With spring MLG and 31" tires it is impossible to keep chains from shock loading my bouncy Scout. To many variables to keep them perfectly tight. Nothing is completely static on aircraft that is why chains may become loose.

Don't get me wrong, I don't advocate or use chains on small aircraft, unless you have a tensioning device. Ours in the Navy had a turnbuckle like mechanism built in to one end. If you have a tensioning device, i.e. turnbuckle you carry, then they are as solid as you can get.

8GCBC wrote:With spring MLG and 31" tires it is impossible to keep chains from shock loading my bouncy Scout. To many variables to keep them perfectly tight. Nothing is completely static on aircraft that is why chains may become loose.

This is why I like ratchet straps. They have a ratchet to make sure the slack is out. Most aircraft tied down with ropes have slack and are banging away in the wind, as its pretty hard to get all the slack out with a knot.

Easy there.... no need to over-tighten for a small aircraft (jet fighters need not apply!)
Inverted flight loading on the wings of a parked aircraft is a bad thing. The ratchet alone could be strong enough to do permanent damage. Strong winds would only make the inverted load worse by adding to that force.

The AC recommends "1 inch of slack" when using a static rope with no stretchiness.

I make my own and sell tie downs. I go to Lowes or Home depot and go to concrete stake area - pick steel stakes about 1-1 1/2 inch wide about 18 inches long, get some screw together caribeners about 2-3 inch long , and about 10 ft. Long 5\8th inch poly rope. Get out your trusty drill press and drill hole near top to put your caribener thru . Drive these stakes into ground at about 30-40 degree angle - outboard about 6-8 ft. Out board from tie down ring , drive stake into ground about 2/3 of length . Attach rope and tighten . Strong enough to pull bumper off truck when seated. When you get ready to leave knock stake from side to side and remove. I use a 5 lbs sledge to drive in. Sets of 3 from me about 40 bucks or make your own for about 2/3 of that.

Battson wrote:Easy there.... no need to over-tighten for a small aircraft (jet fighters need not apply!)
Inverted flight loading on the wings of a parked aircraft is a bad thing. The ratchet alone could be strong enough to do permanent damage. Strong winds would only make the inverted load worse by adding to that force.

The AC recommends "1 inch of slack" when using a static rope with no stretchiness.

That's exactly correct. You CAN change the general shape of your flying machine with ratcheting straps. That is not a good thing. Also, those straps themselves don't "give" much either....and you can induce the same sort of issues that chains can.

A little slack WITH a good stout rope is no big deal because the rope (actually a "line" once it's used in an application) prvides some stretch, thus gradually taking the force, and protecting structures.

MTV

After using ropes (AKA "lines" on a boat, [except the "bell rope"]) on the ocean for forty years my favorite line is still 3 strand nylon. It has reasonable trade offs.

Pros:

* dynamic stretch (returns to same length under light/moderate loads)
* easy to splice
* coils easily
* chafe resistant
* over loading is visually detected early
* "bends" and knots do not slip
* UV damage is very slow in the tropics. I have halyards that are (30) years old that will not break.

Cons,
* Does not float
* loses about 10-15% when wet (hygroscopic) and gets heavy
* moderate chemical resistance ie gas, oil, etc.

A tale of two boats in Hawaii (Kona, Ala Wai)...

Mooring/anchoring a 25,000 LBS 37'sailboat (steel):
I do have all chain rode for my day anchore 3/8" BBB. But, if the seas pick up I go for 3/4 inche nylon. Always use a snubber just in case of an unforeseen shock load on the chain.

Mooring/anchoring an 8,000 (30') LBS powerboat (aluminum) I use 1/4 standard ISO chain only because the alumium is so light. Never used my backup 3/4 inch hurricane rode yet!

There are speciality ropes that do tasks very well. But, if I had one type of rope for everything it would be 3 strand nylon. It is kind of like an acetylene torch, do NOT leave home without it.

Edit: I use a 4LBS Bruce and 1/4" nylon when Scout on floats. But, little experience to mention. Just calm lakes for now.

I think we are applying a generalization here that does not apply to all aircraft. Lets take most Cessna aircraft. The tie down is on the lift strut. If you manage to deform that triangle with a ratchet strap, then that's some ratchet strap you have there. Conversely, tying down the tail on a taildragger is really tough to keep it so it is firm to the ground, both vertically and laterally. Geometry works against you there. Apply the tie down pattern that works best for your aircraft, it may not apply to all aircraft. Like on carrier aircraft, can't use the wings, they fold. Another item, I put orange survey tape on my stakes, why, because I am a klutz, I want to keep from tripping on them. I also cut some plumbing insulator and a child's swimming noodle to protect my head from the end of the flaps. I have lost count how many times I have hit my head on them.

