Tie-Downs and Straps

Any suggestions on tie-down and strap choices would be greatly appreciated.
I am attending my first camping fly in at Madden's resort in Minnesota and will be camping under the wing a bunch this summer. Not sure if the claw from Sporty's is a good idea or if I should buy something else for the times there aren't tie-downs available. Also some proper procedure on tying down the tail of my PA-12.

The Claw has worked great as an anchor point for me for years, but does not work the best in some sandier types of soil.

As for the Lines themselves, I absolutely love the knotless tie downs I got from this guy https://backcountrypilot.org/forum/125-tie-down-lines-and-hammer-s-photo-dump-17878.

That line is called Spectra or dyneema. It's used in sailing and it's awesome. No stretch.

http://www.novabraid.com/rope-material/spectra-fiber-rope/

https://m.youtube.com/watch?v=d0B6tYTVHVM

Great stuff, I've ordered and received the clay and the lines. Anyone on input for tying down the tail should the winds necessitate?

Sent from my XT1650 using SuperCub.Org mobile app

I've had good luck with the Claw for 10 years or so but for New Holstein's sandy/silt and storms I use augers and I don't mean doggie screws.

Not sure about using being a good choice or not, depending upon your opinion of the effect of shock loads being transmitted uninterrupted to the anchors. Spectra it's good stuff (you get to step down usually two size) and works great for light air spinnaker and headsail sheets but in a blow I did some significant hardware damage with it back in my sailing the days. For tie downs I use low-stretch Gold Braid dock lines from West.

I tie the tail a little bit loose so you get some movement but so that it won't raise high and risk a tip over.

I would strongly recommend using line that does strech for tiring down an aircraft. It allows shock from a gust to be absorbed by the line instead of transferring all the shock to the aircraft structure. Use good quality (not cheap) nylon line, not nylon and mixed fibers also learn a few basic knots. A bowline is essential and while many people use a rolling hitch which supposedly locks on a line, they can slip. I tie my knots at the tie down so they can't slip. If the line is long, I may tie my bowline at the wing and half hitches at the ground so the long unused line is on the ground and won't beat on the plane in a strong wind.

Cubs have had failures of the lift strut attach fittings that connect the lift struts to the spars. Both fatal and non fatal. Those who use chain, or even ratchet straps are asking for trouble. One such failure on the Alaska Penninsula in the late eighties or early nineties prompted ATLEE to make two STC's, an insert that went inside the lift strut attach fitting on a cub and a tie down that went arround the spar outboard of the lift strut attach fitting thereby not involving the strut attach fitting in the tie down. I have a seat belt strap arround the spar instead of the Dodge tie down on one of my Cubs. That strut attach fitting is made to take a load in tension but when used as a tiedown the load is no longer in the direction which it was designed for and in the direction where the strength is. There is a service bulliten concerning the inspection of the lift strut attach fitting.

i do carry a realitively long piece of small diameter winch line. Sounds like it is similiar to this specter. I use this to tie to a tie down like a tree or something that is a distance away, and then tie my tiedown line to it. It is light, strong and has no strech and should only be used as a tie down line as a very last resort.

Remember the wings are designed to lift more than the gross weight of the aircraft. You may want to select the line strengths accordingly

reliableflyer said:

I would strongly recommend using line that does strech for tiring down an aircraft. It allows shock from a gust to be absorbed by the line instead of transferring all the shock to the aircraft structure. Use good quality (not cheap) nylon line, not nylon and mixed fibers also learn a few basic knots. A bowline is essential and while many people use a rolling hitch which supposedly locks on a line, they can slip. I tie my knots at the tie down so they can't slip. If the line is long, I may tie my bowline at the wing and half hitches at the ground so the long unused line is on the ground and won't beat on the plane in a strong wind.

