centreboard wobble

radialuk

New Member
hi there,

does anyone else's centreboard wobble when its wavy, downwind? mine does and wondered if anyone did anything about it? packing the plate case or anything?

if not, what do you do about the instability it causes downwind?

thankyou
 
There's not much you can do. Borrow another daggerboard and see if yours happens to be narrow. If so, replace it. If not, maybe stick a rag in the slot?
For more stability downwind, put the board down more. To stop the wobbling in the case, bring it up.
 
wobble sounds serious. Mine hums at planing speed. Maybe the wobble is the early stages of the death roll?
 
Adjust your the brake (the rubber piece in the aft part of the trunk) so it's extremely tight and forces the board forward in the trunk (don't forget some tape on the forward intersection of the trunk and deck to cut down on the wear). This will help somewhat.

You aren't allow to use a rag to stuff in trunk, but you can use a control line - it doesn't take much to wedge in and stop the wobble.
 
Thankyou very much for the last post, thats really useful, a control line is a great idea, and the rubber brake too, I'll try those things.

Thanks again.
 
On the subject,i'm thinking about buting this guy's laser, and in the centerboard trunk there seems to be some stuff he put on the sides to make the centerboard stop humming when he got going fast.(he says it worked). Will this effect anything?(good, bad....)
 
On the subject,i'm thinking about buting this guy's laser, and in the centerboard trunk there seems to be some stuff he put on the sides to make the centerboard stop humming when he got going fast.(he says it worked). Will this effect anything?(good, bad....)

That may be illegal if you are planning to race the boat.... If so, perhaps you can remove the 'stuff'.
 
wel, the centerboard humming is perfectly normal, it just means you are going fast. I am not sure what you mean by wobble though.

Blades should not hum. It means the water is not leaving the trailing edge cleanly/evenly.

The wobble the first poster is talking about is side to side within the trunk... Not great either.
 
From what I've read, the 'wobble' described here isn't good. But the 'humming' debate is still up in the air. About half the argumemnts say that the boards 'humming' when at speed is a good thing, and hald say it's not! So - take your pick! heh heh
It's still an awesome sound when it happens tho :) Enjoy :)
 
Maljam,

Not sure of the date of your hull - would it originally have been supplied with a wooden board?? Some of the wooden boards seemed to be a bit thicker. Might measure the thickness of your board and or compare the fit of some others in the club - try also a wooden board.

Probably the cheapest and most likely to be class legal way to minimise this wobble would be a couple of thick hard-wearing coats of tough epoxy paint on the board - and maybe a coat or two inside on the bearing surfaces of the case, particularly if there is noticeable wear there. In any case except for the weight of the paint the extra protection would be a bonus.

I know your boat is in good shape but 'Repairing' the centrecase joins top and bottom is permitted and if glass tape is also used in this work it might bring the opening size back to a workable spec within the measurement/modification rules. You are probably talking of only one to two milimeters each side at most from what I saw on the beach.

regards
 
Maljam, I'll point out that there haven't actually been any arguments made that hum is good, just suggestions.

The hum happens because your CB isn't completely symetrical- one side has a dip or a rise that the other doesn't. That creates uneven lift forces from each side of the blade, which makes the hum. That means more energy is being put into making noise that could be put into forward motion.
 
Maljam...
regards
Thanx Glasky! But it wasn't MY boat that had the board wobble! heh heh. Twas nice to sail with you on Sunday too. Thanx.

No worries, computeroman2. I was just throwing in my 2-cents-worth. Just my impression from everything that I've read in here and in books and thru Google etc. It's still a 50/50 personal point of view about the pros and cons of the 'hum'. Not to worry.

Enjoy your sailing :)
 
The hum has to do with the imperfect flow of water past the rear tip of the daggerboard. there's nothing you can do about it... other then not sailing in planing conditions.
 
The hum has to do with the imperfect flow of water past the rear tip of the daggerboard. there's nothing you can do about it... other then not sailing in planing conditions.

That's just not true. There are a couple of easy fixes that will get rid of hum. (Search the forums here, the answers have been posted before)
 
I'm going to have to chime in as well and say it's also simply not true that hum is still a "personal point of view" as to whether it's good or not. The hum is a well-documented physical phenomenon that is known to be slower. Again, search the forums.
 

Back
Top