8GCBC wrote:I like digging dirt, piling rocks and logs to protect my assets. But, then again, I am part Neanderthal.

One type of portable anchor (AKA "tie down) for land use is the Aussie tent and awning stake. Please see picture of Aussie Tent stakes here: http://corvallis.pro/var/2013.06.26.misc/1/image.jpg. I carry about 10 - 15 for soft to semi hard dirt. Set them in an array that equalizes the load. They are pretty strong...but, no empirical numbers to back my claims at the moment.

There is a good book on climbing anchors by John Long, Falcon Press that gave me a lot of fear and confidence towards earth and rock anchors. Highly recommended.

Lemme see if I am sizing this up more or less sensibly. There have been a lot of good points made, and it seems like a combination of them is most likely what I'll put in my kit-bag: 1. Lots of strong, light, sandbags for sand to rocks; 2. At least two cargo nets; 3. Lots of strong rope (how strong?); 4. Shovel; 5. Hammer/hatchet.

Here's the way "dead men" were done when I was a kid: Dig a trench perpendicular to the direction of the line. Clove hitch on a log, as deep as possible. Cut a narrow trench for the line at about a 45 degree angle to the point on the aircraft to which the tiedown line will be attached (you can add another shallow trench to place under the line where it emerges from its trench if you like, but the whole idea is to make it impossible to pull the dead man out. Fill and firmly tamp the soil in the trenches (about three feet is usually plenty). But I like the bags of rocks or sand better, along with the cargo nets. Lightest weight for the most strength. Rocks, if they are the right shape to prevent slippage, or any kind of junk will do (e.g., old wheels or even good wheels?). You can leave the dead man and its line for the next time or the next pilot. I also like the idea of multiple anchor points. I know airplanes aren't supposed to swing, but I used to use a Bimini rig for my boat, with three smaller anchors instead of one big one. My guess is that three smaller lines on each wing, one parallel with the chord, one more or less forward and one more or less back, would be pretty good, but I haven't done any testing.

What do y'all think?

Twister wrote:3. Lots of strong rope (how strong?);

Here's one approach.....

If you assume the greatest possible force on the plane is equal to the useful load + the drag of the whole plane in parked attitude, then you're talking somewhere in region of 1.5x the useful load. To have a factor of safety over the impulsive forces - the plane 'tugging' on the ropes - you'd want to bump that up to 2x or 3x depending on your confidence in the rope and how firmly you tie down.

Then to size the ropes, you take that value (say 2x useful load for easy maths), and divide it by the number of ropes holding the wings. So if you have 2 ropes, that means each must be rated to lift the useful load. If you double the ropes up (making 4), then each has to strong enough for half the useful load. And so on.

That assumes the tailwheel rope only takes the forces acting on the tail.

So a typical 4 place Cessna, you're taking about each rope having to survive up to 1500lbs - 2000lbs loads (instantaneously) in a gusty 50mph wind scenario, if you only use one rope on each wing. And of course the anchor points experience the same load too.

I think you'd want static ropes, or webbed straps.
Dynamic ropes have stretch, which probably leaves room for things to get slack, or act like springs as the plane rocks about.

And check your sigmets before heading out too.

Usually a line's (AKA "rope's") downfall is chafe. 3 strand Nylon is recommended for short term anchors for many reasons. If you go long term on a mooring or an anchor, install anti chafe methods. Chain really is best if you sit outside for days in rough areas for aircraft. But, full chain is not good for boat/seaplanes in water for moorings or anchors because of shock loading. Aircraft do not shock load to much because a good anchor does not allow much movement.

I do not have any visual examples for an airplane anchored (8GCBC is far away in a hangar, [I hope ]). But, here is a photograph of anti-chafe installed on a sailboat in Hawaii. Chafe is an issue in Hawaii due to the surges experienced in the tiny harbors.

Where the mooring lines go through the chocks, I use heater hose to prevent chafe. It works great! See bow lines with ....

http://corvallis.pro/var/2013.06.16.MAENA/1/image.jpg

8GCBC wrote:Usually a line's (AKA "rope's") downfall is chafe. 3 strand Nylon is recommended for short term anchors for many reasons. If you go long term on a mooring or an anchor, install anti chafe methods. Chain really is best if you sit outside for days in rough areas for aircraft. But, full chain is not good for boat/seaplanes in water for moorings or anchors because of shock loading. Aircraft do not shock load to much because a good anchor does not allow much movement.

I do not have any visual examples for an airplane anchored (8GCBC is far away in a hangar, [I hope ]). But, here is a photograph of anti-chafe installed on a sailboat in Hawaii. Chafe is an issue in Hawaii due to the surges experienced in the tiny harbors.

