Original Posted By: John Egan
Subject: Re: Pietenpol-List: Brodhead Pictures gone to Piet "improvements"Jack Phillips wrote: Durn Corky - you're gonna get the purists all activated! I think there's much that could be improved on the Pietenpol as well, [big snip]I decided I should improve a couple of things on my Piet.The original airfoil was a weak link, so I substituted a thicker, less cambered, airfoil. This let me put in stronger, lighter, spars and mount the aileron control cables internally. It also gave me much better flying characteristics.The wing strut cross-bracing seemed like it could easily be replaced by a V-type strut arrangement so I mounted the bottom end of the rear lift strut at the same point as the front strut with an adjusting mechanism to get the right dihedral and washout. Again, improved flying characteristics.The tail bracing bothered me so I built thicker horizontal and vertical stabilizers with strong spars, making the external bracing unnecessary.With a thicker horizontal stabilizer, I was able to mount the elevator halves on a torque tube that could be actuated by an internal pushrod, getting rid of the external elevator control cables.With the decreased drag the above modifications gave, the speed increased until the noise and buffeting of the open cockpit was unbearable, so I increased the front windscreen to full height between the fuselage and wing. With that, it was easy to add wrap-around panels to completely close off the cockpit. I could now have conversations with the front seat occupant without an intercom.The windscreen mod decreased drag even further, so the attainable speeds got up to where structural integrity was a concern. I replaced the wooden fuselage with an aluminum monocoque type; much lighter and stronger. With the windshield wrap-around, ingress and egress were a problem for both seats so I made a kind of sliding canopy. The cabane struts were in the way so I lowered the wing to eliminate them.Since the wing spars were now mounted directly to an aluminum fuselage, it became reasonable to convert the wings and tail to aluminum as well. With thicker wings, I was able to completely eliminate the lift struts, making a much slicker airplane.I'm very happy with my modified Pietenpol, but I get some comments from behind-the-times purists. Four different Pieters have said I "radically vandalized" Bernard Pietenpol's original creation. That's why I call it an RV-4.Mike________________________________________________________________________________