Rudder tip fairing question

[thehagg501]

The instructions :
Deburr and dimple the rudder tip attach holes in theRudder Assembly for CS4-4 blind rivets as shown in Figure 2. Machine countersink the holes in the rudder tip fairing for the dimplesin the Rudder Assembly.Step 5: Cleco then rivet the R-909 Rudder Tip Fairing to the Rudder Assembly using the rivets called out in Figure 2.

The question I have is, when I countersink the fiberglass tip the strength to hold a pull rivet in this situation seems weak. Wont the rivet expand through the glass to the alum skin then snap? I'm thinking there should be some blind rivet backup washers.

 

[georgemohr]

I backed all of the fiberglass rivets with washers that I lightly glassed into the flange. Maybe overkill?

 

[thehagg501]

Exactly what I was thinking

 

[TechSupport]

I used Hysol epoxy between the fiberglass and the aluminum, pull rivet just to fill the hole and provide a mechanical stop against shearing movement if the epoxy were to separate. I did not put anything on the back side and it did pull the fiberglass enough to bring it up against the metal while it cured. I didn't want the extra weight aft of the pivot point but I did smooth the transition between the rudder and the fairing with epoxy+micro. dealer's choice, many ways to cut the cheese on this one.

 

[TASEsq]

I glued alu strips along the line of rivet holes. Same idea as the washers, i just thought this was easier.

12-05: Elevator, Rudder, VS and HS tip fairings

A Build Log detailing the build of a Vans RV-14

tasrv14.blogspot.com

 

[thehagg501]

I glued alu strips along the line of rivet holes. Same idea as the washers, i just thought this was easier.

12-05: Elevator, Rudder, VS and HS tip fairings

A Build Log detailing the build of a Vans RV-14

tasrv14.blogspot.com

What did you use to hold the straps to the tips?

 

[TASEsq]

What did you use to hold the straps to the tips?

Epoxy and flox - mostly as a filler to even out the rough surface. All the strength is in the alu strip and rivets. The backs of the strips are unprimed and I scuffed the fibreglass surface with my dremel, vacuumed, stiff brush / acetone, iso then glued it up.