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HovisKM
10-05-2010, 02:48 PM
I am going to be pouring legs for my benches in the next week or two and have a couple of questions for the concrete experts on the site. I will be pouring 8" legs using sonotubes. I will be drilling 9" holes. . The questions I have are.

1. What size of rebar, how many & how to configure. I will be driving them into the ground to hold.

2. What is the best way to stabilize the tube. It will be in a farily tight fitting hole. I figured staking and stabilizing with arms by drilling screws from the inside of the tube toward the top. Or, should I actuall frame the three legs at the top to make sure spacing is correct and add stabilizers to that.

3. I will have about 30" of tube above ground. Thus 18" below, however, I am wanting to drill about a foot deeper because most of the 18" depth is fill dirt that is what I would call semi-packed. In a tight fitting hole, what is the chance of concrete push out if I do a single pour or should I do a two part pour by allowing the first foot or so of concrete to partially set, then pour the rest of the tube? If so, how long or should I just use a rod to check how set up it is.

4. What should I use as a release agent on the inside of the sonotubes so that they are easily removed above ground.

thanks
Hovis

Larry Elliott
10-05-2010, 11:51 PM
I'm not a concrete man by any stretch of the imagination, but when we built new benches at the range I was a member of in Seattle we used sonotubes with several (can't remember how many, but 4 to 6 fits my remembery fairly well) in them. Can't remember if the rebar was driven into the ground, but it was bent over at 90 at the top to reinforce the top and the post. The sonotube wasn't braced anymore than it would be for anything else as I remember. The rebar was 3/8" I think. Motor oil works as a release agent.

Sorry I can't be much help, but that's what I remember from 20 years ago.

alinwa
10-06-2010, 02:14 AM
1. 3 sticks #3 is adequate but 3 #4 is probably just as cheap and is better/easier/stouter. 3 pcs is because it's less than 4 but still 3D in cross section. Space them 2"-3" from the outside of the concrete.

2. I would frame the three legs at top. This isn't hard, three small hunks of wood like pcs of lathe or 1X2 wood stake @ about 6" long will suffice. Drill the holes, position the sonotubes and then fasten the stakes around the top underside. This will stabilize the tube.

Remember that the tabletop (I'm assuming you're pouring the top w/legs???) weighs 460-600lb depending on dimensions...... it can't just set on the sonotubes! The support/bracing adequate for 600lb will stabilize the tabletop and the wee estake's will hold the top of the tubage. If the tubes are cut short (recommended) then you can hang them from the tabletop and let them dandle into the holes. This in turn brings us to point 3.

3. NO chance, zero, nada. if it's actual concrete you're pouring. You could have 12" diameter holes and 8" tubes....... I say DIG deep and dangle the sonotube into the hole at least 6". Now you can pour mud to your heart's desire and if it DOES start to ooze just shovel some dirt on the ooze and it'll stop. DRY dirt, like sand even. You're just causing the concrete to crust over, it'll suck the moisture.

TAMP, stick, chunk or in other words WORK the concrete down the tubes. Dump it in and then jam in and tamp the peewaddy out of it all. You need a 4 foot hunk of something like a broomstick, we'd use a 4ft woodstake. You also can then feel for and work around the bar. BTW the bar MUST extend up and into the tabletop w/90's and you must lay a mat of bar in the tabletop itself on max 18" centers and suspended in the middle of the tabletop thickness. When you pour out the top tamp it well all the way around the edges and tap the sides of the form rat-a-tat-tat with a hammer to drive the fat or cream to the edges getting rid of rock pockets. Form edges will most likely be 2X4's standing on edge? for a 450lb top. 2X6's will give you a 600-700lb top.

4. No need for release agent in sonotubes. Sonotubes are waxed and peel off in a circular fashion. Just start the peel up under the table where it's hidden and peel 'er down like wet jeans off a ....... but I digress. Strip them next day.

Call me @ 360 904 6941 if you've got any sort of question that can't be answered here. Call me during the pour if you have a panic. I sling mud for a living, poured 450 tons of it today.

