Keel-stepped masts

Standard configuration: Seldén calculates the standard hand-tightened forestay length for a 1° aft rake. The normal location of the heel is vertically below the centre of the deck ring which makes for 0.5% pre-bend. You can adjust both mast rake and pre-bend to suit your own ideas, based on the following principles. The length of the forestay determines the mast rake. For 1° rake aft and a straight mast, the heel must be located 0.017 x Q forward of the vertical line from the centre of the deck ring. We call this point B. The mast must not, however, be straight. It should have a certain amount of pre-bend. 0.5% of the fore-triangle height is normal. To set this amount of bend, the heel is located 0.017 x Q aft of the B point. This is point C. The backstay is then tensioned to 15% of its breaking load.
Forestay attachment. Forestay hand-tight. The location of the heel for rake and pre-bend of keel-stepped mast A keel-stepped mast must take up an even curvature (convex forward) right down to the mast heel. This means that the mast heel must be located aft of a line from the forestay attachment on the mast through the centre of the deck ring (dashed line). Before you raise the mast, it is difficult to decide precisely where the mast heel should go. Start from the guide position as described below. The location of the mast heel can usually be adjusted later.
Aft DeckHeel d B aCQFH v° Standard values v = 1°a = 0.017 x Q (17 mm per meter Q) d = Depth of curvature 0.5% x FH d must not exceed 2% (1.5% for in-mast furling).FH = Fore-triangle heightQ = Distance keel to deck Adjustable T-base. Release rigging tension and adjust with mast still in place. Convex underside of heel plug – distributes compressions load on the mast section. 22