Screws for lower wing/fuselage intersection fairing

[czechsix]

RV-14 plans page 29-18 shows K1000-08D nutplates along the edge of the F-01484 bottom fuselage skin where the lower wing intersection fairing attaches, indicating panhead screws in this location. K1100 nutplates for flush #8 screws are used everywhere else on the wing/fuselage intersection fairings, and I can't see why they couldn't be used along the F-01484 bottom skin as well.

Looking at pics of Van's demo airplanes, it appears their original RV-14A prototype uses flush screws in this location, but the RV-14 demo and the silver RV-14A demo (both of which were built to production parts/plans) use the panhead screws per the plans, so presumably Van's had a reason for this change...anyone know why? Maybe the panheads make the fairing lay down flatter with less 'pucker' in between the screws, or is there something else I'm missing?

 

[PaulvS]

I don't know what is Van's rationale for changing the screw type on the RV-14/A, however it is standard practice amongst RV builders in my region to use pan head or truss head screws on the belly/wing intersections (instead of countersunk) because there can be some relative movement between the skins (e.g. during aerobatics) and the nested dimples interfere with this natural flexing.

 

[czechsix]

it is standard practice amongst RV builders in my region to use pan head or truss head screws on the belly/wing intersections (instead of countersunk) because there can be some relative movement between the skins (e.g. during aerobatics) and the nested dimples interfere with this natural flexing.

Interesting, never heard of this. My RV-8A bottom skin attached to the wings with flush screws and I did a fair amount of acro with it, and never observed any cracks or signs of stress in that area. Even if you use panhead or truss head screws, if you wanted to allow movement between the intersection fairing and wing/fuselage attach points, you'd need to avoid tightening them completely. I would think Van's would provide such guidance if that was their intent.

 

[bjdecker]

Dimpled/Countersunk

RV-7 belly skins to wing (W-704-L/R) are all AN509-8R8 or similar (flush head) into platenuts, either K1100-08 (dimpled under dimpled) or K1000-08 (not dimpled under countersunk).

See RV-7 DWG 38

 

[USN bullet]

Screws for Lower wing/fuselage intersection fairing

I'm working on that area on my RV-14A and page 41-4 indicates that there are holes which are not dimpled. That leads me to belive those non dimpled holes will get pan head (not flush) screws. The non dimpled holes are next to the fuselage.
Cheers
John

 

[KeithB]

RV-14 plans page 29-18 shows K1000-08D nutplates along the edge of the F-01484 bottom fuselage skin where the lower wing intersection fairing attaches, indicating panhead screws in this location. K1100 nutplates for flush #8 screws are used everywhere else on the wing/fuselage intersection fairings, and I can't see why they couldn't be used along the F-01484 bottom skin as well.

Looking at pics of Van's demo airplanes, it appears their original RV-14A prototype uses flush screws in this location, but the RV-14 demo and the silver RV-14A demo (both of which were built to production parts/plans) use the panhead screws per the plans, so presumably Van's had a reason for this change...anyone know why? Maybe the panheads make the fairing lay down flatter with less 'pucker' in between the screws, or is there something else I'm missing?

E (see E’s RV-14A blog) made this retrofit to his flying RV-14A documented here (about 1/2 way down the page) https://rv-14a.blogspot.com/2020/11/