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[Towertalk] Obssessive-compulsive Anal Paranoid Builds Over-engineered R

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Subject: [Towertalk] Obssessive-compulsive Anal Paranoid Builds Over-engineered Roof-top Guy Anchors
From: stevek@jmr.com (Steve Katz)
Date: Thu, 21 Nov 2002 13:34:59 -0800
Wow, what a writeup.

I guess my only question would be, "Why are you using LMR400?"  Are you,
ummm, going to rotate that stuff?

>From the "been there, done that school of hard knocks:" I wouldn't.

-WB2WIK/6

"If everything seems under control, you're just not going fast enough." -
Mario Andretti

> -----Original Message-----
> From: Jim Smith [SMTP:jimsmith@shaw.ca]
> Sent: Thursday, November 21, 2002 12:10 PM
> To:   towertalk@contesting.com
> Subject:      [Towertalk] Obssessive-compulsive Anal Paranoid Builds
> Over-engineered Roof-top Guy Anchors
> 
> I often see suggestions on TT that hams typically over-engineer their 
> antenna support installations.  Fifty years ago I heard the definitive 
> definition of engineer.  It goes as follows, "An Engineer is someone who 
> can do for 50 cents what any damn fool can do for a dollar."
> 
> I've been working on improving my modest antenna installation in an 
> attempt to break free of that 1,000-Qs-in-a-contest barrier.  The plan 
> is to increase the self-supported Rohn 25 height from 25 ft to 30 ft off 
> the flat, 2nd story, roof, swap out the old TH3 for a C4-SXL, get rid of 
> the 40m dipole, mount an old Hy-Gain 6 & 2m beam above the C4, swap out 
> the old Ham-M for an Alfa-SPID and mount it near the bottom of the tower 
> where I can get at it easily, add steadying guys to the Rohn to 
> accomodate the increased wind load, swap out the 30 yr old RG8 runs with 
> 9 runs of LMR-400 (there are a few spares here), mount an aluminum plate 
> with terminal blocks for rotor or other control cables and 9 barrel 
> connectors (where the coax comes out of the conduit at roof level) to 
> which the LMR-400 runs will be connected (to make it quicker to 
> troubleshoot swr problems in the middle of a contest) and mount a 
> similar aluminum plate in the shack wall to terminate the other ends of 
> the LMR-400 and control cables.
> 
> Why add 5 ft to the tower?  Because I have a 5 ft chunk of Rohn 25 lying 
> on the roof.  Why bother?  Because, at this rather low height, I expect 
> to pick up 1 dB or so at low angles.  Who cares about 1 dB when a 3 dB 
> difference is barely perceptible?  Think threshold.  Statistically, if 
> you're below it, no Q.  If you're above it, Q.  2 dB is, of course, 
> better.  I hope to get at least that additional dB out of the C4 (and, 
> of course, a lot more on 40).
> 
> Got the C4, got the Alfa-SPID, got the Phillystran and grips, got the 
> 1000 ft of LMR-400, got a 4' by 4' sheet of 1/16" aluminum for the coax 
> termination plates (with a lot left over . . . always wanted my own 
> sheet of aluminum) and got a 12 ft length of 1/4" x 2" aluminum bar to 
> make the guy anchor station at the top of the Rohn (only need 7 ft but 
> now a bending error won't kill me).  Haven't sorted out what I need for 
> a mast yet.
> 
> OK, the Philly is rated at 2100 lbs.  So I need turnbuckles, guy 
> attachment points, etc. rated for at least 2100 lbs if I want to match 
> the Philly strength.  I do want to be able to tell the neighbours that 
> the system is designed such that the weakest point has a very large 
> safety factor (these are steadying guys, remember) so I want the Philly 
> to be the weakest link.  The plan is to attach the guys to the 4 corners 
> of the house.  (A 3 point guy anchor system would make one of the 
> anchors rather close to the tower.)  The house has a flat roof covered 
> in vinyl, i.e. a deck.  
> 
> 
> Sales Pitch For Flat Roof Follows
> 
> Next house you buy (with due regard to snow loading), get a flat roof 
> one, get rid of the tar and gravel, put vinyl on it and punch a 
> stairwell through the roof with suitable enclosure and door.  You'll 
> probaly have to beef up the joists as the roof rating will now need to 
> be for a live load as opposed to a dead one (people dancing as opposed 
> to snow lying on it).  You will have to add a railing for safety 
> (non-conductive unless you can work out a "stealth" design for it . . 
> hmmm... some kind of Moxon, maybe).  Great for antenna stuff.  Sell to 
> the XYL by saying it's great for entertainment (which it is).  Buy a 
> fancy patio table, chairs and umbrella, a small barbecue with 10 lb tank 
> and a Rubbermaid storage shed to store the umbrella, barbecue and tank 