Where the mooring lines go through the chocks, I use heater hose to prevent chafe. It works great! See bow lines with ....

http://corvallis.pro/var/2013.06.16.MAENA/1/image.jpg

Do NOT, as in NEVER tie an airplane down with chains. A gentleman was killed in Alaska many years ago, having stored his Super Cub on floats parked on the bank all winter, tied with chains. That airplane had been blown by winds, and every gust, the plane would take up the slack in the chains, and hit the solid end.....the strut attach channels at the tops of the struts had fractured over that winter, and right after takeoff, the wing came off. Subsequently, most everyone in Alaska took a close look at their strut attach fittings and a bunch of them were bent or cracked, from being tied down with chains. Including my working Cub, which hadn't been tied down with chains since I worked it. Nevertheless, the mechanics looked at those strut attach fittings, and three of them were significantly bent.

DO NOT tie an airplane down with chains, UNLESS you have a section of rope in the tiedown to provide some shock absorption. Personally, I never tie with chains. I always carry a set of three lengths of good quality climbing rope with me, and tie down with that, even if there are chain tiedowns.

One more time: Do not tie down an airplane with chains.

MTV

Keep chains tight or have "snubber"! Shock loading kills! Good post!

I have heard of windless and samson posts being ripped from steel decks with moderate shock loading! Chain can kill!

Thank you MTV good real world info.

Do you guys always tie down with slack in the rope? I use ratchet straps and dont leave them with slack. The plane rocking and hitting the ends of the straps in the wind makes me wonder whats happening to the struts...

David

A1Skinner wrote:Do you guys always tie down with slack in the rope? I use ratchet straps and dont leave them with slack. The plane rocking and hitting the ends of the straps in the wind makes me wonder whats happening to the struts...

David

Good common sense! Tight is good! But, over time any organic material will stretch i.e. rope. Your method seems like a great way to manage tension, shock loading and dreaded chafe.

As MTV stated above chain shock loading can kill?

A1Skinner wrote:Do you guys always tie down with slack in the rope? I use ratchet straps and dont leave them with slack. The plane rocking and hitting the ends of the straps in the wind makes me wonder whats happening to the struts...

I was taught to always leave an inch or two as wings aren't designed to be pulled down constantly. Here's what the EAA says "The tension of the tiedown ropes should allow for one inch of movement. Too much slack allows the aircraft to jerk against the ropes and can cause structural damage. The jerking motion can also pull out or damage the tiedowns. Tight tiedowns impose inverted flight stresses that many aircraft are not designed to withstand."

During a heavy storm on the Oregon Coast near Cape Foul Weather, my "tie down" lines became loose over night from the rocking and bumping. The airplane knocked out it's chocks and was turned into the wind, luckily. Watching your aircraft or having somebody watching for you is a very good idea. My airplane would have chafe out and broken loose if prolonged exposure was not checked by a caring person.

8GCBC wrote:During a heavy storm on the Oregon Coast near Cape Foul Weather, my "tie down" lines became loose over night from the rocking and bumping.

May as well ask what knots people use. FAA says square knot or bowline. Neither of which I've seen an aviator use ever.

Most often I've seen this, which seems intentionally designed to slip and loosen over time: http://www.flysundance.org/images/fig_2.jpg

I use a simple two half hitch butted against the anchor or a bowline. Caution: bowlines in high tech linear core lines will slip and it has happened hurting people.

Never had my bends "AKA knots" slip using classic 3 strand Nylon.

My experience of failure and/or concern of failure in descending order:

* chafe (due to minor or major surging or shock loading)
* bends or knots loosening/breaking
* rope strength
* weather deterioration and/or corrosion (never use anything but real nylon for lines). Thimbles, shackles and chain need to be certified. AND NEVER use full chain in harsh conditions. Splice a thimble into line and connect with 3 strand Nylon for best longevity and safety.

Always check the weather forecast too. Being in Tornado Alley in June-July may require finding a hangar and forget the outside mooring or staying away.

Note: During the above mentioned storm the lines stretched the tow half hitches never let go.

rw2 wrote:

A1Skinner wrote:Do you guys always tie down with slack in the rope? I use ratchet straps and dont leave them with slack. The plane rocking and hitting the ends of the straps in the wind makes me wonder whats happening to the struts...

I was taught to always leave an inch or two as wings aren't designed to be pulled down constantly. Here's what the EAA says "The tension of the tiedown ropes should allow for one inch of movement. Too much slack allows the aircraft to jerk against the ropes and can cause structural damage. The jerking motion can also pull out or damage the tiedowns. Tight tiedowns impose inverted flight stresses that many aircraft are not designed to withstand."

