DR2 Structures PDR Structures and Weight Preliminary Design Review October 5, 2000 Presented By: Jeff Rodrian & Chris Curtis Team DR2 Loren Garrison Chris Peters Mark Blanton

DR2 Structures PDR Areas of Discussion Wing Fabrication Technique & Materials –Wing Loads –Wing Design –Wing Test Fuselage Fabrication Technique & Materials –Fabrication –Design –Payload Layout Landing Gear Configuration & Analysis Weight Estimate

DR2 Structures PDR

DR2 Structures PDR Elliptical Load Distribution b/2 qoqo q(x) x

DR2 Structures PDR x q(x) Trapezoidal Method for Approximating Load Distribution To approximate, The trapezoidal rule was used such that, For wing test loads, h = distance between pads, the load coefficient k pad is found as,

DR2 Structures PDR Wing Spanwise Loading

DR2 Structures PDR Prototype Wing Construction and Test Purpose: Evaluate wing bending and torsional stiffness Practice construction technique Method: Whiffletree system attached on upper surface of inverted wing to simulate air loads Advantage: Easily scale air loads, more realistic than wingtip loading.

DR2 Structures PDR Wing Test Whiffletree Method outbd up looking aft Single Point Load (Outboard pad can be used for subsequent wingtip loading) wing

DR2 Structures PDR Prototype Wing Model Construction and Test Schedule 10/10 Tues.-Fabricate wing skins 10/12 Thurs.-Wing construction complete 10/13 Fri.-Test apparatus complete & test wing 10/15 Sun.-Summarize test results

DR2 Structures PDR Composite Wing Fabrication Methods All methods require female molds of wing skins 1.Dry graphite wet lay-up 2.Fiberglass wet lay-up with graphite tow as spar caps 3.Pre-impregnated graphite lay-up

DR2 Structures PDR Female Mold Fabrication I –Materials Quality hardwood ( i.e. Poplar or Mahogany) –Lower Cost –Ease of manufacturing –Requires sealant –Grain pattern REN board –Designed for mold fabrication for CNC machining –No sealent required –Many sizes available –Costly

DR2 Structures PDR Female Mold Fabrication II –Regardless of material CNC machine on 3-axis mill –Create tool pathes with Surfcam from Iges files generated by Ironcad –Professor Sullivan has given his support of the project Mold issues –Reduce number of molds required with a untapered wing –Machine limits cut length to 4 ft. –Cost of molds

DR2 Structures PDR Dry Graphite Wet Lay-up –Vacuum bag lay-up without any heat –Yields very stiff structure with minimum weight and manufacturing cost –Cost prohibitive without donation ( ~$30/sq.yd.) –Use 2 plies [0/90/±45], graphite spar –Graphite Skin is main load-bearing structure along with spar

DR2 Structures PDR Fiberglass Wet Lay-up with Graphite Tow –Not as light and stiff as graphite –Graphite tow give stiffness to skin –Fiberglass inexpensive (~$4.90/sq yd.) –Graphite Tow very high strength Donation secured from Professor C.T. Sun –3 plies [±45/0/90/±45], graphite tow reinforced fiberglass spar

DR2 Structures PDR Pre-impregnated Graphite –Highest strength-to-weight –Material donated by Professor C.T.Sun –Requires elevated curing temperature ( F) –Molds must withstand at least 250 F –Use 2 plies [0/90/±45], graphite spar

DR2 Structures PDR Wing Structure Sizing –Construct molds regardless of composite method chosen –Secure composite material by end of mold construction (10/10) –Fabricate wing skins with method chosen –Test wing and determine pass/fail criteria –Modify design as required

DR2 Structures PDR Fuselage Sizing –Composite construction employing material used for wing fabrication –Machine female molds of left and right lofts –Possible alternative use male mold from foam –Use knowledge from wing test to determine ply schedule –Add graphite tow at high stress areas to distribute stress Wing attachment Landing gear attachment Tail boom –Design to incorporate simple cantilevered wing attachment system

DR2 Structures PDR Payload Layout –Initial layout done to demonstrate major system integration –Building block for final C.G. estimation

DR2 Structures PDR

DR2 Structures PDR Vertical Tail –Incorporate into mold for fuselage Horizontal Tail –Traditional balsa construction –Base on historic designs

DR2 Structures PDR Landing Gear use lightweight foam tires from Raymer p 274