Pros and cons of steel sailboats - Page 351 - SailNet Community
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post #3501 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

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Originally Posted by Dean101 View Post
Here's a question that is probably a little more in line with the thread subject. How badly does a steel boat affect compass deviation compared to other hull materials? And does a steel hull affect autopilot systems that have those compass computers?
No different to ships. To reduce deviation there are two large soft iron masses placed close to the compass (Kelvin's balls) so they dominate the compass effect and other effects are then relatively insignificant.

Electronic autopilots don't need it and most have an auto adjust procedure you follow which can be as simple as motoring around a circle.
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post #3502 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

Kelvin's balls? I know that feeling.
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post #3503 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

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No different to ships. To reduce deviation there are two large soft iron masses placed close to the compass (Kelvin's balls) so they dominate the compass effect and other effects are then relatively insignificant.

Electronic autopilots don't need it and most have an auto adjust procedure you follow which can be as simple as motoring around a circle.
That makes sense. I knew that most compasses have compensators but I really didn't know how effective they actually are. I thought an all metal hull would be much more difficult to compensate for.
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post #3504 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

I received permission from Kim to post the lines of FRANCIS LEE. I thought some of you might be interested. The lines plan is the heart and soul of the design. I would generally not publish the lines but seeing that you have seen so many photos that the hull shape is hardly secret anymore and the fact that I am not afraid of designers who want to copy me, I'm afraid of the ones who don't want to copy me. Here they are. By the way, if you cannot produce a set of finished and faired hull lines you are not a yacht designer.


A little explanation:
This is revision No.8 of a series of preliminary hull lines. There were far more iterations than eight as Kim and I bounced back and forth trying different approaches to the lines. But eight of them were close enough to get a designation. From this Rev. 8 we went to 3D lines with the help of Jim Franken. Jim spotted a flat spot in the stern and I asked him to fix that. Other than that the final 3D lines is what you see here in 2D.

The deadrise you see in this hull was not there when I started. I favored an arc type midsection going tangent at centerline. That's a fast shape. But when Kim chose to go with the red cedar strip planking I knew we would have a timber keelson, i.e. backbone and the depth of the backbone would cut into my transverse floor timbers. Not good. So I added the deadrise to give the boat more bilge depth to accomodate structure we would need.

I think you can see here how I pushed volume into the end of the boat to keep the Cp up. I did not want whimpy, anemic ends that just went along for the ride. I wanted ends that would do work. The rest is just out of my head and the product of a lifetime of sailing, studying and designing a tremendous variety of sailing boats.

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post #3505 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

Awesome. Did you calculate polars for it?
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post #3506 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

Here's the scene as I see it:
It's a party. There is a string quartet playing some Haydn and Mozart pieces. Nice music and everyone is enjoying themselves. Over in the corner by himself sits Beethoven. He looks really bored. He smells funny, bad. He waits until the quartet finishes a pice then walks over, whips out four scoes from his waistcoat and throws them at the 1st violin. The 1st violin looks them over and distributes them to the other musicians. The room is filled with chatter and noise. Glasses clink. The score is Beethoven's Opus 135. The quartet starts in and plays through the first movement. The room begins to go quiet. By the time they finish the fourth movement the room is almost silent. Then they are done, exhausted and the room is truly silent. And it stays silent.

Not sure why I wrote that other than to kind of say, I post those hull lines and the room goes pretty much silent.
Except for Sandy clapping wildly of to one side.

But Beethoven was profoundly deaf by then so he didn't really notice. Not really.
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Last edited by bobperry; 01-29-2014 at 06:39 PM.
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post #3507 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

Sandy:
Yes we have polars. I won't post them. They would just bring on a flood of questions. Most people are not used to reading tabular VPP data. If you Pm me we can discuss it.

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post #3508 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

Not trying to pry, or cause controversy. Just looking at that hull, imagining a high-aspect sailplan, & wondering what a boat like that would do closehauled. Also tacking angles. Wow.
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post #3509 of 5317 Old 01-29-2014
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Re: Pros and cons of steel sailboats

Looks like nice hull balance . She should have a lot of directional stability, but most narrow boats do. High prismatic coefficient should give her a lot of top end speed, in strong winds.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
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Re: Pros and cons of steel sailboats

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Out:
I played in rock bands for 10 years. I stood four feet in front of stacked Fender Dual Showman amps and later stacked SVT Ampegs, two cabinets 4 12's in each. But for some reason my hearing is still acute. Thick head?

Right now, in the office I am listening to Arabella Steinbacher play Prokofiev's Sonata for Violin Solo in D major.

Or is it,,,,a Haydn London Symphony?

My hearings just fine.
My father lead telephone lines to firing artillery in ww2 and had excellent hearing til his late 80s. Now it is not so good. The doctor said it was because of artillery damage in his early 20s, by artillery fire. He said the fine hairs in the ears get damaged. You may find the same by your late 80s .
He hasn't lost a political debate since he stopped wearing his hearing aid.

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