Refueler
Well-Known Member
One day I hope to get round to the West Archi ...
Plumb bow stupidity
- Thread starter geem
- Start date
One day I hope to get round to the West Archi ...
oz-1
Well-Known Member
Your beautiful boat
dunedin
Well-Known Member
You are getting confused again. Just because a Beneteau cruiser chooses to widen out above the waterline to increase bow cabin space, this does not mean it is necessary with a plumb bow. Just look at all the traditional old gaffers for example. Or modern boats with a more performance orientation.
Need to be careful reading selective “yacht design pages online”. I suspect few of the actual designers who are designing successful modern boats bother to post on these website.
And of course there is no single “best” bow shape. Longer LWL is generally better in almost all circumstances.
But whether a fine wave piercing bow is faster than a scow bow like used on many new IMOCA racers depends on many trade-offs.
geem
Well-Known Member
Seriously, I am not confused. Just been studying the boat next to us that fits exactly what you can read online from yacht designers.Ben Oceania 38.1 it's bow is exactly as I described.
Interestingly, like lots of 1990s boat the original 381 had the slapping stern problem. The newer 38.1 has a stern that no longer sits just above the water. It's far more abrupt. They have lost waterline length at the stern and replaced it at the bow. The 38.1 has over a foot longer waterline length than its predecessor and should be easier to live with at anchor as a lot less slap, slap. So it's not all bad
[194497]
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If you look at the lines of a Vertue, the plan shape at the waterline is much the same as at deck level, with a similar fineness at the point of the bow. But the point of the bow is obviously that much further aft at the waterline.
Now imagine drawing the shape at the waterline forwards until the point is in the same place as at deck level. The waterline entry will inevitably be finer that the point of the bow at deck level.
Supertramp
Well-Known Member
I think old plumb bows (like FWB's in #72) are very different to new ones. There may be similarity above the water but the hull forms beneath are very different. As will be the displacement relative to waterline length.
Plumb bows (or more or less so) were normal on Scottish inshore fishing boats although Norwegian counterparts had more rake and flare. Look further afield and there is huge hull form diversity in working and leisure boat designs between areas. I think a lot has to do with local conditions, experience and individual boat building yards.
Nowadays I sense that a concept forms on paper or PC and is turned into a workable form by the design team for global use. And given the expected use, they do it pretty well. Although it makes me smile to see bowsprits and plumb bows on modern designs (although not as graceful as FWB's).
Plumb bows (or more or less so) were normal on Scottish inshore fishing boats although Norwegian counterparts had more rake and flare. Look further afield and there is huge hull form diversity in working and leisure boat designs between areas. I think a lot has to do with local conditions, experience and individual boat building yards.
Nowadays I sense that a concept forms on paper or PC and is turned into a workable form by the design team for global use. And given the expected use, they do it pretty well. Although it makes me smile to see bowsprits and plumb bows on modern designs (although not as graceful as FWB's).
[194497]
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The hull forms of designs like the Vertue were heavily influenced by the need to build them in carvel timber. If you look at the lines, all the planks and frames would have easy curves. That naturally generates an elegant and moderate overhang. Plumb bows are possible in carvel with a deep, gently curved forefoot (as in the absolutely gorgeous Heard 28 above) but a shallow hull with a plumb bow would be very tricky in a big, carvel boat.
Daydream believer
Well-Known Member
That is odd, because, after reading your post I was at the marina. I looked at some boats on the hard today. A Sadler 34 looked decidely fat against a Hanse 345. A Halberg 34 likewise against a Benny 323. I looked at several boats of past & newer designs ( cannot recall all the models) & I cannot say I saw any that backed your statement. In fact a newer model hanse 31 than mine, had a marked hollow in the hull as the lines approached the bow. I started to wonder if there was a moulding error. But it was even both sides. I have seen it on other late models.
