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forward water tank?

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slim
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USA
113 Posts

Initially Posted - 03/10/2017 : 10:35:32

Hi everyone

I am thinking of putting in a bladder type water tank in the bow of my boat under the v berth with about a 30 gal capacity. Wondering how this will effect my boat's helm and if anyone has experience in doing this and the results they had sailing their boat after word. I would remove the starboard water tank and use that area for storage. I thought this might balance out the outboard motor gas and human weight in the aft end just don't know how well she would handle?

Thanks Slim

1978 - C25 - standard rig - Fixed keel #1040

islander
Master Marine Consultant

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3992 Posts

Response Posted - 03/10/2017 : 13:46:10

30 gal. Is about 250 lbs. You could test it with some sand bags or a large friend up in the berth before committing to buying the parts and plumbing. Maybe someone has done this and can give better advice.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Steve Milby
Past Commodore

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5851 Posts

Response Posted - 03/10/2017 : 15:39:51

The empty bladder obviously won't have any effect on the orientation of the boat. If it's full, or nearly so, it will slow the boat speed under sail, and under power it will likely cause the prop to lift out of the water much more frequently, especially when motoring to windward in a chop. If you encounter foul weather and are unable to motor to windward effectively, it could be dangerous, because you might not be able to get the boat into a place of shelter.

Many people only fill their fresh water tanks when they're cruising. I live aboard my C&C 35 all summer and usually don't fill the fresh water tanks at all. Most people don't like the taste of water from an RV tank, so they bring bottled water to drink and cook. We had no showers where I used to sail, so we took "duck baths," or jumped in the lake for a swim, or swabbed with baby wipes, or rinsed off with a hose at the dock, or found some way to feel refreshed. We were only there for Friday and Saturday night, so we only needed short term solutions. When cruising, it's always good to stay on the hook for a night or two, and then in a marina with restrooms and showers. You'll want to come in about that often for ice, in any case.

My suggestion is that you think of ways that you can meet your needs either without a fresh water tank, or with a much smaller one.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

slim
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113 Posts

Response Posted - 03/10/2017 : 19:08:40

Hi steve

I agree with what you are saying and also think the less weight a person has on his boat the better. I cruised and lived on a 25 for three years and know the value of fresh water. When i was away from any docks for extended periods of time 1 or 2 weeks i would always be thinking about water and how much i had left. I would not fill the tank except at those times i plan on being away for extended periods. I never hear anyone say much about helm changing or boat handling condition in general when someone is up at the bow making sail changes or doing other work. So i am thinking that it is not going to be a big deal but i still would like to hear from someone that has done this with their boat and the results even there was no changes at all.

Thanks Slim

1978 - C25 - standard rig - Fixed keel #1040

Steve Milby
Past Commodore

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5851 Posts

Response Posted - 03/10/2017 : 19:37:57

In moderate to stronger winds, a sailboat's speed is reduced when there's more weight forward. The reason is because, when the bow is down, the transom is lifted out of the water a bit. That reduces the boat's effective waterline length, and waterline length limits a boat's theoretical hull speed.

However, in very light air, putting weight forward and tilting the bow down reduces the boat's effective waterline length, but in this case it increases boat speed.

The reason why reducing waterline length has an opposite effect in light air from it's effect in stronger winds is that the limiting effect of waterline length on hull speed only matters when the boat is at or very near hull speed. In light air, the boat is sailing at considerably less than hull speed, so shortening the waterline length doesn't reduce the boat's speed capability. On the contrary, shortening the waterline length reduces the boat's wetted surface. When there is more surface area of the boat that is immersed in the water, there will be more drag created by the flow of water over that surface, and drag slows the boat. In moderate or stronger winds, the power generated by the sails can help overcome that drag. In lighter wind, that drag has a much more pronounced effect in rubbing off boat speed. Thus, tilting the bow down in light air reduces drag, and increases boat speed.

When you tilt the bow down, the effect on the sailplan is the same as if you tipped the mast forward. Tipping the mast forward reduces weather helm. If you tilt it too far forward, you can actually create lee helm, which is generally regarded as dangerous and will likewise reduce boat speed.

That creates a dilemma for you. Since the condition causing the forward tilt is only temporary, i.e. it will only last as long as the tank is full, should you re-tune the rig each time you fill or empty the water tank? It sounds a little preposterous, but tilting the bow down that much will have a considerable effect on the boat's performance.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 03/10/2017 19:53:08

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 03/10/2017 : 21:10:48

quote:
Originally posted by islander

30 gal. Is about 250 lbs. You could test it with some sand bags or a large friend up in the berth before committing to buying the parts and plumbing. Maybe someone has done this and can give better advice.

I think this test is a great idea. You might discover some other unforeseen issue. As an example (that may or may not fit your boat), depending on your outboard shaft length and outboard bracket, enough weight forward can cause outboard prop ventilation.

Seth
"Outlier" 1987 Catalina 25 SR/SK/Traditional Interior #5541
"Zoo" 1977 Morgan Out Island 30
"Nomad" 1980 Prindle 16
"Lost" 1988 Catalina Capri 14.2 (sold - yay!)
"Marine Tex 1" Unknown Origin POS 8' Fiberglass Dinghy
https://whichsailboat.com/2014/07/27/catalina-25-review/

bigelowp
Master Marine Consultant

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USA
1736 Posts

Response Posted - 03/11/2017 : 07:12:28

I would be considering replacing the existing water tank with a slightly large bladder type and then use portable water containers that you can locate to balance the boat and lash down if/when you need them. Should be much simpler, offer more flexibility and get the job done when you are cruising.

Peter Bigelow
C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

slim
Navigator

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USA
113 Posts

Response Posted - 03/11/2017 : 07:17:39

yep that is about it then! I will test with sandbags first as i was not going to do this project for another few months anyway. Another great idea from the forum members and wise counsel it is indeed. Many thanks again to all

Slim

1978 - C25 - standard rig - Fixed keel #1040

Voyager
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5231 Posts

Response Posted - 03/11/2017 : 07:28:20

I find when sailing on a close reach to windward with strong winds and heavy seas the bow crashes down from a crest into a trough and it he boat almost comes to a stop. If you had 250 more pounds in the bow, this effect would be amplified as when a person goes forward at that time. This set of conditions would be a worst case. So, I'd suggest it's great to have capacity for 30 gallons if you ever needed it (showering, wash down or weeks offshore), but as a rule keep no more than a few gallons handy. And bottles of water for drinking and cooking.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 03/11/2017 : 08:05:03

Slim, Since we are not engineers we can only guess as to how this would effect the boat. Adding sand bags will cost next to nothing to find out if it's doable. It might be. Nothing ventured, Nothing gained IMHO.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Akenumber
Navigator

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USA
247 Posts

Response Posted - 03/12/2017 : 12:31:02

I have a 15 gallon water tank in our bow. Freed up a lot of space in the starboard settee. Super awesome mod. I did notice that when crew go forward it is a little more likely to lift the prop out of the water, but totally worth it. And in some situations, like a heavy cockpit it actually helps out. With two people it still seems to cut threw the chop better. Also if I am not mistaken C27 s come with it in the bow. I guess just don't go too extreme.

Ken
San Diego
84 C25 SR/FK 4116
The KRAKEN

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 03/12/2017 : 12:44:18

30 gallons would be an awful lot of weight to put forward. 15 gallons would be more do-able. If 30 gallons is needed, 15 forward and another 15 near the centerline aft would balance the boat much better.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

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