How to close a parametric sailing yacht hull with a smooth round bow?

[Mr. Gustaf Magnander 0]

  Hi all,

 

I need help with closing the parametric sailing yacht hull explained in the tutorial but not with a sharp bow as in the totorial, but with a smooth round bow with a rather large radius at the deck level that decreases vertically, towards the watersurface and the keel.

 

Does anyone know how to do this?
 

I would really appriciate help with this issue, since I´ve spent so many hours trying to close the hull with a round bow, but without success. 

 

Thank you very much in advance!

 

Best regards,

Gustaf Magnander 

 

[Mr. Claus Abt 14]

Hi Gustaf,

in https://www.caeses.com/forum/index.php?/topic/341-modelling-yacht-with-radius-stem-using-ksplines/ I showed a generic method. That works for the parametric bow as well, you may have to define the surface curve slightly differently, maybe in u-v-space to get a nice lower part.

 

Cheers

Claus

[Mr. Kevin Cudby 0]

Hi Gustaf

There are several ways to achieve a "round" bow.

If you use kspline sections you can put the datum plane at some arbitrary height above the waterline.

This is suitable for a plumb stem, as on the mini keelboat featured on kspline.com.

You can develop such a model by modifying the kspline skiff model (see Claus's link) - you just need to add a curved surface to the bow.

Another approach is to curve the datum. I often do this, becausae it makes it easier to maintain a nearly constant static displacement across a range of different hulls. The datum must be a smooth curve.

If you need a raked stem thaty has a straight profile, you can rake the sections.

if you want a spoon bow, like on a tornado catamaran, flying fifteen, or dragon you can lift the datum right above the deck. This means you can sweep the sections all the way along smooth curves all lthe way to the bow.

I recommend that you break the hull surfaces into sections. Anywhere the longitudinal curves have sudden transitions, it is a good idea to break the metasurface. So if you have a hull bottom curve that consists of a long, sweeping bottom, with a tightly curved forefoot, I would have one metasurface for the long sweeping part, and another for the forefoot.

I also used this technique on the mini-keeler hull on the front page of kspline.com

[Mr. Gustaf Magnander 0]

Hi Claus and Kevin,

Thank you both very much for your advices and that you took time to help me. I have actually never used ksplines before so I will learn how to use them now.

Kevin, I have to say that I do not really understand what you mean when you ”curve the datum”. I have also used the approach to build the hull out of several surfaces, like one for the bottom and one for the chine etc.

Nice to make your acquaintance!

Best regards,

Gustaf