Went sailing coupla days ago.......when Missus and I started sailing a little while ago the forum suggested I sail on mainsail only
'til I got used to things, mainsail only meant I didn't have to tack. Fair enough!!. However I chose to use the headsail instead b/c
it saved me having to furl the mains'l back on the boom.
On Wednesday the breeze was 20knts and Missus was doing a bit work below deck, so I said "Darl, I'm going to hoist the mains'l
and just use that". So I did.
The result was the boat moved forward at about 1 knt, barely enough to steer. The breeze was a Nor'easter and I was heading
due East. I noticed I was being blown closer and closer to Scotland Island, so I yells to Missus "I'm going to pull out a bit of headsail".
So I did.
My headsail is 150% and a furling/reefer, so, b/c it was breezy I pulled out to about 90% and reefed it there.
Well all of a sudden we were moving along at a good rate of knots and spent the rest of the day at that sail setting. A big bonus was the
ease of tacking.....with the headsail shortened it was so easy, I did it single handed...no problem.
So the question is.....why was the boat so slow under mainsail only, and so quick with a bit of headsail added.??.
If I ever have to replace the headsail would it be better to go for a 100% rather than a larger sail b/c it seems to gallop along on the
smaller sail and tacking is SO much easier.

Do Dolphins Ever Sleep. If you want to know the real reason, get this book Sam. Has lots of interesting facts and a section devoted to sailing. It talks about why sails work and not what we all commonly believe and talk about at the yacht club bar. It also explains why the combination of the Main sail and Head sail are more effective.

You can google the info on the internet but this book brings it back to a lot simpler format than trying to get your head around Bernoulli and Newtons laws for lift.

I never realised that it is that same principles that enable a ball (cricket or base ball) to curve through the air and that they have actually made boats with spinning vertical cylinders (no sails) that could sail up to 25deg of the wind. The book explains it all plus heaps of other trivia to bore the $hit out ya mate over a few beers.

Thanks Crusoe.....I seem to remember reading a book once. I certainly know the high and low pressure principle,
I discussed this on the forum a little while ago. What I don't understand is why my boat didn't go with the mainsail
close hauled in 20 knots of breeze, in fact it was going sideways faster than it was going forward.

how much weather helm did you have with just the main up?

Good question Fishy. I'm not quite sure what weather and lee helm is, so bear with me. It seems that
going due East on a Nor'easter I was having keep the tiller over to the Stb'd side to keep away from the lee shore.
Ultimately I had to use the headsail to get speed up so I could steer away from the shore. Does that make sense.??.

My understanding is that, most boats will round up, (point) into the wind if you let go of the helm. The amount of effort required by the helmsman to stop the boat rounding up is referred to as "Weather Helm"

OK Crusoe.....It seems to be the opposite with me. I was trying to bring her into the wind more to get away
from the lee shore. The mainsail looked like it was full of wind...it wasn't luffing, but the boat just wouldn't go.

My understanding is that most boats, that are designed to be sailed with a head sail, point better to windward with the headsail in use. If you only have the main up, then your boat speed will drop off sooner as you come closer to the True direction of the wind, than what it would with the head sail had been in use.

Leeway is a combination of forward boat speed and your sideways movement through the water. For example if your are sideways movement is 1 knot and your forward movement is 5 knots, then you leeway will be 12 deg. If your forward movement drops to 2 knots then you leeway will be 26 deg. And 45 Degs of leeway if your boat speed drops to 1 knot.

Yes, all boats move sideways through the water when the wind is forward of the beam, and this is why you need to point a bit higher than the mark you want to head for.

Good call on putting up your head sail to get your self away from the lee shore.

I usually go down wind a little till the boat speed increases Sam Then point up
I was not there so can say if that happened

Sam, may I make a comment without everyone jumping down my throat.

Maybe a short story will explain it better, my sister recently at an age where childhood things are appealing again (or an age where she should know better), in her case sailing, she got a boat, jumped on, could not work out what why and what the "stupid" boat was doing wrong. It was all the boat's fault. Not sure how she figured that.

Now as a sailing master and sailing coach she got very little sympathy (nada, nil, zip) from me, I sent her back to a sailing school to re-learn the basics, learn about trim (fore and aft, athwartships, centreboard (not really relevant in her case, rudder and of course sail trim).

Now sailing for her is fun again.

Maybe what I am saying is that some time spent with a sailing school/instructor etc on you boat or theirs would be time well spent.

