MacGregorSailors.com

Along the lines of what Jimmyt said, fresh water exerts about 0.43 psi per foot of depth, so if you want .4 psi at the top of the tank, you can fill the ballast tank through the vent hole through a hose extension that’s well sealed to the vent hole. Every foot of additional water in that little hose adds another .4 psi.

But the pressure increases with depth, so max pressure at the bottom of the tank is proportional to the max depth.

I’ve made simple manometers using water and clear tubing, and air gives equal pressure everywhere, so that may be a better option. Unless you have a low pressure gauge, of course, like a Magnehelic, which comes in a jillion flavors.

Don't know if this is fact, but here is a reference to a factory ballast test.

viewtopic.php?f=10&t=23929&p=293976&hil ... st#p293976

2psi would be about 4-1/2 feet of water column using a water manometer. Again, I don't know that the factory did a 2 psi test. This was posted as fact by someone else.

In the link he says that the design value is 1 psi. That’s only about 2 ft of depth, which isn’t much heel, though it’s probably typical of ‘normal’ sailing. Maybe.

I figured 7 ft of width, out to out on the ballast tank’s widest part, with the boat knocked down.

But either way, 1 psi would be applied over the entire surface, top, bottom, sides, etc., when air is used. I’d still urge caution, and use a manometer, even if home made. Which is just as good for a one-time test, and quite accurate to-boot.

Edit: If the ballast tank is 20 ft long and 3 ft wide on average, at 1 psi there will be 8640 lb of force trying to split the top from the bottom, spread out over the whole projected area of the ballast tank system. Just sayin’.

Tomfoolery wrote: ↑Sun May 03, 2020 8:58 am In the link he says that the design value is 1 psi. That’s only about 2 ft of depth, which isn’t much heel, though it’s probably typical of ‘normal’ sailing. Maybe.

I figured 7 ft of width, out to out on the ballast tank’s widest part, with the boat knocked down.

But either way, 1 psi would be applied over the entire surface, top, bottom, sides, etc., when air is used. I’d still urge caution, and use a manometer, even if home made. Which is just as good for a one-time test, and quite accurate to-boot.

Edit: If the ballast tank is 20 ft long and 3 ft wide on average, at 1 psi there will be 8640 lb of force trying to split the top from the bottom, spread out over the whole projected area of the ballast tank system. Just sayin’.

Absolutely agree. I wouldn't do any more than 12" water column, and I'd try it once at 6" water column just to see if I could avoid going to 12". I haven't done a lot of boat pressure testing, but we designed several specialty lab facilities with differential pressure based containment strategies. You would be surprised at how little pressure it takes to do damage.

One of the things my company does is pressure test building HVAC equipment. I have a rig in my garage that can flow about 1,000CFM at 10" w.c. We were once contracted to test a huge central station air handler before installation at a local hospital. The thing was 15' high, 20' wide and 40' long, and we assembled it at the rigger's yard for performance testing before delivery to the hospital. We started building the negative pressure slowly and the thing suddenly caved in along one side. I calculated the force on the section that caved in to be about 10,000 lbs. This was only a few inches of water column acting over a large surface.

$100,000 later and a whole bunch of welding and hammering, and we got the machine to pass.

Doesn't take a lot of pressure to break something. Be careful.

Unless my cel phone math is wrong ( ), 2 ft of water depth with a 7 ft wide tank is only 16.6 degrees of heel. Which is around the sweet spot for my X at least. But it can certainly ‘tilt’, as the admiral calls it, much more than that, so water pressure on the top of the tank could easily see 2 psi I would think.

I have an X, but expect that bilge is similar to that in an M. When I've found water in the bilge (caused by rainwater and/or water tank leak), I've noticed that when I sponge it up, in a short while more water appears. It seems to take forever to finally get rid of the water. When the boat is nearly level, water migrates extremely slowly in the bilge. There may be multiple low points, and a slight tipping of the boat can result in water reappearing where it has been previously sponged up.

LOL.. Thanks for all the warnings..
Ok.. maybe not put 2psi into the tank.

I will fill with water.. dye the water.. look for leaks.
Would filling it OUT of the water put too much stress on the hull?


Thanks
AD

Chinook..

I was initially thinking some hatch etc was leaking.. heck it was only a small amount of water..
But then again.. mind got going.. what if the leak is below the water line.. and the drain valve is open.. would the boat be under water..
(you know.. I am that personality Type)

I would sop up the water.. 1hr later.. its all back!
No rain.. on the trailer..
Must be from the ballast.
I know it must be a mfg problem, as the boat was in very good shape.
Nothing was mounted to the floor..
so I started poking around until I saw that air bubble in the glass..