> and put it all on the roof.  An elevator would be nice (but I wasn't 
> able to sell that part).  So, you're assembling your latest experimental 
> yagi on the roof and it gets dark and tomorrow you're flying to 
> Dusseldorf on a 2 week business trip.  No problem.  You just leave 
> everything where it lies, close the door and walk downstairs.  Nobody 
> runs over it with the lawnmower.  The kids don't use the elements for 
> pole vaulting (you did lock the door to the roof, didn't you?).  Nobody 
> complains that it is unsightly.  When you come back you just pick up 
> where you left off.  In other words, what you get by doing this is an 
> extra floor of the house that is entirely yours to do with what you will 
> except that it has to be tidy for social occasions, and then only in the 
> summer.
> 
> 
> Back to Antennas
> 
> In my case, the added railing to keep folks from walking over the edge 
> consists of standard 2x4 framing which was installed on top of the 
> existing 6" or so high parapet wall and covered with 3/4" plywood which, 
> in turn, was covered with 10" bevelled cedar siding on the inside and 
> cedar shingles on the outside to match those on the existing Mansard 
> roof.  When standing on the roof it looks like a normal outside wall 
> covered in cedar siding except that, being a railing, it is only 42" 
> high.  So, when I screw the eye bolt into a corner of this railing for 
> the bottom end of a guy, what's really holding it, a bit of cedar and 
> some, perhaps rotting, plywood and 2x4?  Off comes the siding.  Off 
> comes the plywood.  No rot and I now know how the corners are framed.  
> 
> I decide that I don't want to screw an eye bolt into the corner as:
> 
> 1.  the guy will terminate only 3 ft or so above the deck surface.  
> Remember the summer time social occasions?  Can you football enthusiasts 
> spell "clothesline"?  
> 
> 2.  I don't like the risk involved in depending on one threaded eye bolt 
> in wood to carry an expensive load for a lot of years (expensive to put 
> up - more expensive to pull out of the neighbour's roof if it comes 
> down).  Here, in the rain forest, stuff rots where you can't see it.
> 
> I decide that I want the guys to terminate about 5 ft above the deck 
> surface.  I now visualize a length of 1-1/4" square tubing fastened to 
> the corner with lag bolts.  Near the top of the tubing is an an eye bolt 
> about 5 ft off the deck to which the guy is fastened.  (I know, I still 
> have bolts screwed into wood but now there are several of them and, if 
> one starts pulling out because of rot or whatever, it won't be 
> catastrophic and it will be obvious with casual inspection.)
> 
> There is a problem with this as there is a sheet metal cap covering the 
> top of the railing which projects out from the corner an inch or so and 
> would interfere with the tubing.  (I know, it's conductive, but it was 
> all done before I got back into ham radio.  Maybe I could cut it into 11 
> ft lengths and separate them with insulators.  Maybe I could replace the 
> whole thing with the plastic equivalent and accept the UV deterioration 
> problem.)  There is also a strip of flashing sticking out 2" about half 
> way up the wall which keeps rain out of a ventilation strip which runs 
> around the whole perimeter of the railing.  One could cut the cap and 
> flashing to accomodate the square tubing but, if it is wanted to restore 
> things to how they were, the cap would probably have to be replaced 
> around the entire perimeter of the house.  The flashing would be less of 
> a problem but would still involve removing and reinstalling a bunch of 
> siding.  Looking forward (well, ahead is probably the better term) to 
> declining years, I devised a method of supporting the steel tubing away 
> from the corner such that it can all be removed and made to look good 
> with only about a half day's labour.  
> 
> The solution was to, at each corner, attach 2 lengths of 4x4 to the 
> wall.  One length fits in the space between the flashing and the cap.  
> The other fits in the space between the flashing and the deck surface, 
> stopping a couple of inches short of the deck.  A 1-1/4 x 1-1/4" piece 
> of each 4x4 is cut out at the corner to accomodate the steel tubing.  
> So, once installed, the steel tubing is spaced 2-1/4" (3-1/2" minus 
> 1-1/4") out from the walls, providing clearance for the cap and 
> flashing.  In the future, the tubing and 4x4s can be easily removed and 
> the exposed space covered with strips of wood.  In what follows, I will 
> refer to these 4x4s as "guy anchor support blocks".
> 
> The question now becomes, "How do I fasten these chunks of 4x4 to the 
