center of gravity fore and aft.

[txtowman]

Is the center of gravity moved when the keel is up or down?

I know if i am tending sails on the bow the boat is down in the bow.

If I put an equal amount of weight in the bottom of the bow at the same distance from the center of gravity will it offset 100% of the weight on the stern?

My boat is always high in the bow and low in the stern.

My plan is to move the batteries and water storage to under the v-berth.

Any help will be appreciated.


75' C22

2 70 pound batteries
10 gallons of water(most of the time)
12 gallons of gas in cockpit lazerette. Approximately 72# + tank weight
everything else is pretty well balanced out inside.

70# outboard also.

 

[Chris Patterson]

Hey Towman. Interesting. C of G's being an interest of mine, (past occupations, etc.), I have pondered the same question. I submit, that if the keel is ALL the way down, with no weight whatsoever on the winch, the c of g will most likely change, from aft to fore. Simply because you've taken part of that 550 keel weight off of the point of where the winch resides. This would be a gradual change as you can tell, simply because of the effort involved in lowering the keel, it gets easier to lower, (and raise), at the bottom of the process. But the center? Hmmm, a whole lot of variables here of course. But the center of the mast would be my guess in an unloaded boat, give or take but a little.
But your question about "equal amount of weight the SAME DISTANCE from the center of gravity offsetting 100% of the weight" from fore to aft, the answer is certainly yes. Providing you know where the center is, you can put the weight 2 inches in front of the fulcrum, and two inches behind it, the difference will be equal.
Regarding the weight being low in the bow, as opposed to crouching in the pulpit, it makes hardly any difference whatsoever. A tad, yes. But I'm gonna stay away from geometry and physics here..

 

[txtowman]

I really want to get my lower gudgeon to sit above the waterline. If I can do that then my motor will be out of the water when it is raised.

And if I understand correctly the boat will point better.

 

[Bilbo]

If you have a boot stripe it is supposed to be at the waterline BUT I believe that this location is based upon a boat without any outboard. At the stern, my boot stripe come s to the point of the transom on the centerline. But because of battery, ourboard, and gas +anything else including bodies, the weight is shifted towards the stern. My transom sits slightly below the waterline by about 1 or 2 inches.
I'd say that when we lower the keel, the weight is shifted forwards a tad but the keel is close to the fore/aft position and so, not much change. It would be like placing two 250 lb guys about 3 feet behind the mast on the cabin top and then moving them forwards about two feet. This difference would be much greater IF you moved both of these guys from the stern rail to the bow pulpit. When I am motoring in small waves, I can hear the difference in the outboard if I move from the stern of the cockpit to the bow because the motor is lifted about 3 inches.

The weight also shifts depending upon the winds because a run in a stiff breeze will push the mast towards foreward and drop the bow.

Also, if your lower tiller gudgeon is submerged, it may because you are hanging off the stern to check this.

 

[watercolors II]

Dragin ass

I think the Catalina 22 class racing rules on my ‘87 says that I can not move the battery from the stern to the bow. If that is the case then the shift in weight forward must provide some kind of an advantage. You can purchase a couple blocks for mid-boom sheeting and with a tiller extension you can shift the helmsman forward in the cockpit, wonder why?

I know from experience that if you send someone forward to sit on the bow pulpit when running down wind your speed will pick up under sail and also just under motor.

So, I would say, keeping you ass out of the water would be the ticket unless it’s an extremely hot day!

 

[txtowman]

Well, I don't race. I just want the ability to point a bit better and use less gas when motoring. I end up motoring a lot when I am single handing.

I should rig the lines to make it easier, but I want to save what little money I have to go towards a bigger boat.