Avid Airdale with Harley engine on barnstormers

[TJay 1041]

I to am excited for a flight report.

[Allen Sutphin 705]

If you haven't flown it yet and don't know how it flys, anything would be a guess at this point. Might ask the person who built it, they could give some insight.

[ne14Yah 0]

He dead

[TJay 1041]

 I will say I'm sure Tommy would never let it go out the door if its not in safe flying condition.  Just point it toward the moon.

[ne14Yah 0]

My airfoil is definitely not your average run of the mill KF1,2,3,4 or Avid airfoil.  From what I have gathered, the Riblett 30-612 airfoil was used on the KF 5, 6 and 7 series?  I don't believe my airfoil is exactly like the 30-612, but I haven't seen a drawing yet that would show a comparison.  How would a similar airfoil mix into the geometry questions I have posed?  Would a similar airfoil explain why the lines are not traditional?  Is there another forum or thread that anyone could recommend?  I will post a picture of the airfoild I have tomorrow, if that would help.  Thanks!

Edited 11 Mar 2019 by ne14Yah
correction

[ne14Yah 0]

I apologize for the reposting of the pics.  Not sure why, but they seemed to be added when I made corrections.  If I try to delete them, they disappear at their original posting.

[1avidflyer 1983]

In a way, it's hard to tell what is what with some of these planes.  Different people get different ideas when they build something (for better or for worse)  Question it seems to be, is the cowl built out of whack or do they have the engine tilted up real high.  Can you get a straight edge going forward off the front and back wing carry throughs, and see if the prop is at a 90 degree to that straight edge?  That would be something someone else could check on their plane, especially if it had a factory made motor mount.  That would then maybe help to see if the cowl is cocked or the prop flange.  Kitfox 4-7 all use the same rib shape I believe.  Earlier Kitfoxes ribs are similar to Avid's STOL or Heavy Hauler ribs but not exactly the same.  Avid also had a speed wing rib which is a flat bottom rib.  Yours does kind of look like a speed wing rib profile although it's hard to say for sure from the picture.  Can you snap a picture of a long rib tail and post it?  JImChuk

[TJay 1041]

I think the Airdale is more Symmetrical type airfoil but I cant remember. Also take a picture of the butt rib I think that is the Avid airfoil and the wing drops down from that. 

[Av8r3400 1178]

If it has extended rib tails to hang the flapperons from, it is not a Kitfox-Riblett wing.  These have separate aluminum brackets that the flapperons are attached to.

 

[ne14Yah 0]

Well, I made a mistake.  The original builder is not dead.  I spoke with him this morning, but he couldn't elaborate about the lines, only stating that the guy he bought the HD from (Brett - Hog Air, now out of business) fabricated and installed the engine on his air frame.  He couldn't remember who established the horizontal stabilizer, but a closer look at the pics indicate that it was installed the way I have it at the time the builder had it.  The builder also provided the email address he had for the original designer, John Larson, so shot off an email to him.  Hopefully it's still good!

A picture I overlooked shows the words "Speed Wing" hand written on the wing roots, so looks like that mystery may be solved.  My wings do not have a flat bottom.

[sioux201 84]

 Just got off the phone with Jerry Matison, he's familiar with this plane, it's called a fat avid, The grove gear is the giveaway

 He just talk to John Larson last week and told me that the email is the same, if you need additional information let me know

 

 

[1avidflyer 1983]

In a way, it's hard to tell what is what with some of these planes.  Different people get different ideas when they build something (for better or for worse)  Question it seems to be, is the cowl built out of whack or do they have the engine tilted up real high.  Can you get a straight edge going forward off the front and back wing carry throughs, and see if the prop is at a 90 degree to that straight edge?  That would be something someone else could check on their plane, especially if it had a factory made motor mount.  That would then maybe help to see if the cowl is cocked or the prop flange.  Kitfox 4-7 all use the same rib shape I believe.  Earlier Kitfoxes ribs are similar to Avid's STOL or Heavy Hauler ribs but not exactly the same.  Avid also had a speed wing rib which is a flat bottom rib.  Yours does kind of look like a speed wing rib profile although it's hard to say for sure from the picture.  Can you snap a picture of a long rib tail and post it?  JImChuk

Well I got out to the hangar today, and actually spent most of the day there.   Packed the strip again, made another drag that would smooth things and even taxied the Avid on skis.  Was to tired and sore to take it up though.  Just kind of ran out of gas.  But none of that pertains to the subject at hand, so I'll show what else I did while it was all handy.  I jammed a board up against the bottoms of the wing spars and clamped a 1x2 onto that 2x4 at a 90 degree angel, and it looks like the 1x2 was parallel to the prop.   Long story short, no up or down tilt on an Avid MK IV with an Avid  factory made Jabiru motor mount.  This is what I suggested you do with your Harley engine setup to see if there is a tilt to the engine or the face of the cowl.  JImChuk

 

[ne14Yah 0]

Hey, thanks for doing that, 1avidflyer!  Actually, I did that with a digital angle finder yesterday and found that, yes, the prop disc was almost perpendicular to the line passing through the leading and trailing spars and the horizontal stabilizer.  All within .3 degrees of each other.  I trailered it out to KBUM today and hopped down the runway 3 times with an A&P friend of mine.  It is severely under-propped with it's 2 blade Warp Drive @ 10 degrees.  We are going to try a Catto prop a buddy of his has next time he is able to get my way.  Also, need to figure out why it's bogging down when power is reduced at slow rate.  Seems alright if you pull power faster.  Might be too rich in the midrange?  I will get some pics of the wing end rib tomorrow and post.

