Tuesday, July 5, 2016

Ch 9.6: Landing Brake

The landing brake (LB) helps provide some needed drag during landing approach to make a steeper decent and a better view of the runway for the pilot.  It is a hinged flat board that deploys from the belly just behind the front seats.  The plans call for a mechanical mechanism to deploy it however most builders today convert this to an electric actuator.

Building the Brake
The building of the landing brake started in an earlier chapter when the brake was cut out but then re-glassed back into the fuselage bottom until Ch 9.  So the completion of the brake starts with cutting it lose.

I decided early that I wanted the hinge for the brake to go almost the full width instead of just 10" per the plans.  I'm hoping this will keep it from warping the way several builders have reported.  To do this, all I really had to do is adjust the number of attach points/screws.  I'm also widening the wooden support the actuator connects to to provide a little more crosswise support.  My hinge runs ~22" of the ~24" width of the LB.

Installing the Brake Hinge Support
I used 7 screws to attach the hinge to the fuselage and 8 screws attaching the hinge to the LB.  Other than the added number of screws/slugs to the hinge line, everything else pretty much followed plans.

Preparing the LB Cavity in the Fuselage
After securing the LB-23 hinge support into the fuselage, I routed out the interior of the landing brake cavity using a dremel routing tool to make room for the glass to be added.

I then located where the actuator would come through the bottom and beveled the foam to that area. The cavity was then glassed per plans.  At this point, each slug buried into the foam of the fuselage was drilled and tapped for 10-32 screws and the brake was test fit.  In order for the brake to hide nicely under the fuselage, micro must be used to fill the remaining depression.  I taped off the brake edges and the hinge to ensure release and filled the edges and the surrounding depression with micro. Then I closed the brake flush with the bottom of the fuselage to let cure.  TIP: I would recommend putting some kind of release agent on the tape. I almost epoxied my LB closed :-) .  This process essentially makes a mold of the inside edges and perimeter of the brake in the fuselage bottom so that when it closes it basically disappears nice and neat.  See video at the end.

Glassing the cavity
Routing out the fuselage cavity
Micro curing in the depression
surrounding the landing brake.  The
boards ensure the brake sits flush
with the bottom of the fuselage.

Installation of the Actuator
I'm using a Firgelli actuator, model FA-PO-150-12-4.  It has a 4" stroke, 150lbs of static force, and a feedback potentiometer in case you want to wire it up to an electronic indicator.  I made glass brackets similar to Wayne Hicks however I only ended up using the larger one to attach the actuator to the back of the seat. 

The brackets were made similar to Wayne Hicks brackets, with 8 ply of BID...4 running along the bottom, 4 running from the bottom and up the side on each side, with another 4 layers forming a U-shape in between the sides.  A picture would be good here, but at any point on the bracket there are 8 layers of BID.  I used a scrap piece of foam to form around which was cut the width of the actuator attachment.  I let it cure, cut it to shape, put adjustment holes in it to allow me to adjust the closure of the LB once installed.

Assessing where to mount the bracket
on the seat back.
Installed Actuator
with homemade
The fuselage side bracket is mounted in the back of seat on the passengers side close to the center seat support.  I glassed an oversized piece of birch plywood on the back of the seat.

Between the seat and the birch, I embedded two EZ-point locking nuts  vertically where two bolts hold the bracket in place.  The actuator is then attached to the bracket with an AN Pin and castle nut to secure it.  For the LB bracket, I simply used the aluminum brackets, part no. CZLB-18 available from the Cozy Girrls.
Voila !...My first moving part...Onward.

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