[Public-List] Rudder Shape

Gordon Laco via Public-List public-list at lists.alberg30.org
Wed Feb 22 04:42:09 PST 2017


Good morning Greg,

Surprise, being an apres-400 boat, has a fiberglass rudder, and it’s port and starboard sides are parallel… there is no taper.  The trailing edge is round, but I’ve not touched that for fear of grinding through the glass skin and exposing whatever is inside.  I just live with it.

With regard to the ¾” thickness you’ve remarked on below – strength is the issue and I don’t have advice on that.

Gord Laco #426 Surprise


On 2017-02-22, 2:41 AM, "Public-List on behalf of Greg Roberts via Public-List" <public-list-bounces at lists.alberg30.org on behalf of public-list at lists.alberg30.org> wrote:

    Thanks for all the responses! Gord, I had come to that conclusion
    myself but couldn't find anything online to back up my gut feel.(And
    fluid dynamics is not something I've ever studied so I didn't trust my
    gut...)
    So, no foil is confirmed. Do the factory fiberglass rudders have a
    taper or are the sides parallel?I'm tempted to copy the shape of the
    old rudder: Flat sides that taper to about 3/4" But perhaps the
    trailing edge should be a bit thicker?
    The current plan is to use a 1 1/8" bronze rudder post. Flat strips of
    bronze will be welded on to create the skeleton.Two strips will be
    used to create each spoke. See Jefa.comI'm not copying the pressed in
    rods that the factory used. Every bronze post failure I've heard of
    failed at the holes bored for the rods.
    Regards,
    Greg
    On 2/21/2017 at 9:28 AM, "via Public-List"  wrote:Send Public-List
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    Today's Topics:
    
       1. Re: Rudder Shape (Gordon Laco via Public-List)
       2. Re: Rudder Shape (Bill Boyle via Public-List)
       3. Re: Rudder Shape (Bill Boyle via Public-List)
       4. Re: bottom paint (gordon white via Public-List)
       5. Re: Rudder Shape (Bill Boyle via Public-List)
       6. Re: Rudder Shape (Bill Boyle via Public-List)
    ----------------------------------------------------------------------
    
    Message: 1
    Date: Tue, 21 Feb 2017 10:05:25 -0500
    From: Gordon Laco via Public-List 
    To: Rod Symmes , Alberg 30 Public List --
     open to all 
    Subject: Re: [Public-List] Rudder Shape
    Message-ID: 
    Content-Type: text/plain; charset="UTF-8"
    
    Another interesting thing?  in discussion with Steve Killing, the
    yacht designer who lives near us, and is the fellow who figured out
    how to make those huge America?s Cup catamarans fly by making their
    centre boards curved, I learned that the way to make certain a dinghy
    rudder or centerboard doesn?t vibrate is to make the trailing edge
    straight and squared with sharp corners.  We make the servo blades of
    Voyager self steering vanes that way.
    
    Along the same lines?  I?ve got an original Hasler self steering vane
    in our workshop.  I bought it years ago for the Folkboat but never
    used it?  I keep it to show where Voyagers came from.  The Hasler is a
    fair bird cage of tubes, tiny blocks and lines, but it shows evidence
    of Hasler?s brilliant mind all over it.
    
    Now here?s the point of all this?  Hasler?s servo blades, the part of
    the vane that?s in the water, is NOT foil shaped.  It?s wedge shaped
    with a small radius parabolic leading edge, then steadily widens to a
    squared trailing edge about 1? thick.  This is the same shape used by
    surface piercing hydrofoils of the 1960?s.    interesting, isn?t it? 
    At low speeds it likely makes more drag resistance than a pure foil?
    but at high speed much less, and especially at angles of incidence. 
    Whatever turbulence it ?feels? is swept off the wedge and tumbles in
    futile frustration aft of the squared edge where there?s no blade.
    
    As a maker of vanes I was also interested to note that Hasler resolved
    the issue of making the vane fit various freeboard heights by simply
    making the blade way too long.  The spruce is cheap, and the owner can
    trim it to whatever is required.  Genius.
    
    Gord #426 Surprise
    
    On 2017-02-21, 9:24 AM, "Public-List on behalf of Rod Symmes via
    Public-List"  wrote:
    
