When I fully lower the centre board on my 26X before setting off it easily falls to its full extent. However, I notice that after I have motored for a short while I have slack in the raising line and the centre board has retracted to about half way. If I slow down or stop, the centre board does not automatically lower to the full down position again. Could it be that it is not fully lowered in the first place? Does the centre board fill with water (as the rudders do) to keep it down? Any suggestions or ideas please. Thanks Steve. (silver impulse)
Tue, 15/09/2009 - 5:08pm
#1
centre board
Hi Steve
Yes, it does fill with water like the rudders. However, the water drag when motoring does tend to swing it back a bit, by increasing amounts as you go over about 5 kts. This is fine, as you don't need it all the way down while motoring anyway - and if you motor at high speed with rudders up then you probably want it fully up.
Any sideways thrust will tend to prevent it dropping back. Even just some sideways windage without sails is enough - that may be what's happening as you slow down. If you turn slowly while dead slow you'll probably find it will drop down again.
A useful tip is to put some marks on the rope - an indelible marker works quite well - which indicate the CB positions. Do this while moored: haul the board all the way up and mark the rope where it enters the jam cleat. Then let the board right down (until if clunks), take up the slack, and make another mark the same way. You may find some intermediate marks useful later on - e.g. best position for motoring.
This way you can (a) tell if you've actually hauled the board all the way up, (b) if you want to let it fully out, cleat the rope at the full-down mark, even if it lies slack on the deck. It usually works it's way down, and you can tell this has happened once the rope pulls taught. If you want to let it down while under sail you usually have to turn through the wind (tack or jibe), and it will fall at the point the sideways pressure comes off.
Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight
Hi
Avoid motoring with centerboard fully lowered.
You can damage the pin and the bracket .
And the force created can make the pin to "dig" into the centerboard trunk.
With empty ballast it can be dangerous...
Jose
Cheers
Jose
http://arianeoveleiro.blogspot.com
My rule of thumb is if at displacement speed or below (approx. 5kts, 7mph) then CB and rudders down, gives much increased steerage capability especially cross stream or tide. After all these speeds are sailing speeds and what the rudders and CB are designed to handle.
When on a plane >5kts or 7mph (approx) then CB and rudders would be up as they have a possible negative impact on steerage as well as a possible increase in unstability of boat.
Though in rougher conditions at speed a small amount of CB down in order to simulate a skeg is useful for better steerage (around six inches of CB)
Like Rick my CB Line was marked up for full up, quarter, halfway, three quarters and full down as even when sailing the CB angle can have a significant impact on stability and sailing speed, so knowing where your CB is sitting at a glance is imkportant.
Cheers
Morris
Thank you to all who have taken the time to reply to my query. It is good to know that I am on the right track and that there is plenty of help and advice out there. My asumption is that the hole in my CB may be blocked and therefore not weighty enough to keep it down on occasions. I will investigate when next out of the water. Thanks again to all. Steve
Hi
At displacement speed or below (approx. 5kts,
7mph) then CB 45th down and only one rudder down, gives suficient steerage
capability increase speed and a lot of spare fuel.At 45th the centerboard will be locked to lateral movements.
Manouvering in small spaces then CB and rudders down
"After all these speeds are
sailing speeds and what the rudders and CB are designed to handle."
Yes but there is a difference. When sailing there is a big sideways force on the centerboard that locks it in a position. Motoring creates linear force only and will make your centerboard to vibrate sideways on the bracket and/or climb up freely into the trunk.
This is very probably what is happening to you.
Cheers
Jose
Cheers
Jose
http://arianeoveleiro.blogspot.com
Jose,
at the risk of being pedantic the force applied to the CB by forward motion may be a significant force but the boat and hence the CB is also potentially effected by tide, current, wind etc. Depending on the strength and directions of other forces then the CB generally would tend to stay down due to its aerodynamic design and its ballasted condition. Even if the assumption is made that there is really only one force and that force is from ahead onto the CB the aerodynamic design of the CB would tend to move it to the left or right, as it is a wing not a flat faced object.
If it was the forward force of the boat causing the CB to retract then if the CB was left down at high speed you would also expect the CB to retract and in fact it doesn't, as I often found out when I first got my 26X and forgot to lift the CB when fast motoring. The CB being down at speed does however affect the steerage stability and I quickly learnt to ensure the CB was up before I went from displacement to planing speeds.
Cheers
Morris
Hi
It happened to me some times that I forgot to pull the centerboard up and went from displacement to planing speed with flat water (lake) and no wind.
When I remembered to pull the centerboard up, there was no weight there. The SST line came up freely. The centerboard was already up bi it self.
If I stop the centerboard goes down freely immediately
That never never happened when sailing...
I don't know if that is related with mods in mi boat (it is a very modified Mac)
Centerboard Mod...
http://arianeoveleiro.blogspot.com/2009/05/centerboard-pin.html
...
All I can tell is that: some times it happens... (but In 12 years with "Ariane"... many things happened...)
Other times the boat simply goes "funny" and starts to do frightening things... (I remember once at sea with small waves)
**** It is a very dangerous mistake to forget to pull the centerboard up at high speed and empty ballast... ****
Cheers
Jose
Cheers
Jose
http://arianeoveleiro.blogspot.com