Lindberg Jolly Roger float test.

I guess there is a formula.Some guys put a weight on the bottom of the ship that might be effective but sure is ugly!

philo426

I guess there is a formula

Well, buoyancy follows rules.

Measure waterline lenght (exclude rudder and keel)
x
beam width at widest at waterline
x
maximum draft waterline to top of keel

Multiply that sum by, oh, 0.67

That's your buoyant volume in whatever cubic units you used. 

A cubic foot of tap/pool/pond water weighs about 63 pounds.

Let's tack some values together.   LWL 11; BWL 5; DWL 2.38  thus 130.9 * .67 = 80-703 cubic inches. 
1728 cu.in. per cu.ft., so .005084 cubic feet.  Multiply that by 63, for 3.2030#.  Weigh the kit and subtract that from 3.2# to get your needed ballast weight.

But, there's a problem.  The kit CG (Center of Gravity) is way above where it would be in an actual ship.    This is why there are recommendations for a longer /deeper keel.  This is the loger the CG closer  to  the prototype's CG (just beloe the main deck, like as not.  The long moment arm also offset the undo forces wind will have on the top hamper.  Some of the "missing" ballast weight would need to be on that keel..

That keel could be as simple as some brass sheet, say 3" wide & 6" long with a steel plate along its edge, and a set of holes mactched to holes through the solid part of the keel, then fastened with a small seto bolts and nuts.  Or, a cotter pinof suitably small sixe.

I think you are a little generous with your BWL and DWL, but we both got the same results.

Somewhere between 1 and 3 pounds, so lets call it two. All at water line or lower.

A cubic inch of steel weighs 4.5 oz. so a seven inch long by 1" square bar weighs two pounds. I would have guessed more, but so be it. Or a ten inch long 1" diameter bar.

Now as far as pennies are concerned, a current one weighs 2.5 grams. About twelve pennies to the ounce, one hundred ninety two to the pound. Four of those bank roll ups get you to two pounds.

Philo, it's not ugly if its underwater. only the fish know.

Your Thermopylae would actually be a really good candidate for a pond floater. There is a lot of depth there in the hull, plenty of room for experimentation.

And MOST importantly, no open gun ports.

Yeah!I guess the whole thing is a lot more complicated than I thought.

Complicated?  Shoot, that was the Cliff's Notes version of the Cliff's Notes  :)

GM, what I was thinking  a bit of steel bat, oh 1/4 x 3/4 x 6-8" long screwed on the brass fin.

Ideally, a brass tube screwed to the brass fin, then filled with plumber's solder.

Was not over-concerned about  streamlining, a galleon ought to lumber along  a bit.  A clupper, now, that want's a bit of zip.

I have been thinking on this and here is a list of mistakes I have made.1.not sealing the gun ports 2.underestimating the weight of the masts,spars rigging and blocks which caused the wild tip when I put it back in the sink.3Perhaps the ship is too small for this to be viable.4.attempting to pour lead shot into the hull without regard to placement and balance.I am sure there are more so chime in dudes if I missed anything.

Don't want to hijack this thread, so started a new thread - Little Wood Flattie build in ships.

EJ

cool

E.J. ;

Your " Flattie " will perform well , I have two of them .They were for when My batteries on the big stuff ran down . Having fun with R.C. is always a blast ! .