Twin O/B Sonic

I’ve seen this topic on here before but I’ve searched for it and failed miserably.

What is the opinion of you offshore wizards for a fore Vs aft center of gravity for our style of boats?

Second question is how do we measure?

Thanks guys!

jadento

I am sure I seen some threads on here also, but didnt find them either. I did find these with google though.

Boating Mag - Article
Boat Builders Article
Microship.com

Griff

If the trailer is set up correctly, the center of gravity should be a few feet behind of the center of the axles. I would guess 2-5 feet depending on boat length.
If the axles were exactly at the center, you would have little to no tongue weight.

Brad Christy

Griff,

I think you mean "ahead of center of the axles"....?

Thanks. Brad.
(937)545-8991

Brad Christy

Twin,

Just to be clear:

Are you asking about the CG of the boat itself, or the boat on the trailer? You didn't specify, but Griff mentioned "CG on trailer".

Thanks. Brad.
(937)545-8991

techman

On a V hull performance boat, I would guess that you would want to achieve 50/50 weight distribution fore and aft. Which with all that iron in the back is hard to achieve but some boats are better balanced than others. This is evident when "flying" the boat over waves/swells. Does the boat fly level or does it come down quickly ass first?

Isn't that why race boats have ballast tanks? As you burn fuel the CG changes and you add/remove ballast to keep it level.

How do you measure this? Not sure....

Wildman_grafix

Pretty sure you will need to lift it and use some sort of measurement on the lift to really find out. I could call my friend that did the LUCUS oil boat if you want.

Keith Atlanta

No, the furthur back the better in a V. Race boats have zero stuff in the cuddy and lightweight layup so they may need weight all trimmed out. Most V hull boats the CG is about a foot in front of the engines. For a fast V hull a little furthur ahead. Stepped can be even slightly further forward. I love CG stuff. I messed with this for months.

Its pretty simple to test. Make sure all the batteries are mounted at the stern. Take all your junk out of the cuddy, run limited fuel, keep moving your weight back or remove it, you will inevitably go faster.

OSO has been around for a long time, there are a bunch of threads. I have to laugh at some of the newer Facebook groups with newer guys in go-fast boats that mount all their batteries under the sink in the cuddy and all their amps under the bed then argue that thats not why their boat is slower. Even saw one that mounted 2 batteries under the bed with plywood and twobyfours! Because nothing could ever go wrong with that, including beaking the mounts and hitting the ceiling from a big wake. But hey, physics are a weird thing...

Wildman_grafix

That is because even though everyone loves to talk about how Bad A$$ rough water boats they have, you give them real 2-3 and they get scared, slow to a craw and talk about the 6 footers they were in.

Brad Christy

Techman,

Pretty sure race boats have the fuel tanks right on the CG, so fuel consumption affects CG as little as possible.

Thanks. Brad.
(937)545-8991