New Posts New Posts RSS Feed: Tell me about T foil rudders.
  FAQ FAQ  Forum Search   Register Register  Login Login

Tell me about T foil rudders.

 Post Reply Post Reply Page  <1 2345>
Author
iGRF View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 07 Mar 11
Location: Hythe
Online Status: Offline
Posts: 5173
Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 10:09am
Originally posted by Daniel Holman

Yes you have to be chest deep and holding the boat singlehandedly into a big shore dump to slot the tfoil in from underneath.


Yes, If the rudder blade and the foil are a unit construction, but what if the horizontal foil were part of the gantry and fixed to a forward only direction?
Back to Top
iGRF View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 07 Mar 11
Location: Hythe
Online Status: Offline
Posts: 5173
Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 10:13am
Originally posted by Peaky

Foils at the bow, like canards, are destabilising. if the bow lifts it will continue to lift, and if the bow goes down it will continue to go down.
Makes you wonder how submarines ever surface when they reverse the bow plane?
Back to Top
getafix View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 28 Mar 06
Location: United Kingdom
Online Status: Offline
Posts: 2066
Post Options Post Options   Quote getafix Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 10:20am
Originally posted by iGRF

Originally posted by Peaky

Foils at the bow, like canards, are destabilising. if the bow lifts it will continue to lift, and if the bow goes down it will continue to go down.
Makes you wonder how submarines ever surface when they reverse the bow plane?


because submarines surfacing or diving is only marginally impacted by the attitude of their external fins and a lot more about bouyancy....
Back to Top
getafix View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 28 Mar 06
Location: United Kingdom
Online Status: Offline
Posts: 2066
Post Options Post Options   Quote getafix Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 10:32am
Originally posted by Peaky

Foils at the bow, like canards, are destabilising. if the bow lifts it will continue to lift, and if the bow goes down it will continue to go down.


OK, I get the science behind that statement but.... A week or two ago I was chatting to a naval architect friend and he was speculating that we might see rudders ahead of keels on the new monohull AC designs. The reasoning being that this would further enable the 'bow down' hydrofoiling attitude which he said improved aerodynamics (of the 'vehicle' when 'flying' through the air) and the lifting of the crew section of the hull (potentially the weightiest bit) out of the briney and to minimise surface area when in the air.

thoughts?
Back to Top
davidyacht View Drop Down
Really should get out more
Really should get out more


Joined: 29 Mar 05
Online Status: Offline
Posts: 740
Post Options Post Options   Quote davidyacht Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 10:33am
Originally posted by Daniel Holman

Yes you have to be chest deep and holding the boat singlehandedly into a big shore dump to slot the tfoil in from underneath.

Do you have to slot the foil from underneath, the N12's have pivoting blades in stocks?  I appreciate that the T foils act as a brake in the half up position.


Somewhere between lies and truth lies the truth
Back to Top
ifoxwell View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 05 Jan 06
Location: Hoo
Online Status: Offline
Posts: 643
Post Options Post Options   Quote ifoxwell Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 10:36am
This was my take on it as far as 12's go... happy to be corrected if others think differently, I'm no expert on the subject


N12 3441
Back to Top
andymck View Drop Down
Far too distracted from work
Far too distracted from work


Joined: 15 Dec 06
Location: Stamford
Online Status: Offline
Posts: 334
Post Options Post Options   Quote andymck Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 8:25pm
I first remember T foils appearing in moths. some of the later Magnum designs. These I think were fixed to try and reduce nose diving. I remember Simon Nelson trying a moth one on a N12 back then.
I think there is a big difference between N12 and I14 use of T foils. On the DCB we tended to have it switched on almost all the time. It did control pitch very well and you could induce a bow up position especially to get the nose over small waves before then going for more lift for a faster more level planing mode. This reacted very much in the same way as outboard trim on a RIB.
Once going it was just a case of sitting as close to the rudder a you could. As a result we moved back earlier. The boats with less rocker would need to back off of they had a nose diving tendency.
The dihedral swept back and up foil induced stability in a similar way to light aircraft. It also reduced the weed issues as a wiggle got rid of any. The N12 foils are set closer to the surface than I14, and I think at lower speeds the stern wave effect is important.
We rarely got to the point we needed to back off on the foil, which is not what I hear from I14 sailors who with greater speed can generate more lift. I wonder if the t foil reduces the extreme wheelies you see in 18ís
To get an idea of loads we were breaking fittings with about 500kg rating and the ones we ended up with were about double that.
We certainly got on the plane earlier and got longer than non t foils. It also allowed heaviier teams to be a little more competitive.

Andy
Andy Mck
Back to Top
Peaky View Drop Down
Really should get out more
Really should get out more


Joined: 15 Nov 08
Location: United Kingdom
Online Status: Offline
Posts: 2604
Post Options Post Options   Quote Peaky Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 18 at 1:01am
Originally posted by getafix

Originally posted by Peaky

Foils at the bow, like canards, are destabilising. if the bow lifts it will continue to lift, and if the bow goes down it will continue to go down.


OK, I get the science behind that statement but.... A week or two ago I was chatting to a naval architect friend and he was speculating that we might see rudders ahead of keels on the new monohull AC designs. The reasoning being that this would further enable the 'bow down' hydrofoiling attitude which he said improved aerodynamics (of the 'vehicle' when 'flying' through the air) and the lifting of the crew section of the hull (potentially the weightiest bit) out of the briney and to minimise surface area when in the air.

thoughts?

Hmmm, I don't see a general aerodynamic benefit to being bow down. The cats were bow down due to a rule limiting the range of play in the rudders as I understand it. Not sure I fully understand the rest of the argument - the lift of the combined foil set up has to be longitudinally in the right place, but that won't require a forward rudder. A forward rudder would be friskier though, likely leading to more small movements which is slow, unless a very good control system was fitted to filter out unnecessary action.

The Bethwaites experimented with a bow mounted T foil rudder on the 49er. There
Back to Top
Peaky View Drop Down
Really should get out more
Really should get out more


Joined: 15 Nov 08
Location: United Kingdom
Online Status: Offline
Posts: 2604
Post Options Post Options   Quote Peaky Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 18 at 2:18am
Originally posted by iGRF

Originally posted by Peaky

Foils at the bow, like canards, are destabilising. if the bow lifts it will continue to lift, and if the bow goes down it will continue to go down.
Makes you wonder how submarines ever surface when they reverse the bow plane?
Could give a long answer to that, but this ain't the place!
Back to Top
ifoxwell View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 05 Jan 06
Location: Hoo
Online Status: Offline
Posts: 643
Post Options Post Options   Quote ifoxwell Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 18 at 8:44am
Originally posted by andymck

 On the DCB we tended to have it switched on almost all the time.

Hi Andy
Thanks for your input, what kind of profile do the DCB and other quick 12's use...?
Ian
N12 3441
Back to Top
 Post Reply Post Reply Page  <1 2345>

Forum Jump Forum Permissions View Drop Down

Bulletin Board Software by Web Wiz Forums® version 9.665y
Copyright ©2001-2010 Web Wiz
Change your personal settings, or read our privacy policy