"Stack effect" in raggie mast

[sarabande]

"Stack Effect" in a raggie mast.

Kerfuffling around near the heel of my keel-mounted mast on a sunny day, I heard a faint sussuration. On more investigation, I could hear the sound of birds from a couple of holes in the mast near the cabin sole. And a palpable draught of air zipping up the inside of the mast.

Generally my boat seems fresh and dry, even when I have been away for a couple of weeks. Do some masts always act as air extract vents, or it is an intermittent phenomenon relying on sunshine, angle of wind and whether there is an R in the month ?

 

[rogerthebodger]

Re: "Stack Effect" in a raggie mast.

Kerfuffling around near the heel of my keel-mounted mast on a sunny day, I heard a faint sussuration. On more investigation, I could hear the sound of birds from a couple of holes in the mast near the cabin sole. And a palpable draught of air zipping up the inside of the mast.

Generally my boat seems fresh and dry, even when I have been away for a couple of weeks. Do some masts always act as air extract vents, or it is an intermittent phenomenon relying on sunshine, angle of wind and whether there is an R in the month ?

Just think that hot air rises and the air temperature inside a boat can and will be a few degrees warmer than the outside so warm air in the bottom of the mast will rise drawing cooler air in from outside in the same way a a power station cooling towers work.

The towers on old middle easton houses work the same way.

Air blowing past your mast can also act as a woodwind musical instrument and resonate inside the cabin. This happens even with my deck stepped mast.

 

[Kelpie]

Re: "Stack Effect" in a raggie mast.

The Albin Vega was designed to take advantage of this effect as a sort of passive air conditioning. Air was ducted along the inside of the hull, to benefit from the cooling effect of the water, and then extracted via a vent at the mast foot, with the hotter mast acting as a chimney. It supposedly worked quite well although I didn't really get much of a chance to need it seeing as I sailed mine in Scotland...

 

[johnalison]

Re: "Stack Effect" in a raggie mast.

What a wonderful word, sussuration. I must try and use it some time.

 

[lw395]

Re: "Stack Effect" in a raggie mast.

So, your mast is not sealed at deck level?
I've had a mast like that, it was amazing how much rain came in!

 

[earlybird]

Re: "Stack Effect" in a raggie mast.

IIRC, this effect is enhanced by placing an inverted plant-pot over a lit tea-light.

 

[Aja]

Re: "Stack Effect" in a raggie mast.

So, your mast is not sealed at deck level?
I've had a mast like that, it was amazing how much rain came in!

Only properly sealed keel stepped masts I've seen were solid wooden masts. Alloy masts are notoriously difficult to seal due to the extrusion having an track indent.
Donald

 

[Lucky Duck]

Re: "Stack Effect" in a raggie mast.

Kerfuffling around near the heel of my keel-mounted mast on a sunny day, I heard a faint sussuration. On more investigation, I could hear the sound of birds from a couple of holes in the mast near the cabin sole. And a palpable draught of air zipping up the inside of the mast.

Generally my boat seems fresh and dry, even when I have been away for a couple of weeks. Do some masts always act as air extract vents, or it is an intermittent phenomenon relying on sunshine, angle of wind and whether there is an R in the month ?

:Test for spam

 

[sarabande]

At the base of the mast

 

[Robert Wilson]

At the base of the mast

Am I missing something here?
Sorry, the whole thread, bar the title was missing when I opened it.

Susurration! Sounds like a terrorist infiltration of the C.I.D!

 

[sarabande]

I was in the middle of a reply and fumbled some key combination by mistake. Posting about using incense to test air currents at the base of the mast.


I think I have been expurgated