Originally Posted by Jake
Originally Posted by Timbo
Originally Posted by catman
Originally Posted by Timbo
Here's a question for you designer wannabe's.

As we have been seeing ever since Foiling became a 'Thing', the worst thing that can happen is the dreaded nose-over, pitch pole. As I look at all the foiling boats, from the Phantom all the way up to that 70' Tri above, they all have the main lifting foils mounted at about mid hull, with a T rudder setup in the back. From watching many of these videos, it seams they always start to hobby horse in any type of big swell, and the bows dig in once in a while, often with disastrous results!

Why aren't they putting the main lifting foils further forward, instead of only at amidships? If the would put it way out front, that would stop the teeter-totter effect we see in the swells.

They could make the rear foils bigger and the front foils smaller, to evenly distribute the weight, but it seems to me it would be much more stable if they spread the foil lift to all 4 corners, rather than keeping it right in the middle of the boat and having the nose dive tendencies.


Why are plane wings positioned where they are? Balance? The other thing to consider is how would it handle/steer with the foils forward. Very slow I think.


Well, that's the problem. They have to design something that's going to 'work' in at least 3 axis', then throw in differing sea state, wind speeds, etc, every design is a compromise trying best to fulfill all those requirements. I'm sure they have lots of smart guys from Boeing and Airbus on staff telling them exactly what/where those foils should be, but I'd still like to see what would happen if they put them further forward, and then did a 'shared lift' concept with larger foils on the rudders.

That may indeed slow down the turning required from the rudders though, maybe that's why we see such small foils back there, with most of the heavy lifting being done by the big L boards in the middle of the boat.

Now, let's think about our A cats, and all the teeter-tottering they do when up on the foils. Have any of them tried moving their big C boards further forward to see if that helps keep them from doing a face plant?


https://www.youtube.com/watch?v=n0gXbhjUDtA


they actually started that way. The problem was (didn't we have this conversation before?) that with the shared lift of the main and secondary foils, the boat was very unstable when transitioning from displacement mode to foiling mode. At some point in that transition, the boat needs to pitch up in order to get to an elevated foiling position. With forward mounted foils and rudders lifting (and no allowed trim tabs on any of the foils), the boat tended to porpoise badly and was very difficult to control. It was only until they brought the foils back closer to the center of mass of the boat that they were able to achieve a stable transition from displacement to foiling....which is the same reason airplanes have a primary lifting wing close to the CG of the aircraft.

Think of the rudder foils serving to provide stability, not so much lift. Similar to the horizontal stabilizer on a plane.


Philip
USA #1006