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New Centreboards #215709
07/10/10 07:04 PM
07/10/10 07:04 PM
Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
stillbitten Offline OP
Pooh-Bah
stillbitten  Offline OP
Pooh-Bah

Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
Hi all,

am about to make a major modification to Thrice Bitten. crazy Have purchased a set of couple of year old design, A class Flyer centreboards and cases cool, which I am going to get put into my 15 year old Faye hulls (it currently has very wide, wider than boyer centreboards) frown .

No surprises that I will get them installed as far back as possible (which is where the back of the current cases is), the interesting bit is that I intend to get them installed vertically (most Mossies angle them back the maximum 10 degrees), so what do you think? confused


Regards Gary.
Mosquito 1830
All opions expressed in this post are mine and mine alone, no assumptions should be made regarding any Associations or Clubs I may be a member of.
-- Have You Seen This? --
Re: New Centreboards [Re: stillbitten] #215710
07/10/10 07:20 PM
07/10/10 07:20 PM
Joined: Apr 2007
Posts: 432
McCrae Y.C. Mornington Peninsu...
S
Simon C Offline
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Simon C  Offline
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Joined: Apr 2007
Posts: 432
McCrae Y.C. Mornington Peninsu...
Hi Gary,

10 degrees forward, port canted out 35 degrees, starboard canted in 26 degrees... Might give me a chance to catch you some time grin grin

On a more serious note... what's the thinking behind verticle? Is it because they were that way in the Flyer or do you have a theory?

Cheers


Simon
Taipan AUS341
Re: New Centreboards [Re: Simon C] #215716
07/10/10 10:43 PM
07/10/10 10:43 PM
Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
stillbitten Offline OP
Pooh-Bah
stillbitten  Offline OP
Pooh-Bah

Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
Hi Simon,

why would you imagine I would have a theory? blush

Well it does seem that all cats that do not have measurement restrictions on distance back that centreboards are placed built in recent years, have vertical centreboards and that incudes the Flyer ones I have bought. As far as I can see the only reason for raking centreboards back is when you want to move your Centre of Lateral Resistance further back and rules do not allow it.

I am hoping that the smaller centreboards vertical will not move CLR forward much if any at all, as the rudder blades will actualy account for a larger pecentage of the CLR, than previously, helping to balance the fact that the tip of the centreboards will be further forward.

Now for the theory grin.
When sailing long sailboards with swinging centreboards as the wind increased we found a effect we called railing up. This was caused by depressing the lee rail of the board on purpose which as the speed increased resulted in the centreboard lifting the board out of the water and helping it to plane, it also allowed you to point higher as you balanced the forces of the increased lift from the centreboard. No surprise I hear you say, you where using the centreboard as a lifting foil. smirk When the wind increased it would flip the board over, to stop this we would rake the centreboard back. smile

My theory, raking centreboards back reduces lift cry. On sailboards we use to even rake them forward in light winds, which increased lift even more, but made them very hard to control crazy.

So there you have it, I hope to get more lift which should improve windward performance grin. But expect it will make the boat twitchier? something I am willing to live with, I hope whistle



Regards Gary.
Mosquito 1830
All opions expressed in this post are mine and mine alone, no assumptions should be made regarding any Associations or Clubs I may be a member of.
Re: New Centreboards [Re: stillbitten] #215756
07/12/10 05:15 AM
07/12/10 05:15 AM
Joined: Jul 2010
Posts: 87
Gold Coast QLD
Damo Offline
journeyman
Damo  Offline
journeyman

Joined: Jul 2010
Posts: 87
Gold Coast QLD
Hi Guys
I'm new to the Mosquito class and I have just started to build my first one. I was Just reading your thread about boards and was wondering if you could point me in the right direction is there a reconmended board and rudder width and length that most people use other than the specs on the rules form?
Thanks smile

Last edited by Boat name TBA; 07/12/10 05:22 AM.

Damien 1820 Raw Prawn (under construction)!!!
QLD
Re: New Centreboards [Re: Damo] #215758
07/12/10 05:39 AM
07/12/10 05:39 AM
Joined: Jan 2006
Posts: 556
Somers, Westernport Bay, Victo...
Peter_Foulsum Offline
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Peter_Foulsum  Offline
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Somers, Westernport Bay, Victo...
Hi TBA and welcome to the swarm. cool I hope that your building all goes to plan and you have your new Mozzie on the water for the start of next season. smile Where do you plan to sail/race and what is your sail number ? Any details would be greatly appreciated for addition to the Mozzie register.

If you don't want to make it public just send me a PM through this forum site.

