[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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------------------------------
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:
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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
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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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http://www.alberg30.org/store/A30supporters.html
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Public-List at lists.alberg30.org
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