Wood, balsa

Insulation having high thermal endurance has been made from vitreous siUca fibers (see Ablative materials). Such material forms the basis for the 30,000 iasulatiag tiles, 125-mm thick, that protect the aluminum skin of the space shuffle. The tiles add a minimum of weight because the density of the iasulation is only 144 kg/m (9 lb/fT), similar to balsa wood. 

The Mosquito was a laminated wood monocoque design that although unusual, was not new. More uniquely, the monocoque shell was fabricated by gluing plywood skins to balsa wood core. This construction foreshadowed the popular honeycomb core/facesheet aluminum and composite designs of later years. Fuselage halves of the Mosquito were formed in closed wooden female tools (tools... 

Different core materials are used. They include foam, honeycomb core (plastic, paper, aluminum, etc.), ribs, balsa wood, filler spacers, corrugated sheet spacers, etc. Materials such as polyurethane foam, cellulosic foams, and polystyrene foams are widely used as core materials. Plastics, such as glass-reinforced polyester, are frequently used as the skins for panels. Different skin materials are used such as metallic skins alone or in conjunction with plastic skins. 

For millenia, hardness has been used to characterize materials for example, to describe various kinds of wood ranging from soft balsa wood to hard maple and ironwood. Mineralogists have used it to characterize differing rocks, and gemologists for the description of gems. Ceramists and metallurgists depend on it for classifying their multitude of products. 

Ingrid has two pieces of balsa wood. Piece A is 0.724 centimeters thick. Piece B is 0.0076 centimeters thicker than Piece a. How thick is Piece B ... 

Since the stiffness of a laminate varies as a cubic relationship with the thickness, there are alternate methods employed to achieve thickness - and hence stiffness - than by using multiple layers of fiberglass and resin. Lightweight core materials, such as end-grained balsa wood, high-density polyurethane foam, PVC foam, and honeycombed materials, are available. These materials are sandwiched in between layers of unsaturated polyester resin to achieve increased laminate stiffness. The common terminology used for this technique is sandwich construction . 

FIGURE 1.2 Effect of surface on evaporation of phenylacetic acid at 0% relative humidity and 20°C. a, montmorillonite b, mylar plastic c, glass d, cellulose e, kaolinite f, balsa wood g, stainless steel h, platinum. (Adapted from Regnier and Goodwin, 1977.)... 

Fiqure 10.2 Balsa wood models of oxy- and deoxyhemoglobin. The hemes are represented by disks. Note the increased separation of the f3 subunits on deoxygenation. This is a historic photograph from the heroic early days of x-ray crystallography. [Courtesy of Dr. M. F. Perutz.]... 

Balsa Wood Nitrated. W.de C. Crater,USP 2174914 (1939) CA 34,887(1940) proposed several expls mixts contg nitrated balsa wood of N content 9 to 11.5%, as for instance nitrated balsa wood, AN,... 

Found chiefly in the American tropics, this family is the source of kapok, balsa wood, some ornamental trees, and the popular Asian fruit, durian. 

Craft glue %-square-in. strips of balsa wood cardboard scraps X-ACTO knife colored posterboard nylon thread prepared in Activity 5.5 (or purchased nylon thread). 

Using the theme shape as the basis for all the shapes to be used in the sculpture, create a series of units (suggested number is seven or nine) in a variety of sizes and proportions from strips of balsa wood glued together. The shapes should be linear. You should vary the size and proportion of the shapes, but all shapes should be variations of the theme shape. 

Swint patented a low-density dynamite containing nitroglycerine (7-15 per cent) and finely divided balsa wood (5-15 per cent) used with ammonium and sodium nitrate. 

Kauh (K2, P2) assumed the applicability of the diffusion equation to describe the movement of moisture in the solid. He also took into consideration the surface temperature change from the time the solid is placed in the dryer until the time of completion of the drying process. He showed that the area for mass transfer at the surface was proportional to the f power of the moisture concentration for balsa wood. The results show that the internal resi,stance in the case of thin solids is very small. 

The data from about 50 runs on balsa wood were fed into the computer and the best value of the exponent of WlWe was calculated. The figure which resulted was 0.6, which checks the theoretical value. 

The correlation that is presented used the following critical moisture concentrations for all drying conditions. For balsa wood. Wo = 3.16 lb water/lb dry solid. For clay. Wo = 0.3 gm/gm dry solid. 

The correlation presented in Figs. 3 and 4 represent the data from about 500 drying experiments. These experiments were on balsa wood, clay, and about 30 different welding rod coatings. The original data are available in theses (Al, C5, G4, K2, S16). 

Experimental data from various sources (C5, K2, G4, S16) were taken for comparison. Kauh (K2) determined the drying schedules for balsa wood slabs of various thicknesses (, j, f in.) at different wind velocities (100-124 ft/min). It was not possible to apply boundary-layer theory to calculate heat- and mass-transfer coefficients because the length of the slabs was not recorded. 

Cheng (C5) studied the relation of the drying rate to drying conditions (balsa wood slabs were used for experiment). His data were utilized to show (Fig. 8) the effect of air velocity on the drying rate, and also to show the comparison between theoretical and experimental curves. Data from 15 runs were taken for comparison, but to avoid overcrowding of the curves, only three of these are shown. The value of the critical moisture content used was the same as determined by Kauh. Heat- and mass-transfer... 

Critical moisture content for balsa wood Slab thickness (taped edges)... 

A similar piece of balsa wood (K2) (run 23) with twice the thickness was dried at the same air velocity. The dry bulb was at 94 F and the wet bulb was at 74°F. Calculate the time for the j-in. wood to dry to 0.316 lb if both samples started at 3.16 lb water/lb solid (critical moisture). 

The handle can be made from any traditional knife handle material or it can. be machined from aluminum or brass bar stock. When completed, a hole Is drilled in the center of the handle and the blade is epoxyed In place. Use a quality brand of epoxy and allow 24 hours curing time before using the knife. A good way to determine the optimum handle shape is to first carve it from soft pine or balsa wood. When the right shape is found, it Is copied In the final material. 

Cut grip frame out of 5/ " plywood, using pattern lf. It is a good Idea CO first make this piece out of balsa-wood. This allows you to make changes in grip shape or angle. When the entire stock is completed and you are comfortable with the final shape, it Is duplicated in p1yvx>od. Drill four 1/8" holes and 7/16" takedown screw hole as shown. Taper the rear of the hole to accomodate the head of the screw. Drill hole for stock latch. 

Holes are drilled in the top surface of the table for the tube leading down to the pump from the potassium-hydroxide trap, the two Dewars holding the traps, the bottom parts of the stopcocks, and a tube leading down to the ballast volume (which should be covered with a wire screen or else well taped because of the danger of implosion). The Dewars are best held in place by blocks of balsa wood which have a hole cut for the Dewar to fit into and which are attached to the under surface of the table. The traps should be large and of a durable construction (Fig. 1-20). 

Phenolic foams were first used in Germany in the early 1940 s to replace Balsa wood for use in aircraft (2). Notwithstanding the fact that both phenolic resin and phenolic foam itself have long histories, newer applications have imdergone slow development. Quite recently, however, the heat resistance as well as fire resistance qualities of this foam have focused attention to its wide uses. 

Once the gel had been formed, they then added 60 parts by weight ammonium nitrate to the mixer, followed by two parts by weight of finely ground cork or balsa wood. The cork or balsa wood is the source of the entrapped air bubbles in the mixture. 

---