Terence Teer wrote: >I’m adding an autopilot and will need trim availability. I’m thinking Bowden >cable and trim lever.
A Bowden cable (manual push-pull arrangement) is exactly what's called out in the plans. This was sold by Rand Robinson in the form of a "ny-rod" plastic pushrod in a plastic housing, straight from your local RC model store. This is a somewhat low-friction design, but it quite springy due to the low stiffness of the housing and flexible pushrod. This leads to a very springy trim tab, which as Jeff pointed out, is not a good thing. And after 20-30 years, the housing cracks and you have nothing at all! I second the Ray Allen trim system. It's quite stiff, by comparison. There are some details on my trim tab installation at http://www.n56ml.com/trimtab/index.html. This setup easily handles all of the CG changes that I ever need on N56ML, with probably half the range unused. I'm happy to keep that in my back pocket though, as you never know when landing without an elevator or something similar will make me thankful that I have the capability. One point to make on the Ray Allen system...use shielded cable to run the wires from the switch and display units back to the servo, and ground one end of the shield, and avoid close proximity to the radio and transponder antenna cables. When keying the mic, the trim position display LEDs goes bright and dim, and eventually it fries them! My middle three LEDs are cooked, and it's because those three LEDs have been lit while the transmitter was broadcasting. The same thing happened on N891JF, and I've heard several other folks have had the same problem. Keep those wires shielded and isolated from RFI (radio frequency interference). It's not a big deal to not know exactly where the trim tab is anyway, as it's so easy to overcome by stick pressure anyway. It is kind of nice to set it neutral on takeoff, as the plane will takeoff by itself with no stick pressure from the pilot. That's good advice that Troy Petteway gave me for my first flight...."just keep it centered on the runway and when it's ready to fly it will lift off and climb. You shouldn't have to pull back on the stick to make it climb...it will do that all by itself". See http://www.n56ml.com/trimtab/index.html .... Mark Langford, Harvest, AL ML "at" N56ML.com www.N56ML.com _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
