Q-talk 96 - Safety Wire Hose Clamps
- Category: Q-Talk Articles
- Published: Wednesday, 23 December 2009 16:24
- Written by Terry Crouch
- Hits: 2117
Terry: How can you be sure hose clamps stay clamped when it really counts, like on the Revmaster induction system?
Q-Talk: I don't know. Tighten them often, I guess.
Terry: Why not safety wire them?
Q-Talk: How would you do that?
Terry: Cut about a 10" piece of .020-.032 stainless steel safety wire, depending on the size of the clamp and fold it in half, creating a midpoint in the wire. Insert the safety wire into the clamping mechanism by passing the cut ends to the right and left of the screw, through the clamp body and out the other side. The fold of the wire will fit inside the groove in the screw head. Twist the ends of the wire together until they are tight. Clip excess wire, leaving only a small tail to be bent out of the way. If you are unable to insert both ends of the wire at the same time, make one side the wire longer than the other and insert individually, starting with the hardest side first.
Terry: Did you know that the Quickie and Q2 are the only Rutan airplanes, that I am aware of, that attaches the elevator to the torque tube by driving only the foam?
Q-Talk: No. How is the elevator attached to the torque tube on other planes?
Terry: The Varieze and Long-EZ elevators have bolts that clamp the glass to the torque tube.
Q-Talk: Oh. How did you do that on your Quickie?
Terry: First, you remove the inboard fiberglass end caps and remove the foam at least .625" to .75" beyond of the torque tube attach bolt. Going outboard beyond these bolt holes is important because you want to seal the bolt hole so no fuel can make its way into the elevator foam core. Be careful when you remove the foam because the unsupported glass surfaces of the elevator can be crushed very easily. Be sure to remove the foam between the leading edge of the elevator and the torque tube. When you are done, the foam surface should be level from the leading edge of the elevator back to the trailing edge. Prepare the torque tube, as well as the inside surfaces of the exposed elevator skin, for glassing. Cover the inboard end of the torque tube with tape to keep epoxy and flox from getting inside. Apply a micro slurry on the foam like other glass to foam layups. Cut two pieces of BID large enough to cover the inside elevator skins and the foam surface, too.
Q-Talk: What about the torque tube?
Terry: The BID will go up each side of the exposed torque tube and temporarily cover the inboard end of the tube previously covered with tape.
Q-Talk: So let me get this straight. You lay the BID down the inside surfaces of the elevator skin walls, along the floor of the exposed foam inner core and over the torque tube like a small ski mask?
Terry: Right. When you have the glass in place, scissor trim it as close to the inboard edges of the elevator skins as you can Prepare a good-sized batch of flox to fill in the blunt leading edge area around the torque tube. If you have already drilled a hole for die elevator torque tube AN4 bolt, sharpen the end of a V" x 5-6" long hardware store bolt, apply a release and pass through the hole. This will aid in locating the boltholes once cured. The sharpened point will help penetrate the layers of BID. Compress the flox around the torque tube, filling the gap between the leading edge of the elevator and the torque tube. Place 2 layers of BID along the aft surface of torque tube and tie into the upper and lower inside surfaces of the elevator skins to help maintain a tapered shape. Make sure the bolt can compress the torque tube slightly to clamp against the steel tube. Neglecting to do this will eventually elongate the holes if there is any extra bolt clearance.
Knife trim the glass when in the green state and let it completely cure. Use a Dremel with a sanding drum and a shop vacuum to clean the edges of the glass to their original inboard position. Level the floxed area with the inboard end of the torque tube and the inboard edges of the elevator skin. Use the leverage of a wrench on the hex head of the long bolt to loosen and work out of the hole. When free, counter bore the hole large enough for the AN bolt head and nut as well as the socket needed to tighten them down. Do not drill all the way through to the torque tube. Stop before you reach the BID attached to the torque tube. That will allow a positive grip of both the torque tube and the glass. When done, prime and paint the new surfaces. Do not worry about adding fill to the area because it will be visible only when the elevators are removed.
Q-Talk: That sounds easy to do. Should it be done on the outboard areas of the elevator as well?
Terry: That should not be necessary because you can drive the entire elevator from that inboard rib.
Q-Talk: Should we be doing this to our ailerons, too?
Terry: On my Quickie I put some additional rivets on the leading edge of the aileron because the aileron skin was bonded directly to the torque tube.
Ed Note: The method Terry described above has the advantage of blocking access of fuel to the foam via the torque tube bolthole as well as providing significant surface contact. I performed this modification on my painted elevators and it only took about 4 hours to complete.
There are other alternatives to ensuring your elevator torque tube does not separate from the elevator foam core. For example, drilling several holes through the torque tube from the upper to lower surfaces and filling the holes with epoxy and wooden dowels.
You can order a printed copy of Q-talk #96 by using the Q-talk Back Issue Order Page.