Overfilling the Ballast Tank?

[PeteC]

I have been using a suggestion posted several months ago that recommended motoring slowly in reverse while filling the ballast tank. The tank fills quicker and you can fill it fuller; up to the bottom of the vent hole. In theory the full tank has no water sloshing and "stiffens" up the boat while sailing.

After reading <http://macgregorsailors.com/phpBB/viewtopic.php?t=2349> I was wondering if this extra water is situated above the waterline, which would perhaps decrease the stability of the boat.

I haven't sailed enough yet to notice any problem.

Does anyone else do this 'overfill' trick?

[ESPERANZA]

I was going to try this last summer but I think it only applies to the Mac with the vent in the bow. Mine is under the step...
Dik...

[Catigale]

I was wondering if this extra water is situated above the waterline, which would perhaps decrease the stability of the boat.

I dont think it is the waterline that is important, it would be the Center of Gravity. IF the additional water is below the existing CG, it lowers it, if its above the CG it raises it. Of course, if the boat heels over and puts the 'added' water below the CG, it now acts as additional righting moment, and works in your favour again.

That being said, I dont know where the CG is on an or but Im sure one of our group can expound on this ....

My guess is the effects here are not going to be measurable, and will be swamped out by other considerations like how much stuff is on board and and where it is located etc. Based on my I dont think this is more than a few gallons of water extra I can get into the tank, so 20-30 pounds extra at most. Could be wrong here. BLue hulls ballast faster....

[richandlori]

I'm not sure why you would need to motor in reverse to fill the tank faster. The times I have put the boat in via launch ramp, I go in with valve and vent open, and by the time I am ready to leave the dock, the tank is full with water lapping in and out of the vent hole. How long does it really take? Now that I have my boat at a mast-up storage facility and they crane it in and out ot the water, I do the same thing of leaving the vent and valve open and by the time I am ready to leave the dock....tank is full. I'm not sure if I could get any more water in if I tried. It would be a design flaw on Mac's part to require motoring backwards to properly fill the ballast tank, and since one of the most dangerous issues of a water ballast boat is not being completely full or empty, I think that the Mac is designed to reach the full ballast point without any extra measures.

Just my 1.75cents worth...


Rich

[tidalwave]

I am planning on running an 'airhose' from my foreward ballast air vent
up to a thru-hull fitting exiting my anchor locker. I noted that
several owners have done this before.

Are there any negatives about running an air line?

My line will use a brass nipple fitting at the ballast vent hole...a pressure-type hose with hose clamps.

[Andy26M]

On my 26M (vent hole is up under the V-Berth) my ballast tank fills right up to within 2 inches of the vent hole without motoring backwards. If I am alone on the boat and go forward, my weight in the bow will in fact overfill the ballast by about a quarter inch (more if I have my fresh water tank in the V full).

If I was to motor backwards, I think I could get water up over the cofferdam around the vent and wet the stuff stored under the seats.

- AndyS

[Sloop John B]

Pete might have something here. Suppose his mate is going to drop him off and then take off with the rig. He wouldnt have to tie up to get the rig off the ramp or have to wait to have his mate trot down to the pier. Fire the motor up and start roaring around the marina backwards. If its a little tight, its best to have a rudder or two down. Course, you dont want to ground a rudder going backwards, its bad enough when it happens going forward. Its more efficient to try to back toward where you are heading, that is, the entrance. Bring one of the kids along to sit by the vent pipe with his finger down the hole. Have him trained to holler when the tank is full. Then slam the valve shut, tell the kid to cork the vent. Swing the boat around 180, cleat the sheets, and check your stopwatch. Ha! An extra two minutes of afternoon glee.

Otherwise, doesnt the older hump vent under the companionway hatch fill to the top?

[Chip Hindes]

Moe is right about the dome part at least on my late 26X with forward vent. The last three to four inches beow the vent is equal to only a gallon or so of water; it's not much worth the effort to superfill the tank under normal conditons.

When the boat is sitting at the dock or launch ramp in dead calm, filling the ballast is not much of a problem. When the wind and chop are up and the boat's being tossed around especially side to side, it's quite difficult to get a complete fill. Motoring forward even just enough to maintain steerageway can also prevent attaining a complete fill. On some occasions I have found motoring in reverse allows you to keep the boat properly oriented while providing some assistance to the fill effort. Depending on how much you appreciate your helper, you might tell him or her to hold their hand over the vent hole as a splash guard and not peer down into it; the water can erupt out of there like old faithful. Or you might not mention it.