Hull shape and sleeping peacefully at anchor

[o1011o]

Every boat is a bundle of compromises and flat bottoms are a common one in the realm of the shoal-draft micro and pocket cruisers that I'm interested in building. There are plenty of discussions I can read through about the sailing characteristics of sharpies and Bolger boxes, but what about the practical issue of comfort at rest? I want to do some extended coastal cruising and I'm certain I won't have a sharpie hull heeled over to its optimal profile while I'm trying to sleep on the water.

I hear arguments from two opposing camps about this issue but rarely details of the kind of conditions that brought these experiences about. It's either, "Sharpies pound! They'll knock your teeth out and the flat bottom is a drum played by the angry hand of Poseidon!" or "I've sailed a sharpie for years and always sleep like a baby!" Is this a simple case of person A only ever anchoring out in rough water rather than someplace protected, and person B only ever stopping on glassy still water and/or being deaf? Or is there more to a hull shape that affects this?

[Larks]

Sounds like person A is expressing an uninformed opinion without experience and person B is talking from experience.

If the flat bottom is submerged you won’t have a noisy night and if you’re at anchor you’ll swing to the breeze so wave motion will pass around your bow. If the waves are big enough to lift the boat out of the water and slap the flat part of the hull you’re anchored somewhere that you probably shouldn’t be and you’re better off being kept awake anyway.

I’ve had noisy nights on full keel boats while securely tied up in a marina berth with the wind from the stern quarter causing the wave motion to slap annoyingly under the transom.

[stromborg]

I keenly remember a long sleepless night anchored out aboard my round-bottomed pocket cruiser, just about the time I got used to the motion an errant wave would slop particularly loudly in the bilgeboard trunks and just like that I was awake again. It was a poor place to anchor for sleeping, most nights onboard I sleep just fine.

[David G]

Yes, round bottoms are more apt to be rolly under the right (wrong?) conditions. While flat bottoms are more prone to be slappy. But, all else being equal, I'll choose the latter to sleep aboard.

[Breakaway]

Any small, light boat is going to be noisy. Its really just a matter of degree and personal acceptance.

kevn

[Mike V.]

Phil Bolger specifically mentioned that boats like Black Skimmer can pound at anchor making sleep difficult.

[o1011o]

Larks, it does seem like an excellent point that weather rough enough to make sleeping difficult should probably not be faced while unconscious!

It also makes sense that any small boat can be loud at anchor, and in the wrong conditions that any boat could make all manner of slaps and whallops. I would imagine that Bolger's boxy designs would be the worst for this, optimizing as they do for volume and efficient use of ply over most other things. While I have a fair bit of experience on boats I've never slept aboard and this advice is really helpful.

[Lemsteraak]

I've always loved the sound of lapstrake boats in waves. There is also something magical in the sound of water against wood.

You guys are right about Bolger boats. The worst I had for anchoring was a fiberglass Dovekie with a perfectly flat bottom and very flat sides. Fiberglass just doesn't sound as good so that was a boat you wanted to beach, so I second that suggestion.

[Edward Pearson]

You've got to define and understand 'flat bottom'.

A boat may have a flat central mid section instead of a V'd pair of garboards for reasons of weight saving, ease of construction or sitting upright on a beach. A Welsford Walkabout for example.

It is however tapered to fine points fore an aft and also cambered or rockered longitudinally. Such a boat has a 'flat bottom' only in one dimension instead of three when you say 'box'. Only true rare 'flatties' are 'flat bottomed' and then only in two dimesions. Bolger never drew a box boat.

It's important to also be aware that flatness which might give rise to pounding and an uncomfortable motion if the increase in secondary stability is too rapid, isn't the case when single chine boats have an immersed chine. The whole surface is underwater, no audible pounding occurs and the chines can also reduce roll speeds with their turbulence. If the fore and aft parts are narrow, there isn't much to pound even if they are flat transversely. If you look at many of Bolger's boats not only are the chines immersed but they are relatively long and thin in proportion.

