Pi 28 / Gonet and Cie trimaran foiler

[Doug Lord]

From front page of SA-
Not much more than this is known:
LOA 37'
weight 320kg / 704lb
variation on bi-foiler configuration-ladder type main foil-rudder foil unknown
launch-tentative October

[Corley]

Interesting boat built to an ambitious weight target with a high standard of finish. It will be interesting to see how this stacks up against other high speed multihulls on the swiss lakes.

[Doug Lord]

From SA today: P 28 foiler flying: http://www.youtube.com/watch?v=WalVD...layer_embedded
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From the new website:
"A totally avant-garde boat, the prototype P28 “Gonet & Cie” is a 28 feet (8.53m) foiling monohull, which offers the very latest in major technological advances."

Looks like a tri to me! But their theory may be that the buoyancy pods(amas?) were not designed to be sailed on-only there for backup.......

New: www.p28foiler.com Absolutely beautiful boat with extremely good workmanship! Technical innovations that include telescoping foils-and the rig-similar to one I've seen on a cruiser here somewhere...

click on image:

[P Flados]

The more I have looked, the more I am convinced. Some monos have buoyancy pods on wings. This boat has something similar, but not the same. With the extension fore and aft combined with the hydrodynamic cross sections, not admitting they are designed as hulls (amas) is either a real stretch or just plain wrong. My current take is a tri.

Now for some technical discussion.

The video shows lots of ventilation on the main lifting foil assembly with the upper of the full width foils in and out of the water a lot.

Unless I miss my guess, there is a lot of extra drag with the ventilation. The boat allows for a lot of roll before the outboard amas hit the water. Small planing / foiling surfaces extended below the amas at the rear would aid in roll control and greatly reduce the total amount. Reducing the total amount of roll would keep the lifting foil tips from reaching the surface near as much.

[Doug Lord]

I finally found a sail that, at least superficially, resembles the wingsail on the Pi28. I wonder if Hug(new member) would elaborate on the differences and similarities....

http://www.buildboats.info/Omerwingsail.html

[P Flados]

The use of a soft skin over a variable geometry rigid structure would seem to have a lot of potential.

The middle picture above shows what looks to be a lot simpler internal structure than the PI-28.

From the thread that discussed the PL wing in detail, I remember advice to keep it light, make it self tacking, and make sure that the control scheme will reliably give you the camber you want. I also remember that when Steve implemented twist control is when he made the most recent "leap" in performance.

It looks like to me that we really want light, self tacking and good control for both camber and twist. We also do not want to introduce any new problems such as wrinkles or fluttering.

I wonder how the these soft skin jobs would stack up against a C Class / AC 45 style wing.

[HASYB]

Do you know this one?
http://www.nauticaltrust.com/5203-stratosphere

More on omersail.
http://www.omerwingsail.com/

[P Flados]

I remember reading through the Omer web site a few years ago. It has really been developed as a traditional sail replacement for boats that are not considered high performance, cruisers.

Although I am fond of wings, there are probably better "non-traditional" configurations for the cruisers. A big airfoil main just does not sound like the best answer.

Consider airfoil sheaths over round masts (similar to the Chris White mastfoil) with an A Frame layout on a cat. This would put all of your primary mast loads out where you want them. With two aft stays and only one soft sail (roller furling - up front). The base of the foresail could be attached to a bridle and adjusted side to side if this improves performance. This would be overall very clean both structurally and aerodynamically.

The PI-28 team definitely wants high performance.

The structural demands and the need for shape control are probably much more significant for those shooting for 30+ knots.

Only time will tell if the soft skin over variable geometry structure is practical for either application.

[Doug Lord]

New picture from SA front page:
http://www.p28foiler.com/en/

click on image: Not much main hull clearance when flying-compare to Bradfields Osprey in 2nd pix....

[HASYB]

Hi doug,

I suppose main hull clearance has something to do with the fact that the boat is just (again) in the water and they take it easy. Picture shows little wind as well.
In the end of the first video you posted of Pi28 you can see her "climb the ladder".
On the site I read:

Manoeuvrable and high performance in flight and floatation mode

The π -shaped foil is comprised of a beam supported at two points. This arrangement reduces the stresses that put pressure on the right angles, the latter being the weak points in carbon structures. It also enables the surface of the foils to be extended, thus optimising their performance.
The technology involved in foils with several lift surfaces facilities the vessel’s ability to power up and take off in light airs and provides less drag once the boat is in ‘flight mode’.

The benefits are as follows:
Eased elevation at low speed
Easier manœuvring
Developed potential for speed