Quick patch with JB Weld WaterWeld.. now going to let the glass dry out.. and then resin over it.. and lay some cloth.
(now I can sleep)

I guess things like this are not uncommon wht a Mac of any model.

AD

adudinsk wrote: ↑Sun May 03, 2020 2:24 pm LOL.. Thanks for all the warnings..
Ok.. maybe not put 2psi into the tank.

I will fill with water.. dye the water.. look for leaks.
Would filling it OUT of the water put too much stress on the hull?


Thanks
AD

The approved method for draining the ballast is to put it on the trailer and pull it up the ramp while its draining. So, it should hold enough water for you to have a look. I wouldn't leave it long, or tow it full, but you should be able to put a bit of water in it without damage. Remember, you found the leak you fixed with a drained tank...

I would probably put it in the water, fill the ballast tank, motor and/or sail a while, and then check the bilge for water. If you have water in the bilge, put it back on the trailer and start dreaming up ways to test/locate leaks.

If there are no leaks in the hull, and you are only leaking ballast water into the bilge, the boat won't sink - if the ballast valve is closed. You will have water where you didn't want it though.

Thanks for the heads up we are dropping our boats on the 23rd of May so maybe I'll get everything ready to go drop it park it and camp out in it to see if any water is coming in..

Thanks for all the info..

As

Sorry that's a AD ...not AS...

adudinsk wrote: ↑Sun May 03, 2020 2:24 pmWould filling it OUT of the water put too much stress on the hull?

I've pulled mine out more than once with a full ballast tank. When I've forgotten to open the valve and vent. Not often, but more than once.

It's an extra 1300-1400 lb, rolling slowly. Not something I'd lose any sleep over, as an empty boat weighing 3000 lb or so banging down the road on a trailer at highway speeds will also exert great force on the bunks, and we do that all the time without a second thought.

Jimmyt wrote: ↑Mon May 04, 2020 6:17 amThe approved method for draining the ballast is to put it on the trailer and pull it up the ramp while its draining.

That's what I do - open the valve and vent, then drive it onto the trailer. As it's winched up the trailer, even a little, the bow raises and the water starts to flow out the back. By the time I'm done monkeying with it and I'll pulling it up the ramp, at least half the water is out, if not more. Usually just a minor stream coming out by the time I walk around back to check on it.

That's if I don't drain it while motoring at speed, that is. I only do that when the ramp is steep and I need the boat high to start with so the goal posts aren't completely submerged. And mine are much longer than the originals. But my local ramp is the steepest I've ever seen, so it helps a lot to drain the ballast before trying to load it.

Just a follow up...
Boat is dry as a bone.
Hatch has some "crunchy bits" around the screws.. used an epoxy wood rot fixer.. worked great, added an aluminm plate for more strength on the underside.

Adjusted motor idle, but get a bit of coughing .. motor runs fine.. then one (yes one) sputter.. then runs..
Looks like the fuel lines should be 5/16" and some are 3/8" and they look a bit tired.. ordered all new lines/bulb/fittings/etc. Changed fuel filter long ago.. will clean insides of fuel pump.. I think this is just a minor fuel issue (maybe sucking some air) not an engine prob. at all.
(having fun tinkering for sure!)

Need to test the charging system.. maybe replace the rectifier? Getting a Low Battery Alarm on the Depth Sounder (have to check if settings are off..)
NO biggie.. standard wear/tear for a 2005 motor.

One battery is a bit weak.. but usable.. may change sometime this summer..

But overall having fun with the projects, and happy with the boat. .. get lots of the members at our club gawking at the boat. All love the interior space and layout. Many surprised how large it is for a 26' boat...

Soon will start on the A/C mod for the hatch ... (happy wife.. happy life..) And will post some photos..etc.

AD

I,d would say it was totally impossible for even a slightly filled ballast tank to freeze & cause a crack because as long as the water has somewhere to expand as it freezes it just travels the easiest route
I had water coming in at the same location only when it rained & my dodger was removed I was able to trace it by having someone with a hose running water over the area that was under the dodger & then water started pouring in thru the plugs in the liner for the sliding hatch it would run along the liner joint there back to where the winch was then some how found it,s way down into that same lactation u mentioned so I figured the bolts holding the plastic strip that retains the sliding hatch were leaking so removed the plastic strip so as to reseal said bolts & figured that this was an excellent time to also install velcro tape onto where the sliding hatch runs on the gel coat so removed the sliding hatch & low & behold on the port side was about 4 holes in the gel coat under where the hatch slides just forward of the halfway mark towards the bow so only way u could see them was by removing the hatch all the bolts looked fine as for signs of leakage , fixed the holes all was good , so u might want to check that area out as I did

J