Makes sense. My only response would be that with big soft bushwheels, 1" turns into a lot more when it starts rocking. With just slight down pressure, it still rocks in the wind, but doesn't slam hard against the loose tie downs.

8GCBC wrote:I use a simple two half hitch butted against the anchor or a bowline. Caution: bowlines in high tech linear core lines will slip and it has happened hurting people.

Yup. Two half hitches for me also. Never could figure out how to tie a bowline and leave the amount of slack I wanted.

8GCBC wrote:My experience of failure and/or concern of failure in descending order:

* chafe (due to minor or major surging or shock loading)
* bends or knots loosening/breaking
* rope strength
* weather deterioration and/or corrosion (never use anything but real nylon for lines). Thimbles, shackles and chain need to be certified. AND NEVER use full chain in harsh conditions. Splice a thimble into line and connect with 3 strand Nylon for best longevity and safety.

Yup, I solve most of the above by carrying my own rope and replacing it when needed. I never trust airport rope.

8GCBC wrote:Note: During the above mentioned storm the lines stretched the tow half hitches never let go.

But they were the ones the loosened. Interesting.

I wish I could justify a hanger, but $5,000 a year is a tough sell when the insurance company rated the value of being in a hanger at a couple hundred dollars.

rw2 wrote:

8GCBC wrote:During a heavy storm on the Oregon Coast near Cape Foul Weather, my "tie down" lines became loose over night from the rocking and bumping.

May as well ask what knots people use. FAA says square knot or bowline. Neither of which I've seen an aviator use ever.

Most often I've seen this, which seems intentionally designed to slip and loosen over time: http://www.flysundance.org/images/fig_2.jpg

I've used that knot, tied twice, my whole wide life. Never a problem even here in windy city. I use a bowline at the ground end. If the weather forecast calls for over 25 I go out and add ratchet straps. I prefer yacht braid dacron. Nylon moves and stretches too much. When I had the boat (36 tonnes, 54' overall) I found that nylon lasted about half as long as dacron yacht braid.

EB

I'm having a "senior moment" and can't think of the term for the heavy-duty rubber "shock cords" that I used to use on my mooring lines 'way back when I had a boat. If I recall correctly, these devices were attached to the mooring lines mid-way, with a bit of slack in the line. Maybe our yachtsman friends can enlighten us on this. This helps keep the strain off the boat/plane under mild wind/wave conditions, but helps to at least keep the wreckage in place in most gale+winds.

6. Spoilers. (Best?)

Rw2

Tie down lines loosened during the storm not parted. The lines stretched or were left with too little tension during the night. The knots were not an issue. The issue was my ignorance of the slack lines that I tied from what I can remember.

Emory Bored wrote:

rw2 wrote:

8GCBC wrote:During a heavy storm on the Oregon Coast near Cape Foul Weather, my "tie down" lines became loose over night from the rocking and bumping.

May as well ask what knots people use. FAA says square knot or bowline. Neither of which I've seen an aviator use ever.

Most often I've seen this, which seems intentionally designed to slip and loosen over time: http://www.flysundance.org/images/fig_2.jpg

I've used that knot, tied twice, my whole wide life. Never a problem even here in windy city. I use a bowline at the ground end. If the weather forecast calls for over 25 I go out and add ratchet straps. I prefer yacht braid dacron. Nylon moves and stretches too much. When I had the boat (36 tonnes, 54' overall) I found that nylon lasted about half as long as dacron yacht braid.

EB

That knot IS two half hitches. I back it with another half hitch to lock it. Yes, it may slip a LITTLE bit.....BUT it also allows you to reTIGHTEN it during a storm, by simply sliding it tighter. IT then locks again. In the midst of a big storm, you sure don't want to have to untie your airplane to tighten the lines, do you? And, you ARE out there at the airport, tending the lines and keeping an eye on it DURING that big storm, right?? I kept three airplanes outside for several years in Kodiak, and spent quite a few nights out there with the planes, sitting in the car, watching......And, there were a couple times the planes really needed tending. I saved a guy's Super Cub wing from collapsing because I was there. While I was occupied with that, a brand new 206 on floats blew over into a rock wall and destroyed itself......nobody there to keep an eye on it.

That's the best tiedowns.....the owner being there, tending the plane. Get inside and fly it on the lines if necessary-I've done that behind a boat one night.....

MTV

Okay just a thought or idea here what about using the bungee cords off of your cub Taylorcraft etc. and using them for the shock load seems like they would be more than Adequate for the shock load on your plane just wondering If anyone has ever used it doesn't work or bad idea etc.?