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Topic: Ballast tank airvent (Read 177 times)
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Colin Lawson
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Hi, does anyone have any advice on position of an airvent for ballast tank as recommended by Claus. He put his immediately behind the centre board case below his GPS. But if your GPS is on top of the centre board case as mine is, an air vent in front of the CB case would be in the way and liable to be damaged by feet looking for something to brace against. Has anyone tried putting the vent in front of the centre board case. I know the battery usually goes there but re siting the battery off the deck might be a good idea anyway.Where does the air collect/get trapped? At the front of the ballast tank or at the back.
Thanks in advance for any words of wisdom.
Colin (looking forward to taking his BR20 to Falmouth first week in June and then again at the beginning of July)
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Craic
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Hi Colin,
the airvent is a MUST. Where you put it is very much your own decision, the boat wave movement in connection with the water coming in under pressure through the bung will quickly drain any airpockets. Absolute best position would be in front of the centreboard case. BUT, to retrofit one, you need to get your hand in underneath to screw the counter nut on the thread from inside the tank.
That is why I put my vent(s) behind the centreboard case where the main hatch allows access from underneath. That position works well enough, as you can watch how first the air burps out, and thereafter some water fountains out. That would be the right moment to open the main hatch again, close the inlet bung and sail away happily ever after ... .
C.
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Colin Lawson
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Thanks Claus - I think I will go with your advice, seeing when the tank is full sounds like the deciding factor.
Colin
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Graham W
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I installed a lean-to piece of wood astern of my centreboard case to hang instruments off, in this case a Tackticks wind indicator (see photo). My ballast tank vent is hidden and protected in the triangular shaped void between the case and the instrument board. As an additional source of information about what is happening in the ballast tank, a transparent watertight inspection hatch cover is available to replace the Henderson TCL4 red and black one that is fitted as standard equipment. Seamark Nunn sell it http://www.seamarknunn.com/acatalog/info_MTLD4002.htmlI found my watertight hatches increasingly difficult to open as the threads became crusted up with salt and general muck. As well as cleaning them up, I coated the threads with silicone grease and now they are much easier to open and close. Same thing with my ballast tank bungs. |
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GRP BR20 #59 Turaco III
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John Davis
Jr. Member
Posts: 7
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Claus and all,
I\\\'ve just read this string and wondering why an airvent is a must. I have not put one in yet and have had no problems filling or exhausting the tank. Under what circumstances do you find it to be particularly useful?
Thanks, in advance, for your advice.
John
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Craic
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John,
to let 300 ltrs. of water in one must let 300 ltrs. of air out, and vice versa, and quickly, in order to keep the transitional free surface situations as short as possible. So how do you vent your tank now? Through having the main hatch open during the process? That is not a good idea, think of what happens if you would heel over or capsize with the main hatch open.
And if you open the main hatch just a little, in an attempt not to risk it falling out, the throughflow of air is limited, especially during emptying the tank, because then the air suction will suck the hatch down onto its seat and seal. Been there... .
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Matthew P
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Rather than make another hole in my BR20 I have fitted (screwed and Sika-flexed) a small drain plug into one of the forward hatch covers, which seems to work well and has so far has stood up to my large feet. It is surprising how much faster water floods out of the tank from the other end when the vent is opened.
Following Clause s lead I have fitted a drain plug into the sump from which I can pump it out with a Whale Titan pump. I will post a picture of this under a new string; Sump Pump.
Matthew
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