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Initial Stability vrs Sea Keeping Ability.
|No one wants
to build a boat that is labeled as 'Unstable'. Small
boats that are unstable are considered to be dangerous,
and we want to avoid this flaw at all costs, when
considering a design to build or purchase. The question
is How do we determine whether a particular small boat
design will be stable or unstable?
In considering the design elements at play here, we first need to come to terms with the 'having your cake and eating it too' problem that every small boat builder or designer must take into consideration. The fact of the matter, is that there are Two Stability Considerations that we must examine in All small boats, 'Initial Stability' and 'Sea Keeping Stability'.
Initial Stability in Small Boat Design:
Initial Stability can best
be explained as follows: Initial stability is how stable
the boat is when getting into or when exiting the boat,
as well as how stable the boat is in regards to moving
around inside of it.
One can Further Define initial stability here, to include factors such as which small boats rail will go Under First, when heavily loaded to one side by a person literally stepping on the rail to try and enter the boat. One mention of the term Bank Dory ought drive this nail firmly in place, the semi-dory is another small boat design that may stand up to this test in lengths down to 15 feet.
Bottom Weight is also a help in increasing initial stability, to Demonstrate this in Your boat, try this simple and easy test. Step into the boat with your first foot placed right up against the inside of the garboard right at the beem. Now try it again, this time, first chucking 50 or more pounds of gear on the bottom of the boat and on the centerline. You should note a small increase in 'initial stability' with the gear first added.
Sea Keeping Stability in Small Boat Design:
The Statement, 'flat
bottom boats are no good in a sea or swell', does have
merit, but the gloster dory has a problem with the
statement. A gloster, or a Grand Bank dory, in sizes
ranging from 16 feet and up, if built along traditional
lines, are Extremely Difficult to capsize actually, you
really have to work at it. Why?