The mechanical design of the structure of the delta wing can be divided in the following parts:

01- Main frame
02- Triangle and king post
03- Bowsprit
04- Deflectors
05- Cables assembly
06- Rflex lines
07- Elliptic tips
08- Truncated tips
09- Washout and sprogs
10- Noseplate assembly
11- Rear keel
12- Kingpost assembly (top and bottom)
13- Downtubes - keel assembly
14- Downtubes - control bar assembly
15- Crossbar center assembly
16- Crossbar - leading edge assembly
17- Hang point assembly
18- Variable geometry and compensators
19- Others

Each part includes a varied group of individual pieces that can be assembled with different design options. It is necessary to know the different options of mechanical and select the suitable in our design. The LEHG program will take into account all these groups and select the appropriate settings for each sub-type chosen.

To start, we will study the options for the groups 13 (Downtubes - keel assembly) and 16 (Crossbar - leading edge assembly).

13. Downtubes - keel assembly

In this section, let's sketch the 7 sub-type, usually found (see mentioned examples).

Figure 1. A simple and effective method is to use a special piece of adaptation at the top of the downtube, which allows rotations around the Y-axis (keel) and the X-axis (horizontal and perpendicular to the keel). The bolt (normally an AN5 or M8) can traverse directly the keel by the middle of the tube. Examples: Airborne Sting 2, Icaro2000 Laminar 13-14, La Mouette Sphinx.

Figure 2: A small variation is to add a saddle or keel bracket made from forged aluminum, and cross the main bolt AN5 here. Examples: Finsterwalder Perfex, Noth Wing Freedom X.


Figure 3. Some manufacturers prefer to replace the rigid piece, free in rotation, by two pieces (crossbar elbow and downtube plug) which allow rotations in X and Y in the corresponding bolts. Examples: Nort Wing Freedom X, Wills Wing Falcon 4.

Figure 4. Variant with the
crossbar elbow and downtube plug and bracket centered in the middle of the keel tube. Example: Airwave Klassic.

Figure 5. Same as previous but complete bracket around keel and the main bolt below. Example Wills Wing Falcon 2.

Figure 6. Classic assembly of the standar Rogallo crossbar-keel union using an AN5 bolt (not AN4) and and stainless steel or aluminum inverted "U" bracket. The two tubes below, bent in a vertical, fixed to the bracket with a single AN5 bolt in the X-axis.


Figure 7. Special "E" bracket similar to that of figure. Allows for downtubes rigged position in the right angle, and also folded parallel to the keel. Example Wills Wing Duck.

There are other subtypes not described here. For example, the double articulation with brackets. Example Bautek Zephr and Astr.

Each subtype can be described by n parameters (geometry, classes, and materials). In accordance to plans and technical notes that describes the group.

16 Crossbar - leading edge assembly

Figure 1. Classic standard Rogallo and 70's hang gliders. One vertical bolt joining crossbar ans leading edge tubes. Tang cables attached at the beginning and at the end of the bolt. Normally crossbar located below the leading edge, but it can also be the opposite. Example: Wasp Falcon V, La Mouette Atlas.


Figure 2. The majority of modern wings use some kind of plate or adapter between the crossbar and the leading edge tube. A plate with three holes not aligned is used frequently in this assembly. Plate fixed rigidly to the crossbar with two AN4 bolts and a AN4 or AN5 bolt in the tube of the leading edge as the point of articulation. Cable tangs top and bottom, can be fixed at the point of articulation in each side of the plate. This arrangement hides visually and aerodynamically the whole assembly inside the double sail. The function of the plates, is to move away the end of the crossbar, so that it does not interfere with the profile. Examples: Wills Wing Duck, AT.

Figure 3. The ingenious Finsterwalder system will also use a three-hole plate similar to the previous one, but it's cables are attached directly to the tubes with the Finsterwalder tangs and quick bolts. Notice also that the fixing of the crossbar is only on one of the lower side of the crossbar tube, but the end of the crossbar is of double wall, reinforced with an exterior sleeve. Example: Finsterwalder Perfex, Airfex,...


Figure 4. Similar to figure 2 assembly but lower side wire attached to bolt in crossbar. Plate attachement using complete tiube in first bolt and only one side in second bolt. The crossbar tube is beveled at the end. Example: Icaro2000 Laminar 13-14 (kingpost).

Figure 5. It also uses a three-hole plate. But fixed rigidly to the leading edge and articulated to the crossbar. Lower tang fixet to leading edge and upper tang to crossbar. Example: Firebird Laser (a very strong glider).


Figure 6. Instead a three-plate hole, some manufactures uses a bracket riveted in the leading egge, and crossbar articuled in a bolt in the crossbar. Upper and lower cable tangs in the crossbar. Examples: Wills Wing Falcon 2,4 and Alpha.

Figure 7. Instead of a bracket, a bolted channel can be used on the side of the leading edge. With a disposition similar to the previous one. Example: Airborne Fun.

Some elementary parts described here: