Sail trim
We help you trimming your sails
About sail trim
The best possible sail trim is important for both doing racing and for cruising. For racing is speed essential, however VMG (velocity made good) when you sail up- or downwind is actually the most important. But for cruising a optimal sail trim is also less healing and more comfort.
Its quite common that people talk about the headsail (genua or jib) and mainsail trim as two independent sails. But its important to se the complete sail-plan as one sail with a gap in the middle. Because they have influence at each other and its the whole sail-plan height, the distance from front stay to aft leech on the mainsail and the total depth of the two sails together that powers the boat forward.
We are based in Mahon and with more than 40 years saling experience. Among them as professional sailor, building race sailboats and many thousand nautical miles on many boats. Then we have the experience, that we like to offer you, to power your boat forward. We are also pleasant to join you in a race.
👉 Contact us for a chat about sail trim
What we can do
- Talk about trim on your boat
- Look at rig and sheeting options
- Talk about improving of sheeting points
- Go out and sail with you
- Look at trimming of headsail
- Look at trimming the mainsail
- Look how the two sails work together
- Look at improving upwind VMG
- Look at the shape of your flying sail
- Look at improving of downwind VMG
- Look if your boat need gear optimizing
These pinpoints in basic what we can offer to help with and we are also open to hear if you have other wishes you need help with.
Sail trim in details
In the drop down menu below, we will explain more about sail trim.
Introduction to sail trim ->
Losing hights and back air.
Do you also have the experience, that the boat is loosing hights when you in light air have to sheet loose to get more power? Do also having problems with a lot of back air in the mainsail in strong wind conditions and when you pull the mainsheet to stop the mainsail flogging? then you have too much heeling? Then it could probably be avoided by changing the sheeting angles with in-hauler and barber-hauler.
Old rig designs
By previous mast head rigging boat design, it was quite common that the genua sheeting angles was between 6-8° and long distance cruisers and offshore racers had a second genua track further out. The mainsail was small and the genuas was large and it was normal to have several sizes genuas and with the large 150% genua you had light wind power and if a furling, then it was okay to reef due to the clew angle was close to 90° on the headstay. When the wind increased, the mainsail got reefed and the genuas was changed.
New rig designs
But new boats with fractional rigging, angled spreaders and some even with full with rigging has only 105-110% furling genua or jib (often on selftacker) and a large mainsail. Here it’s normally only the mainsail that get reefed and the genua or jib is the allround sail for all wind forces. That requires that the you can both trim the depth of the headsail and the twist and due to the steep sheeting angle its quite complicated. Because when you ease the sheet, the sail clew moves more up than forward with the result loosing the upper part of the sail.
Change of sheeting angles ->
Use of in-hauler
With the use of in-hauler you can change the sheeting angles closer to the center of the boat or with barber-hauler further out by open courses. That means that you can sheet the genua loose to get a deep shape, but still keep it close to the centerline, so you have maximum hight to the wind and you control the twist with the normal genua lead car position.
Increasing wind
By increasing wind you flatten the genua by pulling harder in the sheet and by overpower you move the genua lead car aft, to twist out the presure of the genua and opens the slot more so you have less backwind in the mainsail so you can better ease of the presure in the mainsail too.
Open wind angles
If the course starts gets more open, then you ease the in-hauler to move the sheeting angle out and by further open course you let the barber-hauler take more and more over. By new sport cruisers with short selftracker jib sheeting a barberhaul by open courses is a absolute must to avoid a flogging top by open courses. This flogging top can be hard on the sail, but its also very uncomfortable, because you feel the whole boat is shattering. Without barberhaul the normal procedure is to pull in the sheet to the top is steady, but then 2/3 of the sail is pulled too hard in and is overpowered in strong winds. Let us make you sailing faster and mor comfortable.
Where to start with trimming your sails ->
Start in front
You start where the wind hits the sail first which means to check the entry angle of the sail followed by the twist. Pull ind the head sheet with the mainsail in a not flogging trim. Then go slowly more into the wind to you luv tell-tails starts flogging and se if its the bottom or top ones that moves first. If the top ones moves first, then the headsail has to much twist and you must move the genua sheet lead car forward. If the bottom ones moves first, then there is too little twist and you must move the lead car backwards. If all tre set of tell-tails moves at the same time, then you have the perfect position of your genua sheet lead car in that side.