Broadly, for what you're looking at - ultra shallow light shoreline dinghy type cruising, the best would be something like a Ness Yawl. You want a double ended, long, thin boat. This achieves a shallow V bottom become round at the bilges, a symmetrical fore and aft waterplane and a narrow horizontal and vertical waterline entry. The waves can't get hold of it fore and aft or diffracted waves beam on relative to others. Heave motion is proven least with a shallow V rather than round. Getting yourself low in the boat at the center of pitch whilst also having a low freeboard cabinless boat for minimal windage for the least side to side slatting completes the picture. While a heavy mast reduces ultimate stability, it can at anchor slow roll speeds, as can a mizzen, which is what fishing boats retained after they moved to engines: the mizzener's or 'mizainers' in France, a name still retained with the Ilur after it regained it's lug and dropped the mizzen! Increasing your displacement increases initial inertia to movement but ultimately conflicts with draft or trolley weight etc at this small shallow size. There'a a choice there: the less you rely on absolute displacement for inertia to movement, the more you have to use form to reduce wavemaking resistance. A boat will lift more and tip (roll) less on a beam wave if it's beam profile is more steep than the wave face in question. That's why narrow 'unstable' sail and oar type boats simply bob while a flatty rolls to the same wave. A narrow vertical and horizontal entry and exit angle cleaves a wave before it meets the midsection. A blunt ended boat below or above the waterline doesn't do this but can travel more efficiently at higher froude speeds.

Often you will read that a wide assymetrical waterplane aft (achieved with a wide 'low' transom - typically seen on planing boats) resists downward motion that in turn stops the bow lifting in frontal waves. I have read this in several books. I have not seen empirical evidence for this. It's my experience that in small boats, the opposite is true. With a planing hull form, if the stern can't imnmerse the bow lifts even more. A symmetrical double ended boat that allows the stern to immerse is more comfortable in motion both at anchor and in use. It's a hydrodynamicallty slower waterplane shape though at higher speeds when heeled. It's another choice. Your 'best boat' is not necessarily going to be the fastest one.

The Tirrik...an Oughtred double ender (smaller version of the Ness Yawl) is the most comfortable boat I've experienced. You're broadly looking for a round/ b bottom dinghy with a 16ft long waterplane x 4 waterline beam with minimal windage. It taught that that boats that chase speed loose other desirable attributes. A dinghy 6ft gunwale/ 5ft waterline beam will hold up to gusts better: it's a more relaxed sailer, but the waves start to get hold of it. Given that you are able to find sheltered crooks in the coastline invisible to big boats and you're also going to have it pointed into most waves you could likely afford a 'moderate' transom and still have a comfortable boat.

I personally am going off lap noise as I get older. I find it an intrusion to the 'peace and quiet' although it gives audible feedback as to what the boat is doing. But that's a personal thing you'll know if you do or don't like it. It's also worse for fishing and increases slow speed wetted area but will improve dryness and slightly reduces roll speeds.

[Nicholas Scheuer]

One aspect of both Dovekie and Shearwater in which I've slept, or tried to, many, many nights at anchor is their pronounced habit of "sailing" around their anchor, like almost 90-degrees out to either side. This presents the hull abeam of the seas, which is a whole nuther can of worms beyond "pounding".

[Breakaway]

Great post, Ed. Thank you for sharing your expertise!

Kevin

[Ian McColgin]

Some boats really tack on the anchor or mooring. In straight forward conditions, this can be alleviated by setting two hooks on a nearly eight point (90 degrees) spread. Have suitable chafe gear and run the starboard anchor to port and the port anchor to starboard. If the waves are across the wind or current, you may need to have the hook off the bow doing most of the work and your second hook belayed to an aft or midships cleat to twist your boat into the waves.

G'luck

[Edward Pearson]

You've also got to look at the boat in profile and consider the central area of windage on the topside half (cabin, spars, fore and aft hull height) to the central point of lateral area below the waterline.

If you look at Falmouth Working Boat design...the boats are hove too and drift to leeward while oyster dredging. They have the sails adjusted just so and are actually sailing the boat exactly sideways. This is achieved by balancing the wind and lateral area pressure points. The deep forefoot stops these boats falling off the wind and their close to symmetric freeboard fore and aft with little sheer etc has over time got them perfected for sitting and staying exactly 'side on' as they move over the banks in the Fal estuary. It was this attribute with the Itchen Ferries (they also oyster the same way at the base of Southampton water) that made for good cruising boats that hove too in bad weather reliably.

On a small boat at anchor you want the center of pressure of the topsides, spars, cabin etc to be aft the center of lateral area so that the boat naturally weather cocks to it's rode. And the more aft the better. If you look at Rowan, McMullen had the sense to make his boom tent higher aft for this reason. A boat with dropped mast and raised mizzen and symmetrical fore and aft windage and rocker, low lop side height and no cabin of course goes along way to a satisfactory arrangement. In high winds, boats like this still sit still. The lack of any raised forecabin especially helps by my observation. Ultra light long thin boats with low total windage also put very little total pressure and snatch forces on the anchor rode and don't need the latest and greatest anchor either. Total forces are much smaller, in fact as small as they can be.