But to answer your question, the reason it sails better with headsail has to do with "slot effect". The reason it tacks better is that the head is "driven" thro the eye of the wind. As for smaller headsail, me personally would not go smaller, I would just reef as required.

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samsturdy said..
OK Crusoe.....It seems to be the opposite with me. I was trying to bring her into the wind more to get away
from the lee shore. The mainsail looked like it was full of wind...it wasn't luffing, but the boat just wouldn't go.

When only using the main sail, the pulling force produce by the main sail (centre of effort) is behind the mast. When close Hauled with only the Main Sail, its a bit like trying to tow a boat, not from the bow, but 2/3 of the way back along the hull. The effect gives some forward motion, but can significantly add to your leeway.

Once you start using the head sail, the combined "centre of effort" from both sails, ends up forward of the mast and boat speed increase and leeway decreases.

That's how I see it, but could be wrong again.

Simply you were pointing too high. Nor east wind and you were trying to go east, you were only 45 degrees off the wind. A well trimmed boat that points well might get 45degrees, you would be aiming for 60 degrees or so. With only the main and no slot effect and the boat trim out of balance you won't do better than 65-70 degrees.
If you were really 60 degrees off the natural wind, which you could well have been, once you had the boat in trim with both sails set away she went.
On the S&S34 the main just balances the boat, nearly all the drive is from the heady.
On headsail size. The S&S No1 is about 160%. This is too big on a furler as the amount of sail wrapped on the furler when partly furled destroys the sail shape and air flow. I went for a 130-135%. I missed out on a bit in light breezes below 10kts, she is beautifully balanced above that and I can furl it right down whole retaining shape and air flow.
Hope this helps.
I will go out with you and the missus for a day to help you set the boat up. Send me a pm.

Hi Sam

Could you p l e a s e do yourself a favor. Purchase a sailing book and read it! You could get a second hand one at Goulds in Newtown for less than 20 bucks.

It is awfully hard to converse with one who does not speek ones language.
Most of the guys here bend over backwards trying to help you but they only could help if you try to help yourself.

Apparently it's a thing called apparent wind...

I suggest you get a sailor to jump on board and teach you a few things or join a sailing club!

You're on a course heading disaster unless you have experience and sailing knowledge..

Thanks all. Great response from everybody as I would expect. I think MB has nailed it, I was thinking
I could sail closer to the wind than I really can. As HG said, go down wind a little. I was, however too
close to Scotland Island to do that, but, I did make a decision and took action to remedy that situation,
not that we were in danger or anything, but it was a good excercise.
Now me and Missus are oldies, we love the water, especially where we sail on Pittwater. At our age most
of the old rock stars are dead, but not us. We want to keep our brains and bodies active and enjoy pitting ourselves
against the odds. Of course we don't want to be stupid about this, but, asking and getting advice from the forum,
then going out and putting it into practice is magic. The main thing is we ENJOY doing it, and I am fully aware
I've only got to say the word and half a dozen of you will jump aboard.
I thank all of you for your help and concern, but me and Missus with your help are using our grey matter and
we're doing great. Just keep helping when we need it........it's keeping us alive.

Hi Sam
Do yourself a favour and buy yourself some telltales , attach them to your sails , learn how to read them you will be sailing with the best of them in no time .
Sailing a boat with just the main or just the headsail isn't a good idea .

Cheers
Al

You might have been too close to the wind, but you said you had a sail full of wind, so equally you might have stalled the main, and you might have got some way on by easing the sheet. East in a NE, about 45 degrees true, no way on so apparent wind not much less. You should be able to point higher than that.
Best advice, get some tell tales and learn how to read tham.

As suggested, learning to read tell tales and knowing how to trim sails is essential to getting a boat
sailing along. Also a wind indicator is a priceless and simple must have bit of gear for a sailboat.

or Sam, since you mentioned you have a furling headsail, maybe put the main up and try furling different amounts of the headsail, so you can still be confident sailing with both sails up.

Ideally the boat will be better balanced if you have some of each.

Just quickly;

To learn the theory of how sail work, stroll over to the Boat Design Forum and read the stuff by Tom Speer, Mikko Brummer and Mark Drela, and ignore just about everyone else.

Tom is a Boeing aerodynamic engineer who was involved in designing the winning rigs for the last two America's Cup winners. Mikko is a sailmaker who does CFD work and cuts gold medal winning sails. Mark is a MIT aerodynamics professor who worked with Tom on the America's Cup rigs and has also designed world record holding human powered vessels and aircraft. They are great on theory and explaining it, whereas there is a huge amount of BS about sail trim going around.

