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Where Do I find these? (Concrete block tie-downs)

dave_091

Active Member
Hi guys,

Does anyone know where to find these giant concrete block aircraft tie downs?
 

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Interesting concept.

In a very high wind, when the plane goes over, those will flail around and cause even more damage.

Good tiedowns are only needed in really high winds.

Dave
 
Seems like 20min to make a form, squirt the inside with a little diesel fuel and pour it up.

And, failure is a major option with the end use.
 
Or buy a few 5 gallon buckets, fill with concrete and embed an Eye bolt in each. Did that and carried two in my race car trailer to hold down our canopy.
 
These things are heavy

These things weigh minimum 100lbs each.
They are monstrous. It seems like everyone
has them to tie their planes down at the GA area
at this airport. Someone local probably put them
together.
I’m new here, Yellowknife, Canada.
 
It would take around 1,000 pounds to keep that plane safe, and even then I'd want the weights to be secured to the ground.

As an example, Cessna recommends 700 pounds strength for the tiedown ropes on my older C180. My RV-3B is low to the ground so the tiedown ropes splay out at a wide angle, and that increases the load per rope. Assuming half fuel and 850 pounds empty and a 70 mph wind, there could be more than 1,400 pounds per rope.

And I've been at a local airport in more than 70 mph wind, and walked among the dozen or so freshly destroyed airplanes, so I'm a little sensitive about this. Especially since I'm a retired aerospace stress guy.

Dave
 
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At a loss

It would take around 1,000 pounds to keep that plane safe, and even then I'd want the weights to be secured to the ground.

As an example, Cessna recommends 700 pounds strength for the tiedown ropes on my older C180. My RV-3B is low to the ground so the tiedown ropes splay out at a wide angle, and that increases the load per rope. Assuming half fuel and 850 pounds empty and a 70 mph wind, there could be more than 1,400 pounds per rope.

And I've been at a local airport in more than 70 mph wind, and walked among the dozen or so freshly destroyed airplanes, so I'm a little sensitive about this. Especially since I'm a retired aerospace stress guy.

Dave

Thanks for chiming in.

I'm at a loss here for tying down my aircraft. I just bought a new to me RV4
during a move without seeing the GA area here in Yellowknife.
After walking through the GA area here I had a reality check...
this winter outdoors will be tough on the aircraft.
I'm actually thinking about trying to do a quick turnaround and sell the
aircraft so that it doesn't have to endure a winter outdoors here...
poor decision making on my part.
 
Thanks for chiming in.

I'm at a loss here for tying down my aircraft. I just bought a new to me RV4
during a move without seeing the GA area here in Yellowknife.
After walking through the GA area here I had a reality check...
this winter outdoors will be tough on the aircraft.
I'm actually thinking about trying to do a quick turnaround and sell the
aircraft so that it doesn't have to endure a winter outdoors here...
poor decision making on my part.

Can't you rent space in a hangar somewhere just for the winter. If you don't plan on flying in the winter then can you not take the wings off and stick the plane in a storage space?
I agree with others that the concrete block is far from perfect, but if others at that airport have used it routinely without issue then perhaps the winds there are calm enough for this to work.
BTW my 5 gallon bucket filled with concrete is just around 100#. The block pictured looks a bit smaller.
 
I used a cat litter bucket as a concrete form for something similar to do nosegear work on my 172. It did not work. I didn’t weigh it but it wasn’t heavy enough to hold down the tail. There is no way I would endorse using this method for tying down any airplane outside.
 
Canadian winter is hard on stuff, especially up in Yellowknife. Blowing snow and wind. The snow will get blown into every little nook and cranny, and be hard as concrete. Ground is gravel at best, possibly rock.

Will the airport authority allow you to build a rough hangar, a glorified unheated garage out of 2x6? Probably won't even need a concrete pad, just the natural ground could suffice. If you aren't planning on flying, that would keep it protected from the elements. Might have to remove some of the electronics that can't handle -40° though.
 
These types are in Toad River Mile 422 in your neighborhood.

concrete_tiedowns_at_Toad_RIver_-_1.jpeg


And these in Chandalar Shelf of Alaska 5CD.

concrete_tiedowns_at_Toad_RIver_-_1_(1).jpeg
 
concrete

If one is going to make concrete block tie downs, i would do it differently.
I would use a flat concrete block no more than 1 1/2" thick, but like, 2 feet x 2 feet. this way a prop could accidentally run over it and not get damaged. One still has to worry about the rope thou. I hate the thought of someone (probably me) running into a block of concrete placed randomly in the middle of a ramp.
 
lift

Those blocks weigh 100 to 150 lbs ea. A good gust can lift each wing 400 lbs in addition to the empty weight.
 
Why not use something like these. A set of six for $40 on Amazon. https://www.amazon.com/MTB-Anchor-P...keywords=tie+down+auger&qid=1628068373&sr=8-5 They use these for mobile home anchors in large sizes. Using three under each wing tie down point a couple feet apart forming a triangle would be much better than a #100 cement block IMHO.

The problem with those is that they tend to churn up the soil, which then has less holding power. Stakes, several of them, at angles to each other work better. Although these are like knots in this way - if you can't get it right, use many.

Dave
 
Why not use something like these. A set of six for $40 on Amazon. https://www.amazon.com/MTB-Anchor-P...keywords=tie+down+auger&qid=1628068373&sr=8-5 They use these for mobile home anchors in large sizes. Using three under each wing tie down point a couple feet apart forming a triangle would be much better than a #100 cement block IMHO.

