Empty water tank equals boat dipping at the stern?

[larrysanders]

OK I understand the law of buoyancy. However I was really surprised at how much my narrowboat dips at the back and rises at the front when all the water was emptied from my tank, 5 inches or so. It look a good hour plus to empty and it's the first time I've done it on this boat. Am I getting slightly paranoid after reading about boats sinking!!?!!

[Robbo]

Am I getting slightly paranoid after reading about boats sinking!!?!!

 

yes

Edited January 3, 2010 by Robbo

[Idunhoe]

Simple physics really - remove the best part of a ton from one end then that end will rise, the engine no longer has the weight of water to counterbalance it so that end will sit lower in the water.....simples

[larrysanders]

Simple physics really - remove the best part of a ton from one end then that end will rise, the engine no longer has the weight of water to counterbalance it so that end will sit lower in the water.....simples

 

 

Would the length of the boat also make a difference then.. the shorter the boat the bigger the rise and fall?

[DHutch]

Its not at all uncommon, although 5inchs seams a little more than i would expect at the stern. Or is that measurement at the bow?

 

 

Do you know (roughly) how big the water tank is or what the boat weighs over all or its length? All three will effect the ultimate change in trim.

[steelaway]

Would the length of the boat also make a difference then.. the shorter the boat the bigger the rise and fall?

 

 

Yes and the amount of fuel in the tank

 

Alex

[larrysanders]

Its not at all uncommon, although 5inchs seams a little more than i would expect at the stern. Or is that measurement at the bow?

 

approx 5 inches is the measurement at the bow. length is 30ft.

Edited January 3, 2010 by larrysanders

[Nickhlx]

Yes and the amount of fuel in the tank

 

Alex

 

 

and where the waste tank is sited and how full it is - ours is just in front of the engine, full width of boat ( doesn't affect angle of list as it fills ) approx 10" deep and 3 feet high, so around 16 cu ft or 98 gallons or 450 litres - I guess approx 500 kgs depending on the density of ***t !

 

Nick

[koukouvagia]

approx 5 inches is the measurement at the bow. length is 30ft.

 

That means you've got a simple way of determining how empty your water tank is. I use the same method – none of these new fangled gauges for me.

[NB Alnwick]

That means you've got a simple way of determining how empty your water tank is. I use the same method – none of these new fangled gauges for me.

 

Yes we use the same method - it usually goes like this: "how much fresh water have we got left?" the answer comes in the number of rivets showing below the full tank high water mark - i.e. "two rivets!".

[Mac of Cygnet]

Yes we use the same method - it usually goes like this: "how much fresh water have we got left?" the answer comes in the number of rivets showing below the full tank high water mark - i.e. "two rivets!".

 

[pedant]Surely that's the amount of water you've used?[/pedant]

[bottle]

Pedant............ but if you know the capacity of the tank and you know how much you have used, you then know how much is left.

aka. nb Alnwick. ..............Pedant off.

[nb Innisfree]

Yes we use the same method - it usually goes like this: "how much fresh water have we got left?" the answer comes in the number of rivets showing below the full tank high water mark - i.e. "two rivets!".

 

Do you mean washers?

[bottle]

OOoooooo!!!! that was a bit below the belt waterline.

[larrysanders]

That means you've got a simple way of determining how empty your water tank is. I use the same method – none of these new fangled gauges for me.

 

That's a great tip..! when i emptied the tank there appeared to be some rust in the last bit of water that came out. Anyone repainted the inside of thier tank?

[nb Innisfree]

That's a great tip..! when i emptied the tank there appeared to be some rust in the last bit of water that came out. Anyone repainted the inside of thier tank?

 

Every year we empty tank mop it dry and repatch where it's needed with tank blacking. Leave to dry with lid slightly open for a couple of days.

[wrigglefingers]

That's a great tip..! when i emptied the tank there appeared to be some rust in the last bit of water that came out. Anyone repainted the inside of thier tank?

 

Was Ellen's tried and tested method of assessing whether we needed more water, she could judge to within a a few litres, a technique she referred to as 'just-in-time-filling'. She perfected the technioque when I made her pay for a new water pump after she ran it dry once too often. Hell hath no fury as a mother halfway through a shower with no water in the tank and a dead water pump! She's out of luck with Cobbett though as the water tank is midships this time though.

 

Repainting water tanks is my favourite comedy job on a boat. see thread here but there's plenty of more useful advice. I'm afraid it's not possible to avoid it really but there are some reasonable ideas about what to do if if you do it once and never fancy doing it again ......

[NB Alnwick]

Do you mean washers?

 

Although there are a great many cosmetic embellishments on 'Alnwick' the rivets through the solid forged stem post are real enough but it is also welded on both sides. Subsequent 'Northwich Traders' may not have been built to quite the same specification.

[Radiomariner]

That means you've got a simple way of determining how empty your water tank is. I use the same method – none of these new fangled gauges for me.

 

 

Yes we use the same method - it usually goes like this: "how much fresh water have we got left?" the answer comes in the number of rivets showing below the full tank high water mark - i.e. "two rivets!".

 

My system similar. When the cabin roof obscures the steerers view of the next bridgehole it's time to top up the water tank¬