In terms of centreboard width and length there are many variations but most have a width of around 250 mm and a length just greater than 1 m. My current centreboards are 10 inches wide by 1020 mm long. These were cut down from the original timber boards which were much wider and longer and I have seen no adverse effects. smile

Regards,

Peter


Mosquito 1814
Macka Mozzie
Re: New Centreboards [Re: stillbitten] #215760
07/12/10 06:03 AM
07/12/10 06:03 AM
Joined: Jan 2006
Posts: 556
Somers, Westernport Bay, Victo...
Peter_Foulsum Offline
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Peter_Foulsum  Offline
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Somers, Westernport Bay, Victo...
Hi Gary,

My ancient Mozzie had vertical boards and when I made the change to the 10 degrees rake it made made an enormous difference. grin That little shift in the centre of lateral resitance appeared to reduce the weather helm significantly and allowed me to set the rudders up close to vertical. I also reduced the width at the same time so that may also have had some effect.

Mind you the aft edge of the centreboard case is not as far rearward as the modern Mozzie so that could account for some difference (3305 mm versus 3353 mm allowable)

Jeremy Pearse did some experimentation with "A" class centreboards without much success. Not sure if they were 9" wide but they just didn't have the same tracking ability as the 10" boards. I'm sure Jeremy could give you some clarification. smile

Regards,

Peter


Mosquito 1814
Macka Mozzie
Re: New Centreboards [Re: Peter_Foulsum] #215761
07/12/10 06:06 AM
07/12/10 06:06 AM
Joined: Jul 2010
Posts: 87
Gold Coast QLD
Damo Offline
journeyman
Damo  Offline
journeyman

Joined: Jul 2010
Posts: 87
Gold Coast QLD
Thanks for the reply and feed back Peter. Sail number 1820 (on the plans any way)I currently skipper a Nacra 5.8 out of Cleveland yacht club in Brisbane while i build the Mozzie but I live on the Gold Coast so when the boat is built probberly both places at this stage. I bourght an old hull mould from Jim Boyer recently and the hulls will be under way shortly, I know they are an older design mould but for my first boat these will do fine. Your tips on the foils are much appreciated, I can start to work on these in between the hulls. Time is my biggest problem at the moment so I'll just keep ticking along
Thanks once again and look foward to joining the Mozzie clan
Cheers
Damien

Last edited by Damo; 07/12/10 06:34 AM.

Damien 1820 Raw Prawn (under construction)!!!
QLD
Re: New Centreboards [Re: Damo] #215821
07/13/10 12:30 AM
07/13/10 12:30 AM
Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
stillbitten Offline OP
Pooh-Bah
stillbitten  Offline OP
Pooh-Bah

Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
Hi all,

my new boards are 220 x 1005, effective length 550 under the hull. Old boards where 290 x 965, effective length 510 under the hull.

No doubt placing cases as far back as legal in hull is essential, vertical as opposed to raked 10 degrees I guess I will find out. grin or cry


Regards Gary.
Mosquito 1830
All opions expressed in this post are mine and mine alone, no assumptions should be made regarding any Associations or Clubs I may be a member of.
Re: New Centreboards [Re: stillbitten] #215823
07/13/10 01:53 AM
07/13/10 01:53 AM
Joined: May 2007
Posts: 416
Matt_Stone Offline
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Matt_Stone  Offline
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Joined: May 2007
Posts: 416
am i that bigger of a threat that you have to change your boat around hahahaha

Re: New Centreboards [Re: Matt_Stone] #215824
07/13/10 03:09 AM
07/13/10 03:09 AM
Joined: Mar 2010
Posts: 77
Gippsland Lakes
mitchellsailor Offline
journeyman
mitchellsailor  Offline
journeyman

Joined: Mar 2010
Posts: 77
Gippsland Lakes
Matt you're on the right track, but in fact it is I that have just bought the new sail :P. Time will tell if this is to beat you, Gary or both hahaha.


Mosquito 1750 Bonnie-GLYC / Peninsula

The plan was simple.... Like my brother in law Phil, except this plan just might work!
Re: New Centreboards [Re: mitchellsailor] #215922
07/14/10 11:46 PM
07/14/10 11:46 PM
Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
stillbitten Offline OP
Pooh-Bah
stillbitten  Offline OP
Pooh-Bah

Joined: May 2004
Posts: 1,632
Gippsland Lakes Victoria Aust...
Hi M & M,

my theory is never stop trying to go faster crazy. If I keep moving the goal posts hopefully you whipper snippers won't kick any goals grin.

Oh I have ordered new rudders also. cry


Regards Gary.
Mosquito 1830
All opions expressed in this post are mine and mine alone, no assumptions should be made regarding any Associations or Clubs I may be a member of.
Re: New Centreboards [Re: stillbitten] #215939
07/16/10 05:21 AM
07/16/10 05:21 AM
Joined: Apr 2007
Posts: 432
McCrae Y.C. Mornington Peninsu...
S
Simon C Offline
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Simon C  Offline
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Joined: Apr 2007
Posts: 432
McCrae Y.C. Mornington Peninsu...
Originally Posted by thricebitten
Hi M & M,


So who is the Red one and who is the Yellow one? laugh


Simon
Taipan AUS341
Re: New Centreboards [Re: mitchellsailor] #216492
07/26/10 03:02 PM
07/26/10 03:02 PM
Joined: Jul 2010
Posts: 87
Gold Coast QLD
Damo Offline
journeyman
Damo  Offline
journeyman

