Merit 25 Tuning Guide

Merit 25 Tuning Guide

The Merit 25 has had two different rigs; the Kenyon mast which is stiffer and the Ballenger mast which is bendier. There is not a lot of difference in the initial set up of the two rigs but there is quite a bit of difference in how the mainsails are cut for the different masts. Be sure to let your sailmaker know which one you have when ordering a new mainsail

The starting point for our sails should have the mast set up with 16” to 18” of mast rake. The final position will vary depending on the amount of wind you sail in. This is measured by hanging a weight on the end of the main halyard and measuring how far aft of the mast it hangs at the deck level while you have just enough backstay tension to take the slack out of the backstay. The boat needs to be floating level on its waterline when you do this so if you have a motor on the transom or a lot of weight in the bow you will need to move things to get the boat level. You want to adjust the rake so that you have just a slight amount of weather helm and “feel” in 6 to 7 knots of wind. This is done by adjusting your headstay turnbuckle. The more mast rake you have the more weather helm you will have. As the wind increases you will want to decrease mast rake to keep the boat balanced; as the wind increases and the boat heels more the weather helm will increase. You don’t want to sail with any more rake than it takes to give you just that small amount of helm because the more helm you have the more drag it creates. As the wind gets into the 12-14 knot range you will want to shorten the headstay by about 1” and as the wind gets into the high teens you may shorten it as much as 2”.

Upper shroud tension will vary slightly with crew weight, but the goal is to have the mast stay straight side to side up to the point where you start to get overpowered, about 10 knots of true wind. After that is alright if the top of the mast starts to fall off to leeward a little bit because that will help depower the rig as the wind builds. Using the Loos “A” Gauge a good starting point is around 24 to 26 on the cap shrouds. The lower shrouds should be set at about 22.The aft lowers control the amount of pre-bend in your mast. It is best to have these adjustable to give better control of your headstay tension, but if they are not then set them at 18 when you have enough backstay on to bend the mast 1.5”. For one of our mainsails on the stiff Kenyon mast we recommend .75” of pre-bend unless you are sailing with a very light crew and need a little flatter mainsail. With the more flexible Ballenger mast set up with 1” to 1.5” of pre-bend.

Your goal is to set the boat up for medium air, 8 to 10 knots of wind, so that when sailing the mast stays straight side to side, the mast is bent just enough to properly shape the main, and the headstay sag is right for your genoa. Since the mast needs to be able to bend through at least a 4” range you can’t set up the rig with the lowers really tight

When sailing in winds over 12 knots getting enough headstay tension to keep the genoa from being too full is important. Up to that point the rig should be set up so that the amount of backstay it takes to get the main flattened for the conditions will give you enough headstay tension for the genoa. Over 12 knots you should start to tighten the forestay. This gives you three benefits. By tightening the headstay as the wind builds it will give you more tension when the backstay is two blocked. Pulling the mast forward with the headstay will also make the aft lowers slightly tighter which will help to keep the mast from over bending for you main when the backstay is two blocked; and it will also move the center of effort in the mainsail slightly forward which will reduce the extra weather helm you have as the wind increases.

See the table below:

UPWIND:       to 6 knots     7 to 10 knots   11 to 13 knots   14 to 18 knots   18 and Up


Headsail         155%             155%             155%             140%             95%


Chainplate      6”-4”             4”-2”             touching         touching         –


Spreaders       6”-4”             3”-2”             2”-1”             1’-0”              inside 4”


Backstay           loose             light               medium          max               max


Headstay        set for proper rake                                     add 4-6 turns  add 8-12 turns


Boom            down 2”         0                    0/down2         down 2”-8”    down 4”-12”

From centerline


Traveller        up 12”           up 8”-12”       up 4”-8”         up 4”-down 4” played in puffs

From centerline


Top Batten      slight open      parallel           parallel           slight open       Twist to keep flat

The Chainplate measurement is the distance the foot of the genoa is sheeted out from the chainplate. The Spreader measurement is the distance the leech of the genoa is sheeted from the end of the spreader.