502stang

OK..Today is a new day!! It is time to move onward and upward. I was talking to my older brother yesterday. The one that still has the fastest boat in the family. He asked me if I had my boat balanced yet. I said not really...He said that in the high performance bass boat world that they balance the boats pretty precisely before they go up around the triple digits and beyond. He said that it was a "no brain er" to move weight around add ballast where necessary to balance the boat. He says that not only does it make the boat a lot easier to drive and a lot safer but it makes it faster even if you have to add ballast (weight). In a 110 to 120 MPH bass boat they know exactly where they want this center of balance. He says that it needs to be where if you had a pointed stake sticking up and you set the boat(in their case with the driver) the boat would balance perfectly side to side and fore and aft.


My question.....Where would you want this point to be in an offshore boat like we run? Are there companies or people that ballast these boats like the bass boats? Has anyone here gone to that point of balancing to that fine of a point? If there are people here that have done that ...... what were your thoughts?

stevesxm

intuition says that he has to be correct. the dynamic forces in effect at even 70 mph are very large and the inertial aspects of mass location have got to be important to offset them or enhance them as the case may be. on my boat , a 10,000 lb top gun, i drove the boat before i bought it with allegedly a 1000
hp. it went 62 mph and handled "average" i thought.

i repowered to about 850 hp and worked very hard at centralizing the mass which meant getting as much heavy stuff as i could move toward the CG. i did this based purely on my own theoretical undestanding, not anything i would represent as fact based knowledge. when i got done it went 68 mph and handled much much crisper and more positive i felt.

502stang

My boat weighs about half of what yours does..Do you know if there is any kind of device to balance your boat. I know that I have talked to IMCO and Arneson and they talk about having the lateral center of gravity 4-6 feet from the transom. How do you measure where your lateral center of gravity is?

stevesxm

the answer to your question would be as simple as working a simple calculation based on your trailer tounge weight or with the trailer on scales... but how would you significantly change it anyway? what do you have in the boat thats really heavy that you could move around ? for me it was batteries and firesystem and a lot of spares etc. do you have 200 lbs worth of stuff to relocate ?

502stang

I think that I will have to use ballast to correct any balance issues. I don't have enough stuff to move around to make the difference.

hallj

How would this method separate out the the weight distribution of the trailer from the boat?

Jeff

502stang

I got some information today. I talked to Rick at Arneson. The Lateral Center of Gravity should be 25% of the length of your hull from the rear of the hull. He said the best way to determine where yours is would be to run a strap under your boat and pick up on it with an overhead crane or something like that.Just pick it up a little bit. If it falls forward. You LCG is forward of that point. If it falls back then it is AFT or that location. Then you can move stuff or ballast accordingly.

DMOORE

One problem with the weight balance with "boat on trailer" is , if you have a triple trailer, the axles carry almost all the weight. The tongue carrys very little.



Darrell.

BenPerfected

Interesting comment on the 25%. The GC on my 30' Scarab (actually 29' 6") is at 91" or 25.7%....pretty close. There are more options to move weight than you might first think. Can you move your batteries (80-100 lbs) towards the transom? Trim pumps? Remove any misc from bow area? Varying your fuel load might help depending on the tank location. Some race boats move fuel from tank to tank during the race to maintain balance/attitude.
Extension boxes can really help as this moves the drives back 12" which will likely have a big impact on the CG.
You should be able to use a travel lift at many marinas to hang your boat in one strap. You should be at the helm and have 3-4 sand bags handy to test with. The first step is to find out which way you want to go.

stevesxm

you wouldn't. you don't care about the real numbers only a location. if it where a heavy boat like mine on a triple axle , i would run the center wheels up on a couple of 2 x 8's such that the took most of the load . then you look at the tongue weight.
you don't need to know it to a decimal place... just whether its a 100 or 25 or 500... you do it w/ out the boat. then you go get the boat and do the test again with the same 2x8's... if the tongue weight is the same as when it had no boat, then the cg is over the center axle. if its heavier, move the boat back until its the same... or forward if its lighter. when its the same as it was w/ no boat, then the cg is over the center axle. ill bet if you are careful, you can get it w/ in 6 inshes. if it was a 2 axle trailer, do the same thing or take two of the tires off... either way, i think you could identify a problem if one existed...

but having said all that... is your configuration so much different than others that you suspect this is a real problem or are you just trying to do whatever you can do for free to make things better ? i would think twice about ballasting a lot. weight is power. putting in the equivilent of another person will offset any balance gains you might make. especially in a low powered boat.

in my case i stripped all the junk people had hung on this boat that didn't do anything and got rid of a couple hundred pounds. i would have to believe there was a critical issue for me to consider putting it back.