concrete ballast

[Alys]

hello, i have a narrow boat that sits very low in the water, i think because it had a good 6mm of steel put on the hull before christmas. It's caused a few probelms in terms of water coming in outlet holes (the front end where the gas tanks sit), though i'm hoping that'll be sorted today with a bit of welding and putting plugs in (having had an inch of water in it last night!). Anyway, i had the bright idea of removing some of the ballast to lighten the load, but it looks as though it is poured concrete (coarse). does anyone know if there is anyway of removing this stuff, or is any work likely to break through the hull?

[ChrisPy]

you can try a small hand held pneumatic (or electric) chipping hammer but it will be very hard work. I would not recommend a heavy breaker (looks like a road drill that workmen use to break up the road surface), it is heavy to use and will damage the steel.

[Alys]

wouldn't there be a (high) risk of damaging the hull through the vibrations / impact? (i won't hold you to your answer!)

[Alastair]

*DON'T* plug up your gas locker holes!

 

They are supposed to let water in. The gas locker should fill with water up to the level of the holes. Any gas leakage into the locker will then drain overboard.

[ChrisPy]

*DON'T* plug up your gas locker holes!

 

They are supposed to let water in.  The gas locker should fill with water up to the level of the holes.  Any gas leakage into the locker will then drain overboard.

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it seems the boat is trimmed so the water is coming in, so the holes are too low. If the trim problem is not resolved then new holes are needed, just above the waterline when the bow is low (with full water tank) and the gas bottle should be surrounded with something inert up to the level of the new holes. BSS gives guidance.

[ChrisPy]

wouldn't there be a (high) risk of damaging the hull through the vibrations / impact? (i won't hold you to your answer!)

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you will not damage 5mm angle iron stiffeners or 10mm bottom plate with a hand held chipping tool. There will only be vibration damage if the welds are not sound (cracked or lack of penetration). But if that is the case, the welds are damaged (faulty) already.

You can hire the tool at the local hire shop, 110VAC with a transformer. USE SAFETY MASK OR GOGGLES.

Try to crack across the slab and then lift off in sections between the bottom angle iron stiffeners. The concrete doesn't stick to steel.

Of course, if you've ever been dropped by a crane the concrete may already be cracked in some places.

[Amicus]

you can try a small hand held pneumatic (or electric) chipping hammer

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At you hire shop ask for a CP9, the pneumatic jobby, it'll need a 1 tool compressor as well, the electric tool is called a Kango hammer, generic name, I'd advise this-un if you have power handy

Taint going to be easy mind, take great care, keep away from the steel. Use the tool to cut grooves in the concrete and break it out in chunks. Spray with (lot of) water to keep the dust down. Wear gloves. eye protection, a mask, get a proper mask not an el-cheapo from the DIY shed, and ear protection. If your not used to this work get two or three mates and attack it is shifts otherwise it'll take forever. Tell the hire shop your busting concrete and they'll supply points and not chisels.

Sounds as if it has to be done and there aint no easy way, well there is a thermic lance or water jets, but we aint going there.

When you have got it done, find the geezer wot put it there and give him a smack, it'll make you feel better. good luck

[Alan Saunders]

Rolled steel ~7,850 kg/cu.m, Water ~1,000 kg/cu.m, Concrete ~2,400 kg/cu.m (maybe only 2,000 if it was not compacted).

 

6mm of steel added to to the baseplate would increase the draft a little less than 47mm - say about 1.5" assuming you did not plate the counter and that there is some sheer to the sides.

 

Assuming the ballast covers the whole baseplate you would need to remove the equivalent of (6x7850/2400=20mm) 3/4" of concrete overall to compensate. If you remove it locally you will create sumps that will fill with water.

 

Is the trim correct? Perhaps you could add ballast at the stern or remove it mostly at the bow.

 

Unless you have stripped out the inside of the boat you will find it difficult to obtain access and any method is going to be messy. I agree with Chris - a small chipping hammer. You might consider a disk cutter if you are confident of recognising when you have cut through the concrete are starting on the steel. It may not have adhered to the hull so cutting channels almost through to the steel might allow blocks to be removed. A boat builder pouring concrete into a hull would probably not measure proportions accurately or waste money on expensive cement so, with luck, it will be quite weak.

 

As Alastair says, an inch of water in the gas locker is not a problem. I suggest you consult a BSS Inspector before modifying the gas locker. The ones I have met have been very helpful, even proud of their ability to provide solutions to get a boat legal.

 

Alan

 

Chris and Amicus added more good advice whilst I was typing . . .

