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repair5 - rebuild the landing gear and fuse rings

Repair 4

Cardboard Template

Template Location per Fuselage

   After a few tries, this cardboard template is the result.  The existing ply reinforcements on either side of the fuselage were removed. A carbon fiber layered over thin plywood will be used for the new support to interface the detachable wings. Existing plywood - fiberglass structure is not strong enough for the larger wing.

Plan View of Wing Support Section

View toward nose of wing support section.

  Carbon fiber over plywood stock for use in making structure to support larger wing loads. A set of various size load bearing plates to fit inside fuse.

   The carbon fiber composite plate (shown here) fit the internal fuse opening using a dremel wheel and point cutting bit.  A drill was used to mark the shape to remove.  Then, round and flat files scoured out the rough edges. At close to an ounce, this plate is several layers CF over birch ply; this is to provide a brace for the wing supports - mostly vertical forces in compression and tension.  Use gloves - nitrile or laytex for abrasive work on these composites. For wet epoxy work, use  nitrile or industrial butyl gloves to preserve your hands along a mask with OV filters and well ventilated area - at a minimum.   

     As this plate is the first in a series of structures which must work together to provide adequate load bearing strength, all pieces are first made, fit, then epoxy bonded together.

     Actually, at this point, the scope of work is no longer limited to repair but is now modification to fit and bear the higher possible loads from the new wings; both the 8 foot and the 6 foot wings.

Preliminary cut to fit of CF-FG-ply 50kips/psi epoxy wing wall brace

   Note: 1 kip = 1,000 pounds.

   Carbon fiber here (CF) has tensile strength in excess of 500,000 pounds per square inch but must be protected from ultraviolet (UV) light or the epoxy becomes useless in strength over long exposure to UV.   As CF is used in composite form mixed with epoxy, its tensile and compressive strength is much less. The math involved in strength analysis of composites is more complex than isotropic  metal construction. Test to verify strength. Paint urethane UV blocker or opaque paint over CF to protect the epoxy.  Also, CF should not be bonded to aluminum.

   In many cases, destructive measured testing of the forces at issue is performed to verify the accuracy and validity of its designed performance. In other words this testing establishes a demonstrative standard of proof beyond a reasonable doubt and not simply clear and convincing, which simply means more probable than not - a much lower standard to pander to persuasion, perhaps self interest or simple belief; not one to steak you life on.
 

  Left : looking into Botmite fuselage which images the newly made CF plates along with the steel tube (electrical conduit) for aligning the wing supports.

  Above: Clamps hold template over carbon fiber plate which is ready for cutting.

Left - Four freshly cut CF fuse reinforcing rings or fuse ribs with openings. Each wing has 2 wing interconnects to provide stiff strong wings while attaching with bolt strength ( 1 kip each) to the fuselage.
   By distributing these forces over a large surface area of the fuse, the prospect of shear forces damaging the aircraft or wing struts is diminished.
   Fuse rings brace slide-on wing CF tubes using a wrap over pipe.

  Above - 1/2 inch steel conduit connected to serve as alignment tool for larger wing installation.

Carbon fiber rings - fiberglass epoxy with birch ply core composite fuse rings provide the high strength in tension and compression using little material weight.  Material expense was modest while labor and cutting proved time consuming per many refinements and changes.  Testing included pass through of cable plant and control wiring. Wear gloves working with carbon fiber or have itchy pain for days.

     CF ring details: Several layers of carbon fiber and a 10 oz. / sq. yd. fiberglass layer wrapped over a thin birch core. The mold less form:  vice compressed in a mylar wrap between two half inch thick steel plates while the epoxy set were used to provide the base material for these fuselage rings. Further support integrating the rings to the fuselage using small diameter carbon fiber rods parallel to the fuse epoxied to these rings covered by carbon fiber fabric to the fuse.  Result: a monolithic form or unibody structure able to support high shear forces and distribute loads and control forces to the aircraft.  Properly anchored, each set of fuse rings can support a 1,000 pound force in tension, somewhat less in compression.  


Repair 6

PRELIMINARY TO TEST: know the risks, wear eye protection, stay at least 10 feet away from truck. Have a crew to help. DO NOT HOLD ANYTHING DOING THIS TEST.  Have competent adults present.  Powerful forces at work here.  Severe injury can result with any accident and or destruction of work pieces.  Failure can be instant, fast, catastrophic and destructive. Use at your own risk! 

  Crush Test - first test whether the composite pipe will collapse under almost a kip of compression.  Drove truck 3,800 pounds over the FG-CF tube to hold wing inserts: Success. 
  
   Shear Test - suspend composite pipe inside a steel square tube with atop a stack of concrete solid blocks or brick. Now, place half inch thick steel plate for truck to drive over with steel chain in front of truck. Weigh down the other side of the steel square tube with sandbags which provide at least 10:1 ratio at a distance of 4 feet (minimum length of steel square tube..

     Bending Test - put a load of about 1 kip on the point where the wing insert fits inside the composite pipe.  Note: a steel sleeve is over the insert at maximum point of bending force while the inside of the wing insert is solid all the way to the center using a solid 0.25 inch steel round or stainless steel round rod.   Where the wing meets the fuselage, there should be about 1/4 inch solid fiberglass or carbon fiber rib structurally epoxied to the internal stringers and ribs and the composite wing skin.

       These various low cost strength tests are simple basic tests preliminary to further testing to precede flight testing 10 + g fully loaded botmite 1.1 aircraft. Weight and balance testing is covered elsewhere.   

DISCLAIMER: The information presented here is without warranty and no guarantee that it will work for you. No liability whatsoever is accepted by using any of this information on any legal theory or system of law. Your construction is your responsibility as are the design and engineering. All technical information presented here is for information only.  Your use of this information is solely at your own risk. Should you use any of this, you agree to hold Rentnet, Inc. and all parties contributing herein harmless from any injury which may result or risk of injury or legal theory without fault or responsibility.   

Copyright (c) 2011-14 by RentNet, Inc. All rights reserved.

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