Boat physical dimension and what they mean on the water

[salmonee]

Can someone explain what the physical dimension of the boat means when your out on the water. This may be a dumb question, but I'm new. For example, if you took two bow riders and equal length, deadrise, etc. But one of the bow rider is physically taller by say 12", what advantages/disadvantage does the taller boat has over the shorter one? Another question that I have is with regards to the "draft" specification. I believe this means how much of the boat sits below the water line including the bottom of the outboard if equipped. Assuming two boats are the same size, how does the draft specification affect the boat performance? Thanks in advance.

 

[haskindm]

Re: Boat physical dimension and what they mean on the water

There are an infinite number of variables to boat design and each manufacturer tries to determine the "best" design for their customers. Generally the taller the sides of the boat are, the drier the interior of the boat will be, and the rougher water it can handle. This is a gross oversimplification, but you get the idea. Look at the typical boat designed for offshore fishing. They will usually have a deep V shape to the hull to break through the chop and tall sides to keep water outside of the boat. The disadvantage is that it takes allot of power to get a boat like that on plane and it draws more water (draft). A boat with a flatter bottom will plane more easily, be faster for any given horsepower, and have less draft. Everything is a compromise. You will need to decide which boat's design most accurately meets your needs. Compare an offshore fishing boat to a bass boat to get an idea of the difference. The offshore boat will have a very deep V design where the bass boat is much more flat. The offshore boat is made to handle the roughness of the ocean or a large bay. The bass boat is designed to go very fast in relatively calm water. The fun is in the choosing!

 

[erikgreen]

Re: Boat physical dimension and what they mean on the water

...and don't forget cupholders and cooler space, for god's sake.

 

[dingbat]

Re: Boat physical dimension and what they mean on the water

Draft is the hull only. Its does not include the propulsion system.

The higher sides (freeboard) don't necessarily relate to a drier ride. I?ve ridden in some very wet, high sided boats. What freeboard does buy you is less chance of taking water over the side and less chance of you falling out.

 

[QC]

Re: Boat physical dimension and what they mean on the water

But one of the bow rider is physically taller by say 12"

This dimension is "freeboard" which dingbat has referred too. It is usually the distance to the top of the "gunnel" (top of the sides) or lowest deck from the waterline.

what advantages/disadvantage does the taller boat has over the shorter one?

Often drier as some have stated, but a disadvantage is that higher freeboard boats typically have a higher center of gravity which can make them more affected by weight shifting from side to side and they may not handle as well. My wife is used to low freeboard, sporty boats and she literally hates riding in a higher freeboard boat. An I/O (low CG) in a low freeboard boat, with decent deadrise (20 degrees+) is very comfortable in chop and even rougher water at high speeds.

I believe this means how much of the boat sits below the water line including the bottom of the outboard if equipped. Assuming two boats are the same size, how does the draft specification

Draft spec is often listed drive up and drive down. With two identical boats, the one with the lower draft "drive down" will typically be a little slower (more stuff in da wawa) but may get out of the hole better (more bite). If all else is the same their draft with the drive up should be identical assuming that the drive will raise above the bottom which they don't . . .

 

[mrdancer]

Re: Boat physical dimension and what they mean on the water

It all depends...

I run a 26-foot flat-bottom mod-V aluminum with five foot bottom width. It rides nicely in a chop. With 22-inch sides, I've been comfortable with it in 3-footers and the boat is heavy enough that the ride wasn't unbearable. It is also a (pocket) tunnel hull, so its draft is about 6-7 inches for the boat itself, then another five inches for the part of the outboard and propeller that is below the boat. There is no bow rise on takeoff, so I can jump up on plane in a foot of water. Since water is noncompressible, I can run over areas of 6-inch water or less for short distances (the pressure of the shallow water raises the hull of the boat as the water tries to escape out the sides).