The Skinny

From the front page of SA-an interesting-shall we say wild- design using and A Class Rig(150 sq.ft) + jib + spin on a very, very narrow hull.

 

what hull Doug??

 

I think the guy scull used a 30-40' rowing "scull". I've written to the guy to find out more.

 

The same boat is posted elsewhere on this forum. A few of have commented on the courage and skill of the builder as well as admiration for the skipper of this "thing".

What in hell is the purpose of such a boat? Is it for purely exhibition purposes? It is certainly not a contender for the go fast trophy. No doubt it would go well in light air but not necessarily better than some far less spectacular appearng boats. In a blow it would be severely beaten by numerous other types: foil moth, 49er, international canoe, and dozens of others. So what is the point? It sure ain't comfort.

 

Skinny

Do you remember what thread it is in?

 

Damn Doug, I was expecting something other than a boat...

That's the cat Richard Woods had a request for !!
You build it when you're too broke for two hulls

 

This is the thread discussing the same "boat"

http://www.boatdesign.net/forums/boat-design/somebody-ask-fast-rowboat-28843.html

 

Thanks, but apparently nobody knows any details-too bad.

 

The rowing shell is strictly a displacement boat and a very well developed one at that. The only reason I picked on it was that it represents one helluva lot of work for a boat whose performance potential must be limited by the fact that is operates in displacement mode only. If it is 30 feet long it might reach a terminal speed of 11 kn or so. The A-cat sail will almost surely yield better performance on the boat for which it was intended. I will wait to learn more about the performance and destiny of this madcap boat. I actually enjoy being wrong about my assumptions because one learns from such things. We'll see.

 

Given the amount of available power, righting moment, prismatic coefficient and low drag, I would not be surprised to see this hull driven far beyond typical hull speed. Looking at International Canoes, one would assume their double ended design may fall into the same displacement mode limits - but it does not. ICs plane, and skinny Moths exceed hull speed as well. 4s and 8s row regularly well above hull speed.

Although my personal impression of the boat is that it would be a misery to sail in average, shifty, light wind conditions (what we get all season), I would not calculate performance potential using standard yardsticks for this one.

--
Bill

 

In the picture on the left, there seems to be no wake at all. As if she is standing still. Is this typical for such a hull form, Does it tell something about the form drag, or is it the picture?
There seems to be a lot of wetted area,despite the non existent beam.

 

There is plenty of wake in the second picture. he is really 'pinching' in the first photo, so not much wake.

The wetted area of rowing sculls is as low was possible with their rounded sections, so that would be optimal.

But, as previously stated, the rounded hull will stop it planing, and thats where most performance boats get their zoom

 

Wave drag on a hull like this is negligible to small throughout its speed range. The killer is eventually wetted surface. At some point, depending on weight and speed, it is faster to get up on the surface and plane. This reduces wetted surface compared with the long slender displacement hull that will have very little tendency to plane.

This video clips gives a good idea of wake from a slender hull at around 8 to 9kts:
http://www.youtube.com/watch?v=UYmODgeN0tU&feature=related

I expect somewhere around 16 to 20kts a planing hull would have less drag for the same displacement as the Skinny given its length.

In rough water its length would give it greater immunity to waves. Have a look at how well the slender amas on the big tris handle waves.

The Skinny could have a useful performance advantage in light winds that are not enough to get a planing hull on the plane.

Rick W