Cubs have had failures of the lift strut attach fittings that connect the lift struts to the spars. Both fatal and non fatal. Those who use chain, or even ratchet straps are asking for trouble. One such failure on the Alaska Penninsula in the late eighties or early nineties prompted ATLEE to make two STC's, an insert that went inside the lift strut attach fitting on a cub and a tie down that went arround the spar outboard of the lift strut attach fitting thereby not involving the strut attach fitting in the tie down. I have a seat belt strap arround the spar instead of the Dodge tie down on one of my Cubs. That strut attach fitting is made to take a load in tension but when used as a tiedown the load is no longer in the direction which it was designed for and in the direction where the strength is. There is a service bulliten concerning the inspection of the lift strut attach fitting.

i do carry a realitively long piece of small diameter winch line. Sounds like it is similiar to this specter. I use this to tie to a tie down like a tree or something that is a distance away, and then tie my tiedown line to it. It is light, strong and has no strech and should only be used as a tie down line as a very last resort.

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How do you have time to post here, aren't you to busy looking after Glenn

He just left this morning and while he was here he was explaining to me how this site worked He pulled this post up.

It was a pleasure to have him here. I think he may want to come back.

reliableflyer said:

He just left this morning and while he was here he was explaining to me how this site worked He pulled this post up.

It was a pleasure to have him here. I think he may want to come back.

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He's been texting me pictures, beautiful place up there

It certainly is a beautiful place. He and Bev enjoyed it. We caught a 40 pound halibut, ate some fresh salmon, they went kayaking and he flew my cub for a bit. In a week moment he admitted that mine got off shorter than his. It was the festive week and lots going on. I think he wants to come back.

Stretch in tie down rope is a bad thing. Watch your plane bounce up and down as the rope stretches compared to sitting firmly in place with static rope. Sitting still is better.

I am concerned about the carabiners that some people use, as illustrated in your photo at the top of this thread. They need to be rated to a very high strength, and I am not sure any associated even with mountain climbing will be strong enough.

Randy

stewartb said:

Stretch in tie down rope is a bad thing. Watch your plane bounce up and down as the rope stretches compared to sitting firmly in place with static rope. Sitting still is better.

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I need to take issue with your statement about strech vs no strech in tie down line. They build cars now that slowly crush during a collision to prevent sudden stops and absorb the shock over a longer period of time.

. The risk comes when their are gusts which cause sudden jerks on the planes structure. What's more, in a tied down situation the force of the wing moving up in a gust is concentrated in one location on that structure. Many airports provide chain. In strong gusts as the wing is pulled or forced up, it jerks hard when it hits the end of the chain. I had my wife pull one of my ratty old cars with a chain once to get it started. I said get it up to twenty or so. She did right then and streched the bumper out two feet and bent the frame rails of my studebaker. The same happens with non stretchable rope. If stretchable rope is used the force is partially absorbed in stretching the rope and less force is imparted to the wing structure. As I recollect the boom vang on a sail boat is made to absorb some of the shock on the structure when the boat comes hard about? They used to use springs on the chain restraints on screen doors so that when we ran out and the door opened fast the spring would absorb some shock to prevent pulling the screw eye out.

I should add for clarity, I do not leave slack in the tie down lines. They are snug not stretched and tied with appropriate knots usually a bow line at the ground tie down and half hitches right against the tie down ring. The stretchable rope like a high quality nylon line not mixed fibers acts as a spring when the gust starts to jerk the plane since the lines are snug the resistance is ther a little bit at a time throughout the total rise of the plane. Up you tiedown lines at a boat store, not Walmart. Buy lines that are ment to take shock.

