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## Re: [TowerTalk] Sorry to bring up an oldie - Mast Material

 To: Dave Hachadorian , Towertalk reflector Re: [TowerTalk] Sorry to bring up an oldie - Mast Material Rick Scott Wed, 9 Mar 2011 12:09:18 -0800 (PST) mailto:towertalk@contesting.com>
 ```What would that look like for 6061-76 its yield is 40,000 I believe. ----- Original Message ---- > From: Dave Hachadorian > To: Rick Scott ; Towertalk reflector > > Sent: Wed, March 9, 2011 11:31:40 AM > Subject: Re: [TowerTalk] Sorry to bring up an oldie - Mast Material > > Here is a neat mast calculator: > http://www.math.niu.edu/KARC/mast/ > > Plugging in some numbers for 1.5" schedule 20 water pipe: > Safety factor f 2 > Wind loading factor k .004 lb/ft2/mph2 > Maximum stress S 30,000 psi > Outside diameter D 1.9 in > Inside diameter d 1.61 in > Total length of mast 8 ft > Height above support h 4 ft > Antenna 1 height h1 4 ft area a1 6.1 ft2 > Antenna 2 height h2 ft area a2 ft2 > Antenna 3 height h3 ft area a1 ft2 > > Survival velocity: 63.0 mph > Failure velocity: 89.1 mph > Weight of mast: 21.79 lbs > --------------------------------------- > As indicated above, I wouldn't be confident in using Sch 20 water > pipe. That 30,000 psi yield strength for water pipe is hard to > prove, because water pipe is not specified for structural > purposes. Also, the last time I priced water pipe, I was amazed > to see how expensive it had become. > > You are much better off using structural tubing, which has a > specified yield strength. If you go to a metal supplier and ask > for structural tubing, he should be able to quote you some prices > on various strength material. You will probably have to buy a > 20-footer though. Another thing you can do is to order some > galvanized steel mast from Texas Towers. They will sell you a 10' > piece for \$139, and cut off a foot, which makes it UPS-shippable > (at least the last time I did it, in 1978). Their material is > 87,000 psi. Plugging that into the calculator: > --------------------------------------- > > Safety factor f 2 > Wind loading factor k .004 lb/ft2/mph2 > Maximum stress S 87,000 psi > Outside diameter D 2 in > Inside diameter d 1.75 in > Total length of mast 8 ft > Height above support h 4 ft > Antenna 1 height h1 4 ft area a1 6.1 ft2 > > Survival velocity: 107.0 mph > Failure velocity: 151.3 mph > Weight of mast: 20.07 lbs > > That will definitely work. > > > > Dave Hachadorian, K6LL > Yuma, AZ > > > > > > > -----Original Message----- > From: Rick Scott > Sent: Wednesday, March 09, 2011 10:51 AM > To: towertalk@contesting.com > Subject: [TowerTalk] Sorry to bring up an oldie - Mast Material > > Im really confused. Id like to buy Local, because the mail order > houses have > Really high prices and high shipping > plus they only do 5 or 10ft intervals. > > Ive seen all manor material from them from chrome molly to > Aluminum and AES even > has Fiberglass. > > I have a Glen Martin 9ft roof mount tower. Its just shy of 4ft > from the rotor > to the top of the tower. Right now I have > a 2 1/2" Fence Post mast (really heavy wall) that I hold an A4S > up with. > > A4 is going bad so I decided to get my dream antenna the standard > SteppIR 3 > element beam and nothing else will go on the mast. I would > like to get 8ft as that will give me 4ft above the tower, I can > put the antenna > at 2 - 3 feet and be ok. > > > > So I need 2" mast material, > > I would dearly like to buy local and we have a few metal shops > but I need to > know exactly what I have. > > I searched the forum and man there is a lot of material. K7XLC > used to sell > mast but his site doesnt. > > I posted on the local Snohmish County hams and I got a gazzilion > answers. > > One guy swears by Home Depot stuff > One says only buy Sched 40pipe nothing else needed > Another says this and that. > Another says 6061-T6 Extruded Tubing > > > So not really wanting to open a can of worms, whats the best > material to hold > what I plan to put up > for the best cost. > > > Scotty W7PSK > > > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread [TowerTalk] Sorry to bring up an oldie - Mast Material, Rick Scott Re: [TowerTalk] Sorry to bring up an oldie - Mast Material, Dave Hachadorian Re: [TowerTalk] Sorry to bring up an oldie - Mast Material, Rick Scott <= Re: [TowerTalk] Sorry to bring up an oldie - Mast Material, Jim W7RY Re: [TowerTalk] Sorry to bring up an oldie - Mast Material, Dave Hachadorian