water tank installation

[megalops]

My boat has two issues (well, that is not true exactly, but let's just say two issues that can be covered in the scope of this post). First it has a very moderate list to stb. Not enough to be any huge thing, but enough to bug me. Second, as we spend long periods of time on the hook in the Bahamas, I would like to increase my water capacity.

So, I have decided to kill both birds by installing a 52 gallon water bladder in an unused locker under the port side deck. What I am debating on is the deck fill. I can either install an additional fill plate directly above the bladder or I MAY be able to put a T in the fill line that serves an already existing water bladder under the aft bunk.

The T has the advantage of not having to cut a big hole in the deck and all that that entails.

The aft tank sits below the level of the new tank, but the fill is well above the level of the new tank. There would be a run of about 12 feet from the aft deck fill to the new tank.

Do you guys see any reason why a T in the aft fill line would not work?

Thanks!

[s/v Faith]

It is helpful to have water supplies segregated. When taking on water, I like to be able to have 'good' and 'best' in separate tanks if I can.

In the Bahamas, the RO water I took on was excellent.. we drank it without even running it through the Brita filter.

There were times we took on water that turned out to be usable for cleaning, but I would not have wanted to have to drink it.

If you had only a single fill, you would have some mixture of the 'good' and the 'not so good' at each fill....

(plus, it would be too easy to just use what you have). :)

[mitiempo]

You say "under the side deck". 52 gallons (close to 500 lbs) high up is a mistake I think. Low down is the only good place for a water tank.
A separate fill is a better choice to segregate the supply. If one leaks you will still have the other.

[Rachel]

You say "under the side deck". 52 gallons (close to 500 lbs) high up is a mistake I think. Low down is the only good place for a water tank.

Is this always the case for a powerboat though? I don't know what type of powerboat hull megalops has, and I am below amateur when it comes to powerboat stability, but I remember reading in the Albin 25 designer notes, that they recommended against adding ballast down low, instead saying that (if one insisted on adding any) that it be outboard and just under the decks. I'm interested in learning more about this, so don't take my words as gospel at all. (And maybe bladder tanks would increase free surface effect, since they are not baffled? Or does that not happen because the tanks "vacuum" down to surround the water and so it's like they were baffled?)

The section I was remembering reading is here (but note that it's a 1.7mb download), on pages 5-6.

(And they do recommend provisions etc. as good things down low.... so....)

http://www.albin25.dk/71-72.pdf

Maybe powerboat stability discussion is not appropriate here though, so if not... never mind! I just wonder if "low down is the only good place" applies to all powerboats.

Rachel

[megalops]

Interesting discussion as far as ballast goes, but my line of thinking is that I am trying to use a realitivly small amount of weight to correct an existing issue, not to stabilize the boat necessarily. In sailing terms I think of it more as filling a water ballast tank to reduce heeling. Aren't those tanks always outboard?

I have a 1973 36' gulfstar trawler, it is basically a cut down hull from a 42' sailboat. It is round chine, ballasted and has a wide, but not real deep (maybe 1.5') keel. It is a slow displacment hull (8 knots) that will roll peanut butter out of the jar in a beam sea.

As far as putting the ballast high, the side decks are actually in the middle of the boat when you consider the house and flybridge.

I had my wife and 12 year old son, who weigh about 200 lbs between them, stand right above where I am going to place the tank and it had no noticeable effect on the list. If the tank is full (I could always empty some out if needed) it should weigh 400 lbs. I don't think this is really going to be a big deal, I'd like to lower the port side maybe 2 to 3 inches.

