Pietenpol-List: C.G., Fuel, & Long Legs
Posted: Wed Jul 02, 2003 12:12 am
Original Posted By: "rod wooller"
Subject: Pietenpol-List: C.G., Fuel, & Long LegsIn a message dated 7/1/03 2:38:51 AM Central Daylight Time, ashcan(at)earthlink.net writes:>Jim,B.H.P. stated the aft C.G. limits to be 1/4 chord as the forward limit (25%), and 1/3 of the chord as the aft limit, which is 33 1/3%. I believe he determined this, by flying experiments. This makes the forward C.G. limit to be15" aft of the leading edge, and 20" aft of the leading edge as the aft limit. I've never heard of the aft limit of any Hershey bar wing being more than 30% of the chord. The airfoil is a 'Reflexed Airfoil', or 'Undercambered Airfoil',meaning the bottom surface is somewhat concave. It's like flying with a notch of flaps always in, making gobs of lift and drag. This causes the planeto have a tremendous amount of negative pitching moment (nose down tendency). Tooffset this, the plans call for the wing to have 2 of positive incidence (it's on the page with the fuselage build up - done by making the front cabanestruts to be 1" longer than the aft cabane struts), and the stab to be 0. I believe this negative pitching moment is how the Pietenpol gets away with suchan aft C.G. limit so far back. As far as the fuel changing the C.G., my most aft loading configuration would be with Zero Fuel, and 205 lb. Pilot, which puts the C.G. to be right onthe aft limit (I hope I never have to land - out of fuel !!). With but 3 gal.of fuel in the cowling tank (Minimum Fuel), and the wing tank empty, the C.G. is 19.52" aft of the Leading Edge. With the cowling tank full (10.5 gal.), wing tank empty, the C.G. is 18.38" aft of the Leading Edge - my Most Forwardloading configuration. With the cowl tank full, wing tank full (9.5 in the wing), 120 lbs. of fuel - Max Fuel C.G. is 18.60" aft of the Leading edge, with20 gal. of fuel onboard. This should give me about a 3 1/2 hour range !! Someday soon, I'm going to check out 'er Long Legs!!! Naturally, with Max Fuel, the stall speed will go up a little, but as far as the handling characteristics, I really can't tell much difference in the air, although I didmake a couple of those 'splat' landings - embarrassing, but a Pietenpol is a tough airplane !! With more experience I'm sure I'll hone my skills. I practiced landings yesterday for 1.3 hrs. With a full belly (Max Fuel), she seems to wallow around on the ground somewhat. I have room to carry a 157 lb. passenger,max fuel, and still stay under my 1050 lb. gross weight limit.Chuck GantzerWichita, KSLeaving for Brodhead on the 23rd !! I'll post my flight plan soon, and see if any Piet Pals are on the way. One stop I'm planning on is our Hallowed Ground, in Cherry Grove MN.________________________________________________________________________________
Subject: Pietenpol-List: C.G., Fuel, & Long LegsIn a message dated 7/1/03 2:38:51 AM Central Daylight Time, ashcan(at)earthlink.net writes:>Jim,B.H.P. stated the aft C.G. limits to be 1/4 chord as the forward limit (25%), and 1/3 of the chord as the aft limit, which is 33 1/3%. I believe he determined this, by flying experiments. This makes the forward C.G. limit to be15" aft of the leading edge, and 20" aft of the leading edge as the aft limit. I've never heard of the aft limit of any Hershey bar wing being more than 30% of the chord. The airfoil is a 'Reflexed Airfoil', or 'Undercambered Airfoil',meaning the bottom surface is somewhat concave. It's like flying with a notch of flaps always in, making gobs of lift and drag. This causes the planeto have a tremendous amount of negative pitching moment (nose down tendency). Tooffset this, the plans call for the wing to have 2 of positive incidence (it's on the page with the fuselage build up - done by making the front cabanestruts to be 1" longer than the aft cabane struts), and the stab to be 0. I believe this negative pitching moment is how the Pietenpol gets away with suchan aft C.G. limit so far back. As far as the fuel changing the C.G., my most aft loading configuration would be with Zero Fuel, and 205 lb. Pilot, which puts the C.G. to be right onthe aft limit (I hope I never have to land - out of fuel !!). With but 3 gal.of fuel in the cowling tank (Minimum Fuel), and the wing tank empty, the C.G. is 19.52" aft of the Leading Edge. With the cowling tank full (10.5 gal.), wing tank empty, the C.G. is 18.38" aft of the Leading Edge - my Most Forwardloading configuration. With the cowl tank full, wing tank full (9.5 in the wing), 120 lbs. of fuel - Max Fuel C.G. is 18.60" aft of the Leading edge, with20 gal. of fuel onboard. This should give me about a 3 1/2 hour range !! Someday soon, I'm going to check out 'er Long Legs!!! Naturally, with Max Fuel, the stall speed will go up a little, but as far as the handling characteristics, I really can't tell much difference in the air, although I didmake a couple of those 'splat' landings - embarrassing, but a Pietenpol is a tough airplane !! With more experience I'm sure I'll hone my skills. I practiced landings yesterday for 1.3 hrs. With a full belly (Max Fuel), she seems to wallow around on the ground somewhat. I have room to carry a 157 lb. passenger,max fuel, and still stay under my 1050 lb. gross weight limit.Chuck GantzerWichita, KSLeaving for Brodhead on the 23rd !! I'll post my flight plan soon, and see if any Piet Pals are on the way. One stop I'm planning on is our Hallowed Ground, in Cherry Grove MN.________________________________________________________________________________