fr3dcat

The wingtanks.com tanks I had had a vent on the single filler cap.  Let me clarify.  The vent on the cap is a 90 degree tube pointed into the relative wind.
 
My tanks also took a long time to fuel as well. 
Tim

The wingtanks.com tanks I had had a vent on the single filler cap.

I have them in my left wing of my Subaru powered Mark IV.  I dont like them.  They don't seem to feed well when they are below 1/2 tank.  In fact i had them quit feeding on me and the engine quit and I landed in a hay field.  When I rolled to a stop the engine started up.  That happened at about 300 hrs.  I put that tank in at about 285 hours.  
 
It reminded me of fuel venting problems I sorted out in the first hour of initial flight test with the original Avid fiberglass tank.
 
it seemed like that the two tanks have about a gallon each unuseable.  
Tim Morris
s/n 1492
 
 
 

EDMO,
Modifying the originals is not off the table by any means.  I am approaching this with caution because airfoils can be tricky. (i.e. pitching moment, center of lift, controllability).  There is plenty of experience out there with the existing speedwing and KF airfoils.  I was not aware of the files in the forms section.  They were of great help.
So my question is how did the airplane fly with the undercamber heavy hauler rib modified with to mimick the Riblett with the flatter slightly curved bottom and leading edge extension?
Did it change the pitch?  Stall speeds ok and controllability ok?
Thanks
Tim