New VPP

I have developed a new VPP that uses numerical modeling. It can be downloaded here:
Velocity Prediction Program UliSpeed https://www.remmlinger.com/UliSpeed.html
Details are described in the user's manual.
Have fun
Uli

 

Impressive work indeed, added to your previous ones, you really addressed all the complexity of a sailboat. To also input a sea state is challenging because the consequences are numerous and complex to assess, for the extra drag as for sails efficiency drop when the pitch motion are no longer negligeable.

 

Thank you, Jean-Francois, for your interest in my work! The influence of the sea state, like you describe it, is indeed extremely difficult to assess. I used the simplified version of the latest Delft-coefficients, that you discussed some time ago in a thread. It is better than nothing .

 

excuse me, can I use your program for catamarans?

 

Sorry, no, it can not simulate catamarans. Maybe I can find the time in the future to adapt the program for catamarans.
Thanks for your interest
Uli

 

There is a new update, which can be downloaded at Velocity Prediction Program UliSpeed https://www.remmlinger.com/UliSpeed.html
The update contains several bug-fixes and new features. The program can handle now ballast bulbs, twin rudders, and arbitrary longitudinal trim by shifting weights.

 

ok, but it's still a good program

 

I did a tentative VPP for a sailing catamaran, here below. Not very difficult actually, you just have to consider two hulls windward and leeward functioning at different sinkage and Froude (the windward hull having a shorter waterline length than the leeward length). The core issue is the extra drag due to the waves interaction between these two hulls, but the more the wind and the heel angle, the less the windward hull trace in the water, so the less the expected interaction with the leeward hull. A rough estimation of this interaction drag based on available model tests (Molland and al. experiences) can be judged valid enough to take into account its influence on the total drag. It is also quite easy to continue the computation up to the windward hull out of the water. I am sure that Uli can develop a more complete tool in line with his exhaustive development on the subject.
Gene-Hull Catamaran 3.0 and SA-VPP catamaran 1.0 | Boat Design Net
(PDF) Resistance experiments on a systematic series of high speed displacement monohull and catamaran forms in shallow water (researchgate.net)

 

Concerning Catamarans

Leo Lazauskas used thin ship theory to calculate the interference between the two hulls of a catamaran:
Michlet 9.33 Released https://www.boatdesign.net/threads/michlet-9-33-released.52865/
Unfortunately he lost interest in ship design and his website is down.
The resistance of the catamaran hull Delft 372 is predicted with Michlet quite well for Froude-number > 0.35

 

New update!

The update UliSpeed_2.7 is available on my website: Velocity Prediction Program UliSpeed https://www.remmlinger.com/UliSpeed.html
After you have finished the optimization, the program will write now scripting files that can be read by the CAD-programs RHINO or DELFTship. The CAD-program will automatically create 3D-surfaces of the flying shapes of the sails. No other VPP provides such a level of detail about the shape and trim of the sails. Attached are screenshots of the Pogo 40 S2 at a true wind angle of 40° and a wind speed of 16 knots. The CAD-Program is Rhino5. The lines on the sails are sections in the direction of the streamlines.