Pietenpol-List: Drag wires/ stuctural integrity/ weight...
Posted: Fri Mar 24, 2006 4:39 pm
Original Posted By: "Mark Blackwell"
Hans,Of course you are correct when you say, "Looking at points of the airframe that break during a crash is not necessarily relevant." The only place where it is relevant is in the structure protecting the occupants. People have survived some bad crashes with Pietenpols (BHP himself told me this when I visited him in 1982), attesting to its toughness in this respect.The Pietenpol design has demonstrated, for over 75 years, that it is amply strong for normal operations and really doesn't need to be "beefed up" anywhere. In the 1932 FLYING AND GLIDER MANUAL, P.31, engineering professor Joseph Wise said of the wing, "No need to go through any analysis on that job, unless you want to save weight."Having said this, when I built mine (1959 - 1970), I had to compromise by substituting Douglas Fir for Sitka Spruce in the wing spars and using Aeronca and Taylorcraft strut material for the lift struts. I simply could not afford the Sitka Spruce and proper sized streamline tubing at that time, and scrounging was the name of the game. The availability of 1/8" cable "at the right price" dictated its use instead of the 3/32" stuff specified for the drag/antidrag bracing, etc. Poverty does circumscribe one's options!Of course, this added some weight to an already adequate structure, so I tried hard to save weight in non-critical areas to compensate for this. I think I was reasonably successful because, at the last weighing, the dry empty weight with a C85-8 engine was 630 lbs. Mine is the lightest of four Piets in our area; the others are at least 30 lbs. heavier. Frankly, I don't know where their extra weight came from.Today, I feel confident that I could get the empty weight down to around 600 lbs.,should I build another Pietenpol. (That won't happen.) The lightest Pietenpol I know of is Brian Kenney's CF-AUK in southern Ontario. Its empty weight is significantly less than 600 lbs.! Obviously, he didn't "beef up" anything--but he is a professional engineer and likely analysed the structure, probably finding it more than adequate as designed.Graham Hansen (Pietenpol CF-AUN)________________________________________________________________________________Date: Fri, 24 Mar 2006 22:34:28 -0500
Hans,Of course you are correct when you say, "Looking at points of the airframe that break during a crash is not necessarily relevant." The only place where it is relevant is in the structure protecting the occupants. People have survived some bad crashes with Pietenpols (BHP himself told me this when I visited him in 1982), attesting to its toughness in this respect.The Pietenpol design has demonstrated, for over 75 years, that it is amply strong for normal operations and really doesn't need to be "beefed up" anywhere. In the 1932 FLYING AND GLIDER MANUAL, P.31, engineering professor Joseph Wise said of the wing, "No need to go through any analysis on that job, unless you want to save weight."Having said this, when I built mine (1959 - 1970), I had to compromise by substituting Douglas Fir for Sitka Spruce in the wing spars and using Aeronca and Taylorcraft strut material for the lift struts. I simply could not afford the Sitka Spruce and proper sized streamline tubing at that time, and scrounging was the name of the game. The availability of 1/8" cable "at the right price" dictated its use instead of the 3/32" stuff specified for the drag/antidrag bracing, etc. Poverty does circumscribe one's options!Of course, this added some weight to an already adequate structure, so I tried hard to save weight in non-critical areas to compensate for this. I think I was reasonably successful because, at the last weighing, the dry empty weight with a C85-8 engine was 630 lbs. Mine is the lightest of four Piets in our area; the others are at least 30 lbs. heavier. Frankly, I don't know where their extra weight came from.Today, I feel confident that I could get the empty weight down to around 600 lbs.,should I build another Pietenpol. (That won't happen.) The lightest Pietenpol I know of is Brian Kenney's CF-AUK in southern Ontario. Its empty weight is significantly less than 600 lbs.! Obviously, he didn't "beef up" anything--but he is a professional engineer and likely analysed the structure, probably finding it more than adequate as designed.Graham Hansen (Pietenpol CF-AUN)________________________________________________________________________________Date: Fri, 24 Mar 2006 22:34:28 -0500