Invisible Parts of Hat

[arku]

Hello guys!
I made hat for demoman with blender. I export the models and I do the same thing with HJ's importing tutorial. In the beta importer, It looks like some parts of my hat is invisible, and transparent. I took this errors;

this is in beta importer;
http://imgur.com/a/sg9MA

this is in blender 3d;
http://imgur.com/a/TnREz

In the blender, all is ok. But in the tf2 importer, some parts are invisible and transparent.

Thanks a lot, Blender Tutorial Community.


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