geem
Well-Known Member
Words from Farr on one of their very high performance new canting keel designs
The plumb or relatively upright stem angle's typical of today's boats are a product of fashion that has aligned itself with the common box rule type race boats we wish to emulate. When unconstrained by rules, designers are free to look for advantages in alternative concepts. In the case of this boat two major areas have pushed us in the direction of a more angled stem. The first is the desire to tack a removable masthead genoa forward of the forestay. This sail would be used in light air when racing under handicap systems that do not unfavorably treat such a sail. When sizing that masthead sail the resulting foot length positioned its tack well forward of the forestay requiring some form of structure to support it. The structure alone could have been provided by some other means like a portion of fixed bowsprit tube. When looking at the required structure we considered that a section of extended bow slope could also provide an added volume and flare to the topsides forward. The reserve buoyancy in that added geometry will be a benefit in waves and high speed running conditions where nose diving can be a concern. When discussing these possibilities with our client we decided together to pursue the less fashionable but perhaps more technically correct solution.
Daydream believer
Well-Known Member
If one wants to see a different bow design then I suggest that one looks at Richard Mathews Oystercatcher 35.
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Supertramp
Well-Known Member
Indeed. Eye catching, interesting and probably fun to sail. But I note it has no anchor provision at all. Is that because it will come up via the bottom of the boat?!
Then again, it probably won't be chartered. Yet.
Daydream believer
Well-Known Member
I have seen it sitting on a mooring in the Orwell when not in use.
Laminar Flow
Well-Known Member
I think, or rather I know, it is incorrect to compare classical plumb bows with their contemporary variants.
The classical boats with plumb bows had comparatively little saliant keel and to assure some windward ability, they were given a deep fore foot. The steeper the stem, the greater the greater the lift producing area under water. In this context someone posted a picture of a Brixham trawler, which type perfectly illustrates my point. The considerable volume below the waterline would have provided sufficient reserve buoyancy.
On these boats the anchors were retrieved on cat heads either side of the bows. Additionally, the bows were often covered with some sacrificial timber sheathing to prevent structural damage to the planking from the anchors or the odd growler, for that matter.
Another apples and oranges debate. I do love a bit of fruit.
I do think the Heard 28 is an absolutely lovely boat. It should however be remembered, that it is an interpretation of an inshore oyster dredger. In how much securing reserve buoyancy in heavy seas was a necessity, is open to debate.
Other than stretching the DWL and maximizing ones expensive slip length, the modern variety of the plumb bow has little practical purpose in a cruising boat, except perhaps to maximize marketing response by quoting styles that reflect contemporary racing craft. The last point is hardly anything new: designers were equally inspired by the bloated guppy looks of the IOR or the elegantly undernourisched and underbuoyed sterns prior.
Best, A.
The classical boats with plumb bows had comparatively little saliant keel and to assure some windward ability, they were given a deep fore foot. The steeper the stem, the greater the greater the lift producing area under water. In this context someone posted a picture of a Brixham trawler, which type perfectly illustrates my point. The considerable volume below the waterline would have provided sufficient reserve buoyancy.
On these boats the anchors were retrieved on cat heads either side of the bows. Additionally, the bows were often covered with some sacrificial timber sheathing to prevent structural damage to the planking from the anchors or the odd growler, for that matter.
Another apples and oranges debate. I do love a bit of fruit.
I do think the Heard 28 is an absolutely lovely boat. It should however be remembered, that it is an interpretation of an inshore oyster dredger. In how much securing reserve buoyancy in heavy seas was a necessity, is open to debate.
Other than stretching the DWL and maximizing ones expensive slip length, the modern variety of the plumb bow has little practical purpose in a cruising boat, except perhaps to maximize marketing response by quoting styles that reflect contemporary racing craft. The last point is hardly anything new: designers were equally inspired by the bloated guppy looks of the IOR or the elegantly undernourisched and underbuoyed sterns prior.
Best, A.
Refueler
Well-Known Member
Hang on guys ... RESERVE BOUYANCY is not in the water ... its above water to provide a 'RESERVE' to cause body to provide bouyancy when forced to submerge as in pitching.
The best example is the forecastle of a ship ... raised from maindeck level ... but as ships got bigger - the need for an extra deck to create this was replaced by an upward gradient to the deck.
