Help needed now!! Attaching a large Sat dish to roof

M

marcus mcgee

New member
Sep 29, 1997
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I am about to put this monster Sat dish up today. I know where the main
rafter is and I am putting it between the two AC units on the 5th
rafter. It is large(4ft) and a great sail to catch the wind even when
it down and flat against the roof. Because of the size I have to mount
it at an angle. I can get 3 bolts into the rafter and am looking for
suggestions as to what to mount it with. The interioir is finished with
1/4 plywood covered with a wall carpet. Any suggestions for the type of
toggle or blind nut to use? Should I cut an access hole in the ceiling
and put lock nuts and add an interior brace? HELP!!

I do not need this thing coming of at 75 MPH. That could ruin a persons
day. If you have suggestions call me at 800-775-2537. I will be here
all weekend during the day until 5.

Marcus
 
>
> I am about to put this monster Sat dish up today. I know where the main
> rafter is and I am putting it between the two AC units on the 5th
> rafter. It is large(4ft) and a great sail to catch the wind even when
> it down and flat against the roof. Because of the size I have to mount
> it at an angle. I can get 3 bolts into the rafter and am looking for
> suggestions as to what to mount it with. The interioir is finished with
> 1/4 plywood covered with a wall carpet. Any suggestions for the type of
> toggle or blind nut to use? Should I cut an access hole in the ceiling
> and put lock nuts and add an interior brace? HELP!!
>
> I do not need this thing coming of at 75 MPH. That could ruin a persons
> day. If you have suggestions call me at 800-775-2537. I will be here
> all weekend during the day until 5.

Marcus,

About the only way I would be comfortable with this would be to mount a
piece of 6061-T6 channel as a purlin between the two rafters. Easier
said than done as you will need to figure a way to transfer the load to
the rafters. You should be able to find the aluminum at any good metals
distributor or an aircraft supply house. If you don't think you'll have
to take it back down, you use a nylock stop nut on it or make an access
door. To avoid the access door, you could use rivnuts or nutserts on
the aluminum.

No way would I want to just attach it to the skin, even with some sort
of backing plate.

Patrick
- --
Patrick Flowers
Mailto:patri63

The GMC Motorhome Page
http://www.gmcmotorhome.com
 
>

> >
> > I am about to put this monster Sat dish up today...
> > I do not need this thing coming of at 75 MPH...
>
> Marcus,
> I'm of no help on the proper mounting, but if some of the flyboys here
> know how to calculate the wind forces, You can easily see Your mounting
> concerns are more than legitimate.
> The thought that came to me was the use of a wind deflector something
> like You see on some of the big rigs, in addition to, NOT in lieu of
> proper mounting.
> Good luck
> Tim
> > day. If you have suggestions call me at 800-775-2537. I will be here
> > all weekend during the day until 5.
> >
> > Marcus
Good Idea, but if I do the deflector the coach will not fit into my
warehouse door. I am looking at a cable attachment for the dish part to
secure it to the 5th and 6th rafter at the dish top and sides. I think
this should do it. I am supposing that it will spread the load out as
with the dish down the base mounting plate is out to the drivers side
and the wind lift has a multiple effect because of the leverage. If I
hold down the top of the dish also then I believe the lift will be
spread out more evenly. Just a guess on my part. Wish I had the dish
rig before I redid the interior cieling. If I arrive at the fall
convention without a roof and dish you will all know I was wrong.

Marcus
 
>
> I am about to put this monster Sat dish up today...
> I do not need this thing coming of at 75 MPH...

Marcus,
I'm of no help on the proper mounting, but if some of the flyboys here
know how to calculate the wind forces, You can easily see Your mounting
concerns are more than legitimate.
The thought that came to me was the use of a wind deflector something
like You see on some of the big rigs, in addition to, NOT in lieu of
proper mounting.
Good luck
Tim
> day. If you have suggestions call me at 800-775-2537. I will be here
> all weekend during the day until 5.
>
> Marcus
 
Can give you some advice from long experience in the satallite business.
Everyone I know is going to Direct TV, in their home and than when they are
on the road using an extra receiver and antenna on a tripod, with the same
authorization. They are so easy to set up and tune, and in my opinion the
only way to go.

Mounting an antenna that large on the roof is only asking for trouble both
from a standpoint of wind resistance and maintenace. The GMC was never
designed to take that kind of wind load.