Joined: Jul 2010
Posts: 87
Gold Coast QLD
Hi Guy's
Thanks for the tips on the board sizes. Before I start you wouldnt have sudgestions for rudders as well? When I build the boards I can make the rudders at the same time, any help would be graitfull
Thanks once again
Regards
Damien


Damien 1820 Raw Prawn (under construction)!!!
QLD
Re: New Centreboards [Re: Peter_Foulsum] #216559
07/28/10 12:53 AM
07/28/10 12:53 AM
Joined: Jul 2010
Posts: 87
Gold Coast QLD
Damo Offline
journeyman
Damo  Offline
journeyman

Joined: Jul 2010
Posts: 87
Gold Coast QLD
Hey Peter please check you PM Thanks
Damien


Damien 1820 Raw Prawn (under construction)!!!
QLD
Re: New Centreboards [Re: stillbitten] #217473
08/13/10 02:28 AM
08/13/10 02:28 AM
Joined: Aug 2010
Posts: 5
D
DickenCider 1777 Offline
stranger
DickenCider 1777  Offline
stranger
D

Joined: Aug 2010
Posts: 5
Have built MANY Mozzies over the years, Angle them back as far as you can. My early boats were forward and as I gained more knowledge on the construction of these little boaties I brought them back, As I saw elswhere in this forum, they do ease the weather helm so much and if the mast is raked the right amount, you can have neutral rudder helm and No rudder track.

AJ ex Dicken Cider. 1777

Re: New Centreboards [Re: DickenCider 1777] #217548
08/14/10 02:54 AM
08/14/10 02:54 AM
Joined: Nov 2002
Posts: 612
Cape Town, South Africa
Steve_Kwiksilver Offline
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Steve_Kwiksilver  Offline
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Joined: Nov 2002
Posts: 612
Cape Town, South Africa
AJ,
Your boat name kills me.. a few years ago I saw pics of it on an Auzzie website, and I thought it was a sponsor.. Took me a while to get it.

Re: New Centreboards [Re: DickenCider 1777] #217748
08/17/10 05:02 PM
08/17/10 05:02 PM
Joined: Mar 2003
Posts: 943
East Gippsland, Australia
Tim_Mozzie Offline
old hand
Tim_Mozzie  Offline
old hand

Joined: Mar 2003
Posts: 943
East Gippsland, Australia
Hi AJ
Good to see you on the forum at last.

Gary is planning to put them back to the max measurement, but not raked. Because they are narrower than the ones we have been using that also helps get the CofE a bit further back. Overall his CofE may end up slightly forward of the current boats but it is going to be very close.

It's just a question of whether the possible gains from having them vertical will outweigh any disadvantage from moving the CofE slightly forward. We will see...


Tim Shepperd
Mosquito 1775
Karma Cat
Re: New Centreboards [Re: Tim_Mozzie] #217758
08/17/10 09:33 PM
08/17/10 09:33 PM
Joined: Aug 2010
Posts: 5
D
DickenCider 1777 Offline
stranger
DickenCider 1777  Offline
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D

Joined: Aug 2010
Posts: 5
Maybe he should consider tapering the Centre case and run a gasket/ 2 strips of mylar wil do it as used on the tornado's. that way, the top rear of the box is at the rearmost point. the bottom rear of the centre case is angled back to allow 10 degrees rake and the front of the centre case is Vertical. 1 wedge inserted from the top only made of acetal or even better Polypropelene or nylon, front or rear of the case held in by some easily released method can act at a guide to protect the leadng and trailing edges. but they can be used to set the angle he may wish to try. I guess he can try one forward. 1 back and see how it behaves on opposite tacks. this Wedge system can be kept in place at all times. It may offer a way to make the mozzie behave better in different conditions. Just a thought I guess. Hows the sailing going anyway? I hae been tempted to build another Mozzie. Had my enthusiasm crushed with all that big stick bullsh** going on. Maybe I should just stay out of it an dstir the pot, hahahaha. Catchya buddy
DickenCider 1777

Re: New Centreboards [Re: stillbitten] #217759
08/17/10 09:40 PM
08/17/10 09:40 PM
Joined: Aug 2010
Posts: 5
D
DickenCider 1777 Offline
stranger
DickenCider 1777  Offline
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Posts: 5
maybe an option is to scrap the symetric boards and go to an asymetric centreboard design. It does work., but the right shap eto get the right lift will mean a board just under the maximum thickness. They do work having experimented with them previously. Only dribbling this end...

Re: New Centreboards [Re: DickenCider 1777] #217788
08/18/10 03:59 PM
08/18/10 03:59 PM
Joined: Jun 2004
Posts: 502
Port Noarlunga, SA, Australia
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Darryn Offline
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Darryn  Offline
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Port Noarlunga, SA, Australia
Go on AJ, build another one, you have to much talent to let it go to waste. We are having some great racing down at Normanville on Sundays in summer, sometimes 10 Mosquitos on the water.

Darryn
Mosquito 1782
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