Good cheap release agent for the formwork is 5gal diesel/1qt Dexron tranny fluid.


When you trowel the top take twice't as long as you think you need. You need a magnesium float first, then immediately edge to break the corners using a 1/4"-1/2" radius edger. Now trowel it again making sure it has a slight crown. Wait 20min and wipe it smooth with a steel trowel. This is thin spring steel, sharp edges, will cut you. Now, over the next hour hit it with the steel trowel every 20min or so as it dries. bear down, hard, with the trowel very slightly tilted. Keep letting the top dry and re-steeling until it "burns off" to a glassy smooth finish. When troweling with the steel trowel you will keep increasing the angle such that you're laying down a smooth "fuzz." If you get too steep you'll pop rocks or cause chatter. By the time the mud is hard enough to "burn" you'll be bearing down with one hand on the handle, two fingers on the tip or hand on the lower "steel" blade and BEARING DOWN with the blade tilted almost to 45*


Some tips:

-spend extra time on the forming, make it twice't as stout as you think you need.

-If you've got limitless time and it's not raining caulk all the downside corner edges with $1.99 painters caulk. It's the stuff that goes on milky white and dries clear, peels off like silicone rubber. Tool it into the corners with your finger, make it nice and match the radius of your edger. Stuff takes a day ore two to dry clear. You'll thank me the first time you stand up under the table and don't gash your leg. If you don't have time for the painters caulk you can carefully cove the edges using duct tape but this will show ugly when you strip the forms unless you carefully strip and "face" same day. This is wickedtricky.

-If you spend days on the forming make sure that you use plenty form release applied just before you pour, strip following day.

-buy some 8D and 16D duplex nails for forming always thinking about how you're going to disassemble the form after the concrete is hardened. Leave "stripping gaps" for relief.

-remember that the forms must come OFF. This is harder to plan than would first seem obvious. For instance, how ya' gonna get the bottom plate off around the legs?

that's all I can think of offhand.

al

LHSmith
10-06-2010, 07:40 AM
Sonotubes are the way to go....no sharp corners digging into your legs and much more legroom. I poured my tops into a single form that I kept reusing. Poured in my garage. Used 2x4's, and was able to transport tops with 3 people. Top is "T" -shaped , inside corners have large radius (made by taking Composite decking, adding a few kerfs to get a gentle bend. Ditto what Al said about underside edges...I used pine moulding instead of caulk for a more pronounced radius. I put pins in the sonotubes and drilled holes in the tops underside to help keep the tops in place. One regret is I painted some tops and caused bags to slip.

HovisKM
10-06-2010, 08:46 AM
Thanks guys,

Al, I'll keep your number handy. I thought you were the concrete man around here. The tops are poured seperately and I've had most of them about a year waiting. A local concrete company that builds septic tanks, sewers and burial vaults poured them for me, only 28.00 ea and they provided the rebar and put lifting insert studs in the tops which work great for lifting with the tractor. I do have to break the edges and smooth myself but I have a large file that does the job and then a 4" grinder to smooth the edges from there.

A couple of more quick questions. I'm thinking the rebar should extend out the top and then cut them off after the cure. Also, how long should I wait to set the tops on the legs? Also, what should I use to attach the two, mortar or concrete glue? I would like to have the option of being able to remove the top if necessary.

Thanks guys, hope to start pouring this weekend. Figured I'd do two sets and see how they come out and then pour the rest the following weekend.

thanks
Hovis

Boyd Allen
10-06-2010, 10:34 AM
This is a little off topic, but I am posting more for anyone else that is looking at this thread, and who might be thinking of building benches.

Good luck with your project.

Fresno Rifle and Pistol Club did a cooperative project with the Visalia range, sharing forms for benches. The design was by Lee Six. Lee built the prototype form, which needed some redesign to make it easier to use and build. Our club (three of us) built five forms with interchangeable parts, and then Lee built a third generation form. We used the last six to pour 42 at Fresno. Visalia used all seven to pour 28 at that range.

