A little Malcolm magic

[klee wyck]

This Malcolm Tenant CS hull design continues to impress me and it seems odd that others have not seemed to have picked it up. The underlying premise is a canoe stern hull that shines in displacement mode in terms of comfort and efficiency with an L:B of 12:1. This 65' footer can get 3 nmpg at 9 knots. Then, in order to access speed at reasonable fuel burn, he adds a short flat section aft above the canoe stern tail that causes the stern to come up as you exceed about 20 knots. You can see this phenomenon at about 0:16 in the video. At this point I think the forward 80% of this vessel is still in displacement mode even at this speed?
It takes less than 500 hp to get this 65' boat to 22 knots of speed.
And little to no wave making....
This thing defies logic for me....

 

[READY]

500 HP, 20 kts sounds impressive but I am confused. Is this a cat hull? Is this a production boat? Are there any available for sale? L/B of 12:1 does that mean the beam is just over 5 ft?

 

[klee wyck]

500 HP, 20 kts sounds impressive but I am confused. Is this a cat hull? Is this a production boat? Are there any available for sale? L/B of 12:1 does that mean the beam is just over 5 ft?

Cat=yes
production boat=no, but a dozen or so out there
any for sale=yes
beams just over 5=yes for underwater portion

 

[Insequent]

It is an amazing cat hull, and was custom built. Sadly Malcolm died a number of years ago in an accident, way too young! For a time his family continued to sell plans of his designs, although I don't think they have an obvious web presence at this time.

One of his colleagues from that era, Anthony (Tony) Stanton is in Auckland and might be able to assist with tracking down plans of his designs.

 

[kapnd]

It is not planing on the small flat, look at the waterline at speed.
The hull is reminiscent of a box keel design, and I doubt that it does plane at all.
A long, skinny displacement hull can post impressive speed and not be planing.

 

[Insequent]

I seem to recall a comment that the small flat section was all about additional buoyancy to avoid burying the stern.

Here is an article about Malcolm. Somewhere I have some more bits and pieces, other articles etc about the CS design but can't readily find them ATM.

 

[klee wyck]

I seem to recall a comment that the small flat section was all about additional buoyancy to avoid burying the stern.

Here is an article about Malcolm. Somewhere I have some more bits and pieces, other articles etc about the CS design but can't readily find them ATM.

I agree with your assessment of what the flat stern section does and have heard the same. This is what keeps the stern from squatting when you add power as in most displacement designs. The boat remains pretty flat in fore/aft orientation throughout the range of speed.
However, as you can see in this video, the water line reappears aft, and the vessel seems to push easier when passing through about 20 knots of speed. This 20 second video starts around 17 knots and ends around 22 knots, I think. This was a couple of days ago returning home from a cruise with my brother in another boat to take this video.

 

[READY]

@Insequent Thanks for sharing the article. He certainly was a prolific designer.
Ken