While sailing on Saturday; 15-20 knots, mild chop; I still couldn't point well and maintain speed. I was sailing in the groove of the jib telltales. The mast was really misbehaving and flipping all over the place, and the windward/aft diamond wire was very loose.

My theory is that the diamond tension was too soft which leads to the mast bending significantly which leads to reduced rig tension. The bendy mast flipping all over the place will also affect the shape of the main adversely.

Any mozzie sailors with experience in improving pointing ability? Am I on the right track to improved upwind performance?

Still cant point compared to what?

Work out your tacking angle then work through your sail shaping controls until you get the right adjustments. I use a tactik which is just right for the job but a GPS will work also. Analogue compasses are useless. Aim for tacking through less then 90 degrees.

Maybe you need to swap some of that speed for height? Your more likely to get to the top mark first if you sail a shorter distance, unlikely to consistantly win upwind drag races with F18s and Taipans.

If you diamond wires adjust seperately first tighten on the beach until they are both firm then sight up the mast to make sure the mast is straight and adjust to straighten mast, halyard is an ideal stringline for this.

Setup your diamonds on the water, point the rotation at the daggerboard case then tighten both diamond wires the same amount until the windward wire is just coming loose when trapezing. Recheck your mast is straight when you return to the beach.

Check you spreader rake also, tips level with back of mast should get you in the ball park.

Not much point making adjustments until you know how bad the problem is, using other boats isn't much use, even if you borrow a tacktik and come up with a number you will at least have something to check against when you make your adjustments.

Darryn
1782

Can't point compared to H16's. Sorry, we can point with them, but jib luffs and speed drops too much and they leave us for dead.

Tacking angle is greater than 90 degrees, data is from GPS plot. I'll get an accurate angle tonight.

That is bad news if you cant outpoint a Hobie 16, do you have luff tension control for your jib? You want that tight.

Darryn

Nick,

Sounds like diamond tension is way too loose and the mast is just flopping around. <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" /> This would probably affect the jib luff tension and therefore the whole jib effectiveness particularly if there was any waves or slop. Try 30 kg tension load on the diamond wires as a starting point and probably work up from there. Someone must have tensiometer at the Yacht Club.

Once you have set your diamond wire tension then probably look at increasing your stay tension too.

Regards,

Peter

Yeah, it's a bit embarrassing!

It was fine in the lighter stuff, about 10-12 knots. We could point with them and after a late start were catching them quickly. But as soon as the breeze picked up, height disappeared.

I've bumped the diamond tension up and will see how that goes this weekend.

Nick,

It sounds as if there may be more than one issue as you mention that in lighter breeze it goes fine but once the breeze comes in....
Diamond tension will be a start...and these are an issue of their own as preference says whether to run them tight, firm or .....but worth a check to see where they sit in relation to the mast track (rake)...again no hard and fast rules here either
Look at rotation position, jib sheeting positions , jib luff tension and then mast rake....but one at a time and remember to keep a diary of what you have changed and from what settings to what settings, wind conditions, sea etc etc....if it does not make a improvement, change it back and on to the next issue....there is no hard and fast rule to make them go fast.....we spent most of last season sorting youngest's boat out and thnk we got it close to season close...

Enjoy the challenge...always happy to help.

David
"Banh Sidhe"

GPS track of a race a while back. Current tacking angle is very similar.

The bottom line is an upwind leg. Wind is approximately coming from the right (ESE).

You can see the extent of my problem...

Well outside 90 degrees but I would expect your gybing angle to be much less then it shows on the track also.

This would be the case if your sails are cut to full or the max depth is in the wrong place or you cannot control the sail through sagging jib luff etc. These same issues will help you sail deeper downwind but this appears not to be the case from the track you posted.

Perhaps you are sailing the boat in footing mode all of the time? On the track what colors are set to what speed? If you are seeing 10knots+ upwind you really need to go into pointing mode.

Darryn
1782

In 15-20 knot winds, definitely going over 10 knots upwind (from GPS data).

