Propellers, Shafts & Rudders

propeller & rudder
modern brass propeller
A huge modern brass propeller ( from the SS United States ) on display.
shipwreck Delaware propeller
Looking down the prop shaft at the iron propeller on the Delaware. The narrow squarish blades indicate that this is a rather primitive 1880's model, unlike the more modern rounded prop on the Macedonia below.
shipwreck Macedonia propeller
The propeller on the Macedonia.
shipwreck Macedonia shaft mount
Propeller shaft bearing and mount on the Macedonia.
reef Venturo propeller
The propeller on the GA Venturo - a completely modern design. Note the wide, round blades.

Breaking a propeller shaft at sea can be a disaster. The propeller stops turning and becomes a drag, while the vessel's momentum carries it forward. The propeller slams backward, extracting the broken shaft and often mangling the rudder. This leaves a large hole open in the bottom of the vessel, directly into the bilges and machinery spaces. On a large vessel with a deep draft and a large shaft, the water comes in like a fire hose - uncontrollable.

The engine is soon disabled, and along with that the pumps, which in any case are probably not big enough to keep up with this magnitude of flooding. The outcome may take several hours, but it is inevitable unless maybe the Coast Guard can fly out a special de-watering pump on one of their big helos. Unlike a collision, storm, or rogue wave, there is usually plenty of time for an orderly abandon-ship, and there are seldom casualties if rescue is available.

Shipwreck Emerald
The "Emerald" fell victim to a broken prop shaft in 1873, and the Lady Gertrude sank the same way in 2016.
shipwreck Oregon steering quadrant
The fallen steering quadrant on the Oregon, perhaps 20 ft across.
shipwreck Tolten steering quadrant
Tolten steering quadrant
Tolten steering quadrant
The steering quadrant on the Tolten

no snorkel

Here is an item that is useful in the tropics, but much less so around here. This is because the water here is not nearly as crystal clear as in the tropics, and the depths are often greater. Therefore it is unlikely you will be able to see anything interesting below from the surface.

On a boat dive, a snorkel is totally useless - leave it home. Chances are, the captain and crew will tell you to take it off anyway. The same is generally true for inlet diving where the entry is steep. A snorkel is just one extra thing to get tangled up, and you will probably have enough of that already. A snorkel might be useful in a surface swim from the beach out to a close-in dive site, if it is a good one with purge valve or a dry valve to keep the water out entirely. Even then, you are better off doing a backstroke out to the site, with your head out of the water so you can navigate by landmarks, or an underwater swim if the currents are favorable.

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