installing a bilge in ballast tank

[walt]

You would mostly use that helium to answer all those questions about why there is water coming from the boat in a "helium voice".

Is this how pressure works?

Looking at the 26S brochure, it looks like the tank has an area (top view) of about 3 foot by 19 foot or 8200 square inches.

In order to start having water come out the bottom of the boat, the boat must effectively be lifted but it’s only the boat that is lifted, not the water. Weight of the boat without water might be 2400 pounds or so. So the pounds per square inch to lift the boat

2400 pounds = 8200 square inches * PSI

PSI = .29 pounds per square inch.

This is actually PSI over ambient air pressure which is about 15 pounds/inch**2.

So the boat begins to lift at .29 psi, the more pressure you apply after that just increases how fast the boat drains. The maximum the pump can put out is 1 psi but if the valve is open, the max pressure isn’t reached so the pressure is probably somewhere between ..29 to 1 psi. When the boat is blowing bubbles out the bottom, the pressure in the tank is probably right at .29 psi??

I don’t know if this is right.. but it matches what I think I observed..

 

[vizwhiz]

Walt...you have the idea, but it isnt really related to the area, it is related only to the depth of the water (since we are always assuming something is open to atmosphere here).
2.31 feet of water height equals 1psi...regardless of shape, size, etc. The pressure the pump will exert is only going to equal the depth of water it has to displace, so it will start out very low and increase as the water has to be pushed deeper relative to the water below the boat. Fortunately, the boat also rises a little due to the lighter weight, and the pressure will end up somewhere in the neighborhood of what you suggest (0.3 x 2.31 = .7 ft) or six to eight inches of height...about the depth of the ballast tank, so it checks out nicely.

Now brought up also was the rate at which the ballast tank empties... Additional pressure would increase the rate at which the water flows out thru the ballast valve, but since we are talking in fractional pressures here, the difference between 1/2 psi and 1 psi will not make a lot of difference to the speed at which it empties. Whether the little blower can or will reach the full 1psi has to do with how much air it can move into the space compared to how fast the water leaves under the pressure it has reached...just a bit of a race. A bigger blower would back up and reach the full pressure (being essentially blocked by the water), but these may be small enough that the balance point between air going in and water going out occurs somewhere below 1psi.
If you want to experiment with that just for the fun of it, put the blower on the full ballast tank and slowly open the ballast valve while listening to the blower...barely cracked open will have the higher pitch associated with higher pressure and lower air movement (less water able to leave) and as you open the valve, the pitch should drop as more air can enter and the pressure drops accordingly. There will be some balance point between the blocked-in blower sound and the sound the blower makes in open air (detached with no back pressure on it).

 

[Chris & Lenore]

Chris I like the idea but have a couple questions. Is the 3/8 inch line not restrictive to the air flow of the pump. I can see maybe pumping air through a 3/8th inch opening and into the tank, but I'd think that a 3/8 inch line even 4-5 feet long might be restrictive to the air flow volume wise. I guess if this is proven then I'm obviously wrong. I would keep the ballast valve as even if it leaks just a bit it keeps all of the water in the tank so that it is ballast and not connected to the actual lake water. We probably don't heel enough, but I've seen some boats heeled to the point that water might be able drop on the high side of the ballast tank. Maybe if no air can enter that might not be the case?? I'd still keep the ballast valve functional though. Thanks for the idea and I might think seriously about doing the mod even though we have never pumped out the ballast with air. We are set up to do it though with the proper fittings and carry the air pump as we use it on the dinghy if needed. We grounded once in Florida where raising the boat like Walt did might of helped. We were able to get off with the outboard after a couple minutes though, Sum ============================ Our Endeavour 37 Our MacGregor 26-S Pages Our Trips to Utah, Idaho, Canada, Florida Mac-Venture Links

Hi Sumner,

I checked the line I used and it was 1/2 inside diameter (not sure why I was thinking. 3/8). I tried emptying the ballast with and without 10 feet of line and there was no difference in how long it took.

On Teliki I routed the air line up one side, across to the other side (via the space above the galley and liner channels) and down the other side. No change of heeling too much.

You could still leave the ballast valve. I only removed it because the air leakage around the shaft and top makes it take twice as long to empty the tank. I even make a block of wood to keep downward pressure on the top (when the valve was open) but it still leaked air when blowing the tank.

Chris

 

[Sumner]

Hi Sumner,

I checked the line I used and it was 1/2 inside diameter (not sure why I was thinking. 3/8). I tried emptying the ballast with and without 10 feet of line and there was no difference in how long it took.

On Teliki I routed the air line up one side, across to the other side (via the space above the galley and liner channels) and down the other side. No change of heeling too much.

You could still leave the ballast valve. I only removed it because the air leakage around the shaft and top makes it take twice as long to empty the tank. I even make a block of wood to keep downward pressure on the top (when the valve was open) but it still leaked air when blowing the tank.

