Re: [PSUBS-MAILIST] ABS hatch rules and alvin

["Cliff Redus" <dr_redus@devtex.net>]

To be specific, ABS says in Section 3.19.1a under Intact Surface Stability:
" In addition, the distance from the waterline to the top of coamings around
the hatches which may be opened with the unit afloat is to be not less than
2.5 ft. with the unit upright."
 According to Webster, a coaming is a raised frame (as around a hatchway in
the deck of a ship) to keep out water.

So it is the coaming opening that has to be 2.5 feet above the waterline,
not necessarily the hatch.  This particular ABS rule makes it very difficult
to design a small, streamlined psub and meet ABS rules.  Yes freeboard is
important to keep your boat from swamping with the hatch is open but I hope
in future years, ABS will modify this rule so that the minimum freeboard is
calculated based on some characteristic length of the boat such as the hull
diameter, i.,e, a smaller boat should require less freeboard than 2.5 ft.

Cliff



----- Original Message -----
From: "Lucas Gray" <lgray@tera.engr.mun.ca>
To: <personal_submersibles@psubs.org>
Sent: Saturday, April 13, 2002 9:06 PM
Subject: [PSUBS-MAILIST] ABS hatch rules and alvin


>
> I've heard and read that the ABS hatch rules are require about 2 feet,
> from the hatch to the water line. The alvin submersibe does not appear to
> have this but instead has a free flooding (fiberglass?) conning tower that
> appears to have flood holes below the waterline. I assume that these holes
> are oneway valves such that after the water drains out a passing wave will
> not let water come back in. so the pressure hull hatch is at the water
> line but the entrance hatch is 3? feet above the waterline... does this
> simple modification satisfy the ABS rules..? if not, is the alvin
> insured? by who?
>
> lucas
>