Quote:
Originally Posted by Bushwacker
Don't know about Potter, but Moesly always centered fuel tank on the CG so trim wouldn't change as you burned off gas. (With over 13,000 hrs flight time in WWII, most of it flying cargo, he understood the importance of CG location better than most!) Probably safe to assume Potter did the same thing.
So to begin with, assume the original CG was at center of fuel tank, with a 300 LB MOTOR that the 20' hull was originally designed for! Now you're talking about changing lots of stuff, so I'd look at each change independently and calculate the CG change of each. Going to a 500 lb motor will move CG AFT, as will installing a lighter deck, console and removing wet foam! Even if the total package is lighter, it still won't float and handle right unless CG is right. I would NEVER accept the performance penalty of ballast when you can move batteries, gas tank, and console forward to get it right. Since people, coolers and gear tend to congregate in the back where ride is softest, and ALL of your planned changes are moving CG AFT, I'd put that gas tank as far forward as possible! My gut feel is that you're gonna have to move console fwd a fair amount, but before you bolt it down, maybe do a flotation test after you hang motor with pictures of transom/bootstripe to document how level boat sits in water. Then you can move console to see what effect it has. Use trash cans filled with sea water to simulate crew weight. And if you DO still have to add ballast, consider using 20' of chain on your anchor rode . . . makes a HUGE difference in anchor holding power!
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Thanks BW
My original thought was to move the tank all the way forward. But then I started thinking that with it far fwd of CG the trim of the boat would change as fuel was used up. Do you think this would be a problem and how noticeable would it be? Would I just figure on running with the tank mostly full all the time if it was far forward?
I think the sole replacement will be neutral for CG. Just as much weight fwd of CG (if we figure CG is center of the tank) as aft of it. There may actually be more weight aft of CG in the sole, so that would be a positive. I may do something like use plywood for the forward section of sole and Coosa board aft, which would make the new fwd section heavier than the aft. Plywood is twice the weight of Coosa sq/ft.
The battery was in the console before and will be there again.
Agree with you the lighter console will shift CG aft. Maybe I can make use of the old one just so it is heavier... So much work to fix it though... I plan to movie the whole console, leaning post, and T top about 6" forward. This will also put 2 people (mostly run with 2-3) 6" further fwd.
I always have chain on my anchor rode
You can't anchor here without chain.