OTW Ballast tank sensors and tank size

[Thorbrandr]

My thought had been not to bypass the sensor, just shift it, and maybe add another to be more tolerant of the down angle without overflowing into the front compartment.

I did contact Bob at OTW. He called and we had a great discussion.

Bob thinks the boat is too light, requiring too much ballast fill. His simple recommendation: a touch more ballast. Simply provide enough extra space in the tank that this is not an issue. This should not disturb the surface trim by much. It does mean that it will be possible to fill the tank to a significant negative buoyancy, so I will need to watch that. So far the safety blow on the tank has always worked when it looses signal, and the new battery lasts longer than I do when running it.

Chris

[Schmitty1944]

I knew my by-pass idea wouldn't work if it has the hole between ballast and dry area, I just didn't realize that they pretty much always have that hole already drilled. Moving the filled water probe either higher up or to the opposite end of the ballast tank is likely to cause at least some flooding of the dry area.

A while ago there was some talk and research about a fine mesh membrane that would let air through that hole but not water, I'm not sure what became of that idea but it sure would be helpful in your case.

I'm probably not the only one that really doesn't like the idea of a hole directly between a wet area (ballast tank) and dry area (pressure hull). I know it works well enough within the limitations that others pointed out. It just seems like it's asking for trouble with the only thing between success and disaster is a electronic circuit and probe to tell the pump when to stop. A mechanical float valve that would stop water from going through that hole would be a big improvement, or better yet a dedicated compartment to contain the displaced air from the ballast tank as it fills, either section off part of the pressure hull or it could be its own separate compartment outside of the wtc as long as it was below the surfaced waterline. A vent line from the top of the ballast tank to the bottom of this air pressure vessel would be the only connection to anything.

Bob's (O.T.W.) solution will certainly work for you, at the expense of not having as much surfaced free board and of course you can always add some foam above the waterline to prevent it from going too negative in submerged trim.

Jason

[goshawk823]

My thought had been not to bypass the sensor, just shift it, and maybe add another to be more tolerant of the down angle without overflowing into the front compartment.

I did contact Bob at OTW. He called and we had a great discussion.

Bob thinks the boat is too light, requiring too much ballast fill. His simple recommendation: a touch more ballast. Simply provide enough extra space in the tank that this is not an issue. This should not disturb the surface trim by much. It does mean that it will be possible to fill the tank to a significant negative buoyancy, so I will need to watch that. So far the safety blow on the tank has always worked when it looses signal, and the new battery lasts longer than I do when running it.

Chris

I'm glad you called him. He will always help with questions related to his products.

[Thorbrandr]

...

Bob's (O.T.W.) solution will certainly work for you, at the expense of not having as much surfaced free board and of course you can always add some foam above the waterline to prevent it from going too negative in submerged trim.

Jason

I am running out of room for loam above the waterline! UPS scrambled the ballast, so it has taken a bit to get it sorted out. Overall I am getting very good performance now after adjusting for a tendency to drop the stern while submerged. I can deal with a little loss of freeboard on the surface - it actually runs pretty close to photos of the originals.

Chris

[Thorbrandr]

I'm glad you called him. He will always help with questions related to his products.

Actually, he called me! I had my contact info in the email I sent. Since he went paid me the courtesy to call, I figure I should trying his suggestion in my test tank this weekend and letting him know how it worked.

Chris