STW and SOG Errors
Posted: Sun Oct 13, 2024 8:34 am
This is my first time posting here, but I've already learnt a lot from reading many of the other helpful posts and answers.
I've been having a problem with getting accurate STW and SOG. Here is the scenario:
Heading due north with no wind and no current. The maximum STW achieved at full throttle is 16 knots. As you would expect, STW and SOG are the same at this point.
I add 4 knots of current from 000 and after everything settles down again, STW is now 17 knots. SOG is shown as 13 knots, which is correct in relation to an STW of 17 knots, but the STW shouldn't have changed in the first place.
I then change the direction of the current so that it's coming from 180. I wait for everything to settle down, but now the STW has dropped to 15 knots with a SOG of 11 knots. This time, the boat has lost 1 knot through the water!
I've tried this with multiple boats at multiple speeds. The errors get bigger or smaller depending on the amount of current being used and the length of the hull, but there are always errors. The only time at which there is no error is if the boat isn't making way. Then, she drifts at the same speed and direction of the current.
Has anyone else had this problem, and is there a fix?
Thank you.
I've been having a problem with getting accurate STW and SOG. Here is the scenario:
Heading due north with no wind and no current. The maximum STW achieved at full throttle is 16 knots. As you would expect, STW and SOG are the same at this point.
I add 4 knots of current from 000 and after everything settles down again, STW is now 17 knots. SOG is shown as 13 knots, which is correct in relation to an STW of 17 knots, but the STW shouldn't have changed in the first place.
I then change the direction of the current so that it's coming from 180. I wait for everything to settle down, but now the STW has dropped to 15 knots with a SOG of 11 knots. This time, the boat has lost 1 knot through the water!
I've tried this with multiple boats at multiple speeds. The errors get bigger or smaller depending on the amount of current being used and the length of the hull, but there are always errors. The only time at which there is no error is if the boat isn't making way. Then, she drifts at the same speed and direction of the current.
Has anyone else had this problem, and is there a fix?
Thank you.