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Old 10-20-2019, 11:15 AM   #1
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Is direction a Sensar IV antenna folds for storage critical?

I need to replace the inadequate Rayzar Z1 antenna on my trailer. Would like to replace it with a Winegard Sensar IV.

From what I've read, the Sensar IV needs around 4 feet of unobstructed space on the roof to lay down. That's all the instructions indicate but when I saw an install diagram it showed the antenna lying down with the supports facing the rear of the trailer roof.

Is it a requirement that the antenna lay down with the pivot at the front of the travel direction and the Batwing Element be trailing or can it be reversed with Bat Wing at the front of travel direction (all while lowered of course).


My issue is that if I use the existing hole and cable location, where the Rayzar is mounted it's only a couple feet ahead of the AC unit. No room to lower antenna if it has to go to the rear.. There's at least 6 feet of room ahead of the existing mount.

Does it make a difference which way the antenna is parked on the roof? If so,, why?
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Old 10-20-2019, 12:11 PM   #2
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Mike - no real knowledge on this issue - the concern I would have is wind lift while driving. The plastic gears that hold the antenna are not that strong - have replaced mine once (forgot to lower antenna and brushed a tree branch). No other damage - suspect the gears acted as sacrificial stress relief.
FYI, Jim
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Old 10-20-2019, 12:45 PM   #3
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I have nothing that says for certain that it must fold rearward other than in 40+ years of being around R/Vs, I've never seen one fold forward.

Common sense would say the pivot/hinge should be forward of the heavier mass.
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Old 10-20-2019, 01:28 PM   #4
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I agree with both of you that wind lift might be an issue although it might be mitigated by the fact my antenna would be mounted on the centerline of the roof and when down the head of the antenna would be behind a Maxair vent cover.

In my mind I see air being deflected around a lowered antenna.
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Old 10-20-2019, 03:58 PM   #5
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Titan Mike, Question would be 'On that Razor, is there a hole in ceiling on the inside?'
If not, you could mount Winegard anywhere, and use a cable entry plate where wire comes out roof. Winegard part I believe is CE-2000. Mine is done this way.
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Old 10-20-2019, 04:04 PM   #6
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The only way...

Quote:
Originally Posted by TitanMike View Post
I agree with both of you that wind lift might be an issue although it might be mitigated by the fact my antenna would be mounted on the centerline of the roof and when down the head of the antenna would be behind a Maxair vent cover.

In my mind I see air being deflected around a lowered antenna.
The only way to know is to install it and see what happens...unless you happen to have access to a wind tunnel. Say, aren't you near Boeing? Maybe they will let you use theirs.
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Old 10-20-2019, 04:25 PM   #7
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Originally Posted by boatcat AH6NR View Post
Titan Mike, Question would be 'On that Razor, is there a hole in ceiling on the inside?'
If not, you could mount Winegard anywhere, and use a cable entry plate where wire comes out roof. Winegard part I believe is CE-2000. Mine is done this way.

Yes, there is a hole through the roof for the Rayzor. Really don't want to add a second hole but the plate you referred to is certainly an option should I end up having to go that route.

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The only way to know is to install it and see what happens...unless you happen to have access to a wind tunnel. Say, aren't you near Boeing? Maybe they will let you use theirs.
Funny you should mention. When I graduated from High School I did work for Boeing while I was going to College. College by day, Boeing Swing Shift by night. Guess where I was working-------- The Wind Tunnel.

Couple problems testing my TT there. Their SLOWEST wind tunnel had a test section that wasn't much larger than a VW Microbus. Sure, huge plenum and return chambers but the actual windowed test section was small. My first job there was going around with a vacuum cleaner picking up pieces of test models that had come apart on the test fixture.

Another tunnel tested at speeds up to Mach 6 and it exploded a lot of models.

Two more "tunnels" capable of hypersonic speeds up to mach 22 or so.

All our slow speed testing was done at University of WA Aeonautic's Lab (UWAL) or back at the PWT in Tulahoma, TN. They had a large test section that could start their speed around 40 mph and go well up over Mach 1.

While there I got to work on a couple of models that eventually became known by various names. One a Fighter/Bomber nicknamed "The Pig" or "Aardvark". The other got names like "Challenger", "Discovery" "Atlantis" "Enterprise", and Endeavour".

Wee just knew them by their then classified names as "TFX " and "X-20 Dyna-Soar"

Boeing was competing for a new Fighter in the TFX program but eventually General Dynamics got the TFX contract and the Dyna-Soar design elements were incorporated into the Space Shuttle built by North American Rockwell.



