Tie Downs - How to be Taut and Terrific

[BigPete]

OK - Its true confession time.

 

I keep my 'plane in a hanger. I've never tied it down before.

 

I have a set of those "Screwit" whizzos, but what rope do I use?

 

What knots do I use?

 

OK guys and girls I'm listening.

 

regards

 

PS like everything else in Rec Aviation it has to be cheap and effective (the poor mans answer)

 

 

[old man emu]

I'd suggest 12mm (1/2 inch) nylon twisted rope. Strong enough for a Jab; won't shrink if wet; will dry out quickly if it does, and is as cheap as chips.

 

As for knots. Pass a looped of of the rope thru the tie-down ring, then come back around the line from your peg to the ring with a couple of half hitches.

 

Don't have the ropes tight, or you'll damage your wing. Let the rope sag a bit. You're not trying to hold down an untamed brumby. What's the strongest wind you expect to experience while the plane is tied down? How much lift do you get at that airspeed?

 

The biggest danger is the tie-down pegs pulling out of the ground. Test them by screwing them in as far as possible, and then trying to pull them loose. Do that test before you fly away from home. Tie-downs should be put in at an angle so that the head is pointing away from the tie-down ring, ie towards the wing tip and away from the tail for the rear tie-down.

 

Hope that helps.

 

Old Man Emu

 

 

[Guest pelorus32]

Just a note on rope. In general Nylon is the stretchiest of rope - up to 20% is not unusual, particularly if overstressed. It also loses strength when wet and there is some suggestion that it shrinks somewhat when wet.

 

Dacron stretches less and loses less strength when wet.

 

Spectra doesn't stretch much at all but is subject to "creep" - it will "permanently" stretch if left under tension.

 

Knots reduce the strength of all rope by ~50%.

 

Polypropolene is weak for its size, very light and very prone to UV degradation.

 

3 strand rope stretches more than the same size braided rope.

 

Sorry my sailing background popping out.

 

Regards

 

Mike

 

 

[hihosland]

Old man Emu did say

 

and most of us would agree

 

'''''''''Tie-downs should be put in at an angle so that the head is pointing away from the tie-down ring, ie towards the wing tip and away from the tail for the rear tie-down.

 

""""""""""

 

the manufacturer of the 'screw it' anchors advise to insert them so that the pull is directly along the axis of the shaft of the screwit.

 

Davidh

 

Hope that helps.

 

 

[Ultralights]

hmmm just thinking, im not sure my Vampire has tie down points?? have to have a look tomorrow, or come to think of it, im not sure if i have tie downs either.... more shopping.

 

 

[old man emu]

I have no doubt that what pelorus 32 posted in relation to stretch performance of various rope materials is correct, and should be taken into account in situations where there are big loads on ropes, as in sailing, lifting or towing. However, those loads are not expected to apply in the tie-down situation.

 

As I said, consider the expected windstrength when tieing down, and the wind direction. We had a Cessna 172 flipped by 100KpH gusts at Camden earlier in the month. The plane was tied down OK, but had its tail into the wind. It was the only aircraft damaged in that storm. An aricraft tied down beside it, with nose to wind, didn't move.

 

Old Man Emu

 

 

[Guest bazdavis]

The best I've seen are shortened large tent guy ropes with sliding rope adjusters and springs at the anchor points. There quick and easy to fit and tension and the springs have enough movement to prevent over loading the tie down points in gusty conditions. plus all the end loops are nicely spliced for you.