[mitiempo]

True, weight higher up will increase the roll period but at a loss of stability. If you put 500 lbs 2 feet above the waterline as in this case (it may be higher) you have a vertical moment of 1000 lbs (500 x 2).
To maintain the vertical center of gravity you need 1000 lbs 1 foot below the waterline or 500 lbs 2 feet below the waterline. The Gulfstar does roll because it is basically a sailboat without a rig. A rig will increase the roll period of a boat. Any sailboat that loses its rig becomes quite uncomfortable as a result. By putting 500 lbs of water just under deck level the roll period is increased, making the boat slower to roll back the other way. Taken to extremes it doesn't come back. Calm water would hold no issues but if the waves are up it could make a difference. Stability is an important issue whether powerboat or sailboat. And in many ways the Gulfstar is a sailboat minus the rig. I would try to place the bladder low but outboard if possible. The other issue not mentioned is the strength of the desired location - 500 lbs places a lot of stress on whatever it is sitting on. I have never seen tanks of that size located that high up in either a powerboat or sailboat. Around here we have had several cases of fishboats capsizing (70 foot boats) in rough weather while leaving their nets on deck without ice for ballast as they dash out for a short opening. It is not any different than water tanks high up.

[Rachel]

Thanks for the discussion, mitiempo. And to megalops for telling more about your powerboat. I didn't realize it was essentially a rig-less sailboat.

[megalops]

Here is my boat. I realize y'all are sailors and this is a stinkpot, but try to keep your negative comments to a minimum...we love her anyway. :-)

The floor in the locker is very strong, it is the same as the salon floor. In the main salon the basically just built a small fore and aft running bulkhead under the side decks at about knee level. In order to access this area you have to crawl under a flip up settee, then go through a small plexi slider. Right now I just throw spare hoses and wire in there, stuff that really should be at home in my shop. There is about 5 feet forward of the sliding doors that I am going to use to mount the bladder. Also, I'm not positive that I will be able to get 52 gallons in it, as the bladder will fill the space and no more.

Sounds like the tank may actually have some positive effect on the roll, that would be nice but my expectations are low in that regard. I really just want it to level the boat and give us more water capacity. Mitiempo is correct, the tank will be about 2 feet above the water line.

the good thing is that if it doesn't work, i can drain some or all of the water out. A waste of time, money and a hole to repair, but not a disaster.

[Hirilondë]

In sailing terms I think of it more as filling a water ballast tank to reduce heeling. Aren't those tanks always outboard?.

Well, first off, you don't have any heeling forces (well, minimal), so it doesn't apply. And no weight, is going to do much if anything to resist rolling. Even down low it only helps much at the extremes of a roll, not so much until then. For roll you could rig birds like fishing boats use, but that really doesn't seem to be the point of this discussion. Second, water ballast tanks are easy and quick to empty when the boat tacks or gybes, they are not full until the water is consumed.

If water tanks can not be added low and such as to help correct your list, then maybe stowing gear differently? Or add lead ballast secured in the bilge? Or move some of the systems components (if this is even possible or practical)?

[megalops]

Rigging birds is just not practical on a boat like mine. The cost of a rig that could handle them would be really high, especially when you consider that the cabin sides and possibly the deck would need reinforcement to handle the stresses placed on them by big chain plates and a deck stepped (?) mast.

The stabilizing sail we have is on a pretty chunky mast (probably a cut down mast from a GS 42 sailboat), but the rigging....not so much. It is a great place to mount the radome (which I have done since this pic was taken), anchor light and antennas, but not too good for much else. The sail has no noticeable effect on roll even with the wind right on the beam.

Plus, birds are really heavy, and you have to have a secure way to stow them on deck when they are not in use.

As I said, I don't really have any expectations that this will help with the roll. It sucks, but we have put thousands of miles on this boat in all sorts of weather, so we know what it will and won't do. We avoid open water and rough seas, which is easier to do than you may think in a boat that draws 3' 4" and has protected props. It is at it's worst in a beam sea. But then every boat I have ever been offshore in in a beam sea has rolled, including a number of sailboats and my friend's 70' custom American Yacht sportfish.

My goal, really, is to correct a small list and to add more water capacity.

[Figment]

Completely separate from the water tank discussion, can you identify what is causing the starboard list?

