The Tripod
The "A" Frame
Probably the strongest basic structure known.
Under Lashings are given two or three examples of how to make a tripod so we'll move on to other structures.
The "A" Frame
Start with two spars or poles, approximately 4 meters long, laid side by side (in the 'closed' position) and apply a sheer lashing about 20" (500 mm) from the top. Open the 'sheer legs' until the butts are no further apart than one third of the height between the lashing and ground level. Square lash a third spar across the legs about 12" (300 mm) from the butts.
To use the 'A' frame in an upright position, four guy lines, two from the tip of each spar, must be anchored fore and aft. If a rope is to be run across the crutch of the frame, a saddle of canvas or similar material must be used to protect the sheer lashing from damage.
The Trestle
Before you can make it you will need to collect all your gear together. Choose your equipment with care, taking into consideration its size and the load it will have to carry. You will need six spars and nine lashing ropes.
Take the two stoutest spars for the legs and make the thicker ends the butts. Select the next strongest spar for the transom as it would have to take most of the weight if you were constructing a bridge. Mark the position of the transom and ledger so that when they are lashed to the legs, the legs slope inwards approximately 2" for every foot of their length. i.e., a six foot spar would slope in 12".
The spars can now be lashed together using square lashings. Add diagonal braces exactly as shown in the sketch, one end of one brace above the leg and the rest below the legs. fasten them to the legs with square lashings and finally the diagonal braces are lashed together with a diagonal lashing.
There are many other types of structures used in pioneering but they all use either one or more of these three basic shapes in their construction
Now get out there and have some fun.
Remember; If its not fun----It's not Scouting.
See Also:
Pioneering Model Building
Traditional
Training Handbook
©2003 Baden-Powell Scouts Association