Chris

Thanks, I think I'll try that setup. I wondered what people were doing about the leakage at the top of the ballast valve rod. I'll look into a possible fix for that area as I want to keep the ballast valve,

Sum

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[sunman]

did anyone just catch what Sum said?
this is the answer to the over 1 PSI Q: and damage to the tank!
Sum, U have a Lakester I assume from looking at ur pics, normally apirated, or other?
if other then U got a "Pop off valve " so why dont we look at the ballast shaft seal area as our "Pop pff Valve"?
whats the worst that could happen if we go above 1psi w/a tank thats not 100% air tight? get some +psi leaking around the shaft seal?
this looks like trying to pump up a flat tire w/a hole in it...just saying
Im still thinking about a 405FC pump...drop it N2 in the ballast airvent, pump out the water into the cockpit area and let it drain out the back
the Wake Board gang use this method to fill and empty the ballast tanks on thier
ski boats...hop over to"watermakers.com" and have a look!...again, just saying

 

[walt]

2.31 feet of water height equals 1psi...regardless of shape, size, etc. The pressure the pump will exert is only going to equal the depth of water it has to displace, so it will start out very low and increase as the water has to be pushed deeper relative to the water below the boat. Fortunately, the boat also rises a little due to the lighter weight, and the pressure will end up somewhere in the neighborhood of what you suggest (0.3 x 2.31 = .7 ft) or six to eight inches of height...about the depth of the ballast tank, so it checks out nicely.

Vizwhiz, I believe you are correct with the above. Good job figuring that out... Even if the depth of the ballast tank were one foot, that would still put the maximum pressure in the tank at about 0.43 psi (1/2.31 = .43)

Sumner, I had the same concern about air leaking past the valve but simply pulling it up to "sort of" compress the top seal is all I do and it works fine. I also would heed the warning label near the tank to never operate the boat without the valve tightly closed (and of course with water in the tank).

You can see the shape of the ballast tank limits how far water can move side to side even with a partially filled tank - which is a good thing.

The pictures below show how much sloshing un-contained water can de-stabilize something floating. The second picture shows a coin in a can floating. There is no water in the can and the coin is placed over to the side as far as it will go.

In the third picture, the shot glass in the second picture was filled with water and dumped into the can with the coin. You can see how much the uncontained water damaged the stability.

If you were to sail heeled on a very long reach, a leaky valve (or no valve) would result in some loss of water from the tank. A new seal for the bottom of my tank is on the list of things to get done (one of these days...) since I know mine leaks a little.

 

[Sumner]

....If you were to sail heeled on a very long reach, a leaky valve (or no valve) would result in some loss of water from the tank...

Good demo and loosing that water from the high side is exactly the side you don't want to loose it from as that is the ballast that is helping the most. We put a new seal in our valve,

Sum

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[walt]

Sumner, can you change the gasket with the boat on the trailer? Looks like it should be fairly easy to drop the valve out the bottom. I think people order that gasket (set?) from the dealer in Seatle (BY?)..

 

[Sumner]

Sumner, can you change the gasket with the boat on the trailer? Looks like it should be fairly easy to drop the valve out the bottom. I think people order that gasket (set?) from the dealer in Seatle (BY?)..

Yes got the parts from BWY. I can't remember if I did it on the trailer when it was a single axle or off the trailer or partially off. Sorry. I went and looked and I could do it now with the 2 axles, but not sure about the single axle maybe being in the way,

Sum

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Our Endeavour 37

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Our Trips to Utah, Idaho, Canada, Florida

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[finding41]

"4 cyl with 250hp? -that must have a blower... doubt you get much boost on the ramp." MrBill.
Oh yea it has! It also has traction control. That's the secret. Amazing in the snow too! I'm planning to do a stage 3 tune to it this winter and get up to around 290hp. Probably still won't spin on the ramp after that.
I hadn't thought of the advantage of being able to float off a sand bar or the such... Good idea.
I find the boat really tender when I first get it in the water and there isn't any ballast.

 

[willsnow]

Yes got the parts from BWY. I can't remember if I did it on the trailer when it was a single axle or off the trailer or partially off. Sorry. I went and looked and I could do it now with the 2 axles, but not sure about the single axle maybe being in the way,

Sum

============================

Our Endeavour 37

Our MacGregor 26-S Pages

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

I replaced my whole valve assembly while on the stock trailer. Its easy, just takes 2 people

 

[sunman]

I replaced my whole valve assembly while on the stock trailer. Its easy, just takes 2 people

get some safety wire, fish it through the valves shaft/seal holes< look through the vent hole will help.... rap it around the minor pitch of the threads on the valve threaded shaft, pull it up through the holes, a few trys and U'll index the locator pin too!

I just finished making my remote controls of the J8hp, I'm re-sealing the motor too, new seals gaskets water pump, gonna repaint the motor and the new shift/throttle control quadrant, putting up a 18X36 building for Berea, I hope I have time to install the bilge in the ballast tank or I'll use the air-pump method for awhile....
I have a 5day Ice-chest where the dinkie sink use to be, what a waste of space,
It has a fold up counter top to hide the chest, I installed Blue insulation foam board where I could, works pretty darn good

I'm gonna cut a sm.hole under the sub-floor I made to position the Ice-chest, mount the bilge next to the Dagger-board trunk, install a 1/2 in wiide x 1/8th S.S. plate w/ 5/16-18 S.S. studs in the ballast w/the studs coming through the floor and install a S/S cover-plate over that w/a gasket...plumb the ballast-water to the sinks exit pipe on the hull wall and a gland nut for the elect wire...use a bilge w/a float switch,... turn it on and it should turn off automaticly when the ballast is empty,