Poor pointing ability

[Jacket]

I've got a fractionally rigged GK24, which according to all the boat tests I've read should point very high, tacking through about 80 degrees. However, I'm lucky if I can get my boat to tack through 110 degrees.

I've tried everything I can think of to improve matters. The main is new and the genoa, while older, is one of these high tech plastic sails, which as I understand it shouldn't stretch with age. I've spent a reasonable amount of time fiddling with the rig tuning, with no effect. Also, when the rigging was replaced the winter before last, the mast was set up by a rigger, who presumably knows what he's doing.

The boat's bottom is kept clean, and I have a folding prop. I used to race dinghies successfully, so I'm fairly sure that the sails are trimmed correctly.

Basicly, I've run out of ideas of ways to try and improve pointing ability. Anyone got any suggestions?

 

[david_e]

I would be interested to know how you are measuring it, is it against the compass?

 

[Jacket]

Yes, I'm measuring it against the compass, as this is how the boat tests do it. Obviously there'll be leeway on top of this, but my boat seems to make no more leeway than would be expected.

 

[qsiv]

At the risk of oversimplifying ..

As far as the headsail is concerned the headstay tension is everything when going up wind (luff tension of the sail will define the power and to a minor extent modify the pointing ability). Luff sag (too litle headstay tension) will kill you upwind - sight up the forestay and you should see no more than an inch or so of sag.

In general the further aft the mast is raked the higher you will point - but too much will generate weather helm.

The main has less impact on pointing - however you will probably want the entry flatter rather than fuller (cunningham), and the leech tension in the main will contribute to the power you generate going upwind - but dont over do it. Keep the leech telltales streaming. Twist should be maintained such that the outboard end of the top batten is parallel to the boom - you will need to adjust the kicker to maintain this as wind strength varies. In very light or very strong winds you may want to allow some extra twist. Also, when sailing in a tideway that is not absolutely aligned to the wind you will find you need more twist on one tack than the other.

Sheeting angle of the headsail is another key component, as is leech tension. Leech tension should be 'fairly' high but not at the expense of strangling the slot between the main and the genny. Dont worry if the forrd third of the main is slightly lifted by the genny - aim to keep the slot between the genny and main fairly even in distance and curvature. Luf tension on the genny controls the fullness of the entry and has more to do with power than pointing (but as always they are inter related).

Others will doubtless differ in their approach - but I manage to tack through about 75 degrees (the CMg tack angle is wider due to leeway)

 

[david_e]

hmm......I have never bothered to do this against a compass so I can't comment on that, I check how I am pointing by comparing mine against other boats on the water, normally when I'm racing, making small allowances for things like rig and hull shape etc. But if you are cruising only then this doesn't help.

Your rig set up should not affect the performance by as much as you say, I presume you have the sails hard in so to speak, and after that it means checking underneath for keel and rudder alignement or something else.

Failing that get a mate with a boat that has similar performance and see how that stacks up, they might well spot something you dont?

 

[vyv_cox]

My pointing improved by 10 degrees when I bought a new genoa.

 

[chriscallender]

I've often been disappointed by my ability to go upwind compared to other boats, until I get close and then see some water/steam coming out their exhaust!

 

[capn666]

Maybe a daft suggestion - but have you checked the compass for deviation?
Capn

 

[Jacket]

Thanks for reminding me- I'd forgotten I need a new compass for the boat!

However, I don't think thats the problem- I knew the fixed compass was playing up, so I double checked with a handheld compass held well clear of all metal objects.

 

[aod]

You can obviously trim sails and if the rig has been set up by a competent rigger my suspicions would fall on the headsail. Unless it's Kevlar,Vectran or PBO it will have stretched, even Pentex stretches. My assumption is that your headsail is Mylar which with average use has an efficient lifespan of two seasons or two years which ever way you measure it.

The easiest way to find this out is to have the sail hard in and take photographs lying on your back on the foredeck. Send the pictures to the sail maker and ask their opinion. If it has stretched they can cut the luff and re-weld.

