About inclined boat and chine

This post was done to change ideas and knowings about chine above DWL and heeled boat underwater form, you are invited to comment and think about.

My naval know ever was that chines are prejudicial because it causes vortexes that increase the resistance. But Pikanto reintroduced the chine above waterline principally after, Lintel introduced the total chine and Britpop! maintains this total chine. All successful boats. My curiosity reached the maximum and I done some drawings to try understand what happens and I decided try to put these themes in discussion in this post. The  chine is only effective when the boat is heeled.

Although we are talking about radio controlled model sailboats already have some real sailboats adopting the chine.

1 – Heeled boat underwater form

I do a RG 65 drawing:

FS65 IV

FS65 IV

FS65 IV

I heeled it:

What we see in the heeled hull:

1 – the hull has a distortion to left in the fore part, the hull is curved. The form of fore stations intoduces a distorting in the hull to left. (This is used in Italians gondolas to counter react the force caused by the gondolier that paddles ever in the same side.( If we push a gondola it describes a curved path). Some boats that have a tendency in do a curve trajectory when inclined can have this type of problem.

2 – in function of the large stern the fore and aft alignment of the waterlines is inclined in relation to the old centerline. This will make the boat look like as she is walking cross in the water. Will be the cause for this?

We see on the photo above, that, the heeled hull will navigate cross in relation to the original center line, appearing like Viper Fish. I Think that this do not influence the resistance, is only a appearance question.

However if we have waves they reach the hull crossed, which can stop a little the boat.

——————

And the yawl angle? The hull develops a lateral force against the sail  side force and if we look well, the hull is like a final wing part. How the form of the underwater hull influences the yawl angle? The yawl angle influence the resistance.

We will see now, how we can change the form of underwater part of the hull and see that we can do a (controlled ) infinity of inclined underwater  hull part:

Modifying the two fore stations

I only open the bottom of the two fore stations and the inclined underwater hull part was:

We can improve, opening more the bottom of the three fore stations.

Doing this, the hull fore and aft curvature ameliorate and the angle of the inclined hull in relation to the original center line also.

The Chine:

If the sides of the aft stations is very opened, when heeled, the bow tends to down. The chine permit cut the bottom continuity of this type of section putting the side of the section vertically, ameliorating the problem of the bow down.

But I think that is not only this.

Let’s see this ameliorate hull with a chine. The bottom part of the hull is identical to the boat without chine.

Let’s see it inclined:

What I see here?

A much more appropriate foil to develop a side force to counter react the sail side force.

Well, I tried to introduce here some thoughts on these issues and now I would like to hear some opinions.

I open a thread on the subject on boatdesign.net:

http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/about-inclined-underwater-hull-form-41874.html#post532292

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About Fred Schmidt

Engenheiro Naval interessado em projeto de veleiros radio-controlados. Naval Architect interested in RC sailboats design
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