Panther

Yes, unless you move the weight around in the boat the CG won't change. You'll need to compensate with more/less trim to make up for the lack of balance if it's not set up properly, this scrubs speed.

Panther

Lots and lots of time and $$...

Some Cats have the motor mounts on "rails" so they can shift the CG so they can set it up for optimum conditions.

StillHaulin@63

I think I might experiment with this CG question this weekend.

I'll set my tab & trim settings completely neutral, and replace enough weight in my bowlocker to create a slightly positive hull attitude providing a fairly stable offshore ride in normal seas. It seems logical that the tabs would then become more effective in bringing the bow down if necessary.

But bringing the bow up is a different issue. At some point, don't the tabs become irrelevant in raising the bow. If they're raised above neutral, how would they provide lift for the bow? It seems that would become the purpose of the outdrive trim.

BajaRunner

I personally think you are looking WAY too much into it. Learn your boat and how to drive it. If its too rough, look at a longer boat.

StillHaulin@63

Buying a bigger boat is quitting, mastering what I have is exciting!

BajaRunner

Thats what i said, learn your boat.

You should take tres martins class.

onesickpantera

I agree, way too much! Just get some seat time in your boat and you will learn how YOUR boat reacts.

When I bought my Pantera the first few times I had it out(early spring) it was really smooth. Tabs up, trim out and running a consistant 70+ mph. As the boating season approached the waters became more sloppy from the additional boat traffic. Lift the tabs too much looking for that last 2-3 mph and the right wave would send you launching.

I constantly noted my tab position vs speed and "looseness" of the boat and made mental notes. After a few hours I knew where the sweet spot was for sloppy water and never brought the tabs up any higher because I knew I'd launch the bow.

I will admit once in awhile I get out of shape because water always changes. But I immediately bring the tabs down, take note of where they are at and leave them under that position.

I finally got to run in some nasty water over the 4th. 4 people in the boat and a full tank of gas and we were running 64-65 mph on top of some confused 3+ footers. I kept the tabs slightly negative and the trim about neutral and throttled the chit out of it. Maybe I could have squeezed a little more out of it but IMO it wasn't worth it. In that kind of water I don't want to take the chance of injuring a passenger to get 2 more mph. Plus, they were all impressed as hell at how my little boat was ripping through them!

I have ran with a lot of faster boats and in a good 5-6 mile run I am usually ahead of them because they are trying to squeeze every last mph out of it and they end up getting out of shape, recovering and starting over again until they get all out of shape again. And then they just keep repeating the cycle. Meanwhile I am blasting through the slop nice and level!

Okay my post turned into a novel. My point was use the tabs and drive to control the attitude of the boat and with seat time you'll get better/faster.

GLH

Do it.

Zudnic

In a plane knowing center gravity and its effects on flight is a must. In a boat you are compensating for the cg effects on how the boat rides, reacts to the condition, even though you are doing it you don’t really need a reason why. From reading his site it does seem that Tres Martin does cover this topic to a degree. Think from a safety stand-point you don’t really need to know what center of gravity is; sellers however should give an idea how the boat they are selling reacts in dif conditions and what they find best in trim settings etc.

Question: how much more driver and throttles was needed to compensate for the loss of trim?

Every one else question: have you driven the same model but dif set-up, engines, no cabin Vs cabin? Yes, how noticeable was the dif. Between the “versions” on the same hull?

StillHaulin@63

I appreciate all your suggestions and will use seat-time for my teacher as you've suggested. Actually, my interest was more in understanding the physics of offshore boating rather than increasing my performance. But I've enjoyed this dialog and will let you know how it's going!