The ventilation game

August 16th, 2009

One of Innocenti’s drawbacks (which, to be fair, is part of the reason she was cheap for her size) is that her fit-out has been done by a succession of enthusiastic amateur owners, of which I am merely the third or fourth. As she was originally built in 1991 and fitted out fairly cheaply, her insulation leaves a lot to be desired – which results in being too hot in summer and too cold and damp in winter.

Special mentions on this should go to the doors onto the foredeck which, despite being painted tromp d’oeil style to look like wood, are in fact made from steel. They get roasting hot in the summer and run with condensation in the winter. I’m working on a solution to this, which is to fit an internal double-glazed door behind them, but it needs a competent joiner and not inconsiderable expenditure. I will be on the case once my next paycheque has cleared!

But in the course of considering how best to solve this particular problem, I noticed something else that was lacking at the bows – proper ventilation. Boats are supposed to have two kinds of ventilators – top vents which let warm stale air out, and bottom vents that let cool fresh air in. Hot air rises and all that. Innocenti has lots of top vents, but the bottom vents are scarce – there’s one in the lower part of the kitchen door, and one tiny one (better described as a mid-vent, because it’s about 50cm off the floor) in the aforementioned foreward doors.

So, for some months now I’ve been considering how best to provide alternative ventilation at the forward end of the cabin, because any new internal door will block off the airflow from the existing tiny ventilator. The plan I came up with was to fit cowl ventilators (like the kind you have on an old-fashioned steamship) in the foredeck to direct air into the locker below, and then allow the air to circulate from the locker into the cabin. As a bonus, this ensures that the locker (which is nearly always damp) also gets ventilated. The trouble is that cowl ventilators are expensive – at least £35 each – and that water can get into them which gets messy quickly. Having exhausted my various preferred online chandleries, I hit upon the mighty eBay. Sure enough, a Maltese firm could supply me with some very nifty cowl ventilators with an auto-shutoff mechanism that prevents any water on the deck from going down the vents. Total price, for two ventilators, including shipment from Malta, £100. Expensive, but getting something similar in the UK would have been over £150!

When the vents arrived, the next challenge was to drill two 93mm holes in the foredeck. I went to Mackays, purveyors of tools and engineering supplies to the gentry of Cambridgeshire, and obtained a 92mm hole saw (they come 92 or 95 mm, frustratingly, but I reckoned too small was better than too big) and set to work with the power drill. What I acheived was a hot smell, some sparks and swarf, the beginnings of a hole about 2mm deep (the deck is 6mm thick) and a blunt holesaw. Oh dear. Turns out that the hole saw needs to run at a low speed (90rpm) and that my drill doesn’t have enough grunt to turn it at that speed. Back to Mackays for a new holesaw, some cutting compound (I’d forgotten about the importance of this as I rarely do really heavy metalwork) and then I managed to borrow a gruntier power drill with, crucially, a low speed gearbox from Andy, a neighbour.

Andy’s drill made reasonable work of the deck, although each hole probably took me at least ten minutes to drill, with a lot of stopping to allow the blade to cool and apply more cutting compound.

But once we had holes, everything else was pretty easy.


The first piece of the ventilator gets stuck down to the deck with waterproof sealant (I used CT1 – the boatowner’s friend: transparent adhesive sealant that sets in the wet, magic stuff) and then the rest of the mechanism attaches on top.

first piece

There are lots of little buoyant balls that go on top of the first piece, and then rise up if there’s any water on the deck to shut off the flow.

Then there’s a piece on top to hold the balls in place, and an adjustable piston you can use to vary the amount of ventilation by pulling a knob underneath.


There’s a cover that goes over the top, and then you can attach the actual cowl assembly around the vent itself.

finished ventilator

The boat seems to be cooler now on sunny afternoons, so I reckon they do work!

I’ve also fitted a solar panel a few weeks ago – a self-adhesive thin-film panel, very subtle – which produces 68W in full sunlight, which is pretty good going. It does cut my generator usage down, although it’ll take a long time to pay for itself!

solar panel

2 Responses to “The ventilation game”

  1. John and Jackie Says:

    The lovely thing about solar is that it gets cheaper the more you produce! Also, the convenience of being able to leave the boat for a bit with the fridge running is great. (Coming home to warm beer and green sausages is too depressing for words!)

    The ventilators look Proper-Job!

  2. Michael P-J Says:

    My fridge is gas, so that doesn’t happen to me very often!

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