Rudder shape ?

share hints, tips and experiences
User avatar
trebor
Posts: 958
Joined: Mon Jan 02, 2012 1:53 pm
Location: West Midlands
Contact:

Rudder shape ?

Post by trebor » Sun Aug 09, 2015 4:05 pm

What is considered the best shape for a Rudder blade ?

The Rudder blade on Sprint, which I assume is same for all Minisails, the leading edge is angled back from vertical, quite a bit actually, I have altered angle of mine so it is almost vertical.
Class legal issues do not apply, I will make blade "shape" and length width etc considered most efficient.
Robert
Minisprint 4230
Tinker Traveller 160
Mirror 61147 Anastasia
http://www.aquabatdinghy.co.uk

Nigel
Posts: 1238
Joined: Wed Jul 12, 2006 9:51 am
Location: Thornbury SC, Bristol

Re: Rudder shape ?

Post by Nigel » Sun Aug 09, 2015 6:12 pm

don't know the answer but I did think this looked rather exotic -

http://www.ebay.co.uk/itm/Fixed-rudder- ... 3aaf461c7e

JimC
Posts: 1716
Joined: Sun Oct 03, 2004 10:24 pm
Location: Surrey
Contact:

Re: Rudder shape ?

Post by JimC » Sun Aug 09, 2015 6:33 pm

The current fashion seems to be vaguely like that but with the tip under the centre of the board so that there's a reverse curve in the trailing edge.

User avatar
trebor
Posts: 958
Joined: Mon Jan 02, 2012 1:53 pm
Location: West Midlands
Contact:

Re: Rudder shape ?

Post by trebor » Sun Aug 09, 2015 7:00 pm

Nigel, could be useful for dealing with fishermen.

I am sure I read somewhere the Rudder blade should be no more than 2 thirds of centre/dagger board ?
Robert
Minisprint 4230
Tinker Traveller 160
Mirror 61147 Anastasia
http://www.aquabatdinghy.co.uk

Rupert
Posts: 6254
Joined: Thu Sep 16, 2004 8:40 pm
Location: Cotswold Water Park

Re: Rudder shape ?

Post by Rupert » Sun Aug 09, 2015 8:47 pm

On a boat like the MS, a simple rectangle will be fine, and far easier to make a nice cross section, which is where the current rudder is very poor.
Rupert

roger
Posts: 3026
Joined: Mon Sep 20, 2004 12:08 pm
Location: Frome Somerset UK

Re: Rudder shape ?

Post by roger » Sun Aug 09, 2015 10:31 pm

Hornet 191 Shoestring,
Hornet 595 Demon awaiting restoration
Hornet 610 Final Fling
Hornet 353

User avatar
trebor
Posts: 958
Joined: Mon Jan 02, 2012 1:53 pm
Location: West Midlands
Contact:

Re: Rudder shape ?

Post by trebor » Mon Aug 10, 2015 5:50 pm

Wow, figures look impressive.
Robert
Minisprint 4230
Tinker Traveller 160
Mirror 61147 Anastasia
http://www.aquabatdinghy.co.uk

GAv
Posts: 80
Joined: Wed Sep 29, 2010 1:34 am
Location: N Essex
Contact:

Re: Rudder shape ?

Post by GAv » Mon Aug 10, 2015 6:29 pm

My Wooden Sprite rudder fits the pintails on the Monaco Minisprint hull, but I can't remember what the rudder tiller was like when I had a Minisprint 11 but would make an uneducated guess that they are the same. :x

Nigel
Posts: 1238
Joined: Wed Jul 12, 2006 9:51 am
Location: Thornbury SC, Bristol

Re: Rudder shape ?

Post by Nigel » Tue Aug 11, 2015 8:19 am

trebor wrote:Wow, figures look impressive.

but..... they seem to be quoting research on the fin "tubercules" (i.e the whale fin) rather than testing the "Turbocle" rudder's performance directly

I cannot see why increasing the surface area would reduce straight ahead drag but someone with your skills should be able to knock up a blade easily enough and do some testing - that is the only way to find out really

JimC
Posts: 1716
Joined: Sun Oct 03, 2004 10:24 pm
Location: Surrey
Contact:

Re: Rudder shape ?

Post by JimC » Tue Aug 11, 2015 9:17 am

trebor wrote:Wow, figures look impressive.
If you look more closely I'm not entirely convinced that all the things they quote translate into advantages on the race course. For instance being able to put the rudder over harder before it stalls may actually be slower rather than faster because of all the extra drag from the rest of the hull if you turn too fast. We already know that in most circumstances people over use rather than under use the rudder.

User avatar
trebor
Posts: 958
Joined: Mon Jan 02, 2012 1:53 pm
Location: West Midlands
Contact:

Re: Rudder shape ?

Post by trebor » Tue Aug 11, 2015 1:06 pm

The only independent discussion was on the y and y forum In 2012, the consensus was, needed more testing, manufacturer claims narrower blade achieved with this design, due to reduced cavitation
Last edited by trebor on Tue Aug 11, 2015 5:59 pm, edited 1 time in total.
Robert
Minisprint 4230
Tinker Traveller 160
Mirror 61147 Anastasia
http://www.aquabatdinghy.co.uk

roger
Posts: 3026
Joined: Mon Sep 20, 2004 12:08 pm
Location: Frome Somerset UK

Re: Rudder shape ?

Post by roger » Tue Aug 11, 2015 5:33 pm

There is one I know of being used on a Hornet, probably not a large enough sample to be useful but they were positive about it. They probably would have to be as they own 50degree sailing.
Hornet 191 Shoestring,
Hornet 595 Demon awaiting restoration
Hornet 610 Final Fling
Hornet 353

User avatar
trebor
Posts: 958
Joined: Mon Jan 02, 2012 1:53 pm
Location: West Midlands
Contact:

Re: Rudder shape ?

Post by trebor » Tue Aug 11, 2015 6:09 pm

The basis of this design, is taken from nature, the humpbacked whales fins are substantially narrower than other marine creatures of comparable size (Dolphin, Shark etc).

I wonder how many they have sold ?
The designs been out there for a long time now, are their any newly designed dinghies using it?
I know a lot of classes would not be able to use this rudder shape, but their are plenty of classes with out restrictions.
One of the contributors on y&y forum said this would be ineffective below 5 knots and would probably be slower, also ineffective above 30 knots, thats me out then :D
Robert
Minisprint 4230
Tinker Traveller 160
Mirror 61147 Anastasia
http://www.aquabatdinghy.co.uk

User avatar
trebor
Posts: 958
Joined: Mon Jan 02, 2012 1:53 pm
Location: West Midlands
Contact:

Re: Rudder shape ?

Post by trebor » Mon Dec 14, 2015 7:07 pm

I am going to try Tubercules, combined with a Chord.

I hope I will not be breaching someones patent ?
Robert
Minisprint 4230
Tinker Traveller 160
Mirror 61147 Anastasia
http://www.aquabatdinghy.co.uk

realnutter
Posts: 212
Joined: Mon Aug 03, 2015 11:18 pm

Re: Rudder shape ?

Post by realnutter » Mon Dec 14, 2015 7:19 pm

trebor wrote:I am going to try Tubercules, combined with a Chord.

I hope I will not be breaching someones patent ?
Don't think Mother Nature takes out patents....
Matt

Int Moth K2992

Post Reply