Reverse bows on cruising cats pros and cons

Yes, agree.
But what does he know about model testing technique, this was the question?

 

Gary

Pretend we are in a pub - you are about to go after Alik with arms windmilling away shouting "Let me at him - let me at him". I am grabbing you and shouting into your ear - "He's not worth it - He doesn't know anything. Let it go. He's just baiting you." Then I would buy you a drink and we would talk about Spencers sneak boxes, or Titus Canby or John Sayer racing a Ferro boat, Tennant developing strip cedar composite, Bruce Farr designing anything, Waverider, Newspaper taxi, any Bladerunner, Split Enz - or the fact the Edmund Hillary had his number in the phone book - listed in the normal phone book!

I am out with this thread. Saying silly things about Kiwis is just dumb. You guys have to cross rough oceans just to get to the south island!

Go and sand Sid's mast and I will go away too. There's much more sanding/gluing/painting for me as well.

When I get to Auckland I will buy you that drink -especially if I can look over your boats with their well designed and very fitting reverse bows (wasn't that the point of the thread?).

cheers

Phil

 

As usual. Words of sanity from Phil.
I think it all comes down to "Horses for courses".
Wave piercing reverse bows on "all or nothing" racing boats.
Veed overhanging bows (like Wharrams "Ariki"), for dedicated cruising boats.
Just my 2c worth.

 

The only advantages are in pure marketing; since the actual 'advantage' is simply increasing the L/D ratio which is not magic and there is no magic in that increasing the L/D ratio reduce vertical accelerations. How you achieve this, and what is actually effected, is simple as noted here:
http://www.boatdesign.net/forums/multihulls/proa-questions-33138-2.html#post372968
But how one "claims" this as noted here::
http://www.boatdesign.net/forums/boat-design/reserve-buoyancy-37589-2.html#post456511
and more generally:
http://www.boatdesign.net/forums/bo...g-myth-design-ingenuity-30296.html#post318566

...is another matter all together. Why let science get in the way of a good "story" or "claim"??.

Claims are all well and good, but supporting them with evidence that is contrary to existing and well known and established science which explains the very simple "why" it is so, is another. Since then goes down the road of marketing and "belief" systems. Those that don't understand "believe" it...whereas those that do understand it note: "what is so new about that".

Which ever side of the fence one sits on...this is nothing new, the claims nor the endless ad nauseam circular arguments. Never the twain shall meet. The science has been well documented and can demonstrate the "whys"...but as always that doesn't sit well with some people. They like to claim it is ..well....make up their own 'advantages' to suit their own narrative!

 

For those great experimentalists and native designers, who like to claims some advantages based myriads of YouTube videos, here is one of the graphs we made during sea trials of our 11.5m powercat. It represents level of vertical accelerations depending on speed, for craft's CG and forward perpendicular, head wave, H1/3=0.5m.

So, can we see something like this for reverse bows?
I mean we do such measurements for most of our designs, during sea trials... I just pulled this graph from paper I am working on now, for conference.

 

New Zealand

===============
This is one of the most pitiful comments I've had the misfortune to read on this forum!! I'm astonished that a supposedly "reputable" NA would stoop so low. You should apologise to the country of New Zealand and to the great sailors and designers you have disrespected.

 

Alik, do you sail ?

 

If You just go to our website, You can find the info You need...

 

@Alik
Sorry for off topic, but since you

, there's a typo in the graph you may want to correct before the conference.

 

I was looking at the Neel 45 and noticed it doesn't have boards or any keel except for a small skeg. The sailing photos all show the main hull and leeward ama bow in contact with the water versus raising, getting a good bite with the reversed bows. Shades of the deep forefoot of the Arab dhow or English coble. Have anyone measured the leeway these boats make? They are quick and point well but there has to be more leeway than a boat with boards. It is an interesting use of reversed bows.

 

Exactly. So those who look at youtubes of model yachts should be aware they need to slow them down to make them look more realistic

Richard Woods

 

Bloody hell, Alik, do I see a slight, but of course, subtle? reversed bow tendency on your non-sailing craft?
LOL Catsketcher, we needed that.
Oh yes, Ad Hoc, you forget an important factor in reverse bows "just" adding length/displacement ratios - a most important thing is the lowered and "clean" water draining curved deck areas.
See, observation and practical sailing experience does have relevance too.

 

The most researched/developed vessels are naval ships. A light long narrow frigate or destroyer has very similar proportions to a single multihull hull

So why do modern warships generally have raked bows, but pre WW1 warships often had ram bows, eg the US Connecticut Class Battleships?

What made the navies change their minds as to the best shape? That's obviously a question for naval architects rather than for yacht designers. I remember reading a paper from the early 1960's regarding "Wetness relating to freeboard and flare" which certainly did NOT recommend vertical or ram bows

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Oh silly me, I thought a fine angle of entry entry, sheer line and cambered deckl did that, but hey, its only an "observation" rather than facts! Why let facts get in the way...

 

Lachlan Crowther was a grad engineer. He studied mechanical, control systems and electrical engineering and was a very bright well connected individual.

Ben Lexan/Bob Miller employed Prof Engineers and Hydrodynamicists who really designed his later boats, and other professionals designed his rigs and even his boats sails. He was the ideas man but the ideas were implemented refined and improved or rejected by others.

Farr employed Engineers almost from his inception as designer. In the 70's he went into partnership with an Engineer and they designed together. In fact Bowler was pivotal in the success story and it was he that developed and introduced the light weight foam core designs.

Piver ; I'm not sure I'd call him a great leading designer rather an achiever and a great marketer of trimarans, the truth was often twisted a bit in his claims. Cross improved his designs a lot.

Not sure I'd call Wharram an amateur either. Didn't Wharram study construction engineering, City and Guilds? Then he worked at Thornycroft and also had a boatbuilding apprenticeship. He had access to a lot of professionals and learned quickly and was quite conservative as a designer.

Nigel Irons like any modern successful design office employs a team of professionals who do the design work.

Often professionals are often employed on designs and never get the slightest mention. If you are outside of the field all you see is the personality /marketing name.

For the early amateurs that didn't seek pro input, design was usually trial and error and often just as much error as success. That trial and error lead to a lot of disaster.