tunnel boat

Shark fin skegs mounted well aft and outboard might be a solution. I haven't seen these for sale in a few years, but they used to have them.

 

I've been looking for them all over, no luck

 

This sort of thing ?

http://www.deepblueyachtsupply.com/drivetrain-hardware/ski-boat-fins/ModelNumber/10SKI2

 

Perfect. Thanks

 

I've run a 1860 aluminum PolarKraft flat-bottom tunnel that had ice runners on it. These "ice runners" ran the length of the hull, were about three inches deep and maybe a quarter-inch wide, made of reinforced aluminum. They were basically modified ribs on the bottom of the boat. They were each about 1.5 feet out from the centerline of the boat (so 1.5 feet in from the chines, also).

Pros: The boat tracked straight and true, would practically turn on a dime at 30 knots, would easily throw you out of the boat if you weren't paying attention.

Cons: This boat was used in shallow sandy areas. If you ever stuck the boat on a shallow sandy shoal, the boat was STUCK. With those ice runners buried in the sand, you could not move the boat sideways, only backwards, which limits your options for freeing a stuck boat!

Caveats: 1) This was with an outboard motor (60hp), and 2) the tunnel on this boat was very short, only three feet in length, which lead to other problems which is another topic altogether.

The "ice runners" were a factory option, and I've seen them available from other boat manufacturers as well.

 

That has happened to me and I think I have figured out why. As the boat starts to turn the skegs are in stall condition because of the rapid sideways motion. As the boat starts to straighten out, the skegs start to generate lift and that stops the slide very quickly. So we get thrown sideways by the "body in motion" principle if not paying attention. Very embarrassing and possibly dangerous. Fins don't seem to be nearly as bad in this respect. Possibly because the stall/lift transition takes place over a longer time because of the curved shape of the leading edge of the skeg.

Same thing probably occurs because of the shape of propellers.

 

Ever made a sharp turn at speed in a Shamrock? They have a huge keel (they call them keel drive) and you can definetly go over the side if not paying attention

 

Well, that's the thing with this boat - it NEVER slid! You crank the wheel at 30 knts and the boat turned instantly, with no sliding!

OTOH, the tunnel boat I'm currently running slides quite easily. It has no keel, save for a few structural ribs on the bottom. With the jackplate at full height, about 2-3" of the propeller is below the boat hull, along with the skeg, so the boat slides easily in turns. The great thing about it is that it never comes out of the slide abruptly, so quite manageable. I've slid it many times, and have never had an abrupt stop, or even a tipping feeling, but it does have a narrow hull form (25'x5').