Ballast vacuum

[tdc_worm]

I have sacks plumbed on top of all 3 tanks on my 06 220. When I drain the ballast, the pumps form a vacuum that pull what through the sackss into the tanks, and then empty out of the tanks. I am having a problem with the sacks completely flattening once they are empty and forming a vacuum which doesnt allow air to pass into the tanks to replace the water when they start to empty. It keeps causing my pumps to flip the breakers.

Has anyone else experienced this type of problem? Any thoughts on a solution? I was thinking of adding a straw of one sort or another in the bag itself to keep it from vacuum locking...

[mdboats]

tdc_worm,

Do you have the overflow routing out the front of the bag or the back? I have the same setup in my 220 and have the over flow running out the of the bag. I had one bag vacuum so I shortned exhaust line so it would not reach the bottom of the bag. Also, I found if the overflow is right over the fill base it is less likley to vacuum.

Mark Dougherty

Below is a picture of my setup.

[tdc_worm]

My fill is located on the bottom of the sack towards the stern. The overflow is coming off of the top of the sack towards the bow. do you have any problems trapping air at the opposite end of the sack when filling?

[mdboats]

No. I was thinking the same thing, but tried the rear overflow because it looked smoother. The little air you get in there is not enough to make a difference (it burps itself out when you move) especially since it does not make a vacuum when you empty.

MD

[mdboats]

I just read my first post. Sorry for not proof reading. I have the bag overflowing out the rear not the front.

MD

[tdc_worm]

cool. my rationale was to fill from the bottom rear because it should be at the lowest spot. for emptying, i chose the top front of the sack (should be the highest point) to overflow in order to keep the sack from dumping out water inadvertently....although, i guess the through hull is the limiting factor. do you lose much water out of the overflow?

[noti_dad]

There is an old post covering this. The short story is put some PVC pipe in the bottom of your sacs. I got this from another PN member when I did the same thing last year to my 211. Fill the bottom of the sac with lengths that go completely from the front to the back of the sac (smooth the ends off so they don't rub the bag). Insert them through the hole in your bag one by one. Hook it up and go. I've got over 100 hours using mine and haven't had a problem collapsing the tanks or tripping breakers because of lack of vent/air flow when emptying.

[jonfo]

What purpose do the pvc serve? I can see they would keep the bag from contracting i guess. On my 211 i keep the ball valve overflow open so the pumps will just suck air when the bag/tank empties.

[noti_dad]

The vavle just keeps the vent from siphoning once the bag is pressurized/filled.

The pvc creates an airspace that allows the bag to empty but not collapse on itself, seal the flow of air/vent to the hard tank, create a vacum and collapse the tank.

[mdboats]

tdc_worm,

The rear bags will bleed off a little, but here again not enough to make a difference. They are still full and tight. My bow bag will not stay tight as the rear, do you have the same problem?

What setup are you running? I have a pair of 400's over the rear tanks and the intergrated bow bag for around 400. It needs an additional 300-400 in the nose so it doesn't propse (handled with people or a bag).

Later,

MD

[Ryan_E]

noti_dad - this may sound dumb, but how do you seal off the pvc pipe you put in the fat sac? or is the a piece of pvc just stuck in the sac?

[tdc_worm]

tdc_worm,

The rear bags will bleed off a little, but here again not enough to make a difference. They are still full and tight. My bow bag will not stay tight as the rear, do you have the same problem?

What setup are you running? I have a pair of 400's over the rear tanks and the intergrated bow bag for around 400. It needs an additional 300-400 in the nose so it doesn't propse (handled with people or a bag).

Later,

MD

-i am running fly high 750s in the rear lockers (probably get 5-600 lbs in the each max).
-in the belly, i am running a fly high w705 (650 lbs) that probably gets around 400 lbs of water.
-lead in the belly and the nose accounts for another 350lbs.
-i also have an integrated bow sack in the nose that i can fill if we have a large crew and i need help getting on plane. the acme 1234 pretty much has solved that problem, however

i did run my locker sacks off of both the rear upper and lower holes today and it seemed to do the trick without the bag vacuum locking...

[noti_dad]

The pvc is open at both ends. That and the space between them is what provides a passage for air to vent through. I think the trick is to make sure you put more in the sac than less. Some may not provide a passage, so I used plenty.

[jonfo]

I noticed this vacuum effect today, the stock tank doesnt empty completely due to the sack not letting any air through the breather. When i stop the empty pump i hear air rush in, the i restart it and it empties the rest of the way. I see how the PVC tubing could prevent this. I think it may help to drill a bunch of holes through the pvc as well.

[noti_dad]

Try it again and take a look at the hard tanks under the sacs. I'll bet they are collapsed. I couldn't believe the pumps had that much suction but they did. Scared the cr@p outta me when I saw the tank sucking in on itself. Just glad it didn't hurt them.

Don't thing you need the holes, but they shouldn't hurt anything.