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Dark Matter Observatory Construction log

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#26 nimitz69

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Posted 28 July 2019 - 06:45 PM

after lunch I decided to try and at least get the forms done for both the pier hole & slab so that I could pour concrete the next day.  That went much smoother and i closed out Saturday with the forms completed

 

pier and slab footings.jpg



#27 nimitz69

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Posted 28 July 2019 - 06:53 PM

This morning I headed out early to HD to rent a cement mixer as I planned to do both pours.  I checked the pier hole and it still had about 1" of standing water and while thinking about it on the way to HD I decided discretion is the better part of valor & i needed to think about a few things before jumping in and just doing the pour.  I know concrete will harden just fine in standing water but the hole is currently only 3' vice the 5' I had planned & i wasn't sure because of the ground water should I be widening the hole or something different.  So I just bought 10 bags of concrete & planned to do the slab only today.

 

Decided to not get a mixer since it was 'only' 10 bags .... my 2nd bad idea & I won't be making that mistake for the pier pour.  87 degs, 70% humidity & 2 days from turning 60 and  well, I should have rented the mixer .... lol.

 

Although painful, I did mange to complete the slab so at least half the concrete work is now done.  Once I figure out the new cunning plan for the pier pour I'll plan to pour the pier on Sunday.  At that point I'll be done with stuff I've never done before and on to stuff I've done a number of times ...

slab pour.jpg


Edited by nimitz69, 28 July 2019 - 06:57 PM.

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#28 OldManSky

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Posted 29 July 2019 - 09:35 AM

Been following your progress...looking good!

And being a few months from turning 60, I can relate to your mixer issue...the thing is, we don't *feel* old, but gosh darnit we just can't work like we could 10 years ago!  Rent the mixer next time :)


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#29 nimitz69

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Posted 29 July 2019 - 12:55 PM

yeah, you get lulled into it.  I'm still very active with my competitive shooting 5x/week, tennis 2x/week & working out 3x/week but I'm not cut out to work out in the heat doing hard labor any more ...

 

luckily as long as I'm done before fall/winter imaging season I'm good so I have lots of time .... and I can always just take off from work if I feel the need to ... :)



#30 nimitz69

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Posted 01 August 2019 - 10:27 AM

 So in order to be able to pour my pier On Sunday I need To take off tomorrow and do the prep work since I have a match on  Saturday.

 

Several things need to be done: remove the forms on my slab; level the pier base form; build the pier plumb holders; mark true north on the form tube to be able to line up the bolts which will Be embedded in the concrete.  I’ve devised what I think will be a workable methodology for marking true north & i’ll post the process tomorrow after constructing & executing it to Ensure it works



#31 nimitz69

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Posted 02 August 2019 - 02:09 PM

Ok, in spite of the rain today I managed to get everything completed so I can pour the pier on Sunday:

- removed slab forms

- releveled pier form

- built pier stability forms for top & bottom

- cut rebar to final size

- determined & marked true north

 

here's what things looked like when I was done

 

pad and pier.jpg


Edited by nimitz69, 02 August 2019 - 02:21 PM.

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#32 nimitz69

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Posted 02 August 2019 - 02:11 PM

this is a closeup showing the marking on the 2 forms so once true north is marked on the tube I can recenter everything when I'm ready to pour

 

pier forms.jpg

 

I also tack glued the 3 forms together so they will be less likely to move over the next day & a half


Edited by nimitz69, 02 August 2019 - 02:12 PM.


#33 nimitz69

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Posted 02 August 2019 - 02:19 PM

given the overcast skies I just decided to go with using a compass and marking the tube where true north is. the mag variation at my house is -6 deg (west) so I set the compass to point north (mag north) and then adjusted it so that the line on the board ran through the 174 deg mark on the compass which put me on true north. I couldn't see where 354 deg was due to marks on the glass so i just used the opposite side.

 

If this is not right, someone please speak up ....

 

compass.jpg

 

The sonatube is marked against the 2x4 forms as well so I can precisely return it to its exact position it was in when I scribed true north on it

 

So with that I should be ready to pour concrete Sunday ...



#34 dmdouglass

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Posted 02 August 2019 - 03:54 PM

given the overcast skies I just decided to go with using a compass and marking the tube where true north is. the mag variation at my house is -6 deg (west) so I set the compass to point north (mag north) and then adjusted it so that the line on the board ran through the 174 deg mark on the compass which put me on true north. I couldn't see where 354 deg was due to marks on the glass so i just used the opposite side.

 

If this is not right, someone please speak up ....

 

attachicon.gif compass.jpg

 

The sonatube is marked against the 2x4 forms as well so I can precisely return it to its exact position it was in when I scribed true north on it

 

So with that I should be ready to pour concrete Sunday ...

You got me thinking....

Hmmmmm.    So i did a little "quick looking", and you seem to be right on the money....

 

True N.png

 

Hope the "pour" goes well !!


Edited by dmdouglass, 02 August 2019 - 03:57 PM.


#35 nimitz69

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Posted 03 August 2019 - 11:57 AM

Thx!!!  I know the -6 deg was correct, just needed to be sure I was moving in the right direction.  With a mag variation of -6 that means true should to the ‘right’ of mag north when looking north ... which would mean a Line through 354 deg and 174 degs ..



#36 dmdouglass

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Posted 03 August 2019 - 01:45 PM

Ummmmm.....

When is the pour ??    I think Sunday (and this is Saturday).

 

I think we are agreeing on everything...

EXCEPT the last.

In your case (Florida -- I think.... (Cocoa Beach))...

