Adjustable Backstay Tensioner
I added a split backstay adjuster with a 4:1 vang doubled through it's lower sheave to an 8:1 on my Hunter 28.5. It can easily crank in 4 inches of additional mast bend to flatten the mainsail in conjunction with full tension on the outhaul. Of course , on a mast head rig this also decreases sag in the headstay which flattens the Genoa and pulls the draft forward in the Genoa. This can result in increased difficulty in 'staying in the groove' as you steer up wind. The boat should be more forgiving with a little headstay sag. Your other issue of mast rake is more a function of how much or how little weather helm you experience. Increasing mast rake usually increases weather helm, and too much weather helm causes you to use more rudder and slows the boat. You and/or your sailmaker should evaluate how your mainsail fits your mast with the mast bend at its normal position and no additional backstay tension from the adjustable backstay. Your mast could have been set in place by an inexperienced yard crew , or the rake changed as a result of a change in the headstay or an impropper roller furler installation. If you can find a copy, an excelent book which includes these issues in tuning a rig is: "Designed to Win" by Roger Marshall, published by W.W. Norton & Company 1979.
