Search results

The answer is that it depends. A coal powered electrical plant usually has an efficiency in the range of 30-35%, oil is around 42%, and a good natural gas plant will have efficiencies around 60%. Electric cars have an efficiency of roughly 70-80% (i.e. energy put onto the road / energy taken...

@DDW do you find any practical benefit in letting the main out past square and trying to get some lift when going downwind?

The reference lengths are different.  For the cylinder it's the diameter.  For the airfoil it's the chord length.

They do. The drag coefficients are different, but the total drag force is the same.

It's hard to convince people.  Humans have bad intuitions about drag.  No matter how many times I look at this picture, the fact that these two profiles have the same drag feels wrong to me.  Probably the very different volumes tricking my eye.

Yes, wing loading matters.  If you barely load your wing, there's less induced drag to minimize, and adding winglets is mostly adding parasitic drag.  The rate at which induced drag increases with additional wing loading, though, depends on the aspect ratio. The Whitcomb paper found that: At...

Something to remember about AUSTRALIA II, is that the major innovation in the minds of the designers was the inverted keel shape, not the wings.  By having a longer root chord than tip chord, the center of lift on the keel was lowered.  Getting the low pressure region on the keel further below...

Another approach is a sprit that rotates aft to nest along the sidedeck.  This one from the Paul Bieker Shilshole 27 is a very clean setup, with a bow pulpit built into the forward "bearing."  Something like this could probably be retrofitted on the right boat.  I see no reason it must be...

In the words of Bill Garden: “Every boat can be improved with hindsight.”

Any difference besides the rig, Bull? Nat Benjamin did a Rozinante inspired yawl as well.  The design is called TERN, but I believe he's built several of them.  It's got 18" more beam and fuller ends, not to mention a gaff mainsail.  Not quite as elegant as the original, in my opinion, but...

Yawl Rig?

@hdra, how well does the Reflek's work when heeled?  I've seen several contradicting reports.  One said that it would become unreliable if there was more than 10 deg. of heel. Other places I've seen people say they've had no issues, but they don't mention at what heel angles they've actually...

Sort of.  Mitchell's integral, when combined with a skin friction model (ITTC 57 line, or similar) is surprisingly accurate for evaluating the drag of truly thin hulls: think kayaks, rowing shells, multihulls, etc. For beamier boats, the absolute numbers become less accurate, but the general...

I like the sliding rowing seat that fits over the centerboard case.  Saves the weight of an outboard, and gives you something better than leaning over the side paddling with a floorboard.

How about TEJST, a Swedish sailing canoe? More info here: http://www.lunne.se/lunne/Tejst.html

It's just a NURBS surface.  The shape is more complex in the joint so there's more control points there, which is showing up in the visualization. Meshes for CFD are much denser and more regular.

You're right, those numbers have to be in square feet and pounds.  With a displacement of 21,000 lbs. and 1480 sq.ft. of upwind sail area, that's a DLR of 63 and SA/D = 31. Those numbers seemed, ummm... optimistic, so I checked Bieker's website which gives a more reasonable displacement of...

I like the accommodations on Rocket Science.  A loosened up version of the interior of a 40 footer: aft cabins big enough to warrant the name, a big galley, a spacious saloon, chart table big enough for a full paper chart. One thing I find strange, though, is the sinks in both the aft cabins...

There's a great description of the design concept and construction here, which is a good read if you're interested.

That's the 29 footer, I think.  The extra length helps keep the height from looking ungainly. I actually don't hate the appearance.  It's not pretty, but not all boats need to be pretty.  At least it has the virtue of being unapologetic about what it is.