The woods shovm in Table 1 have been selected from a large number of 

 species for which mechanical testing in both the green and air-dry condi- 

 tions has been completed. In addition to the more important mechanical 

 properties, the table shows weight per cubic foot, radial and tangential 

 shrinkage, resistance to checking and splitting upon weathering, decay 

 resistance, and marine borer resistance. Relatively few of the species 

 listed, however, have been subjected to marine borer testing. 



Species Suitable for Durable Above-iater Construction 



The most suitable «f these woods from the standpoint of durable above-water 

 construction are grouped in three classes — Greenheart — ^^^/hite Oak — Southern 

 Pine — Douglas Fir — on the basis of approximate strength properties and are 

 discussed individually in this section. Most of these woods are considered 

 in greater detail in other reports on this project (3, 5^ and 8). Timbers 

 of the Mevj World (6) has been drawn on freely 3Sf a source of information 

 relative to the distribution and character of the timber. 



Very strong woods (Greenheart class) 



l.Almondro ( Coumarouna oleifera ), Gumaru (Coumarouna odorata ). These 

 closely related species are combined here for discussion. Almendro is 

 coiranon to very plentiful in the lovfland forests on the Atlantic side of 

 Central America from Micaragua to Panama, The tree is commonly large, 

 sometimes reaching a diameter of 6 feet and a height of 180 feet. The 

 bole of mature trees is virtually cylindrical and clear for 50-70 feet 

 above the heavj'- buttresses to the first massive limbs. Because of their 

 large size and the hardness of the wood, Almendro trees are frequently 

 left standing in areas temporarily cleared for agriculture, 



Cumaru, the usual name for Tonka Bean in Brazil, is common in many-forest 

 areas in Venezuela, the Guianas, and the Amazon region of Brazil. The 

 trees are frequently l| - 2-| feet in diameter and 80-120 feet in height. 

 The cylindrical bole is generally clear to heights of 60-80 feet. 



The wood. of these species is similar to that of Greenheart in density and 

 strength. Shrinkage is low relative to its density and resistance to_ 

 checking and splitting is high. Timbers of this genus have a reputation 

 for outstanding durability v.ith respect to decay, Cumaru has proved to 

 be one of the best crosstie ^.Joods in Brazil not only because of its dura- 

 bility but also because of its freedom from splitting. Both woods are used 

 for heavy construction especially vrtiere durability is a factor. Because 

 of their somewhat oily nature and the ability of the wood to acquire a 

 smooth, polished surface under conditions of heavy wear, Almendro and 

 Cumarif have been tested as Lignum Vitae substitutes. 



2. Bulletwood ( Manilkara bidentata). This species is common in northern 

 South America, Panama, and parts of the West Indies. Other species of 

 Manilkara and closely related genera also occur throughout this range 

 and extend through Central America. These related species are sometimes 

 confused with Maiilkara bidentata . The Bulletwood tree is typically large, 



T - 2 



