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B&G Vertical Masthead units - how high?

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Does B&G have any reliable data on that? Otherwise you would put a test pole up there with ribbons and observe the airflow. Would be very interesting. If you seek accurate true wind then higher the better, certainly. However the boat is always sailing in an airflow very much altered by the boat itself...ahead, behind and above by several meters. If you only seek steering/trim info then height into undisturbed air may not be so important.

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What size boat, and how tall is the rig?

This chart is from Chicago Marine Electronics, regarding H2000/3000 MHU's.

Product Code

Boat Size

Applicable unit Height

30001 (32") Up to 36' 213 Vertical MHU, 32", 36m cable
30002 (42") 36' - 42' 213 Vertical MHU, 42", 36m cable
30003 (57") 42' - 56' 213 Vertical MHU, 57", 36m cable

We cobbled together a 42" wand with spare parts to make a working unit, and it made a substantial difference. The boat is 40', with a rig about 50' above waterline.

It still over-reads downwind in a blow with an A2. It does bounce quite a bit in chop, so some damping is necessary.

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Upwind I think it would be a factor of upwash caused by the sail plan - in general the more sail below the sensor the larger the effect. Upwash reduces with height and forward position. Downwind the sails are loaded differently so the effect is less clear, but there will be more turbulence. In both cases a square top main would create larger effects. I suspect few sail makers could simulate this as it requires sophisticated software.

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