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21-06-2017, 00:14
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#1
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Registered User
Join Date: Oct 2015
Location: Aspen USA
Boat: 10' surfboard
Posts: 148
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Please explain the advantage of an overhang to a longer waterline?
Mahina, Bluewater, and Atom seem to accept designs that exhibit overhang fore and aft.Perhaps this is related to well established distance cruisers taking these designs all over the world despite the seeming weakness. Dashew says go waterline, damn the torpedoes. I am inclined to lean towards extended waterline as an advantage, and excessive overhang as an old age oversight. seems 2 possibilities:
1 extended waterline gives additional float and buoyancy as waves are encountered. starts early essentially, maybe "motion comfort" is impacted, as the movement is following the ocean surface, but deeply slugging and plowing slowly may not be the best long term solution?
2 The long waterline has no reserve in heavy confused seas? perhaps a deep central keel and progressively increasing buoyancy both for and aft causes a smoother movement and gentler action on long passage in larger ocean offshore swell? the perceived benefit of speed gained from waterline is negated by heavier smoother consistent movements that collaborate to stride longer and make miles pass?
Why are Albergs accepted as passagemakers when the waterline is brutally short? Do the just plow on smoothly endlessly in the big offshore swell and storms, and get better and better as it gets rougher and rougher? Does that progressive buoyancy in the ends smooth things out... ORcreate a heavy slam coming down into a bigger wave following the one you just crested?
Do longer waterlines to overall length pitch less,track better and give smoother motion comfort? (I would like to hear yes answer here...)
Yeah overall design and underbody type is a huge factor, but I am really wondering if long waterline to length, and deep ballast designs are simply advancement and improvements?
OR will that larger overhang give me a smooth rise from the front or stern when the nasty odd wave shows up? Is there value in additional boat above the waterline blending the violent ocean waves into more gentle smoother flow?
I will say in my experience in heavy weather a progressive bow with flare and more over all length to shorterwaterline slams very violently into waves when the period gets even slightly off the boat pitch. A longer waterline seems to move straight ahead, and in really big waves just plunge deeply and accept more green unbroken water over the deck, perhaps a worse option, but the scuppers flushed it and progress was smoother. I will admit the sharper bow and longer waterline was simply better in all ways in rugged conditions, but this is in steel motor powered working vessels of +200 foot length dragging gear. Hardly related to sail boats in the 5 to 20 ton range...
Thank you in advance for input.
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21-06-2017, 05:07
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#2
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Registered User
Join Date: Jun 2008
Location: Tampa, FL
Posts: 5,009
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Re: Please explain the advantage of an overhang to a longer waterline?
It has more to do with racing rules from the past than it does deliberate attempts to make boats that are more seaworthy. That, and a lot of people prefer the looks of a boat with some overhang.
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21-06-2017, 05:14
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#3
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Registered User
Join Date: Dec 2016
Location: Brazil
Boat: Custom Swedish Vindö 50 (35 ft)
Posts: 806
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Re: Please explain the advantage of an overhang to a longer waterline?
The overhangs offers no advantages, except perhaps at the bow, for keeping the boat drier going to windward. The lists you mention have a lot of older, well-built boats that have overhangs because that was the way they were designed at the time. They are on the list, not because they have overhangs, but because they stand above their contemporaries in terms of build quality and, today, are affordable cruising boats.
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21-06-2017, 05:18
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#4
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Registered User
Join Date: Aug 2011
Location: Lower Chesapeake Bay Area
Boat: Bristol 27
Posts: 10,425
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Re: Please explain the advantage of an overhang to a longer waterline?
An experienced sailor gave a great explanation for the long overhangs on another thread. I try and find it and provide the link
A couple things he mentioned were more room/area on the bow and bringing in the anchor. I have an old Alberg design and when bringing in the anchor it has room to swing without slamming into the boat.
And I believe buoyancy was mentioned as an asset on the Alberg style boats for things like heavy chain and anchors. Plus a dryer ride possibly.
Also the plumb bow boats with longer LWL tend to slam into the waves in heavier seas whereas the Alberg style boats with the longer overhangs rode more smoothly......
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21-06-2017, 05:39
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#5
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Registered User
Join Date: Dec 2016
Location: Brazil
Boat: Custom Swedish Vindö 50 (35 ft)
Posts: 806
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Re: Please explain the advantage of an overhang to a longer waterline?
True, the overhang at the bow is good for keeping your anchor from hitting the boat as you bring it up, but a short sprit/anchor platform has the same effect.
It's interesting to see Bob Perry's more recent designs- they have almost plumb bows (with a short anchor platform). I'm not so certain the bow overhangs "cut the seas" better or slam less. Even a plumb bow gains buoyancy as it submerges (it's a "V" shape). If you look at old working craft (Channel cutters etc.) it's interesting to see how they have almost plumb bows. Overhangs, as noted above, came into play because of racing rules (they way they measured and rated boats) and as an aesthetic element.
At any rate, it's hard to make an argument for stern overhangs, unless you appeal to their beauty on older boats.
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21-06-2017, 07:17
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#6
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֍֎֍֎֍֎֍֎֍֎
Join Date: Apr 2006
Posts: 15,136
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Re: Please explain the advantage of an overhang to a longer waterline?
One thing I have noticed on several boats with a plumb bow: If you encounter "square" waves or heavy chop, the boat tends to slam and lose momentum every time it plows into one, instead of rising above and through it.
And similarly, I've heard it mentioned that a reverse sloped transom has its greatest amount of buoyancy when it is inverted.[sic]
There's definitely something to be said about long waterlines and more hull speed and paying less in marinas (who gladly charge by the foot for those overhangs) but I suspect "horses for courses" and "moderation in all things" are the way to make these choices.
Well, that and aesthetics, of course.(G)
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21-06-2017, 07:32
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#7
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Registered User
Join Date: Aug 2011
Location: Lower Chesapeake Bay Area
Boat: Bristol 27
Posts: 10,425
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Re: Please explain the advantage of an overhang to a longer waterline?
This is that post I remembered from that other thread. The link to that thread is:
http://www.cruisersforum.com/forums/...ang-15340.html
This post was from Southern Star:
Overhang, especially at the bow, is not simply about looks. Rather, as Robert Perry pointed out (in Robert Badham and Robby Robertson, Sailor's Secrets, International Marine, Camden Maine, 1999 at p. 193:
"Some things, though, begin to look better the heavier the weather gets. Plumb stems are a modern trend. They obviously maximize waterline length, but in a cruising boat do you want to give up a foredeck and make your boat into a submarine for an extra little boost in top end speed? Traditional elements like overhang are traditional because they work. Overhang keeps people dry and provides space to do what foredeck work you have to do."
To his I would add the importance of front overhand in anchoring - have any of you tried to retrieve an anchor in a boat with a plum bow? It is virtually impossible, in most conditions, to avoid banging the anchor into the topsides - even with an anchor roller that extends a short distance past the bow.
The same can also be said about the current trend towards wide transoms and relatively flat underbody shapes. Yes, the flatter hull form can increase speed potential in relatively flat water, but it does so at the expense of a sea-kindly motion: the boat will tend to slam when sailing to windward.
Further, boats with such an underbody design have significantly greater inverse stability - VERY bad in a monohull. Consider the recommendations concerning seaworthiness made in the aftermath of the Fastnet disaster. Witness also various of the original Open 60's that, when capsized, stayed inverted. As you may recall, this forced a rule change that led to canting keels.
Finally, this 'modern' hull form, while having increased initial form stability, also has a tendancy to increase weather helm under heeling once the rather sharp turn of the bilge is sufficiently submerged on the leeward side.
In the result, it is often the purchasers of these more 'modern' hull forms who are slaves to fashion: they want a boat that looks like a modern racing boat; they want the increased interior volume that is created below (they want huge aft doubles and could care less about proper sea berths); they want the home-like look of a wide cabin sole. For this they are prepared to sacrifice a degree (and sometimes a significant degree) of seaworthiness and actual sailing comfort and praciticality.
Brad
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21-06-2017, 08:27
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#8
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Registered User
Join Date: Dec 2014
Location: Clear Lake, TX
Boat: Kadey Krogen 38
Posts: 236
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Re: Please explain the advantage of an overhang to a longer waterline?
