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Opinions on cinder block walls?

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#26 WoodyEnd

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Posted 13 August 2019 - 08:25 PM

If you want the walls to be bullet resistant you need to use 8" block and fully grout it.  To manage the heat issues I would insulate the outside to reduce heat gain and insulate the inside to reduce the heat transmitted inside. You also need air conditioning or at least a serious ventilation fan turned on around sunset to get the inside down to ambient.



#27 SnowSailor

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Posted 14 August 2019 - 12:04 AM

If you want the walls to be bullet resistant you need to use 8" block and fully grout it.  To manage the heat issues I would insulate the outside to reduce heat gain and insulate the inside to reduce the heat transmitted inside. You also need air conditioning or at least a serious ventilation fan turned on around sunset to get the inside down to ambient.

Do you mean solid 8x8x16 blocks? Or just the regular 8x8x16 hollow-core blocks? I talked to a friend that does a lot of shooting and he said most of his larger rifles would go straight through a cinder block so I'm guessing I'd need the solid ones (probably more expensive, heavier, and much more prone to keep the heat in).



#28 SnowSailor

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Posted 14 August 2019 - 12:08 AM

I went to the hardware store yesterday and got 20 cinder blocks to build a small wall at my house. I also got two sheets of wood to block the sun from hitting the wall (sheet metal larger than 2x2' was only available via special order, so I couldn't get any. I'd imagine metal would be better than wood anyway, so if the wall stays cool enough with wood then metal should be even better). Tomorrow should be pretty sunny, so hopefully it gets blasted with as much sun as possible so we can see what happens. The thermometer also came today and I measured the wall (without the wood blocking the sun, which was behind clouds for a lot of the day) to be ~85F on the side facing the sun and ~81F on the north side. The ambient temperature was 80F and dropping. I didn't measure it after the sun went behind the trees (to figure out how quickly it would cool down), but I will tomorrow.


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#29 fellers

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Posted 14 August 2019 - 05:40 PM

Paint your walls with a thick bright white acrylic paint. Foam insulation inside the walls and some steel plates to stop projectiles from penetrating. Not cheap to stop the heat, moisture, squaters, and bullets...lol

#30 WoodyEnd

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Posted 14 August 2019 - 05:47 PM

Do you mean solid 8x8x16 blocks? Or just the regular 8x8x16 hollow-core blocks? I talked to a friend that does a lot of shooting and he said most of his larger rifles would go straight through a cinder block so I'm guessing I'd need the solid ones (probably more expensive, heavier, and much more prone to keep the heat in).

The holes are for rebar to be inserted and then filled with concrete grout which gives the walls strength.  This will stop almost anything short of a 50 caliber. 

 

http://ncma-br.org/p... Resistance.pdf


Edited by WoodyEnd, 14 August 2019 - 05:49 PM.


#31 fellers

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Posted 14 August 2019 - 06:30 PM

Paint your walls with a thick bright white acrylic paint. Foam insulation inside the walls and some steel plates to stop projectiles from penetrating. Not cheap to stop the heat, moisture, squaters, and bullets...

#32 SnowSailor

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Posted 16 August 2019 - 11:47 PM

So I had a few sunny days and did some temperature measurements on the cinder block wall. With wood in front, the wall didn't get much above ambient temperatures and the inside of the wall was similar (although it was slightly cooler). I am satisfied with those results and I think cinder blocks are a valid material as long as there's something to shade them from direct sunlight. I talked to Lloyd from DSW and he told me about their roll off roof design, which I like more. It allows for lower walls once the roof is rolled off, and it's easier to construct it so that there's no chance of the roof hitting the scope even when it's at its highest point. I need to talk to a metal fabricator to get an estimate of the cost, but I can't imagine it'll be super cheap (as cheap as some wood and flat sheet metal).



#33 Tom K

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Posted 17 August 2019 - 12:22 AM

I think that you are on the right track - I look forward to seeing your progress.   


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#34 rgsalinger

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Posted 17 August 2019 - 09:38 AM

Actually if you have low walls you really need to think about wind and light become a problem. The bigger the scope the bigger the problem with wind. It's no fun to have lights shining inside at night either. So, low walls are a good solution if you really want horizon to horizon access but you will have to deal with more wind and light issues. At DSW they have cited the facility to minimize wind and there is no visible light at all out there.

 

I'm not surprised that the cinderblock construction looks good.  We have concrete block walls and the holes are filled with rebar and concrete and, as I said before, there are no problems imaging after twilight ends. Several  other observatories at the same very hot desert location have the same basic design and again, the owners are happy with the results that they are getting.

 

Rgrds-Ross




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