Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 24-05-2008, 23:03   #1
Registered User

Join Date: May 2007
Location: Hawaii
Boat: Cross 38 Trimaran
Posts: 109
keel winglets

Hi folks,
I have recently purchased a Cross 38. I was talking to Jeff Turner about his fathers boat Thesis and he mentioned she had winglets on her minikeel and rudder. Does any one have knowledge of this type of mod? Jeff mentioned it added about 10 points to her pointing ability.
Thanks
Red Horse
__________________

__________________
Red Horse is offline   Reply With Quote
Old 24-05-2008, 23:40   #2
Senior Cruiser
 
Alan Wheeler's Avatar

Cruisers Forum Supporter

Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
Images: 102
What do you mean by "points"? do you mean degrees??
I am not sure how it would add that much if it is degrees. The reason winglets are used on some racing keels is for reducing or stopping the vortex that spirals off the bottom of the keel. The vortex creates drag and reduces lift. So if the reduction of both of those adds to the ability to point higher, then yes you can. Pointing a further 10deg is a massive gain that I really doubt a winglet would provide. But then, I am no boat designer, so.....
__________________

__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 24-05-2008, 23:48   #3
Registered User

Join Date: Apr 2008
Location: Manchester Washington
Boat: Irwin- Barefoot 37CC (Custom MK V) "Quest"
Posts: 159
I don't believe it. Pointing ability refers to the angle of the relative wind on the sails when sailing to windward, and any modification to the keel or rudder would be to reduce the angle of leeway and that's not the same thing. There have been many mods to the keel that actually do that like having articulating rudders at the fwd and aft edges of the keel, the triangular athwart-ship cross section keel such that the windward side of the keel when heeled produces a greater airfoil curve in the horizontal plane than the leeward side, and the winglets which increase your draft when heeled and because of a greater airfoil shape on the bottom of the wings, they are supposed to give the boat a little lift to windward which in actuality reduces slip or leeway.

Any of these modifications to the keel would reduce leeway by there design but because of their increased frontal area resistance,and increased wetted surface resistance would slow the boat slightly which would cause a corresponding increase in the leeway. So I don't think there is any gain, and if I am wrong it would be measured in fractions of a degree and certainly not 10 points.

If the winglets in question were added as aftermarket add ons, then the increase in draft and ballast would make the boat stand straighter, and that would have a definite affect on pointing ability, but 10 points is still excessive.
__________________
svquest2 is offline   Reply With Quote
Old 25-05-2008, 00:24   #4
Registered User

Join Date: Dec 2007
Posts: 340
End Plate??

Quote:
Originally Posted by Red Horse View Post
Hi folks,
I have recently purchased a Cross 38. I was talking to Jeff Turner about his fathers boat Thesis and he mentioned she had wing-lets on her minikeel and rudder. Does any one have knowledge of this type of mod? Jeff mentioned it added about 10 points to her pointing ability.
Thanks
Red Horse

Because the mini keel is such a low aspect foil some add an end-plate to increase its efficiency. I would suspect that wing-lets would not be as effective plus possibly more prone to damage.
__________________
cat skin hat
catty is offline   Reply With Quote
Old 25-05-2008, 00:25   #5
Registered User

Join Date: May 2007
Location: Hawaii
Boat: Cross 38 Trimaran
Posts: 109
Cross winglets

Sorry, I meant degrees. I will query Jeff and see if its possible to elicit some more info about the winglets. Maybe I can find out who designed them. I have a friend with a stretched Crowther 33 who couldn't out point Thesis when following him into the harbor once. The owner of the Crowther is very race oriented. Of course we may be comparing apples to oranges.
Red Horse
__________________
Red Horse is offline   Reply With Quote
Old 25-05-2008, 00:39   #6
Senior Cruiser
 