The best example is the forecastle of a ship ... raised from maindeck level ... but as ships got bigger - the need for an extra deck to create this was replaced by an upward gradient to the deck.
boomerangben
Well-Known Member
Apart from your reserve buoyancy statement, I agree. new designs with plumb bows which don’t extend very far below the water line are different to the traditional designs where a deep forefoot would have been the forward end of a long straight shallow keel which was relatively easy to build from timber. Fin keels weren’t a thing back then and would be a pain in the backside on a fishing boat.
Modern X bow designs on offshore supply vessels are demonstrating that perhaps traditional flared bows can have too much reserve buoyancy in the bow and a more comfortable ride is afforded as a result of more modern designs. I would imagine reduced reserve buoyancy in yacht plumb bows would reduce slamming.
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FWB
N/A
Re Laminar Flow member “I do think the Heard 28 is an absolutely lovely boat. It should however be remembered, that it is an interpretation of an inshore oyster dredger. In how much securing reserve buoyancy in heavy seas was a necessity, is open to debate.”
The Heard 28s mould is from an actual Oyster Dredger, not an interpretation. One has crossed the Atlantic, though I agree it is an inshore design.
The Heard 28s mould is from an actual Oyster Dredger, not an interpretation. One has crossed the Atlantic, though I agree it is an inshore design.
Baggywrinkle
Well-Known Member
My perfect boat if it had a roller-furling main and no teak decks.
Plum bow? Like that is a buying decision? Bit of wrap-round stainless steel and sorted.
.... just look at that cockpit and bathing platform - that is a truly perfect platform for sunbathing, watersports, and entertaining friends.
Plum bow? Like that is a buying decision? Bit of wrap-round stainless steel and sorted.
.... just look at that cockpit and bathing platform - that is a truly perfect platform for sunbathing, watersports, and entertaining friends.
Attachments
geem
Well-Known Member
Works beautifully in that swimming pool. We see a lot of those hinged doors set at 45deg here in the Caribbean as the anchorages can be pretty choppy. Sunsail in Antigua had a pile of the platforms in a heap that had failed presumably due to thr bumpy conditions since charter boats aren't using marinas out here too often. It can be fun watching people trying to board their boat over an inclined platform in a chop.My perfect boat if it had a roller-furling main and no teak decks.
Plum bow? Like that is a buying decision? Bit of wrap-round stainless steel and sorted.
.... just look at that cockpit and bathing platform - that is a truly perfect platform for sunbathing, watersports, and entertaining friends.
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[194497]
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In 1962 Phil Bolger designed a RORC ocean racer called Hesperus with long overhangs to exploit the RORC rules, which penalised waterline length. He later wrote:
"Overhangs like this don't make much sense, but like a good many people, I have a perverse liking for their looks. Logically, the waterline should be extended in long, sharp points under the overhangs. There would be more displacement in the ends without much increase in the middle of the boat, so she would be shallower in the middle. Then the cabin sole would have to be higher, with an increase in freeboard to keep the same headroom. The result would be a faster, abler and roomier boat than this one for about the same investment."
Fifty years of yacht design development in one paragraph!
"Overhangs like this don't make much sense, but like a good many people, I have a perverse liking for their looks. Logically, the waterline should be extended in long, sharp points under the overhangs. There would be more displacement in the ends without much increase in the middle of the boat, so she would be shallower in the middle. Then the cabin sole would have to be higher, with an increase in freeboard to keep the same headroom. The result would be a faster, abler and roomier boat than this one for about the same investment."
Fifty years of yacht design development in one paragraph!
geem
Well-Known Member
Phil Bolger designed very simple boats. Many for home construction.
A friend had a 38ft boat he built himself. Inspired by Phil Bolger but to his own design. He is a boat designer and has many very successful small boat designs. His boat is 38ft over the deck and 38ft at the waterline. It's a high volume hull with a carbon daggerboard (8ft draft) and lifting rudder. Our hull is 44ft overall with 35'6" static waterline. We sailed in company with Chris in the Caribbean a number of times. Its not all about waterline length. We are faster on every point of sail. We have a folding prop. Chris had a brunton autoprop, we weigh considerably more and have a lot more sail area. Waterline length alone doesn't make a fast boat. There are so many other factors.