RV-8 Flaps differences between DWG RV8-14A and RV8-14B?

[Jacob@advanced]

Hey Everyone! Working on an RV-8 and we discovered during the condition inspection the flap rods where chaffing on the fuselage pretty significantly.
When I was reading through the build manual and drawings I see the build manual references to DWG RV8-14B for building the flaps and then DWG RV8-80 for attaching the flap rods to the flaps. I am also seeing some references to DWG RV8-14A but not in the flap build or attachment. This airplane's flaps, specifically the end rib (FL-704) web direction and Plate (FL-406B) attachment seem to be accomplished as DWG 14A reflects.. See photo and dwgs. Furthering, I cannot seem to find any reference for how to attach the flap rods to the flaps if they are completed how 14A reflects. I spoke with VANS and i've received two opposite answers (no the flaps are wrong and yes that's fine). Does anyone know what the history is on these drawings? Is 14A the "old way" and 14B the new way or was 14A inserted for reference to another item but the flaps should be completed by 14B? Is it acceptable to have the "14A" completed flaps on an RV-8? And is there an attachment reference for the flap rods for "14A flaps" (currently the 90 degree rod end has a nylock that is almost impossible to get purchase on aside from a crows foot)? Thanks!!

 

[fl-mike]

You're seeing the evolution from the early non-prepunched kits to the prepunched and maybe the wing update.
Your flaps have the built-up root rib with the angle and loose nut vs the later design that uses an anchor nut and a FL-706B plate (pre-punched).
Both are "correct".

I, and others have replaced that modified rod-end with a standard CM-4M so that a standard bolt can be used in the joint, along with large washer etc. per good practice on rod-ends. This also allows you to use a large diameter spacer and longer bolt to move the pushrod in a bit to avoid that rubbing or enlarging the fuselage hole a bunch. Full disclosure: I have no analysis to support the the spacer is a safe modification. The clamp-up of that joint is surely critical (no "rocking" of the bolt)

 

[scsmith]

You're seeing the evolution from the early non-prepunched kits to the prepunched and maybe the wing update.
Your flaps have the built-up root rib with the angle and loose nut vs the later design that uses an anchor nut and a FL-706B plate (pre-punched).
Both are "correct".

I, and others have replaced that modified rod-end with a standard CM-4M so that a standard bolt can be used in the joint, along with large washer etc. per good practice on rod-ends. This also allows you to use a large diameter spacer and longer bolt to move the pushrod in a bit to avoid that rubbing or enlarging the fuselage hole a bunch. Full disclosure: I have no analysis to support the the spacer is a safe modification. The clamp-up of that joint is surely critical (no "rocking" of the bolt)

I second everything Mike has said here. When I got my initial airworthiness inspection by the DAR (Dave Morss), the the VERY FIRST thing he looked at was the flap attachment, and he was amazed that I had avoided the integral stud+rod-end fitting that has a potential uncaptured failure mode and instead used a standard rod end with a large AN970 washer and AN bolt, and a spacer of the proper length to get the pushrod to run in the middle of the hole.

Yes, the spacer is longer than the original set-up. The structural integrity of this assembly depends on the end faces of the spacer to be cut very square, with sufficient wall thickness to accept the full bolt torque pre-load. I had to make a special open-end wrench to get inside and hold the nut while the bolt is torqued. The pre-load torque here is critical to clamping everything together without putting any bending moment into the bolt itself.

 

[BuckWynd]

For what it's worth, this is what I did to move my flap actuator rod attach-point inboard, in order to a. minimize the size of the hole in the fuselage (or, in your case, improve the geometry to prevent rubbing on the edge of an existing hole), b. utilize slightly beefier hexagonal flap actuator rods (not shown), and c. utilize a CM-4M rod end bearing with proper capture washers.

 

[Jacob@advanced]

Thank you guys! I already planned to amend the rods to a beefer stock, but will move to the CM-4M on both ends with the spacer on the flap end. I'm very surprised Van's has nothing about this in their instructions or as a buletin.