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MPS or Gennaker Trim

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We used the MPS (do they still call them that ?) last Sunday, it was a broad reach and it would not set  presumably because it was blanketed by the main. The boat is masthead rigged and the tack was attached at the base of the pulpit, the boat not having a prod. The week prior we flew it with the wind just aft of the beam and it set perfectly. If we are not to fit a prod is the answer to use the spinnaker pole ? This would sort of defeat the purpose of an MPS for me, the sail is made by the Willis loft and its had little use so its mint, any suggestions ?

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A real MPS (multi purpose sail/spinaker) is nowhere near as versatile as a proper gennaker - Like an A2.

MPS is like a motor sailer - not great at either job.

An A2 will go from about 165 right around to about 70 deg apparent.   Neither sail works if you are really deep, then either take the main off, or use a pole (or a real Spin...)

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If you are set up with a tack line to your MPS, you can ease it a bit, this lets the luff roll up a bit, by easing the sheet as well it can all roll out to windward a bit, which will help (a bit). Short story though, is if you are too deep, the sail gets blanketed too much by the main, and, if you are too slow (which you will be if the MPS isn't pulling), then your apparent wind drops, and nothing works.

Probably the easiest thing to do is to come up (heat it up) until the sail is drawing well and you have good boat speed, then soak back down as far as you can while still keeping the sail flying and reasonable boat speed. The deeper you go (towards a flat run) the slower you will go and the shittier the sails will draw. But yeah, a proper gennaker will handle better (easier) and be faster. As already said, you can sail higher and faster and gybe down wind, just like a sport boat, or run a spinnaker on a pole, with all the incumbent pieces of string and what not.


I also run a gennaker off the bow (pushpit) but I got a proper one made and ditched the MPS I had, it was like trying to sly a brick...

Gennaker off the bow is nice and easy short handed and cruising. Spinnakers are faster, but a lot more work.

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  • 6 months later...

What sort of boat Frank?

Sounds very much like our learning process with the Davidson 28 and our old MPS. All the above advice is good, especially not running too deep downwind, and easing out that sheet as far as you can without the forward edge collapsing. It is very easy to end up oversheeted after it flaps a bit and you correct.

We have also started adding a second tack line tied to the windward rail so we can haul it out from behind the main a bit, but that's a hack.

Ultimately we are now setting up a proper symmetric spinnaker as it can get so much more sail out downwind, and in a boat like ours we don't have the apparent wind speed to rely on.

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For wind range in light air I can usually run it around 80 - 150 degrees apparent, less if I'm not paying pretty close attention to it. Bring tack line in tighter to sail high, ease our a foot or two to sail deep. Keep easing that sheet.

It's definitely happiest on the beam but then isn't everything?

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Chrs, ours is a heavy boat so there is probably little or nothing to be gained from sailing anything other than a direct course downwind . That said, it it is a stiff boat and happily absorbs the power of the MPS which is broad shouldered and seems vast when set (masthead rig) . It has a sock so is easy to deploy and so long as it is not blanketed it sets well and seems very stable so we will use it when the situation suits, probably on the longer passages like a SW to GB. The boat is a Hood 38 


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1 hour ago, Frank said:

so there is probably little or nothing to be gained from sailing anything other than a direct course downwind

Only if that's your destination, try going somewhere else and your Gennaker might surprise you.

Some Gennakers will happily sail wing to wing with the main, if you really must sail DDW then its a pretty handy option.

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Here are a few pics of the D28 for comparison. Note these are not all on the same day, though it's fairly similar light shifty harbour conditions which we often end up sailing in.

I'd be keen to hear any suggestions on trim, anything you'd do differently, and any thoughts on what a more modern sail shape would look like in comparison.





Edited by crump
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