raw read a tape?

[paul@PERSEPHONE.aegean-sea.dialnet.symbolics.com (Paul Cross)]

I've got 30MB of data written as a tar tape on an SGI 4d70 using a
"low-density" drive.  One tape was written with /dev/tape the other tape
was written with /dev/tapens, which is supposed to write tapes without
swapping the byte order. (ns = no swap)

Neither tape reads on my 3650.  When I try to use :Read Tar Tape, it
quickly return the EOF consition, reads no data, and tells me
"End of TAR input."

Anybody got a way to read either of these tapes using a 3650?  I'd be
content with a raw dump of the data.  I know what the data looks like,
so I could extract it from the TAR muck.  Even better would be a read
tar tape that worked with these tapes.

An explanation of how to make a tar tape on an SGI that a 36xx machine
can read would be great.  I'd like to know what is causing the problem.

OR, if someone can tell me how to make a tape on a SUN that I can read
on a 36xx I may have access to one tomorrow to give it a shot.