According to the plans, the flaps are the easiest controls to build.  The plans are right (except for the blind fasteners in the spar to rib).  The first 8 pictures of the left and right flap assemblies will be the same in both sections.  The narrative will be the same as well.  This is because I did the preliminary work on both flaps at the same time and decided not to differentiate.


Wing flap parts and instructions Ritchie removing the protective coating

Above left are the parts for both the left and right flaps just prior to beginning the construction process.  Above right Ritchie has begun to remove the protective coating from the inside of the flap skins.  As per my normal procedure, I will leave the coating on the outside of the skins for now.  In case you didn't read the narrative on the ailerons or the Forward Fuselage, Ritchie is from Guayaquil, Ecuador and is here for his Summer school vacation which is in February and March as opposed to July and August in the US.

Ritchie cleco-ing a flap together Assembly at this stage is to check for fit


In the two photos above, Ritchie is assembling the flaps with clecos to make sure everything fits as it should.  Teaching other people how to do these tasks makes assembling this airplane all the more enjoyable.


Both flaps cleco'd together Making the FL-706A


The photo above left shows both flaps cleco'd together.  At right above, the 1.5 X 2 X .125 angle supplied with the kit is in process of being sawed into two re-enforcement angles, part number FL-706A, that get riveted to the inboard rib and the inboard end of the forward spar.


FL-706A clamped to the spar Drilling the existing fastener holes

Above left is the FL-706A re-enforcement angle clamped to the the FL-703 spar.  Above right the existing fastener holes are being transferred from the FL-703 spar to the FL-706A on the drill press.

Laying out the 5 added fasteners Drilling the added fasteners


The two photos above show Ritchie laying out and drilling the 5 holes that get added to the FL-706A. 


FL-706A cleco'd to the spar Bending the FL-706B

Above left is the FL-706A cleco'd to the spar.  At right is the FL-706B in the process of having a slight bend put in it on the bending brake. 

FL-706B to inboard rib installation Dimpling the skins


In the photo above left the FL-706B is attached to the inboard rib and the FL706A.  There is one locating hole in the rib at the aft end of the FL-706A and the rib.  There is a cleco in this hole in the photo.  The other cleco is a actually a cleco clamp.  The remaining holes had to be transferred to the rib and the FL-706A.  When the holes were all installed, the aft hole was enlarged to 1/4".  The control arm from the fuselage attaches here.  After this detail was complete the skins were dimpled by Ritchie (above right).


Flap parts after priming Internal ribs cleco'd to lower skin

In the photo above left, the right flap parts are primed and ready to assemble.  I did not photo the process this time but essentially I etched and alodined the parts prior to paint.  I scrubbed the parts with gray Scotchbrite during the etching process to make sure the parts were clean.  This scuffs them up a little which should help the primer to stick better.  At right above is a picture of the lower RH flap skin with the internal stiffeners cleco'd in.  There is an interesting fact about these stiffeners. They are identical to the left flap stiffeners.  The flanges face to the left on both flaps.  I am accustomed to the left being a mirror image to the right on airplanes with a Standard Airworthiness Certificate.

Riveting the internal stiffeners Laying flat on the workbench


Since the lower flap skin has a flange at the rear that serves as a spar and the ribs get riveted to this flange, care must be to keep from twisting this skin while riveting it together.  I placed it flat on the table (above left).  I riveted each rib to the vertical flange first.  I then riveted one fastener in each rib with the skin flat on the table.  I let the skin overhang the table just enough to expose one fastener hole in each rib while I installed a rivet in in these holes.  


Internal ribs installed Riveting the lower skin to the upper skin

The photo above left shows the lower skin with all of the ribs installed.  It is not twisted.  At the right above, I have started to rivet the lower skin to the upper skin.  Again the flap is laying flat on the table.  I continually checked to make sure that I did not twist the flap during the assembly.

View of flap looking inside Outboard end rib installation


Installing rivets in the lower skin to the upper skin was straight forward.  There was plenty of room to get my hand into the inside with a thin bucking bar (left above).  The outboard rib was also straight forward (above right).  A shim was required between it and the upper skin (below).



This shim (in the photo above) is installed between the outboard rib and the lower flange of the upper skin.  The arrow in the photo at right points to where the shim goes.  An identical shim goes in the same place in the inboard rib.

FL-706B cleco'd to inboard rib FL-706B riveted to the inboard rib


Before the inboard rib was installed, I attached the FL-706B to it.  The photo above left shows the two cleco'd together with a 1/4" bolt in the hole where the control arm attaches.  Prior to assembling these two parts a K1100-1/4 nut plate gets installed on this rib.  The photo above right shows the FL-706B and inboard rib ready to be installed.


Three blind fasteners in inboard rib Ready for the spar

There are two fasteners in the inboard rib that are behind the flange on the lower skin.  They have to have blind fasteners installed.  In the photo above left one fastener has been pulled and one is ready.  The third blind fastener has to be installed because the 1/4" nutplate will not allow a bucking bar below the hole.  The stem of a blind rivet is to the right in this photo.  I used CR3214-4-2 Cherry Max rivets in these three holes.  In the picture to the rightthe flap is ready for its spar.

FL-706A installation Blind fasteners in the spar to rib holes


Before the spar was installed the FL-706A had to be installed.  The first picture directly above shows the beginning of the installation.  The photo above right shows the installation of blind fasteners from the spar to the ribs.  Notice that the rivet puller barely fits.


Another shot of the blind fastener installation Rivet puller modifications

Here is another photo of the blind rivets (CR3213-4-2) during installation.  Above right is how much I had to grind off of the rivet puller to get it to fit inside the spar area.  I ground so much off that I was afraid that I would break it during the installation of the Cherry Max rivets.

Upper spar flange ready to be riveted Flap is ready for the hinge

After the spar was riveted to the ribs with blind fasteners the upper flange of the spar could be attached to the top skin (above left).  The photo above right was taken after the flange was riveted in.  Go to The RH flap and control, page 2 for the rest of the right flap assembly and installation.