Figure 1-35.  The skin is an integral load carrying part of a stressed skin design. Figure 1-36.  Fuel is often carried in the wings. or external bracing requires that the skin share some of the  load. Notice the skin is stiffened to aid with this function. Fuel is often carried inside the wings of a stressed-skin  aircraft. The joints in the wing can be sealed with a special  fuel resistant sealant enabling fuel to be stored directly inside  the structure. This is known as wet wing design. Alternately,  a fuel-carrying bladder or tank can be fitted inside a wing.  Figure 1-36  shows a wing section with a box beam structural  design such as one that might be found in a transport category  aircraft. This structure increases strength while reducing  weight. Proper sealing of the structure allows fuel to be stored  in the box sections of the wing.  The wing skin on an aircraft may be made from a wide variety  of materials such as fabric, wood, or aluminum. But a single  thin sheet of material is not always employed. Chemically  milled aluminum skin can provide skin of varied thicknesses.  On aircraft with stressed-skin wing design, honeycomb  structured wing panels are often used as skin. A honeycomb  structure is built up from a core material resembling a bee  hive’s honeycomb which is laminated or sandwiched between  thin outer skin sheets.  Figure 1-37  illustrates honeycomb  panes and their components. Panels formed like this are  lightweight and very strong. They have a variety of uses  on the aircraft, such as floor panels, bulkheads, and control  surfaces, as well as wing skin panels.  Figure 1-38  shows the  locations of honeycomb construction wing panels on a jet  transport aircraft. A honeycomb panel can be made from a wide variety of  materials. Aluminum core honeycomb with an outer skin of  aluminum is common. But honeycomb in which the core is 1-18$^{Sealed structure fuel tank—wet wing}$