An additional comments. As boats with long overhangs heel, the waterline gets longer increasing hull speed potential. Long waterlinea at level were penalized under CCA handicap ratings. Result short waterlines while level in slip for measurement purposes, but much longer waterline when healed. This is also why many of the boats with this design were relatively tender and did not get real stability until the rail was almost in the water.
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21-06-2017, 08:27
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#9
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Registered User
Join Date: Jan 2014
Location: essex england
Boat: offshore 8 meter
Posts: 138
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Re: Please explain the advantage of an overhang to a longer waterline?
hi, i have sailed both, i now sail a 22ft falmouth oyster dredger, 22 ft on deck , 22 ft waterline. ive done 4 atlantic crossings on her and shes a superb boat in rough weather, these designs eg pilot cutters have been around for hundreds of years nelson would recognise them , so they have stood the test of time also hold their course well with long keel ,and more living space for a given length. but i am biased, i love gaffers, nice to reef without having to put her into the wind in 30 ft swell
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21-06-2017, 08:39
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#10
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Registered User
Join Date: May 2007
Location: On my boat, Manhattan, Kansas or LaBelle, Florida
Boat: 45 custom steel ketch-Steelin Time
Posts: 396
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Re: Please explain the advantage of an overhang to a longer waterline?
I would expect it has more to do with what people buy, longer boat length and more deck space sell boats, it makes "bigger" boats for less money and the boat company gets more profit.
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A bad day sailing is 100 times better than a good day at work. www.jheld.mysite.com
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21-06-2017, 08:53
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#11
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Registered User
Join Date: Apr 2015
Location: Lakeland, Florida
Boat: Irwin Citation 34
Posts: 256
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Re: Please explain the advantage of an overhang to a longer waterline?
After many thousands of sea miles on many different boats, I will take a cutter rig, clipper bow and reverse transom in the open ocean over any of the "modern" designs. Every boat design is a compromise, seaworthiness and comfort on the open ocean definitely trumps speed. That's my opinion and I'm sticking to it.
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21-06-2017, 09:24
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#12
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Registered User
Join Date: Sep 2008
Posts: 400
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Re: Please explain the advantage of an overhang to a longer waterline?
"For your life, build no fantail overhang on a craft going offshore."
J. Slocum
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21-06-2017, 09:31
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#13
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Registered User
Join Date: Apr 2007
Location: Marina del Rey, California
Boat: President 43 Sportfish
Posts: 4,105
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Re: Please explain the advantage of an overhang to a longer waterline?
Overhangs increase reserve buoyancy and righting moment, also decrease wetted surface in light air.
__________________
1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
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21-06-2017, 09:32
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#14
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Registered User
Join Date: Sep 2007
Location: Bend, OR
Boat: Brewer designed Pacific 43 in fiberglass. Center cockpit set up for long-distance single handing.
Posts: 472
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Re: Please explain the advantage of an overhang to a longer waterline?
Kadeykrogen38 hit the nail on the head.
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21-06-2017, 09:43
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#15
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Registered User
Join Date: Jan 2013
Location: Anacortes, WA
Boat: Custom 55
Posts: 909
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Re: Please explain the advantage of an overhang to a longer waterline?
I'm firmly in the anti-overhang camp. I've sailed both types offshore, and to my mind, there is no advantage to the overhangs at all.
Ok, maybe the foredeck is drier, but so what? I'd rather slow down for a few minutes while crew's on the foredeck than sacrifice all kinds of boat speed plunging that flared bow into the sea with each wave, effectively stopping the boat.
We had a really interesting study in hull behavior in a marina in Ireland last summer. A gale was passing through, making things quite lively in the marina. Our ultralight, zero overhang 55 footer bobbed around a bit, hardly pitching. Behind us was a 1930's ketch, probably weighing at least triple what we do. That thing sat there pitching around relentlessly, at times nearly scooping water with that long, aesthetically pleasing overhung transom. It was incredible to watch the difference.
This behavior happens at sea too. Sure, they look nice, but as far as I'm concerned, there is basically zero reason for them other than looks or beating some very old racing rule.
TJ
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svrocketscience.com
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