wet keel

nickyp

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ok guys,

whats the deal with wet keels? from what i understand they are full of sea water and help stabilize the boat. maybe that answers the question, but what i want to know is how many boats have them , and who doesn't. and how this affects performance in all regards.
 

F/V First Team

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The wet keels lubricate the shaft bearings, that's the reasoning behind them. In wooden boats, which were the plugs for these new fangled fiberglass ones, the shaft log has some holes for water to lubricate the cutlass bearings. Since the fiberglass hulls are hollow due to the lack of wood in the keel the entire area fills up.

Fun times, makes for a slower boat.
 

harpoon83

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water weighs 8.35 lbs/gallon. Thats a lot of weight to carry around when you consider how much volume the shaft log area can hold.
 

RAMPAGE88

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So, am I wrong in assuming that my wet keel adds stability while on the drift, or on the hook? Furthermore, am I wrong in assuming that while steaming most of the bulk water has exited through the cutlass, therefore not really affecting my speed? Finally, if I'm wrong in my assumptions , what speed gains could be achieved by going over to a tube. Opinions?
 

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The water hasn't left your keel, but it has become static. There probably was a little bit of movement in the water while you were on drift, just being the nature of the water flowing. It's not so much that it is adding ballast but rather denying you of the buoyancy of that air pocket so you sit deeper in the water.

Think of it like you being in a life jacket. On land you weigh X. In the water you weigh considerably less than X because you're mostly water, so the water supports itself, that's why 37 lbs of buoyancy in a life jacket keeps you afloat when you weigh over 200 lbs. The water in your keel is supported by that water outside so it's not really ballast. Take that boat out of the water though and keep that keel filled up, now that's extra weight. Good way to break home made trailers.
 

BillD

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So, am I wrong in assuming that my wet keel adds stability while on the drift, or on the hook? Furthermore, am I wrong in assuming that while steaming most of the bulk water has exited through the cutlass, therefore not really affecting my speed? Finally, if I'm wrong in my assumptions , what speed gains could be achieved by going over to a tube. Opinions?

I'm NO expert but common sense tells me that a "wet keel" (heavier keel) makes for a more stable boat.

The last two days I've been "reminded" more than once about keeping weight "low in the hull".

Right Travis ? ;)

A wet keel keeps weight as "low as it goes" :D

Anybody ever measured how many gallons of water is in a wet keel?

Say a 30 Calvin Beal (Flowers East Coast)

or a 32 H & H ???
 

RAMPAGE88

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Interesting topic for sure. Any guesses on speed gains by changing over to a tube? I'm already getting a 16kt cruise out of 260hp. Is 1 to 2 kts a reasonable goal?
 

captainlarry84

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With the shaft always sitting in a keel of water, growth attaches to the shaft in the keel. This growth becomes drag on a turning shaft in water that has no where to go. That cost you a little, not a lot but every little bit helps on these boats.
The water weigh, never a plus in the speed department. Agreed some stability on the drift with the keel water

Wet tubes the shaft is spinning in force feed water down the tube causing no drag, plus no water weigh.

Converting a wet keel to a wet tube is not that hard. You already have your shaft angle with the bronze stern tube bearing. Went we do the switch over we put two hole saws on the same arbor. The first one to go one is the size of the outside diameter of the wet tube. The second one to go one is the outside diameter of the bronze stern tube.

The double hole saws will walk in at the same shaft angle that the original bronze stern tube had.

The rest of the job is pretty straight forward.
 

tunafishhkg

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Also wondering what if any speed gains on my 35 Duffy going to a tube especially at the hull speeds I and most are doing now to save fuel? Is it worth the change over that for me, able to do it myself, might be worth it. When I do my engine install on the 31 BHM this summer, for sure will go with a tube since I will be increasing my shaft size anyhow with the 450 6CTA and would not go old school.
 

Hurdy Gurdy

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What about installing a valve in the top of the wet keel box,run a hose so its above the water line.This would allow air in the box when running therefor less weight???Would it work?
 

petrel

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Does anyone have any real numbers as to increase in speed going from the original arrangement to a wet tube in the 31' BHM? I agree w/ Larry that fouling of the shaft by growth will create a drag, but I've inspected mine when changing zincs and it's not particularly encrusted w/ barnacles, like the my shafts get under the DMR, where they are exposed so that current can flow over them, and that is what grows barnacles in my experience. Sure it's not a smooth as a baby's ass, but as for significant growth inside that aquarium there was not nearly as much as I had expected to find in a 32 year old boat.
 

Overkill

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I don't agree with the theory that shafts in a tank will foul more with growth or they have more drag placed on them from the water in the tank. The shaft is in water in both cases and in total darkness , the same as in a tube.
 

BillD

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I don't agree with the theory that shafts in a tank will foul more with growth or they have more drag placed on them from the water in the tank. The shaft is in water in both cases and in total darkness , the same as in a tube.

Seems the opinions are a "draw".

Let's change the question just a bit.

On a "new build"..........

What is the "least expensive way" to shaft the boat?

Wet tube/dry keel.........?? $$$
Wet keel.....................?? $$$
 

WoundUpMarine

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