Plumb Bows, Slab Sides, and Wet Decks

[Delancey]

Ha, I wish. I live on a clorox bottle. The restoration of Violet by a guy named Gary Maynard was the subject of an article in Wooden Boat Magazine from a long time ago. The plumb bow always stuck in my head.

Amazing restoration, beautiful photographs in the article. Interesting guy, never met him. I think the boat has been sold, not sure where it is these days. Topsides used to be black.

[Polux]

I love those Pilot cutter. Three years ago I meet a guy that had one built from scratch. not much sense in what regards performance...but what a beauty and what a character.

https://www.youtube.com/watch?v=dNP0YrLhK78

Pilot Cutter - Amelie Rose on Vimeo

[OceanSeaSpray]

The shape of the bow is only one part of the wet-or-dry question. Everything else being equal, a plumb bow means the hull enters the waves earlier and has more time to lift. A finer entry also results in a smaller bow wave, but prompts for sufficient freeboard.
Two other main contributing factors to making a wet boat are displacement and freeboard. Add a blunt entry and low freeboard to medium-heavy displacement and you end up throwing spray everywhere and often still shipping the tops on the foredeck.

A plumb bow, fine entry and good freeboard are highly desirable in terms of motion (less pitching) and dryness. Slab-sided is a less clear-cut aspect; it impacts the amount of reserve buoyancy available forward.
Lightweight racers where most of the weight is concentrated near midships have limited pitching inertia and they follow the contour of the sea more easily than a boat with mass away from its centre of gravity (anchor chain, lazarette gear, heavier mast etc). They can cope with fine sections forward more easily.
Ocean cruising boats tend to be more loaded in the ends and benefit from having more volume forward above the waterline, i.e. fine entry but more flare further up in the hull sections, so not so slab-sided when combined with a steep stem. The older slab-sided hulls with raked stems offered more forward hull volume above the waterline than the new ones with steep stems by the way.

I followed this line of thought when I designed the sloop Nordkyn: steep stem, fine entry, curved topsides. The main concern I wanted to address was the risk of driving the bow under into a wave on the run at high speed.
Not only the boat is very fast in all conditions, but it is also incredibly dry. The hull doesn't create much of a bow wave and doesn't cause a sheet of spray to form at speed. Heeled upwind, spray from wave encounters is on the lee side and peels off horizontally.

In my view steep stems give much more seaworthy hulls and a reasonably fine entry is essential; when hull resistance shifts forward at speed (i.e. too blunt and too full), boats become unsteerable and dangerous on the run in heavy seas. Overall hull resistance is also what contributes to driving the bow under; easily-driven hulls are much safer on the run. The challenge is coming up with the correct blend of hull shape forward below and above the waterline for the type of vessel considered.

[Mirage Gecko]

I never really get these discussions.Is it wetter? Or the plumb bow enters the water earlier type comment.
Unless you compare exact waterline length it's all irrelevant.For example a plumb bow only enters the water earlier than anything else if compared to a boat of the same LOA but different waterline length due to bow design.

[Brob2]

I enjoyed this discussion very much so thanks for that and Polux for that beautiful video and soundtrack.

Eric, that was a great post, and it led me to your nordkyndesign website where I have spent much time over the last couple of days reading your thoughts on this exact topic, as well as others, and I am much richer for it. I found it very interesting and informative.

Thanks all!

[Polux]

Originally Posted by Brob2

I enjoyed this discussion very much so thanks for that and Polux for that beautiful video and soundtrack.

Eric, that was a great post, and it led me to your nordkyndesign website where I have spent much time over the last couple of days reading your thoughts on this exact topic, as well as others, and I am much richer for it. I found it very interesting and informative.

Thanks all!

Very nice to find someone that posts about something to have information about it and not because it has already some opinion that wants to impose to others. Cheers to you for that.

Let me point only one more thing that is obvious but that many seem to forget: a boat is more or less wet according to the speed it sails and you can see that looking at race boats, like the VOR or Open 60's.

A fat boat can go slower and be less wet, but a slow boat cannot go faster even if the ones that like fast boats don't care about getting wet just because they are going faster. They have just to have the right equipment to have fun. On my boat if I go on a beam reach with some waves, if I go at 6K I have a dry boat, if I go over 8k, i start to have a wet boat, even if I don't care

Just to show you what I mean, another movies with the fast Salona 35, that on moderate conditions is a dry boat but when going fast on hard conditions become a wet boat...but as you can see by the faces of all that are sailing it, nobody seems to care:

https://www.youtube.com/watch?v=eU6YqYnys_o

Stage Glénans - Force Sète à Marseille - Vidéo Dailymotion

This are movies taken on Glenan stages. Glenan is the biggest and most famous European sayling school (founded in 1947). Some of the the best professional sailors and some big NA made stages there or monitor stages. The school information about boats is huge due to the big knowledge of their members and they have chose the Salona 35 and 37 as their offshore boats for advanced courses. they say about the Salona 37:

"The Salona 37 is a boat with a sharp hull that Glénans chose for his very good compromise between performance and comfort. Built for offshore sailing it is seaworthy and offer a good safety margin whatever the sea conditions. The Salona offers an obvious pleasure at the big steering wheel, that also allows a great control over the boat with fine trajectories."

