A Photo & Discussion Forum for Wharram Design Enthusiasts
last summer, while I was setting the mast I've notice different strain between the mast's shroud. How tight should they be?
Adriano, if you are using the traditional Wharram lashing system, as tight as you can get them. A good system that I use came from Makz of Siam Sailing: lead two halyards forward to your bows and tie them off at equal tension. Then use a rolling hitch to secure a line to one of the halyards, and then take the line around the other halyard and back again. Now pull this frapping line nice and tight and secure it. This will pull the mast forward; now re-lash the forestay as tight as you can. Release the frapping line and then release the halyards. You can then lead the halyards to the aft stems and repeat the process there.
This will enable you to easily get the side shrouds and forestay nice and tight.
I agree with Boatsmith. If they aren't as tight as you can get them, the mast head will sag off to leeward and you can stress the side of the mast casing. Also having them tight can make a big (like 10-15 degrees) difference in the pointing ability of the boat. The boat changes shape anyway under load, so the tension is always changing as you sail and the loads get distributed through the hull and beams, and there's plenty of stretch and give in the rig itelf. I also find the the mast loads and unloads as you go through the waves (witnessed by varying amounts of slack in the leeward shrouds), and there's less movement and shock loading if everything is tight to begin with.
We use the halyards to tighten them initially, then adding frapping lines (small 1/4 inch line) at the deadeyes to further tighten them once the shroud is tied off above the deadeye. Will try the frapping lines on the halyards next time we need to tighten them up (about twice a year) to move the mast forward; seems like a nifty trick.