Dufour 34 – Genoa/jib optimization

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Bruce3477
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Joined: Wed May 11, 2011 6:10 am
Location: South Africa

Dufour 34 – Genoa/jib optimization

Post by Bruce3477 » Fri May 27, 2011 12:14 pm

As an owner of a Dufour 34 Performance, and having sailed and raced in many club events with wind range all the way to 32 kts TWS (true wind speed), herewith are some ideas as to the ideal foresail set-ups for the D-34 P.

With the roller furler on D-34 P, and with an effective LL of about 12.2m, the actual sail areas and available LPG’s are substantially lower than that of those with deck/tack mounted sails.

Also to be understood, it that with the forestay set well aft of bow, the yacht loses about 15cm of “J” compared to a forestay set on the bow, and with furler above deck another 5cm of “J”, a total effective loss of 20 cm of “J”. This will reduce the effective LOD for the sail plan to about 10.1m, hugely less than nominal LOD 10.28m that club handicapper’s look at when rating racing yachts.

With said forestay set aft, and with almost plumb bow, the D-34P’s LPG% is ‘punished’ under IRC with much shorter actual “J” and higher net rating costs…

And with the tack (on roller furler) well above deck height, and to maintain the correct geometry of the foresail, the clew is much higher than the ‘deck sweeping’ non roller furler genoa, a further restriction on effective LPG of another 5-10%.

What this signifies, is that drop one size range on sail when compare performance from a roller furler genoa to a deck mounted foresail. In rough numbers, the 140% LP R/F is an effective 130%LP, the 130% LP R/F is an effective 105%LP, and the largest non-overlapping R/F foresail can fit on this rig would be about 93%...effectively a #4 and only good for wind in continuous range 20 kts +

Herewith a picture of D-34P, with 130% roller furling genoa under actual conditions, showing a very small overlap ‘on-the-water’.

Image

The wind range of 140% LP R/F genoa is good to about 12-14kts TWS, and is a very good combination for these conditions. With the traveler car almost right aft with this sail, have at most 5cm of car adjustment to de-power top of sail a very small range past 14 kts. The yacht makes full waterline speed at 18 kts AWS (apparent wind speed) / 030* AWA (apparent wind angle), holds to 20 kts AWS, and will broach to windward very quickly as approach the 22 kts + AWS range.

The 130% LP only starts working at about 12-14 kts TWS, and with good trim can carry to 20 kts TWS, with ability to flatten with traveler car further aft when wind is past 20kts and into occasional 25 kts range. This is ideal sail for mid to stronger wind conditions. But, the area is very close to a deck mounted 105% genoa due to hollow leach on 130% genoa vs. 105% LP genoa with battens.

Of course the rating difference is huge between the above 2 sail profiles.

The 93% LP, and is largest foresail can fit (inboard of stays with roller furler, due to high tack of sail and with correct clew height), is just too small for any range less than 20 kts TWS. At 10kts the yacht is a full 1 kt slower than 130% genoa, and at that yacht speed level… about 20% slower on the water.

The Dufour 34 Performance with 140%+ tack / deck mounted genoa, will be very effective from about 10-14 kts TWS , and will make a very good IMS/ORCi club racer in this wind range.

On the Dufour 34e (fitted with tack / deck mounted non roller furling genoa, and especially if fitted with jib battens and forestay re-located to bow), a 105% jib will be very effective from about 12-14 kts TWS upwards, but below 10 kts will struggle as yacht is just too heavy to make decent hull speed with said upwind sail area. But as have discussed before, the LL/P measure under IRC is very ‘unkind’ to this combination on Dufour 34e ...

JoeL18
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Joined: Mon Apr 02, 2012 11:53 pm
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Post by JoeL18 » Tue Apr 03, 2012 3:09 pm

As a new owner of a Dufour 34, I am very interesting in optimising racing performance - apart from genoa optimisation, has anyone tweeked the rig settings for better performance ? I cannot find the right settings for the rig.

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