It is really underestimated. Perhaps because its effects are not known, but the kicking strap often shows off in the same position it was at the departure time.
Actually, it is an important rigging because it not only allows to keep the boom low but it has also a central role in mainsail adjustment. A good knowledge of the kicking strap is important especially today that, on modern boats and not only on dinghies, mainsails are often equipped with no traveller or they have very small and not efficient carriages.
Few days ago, we saw how slacking the kicking strap is important in case of broach in order to rise the boom and spill the mainsail.
Vice versa, a right regulation of the boom in tailwind requires to haul the rigging in order to prevent the boom from rising. This is the first evident function of the kicking strap. But not the only one.
In fact, this tool makes the boom compress against the mast with a consequent bend – we are talking about modern masts designed to flex, so not stiff like on old boats – and a lot of influences on the mainsail.
So, let’s see what happens when we use the kicking strap. We have already said that, by hauling it, we push the boom downward. The first consequence is that we stretch and reduce the leech, that is the rear part of the mainsail. So, the mainsail gets flatter.
In the picture below, position A causes a larger mainsail than that one of position B, after hauling the kicking strap.
When we sail close to the wind, this function is carried out by the sheet. With a similar close-hauled angle and with a more hauled sheet we will have a littler bending, a more closed leech, a greater swerve and a more griping boat. The more eased is the sheet, the greater the bending will be; the more open the leech is, the less griping will be the boat. The first effect will be perceive at the wheel, which will get significantly lighter.
But everything is different if we bear away.
As soon as we finish sailing close to the wind, the sheet starts to be too loosened to keep the boom downward. This is the moment when the kicking strap conquers its central role in bending and regulating the mainsail. But how can we understand if the bending is correct?
According to a practical rule, if it is little windy and the sea is flat, the leech and the kicking strap must be stretched until the upper stick of the mainsail is parallel to the boom.
Moreover, also the flow indicators, if present at the end of sticks, must be parallel to the boom and they must not show turbulence. From this moment on, we must continue to maintain a good bending by hauling the kicking strap before hauling the mainsail.
We have already seen that, if we haul the kicking strap, the mast bends towards the bow in the same point where the boom is fixed, that is the gooseneck. What happens to the mainsail? Its lower part gets thinner and the part near the leech opens slightly.
So, if wind is stronger and we don’t or we can’t reduce or deflect with the mainsail traveller, we can haul the kicking strap in order to reduce the griping tendency and the swerve.
In summary, the kicking strap has an essential function. By hauling it, we reduce the mainsail and its bending. The boat will be less griping and swerved. So, an optimal bending is possible when the last mainsail stick is parallel to the boom.
Of course, effects change according to boats. On large cabin-equipped boats, kicking strap can be used only when you run on a beam wind. On dinghies, it is always essential and it must be set continuously.
In the past, it was a simple traveller. Today, there are a lot of models. The rigid one, now present on all medium boats, has added a new safety element because it allows to support the boom when you lower the mainsail, even if you forget to stretch the uphaul. This way, the boom will not fall on the deck.
Sometimes, kicking strap is used as uphaul even in the harbour stops. But attention, this is not a good thing; the risk is to damage the expansion spring inside the cylinder by reducing its expansion range.