How much draft

Can someone tell me what the draft will be on an 8' x 48' (pontoon boat) hull assuming that the hull weight is 7400 lbs.

Thanks

 

I make it about 4" assuming 7400lb is the total weight and she floats level

 

Draft

Can someone give me the formula for calculating draft on a flat bottom hull.

Thanks

 

You say "pontoon" but you don't say what size the "pontoons" are so I will assume you mean one open bargelike hull and not true pontoons. Fresh water weighs 62.4 lbs a cubic foot and salt water weighs 64 lbs. If your 8' x 48' hull was 1' high, with straight up and down sides and ends like a box, it would amount to 384 cubic feet. (8 x 48 x 1 = 384) In salt water the total weight of your hull and cargo would theoretically be 24,576 lbs before it would sink. (384 x 64 = 24,576) Dividing by 12 would give you the displacement per inch of draft. (384 / 12 = 32, 32 X 64 = 2,048) OR (24,576 / 12 = 2,048) So each inch of draft displaces 2,048 lbs. of saltwater. 7,400 / 2,048 = 3.6132812. So your 7,400 lb hull would have a draft of 3.6" in saltwater, which is pretty close to 3 5/8". Each additional 93 cases of beer would increase your draft apprx. 1". Hope this wasn't too confusing. Sam

 

I'm humored Sam

 

If the pontoons are round, find the volume of the cylinders, if they are of another shape, dig out the old math book (geometry) and figure out which it is closest to then find the volume of the shape. It takes 64 lbs to displace 1 cubic foot of salt water, 62.4 lbs for fresh water.

Steve