One for the boat trim experts

[Trident]

Not strictly racing related but a bit specialist
I have a 50 foot performance oriented catamaran which I rebuilt to shed a lot of weight. It was altered by the previous owner from centre engined with shaft drives to sail drives on engines further back to the stern.
To balance the trim of the boat they put quite heavy stainless fuel tanks further forward . I've removed these along with a lot of other weight and replaced the engines with lighter smaller units but the boat sits 40mm down at the stern.

So the question is - will it sail better if I put more weight back on forward of the mast, or if I put more buoyancy at the back (extended transoms) or is 40mm so little that it's not really adding much drag and I wouldn't see noticeable performance gains by getting rid of it? I can mock up the weight at the front but conditions vary so much small gains would be hard to notice and I can't really do anything to simulate more buoyancy at the stern so I'm hoping some of the experts here will have a better idea than me from experience please

 

[Fr J Hackett]

I am no expert or anything near but won't compensating for excess weight at one extremity by adding weight at the other tend to make the yacht hobby horse.

 

[Chiara’s slave]

The fastest way, and IMHO you will indeed see gains, is to extend the transoms. But the transoms may well lift when sailing. If that is static waterline you may be right just as you are. The rig C of E is way above the deck. That’s how it is on my boat, loaded for cruising. The transom only drags in very light winds and heavy loads. A previous owner of Chiara put 19kg of lead in the forward crash box. All it is, is ballast. I thought the general idea was that weight is a bad thing.

 

[michael_w]

Cats are utterly different from monos. Talk to the designer.

 

[dunedin]

If it truly is a performance cat, and have done some serious weight reduction, I personally would not start adding weight again at the front. A big rig will push the bow down and the stern up. The one thing you don’t want to do is dig the bow in at speed. So a slight weight trim aft is probably safer.

 

[Chiara’s slave]

If it truly is a performance cat, and have done some serious weight reduction, I personally would not start adding weight again at the front. A big rig will push the bow down and the stern up. The one thing you don’t want to do is dig the bow in at speed. So a slight weight trim aft is probably safer.

Thats my thinking too. Adding a spot of stern buoyancy if it’s needed is the safer route, but it may well, if 40mm is the static transom immersion, be just right.

 

[Mudisox]

Is the 40mm when you stand at the stern or in the cabin or sitting on the heads forward.? Don't think it matters too much.