I thought I remember reading in the OSH notam not to use “dog leash” tie downs. I saw some people that had them, and they always seemed half pulled up…
The CLAW tie down seem to hold really well
 
Hi guys,

Does anyone know where to find these giant concrete block aircraft tie downs?

I sympathize with Dave's blight, from what I can remember about Yellowknife is that the airport isn't very GA friendly (odd because GA is what opened up the vast Canadian North). Big open sparse tie down area, I imagine winter operations would be worse than brutal. Think 'Ice Pilots' for those that saw the TV series.

If concrete tie down weights are what other local plane owners are using, guess copying them is best course of action, the heavier the better. I'd also suggest you look into wing covers, maybe ones with spoiler strips across the top to kill any potential of high winds lifting a wing (& block).

I see you had scorching record high temps up there these last few days. A weird time to be thinking about winter tie downs!
 
These types are in Toad River Mile 422 in your neighborhood.

concrete_tiedowns_at_Toad_RIver_-_1.jpeg

Off topic, but this *kills* me to see this sort of thing...setting tools and whatnot on the wing like that. Ever had a drill fall over? Yeah, me too. Now think about any one of those things putting a nice dent into that nice smooth wing skin.

Do whatever you want, but I *never* use the wing as a tool bench.
 
Hi guys,

Does anyone know where to find these giant concrete block aircraft tie downs?

Try the local hardware store and ask for a dock anchor. The ones we use for our dock weigh 150lbs.

Alternatively, if you always park in the same spot, you could use a hammer drill to make a hole for a long-shaft eyebolt and epoxy it into the Canadian shield.
 
That's impractical if you go somewhere other than your home airport. Different airports have different anchor spacing and the positioning of your airplane may vary.

Remember, the ropes should be taut and the knots snug against the rings. Doubling up on the ropes is a very good thing because that reduces springiness.

Generally, we lose roughly 50% with a knot. Choose your ropes accordingly.

I plan to buy 1/4" Endura Braid for my RV-3B. It's good for 4,500 pounds which will allow for the reduction due to the knots. It has decent hand feel and takes knots fairly well, too. On my C180, I use 3/8" Regatta Braid, good for 4,800 pounds, with excellent feel and knotting.

Dave
 
Hearing all the discussions here and on some of the Oshkosh threads about their favorite anchor system or this rope versus straps, etc. - I wonder what the anchor point in the wing of an RV is good for? Marginal threads in an aluminum block in the wing?? I dang sure wouldn't stand under a 3-4,000 lb block hanging from the tiedown under the wing of an RV! Intuitively, I'm thinking 1,000 lbs is about it.
 
Tiedown bar strength calculations

Hearing all the discussions here and on some of the Oshkosh threads about their favorite anchor system or this rope versus straps, etc. - I wonder what the anchor point in the wing of an RV is good for? Marginal threads in an aluminum block in the wing?? I dang sure wouldn't stand under a 3-4,000 lb block hanging from the tiedown under the wing of an RV! Intuitively, I'm thinking 1,000 lbs is about it.

In the RV-4, the 1/2" bar is held on with three 3/16" bolts. 40,000 psi tensile strength for 6061 alum. 1/2 x 3 x 3/16 x 40,000 ~ 11,000 lbs.
However, looking at the structure the bar bolts to:
1 bolt through (1/8 + 1/4 + 0.04) x 3/16 x 40,000 ~ 3,112 lbs
1 bolt through 1/16 x 3/16 x 40,000 ~ 468 lbs
1 bolt through 0.040 x 3/16 x 40,000 ~ 300 lbs
About 3,880 lbs

As for the strength of the 3/8-16 threads into the bar, assuming a conservative 1/32" thread width or contact area: 3/8 x Pi x 1/32 x 40,000 ~ 1,472 lbs per thread. With 5 thread engagement ~ 7,300 lbs. With 10 thread engagement ~ 14,700 lbs. Drawing specifies 1" of thread (16 threads). So close to 23,000 lbs. Someone please verify those thread strength numbers.

For the RV-4 it appears that the structure that the bar is bolted to is the limiting factor.

Currently have my wheels off the ground to fit gear leg fairings and wheel pants, hanging on engine lift to engine mount near firewall. I guess my worries about using 3/8" bolts screwed into the tie-down holes as sole support are unfounded.

Finn
 
Is the tie down area at Yellowknife paved?

If it were me, I'd ask permission to dig a hole (sides tapered out) and fill with concrete add an eyebolt.

I didn't consider frost line, to avoid frost heave, you'd have to get below that depth.
 
Don't confuse tensile strength with shear or bearing strength. And check your material strengths again. Also look at the fitting's flanges as a single part, with however many bolts your particular RV uses.

Dave
 
Don't confuse tensile strength with shear or bearing strength. And check your material strengths again. Also look at the fitting's flanges as a single part, with however many bolts your particular RV uses.

Dave

Shear strength is 30,000. So that reduces my numbers by a factor 0.75. Structure the bar bolts to is then 2,900 lbs.
In my RV-4, the tie-down bar is a simple 6061-T6 0.5x0.5" bar. No flanges.
Drilling a 3/16" hole through it only leaves 1/2 - 3/16 = 5/16" material around bolts. 0.5 x 5/16 * 30,000 ~ 4,600 lbs.

Still would like to know if my thread strength calculations are right.
(3/8 - 1/32) x Pi x 1/32 x 30,000 ~ 1,000 lbs per thread?

Finn
 
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