How do I know what the correct tension is for the side stays on my Hobie 18? what is the procedure for adjusting the side stays? Does this need to be done with the mast up? cat level? and facing the wind?

Thanks

They should be tight enough that the rig doesn't slam around in light air. I usually get my crew to pull down sharply and steadily on a trapeze rig while I put in the final pin on the shroud. I've seen people hang horizontally or even use their mainsheet blocks and boom on the halyard to tension put extreme tension on the rig. However, the leeward shroud is going to dangle like a leaf in the wind no matter how tight you make it - I think beyond some point you're just loading up the hulls unecessarily.

I think the leeward shroud gets loose when the rig is loaded because of mast bend. One can minimize the mast bend by tightening the diamond wires, but this will give you a fuller main.

D. Ho
TheMightyHobie18 1067

I guess they are OK then. The rig does not slam around in lignt winds at all. It was just that I noticed the leeward shrouds slacking and I figured that slack could probably be taken down a bit for an overall tighter rig. Regarding the mast bend though, I noticed that when my mast is down on the trailer it is not perfectly straight and is bowed to one side. Should I loosen one diamond wire while tightening the other until the problem is corrected? and that brings me to the same question. How tight should they be??

Thanks guys!

Diamond wire tension is another matter entirely. It is very likely that your mast is not straight because the diamond wire tension is uneven. Boat performance, particularly upwind, can be largely affected by diamond wire tension (i.e. mast prebend) on boats with swept spreaders.

I looked but could not quickly find an TheMightyHobie18 tuning guide reference on the net but once you have some basic specifications you should be able to measure your prebend a couple of ways. The BEST way is with a Loos gauge that measures tension on cables - adjust both diamond wires so they measure the same (somewhere, somebody should have a specification in pounds of tension). If you have raked spreaders, that is if they are made up from four bars that sweep toward the back of the boat, you can also measure prebend / diamond wire tension by supporting the mast horizontally on the ground with the spreaders vertical (one on the bottom pointing down and the other pointing straight up - this way gravity will not largely affect your prebend measurement). Run a light string from end to end of the mast from the tip of the mast luff track to the base of the mast luff track. Measure the displacement of this string at the spreaders. Adjust the diamond wire tension until the mast is even left to right and the displacment of the string, or prebend, meets the measurement.

The more serious racers will adjust their prebend to match the wind and water conditions for the day - more prebend (less power/more efficiency) for flat water and/or windy days, less prebend (more power/less efficiency) for light air and/or choppy water.

Thanks for the explanation Jake. In my case the mast is slightly bent to one side so if I put the mast with the spreaders pointing up and down then I think gravity will be influencing the shape of the mast. Should I just loosen one of the diamond wires to see if this straightens the mast or will I be compromising the strucural strength of the mast by doing this? Should I instead tighten the other side until it is straight? For a non racer (yet) Does it make much difference if the mast is slightly bent to one side??

Having the mast bent to one side will make a slight difference in performance between port and starboard tacks.

YES!, you are correct about having the mast laying like that influencing the side bend...I didn't explain that part well. You only need to rotate it between adjustments so you can sight down the luff track to check that the diamond wires are even and the mast straight side to side. Rotate back again to check the displacement. Or - first get the mast straight by adjusting either diamond wire, then adjust the prebend by making equal adjustments side to side.

The structure of the rig depends on having adequate tension on the diamond wires - but there is usually a wide range of acceptable tension. As long as they are 'tight' when the boat is at rest on the beach they will provide adequate structural support for the mast while underway.

The Hobie-18 is originally set up with loose diamond wires, not a pre-bend rig. The tuning guide specifies "tightness" by pressing the wires together to the mast. "Tight" meant they touch the mast about 6 inches to a foot above the lower mount, "looser" to various degrees meaning the wires touch a foot or so or more. This means the mast bends along the minor axis of the mast section, and the windward diamond wire will be loose.

Alternatively, many Hobie-18 sailors (me included) tighten the diamonds to the point that the mast doesn't bend side to side, but not enough to induce prebend. Then the downhaul produces mast bend on the major axis of the mast section (front to rear). I also set my spreaders for very little to no rake.

For the shrouds - in light air, a tight rig will inhibit mast rotation. Again, the original tuning guide has varying degrees of tightness to the shrouds, being tight only for big conditions. I tended to run mine a bit loose unless the wind was up.

If the mast has a bend to it - you might try to straighten it. There have been lots of posts on this board about this - try a search.

One thing to keep in mind about diamonds & mast bent to one side...try flopping the mast over 180 degrees to see if the mast now cuvres the other way. Such curving is normal with the soft rig when the diamonds and/or sidestays are loaded...the mast is in compression and flexs enough to pop to one side or the other. It does not necessarily mean you've got one diamond or stay tighter then the other.

Mike.