I ask because we experienced a similar situation on my father's powerboat, only to have to undo it later.
Long story short: Silverton 34 was listing to port, and a bladder tank was added starboard. Years pass, the inverter craps out, only upon removal of the final bolt do we realize that it's basically 12x12x18 solid copper. Reinstall (much lighter) modern inverter in same location, boat naturally lists to starboard. Removal of bladder tank inspires a long chain of other projects.

[Quetzalsailor]

You could experiment with sandbags. Try a stack on deck or in the locker, or down below.

I similarly 'proofed' the roof structure of our dining room bay when Sue wanted a hot tub up there; I bought enough garbage cans and filled them with water. Of course, failure would have been something important to avoid but my reasoning was that, while the bay was not original the stone wall above was. A century ago, someone had cut the wall out below and put something good in the nature of a honkin' large steel beam and had not disturbed the wall above. The weight of water was as nothing compared to the stone so what I was testing was the connection between the relatively short roof framing and the steel.

I corrected a list and trim issue in Quetzal by storing the spare 35lb CQR and rode in the port vee berth.

Both reversible experiments were successful.

[megalops]

Good ideas all.

I carry 21 gallons in jerry jugs on the bow, plus 6 gallons of gas for the dinghy, I could shift those over there and then have someone stand next to them to see what happens.

Also, I've been thinking on how much weight it will actually be. I doubt seriously that I will ever get 52 gallons in that bladder, I think 45 is much more in line most of the time. Water weighs eight pounds a gallon, so that is 360 lbs. Plus the weight of the bladder, not sure what that is yet, but West lists the shipping weight as 8lbs, so not very much.

I'm taking about 15' feet of 00 battery cables, a bunch of engine hoses, 2 cans of varnish (dried out probably) and some other junk out of the locker. All in all, I'm probably adding more like 300 lbs.

[mitiempo]

Oh, those gallons, the little ones. Up here a gallon weighs 10 lbs.

Why are there no smiley faces to use on this forum?

[Rachel]

We just have to express ourselves in words - bolstered by the occasional semi-colon/closing parenthesis ;)

I find it somewhat refreshing. Isn't it interesting how seemingly easy it was to go from the days of people expressing a wide variety of emotions in words only - i.e. letter writing - to a time where it seems odd to express emotions without emoticons?

Hmmm, did the letter writers of yore ever pen "smilies"? For all I know they did; although what I remember is detailed and subtle prose.

Go ahead, call me a Luddite (although.... a Luddite with a Laptop!).

[Ric in Richmond]

So far I nominate this a descriptive phrase of the year:

"It is a slow displacement hull (8 knots) that will roll peanut butter out of the jar in a beam sea."

[mitiempo]

Rachel

I seldom if ever wrote letters - I phoned.:) Most of my online time is spent on another forum (Sailnet) that makes it easy with their colorful options. I have written more on forums in the last 2 or 3 years than in the previous 40 years!

[Rachel]

Totally understood - I would have to say I called people much more than writing letters myself. I was just musing on something that I have thought about in the past, and which was recalled when you asked about emoticons.

That being how before there were telephones (in common use), people communicated very commonly by letters, and they didn't have emoticons at all. Yet whenever I read those letters of yore, I'm stuck by how expressive they were, with long, flowing sentences, lots of feeling and description, and... emotions.

But now it seems like one is almost compelled to use emoticons - when we are essentially writing letters again. I know that I've nearly reached for the "smiley" in business correspondence, but then of course I realize that no, that's not appropriate. But it's just so compelling! And yet obviously people got on fine without them before. I find that really interesting.

Anyway, pardon the ramble.

Rachel

[megalops]

8.35 lbs, actually (I looked it up) so we were both right, or wrong, I guess.

As far as emoticons go, I understand what you mean. I love the written word and how descriptive it can be with no embellishments, or even from leaving the right word out. The depth of Patrick O'Brien's dialogue always amazes me, and written in a form from 200 years ago with no overwrought phrasing.

Also, I think we are much more concerned about offending people than we used to be. Emoticons help with that :-).

I'm glad you liked the peanut butter thing Ric, use it in good faith!

Doug