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Old 14-11-2010, 19:44   #1
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Lightbulb Raked-Back Bows

Hi all

Just a design question if anyone has any knowledge...

Raked back bows, faniliar since the days of clipper ships and before, are becoming rar now with the advent of longer waterline, plumber and even reverse bows (on some cats). A good example is the new Norstar 40, really a Nordic 40 IOR era boat that is back in production.

Raked back bows do have advantages like reserve buoyancy. There are some others and if anyone has any design knowledge on the subject it would be very welcome.

Thanks much
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Old 14-11-2010, 19:53   #2
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They also tend to be a little drier, as spray is directed away from the boat.
Raked bows have become less prevalent not just because of the advantages of a lengthened waterline, but also because a plumb bow increases interior volume.
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Old 14-11-2010, 19:55   #3
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Try here: Boat Design Forums
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Old 14-11-2010, 21:11   #4
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Having one myself I know a few advantages.
1) It replaces a bowsprit and adding more sail area.
2) Adds more deck space for anchoring, which helps the anchor from banging the bow.
2) Positive buoyancy.
3) If a little outward curve is added it'll redirect the spray out a bit.
4) it's fun to watch the dolphins while above them.
5) Tends to make the boat more attractive (sleek or streamline).
6) Nice size anchor locker.

Disadvantages are;
1) If you hit something hard you could loose your forestay, same with a bowsprit.
2) Less waterline in relation to OAL
3) Less interior space vs OAL.
4) I have a nack for bumping marina pilings when docking.
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Old 14-11-2010, 21:49   #5
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Bob Perry has often pointed out the biggest single advantage: easier to keep the anchor from banging the bow as you bring it up. The other advantages / disadvantages are relative and depend on the design.
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Old 14-11-2010, 22:33   #6
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Probably tradition plays no small role here, think about making a wood boat, this raked bow shape is just intuitively one way that it would end up.

I think people think of design waterlines a little too much when looking at boat designs. In reality, you sail in waveforms, when you think about this, the raked bow makes more sense. It makes the motion smoother, smoother motion makes you go faster, or at least puke less.
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Old 15-11-2010, 06:55   #7
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Thanks ship shape for the thread, it's very informative...

I agree that a hull to deck joint with bit of outward flair will keep the decks drier and redirect spray outwards. The reserve buoyancy in sailing wave trains keeps the pitching less therefore faster sailing and more comfortable offshore.

Some designers make a valid argument that a plumber bow actually has more reserve buoyancy (more boat below the waterline) and also more wetted area (more drag). However with a raked back stem the argument is that the pitching is less, therefore making the boat sail faster as the sails keep their proper foil to the wind longer!

Our boat has a good bit of rake on the stem and yes, it does not pitch a lot even in bigger headseas with a large anchor on the bow! The underbody helps also...

(And I also hit pilings too often!!)
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Old 15-11-2010, 07:18   #8
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Bob Perry also said that a raked back bow expends less energy when moving over a wave train...
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