Recommissioning Fuel Tank in Keel

[Winf]

Originally Posted by GILow

Hi Winf,

First, let me congratulate you on your choice of boat. The SouthCoast 36 was very high on our list of choices when we were looking for a good comfortable cruiser a few years ago, and I have many photos of Southcoast 36 interiors as a source of motivation for our own interior rejuvenation whenever that happens.

I am posting here because I just went through a process that I suspect is very similar to what you face. Our Swanson 42 had a failed keel tank (freshwater) which was located under the engine and gearbox. In December I finally got around to dealing with the tank, and I learned a bit in the process, which may apply to your situation.

First, I am going to assume that given the very similar pedigree of our boats that the construction methods will have been the same, and certainly my very careful analysis of the SC36 years ago suggests they have a lot in common with our Swanson 42.

Second, I am going to assume that the previous owner did not decommission the tank just for the heck of it, in the case of our boat they most certainly did not give up on 420 litres of fresh water storage just for a simple problem.

So, I won't bore you with the details, but I pulled out our engine (all 450kg) in December and opened up the failed keel tank from the top, using an electric jigsaw. Then I extracted the utter evil gunk, removed the hideous failed bladder tanks that had been inserted to get around the original problem, washed it all out, sat back and worked out what had gone wrong.

Well, it appears that the keel tanks were lined with some kind of epoxy or hard setting liner which had cracked and failed, exposing the inside of the keel to the tank and thus probably causing foul "osmosis" tasting water (Acetic acid?) When this happened (around 15 years ago) the owner at the time just pushed in some flexible bladder tanks and used these. But of course they failed (they did not fit properly, they never could have, so they chaffed to bits in under five years) and the result was two big black pvc bags floating in scummy solution of water and diesel and goodness knows what.

So, my point is, the pressure test is a great idea, and if it fails I would seriously recommend you do NOT put any diesel, or ANY liquid in those tanks as cleaning them out will become a nightmare, particularly if they are full of now-contaminated diesel. I suspect you will find they too have a failed liner coat (maybe someone here can tell us what the layer of brittle, semi transparent lining material is likely to have been) and that they need some kind of sensible insert to be used again.

Next, I know you don't like the idea, but I would suggest that pulling the engine is worth the hassle. The SC36 came with around 50+ HP from memory, so the weight should not be a major concern, and you'll have a chance to clean up the engine if it needs it, clean all those fiddly bits of the bilge, get to know a really critical and time consuming part of your boat (the engine) but most importantly, you'll be able to open up the tanks properly and make a smart decision on the best way forward.

I don't know what the best way forward will be. I don't even know what I will do with ours right now. We are ok for diesel and water storage, at least for coastal cruising, so there's no great pressure to do anything, but if I had to I would seriously consider custom made poly tanks based on the suggestions of a few CF regulars who's opinions I highly respect.

Certainly, after my experience, I will never fit a bladder tank, but I admit to a bias that may be blinding me to their virtues. So be it.

Happy sailing, very envious of your lovely boat...

Matt

Wow. Great response.

Did a bit of bilge staring contemplation today and think I will leave this sleeping dog as is for now. She will come out of the water next season so will give some thought in the meantime to going the whole hog and removing the engine and tackling the tank repair properly.

We have a 30hp Yanmar which weighs in on paper at about 160kg but I need to get my head around how I would even begin to drag it out. I really would like to get some good access to that area though to give it the full treatment, not just the tank. Last year I spent a week off and on chipping, rubbing, wire brushing, tooth brushing and cleaning up the engine to give it a re spray as best possible but could do much better with it out.

Re the Southcoast 36, we are very happy with it so far. I'm very much the newbie at all this and is my first yacht but she seems sturdily built, is comfortable and sails well (to me anyway). I had read comments that they were more motor sailers than yachts but we scoot along quite nicely in a light breeze and in the heaviest seas we have had so far she felt very safe and stable.

What impressed us was the roominess for the size. We were looking at 40-45 footers mostly and she seemed bigger than a lot of them.

Thank you and thanks to all others who have taken their time to assist the thought process.

