Beautiful boat but where are the buyers?

[jfm]

if you must apply a trasversal force to the hull (=stab fins) to contrast the wave force which would make the boat roll, the more "longitudinally neutral" such force is, the better.

Aty first sight, that makes sense to me, on an amateur basis. If the stabs are, say, lifting the port side to stop a roll you dont want them also lifting the port quarter and stuffing the stbd bow downwards.

BUT, I think to stop a roll like that, the port stab will lift the port side and the stbd stab will sink the stbd side. Then the upward lift component of the port stab on the aft port quarter (caused by the stab being located aft of the LN point) is perfectly offset by the downward push by the stbd stab on the starboard quarter, hence it all cancels out (though with more drag). Get my drift? In which case it would seen that being not quite at the LN point is no problem, apart from some drag.

I'm not sure - just guessing here

But all that said, you have to fit them in the engine room on a boat like the Aq74, and if they are therefore a metre too far aft (of the strictly "correct" position) it probably makes little discernable difference

 

[MapisM]

BUT, I think to stop a roll like that, the port stab will lift the port side and the stbd stab will sink the stbd side.

Yup, they do. But that's an even better reason to place them near the CoG, if you think about it.
In fact, a fair portion of the force they generate actually works as rudders do - creating a sideways force. And that would badly affect the boat course, if they would be placed very far astern (or also under the bow, for that matter).
Though I guess that 10% or so aft of the ideal position can't really make a huge difference.

But all that said, you have to fit them in the engine room on a boat like the Aq74, and if they are therefore a metre too far aft (of the strictly "correct" position) it probably makes little discernable difference

I don't get why "have to".
All the controlling equipment I've ever seen were in the e/r, but almost none of the fins/actuators part were.
They neither take a lot of place, nor are too noisy to locate them in the cabins area.
And if you mean for safety reasons in case of grounding, I'm not sure that a flooded e/r is really any better than flooded cabins... Assuming that in both cases there are watertight compartments.
Or did you see any other reason I can't think of?

 

[AndieMac]

I believe the stabilizers are as fitted from new in the factory.

Help me out with the engineering please. Surely the stabilizers need to be fitted well aft of the centre of horizontal stability or whatever it is called? If you put them on the C of G it would be like balancing a plate on a stick.

The Nordhavn 43 has its stabs. located pretty much mid-ships. The stb. side one is in the masters' ensuite (centre of boat) in a shallow locker with a lift out lid. The port side one is pretty much under the bed, which lays thwart-ships.

 

[jfm]

Yup, they do. But that's an even better reason to place them near the CoG, if you think about it.
In fact, a fair portion of the force they generate actually works as rudders do - creating a sideways force. And that would badly affect the boat course, if they would be placed very far astern (or also under the bow, for that matter).
Though I guess that 10% or so aft of the ideal position can't really make a huge difference.
I don't get why "have to".
All the controlling equipment I've ever seen were in the e/r, but almost none of the fins/actuators part were.
They neither take a lot of place, nor are too noisy to locate them in the cabins area.
And if you mean for safety reasons in case of grounding, I'm not sure that a flooded e/r is really any better than flooded cabins... Assuming that in both cases there are watertight compartments.
Or did you see any other reason I can't think of?

Yup you're right. "Have to" is too strong. I should have said "slightly preferable". If one had the choice it's the sort of gear that "belongs" in the engine room, and that also avoids need to take hydraulic pipes thru the engine room bulkhead, but yes I see your (and AndieMac's) point that you can put them under a bed (keeping them v clean to avoid an oil or grease smell in the cabin)