WHAT AM I DOING WRONG ??

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rob1612

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HELP !!,
This is a problem that I cant get to grips with.
When sailing my fin keel 21' sloop rigged yacht it does something which no one seems to have heard of.
Whilst on starboard tack she sails away fine, pretty neutral really with just a tad of weather helm. Perfect you might think.
However when she tacks on to port tack something weird happens.
She develops Lee Helm.
If the tiller is let go she will always charge off downind.
She probably doesn't point so high either.
Why is this.
HELP PLEASE.
 
Sounds as if the keel may not be on straight?

Also perhaps if the mast was a long way off vertical transversely it might have such an effect but I think it would need to be so out as to be obvious?
 
Hi leighb,
To my knowledge the keel has never been off,
I have measured with the topping lift down to the chaoinplates and it doesnt seem that far out.
Should I check from corner to corner across the stern. Thanks
 
Is the mast straight? That is on the centre for & aft and across the beam! This will cause the symptons you are having. A small miss-alignment can make a big differance.

You need to measure the distance from the masthead to the chainplates on both sides. it should be excatly the same! Mast rake will also have a effect here and any port or starboard bias will be increaed by it.


good luck,
 
Def sounds like the mast is not properly set up.

Might be a silly question but, are the chainplates in the same place each side?
 
Hi again,
Will check the mast again, This time with a tape strung to
one of the halyards.
The rudder looks fine.
Have a go again at the weekend.
 
A little unlikely perhaps with your size of boat - do you have an offset prop? If an outboard is it trailing offset?
 
My previous boat had the same simptoms.It turned out to be the rudder that was assimetric.I reshaped it and she sailed beautifully from then on.
 
Does the set of the sail change across the tacks?

Lee helm is caused by either the mast moving forward or centre of lateral resistance moving back. So, are aft shrouds at the same tension? Is your backstay split at some point & are both sides same tension? Might rudderpost be moving? Are both sides of the hull the same (ie assymetrical damage repair)?
 
Has the boat been certified (measured) if not, could it be distorted (for whatever reason)~ if you look at the boat, is the transom horizontal to the vertical mast. Does she sit upright in the water -weight distribution. Who built/finished her -professional? If nothing moves, the 'effective' hull shape must be uneven from one tack to the other in order to change the relationship between centre of effort and centre of lateral resistance
 
Don't despair my 21fter has always sailed better on port tack than starboard. This for 20 years through 3 masts and 2 sets of rigging and rigging set up. I have checked the keel, seems straight and the rudder seems fine. So to me it is a total mystery. I suspect yours may be also.
Of course you should check the obvious but be prepared to never find out. olewill
 
Apart from checking the rig tension on port & starboard stays, suggest you also check the loading of stuffs inside the boat, unbalance weight at P/SB/fore/aft may also contribute to the issue.
 
I was going to add that one. It's often the case that a slight offset in ballast will not show as a static trim problem, but will affect the angle of heel. As a first check dangle a weight on a halyard to check "plumb centre" but if this still shows nothing hang a bucket of water on the end of the boom and swing the boom over either side and see if "plumb" is unequal. If so its probably offset ballast. Move your beanz!
 
Offset ballast will show up in static trim but is not likely to be the cause of your problem unless it is very noticeable. Certainly my boat (along with a lot of other modern Moodies) has a 10 degree static trim problem (most storage is to port) but sails reasonably the same on both tacks.

And rigging cant be slack on one side and not on the other if you think about it.

But you clearly have a symmetry problem and the place to start is with the rig not least because that is most easily remedied. Is the mast straight and central when rigged? Does it remain so under load (ie you havent got thinner wire rigging on one side than the other?). Are the chain plates moving on one side and not the other (ie bonding issues on one side) . And are the bulkheads still firmly bonded to the hull?

Most boats (probably all boats if you were to measure with enough precision) are asymmetric in hull shape so the question is one of degree. If your mast is set up so that you have almost no weather helm / lee helm on one tack then you will have more of one or the other on the other tack. So maybe at this stage it would be sense to alter mast rake to bring the lee helm tack back to a bit of weather helm. When you have done this, is the weather helm on the other tack unacceptable?

If it is, then you are down to issues of the shape of the hull, rudder and foils. This could either be a quick rudder job or a task that costs nore than the boat is worth. So eliminate everything else before contemplating those issues.
 
I'm with the rudder being the problem. I have seen this on several boats, albeit with wooden rudders. The rudder had developed a slight curve and this gave the effect of a "trim tab" in that the rudder was offset by the water flow slightly to one side. This caused weather helm on one tack and lee helm on the other.
 
Actually I'm wrong when I said "And rigging cant be slack on one side and not on the other if you think about it." cos it can be if it is so slack that the mast can flop over from one side to the other. I'm assuming there is enough rigging tension for both side to have some tension in which case it will largely even out.
 
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