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Seaplane hull design developments

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Himat

Well-Known Member
Joined
May 5, 2011
Messages
2,868
Location
Norway
There have been a lot of talk about that there have been very little development in seaplane hull design later years. And with later years that is later than the 1940’ies. I must confess that I too have expressed this opinion. But as I have studied publications about seaplanes and hull design I do think I must rephrase the statement that there has been very little development in seaplane hull design. I think it is more that the development and progress there have been is little known or not recognized.

If I start with why the progress is not recognised there are several causes. One is that it’s one the large aircraft company flying boat’s most of the development have taken place and been implemented. And of these there have been only a handful developed and produced in some numbers the last fifty years. Then, of those that are more numerous at least in new designs, the amateur built light airplane flying boat a lot have been based on what was known to work in 1945. Another factor is that before we got internet, not much knowledge was public. Not even pictures of those seaplanes produced in numbers, and often nothing about one of prototypes.

There have also been talking about thinking outside the box. Then what box? As I see it, lack of knowledge of what have been done, why what work and the understanding of the physics is the most constraining box. A lot of “new” ideas are maybe not that new, many have been tried before and even found to work.

If we put the baseline at the 1940’ies three designs come to mind. The PBY Catalina, Dornier Do 24 and Short Sunderland. All are examples of the short after body flying boat hull. That is the hull aft of the step is rather short. Apart from the short after body they were not that similar. The Dornier have both a transversal and a longitudinal step, later marks of the Sunderland had a faired step. This is where development often seems to have stalled.

Then, for those that have not been put off by the long rant, some examples where I see that progress have been made.

During the 1940’ies and 1950’ies research showed that longer narrower hulls did perform better. Examples where this knowledge was implemented are the Martin P5M Marlin and Convair P6M Seamaster, both with a pointed step The after body hull now go all the way to the tail. The Canadair Cl215 and Lake Buccaneer also have the long after body, but with straight transversal steps. The later Shin Meiwa PS1 follows these and got effective spray suppression on the forward hull. Last developed of large flying boats are the Beriev A40, Be200. These have again long narrow hulls, now with a dual chine. Compared to the pre world war two designs; spray, hydrodynamic and aerodynamic drag is reduced. There are no longer any problems to get the plane up and planing either, even if better engines also contribute to this.

Another Beriev worth mentioning is the Be103. The “float wing” is not common, but seen before on the Coot amateur built airplane and 1970’ies Equator prototype. What I have not seen on recent seaplane is the step placement ahead of the airplane centre of gravity. It looks like Beriev have made a well function hull with these features.

Last those in development or at the prototype stage. All have been discussed on this forum.

The Centaurus, have a longitudinal step and a narrow hull without a pronounced hump speed. The developers say the hull does not plane, but I think that is down to how you look at it. To me it look more like it have a much more progressive increase in hydrodynamic lift, not a sharp increase like older hulls that get “on the step”.

The Lisa Acoya with a hydrofoil/ski undercarriage. I am not quite sure if it is either or, or part of both. Apart from pure research prototypes such a design has not been tried since the Piaggo P7 racing seaplane.

The Sea Era, a stepped hull design where the hull have got the outline of a lifting body.

The Privateer, a project where Bill Husa, known as Orion on this forum was involved. The step is forward of the airplane centre of gravity and according to pictures and the patent papers part of the forward hull is flat with no deadrise. No great leap forward, but another example that there are different ways to design a seaplane hull and gain benefits from that. Most interesting is that Orion did not follow the guidelines for hull design he published in a short article on this forum.

And with this long post, I have not included any links. On the other side, Google search of this site is in the upper right corner.
 
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