Anomaly in Transverse Metacentric Height

Hi John
I have detected what appears to be a bug in the computation of KMT.
There may be two problems or they may be different aspects of the same.
When the program encounters a knuckle it produces a negative spike on the KMT curve where one would expect a positive step. The positive step seems to be there too, but often smaller than the spike. The step is permanent as would be expected, but the spike is transient and seems to exist only at one draught. A millimetre higher or lower and it is gone.
The other anomaly occurs when a new appendage is reached by the rising waterline.
What happens here is a large positive spike which seems to have an exponential decay.
I would expect something like this when a large knuckle significantly increases the waterplane area with almost no increase in displaced volume, but this looks a bit more radical than that, and shows up for what should be a very fine entry bow overhang appendage on a catamaran. Clearly the fact that it is on a cat emphasizes the effect on the moments of area.
It does not seem to always happen. The bow overhangs have a spike from KMT of about 10m to about 40m, then within a couple of cm draught this drops back to almost the original value.
Other (stern overhangs) appendages have much smaller spikes.
Unfortunately I can not make any suggestions as to what might be the cause of the problem.

KMT Anomolies

Hi Peter,

Many thanks for the descriptive bug report. Can you email the model to me so I can take a look at it?

Many thanks


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