Hull shapes for Water Plane

Hi Everybody,

I intend to design a cargo aircraft for take off and landing on water.

There are classic shapes for the hulls and floats of such vessels, which have not changed much since the 1930ies. Unfortunately these shapes create a lot of drag when airbourne.

There are also ground-effect crafts that function like ram-air hovercrafts. But these are only suitable for calm waters. This limited their commercial use.

I would like to design the craft for rougher waters, hopefully for seastate 5 or 6. This would allow cargo operations on 80% to 90% of the days on most oceans.

Do you have experience with powerboat or hydrofoil-boat design (or other) that may lead to accepable behavior during take off and landing in rough weather?

I am thinking about a 5 ton craft.

The wing would provide:
25% lift at 23kts
50% lift at 32kts
75% lift at 39kts
100% lift at 45kts (airbourne)

 

The 'Empire' and similar flying boats were excellent in their day, 1940's, with the technology of the day. I think modern engines, composite fabrication, advanced alloys and titanium, modern electronics, and better fuels would 'make them great again'. (Sorry). The hull steps could be covered up once airborne with sliding or pivoting panels to streamline them. Or you could go the way of enormous ground effect flying 'boats', like the 1970's - 1980's Russian monster 'planes'. Hull designs have advanced since those days too. Maybe a ducted air jet to break the 'suction' of the new aerodynamic hull at lift off, instead or the multiple hull steps used back in the day. You should be able to have a payload much greater than 5 tons these days. Sounds interesting, please elaborate.

 

Shin Meiwa US-1A - Wikipedia https://en.wikipedia.org/wiki/Shin_Meiwa_US-1A
5 ton craft at sea state 5 or 6 it will be difficult if not impossible . Pure carbon build , turbo props , maybe.

 

Retractable water foils to get the hull above the waves. Sailing boats get 40 knots with wind power alone.

 

Thank you, this is an excellent reference

 

Or a retractable hydroski like in Convair Sea Dart https://en.wikipedia.org/wiki/Convair_F2Y_Sea_Dart
regards
krzys

 

Check out regent in Boston. They are doing exactly what you say for passengers. It’s a startup at the prototype stage

 

WMO sea state code ; 6, 4 to 6 metres (13 to 20 ft),

Sea state 6, You want to be able to land in 20 foot waves flying an airplane that will fly at 45 knots???????

 

I discussed the sea state issue with the team. Sea state 6 seems impossible. But emergency landing during sea state 5 seems necessary (but no take off). Sea state 3 would be sufficient for take off and landing in normal operation.

Do you think this is feasible?

A couple have mentioned hydrofoils. I was thinking a low aspect ratio hydrofoil with large sweep or even a delta configuration. This hydrofoil would functionally become a water ski just before leaving the water. I am worried about ventilating the hydrofoil when close to the surface.

What would be a good hull shape above the hydrofoil? Is a flow detachment step or kink needed? Multihull?

Does a spring and damper suspension system make sense on a hydrofoil?

 

Something like this: iFoil https://www.boatdesign.net/forums/sailboats/ifoil-53280.html
could be appropriate. Works like a hydrofoil when fully immersed, then like a ski when planing. Exactly what is needed for your purpose. Obviously, the suspension makes a sense in this case.
regards
krzys

 

Fantastic, thank you!

 

Designing for rough water operations at sea state 5 or 6 is challenging but possible. Hydrofoil technology could help reduce drag and improve stability during takeoff and landing. Consider a retractable hydrofoil system to lift the hull above the waves, minimizing drag and impact. A stepped hull with a deep-V shape can also improve rough-water performance. Look into modern planing hull designs used in offshore powerboats—they handle wave impact well. Computational fluid dynamics (CFD) simulations can help optimize the hull shape for both water performance and aerodynamic efficiency.

 

Thank you. I looked into this review of planing hulls:
A review on the hydrodynamics of planing hulls - ScienceDirect https://www.sciencedirect.com/science/article/pii/S0029801824003834#bib225

Among the linked shapes I find this one promising:
https://www.researchgate.net/profil...-Royal-Netherlands-Sea-Rescue-Institution.pdf

I like it because it is comparatively "round", which is promising for the aerodynamic behavior.

 

Take into account, that for the takeoff and landing on the water, the longitudinal stability is an issue rater than advantage.
While boats are expected to maintain the longitudinal trim, the airplanes must change their angle of attack by several degrees.
A single transverse step allows for this, while the pitch stability during planing is achieved by the aerodynamic elevator.
On the contrary, with a typical planing boat hull with lengthwise steps, the rotation during the takeoff would be difficult.
regards
krzys

 

Is this tanverse step necessary with a hydrofoil?