On the headsail (genua or jib) you normally also have some horisontal trim lines in a contrast color. So its from below is easier to se the horisontal curved profile. Its important that the max depth is never behind the center of the sail. You can move the depth forward by adding more tension on the halyard, which are normally necessary by increasing wind due to stretch in the sail cloth.
Wind twist
I write that side because the wind speed by the surface of the sea is much less than by the top of the mast because the wind gets slowed down by the friction of the sea wich is also creating waves. Therefore does the wind also have a down angle of approx. 10° which is why your boat also have the largest projected sail area by 10° heeling. But the wind does also often have its own twist which often can be 10-20° different between mast top and sea surface. Therefore don’t set you genua sheet lead cars equal in both sides without checking. Sometimes they have to be set 20 cm differently or even more. On electronic instruments, you can sometimes sail 15° app wind with a fantastic VMG on one track and only 45° app wind with a shitty VMG on the other track.
The mainsail importance to the total sail plan
The next to trim, is where the wind leaves the sail area which means the aft part of the mainsail. You have to see the two sails as one big wing with a gap in the middle. The hight of the rig is the length of the wing and the distance from the headstay to the aft leech of the mainsail is the with of the wing, also called the acceleration time, because the wind gets accelerated on the lee side due to the longer distance around the lee side. The depth of the sail plan is the distance between two parallel lines in same direction as the wind. One line touches the deepest point on the genoa and the other touches the luff of the mainsail. Therefore, when you sheet the mainsail at leeward, then you are reducing the depth of the total sail plan a lot.
Trimming the mainsail
On race boats with traveller the mainsail trimmer often use the traveller more than the sheet in strong winds. in light winds you often have the boom as close to the center as possible and then use the sheet and kicker to control the trim and the tell-tailes at the aft leech tell you how hard you can sheet. They shall fly free aft the sail and only short in between fly around to the leeward side. Never around to the back side, pull a bit, always around to the back side, release a bit. Here again the top and bottom is important. If the top one is always around, then you must twist the mainsail more by releasing the kicker and if not enough, you must release the mainsheet a bit and move the traveler up, if you have such one. On race boat the boom can be even at luw-ward and the top twisted quite a lot, especially with fat head mainsails. The mainsail outhaul is important to adjust the depth on the mainsail. In very light wind it must be quite loose to have a lot of shape in the mainsail. But already from medium wind you can stretch it good out, because a very hollow mainsail creates turbulente drag.
On the mainsail you normally also have some horisontal trim lines in a contrast color. So its from below is easier to se the horisontal curved profile. Its important that the max depth is never behind the center of the sail. You can move the depth forward by adding more tension on the halyard, which are normally necessary by increasing wind due to stretch in the sail cloth.
By upwind sailing in races in hard wind, it can be okay that only the aft part of the main sail are in use in a way, where the mainsail is flogging a bit every time the mast moves forward due to boat moving in large waves and the aft 20-30% is pulling when the mast moves aft, when the boat is in a wave valley start moving up-wave. Where in cruising it will be normal to reef much before.
Control check
Now its time to look at your head sail trim again to see if the mainsail has affect on the headsail tell-tails by going to much upwind again. If the still move on the same til, you have the basic working trim for the hole sail plan and from here its a continuing adjusting after wind speed.
Importance of VMG ->
VMG = Velocity made good is the speed you are approaching your target against the wind or with the wind. If you can point your target, then your boat speed and VMG is the same. By upwind you have to sail a certain angle to the wind which increasing the distance. As closer you can sail to the wind, as shorter is the distance, but also the boat speed. Therefore its important to find the best VMG by different windspeed and sea state. There is notning worth sailing 10 knots from side to side if you dont come forward. Modern boat electronic instruments has a VMG calculator so the VMG instrument is as important to look at as the boat speed is, if not even more important.
By sailing downwind you can’t sail faster then the wind moves when you just follows the wind sailing 180°. But if you cut out and go 160° or 150° then you increase the boat speed and sails much faster than the wind, but also a longer distance. So its important to find the right balance between increasing speed and increasing distance.
Modern instruments can also show you the VMG so you can se where you have the optimal angle combined with boat speed and distance. If you dont have modern instruments with VMG, then you can by practising with different angles and different wind forces make your own VMG scheme in Excel spreadsheet. If you have different downwind sails, you need a scheme for each sail.