The preferred material to make the longbow was yew, although ash, elm and other woods were also used. Gerald of Wales speaking of the bows used by the Welsh men of Gwent, says: "They are made neither of horn, ash nor yew, but of elm; ugly unfinished-looking weapons, but astonishingly stiff, large and strong, and equally capable of use for long or short shooting". The traditional construction of a longbow consists of drying the yew wood for 1 to 2 years, then slowly working the wood into shape, with the entire process taking up to four years. The bow stave is shaped to have a "D" cross-section. The outer "back" of sapwood, approximately flat, follows the natural growth rings; modern bowyers often thin the sapwood, while in the "Mary Rose" bows the back of the bow was the natural surface of the wood, only the bark is removed. The inner side ("belly") of the bow stave consists of rounded heartwood. The heartwood resists compression and the outer sapwood performs better in tension. This combination in a single piece of wood (a self bow) forms a natural "laminate", somewhat similar in effect to the construction of a composite bow. Longbows will last a long time if protected with a water-resistant coating, traditionally of "wax, resin and fine tallow".