Edited February 14, 2005 by Alan Saunders

[ChrisPy]

At you hire shop ask for a CP9, the pneumatic jobby, it'll need a 1 tool compressor as well, the electric tool is called a Kango hammer, generic name, I'd advise this-un if you have power handy

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a standard Kango is a heavy tool, probably too heavy for this job. I agree you need a CP9 or the electric equivalent.

[Alys]

ok, sounds good. I can't really add ballast to the back, because the boat is already so low - basically the lumpy bit that surrounds the boat and acts as a fender type thing is below the water line. I've moved things about though so the bow is now at least higher than the back.

 

I bought the boat thinking how wonderful it's going to have a 'new' hull so will be nice and solid, and have paid for not seeing it in the water afterwards as the sale got rushed through. I'm going to redo the inside of the boat at some point, but when it is warmer, so maybe i could cut a sort of hatch through the floor, down the walkway bit (which is in the middle of the boat), at the bow end to get at the concrete? Anyway we shall see - at least i have some hope now!

[Alan Saunders]

ok, sounds good. I can't really add ballast to the back, because the boat is already so low - basically the lumpy bit that surrounds the boat and acts as a fender type thing is below the water line. I've moved things about though so the bow is now at least higher than the back.

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I call the 'lumpy bit' a 'rubbing strake' - a rounded steel profile about 2" x 1/2". The counter plate should be below water level - perhaps 2"- 4". The lower rubbing strake is commonly fixed level with the counter plate but some boats have the rubbing strake fixed a few inches higher. When it continues to the bow it usually rises so at the bow it is several inches above water level.

 

It is normal to trim the bow a few inches higher than the stern but make sure that sinks, showers etc. drain properly with the water tank empty or full (mine don't ) A quick survey of similar boats should give an idea of the norm.

 

Alan

[John Orentas]

Stand back and look at your problem again, most boats are ballasted too light. I bet it now looks and handles better than it did before.

 

Address your drain problems a separate issue, remember the water drains don't need to be more than a few inches above the water line as long as they have robust pipe and fittings inside.

[Big COL]

Stand back and look at your problem again, most boats are ballasted too light.  I bet it now looks and handles better than it did before.

 

Address your drain problems a separate issue, remember the water drains don't need to be more than a few inches above the water line as long as they have robust pipe and fittings inside.

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John

 

As I understand it the source of the drain has to be 10'' above the water line, or in the case of a pumped outlet the outlet pipe has to rise 10'' above the water line. The outlet can then be close to the water line, provided that the pipe work is constructed with glued joints and not of the O ring type, or you can use a continuous flexible pipe terminated on hosetails.

Edited February 14, 2005 by Big COL

[dor]

I believe for a private boat the 10inch rule is advisory, so not actually essential.

[DHutch]

As I understand it the source of the drain has to be 10'' above the water line, or  in the case of a pumped outlet the outlet pipe has to rise 10'' above the water line. The outlet can then be close to the water line, provided that the pipe work is constructed with glued joints and not of the O ring type, or a continuous flexible pipe.

 

Yes, but does a contunuasly welded gas lock count?

 

- i would have though it would, as long as it build as to a stadard equal to that require for the rest of the unter hull,

[david and julie]

If some of the concrete must come out and it isn't stuck to the steel you may be able to use a drill rather than a breaker. I would try a series of holes in the concrete to weaken it first, use a proper SDS bit in a hilti or kango drill etc on hammer, as it reaches the steel it will go much louder and you must stop. If you do a series of holes and insert a stout bar (as used by road diggers) you should be able to crack it from hole to hole and take it out in chunks. This sounds a damn site quieter and there is probably less chance of damage.

 

Rather you than me though!

[Yamanx]

Personally I would just have a go at it with a lump hammer and bolster, if it had to come out.

 

Then again you could dissolve it, maybe?

 

http://www.shumakerindustries.com/truckwash_endorsements.htm

[ChrisPy]

Personally I would just have a go at it with a lump hammer and bolster, if it had to come out.

 

Then again you could dissolve it, maybe?

 

http://www.shumakerindustries.com/truckwash_endorsements.htm

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I'd hate to risk breaking some of the stitch welds fixing the bottom stiffeners.

 

...... suck it and see, I guess.

[bottle]

If all else fails (tonge in cheeck)

 

Haul it out, cut the bottom off, get rid of the concrete and weld the bottom back on.

[ChrisPy]

If all else fails (tonge in cheeck)

 

Haul it out, cut the bottom off, get rid of the concrete and weld the bottom back on.

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......... so cruel