>I am about to put this monster Sat dish up today. I know where the main
>rafter is and I am putting it between the two AC units on the 5th
>rafter. It is large(4ft) and a great sail to catch the wind even when
>it down and flat against the roof. Because of the size I have to mount
>it at an angle. I can get 3 bolts into the rafter and am looking for
>suggestions as to what to mount it with. The interioir is finished with
>1/4 plywood covered with a wall carpet. Any suggestions for the type of
>toggle or blind nut to use? Should I cut an access hole in the ceiling
>and put lock nuts and add an interior brace? HELP!!
>
>I do not need this thing coming of at 75 MPH. That could ruin a persons
>day. If you have suggestions call me at 800-775-2537. I will be here
>all weekend during the day until 5.
>
>Marcus
>
>
 
>.... If I arrive at the fall convention without a roof and dish you >will all know I was wrong.
> Marcus

Thanks for the mention of the fall convention. Reasons for me to work it
into my schedule are mounting almost daily. It will be my first. I want
to see projects like Your dish and meet some of the people who share so
much valuable information here.
For me this forum is a real trip without ever leaving the farm!
Have fun, Tim
 
WHAP!(hand slapping forehead)

Marcus,

Referring back to my first suggestion to use a "purlin" to spread the
load between the two rafters. Why not mount a pair of purlins on top of
the roof between the rafters and mount the dish to them? I'm no
structural engineer, but 3/4" square .035" 4130 or .125" 6061-T6 should
suffice. Shoot, if you could find square 304 stainless tubing, that
would probably work, and be maintenance free :)

Patrick
- --
Patrick Flowers
Mailto:patri63

The GMC Motorhome Page
http://www.gmcmotorhome.com
 
I understand your concern, but I have to do it to make this work as a
demo vehicle. I just finished, and I have three bolts into the main
cross member, and have put a steel plate perpendicular to the Z shaped
stringers. Bolted the thing together and it seems very sturdy. The
reinforing plate sandwiches two of the parallel rafters. The top of the
dish is held down with two tie downs to eyebolts in the 5th and 6th
cross rafter.
If this comes off the whole roof is going, but it should not be too bad.
I may add a wind defelector in front of it if it needs it. We are
downloading a digital signal on th C-band and need the larger dish for
data reception in severe storms.



>
> Can give you some advice from long experience in the satallite business.
> Everyone I know is going to Direct TV, in their home and than when they are
> on the road using an extra receiver and antenna on a tripod, with the same
> authorization. They are so easy to set up and tune, and in my opinion the
> only way to go.
>
> Mounting an antenna that large on the roof is only asking for trouble both
> from a standpoint of wind resistance and maintenace. The GMC was never
> designed to take that kind of wind load.
>

> >I am about to put this monster Sat dish up today. I know where the main
> >rafter is and I am putting it between the two AC units on the 5th
> >rafter. It is large(4ft) and a great sail to catch the wind even when
> >it down and flat against the roof. Because of the size I have to mount
> >it at an angle. I can get 3 bolts into the rafter and am looking for
> >suggestions as to what to mount it with. The interioir is finished with
> >1/4 plywood covered with a wall carpet. Any suggestions for the type of
> >toggle or blind nut to use? Should I cut an access hole in the ceiling
> >and put lock nuts and add an interior brace? HELP!!
> >
> >I do not need this thing coming of at 75 MPH. That could ruin a persons
> >day. If you have suggestions call me at 800-775-2537. I will be here
> >all weekend during the day until 5.
> >
> >Marcus
> >
> >
 
>
> WHAP!(hand slapping forehead)
>
> Marcus,
>
> Referring back to my first suggestion to use a "purlin" to spread the
> load between the two rafters. Why not mount a pair of purlins on top of
> the roof between the rafters and mount the dish to them? I'm no
> structural engineer, but 3/4" square .035" 4130 or .125" 6061-T6 should
> suffice. Shoot, if you could find square 304 stainless tubing, that
> would probably work, and be maintenance free :)
>
> Patrick
> --
> Patrick Flowers
> Mailto:patri63
>
> The GMC Motorhome Page
> http://www.gmcmotorhome.com

I would love to do it that way but I have a height restriction into my
warehouse. The AC unit clear by about 1 inch with the coach lowered all
the way. The dish is only 1/2 inc shorter than the AC units. See the
previus post as to how I did it.

Marcus
 
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