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Posted

One other very important thing. I want to reiterate that I am 100% convinced there is no risk of wing "failure". An 18 inch plywood stiffener is in the correct place in the wing and now the wings are no longer than STD MKIV wings. The wing does not flex anywhere near a concern of failure. It does appear to flex more than my other Avids.

What does concern me is the stick forces required to move the flapperons in flight that are not there on the ground. That may also have something to do with the push pull cables which I have no previous experience with. The stick/mixer/push pull cable setup has a GREAT deal more play than the more direct linked regular Avids. This could also have something to do with the stick forces. There may be drag in the cables when force is applied that is not in them when not under load.

There are a LOT of variables to sort through. It could well end up being a combination of things and not one root cause.

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Posted (edited)

Chris, 

The cable forces can vary depending on the manufacturer.  Mine are a little easier to move that Jack's plane and the first set I had were the best! (But got broken as I sat out a windstorm with the wing covers on not letting the flaperons return to neutral.)  Anyway the comparison should be between the force needed on the ground vs. force needed in flight.  There is more slop than the push/pull tubes but I was able to minimize it by carefully adjusting as much slop out of the mixer and stick assemblies with washers and snug castle nuts.

I wonder if you could build in a little preload flex in your flaperon hangar mounting so with in flight wing flex they would be straight?

Edited by SuberAvid

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Posted (edited)

I have thought about cutting the wings off to the 144 inch standard length, but honestly I LOVE the additional performance that 18 inches of extra wing on each side brings to the table. It really is awesome even with the wingtips cut off! (And it now has the same wingspan as a std MKIV so it now fits in my hangar easily. It barely fit with the wingtips on. So.... I will only cut the wings as a last resort If there is nothing else that works. if I should end up doing that it looks like I may I have an extra set of wingtips available to use.

I have thought about re-mounting the flapperons on the hangars so they are "pre-stressed" in the negative direction on the ground and become neutral in flight. But there is the issue of how to do that safely because of the existing holes in the flap hangars. But honestly, I need to fly in a MKiV (Which I do have access to) and see what wing flex there is. There may be some and I am not remembering correctly. It's been 5 LONG years since I was flying regularly in the magnum and many more since I owned my MKIV. There may be flex I don't remember.

Right now I am focusing on cable drag as a contributor and trying to figure out if there is any way to reduce play. I can quite literally move one flapperon 3/4 inch up and down at the trailing edge before the other flapperon starts to move! There is less play when moving the stick, because of course the stick is in the "middle" of all of the play in the linkage and cables.

I seldom use flaps landing or taking off as this plane lands super slow b/c of the extra lifting bay on the wing. I have thought about getting rid of the mixer as it is now and running flapperons more directly to reduce some play. My estimate is that at least half of the play is from the mixer/stick linkages and the other half is push pull cable. 

I do not want to cut the wings off unless there are no other workable solutions.

The plane keeps getting better and better as I work through these issues. Right now it is well past the more fun to fly than work on phase of rigging, so things are going in the right direction. At first it was scary, now it is fun to fly, but I have clear memories of my Magnum and original MKIV and this plane is not as good as either of them yet.

Edited by Chris Bolkan
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Posted

My friend Ron took these yesterday from his mkiv when we were flying around the farm fields after work.

466EE19C-2853-493D-AB5C-7B6FB9A9A4D2.jpeg

D15EE81C-F502-402E-8295-42F3136D08B7.jpeg

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Posted

That just looks fun!

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Posted

Any updated flight reports or fixes for us?

:BC:

 

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Posted

I have just been flying and working out minor issues that happen with any new build. I have put about 25 hours on so far, and plan to fly through this month. Then I will take take it out of commission to do some more bigger projects in the winter. It will kill me up to take it out of service since I have not had my own plane to fly for so long, but there is still all of the cosmetic work to complete like painting the cowl, replacing the metal door bottoms with clear plastic, re-positioning the battery further aft to get rid of the lead I put in the tail, replacing or enhancing the wing spar stiffeners to reduce wing flex, capping the wing ends properly, rebuild the gearbox in the engine as it was beaten up pretty badly by a prop with too much inertia for the first 300 hours of its life, and touch up painting the wings and fuse. Hopefully that work won't take long. In the mean time I'm just flying and enjoying.

Even tho I prefer to fly a tail wheel configuration, this plane is tri gear and I couldn't be happier with the rans nosewheel conversion. I run low pressure in the 21 inch mains and in the 600X6 nosewheel. The plane just cushes over bumps and uneven terrain. The big surprise is how little rolling over rough terrain kick back to the rudder pedals. It is amazingly smooth. That was one of my concerns with this untested nosewheel configuration.

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