Speed Brake Construction |
Date: 10 June 2002 - 1 August 2002 |
Chapter: 6.0 Speed Brake |
!! COMPLETE !! |
June 10, 2002 - Chapter 6.0.1 -
"Speed Brake Cut-Out"
The majority of the speed brake work was done during our visit to the factory's Head Start program. After taking inventory of our parts and getting the doors and keel off of the airplane, we cut the indicated door out of the bottom center of the fuselage.
As with all cut outs of this type, the foam in between the two skins of the fuselage is sanded out about 1/8" deep, and is filled with microglass and covered with BID.
June 10, 2002 - Chapter 6.0.2 - "Cover
Speed Brake Hole and Edges"
After cutting the speed brake door out, you hot glue it back into the fuselage with tongue depressors. You double up on the tongue depressors in the opening, however, to force the door 1 thickness of a depressor up into the fuselage cutout. This will provide the necessary operating clearance (1/16th of an inch) later.
Next the fuselage floor was sanded to prepare it for the overlapping glass layups to follow, by about 4" or so. The brake door was then covered with duct tape. Don't go crazy here, I initially covered the door and it's edges so thoroughly that it would not go back into the whole. We actually did this work after the Fuselage reinforcement layups that are needed for speed brake hinges, see Chapter 6.0.3 below.
Next we prewet some triaxial cloth to cover the speed brake opening, one 20"x30" and one 16"x26", laid with their major axes opposing each other (the smaller's major axis parallel to the centerline). Once this cured, we popped the brake out by pressing on the inside of the fuselage and sanded it to fit. We brought all of the edges back about 1/8" so that it would fit once we laid the BID on the edge of the speed brake door, and the beveled the leading about 1/4" (until with the hinges attached we got 60° of brake acutation). The manual indicates to do this right after repairing the door out, as well as laying one bid on the edge, however we did this after the fuselage repair work and hinging/fitting work had been completed.
2 Ply Triaxial Layup over Speed Brake Cut-out
Also in this section is the layup of the edge of the speed brake the same as we did with the speed brake cutout on the fuselage. Again, we elected to do this well after we fit the door in back in the fuselage, but you mileage may vary as they say.
Speed Brake Edge Layup
June 11, 2002 - Chapter 6.0.3 - "Speed
Brake Reinforcements"
Next the speed brake was reinforced to accept it's hinges and actuator. To do this we measured over from the centerline 7" in each direction, and centered a 3x3 hinge in these locations, cutting down to the outer skin and removing the foam and inner skin. We did the same for the actuator with a 5" long x 3" wide cutout at centered on its long axis 8" from the trailing edge, extending 1" to the pilot and 2" to the co-pilot side. The 3x3" hinge cut-outs were then duplicated on the fuselage side of the opening. As mentioned previously, we did all of the reinforcing work prior to covering the speed brake cut-out back up.
June 11, 2002 - Chapter 6.0.4 -
"Hard Points"
Next the cutout areas were sanding down to the inner skin, and 5 plies of triaxial cloth were prepared to reinforce these points. Once these layups were wetted out and applied to the cut-outs, and microglass radius was made in the corners, and layer of BID was applied to overlap the cutout by about an inch.
Speed Brake Hardpoints
Here I actually made a mistake and let two layers of triax get stuck together while doing the co-pilot side hardpoint. I realized later that this made the two sides imbalanced, and had to make an aluminum shim for the pilot side to get even pressure and alignment. Don't try this at home....
June 12, 2002 - Chapter 6.0.5 -
"Install Speed Brake"
This section has you dry fit the speed brake and sand any interferences, which we've already done. Just my 2 cents, by the way, but these "creepers" are the cat's meow for this kind of work (we have done all of the work thus far with the bird on its on legs...). Anyway, then you're to make the 2" wide notches for the hinge pins to sit in. It's important to get good alignment between the hinges so that it swings freely, then drill and cleco them into place and check for good operation. Then you can drill the rest of the holes. Also, you'll find that the pins will zip right out of these hinges at the least provocation, so it was made clear to us that anywhere you have these babies, make sure that the notch for the hinge pin fits tightly so that this cannot happen by accident. Next the holes in the hinges get tapped, and the bottom of the fuselage countersunk. Actuator details are in the Keel section of Chapter 10 - Fuselage.
Test-Fitting the Speed Brake
~ End of Chapter ~ End of Section ~
This Section completed 8/1/2002