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Old 24 February 2003, 14:35   #21
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Isn't it just a variation on the modified V concept? This is very common in planing hull designs where the deadrise reduces aft to make planing easier -- the compromise is that you lose some of the benefit of the deep V in the rough, but you gain in efficiency.

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Old 24 February 2003, 16:20   #22
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Osprey's XR range had Delta V hulls in the early days however they were slowly modified over the years so it is difficult to see it on the later boats, but the early ones you could actually see it quite cearly. There was a firm in Cornwall, prehaps "Vulture Ventures" who also used the same mouldings, seem to remember a bun fight and possible court action over design rights until it was all sorted out.

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Old 24 February 2003, 17:35   #23
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JK I suppose everything with a deadrise of more that 23Deg is a modified Deep V.

To try and describe it is to say where the expected planing surface starts e.g aprox 2/3rds down the hull at the bottom of the Deadrise there is the start of a flat section that extends aft to the transom cutting the V into small A withought the top bit.This A/Flat piece could be aprox 6/18 inches off the bottom of the V when it arrives at the Transom and the length/height is down to different builders experience.

The concept is that providing more lift withought compromising the deep V at the criticle point it goes faster for less power and when deep V is needed it is there when it is required.

Its a balanceing act.

To achieve a efficient Delta Keel you need to do lots of testing,this can be done within a reasonable budget and the size of the delta/flat can be experimented with to find the best size/ height/length to achieve the optimum performance for the given hull length and weight.

I havnt seen the XR but I suppose even if I had I cant comment on there design as some people will get it right and some will get it wrong.

With a fibrglass hull mould this sort of experimentation can be very expensive and usualy you try and get a good all rounder first off when the hull mould is built.

Its interesting as the stepped hull concept came from the US and ended in court action in the UK I beleive.

The length width height of our Delta keel is a closely guarded secret by our builders as the cost of developments were high and the info gleaned is commercialy sensative.

The Acid test is what otheres think who know of the builders designs and there ribs, and one takes into account there established reputation within there respective market place for producing offshore ribs.

If they are respected for there achievments and quality then you give it a shot.



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Old 24 February 2003, 17:52   #24
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how does the performance advantage differ between that of the delta hull and the adversed chimes that Balistic ribs have. Does any one know? that is compared to a deep v
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Old 25 February 2003, 01:10   #25
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The delta keel is what can make or break a hull. to far forward and to wide and it will hit hard. It is more work than the standard deep v. but worth every effort. the boats can plane with less hp
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Old 25 February 2003, 01:48   #26
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From Crazyhorse's description and Eskrae's picture then what is being referred to is just a "planing pad". Again, hardly revolutionary but done better by some manufacturers than others!
Quote:
Crazyhorse wrote:
The length width height of our Delta keel is a closely guarded secret by our builders as the cost of developments were high and the info gleaned is commercialy sensative.
It's not worth guarding that closely as it's only secret until the first boat gets sold!

DGPW, the hull design used by Ballistic, Crompton and a few others has a "delta keel" (or a "Delta Conic Planing Curve" as Crompton's like to call it) as well as the ragged chine design. They also have an extremely deep V at the bow. They plane easily, carry heavy loads, and have a hard ride.

RIB hulls designed for serious offshore work, such as the Ribtec for instance, have a very plain hull with a constant deep-V all the way to the transom and few spray rails. This makes for better performance in the rough, but does mean thay they aren't the fastest boats around.

There are all sorts of weird and wonderful variations on the deep-V hull, few of them truly revolutionary. They are all a compromise between offshore performance, speed and economy. Horses for courses . . .

John
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Old 25 February 2003, 03:06   #27
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Why dont you design and build boats JK?
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Old 25 February 2003, 05:33   #28
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Paneing Pad

When I tested the Osprey which had a huge planning pad my back nearly snapped in half when the boat landed. This was the reason we did'nt buy it. They slam like mad.

I assume they got the design wrong. Got on the plane very quickly but was useless in a moderate sea.

Julian
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Old 25 February 2003, 05:51   #29
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Quote:
Originally posted by crazyhorse
Why dont you design and build boats JK?
Why would I want to do that? There are plenty out there already

Julian, I know that some of the early attempts with planing pads (way back when it could possibly have been described as "revolutionary") were pretty disasterous. Things have moved in though, and Ospreys these days certainly don't suffer from this problem!

John
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Old 25 February 2003, 06:05   #30
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Planning Pad

Hi John

Well thats good to hear. It was about 12 years ago that we tested it. I can feel the pain just thinking about it.

Julian
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