Holes were drilled in the slab, for the rebar, the forms set in place, rebar placed into the holes, which was continuous into the tops, and additional pieces placed and wired. Each bench was a one piece pour, top and base at the same time. They were a lot of work.

The pictures are of the Fresno range where the firing line slab and roof are 256' x 30'. The form picture is after 15 years of being left outside. There are some spacers missing. The form has a few tricks that you can't see to facilitate stripping.

http://usera.ImageCave.com/Boyd/FRPCbenchside-copy.jpg
http://usera.ImageCave.com/Boyd/FRPCfiringline-copy.jpg
http://usera.ImageCave.com/Boyd/benchformtopview-copy.jpg

alinwa
10-06-2010, 01:09 PM
Thanks guys,

Al, I'll keep your number handy. I thought you were the concrete man around here. The tops are poured seperately and I've had most of them about a year waiting. A local concrete company that builds septic tanks, sewers and burial vaults poured them for me, only 28.00 ea and they provided the rebar and put lifting insert studs in the tops which work great for lifting with the tractor. I do have to break the edges and smooth myself but I have a large file that does the job and then a 4" grinder to smooth the edges from there.

A couple of more quick questions. I'm thinking the rebar should extend out the top and then cut them off after the cure. Also, how long should I wait to set the tops on the legs? Also, what should I use to attach the two, mortar or concrete glue? I would like to have the option of being able to remove the top if necessary.

Thanks guys, hope to start pouring this weekend. Figured I'd do two sets and see how they come out and then pour the rest the following weekend.

thanks
Hovis

That's a great idea, and 28.00 each is a real deal.

I would probably not leave the bars stick out the top..... what's the gain?

Tubes will cure to accept tops in 24hrs but they'll chip easily for up to three days..

I don't have any great idea'rs as far as hooking then together. My first thought is to set the top in place and drill down thru the top into the leg and drop in a pin of rebar. grout the hole.

hth

al

Pete Wass
10-06-2010, 05:21 PM
I will make the tops just long enough to accomodate the front reat and rear bag lengthwise. I hate long benches because I have to drape myself over the rifle's stock. I find that leads to gun handeling problems. I like the benches that use a straight angle from the tail up to the mid-point. The benches @ Holton, Michigan are built that way and I find them superb. Some of them are a dite short but the newer ones are a bit longer and RIGHT.

The other thing is the rear leg. I want to get behind my rifle so I want the rear leg forward of the rear edge of the bench by eight or ten inches. I once saw a picture of some benches that were done that way. There is no need to have a leg all the way back on a concrete bench.

The issue here is Benches are FOREVER. Once they are done, one must live with any mistakes they made; most of us anyway.

skeetlee
10-06-2010, 05:52 PM
Kevin
Also feel free to call me anytime. I also have about 20years of concrete experience, and i am also in the middle of building my range. My set up is only going to be two benches though. 200 yard range maybe 250. I am going to build my bench tops like the st Louis tops if i can find a print. I really like they way they feel. I will pour my tops seperate as well, and i will use an epoxy to bond the tops to the sonotube. Im going to form a cup out into the bottom of my tops for the sonotube to rest in. That will also allow for some room for the epoxy to ooze out and flow around the tube. I will then use my hand to smooth the epoxy and make sure all is sealed. One thing different about my project as apposed to the st Louis benches, is that my sonotube will not have an expansion joint around them. If you notice you can actually move the benches in st Louis because of the expansion gap around the tubes. The pad that my benches will sit in will be 100% frost-less!! The pad should not ever move. Footings are the key here. I will also drill # 5 rod into my sonotube below grade so the tubes and slab will bond.
Back to the tops. I am not 100% sure what type of epoxy we use there at the city, but it is some really good stuff. I would also think a brick mix mortar would work but i am going with the epoxy. I dont personally see a need to use any reinforcing rods to connect the tops to the tubes, but maybe this is a mistake on my part? Time will tell, but i just about bet a nickel ill be fine. I will make the cut out in the bottoms of the tops about 1" larger in diameter than the 8" sonotube i plan to use. That will give .5" all the way around the tube for epoxy, plus there will be epoxy on the tops of the tubes before i set the tops. As far as putting a radius on the bottom edges of the tops. I will use my rubbing stones the following day after poring the tops and rub nice smooth corners. That wont be an issue for me. Time is my issue! LOL!! My folks are building a new home on one of our farms and i am helping them with all the concrete work, so it may not be until next spring for me. I will get the tops poured this year with the left overs from the garage floors and sidewalks or whatever the case may be. I will simply burn the tops in with my well broken in steel trowel. I will use a nice gentle radius edger for the top edges, along with my china bristle paint brush to smooth the top edges. It works really well after the concrete gets hard. I just use a bit of moister and lightly brush the edges smooth, If needed. It may not even need it as my edgers are also well broken in. LOL!!! Actually i may even strip the forms and use the china bristle to smooth the sides as well. that way i am asured no honeycomb or stuburn rocks show there ugle edges. I wish i lived a bit closer Kevin if so i would just come over and help. Lots of good advise here though. I bet everything turns out just fine. Lee

