Laurent:
I appreciate your problem. The best thing to do is to extend the concrete above
ground so you can visually monitor the condition of the base concerning rust.
I would leave the hole as it is. Pour the concrete to about 300 mm below the
surface. At that point I would make a form with the plan dimensions need for
the tower base. I would pour that size and would extend it say 100 mm minimum
above the potential ground surface. Slope the top of the concrete to keep the
standing water off and your set.
Regards
Lonberg Design Group, Ltd.
Hank Lonberg, P.E.,S.E. / KR7X
President
-------------- Original message --------------
> Dear OMs,
>
> My project is to erect a self supporting tower i bought a few monthes
> ago. The tower is 13 meters (36 ft) high and weights around 250 Kg. I
> planned to dig a square hole of 4x4x4 (based on what i read about
> similar towers), to put a rebar cage and a tower base into it, and to
> pour the concrete.
>
> However, reality differs from my plans, and i have a few questions.
> Please note that the tower has been "home made" (not by myself). I am
> confident in it but i can't simply "ask the tower manufacturer" my
> questions about the foundations. That's why i need your help.
>
> I asked one of my neighbour if he could dig the hole (he has machines
> for it). He accepted, and i explained him what i wanted. Unfortunately,
> he came one day with his machine while i wasn't here and dig (dug?) a
> hole that wasn't deep enough (just 2 ft). When he came back to check if
> that was OK, i told him that i needed twice that depth. He came back
> another day while i wasn't here (really bad luck) and dug again... i
> ended with a hole that is now too big ! It's now 5x6 and of 7 ft depth.
>
> My first question is about the foundations dimensions. What do you think
> about them ? Does 4x4x4 seem sufficient to you, or should i keep 5x6x7 ?
> (of course, i could keep the big one as a "safety margin", but if 4x4x4
> is already safe, i see no interest in paying the additionnal concrete it
> will take to fill the big hole).
>
> If a want a smaller hole, i can simply put back some ground (?) into it
> for less depth, but i can i do for a smaller "area" ? I could build a
> wood frame for the dimensions i want, put it into the hole, and put some
> ground around it, but i wonder if it will be sufficient, because when
> i'll pour concrete in the frame, it will have a great pressure from
> inside to outside.
>
> About the top of the concrete base: Usually, the concrete base is higher
> than ground level. What's the reason for this ? I would like better to
> have it lower than ground level. That way, i could have just the tower
> base coming upside. In my garden, 5x6 of grass would be nicer than 5x6
> of concrete. Of course, rust on the tower base would be a concern, but
> if it's the only reason, i feel i can deal with it.
>
> About the tower base (to be sealed in the concrete). How deep should it
> go into the concrete ?
>
> Thanks for your help ( and sorry for my bad english)
>
> --
> Laurent F1JKJ
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather
> Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
> and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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