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Board » General Discussion » Boat planning.

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Posted by
Rod


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2010-06-24 22:30:48
2014-04-07 17:30:41 - Re: Boat planning.
I'm in general agreement with your statements about Footy design. The British trend is towards very high bows to counteract Nose-dancing.
I have been following a different approach involving a narrow bow at the waterline, swelling to a much greater volume as the bow is pressed down.
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
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Posted by
JB


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2014-04-08 09:22:59 - Re: Boat planning.
Wow Rod, very nice boat (“Glass Petrel II”).
And above all, very different from the Harpy design, from which I’ve made my overall thoughts about the Footy design, more precisely, the Harpy model.

Looking to your boat pictures two aspects immediately caught my attention:

1 - the high aspect keel with a bulb end, very refined indeed, and;
2 - the enormous rudder, “door” shape alike and, to my mind, totally out of scale.

In theory a rudder with such a large cross section induces more drag than a rudder using a higher aspect ratio, with/without a NACA cross section profile.
Higher drag on the rudder translates to superior forces induced to the helm, obviously influencing the boat behavior.
I wonder if part of the boat’s “nose dancing” instability doesn’t come precisely from having that huge rudder cross section.
If you’re already using a sophisticated keel why don’t you try to some change on the rudder?

At we were talking about the VOR70 I can’t resist to bring up this links:

- stockmaritime.com VO70
- youtube: RC VO65 with genaker (stockmaritime)

And also some planing on the waves:

- youtube: RC VO65 surfing waves (stockmaritime)


___
Edited links to fit column width

--- Last Edited by prokkyer at 2014-04-08 10:32:39 ---
Sail Fair.
Posted by
Rod


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2014-04-08 20:56:07 - Re: Boat planning.
Agree that the rudder is too large, but the model has proved difficult to tack. It is also restricted by the Box Rule for the Footy class, where the rudder must fit through a slot of limited depth.
I will try this summer to reduce the rudder size, while still needing to tack smartly. With such a small light hull, the momentum is small, and stalling during a tack is a continuing problem.
The info on the tilting keel models was interesting--unfortunately, class racing allows only two controlled channels. It may be possible to "automate" a swinging keel and a reefable gennacker, which would be interesting, but I doubt if a strict interpretation of class rules would allow them.
Some early radio-controlled sailboats had just a single channel for steering, with the sails controlled automatically by a wind vane at the masthead. This would leave a control channel available for the furlable gennacker, or for the swinging keel
I have contemplated the possibility of a mast-keel-fin unit pivotting in a boat hull which would remain level. Suitable gearing might allow the keel fin to move through a much greater angle than the heel of the mast.....?

--- Last Edited by Rod at 2014-04-08 20:58:12 ---
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
JB


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2014-04-09 19:08:26 - Re: Boat planning.
Viva Rod.

Talking about the Footy rudder I was thinking in something more like the one seen in the attached picture, positioned before reaching the stern or after it as you have in “Glass Petrel II”.
Anyhow, the idea was a rudder with a higher aspect ratio and, obviously, less drag effects.

Other aspect that intrigues me Rod, is why the front and, I suppose, also the aft sections, aren't more “vertical”, in order to increase the water line length?
Sail Fair.
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Posted by
JB


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2014-04-10 13:29:42 - Re: Boat planning.
By the way,

Sometime ago I tried to track a boat I’ve sailed for years owned by a great friend of mine.
She was the J8 “Finola”, a 1930 William Fiffe design and built by William Fife & Son, Fairlie (fintra.de Yachten von William Fife).

Part of her story goes here: britishyachtingarchive.org.uk Finola

During that search I’ve found a scale model of her. Rod, what a beauty! (rcsailing.net Finola 8 metre of Fife).

__
edited links



--- Last Edited by prokkyer at 2014-04-10 14:48:38 ---
Sail Fair.
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