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Building Tips and technical articles. => Building techniques => Topic started by: Fred Quedenfeld jr on May 14, 2019, 11:48:05 AM
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For an airplane like the Humungas
push rod goes from belcrank right to elevator
How do you install the fancy carbon push rod
do you cut open all the former than glue them back in
Thanks
Fred Q
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How far along are you, Fred?
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Fred,
I usually cut holes in the formers before I start framing up the fuse. With the carbon fiber rods you can make generous size holes and not have to worry about the rod flexing. If you look at the plan profile you should get an idea where they should go vertically on the former. Sometimes the first couple formers after the rod exits the center sheeting will have the hole right down on it. If you feel it is a little weak just use thicker wood or a cross brace. Make sure the formers have the grain going across the width not vertical.
Best, DennisT
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Another method is to get a piece of carbon tube that will slip over the metal rod then solder a threaded coupler on the end capturing the tube. I'm not a fan of fair leads.
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I just got done dealing with this problem and it's very fussy even on a flapped airplane, at least if you aren't willing to cut access holes, which I try to avoid at all costs.
I hadn't really thought about it too much for a built-up fuse unflapped airplane. You either have to build the formers and leave sufficient clearance to slide the pushrod all the way to the back through the wing cut-out, or do like they used to and the way it is shown on the Nobler plans - build the fuselage around the pushrod. I don't like access holes through the fuselage, at least not with IC engines, too much loss of rigidity, and also prone to fatigue at the corners like a DeHavilland Comet.
For the wing cutout method, i would be tempted to make the diagonal cuts to remove the bottom of the fuselage sloping towards the front rather than the back. that makes it easier to get the leading edge in without having the pushrod go in at a large angle.
I haven't built the formers as solid parts in a long time, all of my formers are built-up and have capacious openings in the middle. They are built from 1/16x3/8 strip with overlaps at the corners. They are also have diagonal braces on the top and bottom edges. I think Sparky posted a picture of my crashed airplane from the 2005 NATs where you could see it. Also on Jim Aron's airplane, after he crashed that, both are posted somewhere.
Brett
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use a Russian Z bend at the bell crank and u can remove and install until fuse is totally finished
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I have no idea what a "Russian Z-bend" might be. A picture or sketch might help. IMO, if you can get a "Z-bend" through your BC or elevator horn, it's too sloppy a fit.
It doesn't really matter a lot, but the Humongus usually has an external elevator horn, so it should be easy enough to slid the pushrod in from the tail and bolt it to the bellcrank and then elevator horn...if you plan your building sequences as well as you should. Some of the latest take-apart PA planes have the fin/rudder come off along with an angled bit of the fuselage. That fuselage bit is from the stab TE forward and down to where one might mount the tailwheel strut...forward at about 45 degrees. This gives good support/strength to the stabilizer mounting with great access to the elevator horn...and would make it duck soup to slide the pushrod in. Assuming you're using ball rod ends, and you plan for access to the BC from top and bottom, you're golden. y1 Steve