"Jere Lull" wrote

It seems you don't know the Chesapeake Bay well.

That's sure true. I've only sailed on it once and that was actually
motoring in a 380 foot Russian square rigged school ship. I'm working
however, for people who know it better than just about anyone.


The jets extend your baby's working area by tens of thousands of square
miles of the most environmentally "interesting" areas.

The difference in draft between the research vessel and a prop version is
actually surprisingly little. As measured, it would only be about a foot if
the prop version had partial tunnels as on the Woods Hole vessel. Not
having this expensive, delicate props and rudders right at the bottom though
means you can responsibly operate with less margin of water under the boat.
This is kind of a fuzzy figure and varies with weather and other conditions
but probably will usually let the jet boat operate in 2 - 3 feet less water
than the prop boat. Draft is still 4' - 8" at full load so a lot of the bay
is closed to her anyway. It's the region between about 6 and 9 feet that
will be more available to her than if she had props. Nobody has actually
calculated what that area is. Somewhere between hundreds and tens of
thousands I would guess


And you don't "plow" through an oyster bar, you *hit* one and stop very,
very quickly.

I didn't mean to imply that plowing through was part of the mission profile.
I expect the boat would stop. After backing or being pulled off however,
she ought to be able to continue working instead of heading for a shipyard.
She has a foot deep full length keel which is unusual for a power boat but
assists her station keeping and damps rolling. I expect that would go
pretty cleanly through a lot of stuff when they were lacking just a few
inches or a foot of draft, unlike a set of spinning props and rudders.

I forgot to answer Larry about the jets injesting stuff. The impellers in
these things are pretty industrial grade, think tree limb chipper rather
than jet ski plastic part. They will digest pretty much anything that will
fit through the intake grates and is low enough in density to either float
or be sucked up from the bottom. The impellers may get chipped and lose
efficiency but, unlike props, they don't immediately start vibrating so
badly that they have to be pulled. You can keep operating a damaged
impeller for quite a while.

--
Roger Long