Creating a sparse bundle
First purchase and download SuperDuper from Shirt Pocket Software.
Select the source volume on the left and then select Disk Image... on the right.
After testing please purchase a license to support the developer.
Choose a location for the bundle
Select a local drive or RAID. Make sure Read/Write "Sparse" Bundle is selected. This will create a special bundle file that will contain lots of 8MB bands that can be efficiently copied to LTFS.
Backup the bundle to tape
In the Edit Paths... panel add the date token to the path to keep your bundles separated.
Keep this bundle locally on a drive as you can run SuperDuper again to update this on a regular basis.
Then you can backup the new bundle to tape.