As Tom, Mark and NASA say, there are different ways of understanding how sails work. Bernoulli's theorem is one way. Another way is to consider is as Newtonian lift - as the air hits the sail, the air is directed backwards. As Newton said, every force creates and equal and opposite reaction, so the boat goes forward. As Tom Speer explains, the task then basically becomes directing the right amount of air in the right direction, with the least possible drag.

Anyway, one of the other things that theory and practise show is that the wind "upstream" of a sail is already "bent" by the sail - the wind to windward of the sail has already changed course a bit. When sailing upwind, the jib alters the direction of the wind coming onto it, and also alters the wind coming over the mainsail. The air coming onto the jib is also affected by the flow heading into the main.

This interaction basically means that boats with jibs can (and sort of must) pull the mainsail on tighter - and boats without jibs normally (all else being equal) must ease the angle of the mainsail out. If you take the jib down and leave the main in the same trim, it will become overtrimmed. The boat will also become underpowered, all else being equal.

Think of the air flowing over a sail. If it comes in at 50 degrees or so, the air will struggle to turn around the front of the sail - the flow will break down into a mass of turbulence over the lee side. That's why telltales work - they show you the flow over the sail. The air flowing over the windward part of a mainsail that is trimmed in normally will follow the curve of the sail and get directed partly to windward, rather than flowing aft. The sail will work like the wing of a stalled plane - but instead of crashing you will go slow.

So to sail under main alone, make sure the traveller is well down and the mainsail is at a wider angle to the centreline than it would be if the jib was up. That will allow air to flow over the sail properly, and also ensure that the air flowing off the back of the mainsail (which is really important) is flowing towards the back of the boat, and will push it forward, rather than flowing back to windward too much.

As an example, check a dinghy sailing - a Laser has the main eased right out to the gunwale, a Tasar or sloop has the main close to the centreline.

As others have said, go out and read stuff on sail trim - not knowing how they should be trimmed is like a pilot not knowing how wings work.

Also, rule of thumb - if the boat is not going, head closer to a reach and make sure that the sail is eased a bit. Also, learn the way telltales work - they should be flowing backwards. If the telltales on one side of the sail are flicking around, move the tiller to that side (when sailing upwind) or take the sail to that side (downwind) by easing it or winding it in.

HI Sam,
If you get a quiet moment, read carefully what Chris and MB wrote, that's a lot of info but well communicated.

I hope this pic might help describe some of the effect of the headsail has on bending the wind favourably for the main.
This "slice" of air flowing over the leeward side of the mainsail starts off 60cm to windward of the centre line of the boat.
The higher the airflow speed over the sail the more lift it generates. The airflow over the main is accelerated by the effect of the headsail.
This shows the effect the headsail has on the mainsail, the result is a gain in more lift.










Credits for the analysis and imagery go to W&B sails.

It's not just sails! you need to think of your boat as a whole! what is it trying to do. Set your sails perfectly whilst not moving, you will initially go nicely leeward with the keel stalled, the rate depending on the balance of the boat and the type of keel/rudder.

Just about any well designed boat can be sailed reasonably well on main alone. You can't point as high, but you can move along and it's not hard.

For a beginner, try keeping the engine running, go straight into wind and hoist the main, use the engine to get some forward speed whilst bearing away until the sail takes over. You will notice the boat heel over as the main powers up. At this stage you have forward speed, good flow over the keel and rudder. You are in control and can then put the engine in idle or off.

even if intending to use the headsail as well, hoist the main first, get moving using engine if needed, and then unfurl the headsail. The main will best be hoisted when head to wind, unfurling the headsail can be done at any point of sail at any time.

I would not not get too bogged down in it all, you need some tips to get you going and just a bit of understanding. Lots of people sail adequately fine with almost absolutely no idea of the theory behind it, they just build and build on expetience.

Righto all....some really excellent info there, if somewhat technical. I love that you blokes endeavour to to get
to go to the 'nth degree of the dynamics of this sailing business.
I didn't realise that easing the mainsail would have been beneficial but thinking about it I suppose it would have
the same result that MB said about coming off the wind a bit more. Had I not been able to deploy the headsail to
get some speed to steer and being on a lee shore I suppose easing the mainsail would have achieved the same thing.
Of course I could have started the engine if push came to shove but I chose to take the headsail way out of the
situation just to prove I could.
Having said that though, next time I go out I will start off mainsail only and try sailing close to the wind until it
stalls and then ease of the mainsail 'til she moves forward.
I do have telltales and I sort of know that if they are horizontal then things are OK, but how to get them horizontal
when they want to be is another question.
Sail trim.....yes, paramount, but, with you guys there and whole lot of practice.....we'll get there. Thanks everybody.