Also every boat will have a wavelength that simply causes resonance plus there are places that due to water movement creating upward pressure waves are always uncomfortable places. The visitor moorings off Yarmouth, IOW are like that.

[Nicholas Scheuer]

Tried all those tricks, and more, Ian. The utterly flat bottoms of Dovekie & Shearwater, in addition to their very shallow draft really promote their sailing to & fro at anchor.

[WI-Tom]

In my experience, a small enough boat with a shallow enough draft can tuck so far into the tiniest, most sheltered coves, that waves are negligible or non-existent. Of course, this is facilitated by avoiding tidal waters if you don't want to have to keep moving your boat around. Luckily, I live near the Great Lakes. Tides sound like they are pesky niggling things that complicate pretty much everything.

I slept ashore here, but could have slept aboard VERY comfortably.

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[P.I. Stazzer-Newt]

There's a lot to be said for the lightweight catamaran - slap/pound/roll not much.

Then there's the wind-rode v tide-rode problem

[Edward Pearson]

God has even made the rocks clean and smooth edged for you Tom. Harmonious with your smooth strip planked hull.

[WI-Tom]

God has even made the rocks clean and smooth edged for you Tom. Harmonious with your smooth strip planked hull.

Yes, but those pesky Canadians wouldn't let me in this summer!

Edit to add: I suppose you can't really call what I do being "at anchor"...

Tom

[john welsford]

God has even made the rocks clean and smooth edged for you Tom. Harmonious with your smooth strip planked hull.

Smoothed by ice sliding over them. That makes one think a bit.

John Welsford.

[john welsford]

Edward has made a number of very relevant points here. I could go on at great length, but in brief I have designed small cruisers that have, nominally, flat bottoms. As he points out, very fine forward, with the stem well immersed, sometimes with wide sterns, but the effect on hydrodynamics of those wide sterns are moderated by my carrying the rocker further aft than the traditional sharpie hull. This, at speed, causes the stern to squat which presents the bow at an angle of incidence that will lift the boat up onto the plane. A boat set up like this tends not to have "forced mode" when attempting to plane, will transition very smoothly and is quick midrange, but wont have the same ultimate top speed. Tradeoffs, as always. But a side effect of that wide flat bottom aft is that the boats self damp in both roll and pitch, and that, getting back to Toms original post, is very helpful when sleeping aboard.

John Welsford

[John B]

Our sabot tender keeps me awake with its slapping from its bow chine, it's a terrible thing from that point of view. None of the round bilge dinghies do.

[Woxbox]

Sitting in flat-bottomed Terrapin right now. It's dead calm but there won't be any noise if the wind does pick up because 8 inches of draft allowed me to slip into one of the Chesapeake's many little pond like hidey holes.

But even in open water, the heavily built yet narrow bow doesn't make much noise.

In Lake Ontario earlier this year.

20200721_142249.jpg

[Peter K]

I never found a way to shut my Bolger micro up.
Even pulled up to the shore the slightest ripples would find a place on the bottom to slap against.

[o1011o]

Ed - That's a wonderful in depth reply, thank you. I am particularly fond of double-enders like the Ness Yawl so it's good to hear that they have the qualities of comfort you mention as well. I'll be rereading what you wrote a few times to make sure I've absorbed it all.

tom151 - A fine point about remembering the adaptability of the human animal. Still, I'll try not to make things harder for myself than necessary.

John W. - It was actually your boats that really got me thinking about comfort! As my mind sort of orbited around what kind of qualities I was after I looked at really fast boats, and then boats with maximized volume, and then boats with the highest righting angle, and then the boats that just looked saltiest....Pathfinder and Pilgrim stuck out to me as boats that would be actually good at being boats, period. It's easy to get hyper-focused on one metric or another and forget that it's all a compromise.

Dave - I was hoping you'd weigh in! Your Terrapin is what got me thinking that flat bottom shapes could in fact be beautiful and capable. I'd guessed that the narrow sections bow and stern would reduce noise but I'm glad to hear it from the source.

I better put a signature down here so I'm not just a string of numbers. -Tomas

[gilberj]

Mr. Bolger always drew the bow at the waterline. this was to improve maneuvering I think, but they do pound at anchor, at least all the folks I have talked to spoke of this. My Meadowlark has the bow immersed, and does not pound at anchor, or when sailing. Mr. Herreshoff designed the slightly larger stern and transom to reduce tacking at anchor. She does not tack at anchor either.

