2009 structural changes in 750, 1320-1440 lbs???

Greetings folks- I am the third owner of a stol 750 that was a 2009 kit, and completed in 2012. I know that only a few months after the kit was purchased by the original owner, zenith adjusted future kits going forward in 2010 as well as provided a modification to pre changed kits that did some structural changes to the spar and overhead section, allowing the max gross weight to go from 1320-1440 lbs. However, if you listed the max gross as anything over 1320 in land configuration (versus float), it wouldn’t qualify as an SLSA anymore. All of my paperwork still shows 1320 as the listed max gross weight with the SLSA nomenclature. But I have no idea if the builder took into considerations the 2009/2010 kit modifications that allowed it to structurally be able to max gross out at 1440.

https://www.kitplanes.com/gross-weight-boost-for-eab-zenith-ch-750/

How would I visually confirm the presence or lack thereof this 2009 modification?

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Permalink Reply by John Burns on March 22, 2023 at 4:45pm

Here is a picture of the Edition 3 attach plate.  The most obvious change is three bolts instead of rivets and the larger rivet size.  This is the only place I am certain you can see a gross weight increase part on a completed aircraft.  The assembly guides are still mostly edition 2 pictures so it was interesting to see all of the changes in the plans that increased the gross weight to 1440.  Sometimes new doublers and sometimes hardware changes.  I think there is also a hardware change on the gear attach that might be visible.

Permalink Reply by Ty Manegold on March 22, 2023 at 5:04pm

Thanks John. I appreciate the confirmation and photo.  Per the previous messages and exchange with the other John on this topic, he was able to confirm the thickness difference between the two plates (0.12 vs 0.19 inches thickness), so I've got my digital calipers all packed up in my flight bag for next time I run to the hangar. It will be good to know another bit of info in the question at hand. 

Permalink Reply by Ken Ryan on March 21, 2023 at 4:05pm

It would be difficult to determine that the triangular spar gusset at the main strut attach point had been upgraded with a snake. If my memory is correct the only difference was that the gusset was thicker. If it was larger in surface area (and I don't think it was) it was not by much.

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