As I recollect it was in the early 70's in Anchorage, Judge Kalimeredies was killed when he lost the wing of a super cub. My recollection on that one is fuzzy. In the late 80's or early 90's a State of Alaska Wildlife super cub was tied down on the Sandy river on the south end of the Alaska Penninsula. Two of the guys I worked with stayed in their tent for three days while it blew. At the end of the blow the pilot, one of the bettter cub pilots I know and one of my mentors for about 40 years now inspected the plane. He removed the inspection cover aft of the spar at the wing attach fitting. Because he saw that the compression member had been pulled down against the fabric somewhat more than usual. It requires close examination. He found the lift strut attach fitting on the aft side of the front spar was slightly bowed but no kinks or cracks. Since the fitting portion forward of the spar is not visible since it is under the leading edge he took his knife and cut a hole in the fabric and leading edge aluminum. . He then examined the fitting forward of the spar and found a slight bow but no cracks or kinks. The took off and at about 100 feet the wing separated at that fitting. It folded up and the rear fitting failed. The wing went up still connected at the wing root, the asicraft rolled and they went into the Sandy river inverted. Fortunately the survived the wreck, drowning and the hypothermia that followed. That incident was was well observed and understood. ATLEE promptly designed a lift strut fitting support piece now sold by F A Dodge and by Univair. The distance between the strut bolt in the fitting at the tie down and the bolt that gots through the spar is anout 6 1/2 inches. It is made to take force in tension, a straight line along the total fitting into the strut and the the strut forks. When we tie to the tie down ring or the strut up by the wing and the wind gusts force the wing up and the wing tries to fly the tie don line places a strain on thatstrut attach fitting at an angle of perhaps 45 degrees from the angle that it is designed to take the load. Furthermore the force is the end of a 6 1/2 inch lever. Inspection of the is fitting is discussed in a service bulliten where their is a small hole cut in the leading edge and patched with a bullet hole patch after the inspection. I have even seen the welds on a factory tie down ring fail. I should also mention that ATLEE also made. Tie down STC for a cub which is a metal strap that goes around the spar outboard from the lift strut attach fitting and does not involve that fitting in the tie down. On one of my Cubs I have taken a seat belt strap and put it arround the spar so the tie down force is applied perpendicular to the spar outboard of the lift strut attach fitting.

I suppose if a plane net is tied down where it is not subject to severe winds it probably doesn't matter. My experience and education has come from many years flying in Alaska and I have learned that line that will absorb some shock as the winds jerk a plane is easier on the aircraft than line which transmits all the shock to the airframe.

I watched my 180 ride out 117mph winds in 2003 tied with static climbing ropes. The only motion it had was from tire squish and there wasn't much of that since I had it tied tight. I've watched the same plane dance and jump around on dynamic climbing ropes in less than half the wind. I was worried about it tucking the gear so I added static roles to calm it down. My choice is from experience as well. To each their own.

reliableflyer said:

...If stretchable rope is used the force is partially absorbed in stretching the rope and less force is imparted to the wing structure. ....

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he's gonna be rich... sounds like over unity talk.....

So if you want no stretch would you use chains instead of ropes for your tie downs?? Just throwing fuel on the fire.
DENNY

WindOnHisNose said:

I am concerned about the carabiners that some people use, as illustrated in your photo at the top of this thread. They need to be rated to a very high strength, and I am not sure any associated even with mountain climbing will be strong enough.

Randy

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Good point. Carabiners should be the screw locking type, of high quality. I forget exactly, but mine are rated for 6000 pounds or so, which is about the tensile strength of typical climbing line, particularly after the line is looped through a ring. Carabiners only need to be stronger than the wing tie down rings. We once had a big blow in Boulder, CO, damaging a lot of planes. Some went airborne. Typically, it was the tie down rings that broke.

The problem with chains is slack. The plane moves a couple of inches and hits a dead stop when the slack is taken up. When I tie my plane there's no slack in the ropes and when the winds blow there's no movement. That's the point of tying it down. Dynamic ropes stretch about 25%. That means a 100" rope tied tight may be 125" long when stretched, so one side of my plane may be up to 25" off the ground in a hard gust? Not my airplane. Been there, done that, retired that rope. My current static rope is rated at about 5% stretch but I haven't seen light under the tires even in a strong wind.

Differing opinions on using rope with or without stretch is a good discussion, but something we should all agree on is don't expect cheap rope to work. Some of the line I've seen used to tie down aircraft was down right scary, especially if in the vicinity of my plane. Take some time to look at the static load and strength of line before you buy it, and think about what your going to be tying down.

