Adding Flaps to the Hangar 9 Super Decathlon

[JimD]

Having now modified three sets of wings to add flaps to this model, I guess I qualify as somewhat of an expert now. If you own one of these models, you know that it comes with a set of mystery servo mounts. After careful inspection, I determined that the wing has cutouts for these servo mounts so they can be installed for the purpose of actuating flaps.

On the first set of wings, I had no idea what the structure inside the wing was like. Now, after three times, I know very well what is inside and I know where to cut. Make these measurements and cut on the tip side and trailing edge side of the lines.



A razor saw is the best tool for making the cuts.



Carefully cut from both sides until the "flap" piece is detached.



Use a block sander and flat sand the trailing edge secton.

[JimD]

As you can see, the covering was totally removed from the wings on this set of wings.On the second set, I was able to save the covering (mostly) and on the first set, I stripped and recovered the top of the wings. I wanted to change the trim scheme on this model anyway, so the covering was totally removed for that purpose. As can be seen, there are pre-installed balsa blocks for the flap hinge points.A section of balsa was added for the flap hinge attachment point.

Four pieces of 1/4" balsa sheet was glued together and cut to fit in one of the rib bays.3/32" cap sheeting was added over this section to bring it up flush with the surface.



(next pictures are from prior wing mod)

A 1/4" section was removed for the front of the flap section (note shim under trailing edge).



A piece of 1/4" thick balsa sheet was cut to size and glued to the front of the flap section.



Then a 45^o section was cut away.

[JimD]

Another 1/4" piece of balsa sheeting was cut to fit over this cut.





This was them trimmed and sanded off round.

A piece of triangle stock was added to the top trailing edge of the wing and sanded to the contour of the top of the wing.



Hinges were added at the bottom.

[JimD]

Order an extra hardware set from Hangar 9 and use the aileron pushrod linkage to hook up the flaps to the servo.

[stevekremer]

Thanks Jim
Very nice article

Steve K

[Swiss1]

Did you double up on the hinges at each point, and are those Robart?

Jeremy and Ben
SCC AAA TT

[JimD]

We used two Robart 3/16" hinge points at each of the four hinge locations. Center to center, the hinge points are spaced about 5/16" apart. The control horn bolt is positioned 1-5/16" back from front bottom edge of the flap. Hinge points go into trailing edge and flap edge at a 45 degree angle.

The linkage needed comes in this group of parts:

http://www.horizonhobby.com/linkage-set%3A-super-decathlon-100cc-han107012

Matching control horn bolts and lock nuts do not seem to be available in the accessory parts, so the control horn bolts we used are 8-32 tapered head 2-1/4" long with a plate washer and nylon insert lock nut to secure them in

[JimD]

Construction Steps for 4th Wing to be Modified Starts Here:

Steve & Kevin Kremer recently became the new owners of a Hangar 9 Super Decathlon Tow Plane. One problem, it didn't have flaps...so here we go again!

On Decathlon #1, we ended up removing the covering from the entire upper side of the wing and patched the underside where it was not visible.

On Decathlon #2, we saved the covering on the main part of the wing but had to make patches along the hinge line that didn't look all that great.

On Decathlon #3, we completely stripped the wings, including the tips, and changed the color scheme entirely.

On Decathlon #4, we want to save the main wing covering and don't want patches like #2. In order to accomplish this, we decided to make the front edge of the flap square (like the HH Blanik flaps). This should avoid having to make a visible line in the covering where a patch was added.

*** In all 4 cases, the flap section covering was completely removed so the internal structure could be modified. ***

The cut line was drawn on the covering with an Ultra Fine Line Sharpie marker. the hinge line is 6-1/8" forward of the trailing edge and the root side of the flap is 4-5/8" out for the root rib.



We used a #11 X-Acto knife to cut along the Sharpie line and then pealed the covering off.



Blocks for the hinge points can be seen inside the structure.



We stabbed through the balsa sheeting to determine the exact location the internal plywood section that will become the new trailing edge of the main wing.



Next we used our razor saw to cut down though the internal structure along the Sharpie line.



Things are going to look a little ugly when you are able to break the flap section away from the main wing...don't panic!

[JimD]

Using the razor saw and knife, whittle away as much of the stubs as you can then block sand the trailing edge smooth.




We made a jig for our table top band saw and cut away 1/4" from the front side of the flap section.



Here you can see the section removed from the flap and the smooth trailing edge.



The covering over the flap servo mount was cut open diagonally corner to corner.



Covering was ironed down with a MonoKote trim tool iron.

[JimD]

Structure needs to be added to the flap section for the control horn. Make a paper rib template and then cut out three 1/4" thick ribs using this pattern. Also cut a piece of 1/4" thick balsa to cap the front face of the flap.



The centerline for the control horn is 11" from the root side of the flap. Glue the three ribs together and then insert them into the flap. Then glue on the 1/4" thick piece to finish out the new flap. Sand to blend in the surfaces.



Use 3/32' balsa sheeting to "cap" this wide rib section and flat sand the surfaces to blend in the cap sheeting with the rest of the flap.

Now to see if we can save the main wing covering!

The main wing covering along the hinge line area was gently separated from the underlying structure and a piece of new covering was slipped in under the original covering. covering iron was used to reattach the covering and to seal the new covering down over the trailing edge.



Okay...looks like it worked!

[JimD]

Final step is hinging. Mark the location of the internal balsa blocks and use a Dremel tool with a cone bit to make starter holes for the hinges. We like to use two hinge points at each of the four locations. A 3/16" drill bit is then used to deepen the starter holes for the Robart Hinge Points. Note that these go in at a 45^o angle to the wing cord.



Transfer the hinge locations from the main wing onto the flap section and drill out the hinge holes as was done on the main wing.



All done with building, now to recover the flap section, add the hinge control horn and mount the flap servo.

[stevekremer]

Jim,

This is awsome. Thanks for adding flaps for us!!!!! Can't wait to tow!

Steve K

[Sinkhappens86]

Looks great Jim, your work is always impressive. Thanks again, looking forward to flying it!

[JimD]

...and here is the finished product!

[Rich Kardian]

Hi Jim,
Very Very Nice and well done set of instructions.

So - - How does it feel to be an Expert in a hundred different ways ???

You are one of my Hero,s Buddy.

Rich & Rolly