By the Numbers: Tuning the Rig on Your Small Sailboat

Tuning your rig: it's key

For boats with shrouds and stays, measuring and “tuning” your rig is key. Very few things in sailboat racing are 100 percent replicable. The wind, the waves and currents, how others’ actions on the race course may have affected your decisions, how strong and focused you felt… these all vary widely from day to day. But controlling the things you can provides a reliable base on which to set out to tackle all those other variables. 

Tuning the rig
Nikki Bruno and Bradley Adam work on tuning the rig on a Snipe. Nikki's using a Loos gauge to check rig tension on the shrouds. Special note on Loos gauges: Each one is unique and offers different readings, so be sure to have and use your own consistently!

While many dinghies (ILCAs, Sunfish, etc.) feature unstayed masts, most others use shrouds and stays to keep the mast in the happy zone (vertical). Adjusting the tension of shrouds and stays can help your boat perform better in higher (or lower) winds and sea states. Getting your rig settings to “base” lets you make your decisions starting from a known point. 

If you haven’t gotten around to tuning your rig recently, make it a priority. Maintaining a routine for how you measure your rig and keeping a log of your rig measurements, are equally important. I highly recommend this being an adventure that skipper and crew undertake together. It gets you both on the same page and can really help crews learn more about how change the rig can affect sail shape and thus boat performance.

Taking measurements

Before you even step your mast, take some measurements on your spreaders. Measure individual spreader length, from the mast to the shroud. If you’re new or new-ish to your class, check in with others to see where they measure to and from. That will help you later as you talk with fellow competitors in a shared language about what settings did and didn’t work well in a day’s sailing conditions. 

Spreader length helps control the sideways bend of your mast. Having your spreaders as long as possible makes the mast more powerful. But too long—that ends up pushing the middle of the mast to leeward, and that’s not good for a happy jib. Using the suggested spreader length in your sailmaker’s tuning guide for your class is a great place to start. But know that your crew’s combined weight may affect your decisions, too (smaller teams likely need to start depowering sooner).  

Also track your spreader “angle” by measuring the distance from one spreader tip to the other, with the spreaders hinged back all the way as if the mast were up with tension on the rig. This lets you track how far back your spreaders are set up. A large angle (where the spreaders don’t sweep back much) is very powerful and most appropriate for larger teams, while a smaller angle (where the spreaders can sweep back more, allowing the middle part of the mast to bend, flattening out the main) is better for smaller teams. 

Mast centering, rake, and pre-bend

Okey dokey, now that you have your spreader length and spreader angle numbers written in your notebook (you do, right?), step your mast and take a deep breath. Now make sure your spreaders are angled equally. Pull your jib halyard on and make sure there are no other influences (mast puller or pusher on boats that have those) on the mast, and back away from your boat a handful of steps. Try to line the shrouds up. Do they run visually parallel to one another all the way up? Good deal. If not, you’ll need to adjust them fore and aft until they do look parallel. 

Next up, is the mast itself centered? Use your main halyard to run a tape measure up the mast, and with the main halyard secured in the “sail fully up” position, measure how far it is from the top of your mast to the base of your port and starboard shrouds. Longer on port than on starboard? Take a few turns off your starboard shroud(s) and one on the port side. Measure and adjust until they’re even. 

Now the real head-spinny stuff starts. You need to make sure that the mast “rake”—how far the tip of your mast is from a point certain on the center of the back edge of your boat—is (at least for starters) at the recommended number from your sailmaker’s tuning guide. Pull your jib halyard on, making sure your mast pullers and pushers are off, until your mast rake is at the suggested number. Write that down This *may* be your upwind jib halyard setting, but don’t mark anything on your boat just yet. 

Pre-bend is the ideally graceful slight bend in the mast when you have jib halyard tension on; this causes the shrouds to tension, shoving the middle part of the mast forward just a bit. Check your mast pre-bend, again striving for the number in the tuning guide. Do this by moving the (main halyard still secured in the “sail’s up” position) tape measure forward and pulling it tight to the gooseneck area. Find the spot where the tape measure is farthest away from the mast; this is your pre-bend measurement. If it’s less than what the tuning guide calls for, you likely need to tighten your shrouds up. Write down your pre-bend measurement. 

Does it all come together?

Finally, the “does it all come together” part: Shroud tension. Use a Loos or other tension gauge to check your shroud tension. Adjust tightness to get to your tuning guide’s suggested “base” number, making sure to do so symmetrically. 

Mast rake, pre-bend, and shroud tension work together—changes in one of these elements affects the other two. Keep at it until you are happily at “base” for all three. This may take a while and can be frustrating, but know it’s time well spent! When you are happy, be sure to mark where your optimal jib halyard setting is (by marking where a certain spot on the halyard should go on the mast) and write down all your settings in your notebook. 

Use that notebook every time you set your mast up. If the numbers don’t make sense, there’s likely a good reason for it, so step back and take a deep breath. Making sure your “base” is really “base” is an important way to start a regatta. 

By Kim Couranz
About the Author: SpinSheet Small Boat columnist for more than a dozen years, Kim Couranz has earned several national and world titles in Laser Radials (ILCA 6) and Snipes. She has also raced J/22s, J/24s, and Ynglings on an international level.

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