Ventilators

[system 4-50]

After 12 months building on my sailaway (9 months on the water), I have done most of laying the floor.

Unable to travel in the cold weather to finish it, I have been thinking about how I'm going to provide adequate and BSS ventilation in the future.

 

My stove is in the centre of the boat and I'd like to bring most of the fresh air coming into the boat into the centre as well, at floor level. I don't want cold air from door vents travelling halfway down the boat before being heated.

I can't bring it down from the roof as I have too many flues up there so I thought I might bring it in through louvres in the cabin side and duct it to floor level.

 

I'd like to maintain positive pressure in the boat to help the stove and similar devices to vent exhaust gases out of their flues so I envisage a system of flap valves on these louvres admit more air on the windward side of the boat than the lee side. I am clearer about what I want achieve than how it can be achieved here!

 

I appreciate that the BSS approach is that as much fail-safe ventilation must be provided all the time as might be needed at any instant and I will go on to consider this later after I have got a fail-safe mechanism for providing as much ventilation at any instant as is required at that instant, designed and in place.

 

So, the point of this post is to ask the following:

 

Has anybody got louvred ventilation in the cabin sides?

 

Has anybody got ventilation with design features that hope to maintain positive cabin pressure?

 

Has anybody tried novel alternative means of ventilation other than mushroom farms?

[Nickhlx]

I am looking forward to seeing the replies to this one as I was considering the same myself..

 

Nick

 

 

[nb Innisfree]

I'm trying to imagine the design of the airlock for entry and exit of the crew.

Edited December 19, 2010 by nb Innisfree

[BEngo]

After 12 months building on my sailaway (9 months on the water), I have done most of laying the floor.

Unable to travel in the cold weather to finish it, I have been thinking about how I'm going to provide adequate and BSS ventilation in the future.

 

My stove is in the centre of the boat and I'd like to bring most of the fresh air coming into the boat into the centre as well, at floor level. I don't want cold air from door vents travelling halfway down the boat before being heated.

I can't bring it down from the roof as I have too many flues up there so I thought I might bring it in through louvres in the cabin side and duct it to floor level.

 

I'd like to maintain positive pressure in the boat to help the stove and similar devices to vent exhaust gases out of their flues so I envisage a system of flap valves on these louvres admit more air on the windward side of the boat than the lee side. I am clearer about what I want achieve than how it can be achieved here!

 

I appreciate that the BSS approach is that as much fail-safe ventilation must be provided all the time as might be needed at any instant and I will go on to consider this later after I have got a fail-safe mechanism for providing as much ventilation at any instant as is required at that instant, designed and in place.

 

So, the point of this post is to ask the following:

 

Has anybody got louvred ventilation in the cabin sides?

 

Has anybody got ventilation with design features that hope to maintain positive cabin pressure?

 

Has anybody tried novel alternative means of ventilation other than mushroom farms?

 

 

The first point is that for a private boat ventilation is a BSS advisory, so you can in practice do what you like. I am not sure what the RCD requires, and you need to be compliant with that if you intend to sell the boat within 5 years of 'finishing' it.

 

A flap on any ventilator which would result in it being totally or partly obstructed would mean that vent would be discounted totally or partly in the calculation of the ventilation area. However if the flap was either-or shring between two vents then I would expect that a sensible examiner would allow a single ventilator to be counted.

 

A fan would be necessary to ensure positive pressure all the time, but the average boat has so many sources of adventitious ventilation that I would expect it to be a large fan to actually achieve anything. The problem then [apart from noise, power, location] might be keeping the fire under control! Once the door or a window is open you lose not only the positive pressure but a lot of heat as well.

 

I agree that vents in the doors are stupid in a new boat because there are better ways which avoid draughts but still ventilate. I have my low-level ventilation ducted from the front of the boat under the fixed furniture. That way it is warmed up before it gets into the cabin. The high level vents are a mushroom farm, but there are alternatives here- pigeon boxes with a fixed opening, flying saucer vents and high-level side louvres all work.

 

N

[Chalky]

Has anybody got ventilation with design features that hope to maintain positive cabin pressure?

 

Has anybody tried novel alternative means of ventilation other than mushroom farms?

 

 

It was common practice on dreadnoughts to run the boiler rooms at positive pressure to increase the rate of steam production. Why bother with anything complicated - if its simple there's very little to breakdown and cause you grief.

[Alan de Enfield]

..............so I envisage a system of flap valves on these louvres admit more air on the windward side of the boat than the lee side. Has anybody got ventilation with design features that hope to maintain positive cabin pressure?................

 

Being a simple sort of person it sounds awfully complicated - example - what happens if the 'windward side' is the side you are moored up ?

[Artimis]

This is the one big question I have left to solve. How much and where

 

The RCD stipulates the volume of free or advantitious air needed is directly proportionate to the number of persons which the vessel is designed for.

That number is arrived at from the weight and ballance calculation.

