German Powerboats GP 43

[Jeff]

This may be old news to some of the folks here, but I just revisited the German Powerboats site and found the design of thier GP 43 to be quite interesting and refreshingly different from the norm.

The design of the new GP 43 is based on a simple hydrodynamic principle: Smooth surfaces which glide over or are immersed in the water in a horizontal (surf-board- like) fashion, will allow the highest speeds because the load is distributed uniformly across a small surface area. And this is exactly the approach we use: the smaller the area which is wetted by water, the less friction there will be, and the higher the speed to which the boat can be accelerated.

On the other hand, how will these plane surfaces behave when the boat turns a curve or when loads apply at an oblique angle as with the dashing of waves? In conditions such as these, the smoothness of a surface is not enough. Hence we devided the continous surface into a multitude of small surface sections, set off in height and interconnected by vertical sections. The horizontal surface sections are for gliding and will enable the boat to move at high speeds, where as the vertical rigid ones provide "gliding contours" to deal with curves and lateral loads. With this design, major improvements could be achieved: a maximum amount of the energy is available for propulsion and extremely effective lateral traction is ensured. While you may be feeling the accelerating forces in curves very strongly yourself, the boat is still far from swinging or from reaching its maximum loading capacity.

Their website is at http://www.german-powerboats.de/english/english.html or (http://www.german-powerboats.de)

[Jeff]

And here is a picture of the GP 43 from their website - quite interesting I think.

[Willallison]

Judging by the drawings, the boat appears to be little more than a catamaran style hull with an additional, 3rd hull, up front and centre.
Cats have always faced the problem of the wingdeck slamming - especially where the wingdeck isn't far enough off the water. The GP43 appears to have a very low wingdeck, so I'd be somewhat sceptical about the boats rough water performance and durability.
Their website also refers to a marinized Mercedes Benz engine and makes much of its aluminium exhaust system.
Having seen the result of escaping hot, wet exhauust gases on the hull of a 60mtr aluminium commercial cat, I'd have my reservations about that system too.
Having said all that, the GP43 does look nice.....

[Jeff]

I found it interesting for a few reasons, but I also don't know how to evaluate it without seeing it in action.

1.) The folded hull design (with the multiple folds/'steps' running from bow to stern) was new to me. Someone probably has some precedents though ???

2.) I suppose the hull is basically a catamaran, but as you pointed out, the tunnel is not nearly as aggressive as a typical high performance/sport cat. The sponsons/hulls are symmetrical which I wouldn't expect, except for a cruising cat. And while I've seen small center pods like Talon used on their tunnel hulls, I have not seen a center pod this large or this far forward, or for that matter one that also stops this far forward. I would guess that with this major obstruction forward combined with symmetrical hulls and a shallow tunnel, that this would perform quite differently from a conventional catamaran/tunnel hull. A few years ago I remember reading about a couple air entrapment v-hulls which might have evolved in this direction – I’ll have to try and relocate them, but I’m not aware of a close relative to this design.

3.) Just from an aesthetic/styling point of view, it is something unique. I've never liked catamarans which pretend not to be catamarans, like the ones from a few decades ago which had the squared off bow or a curved deck protruding forward of the tunnel - it's just a personal preference, but I've always thought that a catamaran should show off it's real hull shape. This design though I would call a hybrid, because it really does have a pronounced functional forward center hull.