Pressurizing the ballast tank will only push out enough water until the air bubbles can escape. Essentially it is impossible to blow out the water completely. Picture a pop bottle filled with water and submerged in water. Punch a hole part way down the body and place a straw in the top and start blowing. Water will start to be pushed out of the neck hole but as soon as the water is displaced to the top of the neck hole, air will now just escape and stop displacing water. At this point you would be better off closing the intake hole and sucking the remaining water out.
Just basic physics.
Ballast Bilge Pump
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Trouts Dream
- Captain
- Posts: 663
- Joined: Thu Dec 14, 2006 12:10 pm
- Sailboat: MacGregor 26X
- Location: Calgary, Alberta--1997 26X--Yamaha 90HP 2 Stroke....grunt, grunt
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RickJ
- First Officer
- Posts: 292
- Joined: Mon Oct 01, 2007 2:39 pm
- Sailboat: MacGregor 19
- Location: Isle of Wight, UK - '94 19 + Tohatsu MFS30
I can see that might be a problem. But Louis' idea is to just open the transom gate valve a small amount, so the water level would have to get down to almost the bottom of the opening before air could escape. This should be pretty well at the bottom of the ballast, esp. if the boat is stern-heavy at the time.
Of course if the gate slide allows too much air to leak around the sides then that idea won't work either! It will also restrict the opening which could mean it would take a long time to empty.
There's a big theory v. practice issue here.
(Did you know that the difference between theory and practice is greater in practice than it is in theory?
)
Cheers, Rick
Of course if the gate slide allows too much air to leak around the sides then that idea won't work either! It will also restrict the opening which could mean it would take a long time to empty.
There's a big theory v. practice issue here.
(Did you know that the difference between theory and practice is greater in practice than it is in theory?
)Cheers, Rick
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Frank C
When my boat's on-plane (whatever that means) for emptying ballast, the gate valve is clear of the waterline. As the ballast empties, you can actually see that the hull is rising higher and the valve is fully clear of the water. At process-end, there's just a very slight trickle of ballast still exiting the valve.
Granting though ... this is with the Suzuki 60. Still, even with the Suzi-50 I'd be looking for that ballast valve to be clearly above the waterline by about 8 minutes after the gate valve is opened.
Granting though ... this is with the Suzuki 60. Still, even with the Suzi-50 I'd be looking for that ballast valve to be clearly above the waterline by about 8 minutes after the gate valve is opened.
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ALX357
- Admiral
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- Joined: Thu Jul 22, 2004 6:09 am
- Location: Nashville TN -- 2000 MacGregor 26X, Mercury two-stroke 50hp
Run the motor WOT, for as long as it takes, usually about the commonly agreed-upon 8 minutes, until the top speed no longer increases and is leveled off as told by the GPS. That's how I determine the ballast is all out.
Especially since I never even go looking in the vent anymore, after installing the passive vent hose system.
One other trick I learned even before I bought my MacX, is to open and close the gate valve from over the transom by using a specially sized (shortened) boat hook, with its own clips for attaching at the transom wall next to the rudder lines, and with the plastic point ground off and flattened, so it is easy to push down the Mac T-handle, or use the hook to pull up on it to open. That way, the gate valve gets closed while at top speed, by just reaching over the helm seat, to ensure that no water can get back in. It also avoids having to open the helm seat with the hatch cover fastened behind it.
For an indicator of filling, a stainless steel hose clamp surrounds the vent tube, with a piece of red ribbon just long enough to turn into the vent hose and not get stuck in the valve, which can be seen to get sucked into the tube if the ballast is filling, or float lazily around outside the hole when the water is no longer entering the tank.
Especially since I never even go looking in the vent anymore, after installing the passive vent hose system. One other trick I learned even before I bought my MacX, is to open and close the gate valve from over the transom by using a specially sized (shortened) boat hook, with its own clips for attaching at the transom wall next to the rudder lines, and with the plastic point ground off and flattened, so it is easy to push down the Mac T-handle, or use the hook to pull up on it to open. That way, the gate valve gets closed while at top speed, by just reaching over the helm seat, to ensure that no water can get back in. It also avoids having to open the helm seat with the hatch cover fastened behind it. For an indicator of filling, a stainless steel hose clamp surrounds the vent tube, with a piece of red ribbon just long enough to turn into the vent hose and not get stuck in the valve, which can be seen to get sucked into the tube if the ballast is filling, or float lazily around outside the hole when the water is no longer entering the tank.
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tangentair
- Admiral
- Posts: 1234
- Joined: Mon Jan 22, 2007 11:59 am
- Sailboat: MacGregor 26M
- Location: Highland Park, IL ...07M...Merc 50 BF...Mila K
To each his own I guess, I just pull up on to the trailer, open the valves, pull up until the valve is clear of the water and wait the 3 or 4 minutes (if that long) till it empties. I have had some people come up and ask why I have not cleared the ramp and I tell them my ballast is draining and I will clear in 3 minutes when it dumps. They have always walked away and waited. Then I pull out and start the prep. I am like puggys, I just prefer the handling with the ballast in and like to sail till the last moments. Of course Lake Michigan around here gets deep pretty quick so as I said, to each his own.
Why not leave the stern valve closed, get two hoses run them through a stopper that will fit in the vent leave one long with a weight so it lays along the bottom of the tank and one short. Connect an air pump to the short one and run the long one out and over the side. You could rig this with 12v wet vac, that way you could reverse the lead to the wet vac and suck in the ballast twice as fast also.
Or get a long piece of hose, drop it in through the vent, rig it to a venturi and use air or water to spray it out.
Why not leave the stern valve closed, get two hoses run them through a stopper that will fit in the vent leave one long with a weight so it lays along the bottom of the tank and one short. Connect an air pump to the short one and run the long one out and over the side. You could rig this with 12v wet vac, that way you could reverse the lead to the wet vac and suck in the ballast twice as fast also.
Or get a long piece of hose, drop it in through the vent, rig it to a venturi and use air or water to spray it out.
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Frank C
I suppose different goals justify different techniques. It's fine for me also to just empty ballast on the ramp, when retrieving the boat is my goal.
But sometimes emptying ballast is targeted at enabling motoring across fairly flat water. In that case, eight minutes at WOT is SOP, much quicker than I've ever noted in reports here of emptying ballast by pumping air, or the ballast itself ... which ranges from 25 to 40 minutes.
I rarely undertake 30+ minutes of motoring unless I've emptied ballast. When I'm late heading off the Bay, it could easily take 30 to 40 minutes of motoring at 12 mph to reach the slip .... which motoring is much "easier" on the hull and crew when ballast is empty ... JMO.
Understand too, sailing the center of SF Bay is the gold-ring. Spending a late afternoon out there is invigorating .... after which it's pretty boring to sail the downwind home-run in the gathering darkness, all the more reason to empty ballast, whenever conditions permit.
But sometimes emptying ballast is targeted at enabling motoring across fairly flat water. In that case, eight minutes at WOT is SOP, much quicker than I've ever noted in reports here of emptying ballast by pumping air, or the ballast itself ... which ranges from 25 to 40 minutes.
I rarely undertake 30+ minutes of motoring unless I've emptied ballast. When I'm late heading off the Bay, it could easily take 30 to 40 minutes of motoring at 12 mph to reach the slip .... which motoring is much "easier" on the hull and crew when ballast is empty ... JMO.
Understand too, sailing the center of SF Bay is the gold-ring. Spending a late afternoon out there is invigorating .... after which it's pretty boring to sail the downwind home-run in the gathering darkness, all the more reason to empty ballast, whenever conditions permit.