smiklos@sunprint

iTrader: (1)

In the end final CG is preference that is representented in a number. A well balanced boat like an airplane is a joy to operate. An improperly balanced boat or plane can kill you.


You want a boat that flies long flat and level.
Steve

stevesxm

thats correct. but you trim your aircraft in flight using adjustable control surfaces... just like a boat. the weight and balance are done when its built so that the cg corresponds with the center of lift of the wing. all you have to do is be careful where you put your passengers and luggage. i suspect there are similar centers of pressure both aerodynamic and hydro dynamic on the hull at speed and that it would be really helpful to have that near the cg.

the further apart you get the two, the greater the moment arm and higher the polar moment of inertia will be when you go to turn it at speed. that will translate into a sluggish reaction time and lots of scrub and drag. and , i suppose could make the boat be less user friendly in rougher water as well...

oh well... all well known and understod in the aircraft industry but theoretical as far as these boats go because the hulls are so dissimilar... it would be interesting to know what's actually true in fact.

Tampa38

Simple method from a friend that raced, owned a marina, etc.

He said that the most important factor was the side to side balance, put 2 peices of electrical tape on either side, measuring so if the boat was perfectly level they will match up at the waterline.

Launch the boat and move weight as needed, now you are balanced side to side and will pick up some mph.

502stang

Thank you!! That is my point!

502stang

Great idea!!

hallj

Interesting. I used 3 scales and came up with 26% Longitudinal(front to back) cg. Cool.
I'd like to post pics of my setup but this site charges extra for that, bummer.
Jeff

ChristianGott

hey..
my bow likes to pop all over with minimal drive input. i've always thought that a few extra lbs in the bow...like 100... would "settle things down" (twin sbc's in a 26'er), thus really letting the drives and tabs do their job. a more level ride w/o dragging tabs must surely improve efficiency?
c

CcanDo

The 26% represents a working number to create a CG envelope. As loading and/or load locations change, the CG will move within the envelope. Therefore,variables such as a high X,heavy load,hot dry days etc. may cause the boat to have trouble getting on plane.

Therefore,is it prudent to include a forward located ballast tank in this discussion?

BenPerfected

Cat,
We have a ballast tank in our boat but don't use it often. The thought was a ballast tank in the bow would allow us to run faster overall in the bumps while using less tab. I expect there is a balance of both ballast and tabs but we never figured it out. How do you measure the results? It seems we could exceed the speed we were comfortable with using either system.
I would like to hear move from others that use a ballast tank. Is a ballast tank mostly a band aid for a poorly balanced boat?
Steve, do you race with a ballast tank?

smiklos@sunprint

iTrader: (1)

Yes. The tank is good because you can add to overall weight. With it being forward of the CG you have to be careful of bow steer or worse. Using the tank dampens the polar movement and gives you confidence, sometimes too much! If you do stuff the tank really aggrevates the situation.

The other nice effect I feel is you can run your CG a little aft to get the acceleration and top speed but if you need to settle things down a little water in the nose really helps.
Steve