Lower wing spar

[HC338]

I started working on my Hatz classic last November. I have all the ribs made and the spars cut to width and length. I am starting with the lower wings. I was laying out the taper an the wing tip end of the spars according to the plans. When I checked the rear spar opening on rib 10 it is about 3/16 smaller than the spar taper layout. Dose anyone else remember this discrepancy and how did you decide where to remove material, from the top and bottom in equal amounts?
Thanks,
Jim DeYoung

[MarkM]

Hi Jim!
I’m not sure what others have done, but this was what I did. First off, the tapers shown on the plans make absolutely no sense, since if you stretch fabric over the bottom of that wing, the taper of the planes defined by the fabric will go from rib #9 to rib #10 to the tip bow. What does tapering that spar at some arbitrary point 6” past rib #9 accomplish? Does the fabric just magically conform to that spar taper without another rib being there? Of course not!

I simply tapered the spar from the outboard edge of rib #9 to the plans tip bow location. This leaves the spar about 1/4” smaller at the rib #10 opening at that location; I just used that small gap to my advantage, tweaking rib #10 into place to make the tip bow work out.

You’ll find the Classic plans are one Excedrin headache after another with all of the small annoying errors. Most of them are documented on this forum, though I’m not sure if anyone in the association has actually corrected the plans that they’re selling now. My own recommendation with any issue is to first check the forum, and then check the CB-1 plans. Don’t have CB-1 plans? By all means, get some: that’s the original design that the Classic is based upon. Any discrepancies between the two are either due to something Billy Dawson/ Jeff Shoemake changed to the design (and sometimes screwed up, like the aileron idler or fuel tank), or simply an error on the Classic plans.

I hope this helps! Hang in there and keep on building!
Mark Matelski

[HC338]

Thank you so much for the information Mark!
Is your Hatz built or are you building?

[mmarien]

Jim

I had trouble figuring out the end of the wings. I ended up redesigning the bow and Rib# 10. I put it in my blog here:

https://myhatz.blogspot.com/2016/12/christmas-2016.html

[mmarien]

For me, the spars need to be filled between the ribs to make a smooth transition to the bow. Another page of the blog here. The forum wouldn't let me add two URL's to the last message.

https://myhatz.blogspot.com/2017/05/201 ... uches.html

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