Tuesday, December 06, 2016

Wind Scales

Umatilla, FL

I presume that you have all heard of the  Beaufort Wind Scale.  It is a practical scale that allows you to estimate wind speed based on visual clues while at sea.

For example,

We never got used to the Beaufort Scale.  I guess the reason is that we spent most of our sailing time in force 3, 4 and 5 condisions.  Tarwathie's former owner told me a story of being out there in Force 10 with the wife and children on board.  No thank you.  

The highest winds we have seen at sea is force 7 (28-33 knots).  That can be terrible or comfortable depending on the circumstances.  For example, we once sailed from Fort Meyers to Marathon in 30 knot winds.  The whole time we were in the lee of the land, so waves were small.  The angle of the wind on the beam was also just right. We just flew with no discomfort at all.

On the other hand, both Libby and I have become experts at reading the water surface in the range 7-20 knots.  I believe that we can name the wind speed in that range with an accuracy of 2 knots 80% of the time, and with an accuracy of 1 knot 50% of the time.

On Valcour Island, we learned a different scale.  Sitting at anchor in sheltered Sloop Cove, we could hear the wind howling in the tree tops.  I think I can tell wind speed from that sound with 10 knot accuracy.

Now in the RV park, I'm learning a new scale.  The acorn scale.  You see the park is full of live oak trees.  Yes, those big majestic trees, often with spanish moss or other epiphytic plants. Well, live oak trees have acorns, thousand of acorns. RVs have tin or hard glass roofs.  When a acorn hits the roof it makes a sound like a gunshot.  All day and all night we hear those sounds from all over the park.  Each 24 hours, the lots directly under the trees are covered with about 2 freshly fallen acorns per square foot.  Some neighbors sweep them up every day.  We are not directly under at tree, so we don't have that chore.

Most interesting, when a gust of wind comes along an extra quantity of acorns drop.  I'm still working on calibrating my acorn wind speed scale.

1 comment:

  1. Acorn Drop Per minute = Wind Speed?? Just a Thierry.. Very variable though..


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