Winf

[gonesail]

when you do tackle it you may want to read up on folks that have cut out the side of their keels to get at the area and replace it with an aluminum fuel tank ... instead of trying to drop something in from the top

[JPA Cate]

Winf,

About the jerry jug covers, the way I made mine was one top piece with a slot for the handle, then one seam, and a hem. Not hard to hand sew (though I used a machine). Use a medium sail needle, and a palm. If you have acrylic canvas, cut it with a hot knife to melt the edges so they don't ravel.

Ann

[GILow]

Originally Posted by gonesail

when you do tackle it you may want to read up on folks that have cut out the side of their keels to get at the area and replace it with an aluminum fuel tank ... instead of trying to drop something in from the top

I was quite shocked when I first heard of this. Someone had done a similar thing to a Swanson yacht, similar to ours. (Swansons seem to be somewhat troubled by keel tank problems. Age? Construction?)

My reaction was that felt it was putting a heck of a structural integrity question on the hull overall. I imagine the forces on the sides of the keel as the boat heels significantly to be huge, compression on the downhill side and tension on the uphill side.

Just for the sake of avoiding removing an engine. I would never want to compromise that aspect of our boats strength. If I can pull our 450 kg monster out of the way, on my own, in less than a full day's work, at my first try, then surely hacking into the hull is not worth the risk. Or the work for that matter.

But I concede I am no naval architect and my concerns may be ill founded.

Matt

[GILow]

Originally Posted by Winf

Wow. Great response.

Did a bit of bilge staring contemplation today and think I will leave this sleeping dog as is for now. She will come out of the water next season so will give some thought in the meantime to going the whole hog and removing the engine and tackling the tank repair properly.

We have a 30hp Yanmar which weighs in on paper at about 160kg but I need to get my head around how I would even begin to drag it out. I really would like to get some good access to that area though to give it the full treatment, not just the tank. Last year I spent a week off and on chipping, rubbing, wire brushing, tooth brushing and cleaning up the engine to give it a re spray as best possible but could do much better with it out.

Re the Southcoast 36, we are very happy with it so far. I'm very much the newbie at all this and is my first yacht but she seems sturdily built, is comfortable and sails well (to me anyway). I had read comments that they were more motor sailers than yachts but we scoot along quite nicely in a light breeze and in the heaviest seas we have had so far she felt very safe and stable.

What impressed us was the roominess for the size. We were looking at 40-45 footers mostly and she seemed bigger than a lot of them.

Thank you and thanks to all others who have taken their time to assist the thought process.

Winf

Winf,

Yes the SC36 appears bigger inside than our S42, they are a great design. I think having two pointy ends on our boat costs us a fair bit of space. (And leads to a moment of confusion when we set off in the morning.)

Pulling the engine...? 160kg? If I remember correctly the engine is under the cockpit, just like ours, and is accesible from under the companionway steps? I think what I did (or a variation) might work for you.

To get ours out I simply lay two lengths of square section steel tubing I happened to have laying about in the garage from the engine beds into the main cabin. Slid a nice big 6 x 2" treated pine plank I had lying around under the engine as a "fall back", unbolted the engine mounts from the logs and slid the whole engine forward using a 10:1 block and tackle from the forward end of the plank. The engine mounts slid onto the rails and then the whole lot came forward slowly and easily. I did not know how much the thing weighed at the time (I had been told 300kg, not 450kg oops!) so the steel tubing was probably a bit under-nourished, but it coped fine, I took my time and at no stage were there any "Oh sh-t" moments.

But oh, the joy of being able to get to those tanks. Feet down into the keel section under the engine and I could sit and work at my leisure. You talk about wanting to do a proper job. That's the way to do it properly I think, anything else is just going to be a compromise.

I confess to pulling off the engine access panels now and then, just to gaze into that lovely, clean, dry, white painted bilge. Sad, I know, but you say you've been doing a bit of bilge contemplation, so you probably understand...

Matt

[Mocking]

Hi WINF

I would be interested to see what you do as I have the same situation ( thank you GILow for letting me know re this post) in my SC 36.