I'm fairly convinced it is a combination of forestay sag and deepish main (mainly from not pulling on enough downhaul). I may be footing a fraction, but it usually feels like I'm pinching, and often get abused by crew for it.

We'll see how it goes tomorrow with tighter diamonds, forecast is for a blow!

Downwind is another story, I know I sail too high because it is more fun. Will work on it tomorrow as well.

The purple section coming into the top mark is footing mode. Green is slow (coming out of tacks/gybes etc.) Shades of blue in between.

Good news, we could keep up with the middle of the hobies upwind now. Height was good, as was speed. Looks like the diamond tension was key.

Should have some GPS data from the race to mull over tomorrow night.

Yeah Nick <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> It should have given you a win on handicap or at least a win in your own mind. You should always be able to out point a Hobie 16 and be faster in light winds.

Did it feel like there was less weather helm upwind as well ?

Regards,

Peter

Darryn,

Do you have your spreaders set up cat rigged with the tips level with the back of the mast ?

I've just repositioned mine to this location because I thought the rig was too stiff/powerful and wondered what sort of tension you use.

I haven't had the mast on the boat yet due to beam rebuilding and had started to tension the diamonds and noted a significant increase in mast bend so I stopped tensioning. I also recall that with the diamond wires more in line with the mast centreline I could induce a reverse camber with any sort of stay tension. The new setup should overcome this to some extent.

The Glenn Ashby Catamaran Tuning DVD indicates that a 4 cm distance from the diamond tips to the rear of the mast was a good starting point but that was on a F18 with a much bigger/stiffer mast section so I wondered how relevant it was to the "softer" Mozzie mast section.

Regards,

Peter

In the 15-20knots yesterday they were pinching at times so they were still a fraction higher than me, but not as much as usual and VMG was still roughly the same.

Weatherhelm was pretty much the same as before, have never really had a problem with that.

The spreaders are fairly level and don't induce much if any fore-aft pre-bend.

Boat handling let us down a bit yesterday, and me falling overboard in the second race! First race was much better.

Hi Peter, I have set mine level with the back of the mast. I did a fair bit of stuffing around with them after the Lock sport Nationals were I had lots of power but couldn't point. At Lock sport I had negative bend without the sail on and the mast straightened with the weight of the sail hanging on the hook, lots of depth in the sail but cannot point due the fat leading edge, lots of downhaul made it work sort of but the sail I was using didn't tranfer the load from the downhaul attach point very well so I ended up with an ugly looking sail.

When I got back from Lock sport I started working on a better looking airfoil with the goal of pointing rather then power, so raked the spreaders to kick the middle of the mast forward when the downhaul and mainsheet are hauled on thus flattening the middle of the sail plus I learnt a lot about sails from helping Chris Dean and Gary Saxby develop these UK Halsey sails I am using. So now have an airfoil with less depth in the sail but max depth is at the right place and as the downhaul and mainsheet are applied the sail flattens in a linear fashion, not in patches as most other sails I have used do.

As for diamond wire tensions I cant give you mine as I dont know what they are, I set them up as I said further up this thread, on the water with my weight on the trap and thats the way you should set them up too as you will weigh more or less then me. I will measure them for you though next time I have access to a Loos gauge.

I haven't tested a F18 mast section so I cant really comment on how they set up their spreaders. I would move the spreader tips forward of my current position if I put on 10kgs and change the luff curve on my sail.

Darryn
1782

Hey,
Yesterday Mighty Mozzie 3,1,1,3 against the H16s & that was before yardstick!! <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> so it could get even better.
I even beat one of the A,s across the line in a shortened last race <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />
Can't say enough about how well Darren has set up Top Gun. It killed the H16s up wind, but I still have to get better speed down wind.
But LOVE The new boat <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

Polar plot.

Best VMG upwind seems to be around 40-45 degrees in 15-20 knots. Best VMG downwind seems to be around 150-160 degrees.