Hunter 306 - lee helm vs forward hull windage

[Arbee]

I know I've posted previously about the challenge of lee helm on our beloved in-mast furling H306. Since having a little more experience now with the boat and trying a few things with sail trim and halyard tension, I've come to the conclusion that my main issue beating into gusty winds may be more about get blown off by forward hull windage rather than actual lee helm (though the wheel position still says I have lee helm). We come from a trailer yacht background with very balanced helms and lower profile hulls, so perhaps it's more a consequence of trying to point up in our wide, chubby, high profile 29 foot floating caravan. Wouldn't swap it for the world but perhaps that's just the compromise with these boats. On a positive note, I did conclude my main halyard was too tight, and with a looser halyard our in-mast main now has better shape and a slight improvement to the lee helm situation overall.

Would be interested in others' thoughts on this.

 

[jssailem]

No experience with in-mast furling. Looking at the info from a sail trim point I think you are spot on with your conclusion. Pulling the mainsail tight and flat would move the center of effort on the mainsail closer to the mast. De-powering the main and allowing the fore sail (assume a Genoa) to force your bow to the LEE in an unbalanced condition. You could reduce the ForeSail (furl the foresail), or you could put twist into the foresail by opening the leach moving the sheet block forward, spilling wind.

Move sail’s center of effort (sail draft) aft, Increases weather helm.

Easing the outhaul and some halyard tension would give the main a fuller shape Powering UP the Main. Putting more force behind the Mast adding balance to the sails.
Mainsail shapes.

You might continue to adjust the balance if you can reduce the size of your foresail. For example using in a 100% or 95% jib when the wind is up instead of the furled Genoa.

 

[Arbee]

With in-mast furling, the risk of loosening the main halyard is taking it too far and creating wrinkles in the luff that jam the furler. A fine balance but I think I have it about right now.

In regard to our foresail, it's only a 100%, not a big genoa. In theory and practice, it seems that while furling reduces the sail area it also moves the COE forward, so offsets the sail balancing benefit to a large extent. A shorter 110% foresail might actually give me better balance perhaps by keeping the COE further aft.

 

[Will Gilmore]

Easing the outhaul and some halyard tension would give the main a fuller shape Powering UP the Main. Putting more force behind the Mast adding balance to the sails.
Mainsail shapes.

Exactly my thoughts too.

Lee helm is Lee helm whether the cause is sail trim or hull windage or a dirty bottom and keel and rudder drag. The trick is to balance that forward windage with other effects. If your bottom gets too fouled, the greater drag on the a fin keel and post rudder can allow the forward sections to slide leeward more easily then the after section.

I notice the 306 is a B&R rig. I've never sailed a B&R rig, but they look like they would be very sensitive to upper shroud tension. Over tensioning would bend the mast and flatten the main. In not sure of it would tension the forestay in equal measure or by a significantly lesser degree.

-Will

 

[dlochner]

Lee helm is dangerous, it needs to be corrected, at its core the problems an over powered jib relative to the mainsail. A lot of causes for that.

Mast rake can be a cause. If the mast is vertical or tipped forward the center of effort moves forward adding to the lee helm. On a mast with a backstay this can be corrected by increasing backstay tension or on a keel stepped mast moving the butt forward and blocking the mast at the partners to it leans aft. I'm not familiar enough with B&R rigs to render an informed opinion on how to adjust mast rake.

Check to make certain the rig is tuned correctly, even those shrouds you have to go up the mast to tune.

Reef the jib sooner rather than later. That will reduce the power ratio between the main and jib, reducing lee helm.

Continue to work on mainsail trim. Leech tell tales are essential for trimming the main. If you don't have them, install them. The bottom 3 should be streaming aft and the top one flicking forward and aft when the sail is well trimmed.

Check the accuracy of the rudder sensor. You mentioned it feels better, but the sensor says you still have lee helm. At the dock, center the wheel and then check the actual rudder position. It is not unusual for the cables to stretch or the for the sensor to be out of alignment with the rudder.

 

[Arbee]

Thanks for your input, much appreciated.

Just for context - the bottom is clean, the wheel center (not a sensor, just tape marker) is straight and it motors straight, the hull is clean, the mast has quite a bit of aft rake and a little bend, the telltales set beautifully on both sails from bottom to top, and while the lee helm softens with a slight foresail furl, it doesn't improve any further as I continue to furl the foresail, until it runs completely out of power. As I mentioned, the looser main halyard has improved things, but only slightly.

After decades of sailing trailer yachts I can tell when the boat is "in the slot", but even then if I let the wheel go it bears away (on both tacks). I can only conclude windage and/or the foresail (and even the main perhaps) is not the right sail for the boat. I have the 306 manual and will check the sail dimensions of the in-mast furling rig when I take the sails off next.

 

[jssailem]

and even the main perhaps

Seeking balance can lead you to many opportunities.

An In-Mast furling sail does not have the same aerodynamics as a sail hanked on to a standard mast. It is why you do not see in-mast furling on boats designed for racing. Certainly the design of the sail on the boat could be a factor.

Interesting that under power the boat runs true (no prop wash affect on the rudder). The hull, keel, and prop could also be a factor as you seek sailing balance on the helm.

But most of the correction will be above the water line. Choosing the right sail combination, setting the job sheet blocks so that you get the right jib shape. Perhaps a tweeker could help with trim if you want to adjust the angle of the sheet from the jib tack.

These are all just ideas to explore not instant solutions. One needs to be on board and sail with you (your boat, rigging and sails) to really narrow down the possibilities.

 

[jssailem]

If you are into the why of this challenge, you might find the works of Arvel Gentry interesting. It is deep into the technical.

http://gentrysailing.com/pdf-theory/Aerodynamics-Of-Sail-Interaction.pdf