Home-made Tiedowns

[radfordc]

Bob Mika tested several different types of tie downs to see which held the best. The best was a spiral dog stake. They are difficult to get into really hard ground without breaking. Years ago I bought a set of spiral stakes made from titanium...you can screw then into asphalt if you want to.

Many airplanes were flipped and/or destroyed. It seems that nearly all tie-down sysytem types failed but the dog tie downs were the first to go. It makes sense. Would the desingers really engineer a multi-thousand pound pull force capability for dog security...?

What happen at the lakeland tornado? Did planes flip over due to the dog ties?

Norm

[radfordc]

Here is Bob's test info:

Today I tested my heavy duty dog anchors. I got a big surprise.

Here are photos and results:

http://www.flickr.com/photos/53052604@N03/page5/
http://www.flickr.com/photos/53052604@N03/page6/

The first test was the Sport Aviation tie down. The SA anchor pulled out at 120 lbs when pulled at 90 degrees and 90
lbs when pulled at 45 degrees.

The the dog anchors were tested. The bottom line was using my 50 lb luggage scale I could not move or pull
out a single anchor. At a 90 degree pull I applied at least 277 lbs to the
anchor. The only thing it did was to rotate slightly to align the rope and
anchor to the force vector.

I then did a 45 degree pull and applied at least 275 lbs. Same result. No
movement, except a little rotation to align to the force vector.

With these results I am going to use two heavy duty dog anchors on each
wing placed about 6" apart. I will use a single anchor on the tail.

Remember, these numbers will be affected by soil type and moisture but the
relative

Bob (number crunchier) Mika

[structurespilot]

Thanks for the run of tests you performed Bob. Your tests substantiate my thoughts on the dog ties. I was wondering why the tog ties had broken during the storm. I'm thinking that the people were using dollar store quality dog ties. The dog ties would have way more tension strength provided the metal quality wasn't in question. The strait pins would only have the tension strength provided by the friction of the soil. They both should have similar results in shear strength, provided the metal was of equal diameter.

Not to discount the efforts of people who made the strait rod style tie down, I think they will work just fine. But for me the dog tie style makes sense.

Thanks again for sharing your results,

Norm

[N111YX]

I guess mine were made from Chinese steel...!

[fastj22]

My source for titanium stakes is Chinese. Hence the 1000 minimum order and relatively cheap unit price.

However, I was at the local hardware store and they sold 6061 3/8 aluminum rod for $1.5 a foot. I would think 3 stakes (9 total) made from this would well exceed our needs per Kips design and weigh a lot less than steel ones. Sure they couldn't be driven into pavement, but could work in grass and sand.

[Bryan Cotton]

Cheap Ti rod:
http://www.titaniumjoe.com/index.cfm/products/bar/