With that great experience I have no idea why I went into the Automotive Industry when I got out of the Army. Guess that's where the job and money was
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Old 10-20-2019, 09:21 PM   #8
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Old times

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Originally Posted by TitanMike View Post
Funny you should mention. When I graduated from High School I did work for Boeing while I was going to College. College by day, Boeing Swing Shift by night. Guess where I was working-------- The Wind Tunnel.

Couple problems testing my TT there. Their SLOWEST wind tunnel had a test section that wasn't much larger than a VW Microbus. Sure, huge plenum and return chambers but the actual windowed test section was small. My first job there was going around with a vacuum cleaner picking up pieces of test models that had come apart on the test fixture.

Another tunnel tested at speeds up to Mach 6 and it exploded a lot of models.

Two more "tunnels" capable of hypersonic speeds up to mach 22 or so.

All our slow speed testing was done at University of WA Aeonautic's Lab (UWAL) or back at the PWT in Tulahoma, TN. They had a large test section that could start their speed around 40 mph and go well up over Mach 1.

While there I got to work on a couple of models that eventually became known by various names. One a Fighter/Bomber nicknamed "The Pig" or "Aardvark". The other got names like "Challenger", "Discovery" "Atlantis" "Enterprise", and Endeavour".

Wee just knew them by their then classified names as "TFX " and "X-20 Dyna-Soar"

Boeing was competing for a new Fighter in the TFX program but eventually General Dynamics got the TFX contract and the Dyna-Soar design elements were incorporated into the Space Shuttle built by North American Rockwell.

With that great experience I have no idea why I went into the Automotive Industry when I got out of the Army. Guess that's where the job and money was
Ah, yes. I was an electronics lab tech for a while working my way through college. Good prep for my 45-year career as an electronics engineer. Unfortunately, I lost the gig about seven months before graduation. The project grant ran out. I spent the last seven months as a cyclotron operator which had no practical experience transfer value.

https://www.linkedin.com/in/lvmarks/
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Old 10-21-2019, 01:35 PM   #9
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Ah, yes. I was an electronics lab tech for a while working my way through college. Good prep for my 45-year career as an electronics engineer. Unfortunately, I lost the gig about seven months before graduation. The project grant ran out. I spent the last seven months as a cyclotron operator which had no practical experience transfer value.

https://www.linkedin.com/in/lvmarks/
Probably more value than a Theramin Player

https://youtu.be/-QgTF8p-284
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Old 10-31-2019, 03:25 PM   #10
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Update - "Wind Tunnel Test" completed.

Quote:
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The only way to know is to install it and see what happens...unless you happen to have access to a wind tunnel. Say, aren't you near Boeing? Maybe they will let you use theirs.
Didn't bother asking Boeing but one day while driving home I had a thought. LEAF BLOWER!

Saw them being used right and left as leaves are falling now and got to thinking how much air they delivered and how fast. Found that the simple electric one (Worx Turbine) I have delivered 320 cfm @60 mph at low setting and high setting was 600 cfm @ 110 MPH. Certainly faster than I will drive with the trailer

Today was a nice day to "Play on the roof" so I climbed up with the my leaf blower on the end of an extension cord. End result was as I kind of expected.

No matter how close I got with the leaf blower at full speed to the antenna, from any direction, base end, antenna end, either side, the antenna did not lift at all. When blowing on the end of nested antenna (which in a normal installation would be the rear and is now front) the most movement was when the end of the antenna element "fluttered". But then again when blowing from the other end the air turbulence caused about the same "flutter" and bear in mind, air speed for this test is around 100 mph. Also, no matter where I directed the air or how close, the center "box" of the antenna refused to lift off the roof at all.

Based on this what i suspected was confirmed. Winegard's "Engineers", while sitting at the drawing board thought the wind would lift the antenna and according to an e-mail I received from them "Tear The Antenna From The Roof".

My real world test doesn't bear this out at all so my conclusion is, mount the antenna any way you need and don't sweat it. Just because nobody else has ever done it doesn't mean it's not possible. BTW, that's the answer I got when I called Winegard and asked directly. Their customer service person said "We've never heard of that".

For those new to the discussion, I needed to install my Sensar IV in the reverse nesting position because when I removed the Rayzr Z1 I didn't want to create a second hole in the roof. Not enough room to lower antenna if I used the same hole and followed what I now believe to be "tradition", lowering the antenna to the rear, because of proximity to the A/C unit.

I have a video I took with my phone of the "Wind Tunnel Test" and if I can figure out how to post it from my phone I'll post it here for anyone interested in seeing it.

Here it is via YouTube:



Lastly, there is a Max Air vent cover just ahead of the antenna that doesn't show in the video. It creates a wind shadow that when I held the leaf blower in front of it, pointing back, decreased the flutter almost nothing, again a reminder, this is at 110 Mph air speed from the blower.
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