The owner has made fairly thorough records of what he did during the construction and my SC36 also has a keel tank of approx. 110 ltrs. I also have a 65 ltr tank below the starboard seat up top. He has put a manual pump to transfer from keel to day tank. Having said that there is also a note in his book saying to not use the keel tank as it is there for ballast.

I can see where the fuel pipe goes down to the tank and I also have a breather tube coming out of the depths of the engine room. Other than that I can not find any evidence of an inspection port.

At the moment the day tank is satisfactory however, latter this year I will need to sort it out in preparation for longer trips next year.

So any info on what you find/ challenges would be appreciated.

Regards

Manni

[Winf]

Hi all

Ok a zombie thread here but have now worked my way into the keel tank from the original post. Haven't removed engine.

Firstly, removed the rusty looking tank filler fitting. Tank was filled to the brim with "fresh" water and an oily diesel residue. Sucked all that out for disposal.

Got an endoscope and started looking. Tank is fibreglass. No baffles. No obvious damage and tank was relatively clean other that the walls looking dark with diesel residue/tar looking film and some sludge at the bottom.

Bit the bullet and cut a 200mm x 100mm access hole into the top of the tank under the prop shaft.

Removed the sludgy stuff. Have been rinsing out repeatedly with degreaser, sugar soap and methylated spirit (not at same time). Able to do some limited scrubbing/mopping with contraptions fashioned from cleaning brushes, short broom handles and duct tape. Very hard to reach all points in the tank though, arms just aren't long enough.

Haven't pressure tested yet.

Question is, how clean does a tank need to be?

There are no floaties or sludgy stuff remaining. Cant seem to shift the tarry looking stuff on the walls easily. Floor looks pretty clean. Pics attached.

Plan is to use this tank as additional storage and as per RaymondR's suggestion, pump from it from the keel tank to the upper tank via a water separating filter. When the upper tank fills it will overflow back to the keel tank. The upper tank will supply the engine through a separate line through another water separating filter and then through the injector filter.

So in theory all fuel will be passing through three filters. Would also give the tanks a full biocide and conditioner type treatment fuel when refilled.

If I need to get it cleaner, any suggestions on moving this tar looking stuff?

[AndyEss]

I'd try to remove the tarry stuff with diesel.
If diesel doesn't remove it - it doesn't matter.

[Sailmonkey]

That’s cleaner than about 99% of non-new fuel tanks out there!!!!

[Pete7]

The only thing I can think of to get that any cleaner will be a hot pressure wash (not the little domestic ones) and dish washer tablets.

What are you going to put back in the way of hatches? how about something like this? they do a clear lid so you can see inside without opening it.

Access Panels|tank|hatch|boat|water|TCL4

[Cheechako]

That looks very clean to me. Many tanks have a lot of gunk in them.

[GILow]

Regarding the access hatch, I did some digging around when I was making my diesel day tank, and even spoke to the chemistry guy from a local plastics manufacturer, and it turns out that conventional Perspex is extremely diesel resistant. So I made mine out of Perspex and three years later it still looks perfect.

[Wotname]

Originally Posted by GILow

Regarding the access hatch, I did some digging around when I was making my diesel day tank, and even spoke to the chemistry guy from a local plastics manufacturer, and it turns out that conventional Perspex is extremely diesel resistant. So I made mine out of Perspex and three years later it still looks perfect.

Good to know

Were the seams welded or glued (and with what) or ???

EDIT: just noticed you were talking about the access panel, not the whole tank

[GILow]

Originally Posted by Wotname

Good to know

Were the seams welded or glued (and with what) or ???

EDIT: just noticed you were talking about the access panel, not the whole tank

Would have made a fun tank hey? Kinda fish tank feel.

This was the fibreglass tank that half a dozen people assured me was going to kill me. Touch wood, so far they've been wrong, but if I disappear in a giant oily diesel-flavoured ball of flame next week... they were right.

[Winf]

Thanks for all the responses. Much appreciated.

I'll give it a few more rinses, dry it out then try a bit of a final diesel rinse.

Access hatch wise, thinking i will fabricate my own from ply and epoxy. Interesting about the perspex as an option. Will give that some thought.