Now, as Robert had pointed out, all is relative, this is the French way, they like fast, light, safe, rewarding boats. If we were talking about a British sail school or American sail school, they would chose probably other boat for giving several days offshore stages.

So, in the end, chose a good boat, one that goes with your character, light, medium or heavy and go sailing.

[Southern Star]

Mirage Gecko, as I found out on a similar thread in the multihull section, you are on shakey ground suggesting that boat/bow design comparisons are more valid based upon the LWL, rather than LOA!

Cheers!

Brad

[Jim Cate]

Originally Posted by seacap

I don't belive those 2 videos offer a valid comparison. The Rustler is broad reaching and the other is hard on the wind.

I own a Bristol Channel a Cutter. Plumb bow slab sided and as easy and dry a motion as you would care for.

Amazing how designs have gone full circle, except for the flat forward section of the newer designs that rattle your teeth out. Bow sprites anyone?

This is an interesting opinion! We have had three close friends with BCC's, and all three reported that when loaded for long term cruising, the boats are very wet sailors. Perhaps it is the lading, who knows?

Jim

[DeepFrz]

The Salona was doing a lot of hobby horsing. Didn't look like a comfortable boat to be on, IMO.

The Rustler needed a few more deck drains.

[wingssail]

Definitely wetter going to windward in any kind of waves, but worth it if you have to sail to weather, and, despite the old saying that "gentlemen" don't do it, quite often you will be stuck with either pounding to windward under power, (miserable, in my opinion) or sailing and getting wet.

What happens is this: The bow slices off a piece of the wave, throws it up in the air, where the wind blows it back onto the deck. It can be quite a bit of water, at times. Even my boat, which does not have a plumb bow, can land six inches of water on the foredeck, which is then rushing back towards us. We duck for cover behind the dodger, and hopefully stay dry. The helmsmen, if we are not on the vane, gets wet.

But we can go upwind at 40 degrees and make miles in any direction. We can sail, in other words.

These designs were developed for racing boats, they work. In my opinion, they are superior. If you want to motor, get a powerboat, if you want to sail, get one that will: fine bows, light weight, and keep the weight out of the ends, which means, amongst other things, no big arch aft with a dingy hanging from it.

[DeepFrz]

Keep the weight out of the ends you say...

https://www.youtube.com/watch?v=9wgO9JJ4s-o#t=18

[Terra Nova]

DF--you practically need scuba gear on those boats.

[Stumble]

Things change at 25kn of boat speed. Wild oats at 8kn is ben dry.

[wingssail]

Originally Posted by DeepFrz

Keep the weight out of the ends you say...

Yes, 'tis a thing of beauty I'd say, watching Wild Oats at speed like that. Slicing rather than pounding, not coming to a full stop on each big wave, like some tubs I've sailed. Glorious!

It is wet? Sure is, at 25 knots. But a bluff bowed, heavy ended vessel hobby horsing at 3-4 knots would be pretty uncomfortable too.

If you want to stay dry, slow down, or better yet, stay ashore.

Anyhow, DF, I don't quite get your point.

[OceanSeaSpray]

Originally Posted by Brob2

I enjoyed this discussion very much so thanks for that and Polux for that beautiful video and soundtrack.

Eric, that was a great post, and it led me to your nordkyndesign website where I have spent much time over the last couple of days reading your thoughts on this exact topic, as well as others, and I am much richer for it. I found it very interesting and informative.

Thanks all!

Thank you for your kind note.

The type of design and shape of the forward sections make a huge difference to performance and, as Polux commented, if performance is available, you can take it or not. You have more options, but this also makes a big difference to safety, because yachts become really dangerous if they can't sail any more when the sea breaks in high winds.

When it comes to "comfort", if I match the angle and speed of a traditional cruiser sailing hard on the wind... I heel half as much (or less) as they do to develop the power and I pitch less because the bow doesn't stop and lift as the hull attempts to plow through.
They are hard-pressed, straining everything and throwing spray around, while I hardly feel I am sailing. If a gust comes through, they put the lee rail under; I just point higher. It is night and day.

We have learned many things in the design of yachts in the past 30 years. Modern ones certainly look different, but they also sail and handle very differently both up and downwind and there is no need to go to giant extreme racing machines to experience it.
A yacht doesn't need to be ultra-light to sail very well, but it can't be exceedingly heavy either and shape/configuration do matter a great deal.

Eric