Sailing - keel foil

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keel foil

Printed From: Laser 28 International Class Association
Category: Laser 28 General
Forum Name: Sailing
Forum Description: Everything on sailing the boat
URL: http://www.laser28.org/forum/forum_posts.asp?TID=136
Printed Date: 14 May 2024 at 5:15am
Software Version: Web Wiz Forums 11.03 - http://www.webwizforums.com

Topic: keel foil

Posted By: Chris Ross
Subject: keel foil
Date Posted: 03 January 2007 at 5:21pm

compukeel had a kit listed for the laser 28 keel. Has anyone faired their laser 28 keel using the compukeel molds?

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Chris Ross

Replies:

Posted By: fatjohnz
Date Posted: 08 January 2007 at 10:15am

Hi Chris, Do you have any more information on keel fairing? I made templates for my previous 24 foot keel boat using a program that generates plotpoints for a given NACA foil number. I've been interested in doing the same for the laser but I'm not sure what the design spec was for the keel and rudder. Anybody got any info on what the shape is supposed to be? thx, john

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the freak flag is flying

Posted By: Chris Ross
Date Posted: 08 January 2007 at 5:43pm

what program are you using? I thought I found the naca numbers on a website... I'll see if i can find that site again.

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Chris Ross

Posted By: Bill Brock
Date Posted: 08 January 2007 at 8:17pm

If you have the NACA airfoil number, I can give you the dimensional profile to make your own templets. You do not need a program if you can do a simple xy plot on a piece of cardboard. It is not difficult. Among other things I am an Aeronautical Engineer.

Posted By: Chris Ross
Date Posted: 09 January 2007 at 2:02pm

http://www.compukeel.com/uniboats.htm

there seems to be a couple of naca foil numbers mentioned in their universal template pdf. I think the laser 28 pattern is the universal foil pattern.

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Chris Ross

Posted By: fatjohnz
Date Posted: 09 January 2007 at 4:00pm

Right, like Bill said, its not that hard. Someone sent me a spreadsheet where you plug in the airfoil number and the chord length and increment and you get a (y) offset per (x) increment of the chord. Tape some graph paper on a sheet of foam core, graph 20 plot points and viola, cut out the template. Of course need multiple templates....

Do we all agree that the keel was designed to be faired to an airfoil number? And the rudder as well? thx, john

p.s. I'll send you the spreadsheet if you're interested...

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the freak flag is flying

Posted By: Chris Ross
Date Posted: 09 January 2007 at 9:42pm

sounds good on the spreadsheet. I was going to get a cross section foil shape from my keel by using a wire (in 4 or 5 places) and then compare that shape to some of the naca shapes. I was simply going to choose the closeest one for a template.

I emailed the owner of RAGS, a laser 28 with a faired keel. He said the keel matched the compukeel template closely and the only thing that needed to be corrected was a flat spot he found with a straight edge. I 'm going to check my keel tomorrow.

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Chris Ross

Posted By: fatjohnz
Date Posted: 10 January 2007 at 2:36pm

I wonder if RAGS would send you a paper tracing? I can't find anything yet that specifies whether a NACA shape was used for the keel/rudder and if so, which one. Class rules specify that a measured Laser 28 is supposed to be 'the same' as the others. No specs on what that is though. john

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the freak flag is flying

Posted By: Chris Ross
Date Posted: 10 January 2007 at 2:57pm

I sent RAGS an email about the templates. There was a PDF on the compukeel link with the "universal foil shapes" These shapes are the the foils RAGS used I believe. But, you are right, I don't know what the foil shape is supposed to be. The best bet would be to call bill layton.

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Chris Ross

Posted By: Chris Ross
Date Posted: 10 January 2007 at 4:44pm

i looked at 4 laser 28 keels, 3 of them were asymmetrical and one of them was faired. My boat was in the former group. judging by how the other 3 differed, it will be difficult to estimate what the shape was supposed to be.

I guess it's time to start playing with naca sections in xfoil. I have played with Open foam to crudely test sail shapes, maybe I'll play with that too. I'm guessing a lamanar flow foil shape would be ok at the base, then maybe a turblent flow shape at the tip? I'll have to look at the expected leeway angles on the polar charts.

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Chris Ross

Posted By: dmarkc
Date Posted: 03 February 2007 at 6:28pm

Apologies for butting in on your topic. I am about to become a Laser 28 owner and would love to be able to access the Members Area. Please can you tell me if this is possible? Or perhaps lend me a user name and password!