Casting for flagpole?

[Calle Nordström]

Hello,

I have cast for a flagpole. I made a hole of 55cmx55cmx65cm. I used expanding concrete and it took 12 bags, i.e., 300kg.

Now, when I read, I see that you should really dig 100-120cm and have a 40cmx40cm hole.

The question is whether you think my foundation will work? The flagpole is 12m and made of fiberglass, weighing 38kg including the base.

//Calle

 

[AG A]

Unfortunately, I am afraid that the flagpole will topple over.

 

[Marsman80]

It's certainly better to have a deep hole, but what you've done should work as well. It definitely depends a lot on how stable the ground is and how much it blows. I can't imagine it blowing over, but if it starts to lean more and more, it might be time to create a new "foundation". I personally used an earth auger and drilled straight down about 50 cm and then in 3 different directions from there, as it felt more stable than a straight pier. The earth auger was only 22.5 cm in diameter, but my 12 m flagpole stands firmly despite a windy location.

 

[MathiasS]

You have cast a 300kg lump! It's not going to fly away. I didn't even get a meter down before hitting rock. I have a simple casting pipe with concrete, a fraction of what you have, about 45 liters. That flagpole has stood straight for over ten years now.

Start hoisting the flag and see what happens, I think it will work excellently. If it's not okay, it's unlikely anything dramatic will happen.

 

[Calle Nordström]

Thought so too, the weight in the plinth is 80 times the weight of the pole, a flag doesn't have much wind resistance since it constantly turns with the wind. Will have to try and see, not more than having to re-cast if it goes wrong.

Thanks for the reply anyway!

 

[Calle Nordström]

Just wanted to let you know that the base works fine, flagged in a windy situation without moving a millimeter.

 

[Stefan N]

Yes, it will remain standing.

 

[niklasn]

It will probably stay standing, but as a comparison, I can tell you about my sailboat - 5 tons total weight, of which 2.8 in the keel, with the center of gravity approximately 1.40 below the water surface. The mast is about 16m above the water with a slender profile, more streamlined than a flagpole.

In a wind of 7m/s, directly from the side without sails, the boat leans about 15 degrees... So don't underestimate the effect of the wind, especially as the force in a flagpole is at the farthest point from the base.

 

[jvhavshus]

Tänkte bara meddela att grunden funkar fint, flaggat i blåsigt läge utan att den rört sig en millimeter.

Hej Calle!

Jag är i samma sits som dig nu, hsr ett hål på cirka 55x55x70cm altså 70cm djupt. Min flaggstång är identisk i mått och vikt med din.

Hur ser din ut efter alla dessa år? Finns här någon annan som haft samma bekymmer?

 

[MathiasS]

Du har ju gjutit en 300kg-klump! den kommer inte flyga iväg. Jag kom inte ens en meter ner utan stötte på sprängsten innan detta. Har ett enkelt gjutrör med betong, dvs en bråkdel av vad du har, cirka 45 liter. Den flaggstången har stått rak i över tio år nu.

Börja flagga och se vad som händer, jag tror det funkar utmärkt. Om det inte är ok lär det knappast ske något dramatiskt.

Ytterligare tio år senare står min flaggstång fortfarande kvar.