eclipsemullet

B&G H5000 Heel Correction

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Would you guys expect a 40' race boat's BSP to over-read when heeled at 20 degrees?  (First 40, paddlewheel is on the centreline, fo'ward of the keel).

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It's very hull-shape dependent and more pronounced on "triangular" boats, those with fine entries and big wide transoms. As the forms heel, there's a pressure differential in the water across the boat and the water squirts across. BSP correction tables are the solution.

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You have heard the guys that know, but generally yes.  However, have you also separated the BSP over-read component?  At 20 degrees heel I'll bet you are exceeding your paddlewheel BSP calibration benchmark.

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On 7/17/2019 at 9:40 PM, eclipsemullet said:

Any idea of numbers?

I use an ultrasonic speedo which is very lineair accross a wide range of BSP.

However, when heeled I apply a correction up to -3%.  This is on a J/111

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Heel correction for a symmetrical hull can be set value however for boats that have a flatter hull with almost vertical chine it isn't as simple such as a Class 40, thus there needs to be correction values based on boat heel which look like this:

  Heel         Boat Speed Calibration:

  -40.0       0.960
  -25.0       0.980
  -10.0       0.990
    0.0        1.000
   10.0       0.990
   25.0       0.980
   40.0        0.960
 

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On 7/25/2019 at 4:40 AM, ZeeZee said:

I use an ultrasonic speedo which is very lineair accross a wide range of BSP.

However, when heeled I apply a correction up to -3%.  This is on a J/111

I've generally heard negative things about the ultrasonic sensors. Are you happy with yours? What model is it?

I would love to get rid of the paddlewheel. I have to pull it out every time I get off the boat or it'll be fouled with small critters within a day two.

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On 7/30/2019 at 4:08 PM, squiby said:

I've generally heard negative things about the ultrasonic sensors. Are you happy with yours? What model is it?

I would love to get rid of the paddlewheel. I have to pull it out every time I get off the boat or it'll be fouled with small critters within a day two.

When we had our H5000 installed, they advised against an ultrasonic sensor because the calibration goes wonky as the water salinity changes.

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4 hours ago, eclipsemullet said:

When we had our H5000 installed, they advised against an ultrasonic sensor because the calibration goes wonky as the water salinity changes.

Can confirm on the calibration, but it's not a large difference 5% or so between fresh and salt water,  1% or so in salinity of salt water and 2%-4% in brackish water. 

The earlier Airmar Ultrasonic speedo's did not like no flow or backwards flow of water across them to the point where they would result in errors being displayed instead of 0. Also if the ultrasonic was to far forward the displayed speeds would get really wonky when the flow of water was disrupted by air. The only way to tell though would be to see what the LED was blinking. Generally solid green or 3 green blinks is good, its not so good when it's blinking red or solid red. The worst is when it's alternating between red and green, that means it's failed. 

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