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I bought a telescoping flag pole kit from Harbor Freight and am using it for a small anemometer. The kit comes with a piece of schedule 40 PVC pipe that the pole slides into. I'd like to mount this on my roof, re-using some supports from an old satellite dish. I plan to angle cut the pipe to the roof angle but also need some sort of flange that the pipe will actually sit in, then I'll clamp it down to the satellite mounts. Most roof mount flanges I find are pretty piddly and only meant for exhaust ductwork and such. Can someone recommend a flange for roof mounting stuff that's pretty heavy duty?

edit: Photo of the current satellite mount. My idea is for the schedule 40 PVC to go right alongside the main satellite mount, attaching to the roof, and then I'll attach the top of the PVC to the top of the satellite mount so it's attached in two places. enter image description here

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  • If your plan includes cutting the base of the flag pole, note carefully that the second layer tube likely falls into the cut area. Burrs and other protrusions may prevent raising the pole once inserted to the cut area.
    – fred_dot_u
    Oct 1 '20 at 23:56
  • a photo of your existing satellite mount would help.
    – Jasen
    Oct 2 '20 at 0:59
  • I won't cut the base of the flag pole, just the schedule 40 pipe the flag pole slides into. Added a photo. Oct 2 '20 at 3:55
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I'm having a bit of trouble figuring out the terms. It seems that when you write "roof mount flange .. meant for exhaust ductwork" you might be referring to a roof flashing like this: (image from oatey.com)

oatey roof flashing

Those flashings aren't intended to support a pipe at all; they merely keep water out of the roof. I don't think they'd be of any use for mounting your pipe.

When you write of "supports from an old satellite dish" I think of an antenna mount like this one made by Laird: (image from streakwave.com)

Laird UM/L

I can see the foot of that mount working well to anchor the bottom of your mast. I use those alone for mounting small (14 inch diameter) antennas, but for your taller mast, a brace like this one used for satellite dish mounts might be useful: (image from summitsource.com)

DirecTV DTV-AT9-SB brace

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  • I recently installed a similar flag pole, also for mounting a weather station. The instructions require support for the bottom 16" (400 mm). The flange pictured may work by preventing lateral movement of the base. If the sat-dish mounts can provide the necessary rigidity over the entire length of the base PVC, it may work well enough. By using the described dish mount in place of the flange, it's more likely.
    – fred_dot_u
    Oct 1 '20 at 23:55
  • Yes exactly, I already have the last two braces pictured, nicely mounted and I'll attach those to the schedule 40 pipe, I was just hoping to have something the pipe itself could firmly attach to the roof with. Just to give a little more context, the flagpole itself is this one and the bottom portion slides into a chunk of schedule 40 PVC pipe they provide with the kit (and suggest burying in concrete). I'm going to take that piece and rigidly mount it to the roof then slide the flagpole in. Oct 2 '20 at 0:43
  • I added a photo to the original post if that helps. Oct 2 '20 at 3:56
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Consider using PVC glue to attach a male threaded adapter to the pipe. You could fasten the assembly to the roof by threading the male adapter into a floor-flange. To adapt for the roof angle, just glue a 45° elbow near the bottom of the pipe, rotating it until the pipe is vertical (use a level or plumb bob).

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depending on height, I would recommend that you rig 3 guy-wires to the top of the mast to assure stregth vs. wind...

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  • Not a bad idea but the roof isn't a perfect 45 degrees, i think I need something adjustable. Similar to what the satellite mount uses (pictured in @greg-hill 's post above) but that can accept a large diameter schedule 40 PVC pipe. Oct 2 '20 at 0:45
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    You can also use a heat gun to carefully bend PVC pipe to any angle you want... practice first on a scrap piece... Oct 2 '20 at 0:48
  • you can use two 45 degree elbows to make any angle up-to 90 degrees.
    – Jasen
    Oct 2 '20 at 0:57
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Follow up on what I ended up doing, I found some heavy duty brackets at the builder's center and used them in the same fashion as the satellite mount to attach the base of the PVC to the roof, then used hose clamps to tied it into the existing dish mounts. It's solid as a rock! Thanks for the suggestions here folks. Now I realized after putting it up I need a bigger ladder so off to get that before I mount the anemometer.

enter image description here

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  • What did you do, if anything, about waterproofing the penetrations made by the bracket fasteners?
    – Huesmann
    Oct 5 '20 at 15:51
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    I used some rubberized sealant designed specifically for roofing. I put big gobs of it under the brackets and in the lag screw holes. Should be sufficient I think. Oct 5 '20 at 20:12

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