Alan Wheeler's Avatar

Cruisers Forum Supporter

Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
Images: 102
I guess the question of pointing would depend on what degree does the boat pint now. If was say 60 and now can point to 50, then yes quite possible. Even say 40 to 30 is a do'er. But 30 to 20 is asking a bit much.
Quote:
some add an end-plate to increase its efficiency.
I imagine the winglets are some form of an end plate. Either would do the same thing for making the keel more efficient.
I remember one (or was it more) Americas cup year, some teams used winged keels. The idea was two fold. To stop the vortex and to also add vertical lift to the boat. The idea was that as the boat tacked, the wings lifted the boat up out of the water slightly and made a point of effort that the boat wanted to turn on. But I don't think that part worked so well. I think I can remember they had issues in one of the legs. Either upwind or down wind, can't remember which. But it upset the balance of the boat to the point of not being an advantage.
__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 25-05-2008, 00:59   #7
Registered User

Join Date: May 2007
Location: Hawaii
Boat: Cross 38 Trimaran
Posts: 109
I think what Jeff meant was a 10 degree total in increased pointing ability. As for the other issues mentioned as we say in aerospace every thing is a trade off. Jeff took a few pictures when Thesis was out for survey I'll ask him to post them to me and put them on the forum if I can ever figure out how to post photos.
Red Horse
__________________
Red Horse is offline   Reply With Quote
Old 25-05-2008, 09:26   #8
Senior Cruiser
 
sandy daugherty's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: near Annapolis
Boat: PDQ 36 & Atlantic 42
Posts: 1,178
A PDQ 34 I knew had inward turning plates on its minikeels. With the trade-off to wetted surface drag, it didn't seem to make a lot of difference. I read somewhere that a sharp 90 degree edge at the bottom of the keel had some stop-plate effect in tank testing, but I have no authority to cite.
__________________
sandy daugherty is offline   Reply With Quote
Old 25-05-2008, 10:14   #9
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,152
If it was a wonderful idea then more modern custom built racers would have it, and they don't. What you do see in modern racers are a lot of very deep, high aspect ratio bulb keels which adds to the boats righting moment and provide more efficient lift.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 25-05-2008, 10:30   #10
Marine Service Provider
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
We have investigated the idea of adding small winglets to the bottom of the keels and in upwind conditions the performance would increase slightly and the pointing would improve with 1 to 2 degrees but in all other conditions the extra drag created lowered the speed , the vortices or whirlwinds are small , so small that the possible advantage is just not worth it.
My 2 cents worth
Greetings
Gideon
__________________
fastcat435 is offline   Reply With Quote
Old 25-05-2008, 10:41   #11
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,152
I agree Gideon, it is probably best just to keep it simple. Otherwise it is yet one more thing to break or to start worrying about.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 25-05-2008, 11:35   #12
Marine Service Provider
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Quote:
Originally Posted by David M View Post
I agree Gideon, it is probably best just to keep it simple. Otherwise it is yet one more thing to break or to start worrying about.
Hallo David That is always our principle unless we get very good speed or weight gains from it , there has to be a real advantage to go a complicated route otherwise KISS.
It is hard enough to keep a yacht going without any extra burdens , the od thing is ( I have found out the hard way ) things always break when far away from civilization you are the one that has to fix it nobody else can do that for you.
Greetings

Gideon
__________________
fastcat435 is offline   Reply With Quote
Old 25-05-2008, 11:58   #13
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,152
Yes, thats kind of the thing about it. If you are out in the middle of nowhere and something breaks, regardless of how much money you have to pay someone else to do it, if you are the only one available, then guess who gets to fix it?
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 25-05-2008, 12:19   #14
Marine Service Provider
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Let me guess You or in my case Me

Greetings and have a good day

Gideon
__________________

__________________
fastcat435 is offline   Reply With Quote
Reply

Tags
keel

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Swing Keel Jennybug Monohull Sailboats 11 15-10-2012 21:01
Fin Keel? Long Keel? Jeff? bob_deb Monohull Sailboats 89 13-03-2012 12:28
New Keel? Drexel Engineer Construction, Maintenance & Refit 10 11-08-2009 17:25
Center board vs keel vs twin keel vs twin centerboard jscott Monohull Sailboats 32 26-03-2009 15:48
Keel discussion RandyAbernethy General Sailing Forum 13 10-01-2006 19:19



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:29.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.