[ChrisBolkan 130]

Jerry Matison is a super nice guy and very knowledgeable, but what you have there looks like an airdale flyer which is not a fat avid. I have a fat avid and there are differences from your plane that go beyond the cowl mods to run the Harley engine. You have a lowered floorboard for more foot room, different wing profile and wider open baggage area. Those are some of the differences I am aware of. The "fat" avid is pretty much just a stretched and widened MKIV with the control mixer placed under the seat. It fits all Avid parts like wing struts, wings elevator etc. I think that a much as the airdale flyer looks like the fat Avid, it was an attempt to create a new better plane that corrected the shortcomings of just making the original avid longer and wider. It might even be that those are not Avid Struts and that you have more headroom.. headroom did not change with Fat Avid. Your cockpit looks taller to me too. 

[1avidflyer 1983]

The way the landing gear attaches reminds me of John Larson's Pursang that Lostman bought and eventually crashed.  Take a look at it in this thread.  Which came first, the Pusang or the Airdale flyer, or were they separate designs?  JImChuk

www.avidfoxflyers.com/index.php?/topic/2794-avid-mk-v-for-sale-john-larsens-pursang/#comment-20008
 

[MnAvidFlyer 34]

Could it be an Airdale Backcountry? 

https://en.m.wikipedia.org/wiki/Airdale_Backcountry

Brooks

[ne14Yah 0]

John Larson chimed in this morning with an email response.  He advised the the engine thrust line should be 1.5 degrees down from the center line of the airframe.  All other lines should be parallel.  So, may need to modify the engine mount.  According to what he said, mine would not be a "Back Country" with my airfoil, so looks like it would be the "Cross Country".  Now I just need to figure out where is the airframe center line!  Anyone have an idea where it would be?

Edited 13 Mar 2019 by ne14Yah
addition

[ne14Yah 0]

Well, did it again.  I edited my last post and those 2 pics automatically loaded themselves.  How can I remove those pics from the above post and not end up removing them from the original post where I uploaded them?

[TJay 1041]

Thrust line and chord line should be close in my opinion.

[Allen Sutphin 705]

A short flight, even down the runway, should show if something is not aligned correctly. And what direction you need to go.  I guess I am confused as to why the issue if you haven't flown it and, since it has flown, and if there is an issue with it. But hey, its not my plane.

[1avidflyer 1983]

My thoughts are I would see how it flys before I change anything.  My Avid flys fine with the prop at 90 degrees to the spars.  You have the same measurement, so it should fly ok at that rate I'm guessing.  Make sure the CG is correct though.

I wrote this last nite, but didn't post it then.  I agree with Allen,try it out.  First though I would check some things.  As I mentioned, make sure the CG is correct.  You also mentioned earlier that the prop was under pitched.  I would imaging you know what maximum rpm is for the engine.  Just comparing a 582 and a Jabiru, static rpm was about 90 percent or a little bit less of maximum rpm on them.  I would set the prop up so your static rpm is about 85-90% of maximum rpm.  If possible, I would do a static thrust check with a scale to get an idea of how much pull you are getting from the engine.  I've read 305-310 lbs pull with a 582, so that much for sure should fly your plane.  I would fly it then and if all is well, remodel the cowl if I didn't like the look of it being crooked.  I'm just stating my opinions of what I would do if it was mine.  YMMV.  JImChuk

[ne14Yah 0]

Would love to have Jerry Mattison's contact info.  John provided me with his write-up of the history of the Avid and it's lineage.  Was quite an education!  Sadly, I have not been able to obtain the answers to my questions regarding it's design geometry and specs.  I only have a partial construction drawings and manual and need to find a complete set - hoping I can find the answers within.

So, my mechanic friend did crow hop the Airdale down our runway 3 times and reported that there were no surprises and everything felt as he would expect.  There was an issue with the engine bogging when backing off the RPM's slowly, but not rapidly.  Need to iron that out.  As I mentioned, it is way under- propped, not developing airspeed quick enough.

[Allen Sutphin 705]

Correct the engine issues and CG check and go fly the dang thing!  If there were no issues or surprises with the crow hops, there is no reason to re-engineer it.

[1avidflyer 1983]

 

So, my mechanic friend did crow hop the Airdale down our runway 3 times and reported that there were no surprises and everything felt as he would expect.  There was an issue with the engine bogging when backing off the RPM's slowly, but not rapidly.  Need to iron that out.  As I mentioned, it is way under- propped, not developing airspeed quick enough.

I wonder if I'm understanding your wrong or you're expressing things incorrectly.   You say it's underpropped, that would say by my understanding not enough prop for the engine (not enough pitch or length or both, allowing it to over rev)   But you follow that up with not developing airspeed quick enough.  Seems like a contradiction here unless you are having to back off the power to keep it from over revving.   I would adjust the prop for the correct static rpm first of all.  JImChuk

[ne14Yah 0]

My mechanic said, "It is underpropped" after he flew it - length is the problem here.  No reported problem with over revving. The CG is good.