> corner framing?"  The answer involved many lag bolts and many CAD 
> drawings and much looking at Crosby 3/8" and 1/2" eye bolts, shackles 
> and turnbuckles along with lagging and gluing many pieces of wood into 
> the existing corner framing.  The carpenter I hired to do the work drily 
> suggested that the 40 lag bolts per corner in my original design might 
> be too much weight for the building to sustain so I managed to cut it 
> down to 28.  Friends suggested that lag bolts need a certain amount of 
> wood around them to function properly - some even making oblique 
> references to swiss cheese.
> 
> In what follows, I'm going to talk about the south-east corner as I 
> think it will make things clearer (but nowhere near as clear as a couple 
> of photos).
> 
> So, the original corner framing consists of 3 2x4 studs arranged to 
> provide something to nail to at both the inside and outside corners.  
> This particular corner style has a 3-1/2" x 1-15/16" gap in it where 
> there is no wood.  We filled this gap by cutting a 2x4 stud the 
> appropriate height and screwed (6 screws) and glued a piece of 3-1/2 x 
> 3/8" plywood of the same height to it.  This exactly filled the empty 
> space.  A plan view of the corner now looks like the corner is made of a 
> 5-1/16" x 5-1/16" piece of wood with a 1-9/16 x 1/91/16" piece taken out 
> of one (NW) corner (the aforementioned inside corner nailing area).  
> When we put the gap filler in we put construction adhesive on all hidden 
> surfaces, slid it into place and fastened it with 6 long screws through 
> the existing corner framing.  We then cut some 3-1/2" x 5/4" material 
> and a 4x4 to the appropriate length.  We covered all the hidden surfaces 
> of the 5/4 and 4x4 with construction adhesive, placed the 5/4 against 
> the north face of the corner, placed the 4x4 against it and fastened 
> them to the corner framing with 6 3/8" lag bolts.  In this way, we have 
> extended the corner framing nailing area inside the east wall by 4-1/2" 
> (3-1/2" plus 1").  Now we have something to which we can secure the guy 
> anchor support blocks.  We did the same to the west face of the corner 
> to extend the corner framing nailing area inside the south wall by the 
> same amount.  (If you haven't been counting, we're up to 12 lag bolts.)  
> All of this was somewhat complicated by the need to accomodate the 120V 
> ac wiring running through the corner for the deck outlets and lighting.  
> We also ran 8 3/8" lag bolts through the bottom 2x4s of the new railing 
> framing into the top 2x4s of the original parapet wall to accomodate 
> vertical forces, 4 on the east side and 4 on the south side.  (20 lag 
> bolts and counting.)  This was all repeated at the other 3 corners.
> 
> 3/4" plywood goes back on and is covered with building paper.  Awright, 
> we got stiff corners now.  Don't have the 1-1/4" steel tubing yet so 
> made some 4' lengths of 1-1/4 x 1-1/4" wood to simulate the steel 
> tubing.  Painted them with aluminum paint so neighbours would think they 
> are galvanized steel.  Wouldn't want them to remember the wood and 
> subsequently think, "He's got that huge thing up there supported by 4 
> flimsy wooden sticks."  There are 8 3/8" lag bolts securing the (now 
> wood, later steel) guy anchors and their supports to the 4x4 extensions 
> to the corner framing nailing area.  Could have used fewer had there 
> been one guy anchor support block per corner instead of two.  For each 
> of the two support blocks in the SE corner there are 2 lag bolts through 
> the steel tubing and support block into the east wall 4x4 and 2 into the 
> south wall 4x4.  (Brings total lag bolts per corner to 28)
> 
> Earlier I mentioned CAD drawings.  Why wouldn't sketches do?  In a 
> vertical distance of 42" we have 20 3/8" lag bolts plus the 12 screws 
> for the 2x4 plus 3/8" plywood filler plus another 12 screws I haven't 
> talked about because it would have turned an already murky description 
> into impenetrable mud.  An obvious requirement was that none of these 
> screws/bolts could be allowed to interfere with any other.  Thanks to 
> CAD, they don't.
> 
> Next the siding goes on, cut back a little to butt up against the 
> support blocks.
> 
> The other night I dreamt that a huge tornado had ripped the roof right 
> off the house.  When last seen the roof and railing were sailing through 
> the air with tower proudly vertical and guys still attached.  The 
> LMR-400 was getting pretty thin, though.
> 
> Hope this was of some interest.
> 
> 73 de Jim Smith    VE7FO
> 
> 
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