Peter R Payne-Sea Knife-Blade Hulls

Come on baby, attach...

Peter Payne's hydro patent:

 

I'll have to see if I can dig up the pictures I have somewhere. It was a smallish testcraft and trailered; what was most remarkable to me when I saw the pictures was how innovative the foil retraction and stowage details were.

 

I would venture to suggest that his Sea Knife design did not get more prolific use for at least two reasons:
1) Government/Defense Department Market
...too conservative at that time (and presently) to fund such experiments, or even give 'radical ideas' serious consideration.
2) Public Boating Market
...the vessel offered too small of an interior accomodation, and its stablity at rest was very questionable.

My renewed interest in this Sea Knife concept is spured on by the possibilty of using such a hull design as the basis of a 'new concept' RIB. The inflatable 'collar' of a RIB might well take care of the 'at-rest-instability' of a Sea Knife vessel,...plus some other thoughts. :idea:

 

Well, isn't that thought provoking...

 

The Sea Knife was based on the concept of a high planing surface loading, with a relatively small increase in planing surface area as wave action was encountered. Aside from an increase in skin friction due to increases in surface area, the Sea Knife could provide a soft ride within the a relatively narrow range of operating speeds.

The delta planform, as is used in high speed aircraft, provides the ability to provide lift at high angles of attack, and therefore expand the planing envelope.

While it did appear to work, there were, as others have noted stability problems with the design.

Since the Sea Knife was developed (in the late 1960's and early 1970's), the knowledge about padded V hulls has increased exponentially. I would think that some of the Sea Knife features, (such as the bow and side shaping) married to some from of padded V hull with high deadrise, might provide a good ride, but might not have the other attributes that doomed the Sea Knife... More food for thought

 

Mmmmm, chewy, chewy...

Thanks YJ

 

Spray Sheet Reversers

Something I just noticed. It does NOT appear as though this first 'racing' SeaKnife had the 'spray sheet reversers', that were discussed as very positive attributes in the Supercritical Planing Hull paper that has been referenced earlier in this subject thread:
Supercritical Planing Hulls

These 'spray reversers' are introduced on page 8 of the document, and illustrated on page 11

"One of the most interesting developments has been in the successful development and use of the lateral spray sheets which are characteristic of the Sea Knife. "Spray" is really a misnomer, creating an impression of discrete droplets, but it is hard to think of an alternative word which is not ponderous and forced.

These reversers, illustrated in Figures 23 through 25, were originally intended to recover substantially all of the vertically oriented momentum as dynamic lift. It was then realized that, if the reverser had a bow-down slope to it, not all of the vertical momentum would be recovered, but the force that was reacted would be forwardly inclined, reducing the net pressure drag.

Figures 26 and 27 show how one particular set of reversers performed in practice. In the configuration shown, and without changing the propeller, the top speed of the boat increased from 32.0 mph to 41.6 mph with the reversers in place.

....continued"

 

Delicious.

Similar hulls...

 

Marker~~~~

 

Will bump up that old theme...

I did a pretty decent piece of work, researching the case of the sea knife and its features.

To do this, we had to restore the geometry of the hull, collecting information piece by piece literally from everywhere.

Payne's book does not contain much information about the hull - only general information, from any reference book on hydrodynamics. (Rather, even more from aerodynamic)

Surprisingly, you will not find too much useful information, probably due to Payne's work for the government and the classified work.

In addition to the detailed design and calculations, I tested scale models (8.5m deep V hull vs. 7.5m sea knife) in open water equipped with accelerometers to compare the results.

Based on the results, I can highlight several features of this case:

1. Indeed, the vertical accelerations measured at the place of the pilot's seat for the "sea knife" body are several times less (in my case - 4 or more, no matter how strange it may sound). The wave height was approximately 1.5 m, in terms of actual size.

2. Initial stability is insufficient, when a heeling moment occurs, the hull receives a significant heel until the edge of the deck touches the water. Then the righting moment increases sharply, up to 90 degrees of heel.

You can see a typical stability diagram in the appendix.

Unfortunately, I did not determine the curb of the total resistance of the hull, due to the lack of funds.

On the whole, in my opinion, the hull is of some interest, and some of its shortcomings can be overcome by constructive solutions and modern materials.