[Canoeyawl]

Some boats really tack on the anchor or mooring. In straight forward conditions, this can be alleviated by setting two hooks on a nearly eight point (90 degrees) spread. Have suitable chafe gear and run the starboard anchor to port and the port anchor to starboard. If the waves are across the wind or current, you may need to have the hook off the bow doing most of the work and your second hook belayed to an aft or midships cleat to twist your boat into the waves.

G'luck

I often set up a spring line right on the anchor rode to "adjust" for the current, which can be very different than the wind.
A "stiff" boat can be an damned uncomfortable thing at anchor in a cross sea...

[Andrew2]

Seem to remember that peeps that had slapping problems with flat bottoms used some sort of bundle of rope tied under the hull to interupt the ripples that slapped.
I will let you know later, as my Micro derivative will be on the water before Xmas.

[o1011o]

Andrew2 - I've heard about similar solutions with rope or foam or even a fender tied under. It probably looks silly but it certainly seems like it would help. I'm glad to hear you're ready for the water soon, that's always an exciting time!

gilberj - I'm glad you mentioned that, I have been curious about the immersed vs. waterline-level bow on the various sharpies I've seen. Atkins seems to have a fair few sharpies with an immersed bow, I'll roll on over to their site and take another look.

-Tomas

[Jay Greer]

There are a vast number of designs that will fit your requirement for an easy rider at anchor. Flat bottoms do have a marked tendency to slap or pound depending on the amount of chop. A good design should not have a tendency to do this to any great extent. But if motion or sound changes in the night it is a good alarm that the position of the boat should be checked.
Also a little sound can be comforting as well. I like a boat that does not wish to sail around its mooring so, my recommendation is that you do two things, read L. Francis Herreshoff's "The Complete Cruiser" Then study his book "Sensible Cruising Designs". Books by Uffa Fox is a place to land as well.
Jay

[schoonerpacket]

I've got a Michalak multi-chine hull in a cat boat and we spin like crazy at anchor. It's not unpleasant but it does keep you awake as the moon moves from one port to the next. I'm told it's a feature not a bug.

[Woxbox]

I've got a Michalak multi-chine hull in a cat boat and we spin like crazy at anchor. It's not unpleasant but it does keep you awake as the moon moves from one port to the next. I'm told it's a feature not a bug.

Rigging a bridle will cut it way down. I always used them on my multihulls, which exhibit the same behavior.

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[Paul G.]

In responses to the OP sharpies can be both settled and slappy depending on how much they displace. I have found that all boats are pleasant in calm water but all thing being equal, bigger is usually better as conditions degrade.

[John B]

I've got a Michalak multi-chine hull in a cat boat and we spin like crazy at anchor. It's not unpleasant but it does keep you awake as the moon moves from one port to the next. I'm told it's a feature not a bug.

That's a function of the rig position, windage forward. If you wanted to mitigate it you'd be looking at ways to either reduce it or more likely shift windage aft. Shifting the anchor fulcrum forward via bowsprit or fairlead works, A sentinel will also help.

Our old girl is a 1908 gaff rig boat that was converted to bermudan by the time we bought it. I stayed with that rig and put double furlers on the bow. After I did that she became a sailer at anchor. I rigged a block to shift the anchor rode out to the bowsprit end and ran a sentinel/anchor buddy/angel, and that worked.
Later I removed all that rig and converted to gaff with the result of more static 'sail area' aft in the long boom, shorter mast etc and she became docile at anchor without shifting the rode or the sentinel.

[Ian McColgin]

Not all catboats are alike here. Marmalade was utterly psychotic if you held her nose by anchor, mooring, or bowline with any sail up. She could do multiple gybe-tack cycles in a couple of heartbeats. But sail down and she lay quietly. Very differently, that catboat at Mystic that takes people out is stunningly calm moored to the dock with sail up. Might be hull shape. Might be battenless sails. Might be both.

[Jay Greer]

Sitting in flat-bottomed Terrapin right now. It's dead calm but there won't be any noise if the wind does pick up because 8 inches of draft allowed me to slip into one of the Chesapeake's many little pond like hidey holes.

But even in open water, the heavily built yet narrow bow doesn't make much noise.

In Lake Ontario earlier this year.

20200721_142249.jpg

Tell us more about your boat Woxbox. It reminds me of an International 110 hull.
Jay