        What I remember from aerodynamics in that time period was that
    European car rally drivers prefered the Volvo station wagon over the
    sedan because,  in spite of the extra pounds of glass, they were 2 or
    3 mph faster with that square back end.
        Go figger ?
        Cheers,  Rod
        -------- Original message --------
        From: Michael via Public-List
        Date:21-02-2017 7:37 AM (GMT-05:00)
        To: Gordon Laco , Greg Roberts , Alberg 30 Public List -- open to
    all
        Subject: Re: [Public-List] Rudder Shape
        I always think of Kamm back cars of the late '70's on this
    subject. Kamm
        was an aerodynamic scientist who calculated the drag of building
    in a
        tear drop shape was more than just cutting off the back of the car
        square. Made for a bunch of ugly little cars.
        Michael Grosh
        #220
        ------ Original Message ------
        From: "Gordon Laco via Public-List" 
        To: "Greg Roberts" ; "Alberg 30 Public List --
        open to all" 
        Sent: 2/21/2017 3:27:50 AM
        Subject: Re: [Public-List] Rudder Shape
        >Good day Greg,
        >
        >A foil shaped rudder would do you no good at all? one must
    consider,
        >with our sorts of boats, that the ?foil? has it?s leading edge at
    the
        >forward part of the keel and the rudder is a sort of flap or trim
    tab
        >on that structure, not something on it?s own.
        >
        >The only improvements one could give our rudders would be to
    minimize
        >the ?leaking? of flow from the leeward side to the windward
    between the
        >rudder post and the after part of the keel (already a pretty good
    fit
        >in Alberg 30?s except of course for the troublesome propeller
    aperture)
        >and perhaps a narrower and more squared trailing edge.   The
    thicker
        >rounded trailing edge (when considered in cross section) is not
    so good
        >for minimizing turbulence at the trailing edge.
        >
        >Gord #426 Surprise
        >
        >On 2017-02-21, 12:32 AM, "Public-List on behalf of Greg Roberts
    via
        >Public-List" public-list at lists.alberg30.org> wrote:
        >
        >     Did any of our boats come with a foil shaped rudder?My wood
    rudder
        >has
        >     flat sides and a gentle taper..I'm not sure how much one
    would gain
        >     with a foil given the 3/4 keel,I'm having a hard time
    picturing how
        >     you would handle the tilt when defining the profile.
        >     Regards,
        >     Greg
        >     _______________________________________________
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        >
        >
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    ------------------------------
    
    Message: 2
    Date: Tue, 21 Feb 2017 15:51:14 +0000 (UTC)
    From: Bill Boyle via Public-List 
    To: Greg Roberts ,
     "public-list at lists.alberg30.org" ,
     "public-list-request at lists.alberg30.org"
     ,  Alberg 30 Public List --
     open to all 
    Subject: Re: [Public-List] Rudder Shape
    Message-ID: 
    Content-Type: text/plain; charset=UTF-8
    If you want to close the gap between the keel and the rudder this is
    the product to use.Hawk Marine Products, SlotStrip
    |  
    |   |  
    Hawk Marine Products, SlotStrip
     Manufactures of Marine Products  |  |
    
      |
    I use this on my Classic Moth to close up the dagger board slot.? They
    also have it in bigger sheets to close bigger gaps.? Any keel hung
    rudder would benefit from this.? 
    
    Bill BoyleSlainte #129
          From: Greg Roberts via Public-List 
     To: public-list at lists.alberg30.org;
    public-list-request at lists.alberg30.org 
     Sent: Tuesday, February 21, 2017 12:32 AM
     Subject: [Public-List] Rudder Shape
    Did any of our boats come with a foil shaped rudder?My wood rudder has
    flat sides and a gentle taper..I'm not sure how much one would gain
    with a foil given the 3/4 keel,I'm having a hard time picturing how
    you would handle the tilt when defining the profile.
    Regards,
    Greg
    _______________________________________________
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    ------------------------------
    
    Message: 3
    Date: Tue, 21 Feb 2017 15:51:14 +0000 (UTC)
    From: Bill Boyle via Public-List 
    To: Greg Roberts ,
     "public-list at lists.alberg30.org" ,
     "public-list-request at lists.alberg30.org"
     ,  Alberg 30 Public List --
     open to all 
    Subject: Re: [Public-List] Rudder Shape
    Message-ID: 
    Content-Type: text/plain; charset=UTF-8
    If you want to close the gap between the keel and the rudder this is
    the product to use.Hawk Marine Products, SlotStrip
    |  
    |   |  
    Hawk Marine Products, SlotStrip
     Manufactures of Marine Products  |  |
    
      |
    I use this on my Classic Moth to close up the dagger board slot.? They
    also have it in bigger sheets to close bigger gaps.? Any keel hung
    rudder would benefit from this.? 
    