Battson wrote:Easy there.... no need to over-tighten for a small aircraft (jet fighters need not apply!)
Inverted flight loading on the wings of a parked aircraft is a bad thing. The ratchet alone could be strong enough to do permanent damage. Strong winds would only make the inverted load worse by adding to that force.

The AC recommends "1 inch of slack" when using a static rope with no stretchiness.

Im nit saying suck them down as hard as you can, just snug so there is no slack. I hardly think that snugging up a ratchet strap puts more then -1G on an aircraft.
If using a rope with no slack then you mught as well be using a chain, as it will still hit pretty hard with 1" of slack, especially if that 1" turns into 3" because you are on bushwheels.

A1Skinner wrote:Im not saying suck them down as hard as you can, just snug so there is no slack. I hardly think that snugging up a ratchet strap puts more then -1G on an aircraft.
If using a rope with no slack then you might as well be using a chain, as it will still hit pretty hard with 1" of slack, especially if that 1" turns into 3" because you are on bushwheels.

Yes I agree - no hard having it snug. I just wanted to add that thought in case someone else took the wrong message from the mention of using ratchets. No offence intended.

Semi-snug ropes are quite different to chains. Chains stop the motion almost instantly. That very fast rate of change of momentum requires an extremely high impulsive force be applied to the aircraft. This impulsive force effectively acts like a large instantaneous (and negative) g-force. A small amount of stretch in the rope has a huge cushioning factor, compared to chains with zero give, because it gives the rocking aircraft crucial time, allowing to change momentum more slowly by comparison. The net result is, the applied impulsive force is much lower even with a tiny amount of springiness in the rope.
If the change in momentum takes 0.05s with chains and 0.5seconds with a rope, the applied -g force is only 10% with the rope compared to chains.

One of the problems often overlooked in testing is the fact that the pressure on the ground tie down is not constant, gradual and progressively increasing as presented in the trials but more of an inconsistent tugging, pushing and pulling effect relentlessly and slowly pulling the tie down out of the ground to the point of failure. I agree that all are tested against each other in the same fashion, but it doesn't represent the normal use of the tie downs.

My point, try to pull a fence post out of the ground straight up...now move it from side to side and back and forth, much easier...

I spent many hours over the years under the wing or in the seat watching and wondering if that tie down was going to let go before the wind died down and the weather cleared and that is my observation.

I've added swimming noodles to my camping supplies, too. I seem to duck most of the time in the hangar (most, not all), but I've banged into trailing edges a few too many times while camped. At Marble a couple of years ago, I whacked into the strut and about knocked myself silly, so a noodle goes on the back side of the left strut, too. They're a little thicker than pipe insulation, and since they're pink, hopefully I will see them and not try to take off with them still on!

Incidentally, The Claw instructions say to have the pull vertical, not angled, and that seems to work pretty well. I snug up my straps as tight as I can (they're not ratcheting), and I have yet to pull The Claw loose in anything--haven't been in pure sand, yet, but everything else has held. I agree with angling if you use something like an angle-iron or rebar stake, which you'd angle against the line so that it pulls at roughly a 60 degree angle, much like a tent stake.

Cary

So I'm in Durango this week looking for a vacation place. Unfortunately I couldn't find any hangar space at Animas Airpark so have had to keep the 185 outside and tied down. Animas has cables running across the ground to tie to, not something I like. I did manage to get an end spot this morning, after a brief flight up the valley to bag a strip, so was able to secure one wing to an eyebolt set in the ground. The other wing was secured to the cable. The lineman wanted to chain the plane but that's just a terrible idea if you like your plane - and I like mine so I used rope that I carry. I was unable to tie down the tail as there is nothing to anchor it to, besides, it was a nice sunny calm morning.

While we were looking at places in Glacier Club a thunderstorm hit, winds of 30 plus. Naturally I headed to Animas to see how the Wagon was holding out. When I arrived I spotted a truck parked behind the Wagon and thought how nice it was that someone thought to shield my Wagon's untied tail. Upon closer inspection I saw that they also had tied the tail to the trailer hitch on the truck. Wow, very thoughtful. I assume it's the FBO Gregg's Flying Service but don't yet know for sure. I will find out and give them a big thanks.