using a tape measure is the best way and the preferred method according th o the US Navy.
yard
from the base to the tip.
A 21 foot boat refers to the length of the boat. There is not comparison between length and width. It could be narrow as on narrow boats or wide as in sea faring boats,
A D/L ratio is calculated by dividing a boat's displacement in long tons (2,240 pounds) by one one-hundredth of the waterline length (in feet) cubed.
The length of the boat.
use a metre stick
using a tape measure is the best way and the preferred method according th o the US Navy.
There are varied "correct" answers to this question, as many separate entities identify different meanings. Generally Length Overall (LOA) is a measurement taken along the hull, parallel to the waterline. In some instances it can also include the bowsprite to the fantail.
yard
from the base to the tip.
That depends what you want to measure - its length, its mass, its color, etc.
A boat's length overall dictates the equipment the boat must have to comply with federal and state laws.
A web reference states "The beam of many monohulls can be calculated by using the following formula."Beam=LOA(Length overall) in feet to the power of 2/3 +1Hope this helps.
You can do so in any unit but in backward countries people talk of boat lengths in feet because they use the imperial system. More properly they should use the international standard unit of length which which the meter and would be understood worldwide.
The length of a rowing boat may only be 6 feet. A large yacht may have a length of 100 feet. Of the two units of length given, then yards is more appropriate. In practice, the length of a boat is given in feet or metres.
The length of a motor boat is not restricted
The boat is on the river is correct