The 18.3m long hull displacing 4500kg with a flat bottom will have very little dynamic lift when in level trim. It is not planing.
At 30kts the bow of the hull will be passing through waves. The best place for the 'V' is on the deck so it will lift easily when submerged.
One issue with a wave piecing hull is the tendency to dive into the backs of waves when running. In waves having wavelength about twice the length of the hull it is quite easy to drive the hull underwater if it has a flat deck. It seems the 'V' decks lift better. I am yet to test this.
Rick
--- In harryproa@yahoogroups.com.au, barrie lyall <protocomposite@...> wrote:
>
> Extremely interesting comment Paul, As a somewhat recent multihull convert I think this is a very important topic. Could we venture to say that less of a planing and perhaps a more V form hull would be something to consider for blue water sailing?
> --- On Sun, 7/25/10, Paul Wilson <opusnz@...> wrote:
>
>
> From: Paul Wilson <opusnz@...>
> Subject: [harryproa] Swells in open ocean
> To: harryproa@yahoogroups.com.au
> Date: Sunday, July 25, 2010, 11:01 PM
>
>
>
>
>
>
> I have found the recent threads very interesting and thanks to all for
> their contributions. One thing has been bothering me though. Talk has
> been of large proas at high speeds. I assume these are designs for open
> ocean. 12m, 15 m and speeds of 25 to 30 knots have been mentioned.
> This seems unrealistic to me and would be designing for an ideal of high
> wind with flat water and no waves. Having sailed offshore, I know that
> a 10 to 15 knot trade wind that has been blowing for a few days normally
> kicks up a 2 to 3 meter swell. Going 25 knots on a 3 meter swell with a
> light boat could launch you into the air. These waves are what limit
> your speed as their tops crash into beams, superstructure, or you. If
> one is designing an offshore cruising or racing boat, wouldn't it be
> better to design for max efficiency at a more realistic speed? Say 10
> to 15 knots for a fast, offshore multihull? This seems more realistic
> to me and may result in a boat that was more all round, easier to keep
> "in the groove" and possibly faster.
>
> As an illustration, I have a friend currently sailing from Galapagos to
> Marquesas. His average speeds have been between 6 and 7 knots on a 35
> foot catamaran that in the same conditions in flat water would probably
> be 12 knots or better. The pounding and smashing if he pushes the boat
> is always so bad that he has to limit the speed. On my heavy 36 foot
> monohull, I have made passages in the same conditions in less time, due
> to the fact that I can push the boat harder without beating myself or
> the boat up. Everything says the multihull should be much faster than
> my heavy monohull, yet I know offshore, the reverse is true.
>
> Something to think about.
>
> Cheers, Paul
>