected.

 

Have you recently installed anything of significant mass above the waterline?

Not as far as I can think of, just feels a load more tippy when stepping on and off than it did before I added the rest of my stuff onboard, maybe it's sign I should have a clear out ha ha.

[MtB]

The point is, the height in the boat of the ballast makes a noticeable difference to the tendency to rock about. The lower it is, the more stable the boat will be.

 

Make sure all the new ballast is resting right on the baseplate under the floor, and remove all the old ballast which you say is still in the boat. It must presumably be out of the bilge now? 

[Kudzucraft]

1 hour ago, Mike the Boilerman said:

The point is, the height in the boat of the ballast makes a noticeable difference to the tendency to rock about. The lower it is, the more stable the boat will be.

Exactly! 

 

I used a large concrete slab as an anchor to moor a sailboat to. We placed the slab on a trailer. A small aluminum flat bottom skiff on top and strapped to the slab and then launched them.  Paddled it out to the spot, released the straps and darn near flipped the dinghy when we lost all that ballast. Was amazing how much difference in made.

[BEngo]

Not only is the height relevant but so is the distance from the centreline.  If you have replaced pavers all over the baseplate with a row of steel blocks down the centre line then the boat will feel more tender.  If the steel blocks are shared out between the edges it will be stiffer than with the pavers.  It is all to do with moments of inertia and metacentric height as well as sheer mass.

 

N

[Sir Percy]

18 hours ago, Mike the Boilerman said:

The point is, the height in the boat of the ballast makes a noticeable difference to the tendency to rock about. The lower it is, the more stable the boat will be.

 

Make sure all the new ballast is resting right on the baseplate under the floor, and remove all the old ballast which you say is still in the boat. It must presumably be out of the bilge now? 

The new ballast is all down on the baseplate. A lot of the pavers have been removed, and whats left has been taken up an shifted to fore and aft extremities of the boat - however, piled up to six layers high (on the baseplate). So I'll see how removing it changes things.