 

I have no bloody idea what the weight and ballance will be and thus the number of persons the vessel is designed to carry so I guess the next obvious thing is to design in the common sense amount of ventilation needed.

 

Regs state that heating stoves under 4kw dont need a dedicated source of free air but I prefer to make provision for it as its common sense that what gets burned must be replaced.

 

I will have a mushroom leading to a low level outlet by the stove which will provide for it (vent is a larger cross section than the flue), but how much more free air do I need to provide for the rest of the boat?

 

The highlevel vents will be in the roof boxes

[Nickhlx]

Artemis :

The RCD stipulates the volume of free or advantitious air needed is directly proportionate to the number of persons which the vessel is designed for.

That number is arrived at from the weight and ballance calculation.

 

I have no bloody idea what the weight and ballance will be and thus the number of persons the vessel is designed to carry so I guess the next obvious thing is to design in the common sense amount of ventilation needed.

On ours, (62') there is a plate which says max. no of people allowed on board is 6

 

I wonder if this means the four of us, can only ask another couple to join us on a day trip. Alternative meanings which I think more likely, is that the designed overnight ventilation is for 6 people sleeping on board with the stove going. There are 3 double beds and any more than 6 would be getting "cosy"... its fine for 8 or so during a day trip though...

 

Nick

[Alan de Enfield]

.............I wonder if this means the four of us, can only ask another couple to join us on a day trip. Alternative meanings which I think more likely, is that the designed overnight ventilation is for 6 people sleeping on board with the stove going. There are 3 double beds and any more than 6 would be getting "cosy"... its fine for 8 or so during a day trip though...

 

Nick

 

On asking the same question some years ago I was told the maximum number of people was primarily based on 'balance' (rather than allowing them to breathe). It is something to do with what angle of heel you'll get if they all stand on the same side at the same time.

I assume there is a 'standard weight' for a person somewhere in the directives

Edited December 19, 2010 by Alan de Enfield

[Nickhlx]

On asking the same question some years ago I was told the maximum number of people was primarily based on 'balance' (rather than allowing them to breathe). It is something to do with what angle of heel you'll get if they all stand on the same side at the same time.

I assume there is a 'standard weight' for a person somewhere in the directives

 

 

OK - thanks ...

 

Nick

[Artimis]

I think for 'standard' weight, you have to read worst case senario which in the case of light aircraft, bodies are assumed to be 90kg or 15 stones each for the weight and ballance calcs

 

So, 6 bodies at 90k each, all stood on one side, must be able to be withstood and the vessel remain seaworthy, ..............so how much air do 6 people need?

[Nickhlx]

I think for 'standard' weight, you have to read worst case senario which in the case of light aircraft, bodies are assumed to be 90kg or 15 stones each for the weight and ballance calcs

 

So, 6 bodies at 90k each, all stood on one side, must be able to be withstood and the vessel remain seaworthy, ..............so how much air do 6 people need?

 

I understand the theory - but if things were getting "marginal", wouldn't the people move back into the centre of the boat voluntarily, or even at the instruction of the one who

wasn't brain-dead ? Seems another of those "laws / rules" for the sake of having a pointless rule ...

 

( but thanks for the responses)

 

Nick

[ditchcrawler]

I understand the theory - but if things were getting "marginal", wouldn't the people move back into the centre of the boat voluntarily, or even at the instruction of the one who

wasn't brain-dead ? Seems another of those "laws / rules" for the sake of having a pointless rule ...

 

( but thanks for the responses)

 

Nick

I dont think it is unknown for boating disasters due to everyone being on one side

[Nickhlx]

I dont think it is unknown for boating disasters due to everyone being on one side

 

Sadly, no... but I guess the plate was ignored too, else it wouldn't have happened

 

Nick

Edited December 19, 2010 by Nickhlx

[Keeping Up]

There have been capsizes, but the only ones I know of involving narrow boats have been when it was a small boat, there were far too many people, and many of them were on the roof. For example weren't there two Springer water-bugs hired as day-boats near Bristol or Bath, that attempted to return from the pub with something like 20 people on the roof of one of them.

[Artimis]

When I had a Broads holiday one year, I saw 4 city kids turn up to hire a boat and the girls were trying to negociate boarding whilst wearing 5'' heels and hanging onto rucksac sized handbags with one hand and shoulder mounted ghetto blasters with the other hand.

 

Therefore rules have to be in place to cater for people who are as impractical as this.

[Neil TNC]

Has anybody got louvred ventilation in the cabin sides?

 

Yes, on barge Maurice A, for low level ventilation.

 

Fabricated and welded in.

 

The "duct" behind is formed by strategically placed cabin side stiffners, that will be covered by bolted on galvanised steel plates. This will be spray foamed over...but...these vents have been stategically placed to be inside cupboards, here the lining will be removable for future inspection/painting.

Below the gunwale the ducting will be 125mm x 50mm kitchen venting, above the spray foam, down to a vent in the kickplate below the cupboard....or so the theory goes...