Fri Jun 14, 2013 11:19 pm
Well, seeing that I have not offended you with my previous posts... I do happen to have a little experience trailering experimental airplanes.
There are three general principles:
1) have everything restrained softly, certainly not flopping around but not lashed down hard hard hard to the trailer. The trailer flexes and vibrates. Unless your trailer is a converted ConEx container, it is going to flex. Even if it doesn't flex it is going to vibrate, undulate, and bounce on the springs. Plain steel leaf springs set up a resonant frequency. Very few trailers have real shock absorbers. If you can use one of those for your trip, do it... but most don't. The important thing to understand is that if you firmly bolt and clamp a 50 pound aluminum pop-riveted .020" skinned Zenair 701 or 750 wing panel to a trailer frame, and the road vibrations are flexing that heavy trailer frame, your Zenair wing is going to have the equivalent of 5,000 hours on it in the best case, and visible damage in the worst case.
2) do NOT support the airplane in the trailer by any of the bolt fittings! You are taking enough risk on those fittings with normal flight loads, and trailer-thrashing is just adding two or three more bullets to the revolver in your Russian Roulette game. It's fine to support the fuselage on it's tires, with big chocks SCREWED into the trailer floor and wide nylon straps over the tires. But see 3) below. The wings should be hung leading edge down, on the sidewalls of the trailer, hung by nylon straps looped chordwise around the wing at four spanwise locations (not just one at the root and one at the tip). There should be dense foam pads between the wing leading edge and nylon straps, and these pads should be securely taped or lashed to the wing so they do not work their way loose.
3) an engine bouncing up and down 3 million times, with nothing supporting it but the engine mount cantilevered off the firewall, is very very bad. I once owned a small experimental (Cassutt) which is a traditional steel tube fuselage and engine mount. The weight of the engine bouncing up and down during trailering had caused repetitive movement stress, flexure, hardening, and ultimate failure of the STEEL TUBES. Now imagine the same type of engine weight loads bouncing up and down against the pop rivets and thin sheet metal firewall and forward fuselage structure of a Zenair. So my advice is to strap the tires down to the floor, install very large wheel chocks on all 3 tires, and then build up a padded support to take the engine weight off the fuselage. This can be as simple as a stack of plastic milk crates under the engine with a pillow wedged underneath the engine, and everything screwed down to the floor so it won't walk around.
Even after securing the aircraft correctly, with all aircraft trailering, you still have one major responsibility. Go back there and personally check your load every 150-200 miles. It's a pain in the ass, but you will be absolutely surprised at how much things will move around no matter how well you try to secure it. You have just spent a good chunk of your money on this airplane, and then you are going to ask it to protect your life and your family's lives. Stress cracks in aluminum can be so small that they are not easily seen. Repeated flexure, work hardening, and subsequent impending failure of a metal part will very often not be visible to the naked eye. Small mistakes and oversights in the trailering stage can become huge maintenance or repair problems as soon as you unload the aircraft. Extra time and energy securing and transporting the aircraft will pay you tenfold in preventing seen and unseen damage.
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