Securing Your Cessna
As you may do now, I simply tied a rope to the tie down ring provided by Cessna. Over the years, I heard stories of the rings breaking and the plane departing the area.
I always placed the hold down so the rope would be at a 45 degree angle when tied to the ring at the top of the strut.
Having learned a little about physics, if the rope isn't straight down from the ring to the hold down, the forces on the rope are increased for the same force produced by the wind and varies with the angle. The increase in pull for the same applied force due to wind is sizeable and increases as the angle gets bigger.
I kept my eyes and ears open over the years and formed my own opinion on how to properly tie my aircraft to Mother Earth.
1) Wrap the rope around the strut. Add a couple of loops and run one loop through the tie down ring just to keep the rope from slipping down the strut. It's the strut that is now taking the main force, not the ring. The strut is built for this, the tie down ring isn't.
2) Place the hold down, the part you drive into the earth, directly under the tie down ring. As can be seen mine isn't but close enough.
3) Make the rope tight. If there's slack, that adds more stress to the rope and tie down. A short term duration of a tight rope isn't the problem. A tight rope over a long period of time will do damage to the plane with the change of the Seasons.
A loose rope allows the plane to move with the wind so the rope now has to stop a moving plane instead of simply holding a stationary one. Once the plane starts to move, it's weight is increased by it's velocity. The rope will have to hold a higher weight if the plane moves as opposed to being stationary. And the weight is applied with a steep rising front as the rope gets taunt so a weak rope may break. The rope may survive a steady pull, however.
4) As with the wings, put the hold down directly under the tail tie ring. With a tail wheel aircraft and you have the BAS handles, use them to tie down your craft.
If you do have a taildragger but not the BAS handles, you are on your own.
5) I use a modified taut line hitch at the hold down end of the rope. This permits an adjustment. Over time knots may loosen and this provides an easy means to make the required change. The rope has to be a coarse rope, not the smooth, silky type. I do not use a natural rope material because of the change that occurs when it gets wet.
I use Fly Ties for the hold downs. For the rear, I tie the rope to the hold down then wrap the handle on the far side then come under the fuselage and wrap the handle nearest me. I then run the rope through the hold down again and create the taut line hitch to allow adjustment.
Visit http://www.iwillknot.com/taut_line/ for a tutorial on tying this knot. Remember to add two extra loops during step 2 and an extra half hitch during step 3.