Wave Piercing Bows

It's not irrelevant

Groper - the bow shape styling is not irrelevant. You can't just plonk any bow profile you want on any hull. The shape is heavily dependent on hull flare. Very few cruising cats have inward sloping sides so the reverse bow will be a low volume and therefore hydrodynamically useless affectation. With its knife edge it low volume immersion rate it will help broach the boat better than any deep forefoot as well. Put one on if you like - it will be your boat -you can put any protuberance on but it will not be doing anything much and shove some bigger rudders on as well to help in a following sea.

I would be a bit careful of styling for its own sake - it really dates a boat. The sleek very low slung cabins of some cats with massive almost horizontal windows are now a historical legancy as owners got sick of living in a glasshouse in the tropics. Reverse bows will probably be the same as they serve no real purpose on a cruiser apart from looks. Even the graceful overhang of metre boats was useful from a racing measurement point of view.

Rattus - I will see if I still have the interview on my computer but I have had some hard drive crashes since then. It was when I looked over B and Q at Boatspeed. I rang Irens for the article that appeared in Multihull World.

cheers

Phil

 

I may have a copy of the multihull world magazine. I have issues from number 66 up to the current issue. I do know I have the one with B & Q in it.

if you have no luck Ill see if I can scan it and put it up.

I am still working on putting files up this would be a multiple page file which I am not certain of.

 

+1 and I would add that intended use must also be a consideration...and the water. The best example would be the last AC. Alingi v Oracle...not even close, but two different boats also...

I would also look to find information on MacAlpine-Downey boats. As you will note, slick as they come, but back in the day.

And for a twitchie sleep, dream about an AC 72 pitchpole...

 

Well, pictures speak a thousand words...

Schionning...


Grainger...


Morelli Melvin...


Loic Goepfert, (Alibi)...



And ill give a quote by Rob Denny because i cant say it any better my self;

 

Not wishing to sound flip or sarcastic, but the quote seems to be mastery of the obvious. No one here would disagree, would they?

 

Reverse bow-better by design(in many cases)

One thing I've noticed is that most of the racing multihulls using reverse bows also use lifting foils(the combo doesn't have to be limited to racing boats). I'd say there is ample evidence that that is not a coincidence. I don't think you can judge reverse bows as unseaworthy without understanding more about the boat they're used on. For instance, the fastest trip around the world ever was completed recently by a tri with reverse bows-and lifting foils. In my opinion, lifting foils and a reverse bow work together in many respects to produce the optimum high speed multihull design from 18' A Class Cats to the 130' Banque Populaire V:

click on image-

 

Good observation. Makes much sense too.

 

I can almost do the morelli and melvin bows and I can definitely do the Loic Goepfert ones, so I will.

 

Do 'em all.

Perpendicular bow frame...x wide, with some sort of rails mirrored by slides or attachments on three for four bow blocks to slide on and afixed...? Is possible, if you wish to play.

 

I still don't like the increased vulnerability to flotsam and jetsam....yes the foam can repaired but that can mean putting up with a lot of drag from damage cruising while you try to get to a place to haul out. If I used reverse bows I'd be back to working out field/sea replaceable or inflatable versions....

 

I would likely use laminated pine or spruce...thinking as you do, foam too flimsy, particularly for beaching boat etc.

 

I don't know many catamarans (such as pictured) that touch their bows to the beach when drying out.

 

The average boat with a cabin has to successfully meet many more criteria than does a dry sailed racing boat of any size.

I remember being at anchor and leaning over the bow to fend off another boat that was dragging onto me.

And being in a wind over tide situation and having the anchor warp running up the stem in every gust. In those situations having a bridle doesn't help as it also goes slack. I once saw a ship turn on the tide and heard the incredible noise as the chain jumped over its bulb bow. It disturbs sleep and doesn't do much for your paint job either

Usually I come into a dock at 45deg and have someone on the bow to either hand the bow line ashore, or jump ashore themselves. Most of the docks and marinas I visit seem to have only one undersize "parking" space left. I say "parking" because we all know from parking a car that if you cannot see the "bows" it is much harder to maneuver safely.

Many sailing guests like sitting on a bow/pulpit seat. Even sailors like to have a wide solid deck to stand on while working in the bows with a good rail all round

And Catsketcher is right. I don't see how you can retrofit a reverse bow unless you shorten the boat at the deck line and then pull the gunwales in. If not then you must end with very hollow waterlines, not good for speed and looks really wierd. Unless your hull has a very poor shape to begin with of course.

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

We will have to disagree

If you look carefully you at the hull side of the Morelli Melvin cat you will see typical hull flare further back. So as Richard says the gunwale gets twisted in to reverse flare at the bows. A bit of me says "Why not just keep it the same and get a plumb bow?"

I really understand the logic behind the concept. Having sailed tris for a over a decade I love the concept of a bow that can go underwater and not trip the boat. Essential for broad reaching in big swells. When I was a little tacker I remember John Hitch talking of a Piver Lodestar that he was in that dug its float bow in, stopped and almost flipped. He then helped draw and built the first Kraken 33 - Manta 2. Manta 1 was a Piver Nimble. My Piver Nugget did the same and sailing my Twiggy in swells was so much easier with a beautiful wave piercing bow. I went and watched the A class cat Aussies and all the new ones had reverse bows - they are a great idea for these boats.

What I don't get is why a designer would put a bow on that is going to be harder work than a plumb bow is at anchor and mooring when the design premise - wave piercing - cannot be carried out because of the huge drag that is not in the designs that reverse bows came from. Drag from the forebeam, netting, walkways, cleats, and on the bottom Goebfert boat - a massive prodder. If the designers were serious about reducing tripping drag they would do what Crowther did in the early eighties and move the forebeam way back. A class don't have any of these things, AC 45s do have the prodder but it way up high and a single tube.

The safest thing a boat can do is keep you on board - falling overboard is the most dangerous aspect of sailing. So flat and wide enough decks actually make sense - even up the front as a modern cat (35ft plus) with good freeboard will almost never put her nose under. unlike the A class and the trimaran float.

The concept itself is fine and sensible but this is like putting spoilers on a tinny car. Looks like a racer but does not serve the initial design purpose.

Anyway Groper - have fun building and drawing your boat. I am just trying to be the fly in the ointment. I often wish I could go back in time for some of my builds and give myself a talking to. Of all of my innovative ideas about half have turned out to be turkeys, a quarter have been fine and a quarter have been gold.

cheers

Phil

 

well i dont completely disagree with all of this, and i know what you are saying... one of the things that always bugged me about this bow shape was tripping on mooring lines etc and is a negative trait, same goes for parking/fending off but it comes back poor boat handling to begin with although not always by you - as in richards example.

For me, if this ever happened and some small damage resulted, id simply fix the ding in the solid foam bow no big deal.

As for the wave peircing perforamance, theres no need to think of things in the extreme. The reverse bow doesnt have to have HEAPS of negative rake, it can be almost plumb with just a touch of reversal for styling - the difference is nothing im sure youd agree. Same goes for the submergence when pressing hard, if your pressing that hard that the prodder on that alibi cat was submerging, then you really must be flying - is this cruising or racing now and are you insane or sensible?
Think about how it will perform when sailing more moderately rather than extremes, which is where a cruising boat will spend 95% of its life... it will provide higher cruising speeds as the bows have less drag when pushing through smaller waves that dont completely engulf/submerge the bows. It also means less spilled drinks from reduced pitching or hobby horsing although probably not much...

One reason i chose the reverse bow with moderate 15deg reverse rake, was it allows a very fine entry and reduced drag in moderate seas as the bows dont present such a blunt entry when pressed into waves. I also beleive i will get less spray due to the same, which is why i have omitted spray rails and/or knuckles as the spray from these blows in over the side in anything but a true headwind anyway. I guess we will see what comes out in the wash...