Fin stabilizers on cats

GK
Georgs Kolesnikovs
Mon, Nov 16, 2009 1:46 AM

From: "Tim Chrisp" tchrisp@cedenco.co.nz
Date: November 14, 2009 5:38:11 PM GMT-05:00
To: power-catamaran@lists.samurai.com
Subject: fin stabilisation

Dear Sirs,

I am not sure if your forum is still operating bit I am keen to hear if
anyone has experience with passive fins set between the hulls of a
displacement catamaran for slow or modest speed stabilisation.

Look forward to hearing from you

Tim Chrisp

New Zealand

From: "Tim Chrisp" <tchrisp@cedenco.co.nz> Date: November 14, 2009 5:38:11 PM GMT-05:00 To: <power-catamaran@lists.samurai.com> Subject: fin stabilisation Dear Sirs, I am not sure if your forum is still operating bit I am keen to hear if anyone has experience with passive fins set between the hulls of a displacement catamaran for slow or modest speed stabilisation. Look forward to hearing from you Tim Chrisp New Zealand
RD
Robert Deering
Mon, Nov 16, 2009 4:37 AM

On 11/15/09 4:46 PM, "Georgs Kolesnikovs" gxk@earthlink.net wrote:

I am not sure if your forum is still operating bit I am keen to hear if
anyone has experience with passive fins set between the hulls of a
displacement catamaran for slow or modest speed stabilisation.

I've explored it a bit.  There's at least one boat around here featuring a
hydrofoil spanning between the hulls, using the Teknicraft design from your
parts (New Zealand).  My understanding is that the foil only becomes
effective at speeds exceeding 20 knots.  At slower speeds the increased drag
of the foil exceeds the performance advantages of increased lift, which is
almost nonexistent at slow speeds.

Bob Deering
Juneau, Alaska

On 11/15/09 4:46 PM, "Georgs Kolesnikovs" <gxk@earthlink.net> wrote: > I am not sure if your forum is still operating bit I am keen to hear if > anyone has experience with passive fins set between the hulls of a > displacement catamaran for slow or modest speed stabilisation. I've explored it a bit. There's at least one boat around here featuring a hydrofoil spanning between the hulls, using the Teknicraft design from your parts (New Zealand). My understanding is that the foil only becomes effective at speeds exceeding 20 knots. At slower speeds the increased drag of the foil exceeds the performance advantages of increased lift, which is almost nonexistent at slow speeds. Bob Deering Juneau, Alaska
M
Mark
Mon, Nov 16, 2009 5:31 AM

It's not so much a stabilizer as a passive hydrofoil.  Do a search on "Hysucat", HYdrofoil SUpported CATamaran, or Hysuwac, invented by a professor in S.A.  A variant is used on several of the ferries that run to the islands here off the Southern California coast.  Various people have used it to build pleasure boats from 5m Ribs to 50' cruisers.  All the versions I've see were used with planning/semi-planning hulls.  Just as there are high and low speed wings on aircraft, I'm not sure if there is a barrier to using it at lower speeds.    Since you need more lift at low speeds that will have to come with more drag, so if you are willing to limit top speed to say 15, maybe you can find a foil that gives you lift starting at say 10knots - maybe the energy tradeoff doesn't work out at lower speeds - I'm sure it's a complex calculation.


From: Robert Deering deering@ak.net
To: PCW List power-catamaran@lists.samurai.com
Cc: Tim Chrisp tchrisp@cedenco.co.nz
Sent: Sun, November 15, 2009 8:37:05 PM
Subject: Re: [PCW] Fin stabilizers on cats

On 11/15/09 4:46 PM, "Georgs Kolesnikovs" gxk@earthlink.net wrote:

I am not sure if your forum is still operating bit I am keen to hear if
anyone has experience with passive fins set between the hulls of a
displacement catamaran for slow or modest speed stabilisation.

It's not so much a stabilizer as a passive hydrofoil. Do a search on "Hysucat", HYdrofoil SUpported CATamaran, or Hysuwac, invented by a professor in S.A. A variant is used on several of the ferries that run to the islands here off the Southern California coast. Various people have used it to build pleasure boats from 5m Ribs to 50' cruisers. All the versions I've see were used with planning/semi-planning hulls. Just as there are high and low speed wings on aircraft, I'm not sure if there is a barrier to using it at lower speeds. Since you need more lift at low speeds that will have to come with more drag, so if you are willing to limit top speed to say 15, maybe you can find a foil that gives you lift starting at say 10knots - maybe the energy tradeoff doesn't work out at lower speeds - I'm sure it's a complex calculation. ________________________________ From: Robert Deering <deering@ak.net> To: PCW List <power-catamaran@lists.samurai.com> Cc: Tim Chrisp <tchrisp@cedenco.co.nz> Sent: Sun, November 15, 2009 8:37:05 PM Subject: Re: [PCW] Fin stabilizers on cats On 11/15/09 4:46 PM, "Georgs Kolesnikovs" <gxk@earthlink.net> wrote: > I am not sure if your forum is still operating bit I am keen to hear if > anyone has experience with passive fins set between the hulls of a > displacement catamaran for slow or modest speed stabilisation.