 

[Jacket]

That'll be the answer then. Yes, the sails Mylar, and well over two seasons old.

I'd been told that Mylar didn't stretch, it would just suddenly give up on you one day and tear. If thats not the case, the sails probably well past it now- I've had the boat 3 years, and the sail wasn't new when I got the boat.

Problem solved. Now I just need to find a bank to rob, or a rich widow to marry so that I can afford a new sail (the existing one's to tatty to be worth re-cutting).

Thanks for your replies, everyone.

 

[aod]

IF it's of any use I can strongly recommend Parker and Kay of the Quantum sail group. No, I don't have any commercial links, it's just that they have supplied me with racing sails for the last four years and I have found their quality, after sails service and attention to detail second to none.

 

[david_e]

Re: Deviation

I thought about this, but concluded that deviation is a relative adjustment against a set or known point, ie North. Here the boat is going through 110 so even if the compass was out bu 10 it would still tack through 110 degrees.

 

[chriscallender]

Re: Deviation

Deviation curves are roughly sinusoidal , so if deviation were maximum on one tack, then it would be somewhere close to zero or even deviating the other way after tacking. In other words deviation depends completely on your heading, its not just a constant error.

So if the compass isn't well adjusted it could easily be responsible for a reasonable difference between the aparant tacking angle and the real one (say 20 degrees).

However, if you repeated the same experiment lots of times with different wind directions, and the real tacking angle was for example 80 degrees then you would sometimes measure significantly less than 80 degrees and sometimes significantly more.

If the compass always shows about 110 between tacks no matter what the wind direction is, then its probably because the boat really does tack through 110 degrees. (and compass deviation isn't too bad either!)

 

[david_e]

Re: Deviation

Interesting, thanks for this (have only just learnt about this in Yachtmaster this year), I can see how it could play a part but could deviation be as much as 20 degrees from one tack to another?

 

[kdf]

Others have made many useful suggestions as to how you can improve the pointing -all are valid to some degree but there are other places you can look. For one, your boat is fractionally rigged. This means a smaller headsail with narrow sheeting angles and a larger mainsail. With most fractionally rigged boats most of the drive, and more importanty pointing ability, comes from the mainsail. Headsails are very important also especially luff tension and forestay tension (not the same thing). Any tension you put into the halyard will move the draft of the sail forward and improve your pointing. Also taking in on the backstay will take any sag out of the forestay and also tension the jib luff even more.

On Farr 40's (yes I realize they are very different but the same principles apply) we over sheet the main by hardening down on the mainsheet and then play the main with the traveller. You have to have the leech tension on the main bar tight with no twist and this means really sweating down on the sheet. Look at the top batten and it should be almost cocked to windward - you check this by getting under the boom and looking up along the leech of the sail.

 

[snowleopard]

how do you know when you\'re hard on the wind?

is it when the jib luff starts to lift? if so it's down to forestay tension & sheeting angle. my boat goes to windward like a pregnant bucket because of lack of tension in the jib luff so i'm having the sail re-cut to suit.

 

[42_South]

One point not covered by learned colleagues - the boat has to be moving at speed to generate lift via the foils in the water.

If all above points are covered, don't forget to drop off to build speed and then gradually come up to windward.

Our boat is similiar to a Kerr 11.3 and we get huge lift using this approach and sail generally at 20 degrees app (according to our B&G's). Our fin is deep and relatively long in it's chord length, but very narrow, but it just won't work if your generating too much leeway...

 

[Aja]

I take it the keel is in line with the fore-and-aft line of the boat? I hasn't had a 'ding' at any point? That may have a detrimental effect in pointing ability.

Regards

Donald

 

[capn666]

Re: Deviation

Given that Jacket says he needs a new compass then it could well have a high deviation. If you tack through ~90 degrees you will often see noticeable differences in deviation if the compass is a bad one.

Depending on where he sails eg an estuary or river his checks may have been done only in sheltered water on consistent headings each time so may not have been truly random.

However, in this case he has checked it with a handbearing - so deviation is probably not the culprit here.