HovisKM
10-06-2010, 10:35 PM
Lee,

St. Louis will loan you their form. All they require is a deposit that you get back when you return the form. I don't remember if they have one or two. Ron can fill you in on the details. My tops are very similiar to theirs.

Hovis

Bob Kingsbury
10-06-2010, 10:36 PM
I built mine the cheap way ( LOL). First I poured a 22 inch thick slab, 10ft x 10ft. Then
I used 10 inch cement blocks to form a T. Poured the top in my garage. Its 5 3/4 thick and
got 7 guys to help move it to the site. Oh ya, it has 10 full sticks of rebar in the blocks and top.
My rail gun loves it, but Its the last one I'm building

Mountain Mike
10-07-2010, 12:32 AM
If you are precasting your tops, I recommend you precast the legs as well. The rebar should not touch the face of concrete anywhere. Plastic bar spacers are available for sides. A single 3 inch cube of concrete is available for the bottom (under one bar). Like Al said, I would use 3-#4 vertical bars. If you want in insure no cracking or splitting in the legs, I would use #3 bar hoops at 6 inches on center full height. Bar clearnce should be 1.5 inches except 3 inches at bottom. Stand the tubes up on a concrete slab with plastic sheet bond breaker (will require braces to hold in place). Cast the tops as Al recommends and add the 0.5~1 inch depressions for the tube tops. At the range, drill or dig 12 inch or larger holes to a depth you are comfortable with. Put some concrete in the bottoms of the holes, set the legs in (needs jig to keep them straight and insure they will fit the depressions in the tops. Level the leg tops (very important). Tamp in concrete in the annular space around the legs and let the thing set up for minimum 3 days (7 is better). Set the tops on the legs in a bed of epoxy mortar. I would get some Hilti capsule anchors (5/8" is good) with #5 dowells. Drill through the top into the leg and set the dowells in the capsules. Dowell top should be about 1/2" below top of table. Don't worry about release agent in the sonotube which is intended to be a single use item. For curing your bench tops, spread several layers of burlap on them after finishing and keep it really wet for 3 (or 7) days.

Donald
10-07-2010, 02:33 AM
Check your area phone book looking for a company that casts concrete burial vaults. They use a very strong concrete. I found one only 8 miles for me. I talked to the the owner and he said when they poured vaults they always had a bit left over. I asked him if I make a form out of 2x4's that he could take apart, what would he charge me to cast about 10 tops. I told him he could have all winter to get them cast. He did a bit of figuring and said how about $20 per top. The next spring we picked up the 10 tops, they even had threaded lugs in each top so we could pick them up. We stacked the concret blocks with liquid nails, and filled the cavities with condrete and rebar. Then when cured we set the tops on and used liquid nails again. It let you slid the top around a bit before it sets. The tops weigh about 400+ lbs. After setting there is no movement. That was about 3 years ago and they are as stable as the day they were made. The tops are setting on a "T" make from 2 blocks across and one block toward the read. They are all set touching. So far no problems at all. Everyone loves them. Someone on this forum sent me the plans for the shape of the top. Forget who but thanks.....

Donald