Hi Sam
Google a book called "The Sail Trim Users Guide" by Don Gillette.
It would have to be the simplest and clearest guide to how and why you do things to make your boat go that I have come across.
Everyone that I have lent it to has either bought their own copy or written down relevant parts.
There is no tech talk just good clear speak!!
Not affiliated in any way with the author ,just really impressed.
Cheers and happy sailing

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samsturdy said...

Righto all....some really excellent info there, if somewhat technical. I love that you blokes endeavour to to get
to go to the 'nth degree of the dynamics of this sailing business.
I didn't realise that easing the mainsail would have been beneficial but thinking about it I suppose it would have
the same result that MB said about coming off the wind a bit more. Had I not been able to deploy the headsail to
get some speed to steer and being on a lee shore I suppose easing the mainsail would have achieved the same thing.
Of course I could have started the engine if push came to shove but I chose to take the headsail way out of the
situation just to prove I could.
Having said that though, next time I go out I will start off mainsail only and try sailing close to the wind until it
stalls and then ease of the mainsail 'til she moves forward.
I do have telltales and I sort of know that if they are horizontal then things are OK, but how to get them horizontal
when they want to be is another question.
Sail trim.....yes, paramount, but, with you guys there and whole lot of practice.....we'll get there. Thanks everybody.

Unfortunately I don't think you got what we were saying. Easing the main won't help if you are pointing too high. It will just luff and flap and you will stop dead. You need to bear away from the wind and then ease the main sheet.
Although you might pick things up from people on here nothing will compare to some instruction. Theory, demonstration and then practice.
Seriously, either take up my or somebody else's offer of a day sail, or get some lessons. You have done well so far but sailing can be a dangerous past time. Broken bones, skinned or lost fingers or going overboard all await those whose boats get out of control. None of us want to see you or the missus suffer an injury. I am available many Fridays through to Mondays if you wish. There are others on here who could also help you out.
Take advantage of this resource.

Yes I agree, with those saying get some instruction . Sam you will notice the difference , when doing the right moves while being shown how when and why . your learning curve will get way steaper !
Then the fun will be funner !!!

5 minutes of instruction will be enough. One nice day with a light breeze and main only. Practice sailing up to your mooring and leaving your mooring. Learn how to park alongside your buoy, sail backwards etc.

OK,OK. We were on the boat yesterday (working not sailing). The problem Missus and I have
is we tend to decide on a sail day at very short notice. Literally wake up in the morning, 'oh
look, the sun's shining let's go to the boat'. It's awkward trying to organise a meet when you
operate this way.
Conversely, if we organise a day and the weather is inclement, we won't want to go.
Now MB, you are the logical choice for a lesson and I will endeavour to get you aboard whenever.
Knowing the days you are available will help a great deal but I can only forecast ahead using the
local weather forecast to try and pick a day.....does that suit ??.

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samsturdy said..
OK Crusoe.....It seems to be the opposite with me. I was trying to bring her into the wind more to get away
from the lee shore. The mainsail looked like it was full of wind...it wasn't luffing, but the boat just wouldn't go.

with just the main up sailing into the wind & depending on the boat, the wind might just push you rather than pull. If you head too much into the wind too soon with no momentum you wont move much. Almost like in a hove to state. if you only had the jib up youd probably lose the bow, as in the boat will get pushed around. both sails up, into the wind is best. downwind or on the beam is a different story. Still though in my limited experience the boat works better in most conditions with both sails up. I was doing what youre doing too on my first lil 22 footer. against the wind id have to use the engine as well as i was only using the main. Once i started using the jib as well it was a beautiful thing. If you feel youve got too much sail up then use less jib and reef your main. better to decrease sail area overall. Dont decrease sail area by not have 1 of them up. You need to be balanced fore and aft of the mast. I would rather sail in 50 knots with a storm tri sail(tiny amount of main) and a storm jib, than say just a bit of jib or main.

OK got that Steve. Sounds like you played around a bit too when you were learning.
Good fun, but if I don't understand what's going on I don't mind showing my ignorance.
as someone said a while ago....it's NOT asking the questions that's foolish.
At the end of the day, I just want to be able to sail competently without scaring the Missus.

I see some people sailing catamarans downwind with just the headsail , I shudder to think what will happen if one of the crew goes over the side . Absolutely no chance to sail back to them with just the main.

Al