Are full water tanks on the hard bad for the boat?

[hlev00]

We had to haul our Beneteau 423 for a couple of weeks. We had just finished filling our two water tanks. Forward is 75 gallons. Aft is 50 gallons. The 50 gallon fuel tank is about full too. Is the weight of the water significant enough that we should empty the water tanks while the boat remains on the hard?

Thanks,
Harry

[billknny]

Originally Posted by hlev00

We had to haul our Beneteau 423 for a couple of weeks. We had just finished filling our two water tanks. Forward is 75 gallons. Aft is 50 gallons. The 50 gallon fuel tank is about full too. Is the weight of the water significant enough that we should empty the water tanks while the boat remains on the hard?

Thanks,
Harry

No worries. Unless storing the boat for freezing weather of course...

[nhschneider]

If we're storing our boat for any significant length of time, we always fill the fuel tanks - we have two, 90 gallons each. The theory is that if the fuel tank is full, there's less room for condensation to form. At the same time, we usually drain our water tanks only because we think it gives less opportunity for things to grow in the water. However, as far as affecting the structure of a boat, there should be no worries if all the tanks are full.

Fair winds and calm seas.

[JPA Cate]

It's roughly the equivalent of 18 extra people aboard, weight-wise. Your boat, your choice.

We normally haul with whatever we had in fuel, but try not to have full water tanks, but for us that is only 1800 lbs.

Ann

[StuM]

Originally Posted by JPA Cate

It's roughly the equivalent of 18 extra people aboard, weight-wise. Your boat, your choice.

We normally haul with whatever we had in fuel, but try not to have full water tanks, but for us that is only 1800 lbs.

Ann

You may like to revise your calculations.
75+50 = 125 gallons.

125 US Gallons = 473Kg (the OP is in the US so I assume that's what he means, if it's imperial, its 568Kg)


That's more like 5-6 people rather than 18

[SV_Harbinger]

Will it harm the boat I would not think so but if you are going to be keeping her out of the water for a long time I would drain the water out to keep the tanks cleaner. But Harbinger doesn't spend any significant time out of the water, just long enough to do the bottom work once a year in the spring.

[Nicholson58]

Our fuel and water is 7000# combined. We never empty to haul. Camper and Nicholson58

[NYSail]

Originally Posted by hlev00

We had to haul our Beneteau 423 for a couple of weeks. We had just finished filling our two water tanks. Forward is 75 gallons. Aft is 50 gallons. The 50 gallon fuel tank is about full too. Is the weight of the water significant enough that we should empty the water tanks while the boat remains on the hard?

Thanks,
Harry

My 423 has 100 gallons up front for 150 total water.....

Greg

[Dockhead]

I think that's actually a serious question.


That model of Bene AFAIK has a fairly thin single layer hull which can bend a lot when the boat is on the hard -- causing some problems for boatyards, requiring care with props and so forth. I know someone with a similar boat who had to have his hull x-rayed after one prop came way inside the hull volume just from his walking on the bow with the boat on the hard.



I think I might empty the water tanks, myself.

[kas_1611]

Originally Posted by StuM

You may like to revise your calculations.
75+50 = 125 gallons.

125 US Gallons = 473Kg (the OP is in the US so I assume that's what he means, if it's imperial, its 568Kg)


That's more like 5-6 people rather than 18

50 GallonsUS of diesel weighs 347.15lbs
125 GallonsUS of water weighs 1045lbs

Total weight of fluid is 1392.15lbs
2.2lbs to the kilo that is 632.8kg

I tip the scales at 74kg (163 lbs) so that is 8 1/2 me's

Weight of diesel 6.9ppg
Weight of freshwater 8.36ppg

[TrentePieds]

A reputable yard is always very careful about placing slings and props where there is interior structure (such as transverse bulkheads) in the hull to vector the pressure of slings and props into the hull where it is strongest. Dunnage is also placed very carefully under the keel, for it is the keel and the dunnage that takes almost all the weight of the boat. The "jacks stands" are there only to ensure that the boat won't topple, and they actually take very little weight at all. Again, the stands with their relative small pads should not be placed willy-nilly, but where there is structure within the hull to take the pressure.

A boat's hull is essentially a monocoque structure and should not distort when hauled. However, the hull to deck joint is the "weak link in the chain", and if it isn't entirely sound (which you probably would not know), it can burst, and deflection can take place. Work Orders/contracts for hauling normally contain a waiver of liability for that reason, so the yard cannot be held responsible if the seam (or anything else) pops.

If the hauling and propping are done responsibly there should no reason to drain the water tanks, even if they are at the extreme ends of the boat which is very often the case, but since it is so very simple to do, why not just do it? It is a lot easier to drain in the fall and fill in the spring, if you are in a location where there is frost, than it is to mess with antifreeze. Antifreeze requires that you drain in the spring anyway in order to flush the tanks, so just drain the water before you haul.

TrentePieds

[sailcrazy]

We usually leave our boat every year for 4-6 months. And we haul every season, for bottom inspection+ mx, etc, and now that we're in the Caribb...its for hurricane safety as much as anything else. We always ensure our fuel tank is full(no space for condensation), and our water tanks are full. Full water tanks mean no air-exposed surface, and so less chance for "things" to grow. The other option, IMO, would be to COMPLETELY empty the water tanks and blow the lines out....but that's to hard to do! Plus, the added weight might help stability in the event of a major blow. And, after 10+ years in the Philippinnes and now 4 years in the Caribb-we've had no damage due to typhoons/hurricanes-yet. And yes, hulls can "move" some when you're out of the water-that's why you always check the realignment after the hull is back in the water for a few days, not just on the hard after you've messed with the shaft alignment. But we've never noticed enough movement to be noticeable, or to effect drawers/locker doors, or anything else.

[Locquatious]

It's a good question, water full or no. We debate it.
We had blisters in the hull which had to be planed off and recoated. Does the water in the tanks lead to blisters inside our fiberglass water tanks? Is it better to let them dry? Can anything ever dry inside an empty water tank?
Is the extra weight (we have 400 gallons full) better during hurricane season? Would it help to keep us from toppling?
Will we need water when in the yard? Do we want to pay for yard water? Do we want chlorinated water in our tanks? We invested time and expense in watermaker water. Why would we dump that to go in the yard?

[Martkimwat]

Originally Posted by JPA Cate

It's roughly the equivalent of 18 extra people aboard, weight-wise. Your boat, your choice.

We normally haul with whatever we had in fuel, but try not to have full water tanks, but for us that is only 1800 lbs.

Ann

Ann, I think your arithmetic is a bit out or you know some really tiny people! Average weight of an adult is 80 Kgs so 18 would be 1440kgs or 3174 lbs. Their water tankage combined is 125 gallons (i'm guessing they are quoting imperial not US gallons) thats 567.5 litres = 567.5 Kgs or 1251 lbs or roughly 7 adults, that's not a huge number on a large boat. you quote your tankage is only 1800 lbs, that's still more than they have. (1800 lbs =816 kgs = 816 imp. galls)

[JPA Cate]

Originally Posted by StuM

You may like to revise your calculations.
75+50 = 125 gallons.

125 US Gallons = 473Kg (the OP is in the US so I assume that's what he means, if it's imperial, its 568Kg)


That's more like 5-6 people rather than 18

He did say 175 gallons. 16 lbs per gallon (a pint's a pound, the world around), so approximately 2800 lbs, divided by 150 lbs for the people. Just approximations, but I just ran the numbers again, and my calculator says 18.66666667, so I called it 18. Figured somebody might weigh more than 150 lbs.

Ann