Maxsurf Resistance Method

Hi All . For an FRP V-shaped hull Fishing vessel (LOA= 27.75m, B= 5.24m) what method is suitable for resistance and power estimates? Is Holtrop ok to use?

 

The attached table outlines the range of application of the method for various types of vessels.

 

Hello all,
I've some inconsistencies in the Maxsurf Resistance Module, someone could indicate me some possibilities to check and fix it?

 

The figure on the left suggests that, among other things, the hull might not be correctly positioned relative to the coordinate system.
Could you share your model?

 

Yes

 

I think you don't need more surfaces than the inner npl-hull and outer npl-hull. You can delete the others. If you want, you could also keep Surface Number 1, but Maxsurf doesn't need it for its calculations.
Once that's done, define the surfaces as symmetrical and move them, for example, 0.7 m transversally.
I think this will improve the calculations considerably.

 

Annoying self-marketing, but try mine tool here Resistance – Prelimina https://prelimina.com/resistance/
It can hand symmetric cats like yours, and it is validated against similar forms

 

Hello,
I'm try to define a simplification hull directly on Modeler, defining different frames by Markers.
However, I can't close properly the bow.
Any suggestion?

 

Thanks so much, I'll try with your tool.

 

Yes, like most of us who use MaxSurf, you create a model in Rhino or AutoCAD (AutoCAD is better than Rhino) and export it to MaxSurf. MaxSurf's modeler is the most unfriendly I've ever seen.

 

That was my first intention, but due to I get some problems when I defined the ref frame, I started to get the points which define the surface and reproduce the hull in the Modeler
My problem is that the values at low speed makes me doubt.

 

You can't use Holtrop nor Savitsky for multihulls.
Your hulls shapes in the first post seemed to be correct. Why did you change them?. Try to simplify them and use with the slender body method.

 

Probably, if you create the model in AutoCAD, with the coordinate system correctly placed, you will not have any problems exporting it to Maxsurf in .igs format.

 

Hi TANSL, hope all is well. I am doing a preliminary design of a ropax double ended ferry and am a bit confused whether holtrop method would be feasible. I am getting confused as i am getting different results when actually hand calculating it andwhen calculating it on MAXSURF. Can not use any of the excel ready made templates since when i leave some things out, as i am analyzing a double ended ferry and things like appendage area are left out it would not compute. Please not that i did not put the model in max surf just put the dimensions.

 

Welcome to the forum.
I'm not entirely sure how Maxsurf can calculate anything if you haven't entered the model, only its dimensions.
On the other hand, I wouldn't trust Maxsurf's results too much because there is some data, necessary for Holtrop's calculations, that Maxsurf doesn't require (the appendices, for example). I'm not saying Maxsurf does it wrong; I'm just saying I don't know how it does it and, therefore, I don't trust it too much.
Holtrop doesn't consider those types of boats, but in any case, given that your boat's stern is more hydrodynamic than a conventional stern, Holtrop's results may be more pessimistic but acceptable for a preliminary estimate.