kieronriley
Well-Known Member
is weather helm always caused by sail plan or can it be caused by badly placed balast .thanks ,kieron.,
weather helm
- Thread starter kieronriley
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ColinHuggins
N/A
Either -or both.
You'll get some more erudite explanations, but IMHO weather helm is the result of the relationship between Centre of Effort (from your sail plan) and Centre of Lateral Resistance (from shape & displacement of your hull.)
Moving your mast or changing your sails affects the former, modifying your hull profile or altering your ballast the latter.
For a more detailed analysis refer to one of the unpaid knowalls on this website.
You'll get some more erudite explanations, but IMHO weather helm is the result of the relationship between Centre of Effort (from your sail plan) and Centre of Lateral Resistance (from shape & displacement of your hull.)
Moving your mast or changing your sails affects the former, modifying your hull profile or altering your ballast the latter.
For a more detailed analysis refer to one of the unpaid knowalls on this website.
boatmike
Well-Known Member
Actually I don't think that answer can be improved upon much. There are many causes but the most likely is sail plan. If she has a tendancy to bear away from the wind its potentially unsafe. Bearing up into the wind is normal and should be expected. If it's excessive making the tiller heavy to handle try sailing under genoa alone to see if it cures it. If it helps than moving the mast forward, tightening forestay etc is the way to go.
G
Guest
Guest
there are times when an oversized genny can in fact bring its CoE back enough towards the mast - that allied with a good size main can increase WH.
That is why reduction of large genny can also help in some cases.
It is generally accepted that reduce main, rake mast fwd or even if possible step mast more fwd etc. are ways to ease WH ....
But some boats are just built with it in !! Macwester 26's etc. are a good example. The 27 had its mast height increased and boom reduced to give greater aspect ration and move CoE slightly fwd to help.
The Snapdragon 24 is another example when it became the 747 ....(OK wise guy ..... yeh yeh yeh ... when Boeing bought them out !! /forums/images/graemlins/grin.gif )
At end of day it is down to experiment with reefing, sheeting and some boats staying of certain wind angles ....
That is why reduction of large genny can also help in some cases.
It is generally accepted that reduce main, rake mast fwd or even if possible step mast more fwd etc. are ways to ease WH ....
But some boats are just built with it in !! Macwester 26's etc. are a good example. The 27 had its mast height increased and boom reduced to give greater aspect ration and move CoE slightly fwd to help.
The Snapdragon 24 is another example when it became the 747 ....(OK wise guy ..... yeh yeh yeh ... when Boeing bought them out !! /forums/images/graemlins/grin.gif )
At end of day it is down to experiment with reefing, sheeting and some boats staying of certain wind angles ....
oldharry
Well-Known Member
ChugginAround just about sums it up: If it is the rig, make sure it is set up properly. If you have a lot of moveable weight up forward this can cause the boat to gripe to windward, and bringing it aft may help. Not quite sure how you can change the hull form: on the old Eventides for example it was found that filling the space between skeg and ballast keel eliminated undesirable weather helm, and it was a toss up between that and putting a bowsprit on and changing to cutter rig, which had the same effect.
Some boats sail much better kept upright. Try reducing sail as the wind and helm increase to reduce the heeling. You may find you actually go faster! Years ago I had a plywood 20 footer; a miserable little boat if ever there was one, with vicious weather helm in any sort of wind. We tried everything to no avail. Then one day out with a novice crew, struggling along in a rising wind, I reefed down more than usual - she took off like a rocket! We found that reefing the main in anything over F3 and keeping her upright solved the problem almost entirely.
Some boats sail much better kept upright. Try reducing sail as the wind and helm increase to reduce the heeling. You may find you actually go faster! Years ago I had a plywood 20 footer; a miserable little boat if ever there was one, with vicious weather helm in any sort of wind. We tried everything to no avail. Then one day out with a novice crew, struggling along in a rising wind, I reefed down more than usual - she took off like a rocket! We found that reefing the main in anything over F3 and keeping her upright solved the problem almost entirely.
cliffordpope
Well-Known Member
If you have the plans, or if not, next time she's out of the water, make an accurate drawing of the underwater profile on stiff cardboard and cut it out. You can balance this on a knife edge and mark the CLR reasonably accurately.
Then draw a scale diagram of the sail plan, work out the area of each sail, and join up the centres of each sail, weighting the proportionate distance with the respective areas. That will give the overall CE (static, I know).
Mark that point on the cardboard, and you can see how the two positions compare. Then you can try juggling the variables - altering the sails, moving the mast, extending the bowsprit, changing the trim by shifting ballast, even cutting away or adding deadwood.
Good fun on a cold rainy day in the comfort of your own sitting room.
Then draw a scale diagram of the sail plan, work out the area of each sail, and join up the centres of each sail, weighting the proportionate distance with the respective areas. That will give the overall CE (static, I know).
Mark that point on the cardboard, and you can see how the two positions compare. Then you can try juggling the variables - altering the sails, moving the mast, extending the bowsprit, changing the trim by shifting ballast, even cutting away or adding deadwood.
Good fun on a cold rainy day in the comfort of your own sitting room.
twisterkai
Well-Known Member
It's worth checking that she's floating to her marks correctly - ie, as the designer intended. With a long keeled hull form (assuming we're talking about the Morgan Giles), if she's down at the bow, but the mast has still been set upright, the change in lateral resistance won't have changed dramatically but the change in the centre of effort will have been moved aft, hence weather helm.
This was discovered many years ago after a particularly punnishing beat from Falmouth to Fowey - I'd always reckoned that she was trimming down at the bow and set about finding why. Eventual answer came in the form of 300Kg of 'trimming' ballast under the foc'sle sole boards. This was re-distributed further aft until she sat to her lines. Result? Masses of mast rake. Rig was adjusted and since then we can fly to windward at 30 degrees of heel with just an index finger under the tiller!
It's worth noting that when that lot was going on we had a fairly new suit of sails and were able to discount any adverse effects from sail shape etc. If you're happy with the way the boat floats to her marks and the rig is set up correctly it could be that the sails are simply worn out, although it's usually possible to get some extra tension in the halyards and outhaul to flatten them with some additional creative rope work.
Good luck with the experimentation!
This was discovered many years ago after a particularly punnishing beat from Falmouth to Fowey - I'd always reckoned that she was trimming down at the bow and set about finding why. Eventual answer came in the form of 300Kg of 'trimming' ballast under the foc'sle sole boards. This was re-distributed further aft until she sat to her lines. Result? Masses of mast rake. Rig was adjusted and since then we can fly to windward at 30 degrees of heel with just an index finger under the tiller!
It's worth noting that when that lot was going on we had a fairly new suit of sails and were able to discount any adverse effects from sail shape etc. If you're happy with the way the boat floats to her marks and the rig is set up correctly it could be that the sails are simply worn out, although it's usually possible to get some extra tension in the halyards and outhaul to flatten them with some additional creative rope work.
Good luck with the experimentation!