Away-from-home-tiedowns

[Dave S]

This thread is in part a response to Wayne T (AKA Twister) who queried in a different thread a while back about what people do to tie down on remote strips they visit. I didn't have any photos at that time, but, here goes.

I fabricated a set of three tiedown anchors patterned after the EAA example which they have on their website.

Photo 4368 shows the stakes (which are 5/16" Diameter HRS rather than 1/4"; and, 24" long rather than 18" shown on the EAA design) and the tiedown anchors.

Photo 4370 and 4372 show the detail of the attachment point....the triangle is 14 gauge 4130 rather than the 1/4" HRS example of the EAA design. Washers and reinforcement on both sides. U-bolt is a narrow 1/4" one.

Photo 4371 is the details of both ends of the rods.

Photo 4367 shows how the stakes would go through the plate and into the soil in a Teepee fashion.

The whole business has three anchor plates and 9 rods. I use my trusty geologists hammer/pick to pound them in and pry threm out. The EAA design shows a small rope puller to wrap around the ends and yank.

A person should angle the tiedown rope rope at least a 45 degree angle....not straight up from the anchor---much less succeptible to being pulled out then.

This doesn't work everywhere, but it works most places.

Sincerely,

Dave S
KF7 Trigear - Flying
912ULS Warp Drive

[Dave F]

anyone who was a sun n fun a few year ago realizes that good tie downs a a great asset

http://www.youtube.com/watch?v=G9c_o2mEfGg

[Av8r3400]

...and "dog screws" aren't worth their weight in dog boogers for tie downs.

Ask the guys at the Zenair booth if you don't believe me.

[DesertFox4]

At AirVenture 2012- 3 Kitfox factory demo aircraft survived approx. 70 mph winds and driving rain using newly purchased Claw brand tie downs. One Kitfox was facing directly into the wind , one was a direct broadside and the other tail first into the wind. Good test, although a little unsettling to watch as the one into the wind was "flying" enough to lift both main gear off the ground. No damage to any of the 3 aircraft.


I have the same opinion of "doggy cork screws" as Av8r3400.

[Av8r3400]

I use a "Claw" set also. They are very nice, work excellent, but at 8 pounds a little heavy.

We may have to agree to disagree about the rope placement. IMO, speaking as a recovering engineer, vertical to the tie down is definitely strongest for the airplane structure and the dynamics of the anchor.

I've often thought of making up a set of those EAA tie downs. Maybe that will be part of my project plane...

[SkySteve]

I made and use the EAA style tie downs that Dave S made. They are light weight and fit nicely in a nylon drawstring bag. Although I've never tried them in a hurricane, I have had them in some strong winds and micro bursts that did flip other planes over and they held very well. I use 3/8" rock climbing ropes with a breaking strength of 4-5,000 lbs each. I position the tied downs directly below the wing strut and loop the ropes thru the strut tie loop, around the strut then back thru the strut tie loop again. The knot I use is the standard airplane double half hitch slip knot that can be adjusted by sliding it up or down the tie rope, then add another single half hitch for safety. Place a "pointy end" toward the plane so you have 2 stakes toward the wing tip.

[Dave F]

I made and use the EAA style tie downs that Dave S made. They are light weight and fit nicely in a nylon drawstring bag. Although I've never tried them in a hurricane, I have had them in some strong winds and micro bursts that did flip other planes over and they held very well. I use 3/8" rock climbing ropes with a breaking strength of 4-5,000 lbs each. I position the tied downs directly below the wing strut and loop the ropes thru the strut tie loop, around the strut then back thru the strut tie loop again. The knot I use is the standard airplane double half hitch slip knot that can be adjusted by sliding it up or down the tie rope, then add another single half hitch for safety. Place a "pointy end" toward the plane so you have 2 stakes toward the wing tip.

Smart decision. -> I use 3/8" rock climbing ropes with a breaking strength of 4-5,000 lbs each

I have banned the use of those cheap coloured ropes for tie downs at my airfield. If you read the WLL (working load limit) you will see they only good for 250 lbs !! We had a ultralight once break free and cartwheeled into a ball of mangled aluminum. Luckilly it did not hit anything else.

also those cheap nylon straps are poor as well -- Read the WLL to see what they are rated for. Saving a few buks on ties down can wreck an airplane.

The dog style screw ins are worthless as well - you need at least 1500 lbs hold strength at the bare minimums. The hay bale screw ins work well but are heavy.


This is similar to what I mean.

[HighWing]

I made a set of tiedowns I used on my first Model IV. They were drilled aluminum bar stock to hold the angle of the stakes. I only used two stakes. I like the three stakes, but probably would weld tubing into the flat plate to mainain the angle in the event of strong vertical loads. I think maintaining the angle would enhance vertical resistance.

For some reason, the claw seems to have a weakness in that the driven stakes form a cone while underground and if pulled vertically, I would think that if one spike moved a bit, the moved soil might help reduce the risistance of the remaining soil. In my mind's eye, I can see the soil cone being suspended by the three stakes somewhere other than in it's original location. I like the divergent angles better.
Lowell

[SkySteve]

I used 3/8" flat steel for the plates. I think each of the three sides is 2.5" long, but they are at my hangar so I can't verify that. As Lowell did, I did drill the holes at an angle to guide the rods at the property angle as the rods are driven into the ground. Instead of a U bolt in the center, I used an eye bolt so I only had one hole, providing additional material for the plate strength. Prior to inserting the eye bolt I welded it closed so the eye couldn't pull open, again providing additional strength. Also used a nylock nut on the bottom. The final touch was bright colored paint so they would show up when on the ground. Those buggers could really tear your toes open when running around camp barefoot or wearing sandals, especially when you are out flying and someone else runs thru your camp.

[DesertFox4]

For some reason, the claw seems to have a weakness in that the driven stakes form a cone while underground and if pulled vertically, I would think that if one spike moved a bit, the moved soil might help reduce the risistance of the remaining soil. In my mind's eye, I can see the soil cone being suspended by the three stakes somewhere other than in it's original location. I like the divergent angles better.
Lowell

Perceived weakness? We had 3 aircraft go through an actual event and survived undamaged. Not many of the home engineered tie downs get real world testing courtesy of Mother Nature. Every type of tie down on the North display area got the real test that day. Some did not fair as well.

Since photos speak volumes here is a couple of the above mentioned "event". These storms are not uncommon at AirVenture.

"This is going to be fun."
Oshkosh 2012 trip 399.jpg

Gust front arrives in 5 minutes. Brace for impact.
Oshkosh 2012 trip 401.jpg

Van's little piece of history likely also save by "THE CLAW".
This was about 30 feet from Kitfox Aircraft's tent.
Oshkosh 2012 trip 213.jpg
What is left of this line of Port-a-Poddies after the storm passed. There were about a dozen just before the storm hit.
Hope folks didn't seek shelter in any of those. We never heard where they ended up or how many aircraft were hit by flying outhouses.
They might could benefit from tie downs also.
Oshkosh 2012 trip 406.jpg