This is probably a stupid question..but my swing keel has lines that go from the top of the board, over one block, to the back of the boat, under another block, and up into the cockpit. Why doesn't water come though this passage into the cockpit? am i missing something?
Why doesnt it sink!
- Thread starter Brian M H23
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In this case atmospheric pressure has nothing to
do with the question. Just as you have a water line on the outside of the boat you could also paint that line on the inside of the boat. That is where the boat floats. When the boat heels the actual water line shifts but the volume of the boat that is submerged remains the same. As you add people and cargo to the boat the additional weight causes the boat to settle deeper in the water in order to increase the volume of submerged hull. If you fill a bucket brim full of water and float a chunk of wood in it some of the water in the bucket will spill over the top, when you remove the wood from the water the bucket will no longer be brim full. If you drill a hole through the chunk of wood it will still float as before with the water rising part way up through the hole. The amount of water spilled is the displacement of the wood. Your boat does the same thing and the water that is displaced spills off the edge of the earth.
do with the question. Just as you have a water line on the outside of the boat you could also paint that line on the inside of the boat. That is where the boat floats. When the boat heels the actual water line shifts but the volume of the boat that is submerged remains the same. As you add people and cargo to the boat the additional weight causes the boat to settle deeper in the water in order to increase the volume of submerged hull. If you fill a bucket brim full of water and float a chunk of wood in it some of the water in the bucket will spill over the top, when you remove the wood from the water the bucket will no longer be brim full. If you drill a hole through the chunk of wood it will still float as before with the water rising part way up through the hole. The amount of water spilled is the displacement of the wood. Your boat does the same thing and the water that is displaced spills off the edge of the earth.
When the opening is below the waterline ...
Then you will sink. The same accounts for any other underwater thru-hull opening. When I disconnect my water intake hose from the filter (inboard engine cooling system) and hold it up ... no water comes out. When I let it drop to the hull, the boat fills with water. When your boat is filling with water, the water line keeps dropping until you sink.
Then you will sink. The same accounts for any other underwater thru-hull opening. When I disconnect my water intake hose from the filter (inboard engine cooling system) and hold it up ... no water comes out. When I let it drop to the hull, the boat fills with water. When your boat is filling with water, the water line keeps dropping until you sink.
Phil
Where is the floor of the cockpit (or the top lip of that channel) with respect to the waterline?
Where is the floor of the cockpit (or the top lip of that channel) with respect to the waterline?
The opening to the cockpit ...
looks like it is at seat level, several inches above the water line. The water line appears to be just above the first block coming off the centerboard, and about the same level as the second block, where the channel goes vertical. Inside the channel, the water will only seek the level that is equal to the water level outside the boat. If you punched a hole in the bottom of the cockpit (below the outside water line) to the channel, then your boat would fill with water. As it is, when you are sailing, the water only goes up the channel to the water line. Those two blocks may be underwater. If you were heeling way over, I suppose there may be a chance that a little water would splash up thru the channel, but that would only be temporary and a small amount, and it would have to be pretty extreme.
looks like it is at seat level, several inches above the water line. The water line appears to be just above the first block coming off the centerboard, and about the same level as the second block, where the channel goes vertical. Inside the channel, the water will only seek the level that is equal to the water level outside the boat. If you punched a hole in the bottom of the cockpit (below the outside water line) to the channel, then your boat would fill with water. As it is, when you are sailing, the water only goes up the channel to the water line. Those two blocks may be underwater. If you were heeling way over, I suppose there may be a chance that a little water would splash up thru the channel, but that would only be temporary and a small amount, and it would have to be pretty extreme.
hmmm
After some investigation, I've remembered that the same two holes are also the cockpit drain. Why this works is still kind of conufusing..the waterline is right below the lip of the transom. But obviously the forces at work are making water go down the tube, not up. The link is to some drainage information about a boat with a similar system that claims to have water come up through the drain if the boat squats in the back..I assume the same applies to me? But, I think I get it. The water would have to magically climb up above the waterline before it could go anywhere. Now, if the channel from the waterline to the cockpit were to break, I'd have a problem. Thanks!
After some investigation, I've remembered that the same two holes are also the cockpit drain. Why this works is still kind of conufusing..the waterline is right below the lip of the transom. But obviously the forces at work are making water go down the tube, not up. The link is to some drainage information about a boat with a similar system that claims to have water come up through the drain if the boat squats in the back..I assume the same applies to me? But, I think I get it. The water would have to magically climb up above the waterline before it could go anywhere. Now, if the channel from the waterline to the cockpit were to break, I'd have a problem. Thanks!
No way to sink!
On smaller boats with a centerboard that pulls out you can see the water coming up the slot. But even if you drilled a 6" hole through the bottom, your boat wouldn't sink. I thought Hunters up to a considerable length were designed with a positive flotation hull.
On smaller boats with a centerboard that pulls out you can see the water coming up the slot. But even if you drilled a 6" hole through the bottom, your boat wouldn't sink. I thought Hunters up to a considerable length were designed with a positive flotation hull.
You hit on it...
Indeed it is a manifestation of nautical magic. The water molecules actually know whether you want them to come aboard or stay out of the boat, and they are acceding to your wishes. Seriously, my boat has a vertical tube up which the centerboard cable passes. The top of the tube is not too far above the boat's waterline, and on any day when the sailing has been, well, 'spirited', we will take on a measurable amount of water when it splashes up the tube. A sponge jammed a little way down the tube helps keep this to a minimum, however.
Indeed it is a manifestation of nautical magic. The water molecules actually know whether you want them to come aboard or stay out of the boat, and they are acceding to your wishes. Seriously, my boat has a vertical tube up which the centerboard cable passes. The top of the tube is not too far above the boat's waterline, and on any day when the sailing has been, well, 'spirited', we will take on a measurable amount of water when it splashes up the tube. A sponge jammed a little way down the tube helps keep this to a minimum, however.
- Jan 22, 2008
- 519
wl and cockpit drains
Simlarily, my cockpit drain shows the water level at just an inch or so below the floor of the cockpit, but my boat also requires 403 additonal pounds to sink it that one inch further. Add to that the venturi effect which sucks water out when the boat is moving, and there is no way that water comes up that hole when underway. As Bob from Virginia states, the water knows where to go!
Simlarily, my cockpit drain shows the water level at just an inch or so below the floor of the cockpit, but my boat also requires 403 additonal pounds to sink it that one inch further. Add to that the venturi effect which sucks water out when the boat is moving, and there is no way that water comes up that hole when underway. As Bob from Virginia states, the water knows where to go!
So thats to say...
If two fat pirates boarded and held you hostage, the boat would sink?! As for positive flotation..Does the 23 have it? I havent heard such a thing yet.
If two fat pirates boarded and held you hostage, the boat would sink?! As for positive flotation..Does the 23 have it? I havent heard such a thing yet.
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