To be specific
I use a "Ozark Trail" brand twin size air mattress from Wal-Mart part Num
68957
75" x 37.5" x 7.5" inflated size
The large "exhaust" valve has screw-on thread that fits water bed filling
kit.
It has a velour side for non scratching of car top.
It is nowhere near full at 40 gal, as I routinely fill to 50 "just in case".
I have had occasional "disconnects" in the line and lost some. I think it
would hold more--Let's see----75 x 37.5 x 7.5 = 21,093.75 cu in or 12.207 cu
ft. At 7.48 gal per cu ft that's 91 gal.
I put the hose end under the rear crossbar, and drape the fwd end over the
fwd crossbar. The water flows nicely till nearly empty, then I must fold the
forward part to the rear and so on.
The number from the bar code is 78257 68957
I bought a spare and I am reading from the package. As I recall, the cost
was less than 25 USD at Wal-Mart.

Hope this helps

--
Hartley Falbaum
ASW 27B "KF" USA

"Bill Daniels" wrote in message
news:3hckc.16977$RE1.1449581@attbi_s54...

"HL Falbaum" wrote in message
news:GjXjc.9465$lz5.929079@attbi_s53...
In spite of your preference, I have been using a single bed camping air
mattress from Wal-Mart for years. I put it on top of my Jeep Grand
Cherokee
and fill with gravity. Need a water bed filling kit to attach hose to
the
receptacle. Roll it up when done and it's out of the way. Holds 40
gallons
easily---enough for my '27B


I just measured the top of my Grand Cherokee and it is 37" across between
the roof rack rails and 57" long with the rack crossbars as far apart as
possible. Do you remember which air mattress you use?

BTW, I checked water beds and all I find are 84" long.

Bill Daniels