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Laying joists in floor.


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17 minutes ago, Murflynn said:

modern narrowboats have angle steel bottom stiffeners with the horizontal flange uppermost, with a timber (maybe 50x50mm) fixed to the top flange, to which the plywood structural floor is fixed. 

And cutouts in the steel stiffeners to let any water drain to the stern. What is the boat?

Edited by Jen-in-Wellies
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45 minutes ago, Charles_Graham said:

was wondering what size joists are typically used for under floors 

 

ta

IMG_0066.JPG

That looks well strong. Most modern narrowboats don't have the long fore-aft stiffener. Most of the strain in that axis is taken by the sides of the boat and gunwales.

 

My widebeam has 2 sets of fore-aft stiffeners because all other things being equal, the wider a boat gets the weaker it becomes from bow to stern and the less reliant it should be on the sides to stiffen it.

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Been some big alterations to that hull, a bulkhead and  more has been cut out, how old is it?

It has a very narrow base plate and steep angle side sheets.

There is some sort of port on the side?

Needs gaps in cross angles on both sides to let water flow back

Edited by hider
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On 21/05/2019 at 22:03, hider said:

Been some big alterations to that hull, a bulkhead and  more has been cut out, how old is it?

It has a very narrow base plate and steep angle side sheets.

There is some sort of port on the side?

Needs gaps in cross angles on both sides to let water flow back

The boat was built by students in a Nottingham school, late 70s I think.

 

I don't know what that port on side was for, maybe a repair of some kind?

 

There are gaps in both sides to allow water to flow down to bilge in stern.

 

I may cut those uprights down an inch or 2... may give more head room, but it is still quite tall inside ass is....

 

Do I need stainless bolts or can galvanised do?

 

 

 

IMG_2508.JPG

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2 hours ago, Charles_Graham said:

Do I need stainless bolts or can galvanised do?

 

It depends on whether you think the bilge will get wet.  I put in stainless steels ones - a bit of an overkill, but you never know when you are going to get pipe or pump leaking.  

If I were doing the job again I'd probably use something like these:

https://www.screwfix.com/p/timco-in-dex-exterior-carriage-bolts-organic-green-10-x-220mm-10-pack/41338

 

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3 hours ago, Charles_Graham said:

I may cut those uprights down an inch or 2... may give more head room, but it is still quite tall inside ass is....

Personally I wouldn't bother.  You got ready drilled bolt holes to secure both the upright framing for the sides and the cross-members for the floor supports. 

Don't forget you don't know how much room for the ballast you may need and it's always good to have space for air to move around in the bilges.

 

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2 hours ago, koukouvagia said:

If I were doing the job again I'd probably use something like these:

https://www.screwfix.com/p/timco-in-dex-exterior-carriage-bolts-organic-green-10-x-220mm-10-pack/41338

I recall a video on here of someone making an awful lot of noise using a Hilti gun or similar to attach his battens. Seemed to be effective and quick. 

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20 minutes ago, WotEver said:

I recall a video on here of someone making an awful lot of noise using a Hilti gun or similar to attach his battens. Seemed to be effective and quick. 

OK until it goes wrong.  I believe special training is mandatory to buy or hire a proper Hilti gun.  

Edited by Murflynn
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13 minutes ago, Charles_Graham said:

Is this enough ballast?

 

mostly steel and lead...

 

 

 

 

You won't know until you fit out the boat.

It will depend on what you are putting into it.

 

Make sure you leave some areas of the floor easy to lift so more can be added / some taken out.

 

It is unlikely that you will have it right - even fitting (say) the Kitchen on one side will make that side 'lean' over so you will need to move some ballast to the other side.

 

It certainly wont be as you have laid it out - you may need less at the rear to allow for the engine, maybe more at the front - where are the toilet tank, water tank and gas bottles being fitted ?

 

(I think that big green lump may need to be removed otherwise you will have a big lump in your carpet.)

Edited by Alan de Enfield
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Well spotted Alan, will remove that lump asap - It actually turns out thats the hot air exhaust outlet.

