Maxsurf v11 - Can you span a Cat?

[Velsia]

Hi everyone. I am trying to use the Maxsurf v11 package to produce a 17m Catamaran and have come up against problems when producing the polars in Span.

It tells me that the results aren't converging. I understand convergence but have no idea where the difference is lying.

I have used Span before but only with monohulls and haven't yet had this problem.

The manual mentions nothing about not being able to predict catamaran behavior. Has anyone experienced similar? Will Span model a catamaran?

I need help.

[jen2]

Hi Velsia,

the answer is no I'm afraid! Came up with the same problem just over a week ago.

Back to the hand calcs my friend!

[Jenny Giles]

Maxsurf has some very good features and some things like this that drive you crazy.

[Velsia]

Thanks for the advice, back to the textbooks.

[formsys]

The VPP algorithm in Span is based on the published IMS approach. That approach does not cover sailing catamarans.

[Laranjo123]

I have maxsurf v13 ^__^

[Speng]

Doesn't matter whether you have V13 or not Span is an IMS clone. As good as that may be it doesn't do multis. The only commercial VPP I know of that does multis is WinDesign from the Wolfson Unit.

I must say though that if you're doing powering predictions for multis and need resistance that maxsurf's resistance program ( I forget the name) is good for that.

[formsys]

Yes, Hullspeed is the module you are thinking of and the slender body method in it is well suited to catamaran resistance prediction. Info and pretty pictures at
http://www.formsys.com/maxsurf/msproducts/hullspeed

[Speng]

Ya. I really liked it for that. You can go from maxsurf file to resistance curve in 5 minutes. One thing I wasn't sure of is if you could add things like wind resistance etc like you can in the Wolfson powering program. I didn't spend that much time looking at it I just spat out the hydrodynamic drag curve and took it to a spreadsheet where I added the other bits or resistance/drag that I wanted.

[formsys]

Yes, with the regression methods in Hullspeed (not the slender body methods) you can manually modify the settings for things like frontal wind area, transom area, appendage area etc.