Extra 200 - Page 266

CHAPTER 51
PAGE 23
EXT
RA - FLUGZEUGBAU GmbH
SERVICE MANUAL EXTRA 200
PAGE DATE: 1. July 1996
The damaged area of the inner laminate has to be taken out as
well. Make sure not to increase the disbond area by preparing
the hole. Preferably use a hand held milling machine. In case
of cutting with a saw, the pulsation stress may peel of the
inner laminate (secondary damage). If the extent of the
disbonded area on the inner laminate exceeds the prepared
cut out, increase the cut out of material and upper laminate.
Prepare a scarfed overlap of laminate around the circular cut
out. Overlap length of inner laminate should not be less than
20 mm.
I M P O R T A N T Overlap length of the upper laminate should not be less
than 1/50; (ratio: laminate thickness / overlap length).
Prepare a replacement block of core material (foam or
honeycomb) with equivalent diameter and thickness. Cut it
to fit snugly in the trimmed hole. In case of foam core, coat
one side with a mixture of resin and microballoons (ratio
100:15). Apply pre-laminated fabric layers required for the
inner laminate on this side of the core filler block. Ensure
correct style and direction of fabric. After precuring the
laminate at elevated room temperature (30°C), scarf the
overlap and sand the upper overlapping core material down,
up to the surrounding core material.
Subsequently clean the repair area thoroughly as follows:
- Remove the sanding dust with a pneumatic vacuum
cleaner
- Clean the scarfed overlaps with carbon-tetrachloride or
acetone in case of dirt or grease was introduced during the
preparation.
W A R N I N G Carbon-tetracloride or Acetone used for cleaning re-
pair areas are flammable liquids and should be used
with proper ventilation and safety equipment.
I M P O R T A N T Repair area must be free of dirt and grease.
Wet all surfaces of the backing plate and the scarfed area with
resin mixture. Lay on pre-laminated fabric layer in accordance
to the layer sequence plan. Ensure correct style and direction
of fabric.
REPAIRS
Repair of Sandwich Material