-----Original Message----- From: Kappus, John <[EMAIL PROTECTED]> To: 'Soaring' <[EMAIL PROTECTED]> Date: Wednesday, August 11, 1999 3:08 PM Subject: [RCSE] Wing Building >I had an unusual experience last night when cutting some foam cores (15 psi >pink foam) for a HLG. When cutting extruded foam, there is a lot of >residual stress in the foam itself which causes the core saddles to bow >considerable after they are cut. This has never proved to be a problem when >cutting before because the cores are held firmly to the table with weights. >Last night however, the trailing edge of the core, on the smaller cord side, >was getting scalloped quite badly. It didn't matter how much weight was >placed on the core, or the cutting speed (arm weight), or the wire >temperature. What was happening was the wing core itself had so much stress >in it that it wanted to bow greatly. When the cut reached the trailing >edge, there was little foam left to resist this bow, and the core would bow I cut apx. 1/8 inch of foam off the outside of the block and no bowing. Just take two 1/8 sheets, place them on the table 2 inches outboard of the blank, hold the wire on the sheets, and push the blank through. Just like a cheese slicer. Ric RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
