Community Forums

pago cruiser · 08-15-2021, 11:24 PM

Did a search and was surprised to fin no similar questions - or even concerns.
Just bought a DISH Playmaker - 16" diameter by 13" high.

Am discovering that the best place for it is up near the front on a 2008 Winnebago Aspect 26A.

I have just finished swapping out (2) original fans and adding a 3rd MAXX Fan; meaning I have discovered that the roof is about 1/16" fiberglass over 1/8" "plywood". It is adhered pretty well to 4" polystyrene looking foam, with another 1/8" plywood on the bottom (ceiling) , with some frizzy material almost like a real short carpet. It is pretty strong to walk on - no soft spot or spongy areas.

But for securing stuff with screws - like the MAXX Fan perimeter - or the "roof top mounts" of the DISH antenna - it does not impart a feeling of...robustness. To the contrary; coming from a lifetime around cruising sailboats, this would have been 3/4" marine grade ply.

Of the 16 screws on each of the MAXX Fans, 2 screws failed to grip whatsoever; like there was a void in the plywood. No BIG problem... I guess, as the 2 original fans were installed by Winnebago without ANY screws - just silicon based sealant/adhesive.

But for the DISH thing; the height of 13" will be just a couple feet back from the leading edge of the roof line. Meaning that at 70-75MPH, plus say a 20 mph headwind, and I've got close to 100 mph trying to blow this this off and sending it to Kansas...

So... the OCD in me is thinking about a 1/2" thick fiberglass panel - 18" x 18" (about $60 on ebay), which would then be silicon based sealed/adhered to the roof, with perimeter #10 screws at about 4-5" on center. I thought about (4) maybe 6" x 6" pads, but (assuming your "goop" is good) adhesion strength is primarily a function of surface area. with an 18" x 18" bonding area, I don't think a human could rip it off. The mounts for the DISH would then be through-bolted to the 1/2" fiberglass, with recesses in the original roof deck to sink the nuts below the roof surface.

I also thought about using 1/8" stainless with welded nuts on the bottom; but here in AZ I would be concerned about the 150F metal temps (sitting in the summer sun) possibly overheating the DISH antenna.

Comments?

moisheh · 08-16-2021, 07:04 AM

Did you get the rk4000 mounting kit?

pago cruiser · 08-16-2021, 09:21 AM

Yes; have the mounting kit. All it does is provide (2) screw holes offset about 3" for each of the DISH (4) mounting screws. They look to be of pot-metal, or a low grade aluminum casting. While the doubling of the screw holes is a good idea... it does not change the fact that each #8 screw has less than 2 threads engaged with the roofing. Not confidence inspiring.

As I think about it, I guess they are counting on the appx 4 sq inches of bonding area between the roof deck and the base of the (new) roof mount. If you used something like 3M 5200 as an adhesive, I would think the bond between the aluminum roof mount and the Winnebago 1/16" fiberglass roof would be superb. Not so sure of the bond between the 1/16" fiberglass and the 1/8" plywood, or the plywood to the foam... This is what is leading me to a large surface area mechanical (screws) + adhesion (goop) solution.

Interestingly enough, the (4) 1/4-20 (I think) bolts that they provide look to be mild steel - not galvanized, not stainless. Meaning that unless they are are just covered in goop, they (soon) will be adding orange rust stains to the roof deck.

As an absolute minimum, these need to be changed to 304 SS. About 50 cents each...not a big deal, but surely the profit margin on these things could allow for $2 more cost...

moisheh · 08-16-2021, 02:54 PM

I understand your concern but you are overthinking. I reaaly do not think that there are air currents lifting the dish. Think of rv'rs that attach solar panels with facy 3m tape. I had a truck camper with a thin plywood roof. No fiberglass. I mounted it to the roof with expanding inserts. It stayed on. You could use those rubber net serts
Or even the metal inserts that expand like a pop rivet. You could use the mounts from the kit but follow your idea of using a piece of fiberglass held to the roof with sealant. A 6 inch square under each die cast foot. .