BD5builder
Well-Known Member
As i'm sure a few of you know, Jim Bede was highly Fond of the tube spar design for the BD-5. Most of the people i have talked to say the stock 21.5 ft wings have WAY too much flew and wing wrinkling in normal straight and level flight causing a different cross section of the airfoil (when at rest) which causes a somewhat higher stalling speed. Jim Bede put out (in the BD-5 group) a proposed solution to some of the wing flex problems for the -5. He proposed using 3-4 layers of carbon fiber and somehow forming it (i'm thinking something like the opposite of a vacuum bagging process) to epoxy the carbon fiber to the inside of the tubular spar. BD-micro has already designed a VERY successfull solution to this same problem (but costs $1200). They use a 7075-T6 aluminum bar stock that is machined to a I beam spar insert that is inserted into the center spar section and "locks" onto the landing gear trunions (what the struts Rotate around). My question is this:
If i were to go about the Jim Bede way and use the carbon overlay method, could i also use take some 1/4" high density foam, cut this to a shape to fit inside the wing spar and also wrap it w/ 3 or 4 layers ( 90 deg. too each other and 45 degree to the lengthwise edge, to give a X shaped pattern down the stiffner) and mount it 90 degrees to the chordline and possibly get the same effect as the metal I beam structure w/ the same or slightly less weight? I was also planning on having a section of the carbon spar (I beam section) protrude into the center wing spar to butt up against trunion bolts w/ a U shaped section to wrap around them.
Thanks,
thomas
P.S. here's the link to the article describing the stiffner mod:
http://www.bd5.com/bedesparmod.htm
If i were to go about the Jim Bede way and use the carbon overlay method, could i also use take some 1/4" high density foam, cut this to a shape to fit inside the wing spar and also wrap it w/ 3 or 4 layers ( 90 deg. too each other and 45 degree to the lengthwise edge, to give a X shaped pattern down the stiffner) and mount it 90 degrees to the chordline and possibly get the same effect as the metal I beam structure w/ the same or slightly less weight? I was also planning on having a section of the carbon spar (I beam section) protrude into the center wing spar to butt up against trunion bolts w/ a U shaped section to wrap around them.
Thanks,
thomas
P.S. here's the link to the article describing the stiffner mod:
http://www.bd5.com/bedesparmod.htm
