Wheel Well Refinish

The objective is to make covers for the two holes pictured above [think blue].
The photos above were taken during the wheel well refinish project on my Comanche 400.

Wheel Well Refinish

Also make covers for the kidney-shaped opening in the root rib.
These covers will benefit cabin-draft reduction.

Cabin Breeze Reduction
Cabin Breeze Reduction Sealer

Use “duct seal” here which will also reduce cabin draft somewhat, and possibly keep wildlife from nesting inside the fuselage.

For reference photos see top two at top of this page. Airflow creates high pressure under the wing and consequently in the wheel wells. There are 3 openings located in each wheel well to be blocked. One is at the wing-root rib, a kidney-shaped cover; the other 2 are round covers. One is just outboard the MLG strut; the other is behind the wheel-well splash shield. If you give some thought to this issue you’ll discover this approach is also a speed-mod. Remember Bernoulli’s principle? The airflow through these openings entering through the wheel wells to exit points is a total waste of energy; except possibly to vent odor from mouse droppings.

The primary interest here will probably be cabin draft-reduction, although I prefer the speed-mod benefit. The kidney-shaped cover will be the most effective in this cabin- draft reduction approach. There is also a cover that is supposed to be in place where the main spar and conduit penetrate the fuselage. If they are missing there will be a very large draft in the cabin. See the photo above outlining the cover that should be found.

Another point, although quite small, is the small area around the conduit entry/exit thru the fuselage; plug those areas with some sealant. I use “duct seal”, a product of Gardner Bender – Google™ it – about $2 from various sources; sorry to say Home Depot no longer carries this stuff. Or possibly purchase at an air conditioning/heating establishment. See the sealer photo above.

Now let’s proceed. Use a piece of heavy poster paper and cut to the approximate size, of the cover for the root rib, plus some margin. Measure the conduit diameter [7/8”?] and mark the hole location; use a circle template to draw the hole. Slit from an edge of the pattern to the hole; then accurately cut the hole.
Position the rough-cut pattern over the conduit and using your fingers make an impression of the edge of the root-rib opening onto the poster paper. Now you almost have a pattern. Using scissors, cut on the outline of the rib-opening impression, then lay this pattern onto  another piece of poster paper and add a 3/8” margin; now you have a new pattern. Test-fit the pattern and trim as necessary before making the final product. The hole for the conduit should leave a bit of room to avoid contact, or make the hole larger [1-1/4”] like my photo for a grommet AN931-14-20. Note – the rib cut-out covers for the left side and right side
are identical pieces, just mirror images.

Two options; if you plan to install this cover with an installed conduit use option 1.

Option 1 – make a 2-piece cover split diametrically through the conduit hole; add 1/2″ overlap at the split. Use pop rivets at the overlap to secure.

Option 2 – for installing with new conduits, make this a one-piece cover as shown in the photograph on the bottom of page 1.

Use 2024-T3, 0.032″ aluminum for all the fabricated covers. Use a hole saw for cutting the hole for the conduit opening in those covers. Install the covers using “3M Scotch-Mount double coated acrylic foam tape”. You can find this stuff on-line, Google™ “3M ScotchMount, or try an automotive store [NAPA]. It comes in 1/2″ width which is too wide to apply neatly; cut to 1/4” width. This stuff has an acrylic adhesive which is tenacious and thusly works well on clean surfaces. Nix the silicone-adhesive method here.

Another hint – adhere some baffle material at the openings where the aileron cables enter/exit the fuselage; likewise flap cables [conduits on the 400] and step-lock cable.

Baffle Materials