That said, boating offers some spectacularly horrendous examples of what I call 'That Should Work' solutions - usually taken as an expedient fix with the idea that it'll get taken care of correctly later. But when a boat is built with these 'Gotchas' I am truly amazed.
Here's a case in point - Pelican has three water tanks, one each 50 gallons under the port and starboard settees in the main cabin and one 60 gallon tank under the v-berth. So far, so good. But the vents are not overboard - that's also a pretty good idea except in this case when the port tank vents into a hidden space, the starboard into a hanging locker, and I haven't found the vent for the bow tank yet.
Rerouting the vent is no problem - I've rerouted them to the bilge which is not the best idea but is better than venting into your clothes or somewhere else. I may change them to vent into the forward cabin's sink, which is the best solution. But that was a stupid engineering/builder decision.
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More to the point, to get to it you have to remove all the cushions and slide the berth extension out. How about not needing to do that each time you fill the tank, eh?
If you inadvertently fill the tank above the top but not enough to spill out the vent some three feet above the tank, you put approximately 1.3 psi on the tank, and that results on a total force of about 16 pounds over a 4" diameter inspection plate. That is enough to make it leak. And that doesn't take into effect the dynamic loading of water splashing about.
Ok, you say, you've lowered the vent. That should help, but the fill is 1.5" and the vent 5/8", so you could have a standing column that can essentially pressurize the tank to some 3psi including the dynamic loading of the force of the water - so even with the vent there will be leaking around the plate.
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They consist of a split back plate held together with a rubber gasket, a separate gasket for the top, and of course, a plate that's bolted on.
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Next: Installing instruments, frustration associated with that and living out of the water, and the good people at Raymarine.
My cruise starts next weekend, and I'll be seeing you on the water!
1 comment:
Your math is wrong as to psi on the tank. having a vent run 3 feet above a tank would indeed raise the pressure by 1.3 psi, however, you would be raising it for the square footage of the VENT LINE ID - it it's a 5/8" line, thats .3 square inches, or roughly 8 OZ of pressure, total
Applying this to your 4" deck plate, which has an area of roughly 12 .6square inches, equals a pressure of .03 psi.
In other words, the vent height adds no appreciable pressure to your tank whatsoever.
Heeling over at 25 degrees, however, places many gallons of water above the port, at 8 pounds per, puts considerable pressure on the inspection port.
Matt
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