    Bill BoyleSlainte #129
          From: Greg Roberts via Public-List 
     To: public-list at lists.alberg30.org;
    public-list-request at lists.alberg30.org 
     Sent: Tuesday, February 21, 2017 12:32 AM
     Subject: [Public-List] Rudder Shape
    Did any of our boats come with a foil shaped rudder?My wood rudder has
    flat sides and a gentle taper..I'm not sure how much one would gain
    with a foil given the 3/4 keel,I'm having a hard time picturing how
    you would handle the tilt when defining the profile.
    Regards,
    Greg
    _______________________________________________
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    ------------------------------
    
    Message: 4
    Date: Tue, 21 Feb 2017 11:00:44 -0500
    From: gordon white via Public-List 
    To: public-list at lists.alberg30.org,
     public-list-request at lists.alberg30.org
    Subject: Re: [Public-List] bottom paint
    Message-ID: 
    Content-Type: text/plain; charset=windows-1252; format=flowed
    
    There was discussion at last Saturday's maintenance seminar of bottom 
    paint and I believe prices quoted were between $160 and $200 per
    gallon. 
    I just bought a gallon of Woolsey copper ablative bottom paint at my 
    nearby Tru-Value hardware store for $99.
    - Gordon White, BRIGADOON II (#275)
    ------------------------------
    
    Message: 5
    Date: Tue, 21 Feb 2017 17:28:19 +0000 (UTC)
    From: Bill Boyle via Public-List 
    To: Bill Boyle , Greg Roberts
     ,  "public-list at lists.alberg30.org"
     ,
     "public-list-request at lists.alberg30.org"
     ,  Alberg 30 Public List --
     open to all 
    Subject: Re: [Public-List] Rudder Shape
    Message-ID: 
    Content-Type: text/plain; charset=UTF-8
    
    Well, that didn't stick.?? I'll post the reference to the SlotStrip
    over on the facebook page.
          From: Bill Boyle via Public-List 
     To: Greg Roberts ; "public-list at lists.alberg30.org" ;
    "public-list-request at lists.alberg30.org" ; Alberg 30 Public List --
    open to all  
     Sent: Tuesday, February 21, 2017 10:51 AM
     Subject: Re: [Public-List] Rudder Shape
    If you want to close the gap between the keel and the rudder this is
    the product to use.Hawk Marine Products, SlotStrip
    
    ? 
    |? 
    |? |? 
    Hawk Marine Products, SlotStrip
     Manufactures of Marine Products? |? |
    
    ? |
    I use this on my Classic Moth to close up the dagger board slot.? They
    also have it in bigger sheets to close bigger gaps.? Any keel hung
    rudder would benefit from this.? 
    
    Bill BoyleSlainte #129
    ? ? ? From: Greg Roberts via Public-List 
     To: public-list at lists.alberg30.org;
    public-list-request at lists.alberg30.org 
     Sent: Tuesday, February 21, 2017 12:32 AM
     Subject: [Public-List] Rudder Shape
    ? 
    Did any of our boats come with a foil shaped rudder?My wood rudder has
    flat sides and a gentle taper..I'm not sure how much one would gain
    with a foil given the 3/4 keel,I'm having a hard time picturing how
    you would handle the tilt when defining the profile.
    Regards,
    Greg
    _______________________________________________
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    ------------------------------
    
    Message: 6
    Date: Tue, 21 Feb 2017 17:28:19 +0000 (UTC)
    From: Bill Boyle via Public-List 
    To: Bill Boyle , Greg Roberts
     ,  "public-list at lists.alberg30.org"
     ,
     "public-list-request at lists.alberg30.org"
     ,  Alberg 30 Public List --
     open to all 
    Subject: Re: [Public-List] Rudder Shape
    Message-ID: 
    Content-Type: text/plain; charset=UTF-8
    
    Well, that didn't stick.?? I'll post the reference to the SlotStrip
    over on the facebook page.
          From: Bill Boyle via Public-List 
     To: Greg Roberts ; "public-list at lists.alberg30.org" ;
    "public-list-request at lists.alberg30.org" ; Alberg 30 Public List --
    open to all  
     Sent: Tuesday, February 21, 2017 10:51 AM
     Subject: Re: [Public-List] Rudder Shape
    If you want to close the gap between the keel and the rudder this is
    the product to use.Hawk Marine Products, SlotStrip
    
    ? 
    |? 
    |? |? 
    Hawk Marine Products, SlotStrip
     Manufactures of Marine Products? |? |
    
    ? |
    I use this on my Classic Moth to close up the dagger board slot.? They
    also have it in bigger sheets to close bigger gaps.? Any keel hung
    rudder would benefit from this.? 
    
    Bill BoyleSlainte #129
    ? ? ? From: Greg Roberts via Public-List 
     To: public-list at lists.alberg30.org;
    public-list-request at lists.alberg30.org 
     Sent: Tuesday, February 21, 2017 12:32 AM
     Subject: [Public-List] Rudder Shape
    ? 
    Did any of our boats come with a foil shaped rudder?My wood rudder has
    flat sides and a gentle taper..I'm not sure how much one would gain
    with a foil given the 3/4 keel,I'm having a hard time picturing how
    you would handle the tilt when defining the profile.
    Regards,
    Greg
    _______________________________________________
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    ? 
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