 

Which I thought was a big air intake, (local knowledge on the forums)

 

Ya water tank - 400Litres in the bow, plus a 13kg gas bottle. Then open plan mostly, then bedroom,  bathroom, engine room.

 

So I will try and counterbalance things,.

 

As you say I'll only know when I fit out, but as a starting point is this ok - do I add more that I have left over?

 

Will it be balanced ok at edges,

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1 hour ago, Charles_Graham said:

Well spotted Alan, will remove that lump asap - It actually turns out thats the hot air exhaust outlet.

 

Which I thought was a big air intake, (local knowledge on the forums)

 

Ya water tank - 400Litres in the bow, plus a 13kg gas bottle. Then open plan mostly, then bedroom,  bathroom, engine room.

 

So I will try and counterbalance things,.

 

As you say I'll only know when I fit out, but as a starting point is this ok - do I add more that I have left over?

 

Will it be balanced ok at edges,

The only way to not to make this trial and error is to calculate the weight of the boat, using the density for steel and lead and the thicknesses and sizes of the hull plates and ballast. Add in the weight of engine, fuel, water (400kg), plywood lining, fixtures and fittings. Then use Mr Archimedes to work out how deep the draft will end up to counteract that weight.

Just as a comparison, my boat is a typical 57' modern narrowboat with a Japanese engine. It sits around 2' draft at the stern, rather less at the bow. It has 40 to 42 3'x2'x2" paving slabs under the floor as ballast, each weighing around 145lb. The total ballast weight is around 2.6 ton.

 

Jen

Edited by Jen-in-Wellies
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When I fitted our boat I used 2ft paving slabs two deep over most of the floor, the day after launching I had a concrete paving coffee table on the starboard side at the front of the lounge and nothing under the floor at all behind the engine room and all the rest I could reach removed. I replaced the concrete with a ton and a quarter of steel all near the bows on the starboard side.

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I've looked again at your pictures and I'm wondering about those triangular stiffeners.  Was the original floor level above these?  You seem to imply that you want to lay the wooden floor joists as close to the base as possible.  If this is the case then these bits of metal would protrude above floor level and would be a right pain.

Sorry, if I've misunderstood your plans.

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400L of water, and 1, 13kg gas cylinder.

Would you have room to double this up to 800L and 2 gas cylinders?

Too smaller tank, and you are forever refilling, and the gas always runs out, when a new one is not available.(and half way through cooking dinner)

We have a fairly standard layout, where the top of lower part of the water tank is the floor of the gas locker, and one side of the locker is the top part of the water tank.

This also lifts the gas locker base above the waterline, for the locker gas drains.

 

Bod

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1 hour ago, Jen-in-Wellies said:

The only way to not to make this trial and error is to calculate the weight of the boat, using the density for steel and lead and the thicknesses and sizes of the hull plates and ballast. Add in the weight of engine, fuel, water (400kg), plywood lining, fixtures and fittings. Then use Mr Archimedes to work out how deep the draft will end up to counteract that weight.

Just as a comparison, my boat is a typical 57' modern narrowboat with a Japanese engine. It sits around 2' draft at the stern, rather less at the bow. It has 40 to 42 3'x2'x2" paving slabs under the floor as ballast, each weighing around 145lb. The total ballast weight is around 2.6 ton.

 

Jen

................  and of course you need to undertake moment (lever arm) calculations to establish how far away from the centre of the boat (calculated both for the fore & aft sense and athwartships) the centre of gravity of the ballast should be.   If you are not familiar with spreadsheets and moments then you may be better off guessing and making sure there are plenty of removable floor panels so you can adjust things later on.

 

having said all that, a typical new sailaway boat (shell, floor and engine) will have nominal ballast installed by the hull builder which will generally be near enough.

 

 

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1 hour ago, Jen-in-Wellies said:

The only way to not to make this trial and error is to calculate the weight of the boat, using the density for steel and lead and the thicknesses and sizes of the hull plates and ballast. Add in the weight of engine, fuel, water (400kg), plywood lining, fixtures and fittings. Then use Mr Archimedes to work out how deep the draft will end up to counteract that weight.

