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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Kaufman 47 cutter, anyone have anything on these boats?
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Thread: Kaufman 47 cutter, anyone have anything on these boats? Reply to Thread
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Topic Review (Newest First)
4 Days Ago 05:38 PM
jerryrlitton
Re: Kaufman 47 cutter, anyone have anything on these boats?

Quote:
Originally Posted by Jeff_H View Post
I respectfully suggest that you may not be correctly understanding the term 'Depowering'. Depowering does not mean the same thing as shortening sail. The term Depowering refers to changing the shape of the sail rather than the size of the sail. As you may know, in order to generate drive (forward forces) except when running, a sail must also generate side forces as well. Those side forces are why boats heel and make leeway. By and large, the rounder the sail shape, the greater the forces, both drive and side force.

As the wind builds you get to a point that the boat is going about as fast as it can and so generates excess drive. At that same time, it is also producing excessive side force and heeling.

One way to deal with that is to shorten sail. But a simplier more calibrated way, is to flatten the sail and reduce its angle of attack. The process of flattening the sail and reducing the angle of attack is what is meant by depowering. While large jibs can be depowered a little by tightening the backstay to take sag out of the forestay, and by tightening the halyard to flatten the sail, and by moving the jib car aft a little to open the head of the sail and reduce the angle of attack at the head, the options are far more limited than on a mainsail expecially on a boat with a 'bendy mast'.

Jeff
Jeff, we may be in heated agreement however in my experience the angle of attack as we know it is the angle in which the relative wind meets the airfoil. This does not change with airfoil shape however the characteristics of the relative wind and airfoil can change with airfoil shape. For instance in an airplane, I can directly change the shape of the wing by extending my leading edge devices (slats) or trailing edge devices (flaps) however this does directly change my angle of attack. This is mostly done with my primary pitch control which is my elevator (for and aft stick movement). Now very very generally speaking a fat curved wing gives me more lift (thrust to you) during slow speed ops and when I deploye my leading and trailing edge devices I am changing the shape of the wing so I can operate at a higher angle of attack without losing efficiency during slow speed operations. Now move this horizontal wing vertically now we call it a sail. (a wing is a wing is a wing) now the lift is now called thrust. And my elevator that I used to control my angle of attack is now called a rudder on a sailboat. However in addition of the rudder I can move the boom independently of the boat to change angle of insidence which changes the angle of attack without changing boat heading or in the case of the old Navy jet the F8 the fuselage pitch angle. Instead of leading and trailing edge devices you can change the shape of the wing (sail) by raking the mast, changing the luff, tightening the back stay etc and I am sure many other ways BUT these are not directly changing the angle of attack, only changing the characteristics of the airflow because of a change in angle of attack which you changed by changing boat heading relative to the wind of moving the boom or traveler. I understand that I am speaking of very generalities but the concept is sound.

Jerry.
5 Days Ago 12:16 PM
SailRedemption
Re: Kaufman 47 cutter, anyone have anything on these boats?

Redemption - Mast Stepping: http://youtu.be/mCVJN6cF-kU

- Ronnie...on the geaux
5 Days Ago 10:34 AM
SailRedemption
Re: Kaufman 47 cutter, anyone have anything on these boats?

The last of them... Finishing the time lapse now!

- Ronnie...on the geaux
5 Days Ago 10:33 AM
SailRedemption
Re: Kaufman 47 cutter, anyone have anything on these boats?

More pictures (:

- Ronnie...on the geaux
5 Days Ago 01:39 AM
SailRedemption
Re: Kaufman 47 cutter, anyone have anything on these boats?

Time lapse is taking a while.. Hopefully it finishes by the time I wake up in the morning to head back to work on the ship. Only the first part of the video is done, so we may just have to settle for that haha!

I'll post the remaining pictures in the morning!
5 Days Ago 01:33 AM
SailRedemption
Re: Kaufman 47 cutter, anyone have anything on these boats?

Quote:
Originally Posted by sandy stone View Post
Beautiful boat. I think John Kretchsmer has an article about refitting his own K-47 in this month's issue of SAILING.
BTW, is that at Lake Catherine Marina?
Thank you Sandy, thanks for the tip on that article! I looked it up and luckily it was online, though not sure if it was different from the magazine or not.

And yes it is(was) Lake Catherine Marina. It has been sold and now is Lake Catherine Island Marina. Have you been there?
6 Days Ago 10:09 PM
sandy stone
Re: Kaufman 47 cutter, anyone have anything on these boats?

Beautiful boat. I think John Kretchsmer has an article about refitting his own K-47 in this month's issue of SAILING.
BTW, is that at Lake Catherine Marina?
6 Days Ago 05:22 PM
SailRedemption
Re: Kaufman 47 cutter, anyone have anything on these boats?

Thanks for the nice words guys!

Here is the coins I used for my mast step. One is a Hong Kong 10 dollar coin and the other is a 5 peso coin from the Philippines. Both of which I acquired from my cruising there in the maritime academy. Both worth about $1.40.. I figured they were a better penance than a regular dollar coin. That and I couldn't find one at 3 banks before I put the mast on haha!

- Ronnie...on the geaux
6 Days Ago 01:21 PM
christian.hess
Re: Kaufman 47 cutter, anyone have anything on these boats?

moar pics! jajaja
1 Week Ago 12:06 AM
Jeff_H
Re: Kaufman 47 cutter, anyone have anything on these boats?

Congratulations, Those are really wonderful boats. There was one named 'Dove' that lived near here that had made all kinds of long passages. A beautiful and fast boat.

Enjoy owning her.
Jeff
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