True N is to "right" (EAST) of Magnetic North...

Thus, you should be looking at a line with +6 Degrees Magnetic  (or 186).

 

I have NOT validated the "6" figure yet. Will work on that now.

 

Can someone else chime in here and verify for us ??



#37 dmdouglass

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Posted 03 August 2019 - 02:19 PM

Well, everything i see for Cocoa Beach, FL is in the area of 6.9 Degrees.

 

AND.... i guess the final "method" depends on how you are using your compass to create the line, such as adjusting the dial, or leaving the dial with the needle pointing "N".

 

The actual "reference" though, should agree with the map i posted a few posts up (#34).

 

AND... as shown at the bottom right, True North will be to the right of Magnetic North as you are facing North.



#38 dmdouglass

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Posted 03 August 2019 - 03:25 PM

I have been re-reading your thread. I see that you can definitely "see" Polaris from this location.

Thus.... the absolute solution is available.

 

You said you were going to setup a "marker" and "scribe" point.  

With that done, hopefully you can go out tonight, and do a "sighting".

If you can, you have it made !!

 

Either the line-up will go "right on"... or it will be about 12 degrees off.

Hopefully you can verify it all tonight.



#39 nimitz69

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Posted 03 August 2019 - 04:10 PM

unfortunately its completely overcast here and will continue to be for quite some time but you are correct, true north is showing 6' 52" and I agree it is 'to the right' of mag north which means  a line that is 006 degs & 186 degs on the compass.  

 

After moving the 6 degs I was using where the needle was pointed which of course is still mag north ... duh ... thx for the correction.  Guess I know what I'll be doing in the morning before starting the pour .....

 

why couldn't I live in the panhandle where its zero deg .... dalek12.gif



#40 nimitz69

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Posted 03 August 2019 - 04:16 PM

I know people say not to use your cell phone compass but if you set it ti 'use true north' isn't it using GPS to determine location and therefore should be plenty accurate?



#41 dmdouglass

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Posted 03 August 2019 - 04:23 PM

I know people say not to use your cell phone compass but if you set it ti 'use true north' isn't it using GPS to determine location and therefore should be plenty accurate?

Reasonably so.....

But it sort of DOES require some movement that can be recognized to be "right on"....

At least, that is my experience.



#42 nimitz69

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Posted 03 August 2019 - 04:30 PM

isn't that why it has you rotate the compass through 360 degrees when to select true north?  I guess the question is , how far off is it without any motion?



#43 kathyastro

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Posted 03 August 2019 - 05:03 PM



I know people say not to use your cell phone compass but if you set it ti 'use true north' isn't it using GPS to determine location and therefore should be plenty accurate?

GPS knows position, not direction.  GPS units that show compass directions typically have a magnetic sensor built-in.   But it senses magnetic north, not true north.  It needs a table to look up your location and return the magnetic variation, so it is no more accurate than a regular magnetic compass. 

 

The only accurate way to measure north with a GPS is to walk in the direction you believe to be north and see how your moving position compares to your starting position.


Edited by kathyastro, 03 August 2019 - 05:03 PM.

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#44 nimitz69

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Posted 04 August 2019 - 06:07 PM

start ....

pier start.jpg

 


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#45 nimitz69

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Posted 04 August 2019 - 06:14 PM

finish ...

 

pier finished.jpg

 

started the day redoing true north location and got everything ready & took a break for lunch. returning from lunch it started to rain (of course) so I broke out my 10' x 10' EZ-Up tent from when I used to do arts & crafts shows & pressed on.

 

pier is level & the 4 bolts sunk into the concrete are centered on true north.  This weekend I'll layout the 8 footings & start construction of the deck floor.  Once the deck floor is complete I'll probably pour concrete around each pre-fab concrete footing just to be sure.  At that point I'll need to take  a break to do some wall design work to determine exactly how high the walls will be.


Edited by nimitz69, 04 August 2019 - 06:17 PM.

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#46 dmdouglass

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Posted 06 August 2019 - 06:26 PM

Anxious to hear an update...
Have you had a clear evening yet where you can look over the pier, and line up Polaris with the mark?



#47 nimitz69

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Posted 06 August 2019 - 07:58 PM

The pier isn’t even dry yet ... lol but No, and there is no end in sight.  Once the floor is done I’ll look for a night to try out the pier mount and check PA. For now it’s full speed ahead since there is  nothing that can be done about the pier ....dalek12.gif  


Edited by nimitz69, 06 August 2019 - 08:01 PM.


#48 N3p

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Posted 07 August 2019 - 07:57 PM

Nice work there nimitz69.

 

That's an important pile of concrete bags, just by looking at them, my back got stiff. This is real work wink.gif

 

RumxF07.jpg?1



#49 nimitz69

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Posted 07 August 2019 - 08:17 PM

Thx!    Particularly since I needed to add another 10 bags to finish the pour!  With the square footing about 1/2 full I only had 2 bags left so luckily my wife was  able to go to Lowes & buy 10 more bags - actually completed the pout with 1/2 bag left.  The hole was somewhat bigger than I originally calculated  I think ....

 

and a mixer does nothing to lighten the weight of 50lb bags ... one more thing added to the list of things that I’ll only do once .... (removing wall paper, hanging wallpaper and building a brick paver patio in Albuquerque)


Edited by nimitz69, 07 August 2019 - 08:18 PM.


#50 nimitz69

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Posted 09 August 2019 - 05:54 PM

so now I'm a machinist ...

pier plate cut.jpg

 




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