Expedition Navigation Software » Basic stability for meaningful "test"

sheldon.haynie · 7/21/2016 11:11 am

Raced last night on the Oakland Estuary, and am learning a lot by reviewing log files.
One major learning is that my measured AWA is about 20 degrees worse than my polars suggest it should be.
As we were strapped in, pointing reasonably well with a few other boats, I doubt I was really at 48 AWA and 78 TWA in 6-10 kts. As we have not applied any corrections yet, that's an indicated action for next outing.

Question:
the TWD that was calculated had a sigma of 10 degrees across 10 minutes, with 3 distinct gradual left hand (lift) shifts and 3 abrupt resets.

If I filter the log file offline for ROT < 1.1 degree/sec and BSP%> 90 I can take out the abrupt resets, but in a stripchart I don't know if/how to do that.

Is this just too much oscillation "noise" to bother with creating a test?

Last edited by sheldon.haynie (7/21/2016 11:14 am)

DuncanR · 7/21/2016 10:20 pm

Sheldon
I'd cherrypick this lot for individual 1 minute samples, omitting the gross changes and work on those as a set. However, if what you are trying to do calibrate AWA and TWA tack to tack, as I suspect you are, go for a sail - not racing - and do 6 or 8 tacks as similar as possible, racing mode - not pinching - and compare the P and S "tack pairs"values against each other.
I suspect from what I read of your posts you are a river rat, so open water and clean tacks might be a challenge ... but to do this OK, get offshore.

sheldon.haynie · 7/22/2016 9:39 am

Duncan, we have the SFBay just a mile and a half away to the west, but we race our beercans on the Estuary, hence the "riverine" aspects of some of my usage. To date, have not put in the "evaluation" time as its either been racing or family "fun" sailing and neither of those is suited to repetitive assessments.

I can subdivide log into smaller chunks, but given that my SA/Disp is about 12, we do take a while to accelerate and I will have to look at if I am at stable speed/angle in that shorter period, Perhaps at the end of each tack a smaller sample would be good.

I plan to get out this weekend and do some calibration/mast tuning/trim tuning, letting the AP hold a wind angle to see if I have offsets while I get the mast/sails tuned up.I've been fighting some battery and paddlewheel issues, that are hopefully resolved and that should clean up some of the BSP--> TW* questions.

My polars tell me I should be hitting 30 AWA and better at higher TWS, I am seeing instrument readings that are substantially larger as above, while pointing nearly as high as the fin keel boats and making the polar/target speeds. Not sure quite how to address but will be looking at the H5000 webserver help files to see if there's calibration of the angle magnitude.

S

Last edited by sheldon.haynie (7/22/2016 9:41 am)

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7/21/2016 11:11 am #1

Basic stability for meaningful "test"

7/21/2016 10:20 pm #2

Re: Basic stability for meaningful "test"

7/22/2016 9:39 am #3

Re: Basic stability for meaningful "test"

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