Heeled Hull Form II

Let’s see Riptide:

Riptide 10 degrees helled

Riptide 30 degrees

Riptide wl 35 degrees

Although we see that the  Riptide 10 degrees waterlines are in the form of foil, the foil is in the opposite direction it should be, the low pressure side is on the wind side generating a force downwind.
As the shell heel, 30, 35 degrees, the foil is being formed on the right side, ie with low pressure side of the wind, generating a force against the wind.
Based on this I would say that the stronger the wind would be the best boat performance. I’ll ask Earl Boebert if this is correct. Earl was the one who sent me the design of the Riptide.

Earl Boebert replied to me today (03/20/2012 – 15:26):

Originally Posted by fredschmidt View Post
EarlI am supposing that the Riptide performance was better in winds with more velocity than lighter winds. Am I correct?
Yes, one of the greatest heavy air boats of its era. When hit by a gust, it just leaps out of the water and goes. Eric Sponberg has posted an explanation for this in several places — it has to do with the narrow stern (which also accounts for the balance of the hull — it doesn’t yaw when it heels.)Cheers,Earl


Now we have another explanation than that of Mr Sponberg

The rapid change in board side of low and high pressure may justify also leaps out of the water and the good efficiency in greatest heavy air can be explained with the adequate waterline forms at great angles of heel.


I remember that the angle of attack must be better with adequate waterlines foil form.

Another thing to note is that the side of the Riptide is pretty straight and vertical, like a chine, which facilitates in larger angles of heel the proper formation of waterlines in appropriate form of foil.

Thinking about this subject I would venture to say:

1 – The chine improves the shape of the waterlines  by placing the low pressure side from where the wind came. Both port and starboard.
2 – It also improves the angle of attack
3 – We must be careful when designing the hull, study it tilted so as to obtain good waterlines in the form of foil
4- There should be a better form of foil to the water lines.

Of course the boat design should continue to take into account:
1 – weight
2 – prismatic coefficient
3 – wet surface
4 – entrance angle

5 – LCB and LCF positions in all angles of heel referred to 0 degrees.

The set of all these factors chosen properly, will lead to the best boat.

I believe that the assumptions above, based on good sense, take the boat design more efficient.

Ideal would be to develop a research on the subject. For my part I will use them in my RC sailboats, and I will continue my studies on the subject.

A good contribution to the subject is to confirm this theory with whom designed good RC sailboats as  Britpop!, Pikanto, Cheinz, Lintel, etc..


About Fred Schmidt

Engenheiro Naval interessado em projeto de veleiros radio-controlados. Naval Architect interested in RC sailboats design
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2 Responses to Heeled Hull Form II

  1. Great stuff Fred

    I follow your research with great interest!


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