Just as a comparison, my boat is a typical 57' modern narrowboat with a Japanese engine. It sits around 2' draft at the stern, rather less at the bow. It has 40 to 42 3'x2'x2" paving slabs under the floor as ballast, each weighing around 145lb. The total ballast weight is around 2.6 ton.

 

Jen

I got the total weight required right, just the distribution wrong

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22 minutes ago, Murflynn said:

having said all that, a typical new sailaway boat (shell, floor and engine) will have nominal ballast installed by the hull builder which will generally be near enough. 

Especially if the sailaway shell builder also does fit-outs. Piper were pretty much spot on with my boat. I ended up moving one paving slab from the heavy to the light side when it became evident that my fit-out was rather lopsided for weight distribution.

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4 hours ago, koukouvagia said:

I've looked again at your pictures and I'm wondering about those triangular stiffeners.  Was the original floor level above these?  You seem to imply that you want to lay the wooden floor joists as close to the base as possible.  If this is the case then these bits of metal would protrude above floor level and would be a right pain.

Sorry, if I've misunderstood your plans.

You're right, I was hoping to go as low as possible with floor as Im 6 ' 3".

I too just noticed these stiffness, so was thinking let them stick up, I can cut around them. 

 

4 hours ago, Bod said:

400L of water, and 1, 13kg gas cylinder.

Would you have room to double this up to 800L and 2 gas cylinders?

Too smaller tank, and you are forever refilling, and the gas always runs out, when a new one is not available.(and half way through cooking dinner)

We have a fairly standard layout, where the top of lower part of the water tank is the floor of the gas locker, and one side of the locker is the top part of the water tank.

This also lifts the gas locker base above the waterline, for the locker gas drains.

 

Bod

Id be interested to see your bow set up Bod, prob a bit late for me now but I got the water under floor in deck 0bviously, then the bow locker had just enough room to fit the 13kg, thats if it passes inspection. My concern at the moment is to just get ir completed and in water, to live on. It was a hell of a lot of work to get it to this stage, and Im beat!

 

3 hours ago, Jen-in-Wellies said:

Especially if the sailaway shell builder also does fit-outs. Piper were pretty much spot on with my boat. I ended up moving one paving slab from the heavy to the light side when it became evident that my fit-out was rather lopsided for weight distribution.

Jen, the concencous here on boat yard is to get plenty of ballast in and weigh her down, so I've chucked some more of the steel in. My concern with the ballast was because of the drainage holes we cut in hull in the bow. Its close to the water line. By right I should drop this in water and check, but that would be 2 lifts.

 

Graham

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7 minutes ago, Charles_Graham said:

Jen, the concencous here on boat yard is to get plenty of ballast in and weigh her down, so I've chucked some more of the steel in. My concern with the ballast was because of the drainage holes we cut in hull in the bow. Its close to the water line. By right I should drop this in water and check, but that would be 2 lifts.

 

Graham

I understand why you would want to avoid the cost of lifting the boat in and out. Sums are going to be the only way to avoid this, unless you can copy another boat near identical to yours in hull design, engine, tank capacity, fit out and other loads. On a 2.1m wide narrowboat, say 15m long, assuming the ends are square, which they aren't, except on skips, then adding 100kg of ballast, or any other weight increase the average draft of the boat by 3mm. Getting the drainage holes at the front higher from the water for the same weight boat means moving the ballast to the stern.

 

Average draft(m) = Weight/(length(m) x width(m) x water density(kg/m3))

0.003m = 100/(15*2.1*1000)

 

A 15 ton narrowboat of this size will have an average draft of 15,000/(15*2.1*1000) = 0.476m, or about 18.7".

 

This is very simple calculation. There is a better one here, specifically on narrowboats, with some reasonable estimates for weights of engine, fit out, liquids and so on that will give you an idea of ballast weight required for a particular draft. The ballast affects stability as well as draft, but these are more complicated calculations. Lower down weight is better for stability, which is why ballast is under the floor, rather than on the roof.

 

Jen

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