(b)  
When vacuum pressure is used, take care to ensure a constant, uniform pressure of 5 to 14 psi. A vacuum pressure gauge must be used periodically to check pressure uniformity and consistency.

500 
May 15/69  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  51-51-11 Page 805 

F85853
Serrated Adhesive Spreader  500 
51-51-11  Figure 801  May 15/69 
Page 806 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

ADHESIVE BONDING MINIMUM TIME LIMITS
 Class B-1/2 Class B-2 Assembly Time
0.5 2.0 (hours after adhesive mixing)Curing Pressure Application Time
1.0 3.0 (hours after adhesive mixing)
Curing Time for 77 (+ 5°)F Ambient Temperature 45 72 (hours after application of curing pressure)
Curing Time for 72 (+ 5°)F Ambient Temperature 68 108 (hours after application of curing pressure)
Curing Time for 67 (+ 5°)F Ambient Temperature 90 144 (hours after application of curing pressure)
Curing Time for 62 (+ 5°)F Ambient Temperature 135 216 (hours after application of curing pressure)
Optional Curing Time at 115 (+ 5°)F 12 18 (hours after application of curing pressure)
Optional Curing Time in Minutes at a Bond Line 45 45 Temperature of 185 (+ 5°)F, under curing pressure. Optional cure may be used with Pro Seal 890 only.

 The time limit does not include time in refrigerated storage per paragraph 1.D.
 Additional time under curing pressure is required to heat the bond line from room temperature to 180 °F, and to cool the bond line from 180° to 100°F.
500  Adhesive Bonding Minimum Time Limits 
May 15/69  Figure 802  51-51-11 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

(6)  
Laminated phenolic to aluminum bonds shall be cured under constant pressure (5-14 psi) per step (5) for not less than the time and temperature specified in figure 802.

(7)  
Curing may be hastened by curing at 115° (+ 5°) F under constant pressure for not less than the optional time specified in figure 802.

(8)  
Stainless steel to aluminum bonds shall be cured under a constant pressure of 10 to 14 psi for not less than the time and temperature specified in figure 802.

(9)  
Cured excess adhesive may be removed by the following method: (excess adhesive includes extruded adhesive extending higher than the plane of the rub pad and more than 1/4 inch beyond the edge of the rub pad unless otherwise specified).

(a)  
With a hardwood or plastic wedge, scrape away the excess adhesive.

(b)  
Clean residual adhesive from the aluminum by rubbing the area with a clean gauze moistened slightly with methyl ethyl ketone.

3.  Field Repair of Bonded Rub Pads with No Heat Source Available
A.  General

(1)  The following process is recommended for a field repair of bonded rub strips when a short cure time is necessary.
B.  Repair Bonded Rub Pads
(1)  The rub strip to be repaired may be reworked per paragraph 2.D. with the following exceptions:
(a)  
Pro Seal 890 B-2 shall be used as the adhesive.

(b)  
The ratio of activator component to the base component shall be 22 (+ 2) parts by weight of activator to 100 parts by weight of base.

(c)  
The new rub strip shall be prefitted on the assembly after the faying surfaces are cleaned and before the adhesive is applied. The rub strip shall lay flat against the assembly surface without the aid of holding or clamping devices. The gap between the mating faying surfaces of the prefitted rub strip and the assembly shall be a maximum distance of 1/8 inch. The new rub strip may be rolled out with a clean roller against a smooth surface to improve the prefit.

(d)  
The parts shall be assembled within 25 minutes after adhesive mixing.

(e)  
The cure time and temperature shall be a minimum time of 6 hours at a minimum temperature of 64°F.

(f)  
The following method of applying curing pressure shall be optional to the process in paragraph 2.C.: 1) During the first three hours after the parts are assembled, smoothing pressure

500 
51-51-11 Page 808  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 15/69 

shall be applied to the rub strip at intervals of no more than 15 minutes.
2)  The method of smoothing shall be in accordance with that in paragraph 2.C. A continuous bead of extruded adhesive at the bond line is desirable because it indicates proper contact of the faying surfaces. As the adhesive cures during the first three hours after the parts are assembled, increasingly greater smoothing pressure is required to squeeze out any air pockets forming in the bond line.
　
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