Tandem Cycling - Santana Geometry confusion

I have a Sovereign which was made in the 90's. I have been taking measurements and comparing them to Calfee's geometry. I found out Santana does not publish a geometry chart which seems really dumb.
I came up with the following measurements on my small / small frame:

Front stand over: 77cm (same as Calfee)
Rear stand over 72cm (71 cm for Calfee)
Front top tube 53cm (same as Calfee)
Rear top tube 67.5 cm (72 for Calfee)

The rear top tube is the one that stands out.
I found this bit of information:

Sovereign's new for '99 top tube length of 27.75" or
705mm.

It seems Santana at some point lengthened the rear top tube from 67.5 to 70.5 but its still shorter than Calfee or Comotion. Also I have seen standover heights for Santana listed as 72 / 69 which doesn't make any sense.

If I am missing anything please let me know.

Santana prefers to provide its buyers with a sizing table (http://santanatandems.com/Started/TandemSize07.html)instead of geometry tables. As to why, in my discussions with the folks at Santana, they feel the average tandem buyer really doesn't need nor benefit from the additional data: in their view it just muddies the waters and can add confusion. For bike-geek buyers who simply feel it's essential to have those numbers they will provide it upon request.

Stand over heights cited for tandems are often times taken from the top tube at a point just ahead of the saddle noses since that's where the riders tend to end up as they straddle the bike when standing still, much the same as bikes with compact geometry. Additionally, Santana and Cannondale both produce certain model and/or size frames using a stepped-down top tube (http://santanatandems.com/images/07FusionSE(e).jpg)that provides additional stand-over height which could easily be what you saw, e.g., a small-sized Arriva SE or a Picante.

As for stoker compartment length, Santana used 27.5" for a very long time, then increased it to 27.75" around '99 (per your citation from a Jim Leise posting to the Hobbes list) after Co-Motion adopted the 28.5" spec and I believe may now use a 28" stoker compartment. Co-Motion, Calfee and others all used the shorter stoker compartments (27.5" - 27.75") until around the late 90's while some other builders like Erickson, Rodriguez and even Cannondale (pre-99) were using 28" - 31", perhaps even 32" for very tall stokers. Santana has been reluctant to follow current 'trends' and sticks with 28" per their own frame design philosophy, noting that if a customer really wants a longer stoker compartment they'll gladly do a custom build.

Mine is definetly not 27.5, it measures 26.5 between the center of the top of the seat tubes.
I wonder if 27.5 was used on larger frames.

Mine is definetly not 27.5, it measures 26.5 between the center of the top of the seat tubes. I wonder if 27.5 was used on larger frames.

The older you go, the shorter they get. 25" was hardly unheard of in the 70's on many tandem frames and the stoker compartments have gotten progressively longer as time has moved forward. 26" sticks in my head as a Santana spec at one point, as does 26.5" and so-on. However, they've always been the same across the size range for a given year for most production tandems, excluding the older Cannondales (pre-'99) and now the newest where they have made the rear stoker compartment's proportionally longer as the frames got larger. Trek did this on their TX000 frames as well.

The only thing to make sure of is that you're measuring the effective top tube length along a line that runs parallel with the ground, not down the length of a sloping top tube. You can also measure stoker compartments at the boom tube as most tandems use parallel seat tube set at 73*.

Good point. Measuring acroos the boom tube its now 27"