Anyone made their own omnidirectional wind scoop?

[tudorsailor]

Been looking at Windscoops. Best seems to be the 4 sided ones that allow wind in from any angle. £70 from Plastimo seems a lot.
Has anyone made their own and can share dimensions?
Does the scoop have to be pointy at the top? Why not four equal sides with the top and bottom both square? This would mean having a frame at the top end to keep the square shape.

TudorSailor

 

[sarabande]

after a number of years in the summer heat of Dubai and SHarjah, I can vouch for the efficiency of the traditional wind tower.

Go down about halfway to see the landbased construction details, and lower to see the computer-generated windflow patterns.

http://architecturalmoleskine.blogspot.co.uk/2010/01/other-side-of-dubai-wind-towers.html

The shape from above is a right-angled X, and the windward side funnels the fresh downwards, and the leeward side sucks the old air upwards. I'd put a flat cloth across the top to create an end-plate effect.

They would be very very simple to make to fit above a hatch, suspended from directly overhead. Perhaps best to have one right upwind, and one downwind to get a really good through-boat flow.

 

[duncan99210]

Lalizas also make a four way scoop. Flat top with two dowels at the top and two at the bottom to give rigidity. The top has a loop to take a halyard, the dowels at the bottom are slightly longer than the top so as to engage the underside of the hatch. Height is about 1.5 metres. Made out of rip stop nylon. You could make it shorter if required to say fit a saloon hatch where the boom is too low for the longer scoop.
For use on the forward hatch, we've found that two lines are useful in getting the position of the top in the right place: the spinnaker halyard plus a bit of mousing line taken to the roller genoa to pull the top scoop forward to the vertical.

 

[Roberto]

for some reason photobucket will not turn the picture, sorry...

Anyway, this is mine; initially I put the square vertical cloth you see near the deck as I saw the original model had one, later I took it off and the windscoop worked a lot better.
Under the deck, there are four slack lines keeping the four corners, keeping them slack allows the windscoop to modify its shape and adjust better to a change in wind direction

 

[GHA]

Is a 4 way one anywhere as good as a single one? Might be worth getting 2, one of each. At anchor is where they come into their own, IMHO, never so much wind in marinas and at anchor you're head to wind. In the warm places anyway

 

[wklein]

I was looking at making my own one I have a round hatch so should be able to use two hoops. I'll report back if I get around to it.

 

[Contest1]

Bought an odd looking sunbrella that clamps to a child's buggy. Works great on my forward hatch lying to the wind!

 

[vyv_cox]

It always seems to me that wind flows from high pressure to low pressure areas of the boat. At anchor, with head to wind, this is very obviously from the forehatch to the cockpit. Assuming the boat was in a port with the stern into the wind the high pressure area is the cockpit, with the spray hood perhaps acting as a scoop, and wind exits the forehatch. I have occasionally found a scoop facing aft on the central hatch to be useful, although only a little. I cannot see how a four-sided scoop on the forehatch could possibly be useful in these circumstances. In cross winds there might be some benefit for occupants of the forecabin but doubtful that any draught could penetrate further into the boat.

By far the best arrangement I have seen was made by a friend. His forehatch scoop pivots on an arrangement that allows it to rotate through 360 degrees. It always faces the wind and directs it into the forecabin.

 

[charles_reed]

It always seems to me that wind flows from high pressure to low pressure areas of the boat. At anchor, with head to wind, this is very obviously from the forehatch to the cockpit. Assuming the boat was in a port with the stern into the wind the high pressure area is the cockpit, with the spray hood perhaps acting as a scoop, and wind exits the forehatch. I have occasionally found a scoop facing aft on the central hatch to be useful, although only a little. I cannot see how a four-sided scoop on the forehatch could possibly be useful in these circumstances. In cross winds there might be some benefit for occupants of the forecabin but doubtful that any draught could penetrate further into the boat.

By far the best arrangement I have seen was made by a friend. His forehatch scoop pivots on an arrangement that allows it to rotate through 360 degrees. It always faces the wind and directs it into the forecabin.

I suspect the OP is considering trying to use a windscoop when tied up, either in port or marina. I've found the wind directions and velocities under port conditions to be so light and variable that the occasions that you can rig any windscoop are few and far between.
At anchor, my 21-year old windscoop works OK, at times making the boat too chilly in 38C with a Bf 3-4. That cost me FF 25, and the only problem is that the shock-cord holding it on the hatch-lip lets go too easily and needs frequent renewal.
So essentially I agree with Vyv - an omnidirectional windscoop probably doesn't exist - perhaps a big computer fan is a more certain solution to the OP's dilemma.