REPLY: Hello John, A very interesting read, thank you. It's amazing what a great teacher hands on offshore experience is. I had a similar history to you commencing back in 1984 when I first moved onboard my 33' motor sailor catamaran before putting over 17,000 miles of water between the 22' wide but skinny hulls cruising west about from Australia via the Mediterranean to the Caribbean. I also put over 3,000 nm on a large planning hull power catamaran, which was a disaster. These experiences are why I used semi-displacement hull forms for my long range power catamarans in 1997 and they have successfully put in thousands of sea miles for their happy owners ever since. Malcolm and I often discussed his narrow hull theory over my hands on experience. I also went down the "build in China" route you are taking. From 2001 to 2004 I did business with a company who had been building "Halvorson" and other fiberglass powerboats for the US and global markets for over 20 years, but the experience was not good, even with our own ex-pat project manager on site five days a week. My point being 30 years experience building boats in China is no guarantee they will build a boat to the standard expected by North American and European customers. In Shenzhen City, Guangdong Province my 5 star hotel had rats from the basement to the 8th floor where I was staying. Their 5 star standard is not necessarily the same as ours and this also applies to boat building. China is a developing country progressing on the backs of foreigners pouring money into their country and they will do whatever it takes to make as much by giving as little as they can. The lesson I learnt there was, unless you own the building, own the business, employ the workers and have Ex-Pat Managers you can get into trouble. I checked your excellent web site and your concepts with the same note of familiarity similar to Pacific Expedition Yachts. It states you are up to your 7th boat with your Far East builder but I don't see any construction photos of your power catamarans on your web site yet. This would be nice for us all to see and follow their progress. Cheers, Graham Captain Graham Pfister President & Principle Designer TrawlerCat Marine Designs Message: 3 Date: Wed, 18 Nov 2009 22:31:58 +1300 From: "John Winter" <john@adventurebay.co.nz> To: <power-catamaran@lists.samurai.com> Subject: [PCW] Foils and roll motion Message-ID: <!&!AAAAAAAAAAAYAAAAAAAAAI7PnsOKHgJCnsQBtPG/eRbCgAAAEAAAAHdYDmY3y2BIiHZnQre7 SRMBAAAAAA==@adventurebay.co.nz> Content-Type: text/plain; charset="us-ascii" Personal Observations on Foils and Skinny Hulls. The research I have done over the past 8 years on Foils and roll motion- testing many powercats in wide ranging conditions, living afloat on cats for a few years has led me to these conclusions: 1. Foils for their extra $25-$70K cost (cost depending on size, country of origin and level of sophistication in trim control) are advantageous for boats wishing to cruise at 28-35+ kts for many hours a year. For ferries its ideal as the payback in fuel saving running 8hrs a day will be soon realised. Pleasure-boats may take a while to get payback VS adding more horsepower but the eco-conscious boater will like it. Depends on the deal you get on the engines on the day. 2. Personally riding on foil boats into 10-12ft head seas at 25kts and feeling very soft landings (a 14m boat) was enough to convince me they certainly improve ride, like adding leaf springs to a vehicle with no suspension. Our 26m Tennant cat would break things in these conditions, even slowing to 6 kts, due to lack of reserve buoyancy in the hulls and knife like fine bows. 3. But by just adding Foils on a slim hull cat will miss a large part of the hull improvement opportunity. Adding fullness above waterline in the bows helps reduce bow tunnel pounding and a foil will soften landings on fast boats, hence our new hull shape was developed after 6 months pounding across the Pacific in skinny hulls bruising the crew black and blue. We and the crew of boat-builders all decided future boats will have less tunnel entrance, 2 months in Tahiti repairing tunnel delamination and core shear gave us time to think this over. (Composite originally engineered by a leading composite design house might I add) 4. Further to the crews bruising was the snappy roll motion of skinny hulls in beam seas. A 16 day voyage from Marquesas to Galapagos with a naval architect, an engineer and 2 boat-builders aboard gave us time to reflect. Skinny hulls are for harbour crossings, not real time, confused ocean seas. Wide hulls we think have slower immersion rates so they don't sink down quickly to the tunnel buoyancy and stop dead, snapping back when the arched tunnel is reached. They immerse slower, finish their roll softer and some weight aloft also helps slow the end of the roll. 5. Performance figures from leading ocean going ferry designers of wide hulls showed their well designed hulls were operating as fuel efficiently as our skinny hulls so naturally we crossed over when we experienced the improved ride. Well designed is the key, some builders have taken old design hulls from old moulds that weren't designed well to begin with and certainly not for the new superstructure balance and make a boat out of it. The hull has to be optimised for the speed, weight and superstructure by a QUALIFIED naval architect who knows how to calculate and computer model it and has done many ferries and pleasure-boats to his credit to compare, not a self taught draughtsman guessing it each time. 6. The people we learnt about wide hulls from and selected for our new hull designs have hundreds of ferries crossing ocean straits in all corners of the globe where stiff penalties for getting it wrong would have sent them out of business. They charge a fair penny but the result is worth it. Kind Regards, John Winter Managing Director Adventure Bay Powercats Cell +64 21 454 107 www.adventurebaypowercats.com ------------------------------ Message: 4 Date: Wed, 18 Nov 2009 06:41:27 -0500 From: "Russell Hunt" <info@mdcats.com> To: <power-catamaran@lists.samurai.com> Subject: [PCW] teknicraft foil boat Message-ID: <20091118064127.a0r075fkzxhcwcg0@webmail.uplinkearth.com> Content-Type: text/plain; charset=UTF-8; format="flowed" Bob, Thanks for the information. I put a call out to the owner of Reel Time Charters. Looking forward to discussing this design with him. Russell Hunt, President Multihull Development, Inc. and Buzzards Bay Catamarans Office #: 508-403-0301 Cell #: 508-759-4111 Other #: 800-882-7083 Email us at: info@MDcats.com Check out our website at : www.MDcats.com http://www.yachtworld.com/multihulldevelopment/