H3000 calibration problem
40' IRC boat running B&G H3000, 1.5m wand, paddle wheel BSP
(Calibration adjustments available only MHU offset, TWS table - no heel, etc)
We have a significant discrepancy between AWA and TWA tack to tack that is very difficult to correct.
We have calibrated BSP, SOG and compass using the onboard routines. Damping set on all parameters at 3.
With the boat in the pen, AWA and TWA are within 1deg (but don't seem to change if I change the MHU offset - averaged over 30mins, so taking the damping out of consideration - at least the change isn't consistent?)
On the breeze, the tack to tack AWA (with everything meticulously repeated tack to tack) is quite different by say >10Ddeg) and the TWA is about right (~42deg) on STB tack and way off on PRT tack (~20deg). This doesn't seem to be much difference from flat water or lumpy from 10knots TWS up to 20knots.
Changing the MHU offset doesn't bring this any closer. Even if I adjust the TWS table it doesn't really have much effect - but certainly not a consistent effect on TWA/AWA.
I have tried almost everything but cant seem to make any consistent difference.
The one thing that maybe an issue is that the wand is not vertical - maybe 1 - 2deg off? Would that have such an effect?
Need some advice from the community please about where I should look for answers.
Many thanks - turned out that the MHU was -10deg off centre (how it came?). This became obvious by trying to get AWA the same tack to tack. Once that was sorted, then everything started to fall into place. So if anyone else is going down this road, my expereince has been do the following in sequence:
AWA same tack to tack by adjusting MHU offset
On the wind, adjust the TWA table to get the TWA narrower or wider (we started off with actual being about 45deg and needed to be about 42deg so more negative in that wind range and just keep doing this for other wind ranges). Started with the recommended table from the manual (40' sloop)
TWS adjustment at different TWA's (on the wind, reaching and running) by bearing away and holding at 90deg TWA, then 135deg TWA and adjusting the TWS table to make TWS the same on each point of sailing.
Now TWA and TWS are pretty good (+-1deg) and so laylines, sail selection and targets then strat to become more accurate and so the search continues . . .
Once we got this done over a few sails, everything started to click and we were able to concentrate on damping and fine tune of the tables for sea state.