Thread: Paradox Micro Cruisers and "Bilge Runners"

Yap ...

Still a problem with the separation of the effects. Most traditional boats are "lifting bodies too", or a NA would probably talk about salient lateral area.

You need that lateral plane one way or another. I still find it hard to believe that a little lip can make so much difference and still suspect that if it wasn't there it would make little difference.

It does mean that the method only really works for heavy boats.

Norfolk Wherries - had no visible keel but had to sail upwind up rivers .. they were well regarded as upwind boats.


Plank on edge cutters, pilot cutters. Also why you factor in the hull depth when you calculate the Centre of effort of heavier boats. No lip to be seen.

Best wishes
MIK

As some of you know I am staying with Chuck and Sandra of Duckworks in Texas.

I was having a look through some back issues of Small Craft Adviser and found an interview with Matt Leyden.

(ha ... just realised that AJ's link above was to the same article)

I wanted to add some to this thread.

He says the bilge runners are the most obvious and also the least important part of his system. What I read makes lots of sense.

1/ It is suitable for boats that are quite deeply laden - heavy for their length. A large part of the lateral resistance is from the depth of the hull. It won't work with shallow, lightly laden vessels. Think very tradtitional boats before the keel became an appendage and garboards became hollow.

2/ The mast and sail are set well aft and the rudder is large. This means that the boat will have an amount of weather helm that will be corrected by the rudder at all times. This means the rudder which is large and deep will be at a greater angle of attack and provide a large part of the lateral resistance. Hobie cats do this too (the ones without centreboards) the more you rake the rig aft, the more load is carried by the rudders which are much more efficient at carrying side load than the hull.


3/ the chine runner is the least important component and won't work independently of the other two. It is an attempt to reduce the crossflow slightly and increase the effectiveness of having a deep hull in the water. In a couple of the photos one of his more rounded hullshapes seems to have the chine runner at a slight angle to the way the water would naturally run over the hull. I think you would have to be very careful how you used this and Matt has chosen quite a small angle (I think).

Best wishes

MIK

These are pretty much the same conclusions you and I came up with, when this thread was active Michael. See, we're not as dumb, as our women attempt to convince us of.