I also think there's a lot to be said about spoiler covers if you're wanting to keep your plane on the ground.

Jim

Yep, spoilers work good, but when the winds are greater than 45-50 my covers come off.

Anyone have any good pireps for vented spoiler covers? I leave town for weeks at a time in winter and still use a trick 55-PA18 taught me. I use my solid covers and then add my mesh spoiler covers over those. It's a bit of a pain for everyday use but for weeks way it's worked great. Covers that behave and perfectly clean wings. My new Cub will see the same treatment but I would like some vented covers for everyday use. I expect to employ another idea that AKPA18 offered years back. Add an earth anchor under the cabane to allow the plane to be tied down and still be able to rotate it nose to the wind. Good idea!

stewartb said:

Add an earth anchor under the cabane to allow the plane to be tied down and still be able to rotate it nose to the wind. Good idea!

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I got caught in a big blow a couple of years ago and used my tail tie-down under the cabane. The wings were tied down and tail was free to move some.

It blew harder later and I was sitting in the front seat dosing off. I woke up when the left wing anchor broke loose and the right wing touched the gravel. Instinctive left stick saved the day (night actually) along with a lull in the wind.

twl said:

Any suggestions on tie-down and strap choices would be greatly appreciated.
I am attending my first camping fly in at Madden's resort in Minnesota and will be camping under the wing a bunch this summer. Not sure if the claw from Sporty's is a good idea or if I should buy something else for the times there aren't tie-downs available. Also some proper procedure on tying down the tail of my PA-12.

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I'e had good success with the Claw in all types of soil, including New Holstein although I don't recall any high winds there.

I like to add snaps to attach wing covers(spoiler type) to bottom of leading edge. Keeps them from rotating back in wind storm and becoming useless.

With regard to stretch vs. no stretch (assuming a solid anchor), I'm in Stewart's camp on this one. I use ratchet straps and draw them down slightly snug. No slack equals no jerk/shock.

psssst... as far as stretch goes...

theres only so much stretch till no more stretch, and then you are just same solid....

until it breaks in an extreme...

No matter how tight I tie down my Cub, I've seen it jump around in big winds due to the flex of the 31" Bushwheels. The tires trump the stretch or no stretch of the ropes/straps. Maybe the rope stretchiness would make more of a difference on planes with little tires.

Same here, but at least there is no jerk or jolt. Are you coming out to Kirk's fly-in at Booneville in Aug?

PerryB said:

Are you coming out to Kirk's fly-in at Booneville in Aug?

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planning to. And you? See you there!

I am also in the camp tie it tight, and use rope that doesn't stretch,when I use rope. I say when, because even though I am quite handy with knots and lines, after trying a set of tie downs like the ones in the second post, it's almost all I use to tie down my planes. It's worth mentioning that there aren't many good ways to 'tie' amsteel, or any of the 'super lines'.

Three of my airplanes survived a microburst that made a pretzel out of my neighbors cub, and blew a section of my wheel line a mile away. I get them down tight enough that even on big wheels, they don't move. The big tires provide cushion down, I don't see why anyone couldn't get a plane to quit moving up regardless of tire selection.

As to use of carabiners, it is wise to select wisely. Having said that, the ones in the second post show a rating of 20KN on the spine or something on the order of 4500 pounds. I use a bit beefier ones, but I suspect that the tiny bolt that holds the tie down ring (mounted in shear) would fail before holding 4500#s, and have no doubt that any rope would be cut in two at the tie down at that pressure (I wrap the strut on a Cessna for that reason and others). Like most, I was suspicious of those wonder lines prior to putting them to the test. I'm sure I warmed up to them about like an old timer to a GPS. New technology always seems to get its fair share of skepticism. Now I flat love them. The speed at which they can be deployed is astonishing, and has come in handy a couple times already when the wind was stiff enough to execute an almost vertical landing into the tie down.

Take care, Rob