FluffMagnet

Just a quick note in case others are in need of these: I have finally been able to order six "large" mushroom vents from Vertex Exports, via Midland Chandlers. £230 inc VAT & shipping for the six, which is pretty good IMO. Less good is the 7-8 week delivery, but that's what you get for knowing what you want.

Aww. I didn't mean it like that. I'm sorry if it came across as a "slap down". It just happens to be a classic forum bully tactic to hijack genuine questions and make the thread about something completely different that they feel more comfortable having an argument about. Which is one reason I rarely share more information than necessary when posting; I know what I post will be examined in great detail by Internet know-it-alls, eager to spot some error (or spelling mistake) that they can point to and shout "look, you're doing it all wrong!". I guess it makes them feel really important and stuff. In any case, the resulting argument is never worth my time, so I hope you don't mind me refraining from being drawn into one. Now if anyone has any further suggestions for boat roof vents with a ~120mm internal diameter, I'm all ears eyes!

Yes. I think so too. It's definitely an option, though the idea of spending 6 x £60 only to discard much of what makes them so expensive (I also have no need for the liner) is a bit of a turn-off.

Yeah, and I appreciate the suggestion! Here's a dimensional diagram of the "Athos" model:

I think I do. I think I do. Yes. I keep a spreadsheet listing every single on-board consumer, its power draw, and estimated runtime / 24h. It also includes the distances to the distribution boards which each consumer is connected to, automating the calculation of the amount of wire of different dimensions that will be needed, and how many fuses (and what size) each distribution board will require.

I already said I didn't want to go "in depth" on the design of my ventilation system, but I guess I'll have to explain a few things: 1) The fans are individually controlled. That is any fan can be on at any level independently from all others. For example, the forward bedroom can get a gentle flow of air while the bathroom fan is on half power and the galley fan on full blast. 2) The fans are controlled by PWM (Pulse-Width Modulation). This means that they draw less power the lower their speed. The fact that the fans have a maximum power rating of 5.4W only means that they are capable of moving more air as need arises. 3) The fans will not be "always on". While having manual controls (a simple momentary pushbutton), the PWM dimmer units are also controlled by the central computer, a Raspberry Pi, which is always on, and always online (using about 7.5W). This is also equipped with (several) temperature & humidity sensors, allowing some automation of climate control (it will also control a Webasto diesel heater and, when shore power is available, a Meaco dehumidifier). Ah yes - I have looked at these. Definitely an option. But I would need to butcher the internal opening/closing handle, as it would interfere with the fan. I'm also concerned that the low height of the units mean what's left of the screw will still protrude inside the cabin when fully closed.

Feel free! I think it's possible to question almost every design decision I make - and I do too I'm not, however, interested in having any lengthy discussion about this, suffice to say the fans are needed because of the size, shape, layout and existing ventilation of my boat. And the fans will be very effective even at whisper quiet speeds - already tested! This is one of the benefits of choosing a larger diameter fan. They will also be able to shift huge amounts of air when required - such as right now ? I believe I have located the manufacturer of these vents; a company called Vertex Exports in Uttar Pradesh. I have sent them an inquiry.

Sounds like a nice and cheap solution. Not sure how well two co-rotating sets of blades will perform, though I'm sure I've seen some server computer case that used them (noisy as *&#!£$) There are round fans too, which cost quite a bit more, but are designed for ventilation use and a lot cheaper than the bulky bolt-on "marine" vent fans I've seen, one example being the San Ace "RF" (round frame?) series: http://uk.farnell.com/sanyo-denki-sanace-fans/9rf1312p3h001/axial-fan-136mm-12vdc-70-7cfm/dp/2679913 For larger fans, look at combustion engine cooling fans, which are available in surprisingly small sizes, e.g. https://www.ebay.co.uk/itm/153010395167 Edit: For the record, I will be using the Sunon EEC0251B1, of which I have already purchased 10pcs. 184m3/h, or 108 cfm, at 44.5dBA noise level and 0.45A current draw (5.4W). They will be individually controllable through PWM, so can run whisper quiet with very low power draw, while still providing meaningful air flow.

Not really; the next (standard) size down is 80mm, which would whine like a turbo-jet if you wanted to move any significant amount of air. 120mm is the sweetspot.

Please disregard them. They will not be fitted, and this is about finding 120mm roof vents.

I need that size because I want to use 120mm 12V "PC" fans for the ventilation; these fit neatly inside the roof insulation, with both being exactly 1" thick. Cheap as chips too, and relatively quiet (yet powerful) due to their large diameter. I could fit them under 4" i/d vents, but this would reduce the efficiency by ~50%. I'm kicking myself for not having purchased the vents when I designed the ventilation system last year - I think they were "in stock" then - I Just didn't take into account that the product might vanish between concept and implementation Lesson learned: don't hold fire on that "buy it now" click! I think so too, but I haven't been able to find much, despite 120mm being a fairly standard ventilation pipe dimension. Suggestions? So you did, and I made sure to have a stiff drink to hand before checking the price As it is, it would make far more sense to order 25 pcs @ £750 from BCMW and try to flog the surplus 19 than spend £2k on the six. Edit: Here's an animation I made, to illustrate the concept:

Thanks, I now have, and they won't Apparently they "import them themselves", but stupid me forgot to ask from where! At least this means there are multiple sources of these things, which gives me some hope Dear? They're £276.52 plus VAT each. That's not "dear", that's daylight robbery! Times six, inc VAT, the bill would land on two grand ? Or to put it another way: I could buy seventy-two of them from Black Country Metal Works for the same amount... Done. Long time ago. One of the first places I look for pretty much anything.

Black Country Metal Works also sell directly to the public. And while "standard size" (6" x 4") mushroom vents are easy to find - either via search engine or on eBay etc - the only company I have been able to find that sells the "large" (6¾" x 4¾") type is Black Country Metal Works.

Hi all - my first post here, so please be gentle :) I am fitting out a 45' barge and I'm desperately seeking six "large" (6¾" outer dia, 4¾" internal dia) mushroom vents* - colour and material irrelevant (I'll even accept plastic at this point!). It seems the only company who makes them is Black Country Metal Works, but they won't produce any unless they have an order for 25(!) pcs. Short of spending the £750 required to meet their minimum order quantity, what are my options? *) It is important that the vents don't have any internal protrusions, such as a handle for closing; the vent base must be flush with the cabin roof even when screwed down. This is because I will have fans mounted on the inside, which any protrusion would interfere with.