High air flow / low battery consumption?

[JohnWms]

The solar vents work okay. There's one in the head and it runs quite a bit considering its cloudy ALL the time up here. They don't move a lot of air but some is better than nothing.

The battery only lasts a year or so before it won't hold a charge. Replacements are a lot cheaper at Radio Shack than they are from Nicro.

[Tropic Cat]

I've been contemplating this problem for a while now. In my Cat we have a forward stateroom on the bridgedeck which has no ventilation. In Florida, summers get slightly uncomfortable (OK, that's a bit of an understatement).

I was wondering about trying 12" electric automobile radiator fans. They draw 8-12 amps at 12 volts (way too much current) but move 2000 - 3000 cfm. So, by reducing the DC voltage to some lower point, say 4 or 5 volts will in fact reduce their current draw and motor speed, right? Should move lots of air and be silent as well without killing the battery.

Any thoughts?

Rick in Florida

[JohnWms]

When you say *no* ventilation does that mean no dorades or anything? It seems like you'll need some way to have an "in" and and "out" so any fan can work better.

Otherwise, your assumption is correct in that reducing the voltage reduces current draw, to a point. It *is* possible to damage some electric motors with too little voltage. They can draw too much current to compensate for a voltage drop.

Maybe first pick up one of those Caframo fans and experiment with placement? I tend to like to build things in permanently too but the portable fans have been a pretty good solution for me.

[Doghouse]

I like the idea of the cardboard door with fans to test. I may try that this weekend. I have 12 older 210mm fans from a server we tossed out at work, and I may see how they do. (just 3 or 4) I figure 4 would be about 2ah draw so my battery should be able to handle that for 12 hrs. I will have to do some testing. Thanks for all the tips. NewEgg.com has 105 cfm fans for 13.99 with a speed control so that may be a cheep starting point for anyone who wants to experiment. I will post the results of my tests here as soon as I have some.

[Tropic Cat]

"no ventilation" means it's damn hot in there!! I have openings in the bulkhead which open into the salon, and a hatch. Plenty of room to pull and push air around, I just have to come up with a power efficient way to do this.

I advocate large fan blades turning slowly. They move a lot more air than those tiny (and noisy) muffin fans.

Rick in Florida

[Alan Wheeler]

Rick, just as a thought, what color is the hull?? Dark colors will heat the insides up like an oven. You could solve some heat related problems by changing the hull color to white, if it is say Blue or Red or what ever. Just a thought.

[Tropic Cat]

Alan, I appreciate the thought, but the Bridge deck is white, the Hulls are cream colored. The real problem is 95 degree days and clear blue sky, ie... direct, radiant sunlight.

Here are the openings I plan on using for fan(s). I think these circular cutouts were designed for passive ventilation but look perfect for large slow turning fans.

Rick in Florida

[Tropic Cat]

oops, I apologize for the large photos

[Talbot]

rick, dont you have a hatch above that compartment (there is on either side on the 9m) If so, a wind scoop will solve your problem (see http://www.seamarknunn.com/catalog/items/item4032.htm)

[Tropic Cat]

Mark, Yes, I do have a hatch in the stateroom, to the side of the berth over the companionway.

I checked your link, it sort of looks a bit ostentatious, and I can't figure out what supports it on the cabintop. Does it actually work?

Rick in Florida

[Alan Wheeler]

Thanks for the Photo. No it's not to big, it's great. Interesting layout, I take it you can walk around the front of your seating area?
OK, the important aspect of ventilation is "air flow". You need to draw air through. If you place a fan at the doorway, you will cycle 98%of the air around that fan only. That equates to wasted power. You need to make the fan the exit and the inlet at the opposite end. Whether that means the fan at the door or not, is up to you. But drawing air through the entire cabin is essential. My suggestion is that the cabin entrance is the "Intake" and the fan goes the opposite end.
Can I see a window open on the left up forward? or is that a bug screen only? A fan there would be good. Otherwise, you need to place a Dorade vent on the cabin top forward somewhere. You can place a fan inside that for very calm days, but it breezes, the Dorade cowl facing forward will allow air flow. You can swivel the cowlings around to suit wind direction and as wind is usualy on the nose while at anchor, it allows a natural air flow through the cabin and out the hatch.
If you place a fan inside, DC fans can be reverse rotated. So a simple switch could mean you could force air in either direction to suit conditions and direction.
Hope that helps.

[Talbot]

rick, these wind scoops work well. They are held up by rope from the top secured to something convenient like the shrouds, spinnaker halyard etc.

[Tropic Cat]

Alan,

I have 6 side windows which can be removed and the openings hold screens. Unfortunately, only one of these is in that forward stateroom (which is on the other side of that bulkhead in the photos). In addtion, that stateroom has a hatch. The window in the photo is in the head, portside forward.

Well, I'm boatless for a week or so. I just dropped the boat off at the yard to have the starboard shaft looked at. Alan, the weather here is warming up, and I fear I have moisture in both fuel tanks again. When motoring this morning, white/gray steam from boat engines for the entire hour of motoring.

Rick in Florida

[Alan Wheeler]

No way water in fuel will do that. If you have water cooled exhausts, that is all it is. quite normal. If it is dry exhaust, it maybe a bad sign, such as a blown head gasket. Water in fuel bad enough to cause steam in the exhaust will stop an engine dead. It takes very little to stop the engine. Even one drop can do it. If you are lucky, smaller than a drop will pass into one cylinder and may not be noticed, but it certainly won't be seen as steam out the exhaust.

If it is a Gasoline engine, then that is different again. For every 10ltrs of fuel burn't, produced is 1 ltr of water and 1/10th ltr of sulphuric acid.