SECTION 36: Flap
Jump to navigation
Jump to search
Before you start:
Build Instruction Updates
- Check for more recent updates here
Videos
- Van's RV 15 Flap Build — BackcountryRV-15
- Vans RV-15 Build Series — Episode 13: Building the Flaps — Average Joe's Airspeed Acres
- Installing the Flap Skins (Episode 14) — Average Joe's Airspeed Acres
- Building RV-15 airplane in a garage — Day 5: Flaps — Rivet Therapy
- Building RV-15 airplane in a garage — Day 6: Flaps — Rivet Therapy
- Building RV-15 airplane in a garage — Day 7: Flaps — Rivet Therapy
Modifications to Consider
- N/A
Special Tools / Supplies
- B2 fuel tank sealant
- 3/16" wooden dowels ×3 (for trailing edge bending radius guide)
- 12-ft poplar boards ×2 (for uniform TE squeeze cauls)
- Form blocks for the nose ribs: Great idea on ensuring correct curve on nose ribs. Trace the rib onto 3/4" MDF (no grain, so it won't split), band-saw it out, sand to shape on a belt sander and round the corners with a router. Make the block symmetrical so the same one works for left- and right-hand ribs — clamp the rib over the block to true up the flanges. The same approach works for the wing nose ribs. Source
- Half a rubber grommet super-glued to a normal flush set: or a short length of fuel hose slipped over the unset shank (reusable about a dozen times). The point is to keep the thin skins clamped so the rivet can't expand between the ribs. Source · fuel hose
- Curve-tip applicator syringe with the nozzle trimmed back, for laying the B2 bead in the aft flange (pg. 36-24) — load it by cutting the corner off a baggie of mixed sealant. Also recommend 6" palette knife for mixing and working sealant. See the Wheeler method. (VAF)
General Build Notes
- Mislabeled flap skins: Some early kits shipped with two right-side flap lower skins, one mislabeled as left (-001). Compare both lower skins side-by-side before drilling.
- All of the flap ribs are attached with solid rivets; at many locations, access is tough and both sides have thin aluminum. Some puckering is unavoidable with solid rivets, but I found using a piece of tubing over the shop head side of the rivet while squeezing really helped keep the joints flush and minimize puckering.
- In my kit, the AN426AD3-3.5 were actually -3. Measure your rivet length to ensure they are the correct ones.
- KAI Section 36 (Rev 1). There's lots to get backwards on the flap assemblies, especially the right side as no drawing is provided. Having just gone through this, I recommend the following sequence (following the KAIs of course):
- Cleco everything together on the left then the right side, including the brackets to the ribs and the ribs to the spar. Note the inside edge of the spar has a slight angle to it which matches the skin. Work from inside to outside (or vice versa) to match the right side mirroring the left side.
- Fit the cleco'd spar/rib/bracket assembly on the lower skin (both L and R sides) to ensure the holes match up and brackets fit through the slots in the skin. Then remove the assembly from the skin.
- Remove the nose ribs with brackets, individually, and rivet brackets to ribs per the instructions. Reinstall using clecos on to the spar.
- Go through and rivet everything per the instructions. I found using a 3x rivet gun with an offset 470AD4 rivet attachment extension, and tungsten bucking bar worked well.
Revision History
- R1 - Initial release to builders
Specific Build Notes:
Page 36-11 (R1)
- Spar may need to be rotated 180° on its long axis for inboard rib alignment. The lightening holes are irregular by design — this is intentional.
- Check the forward-most rivet hole in the angled inboard flange of FL-15007-001 against the FL-15001-001 skin (FL-15007-002 and FL-15001-002 on the right flap) before riveting — reported misaligned on both flaps. Do not force the tab when installing the skin (page 36-22); it twists the flange and puckers the skin. (VAF)
Page 36-11 through 36-20 (R1)
- Flap rib dimpling (NOT in KAI Section 36 R1): Flap top skins come pre-dimpled; TE flap ribs are NOT pre-dimpled and the KAI Rev contains no instruction to dimple them. You MUST dimple the flap ribs recommended before riveting. There are 12 total holes per Flap (one hole in each TE Rib) that need dimpling for CS4-4 countersunk blind rivets(page 36-26). The skin dimples will make it obvious which hole in the rib needs to be dimpled.
Page 36-22 (R1)
- Edge break (where accessible) trailing edge of LE Flap Skin on top near vortex generators.
Page 36-23 (R1)
- Note that the KAI says to rivet the tail ribs with LP4-3 rivets. The nose of a standard rivet gun is just a bit too large to fit under the cove where the pro seal bead is applied. If the rivet gun is pushed into the lower skin, it will appear that the rivet is sitting flush to the skin when it MAY NOT be flush. The solution is to drill a hole the size of the rivet mandrel in a piece of 1/8" stock and place it over the mandrel side of the rivet. This allows the rivet gun to be 1/8" farther from the lower skin and it will clear the cove when the rivet is flush.
Page 36-24 (R1)
- Adhere to Note to complete forming and check fit (36-25) prior to adding sealant.
- ProSeal for flap TE sealing: ~35g per flap (~40g if less precise)
- Rest the upper T.E. skin on 1.5" wood blocks it stays clear of the wet bead until it is lowered, then pull the blocks and cleco. (VAF)
Page 36-25 (R1)
- Edge break the Upper TE Skin on the leading edge on the bottom of Flap.
- Trailing edge bending: Use 3× 3/16" dowels inside the TE to maintain the correct bend radius. Use 2× 12-ft poplar board cauls for uniform squeeze across the full span.
- Alternative to the dowel method: a home-made brake from two boards joined with door hinges - rip one edge of each board flat so the hinges seat, use paint stir sticks between the boards to set the gap, and drive the hinge screws with deck screws. Reported to give a clean bend. A Vix Bit is the easy way to center the pilot holes in the hinge leaves. Source