Sign in to follow this  
Followers 0

Just joined the Fat Avid Club

216 posts in this topic

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.

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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
1 person likes this

Share this post


Link to post
Share on other sites

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

2 people like this

Share this post


Link to post
Share on other sites

Posted

That just looks fun!

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Any updated flight reports or fixes for us?

:BC:

 

Share this post


Link to post
Share on other sites

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.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Been working on the Avid this winter after flying it in the fall. Cleaned up a lot of mechanical and electrical loose ends and now working on cosmetics. Here are some pics. One is of plane in hangar as I was flying it this last fall. The other pics are of fabric work and painting cowl. i still have to figure out how to best bring blue trim cosmetically through the cowl. I also replace the metal on the bottom of the doors with lexan and added some cowl windows. Those two things will really improve the already great visibility.

Next project is to try an replace wing spar stiffeners in the wings, cap the wing tips and cosmetically "finish" the wings.

IMG_0284.JPG

IMG_0524.JPG

IMG_0530.JPG

IMG_0532.JPG

IMG_0535.JPG

IMG_0536.JPG

IMG_0537.JPG

Share this post


Link to post
Share on other sites

Posted

I realized I never posted pics of the wings with tips cut off. The wingspan was 33 feet or so till I cut the tips off. With the tips cut off wingspan is just a bit wider than 30 feet (like a standard Avid) feet because of the wider fuselage.

Problem with the 33 foot wingspan is that the strut was not moved out accordingly so the portion of the wing beyond the strut was heavily cantilevered leading to the wingtip bending up too much under load. I do not believe it is/was a structural issue, but it did seriously impact the flapperons.

The first pics show my plane next to my friend's 912 MKIV. You can see that my plane has an extra 18 inch "bay" before the wingtip, making the total wingspan 3 feet wider than stock Avid. The second pics show the wing tips cut off and taped with vinyl tape to "cap" them. The wingspan is now the same (+4 inches because of wider fuselage) as the standard Avid and the wings flex MUCH less. I still want to improve this with new spar stiffeners though. I will also experiment with wing tip fences since it is set up perfectly to do that now.

IMG_0303.JPG

IMG_0304.JPG

IMG_0305.JPG

IMG_0306.JPG

Share this post


Link to post
Share on other sites

Posted (edited)

A little more progress on the cosmetics of the Flat Avid. Got the stripes on Cowl and blue on bottom to sort of match up to what the original builder did on the fuselage. I think it is turning out pretty nice. Now on to the wings. Trying to see if it is feasible to replace spar stiffeners with longer ones and figuring out how to cap the wingtips as well as cosmetic fixes. The cowl does actually match the fabric much better than the lighting in the photo would lead me to believe.

IMG_0540.JPG

IMG_0539.JPG

Edited by Chris Bolkan
1 person likes this

Share this post


Link to post
Share on other sites

Posted

Looks great....if this beauty were mine I would continue the blue colour from bottom of fuse along bottom of cowl to make the cowl look slimmer and unify the fuselage...

 

My 2 cents...very subjective

Share this post


Link to post
Share on other sites

Posted

Funny you should mention that. I spent hours agonizing over how to carry the blue on the bottom of the fuse thru the cowl. I used a roll of blue masking tape to try and figure out how to do it and the cowl window just kept screwing everything up as well as how to carry the blue around the front or terminate the stripe, so this is what I settled on for now. I have plenty of blue paint and it is easy to change or add later because fortunately the plane was painted in Poly Tone which is what I also used on the cowl. It is super easy to work with as far as adding/changing stripes and so forth.

Share this post


Link to post
Share on other sites

Posted

Hey Chris.....something in those lines maybe.....

IMG_0539.thumb.JPG.cc08ba8a72161cc45e6172b19d6c93bc (2).JPG

2 people like this

Share this post


Link to post
Share on other sites

Posted

Hey I like that nice work.

I Bet that drain is full of nuts and washers. :)

Share this post


Link to post
Share on other sites

Posted

Wow! How did you do that? Very cool! You obviously have an artistic side I that I do not! Now I have lots to think about.......

Yes occasionally I remove the grates from the pit and go mining for lost artifacts :-) The pit has proven very useful many times though. It's 12 feet long and 6 feet deep. I somehow got it past the inspectors when I built my house. Pretty sure it is not fully compliant with all safety regulations!

Share this post


Link to post
Share on other sites

Posted

I know that cowl represents a lot of work but definitely time well spent. Looks great, even better with the lower color carried forward imho.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0