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Mk IV with wing extensions - specs\p0

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Posted

Does anyone have the specs (esp. cruise speed) for an Avid Mk IV with the 3' wing extensions (that means 35' span).

Engine is a 582.

And one other thing - how's the standard (not 'wide') gear on that plane for a taildragger newbie?

Thanks!

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Posted

Does anyone have the specs (esp. cruise speed) for an Avid Mk IV with the 3' wing extensions (that means 35' span).

Engine is a 582.

And one other thing - how's the standard (not 'wide') gear on that plane for a taildragger newbie?

Thanks!

I will have to check my design books, but believe the standard ratio for wingspan / landing gear is 4:1, so your landing gear with 35 foot wings would have to be about 9 feet wide.

ED in MO

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Posted

Does anyone have the specs (esp. cruise speed) for an Avid Mk IV with the 3' wing extensions (that means 35' span).

Engine is a 582.

And one other thing - how's the standard (not 'wide') gear on that plane for a taildragger newbie?

Thanks!

Was it a standard speed wing MK IV that they put extensions on or was it a full length wing that was extended? I have flow an extended speed wing and it was a pleasure to fly! very light and sporty on the controls, yet I could get it in and out of every place I bring my "C" Heavy Hauler. If they were full length wings that were extended, I would LOVE to know what they did. Were the struts extended also? I would love to put extensions on mine, but I am afraid the washout in the wings would kill any performance increase I would have seen for STOL.

BC.gif

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Posted

[Was it a standard speed wing MK IV that they put extensions on or was it a full length wing that was extended? I have flow an extended speed wing and it was a pleasure to fly!]

 

Hi everyone just a quetion about this. what is the extended length that everyone is talking about? sorry for the dumb question I am just trying to figure what wing to build for an avid mark 4 with a rotax 582

Bob in Florida

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Posted

Standard span was only 29ft and with the flat bottom speed wing the takeoff and landing peformance was nominal. Takeoff distance was much longer than a STOL wing and the increase in cruise wasn't very signifcant. Most people that had them either swapped them for STOL wings later or added an extension kit to the Speedwing that Avid produced because they recognized that a standard length speedwing was not meeting customer expectations on performance. No matter what wing you have with the 582 80-90mph is probably a realistic cruise speed. I've seen guys pushing 105 mph that are real careful about fairings and have a Jab or 912 for power.

 

Here is the Speedwing extension kit that Airdale was selling http://www.airdale.com/speedwingext.htm

 

What wing to build depends on your mission. If you plan on flying light and off of pavement most of the time you would probably be fine with a Speedwing. If you are wanting to blast out of a 500ft grass strip fully loaded with camping gear STOL all the way!

 

A lot of people have groundlooped and tore up these airplanes on standard bungee gear. They require some respect for sure but there are also gobs of them out flying just fine with it including myself as well. The wider gear does make them handle a lot better on the ground.

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Posted (edited)

Bob, I forgot to put this in the answer to your PM: From what I hear, the Speedwing ribs are not the same as the later Kitfox ribs. Harry Riblett designed the Kitfox ribs for faster cruise with the long wing. The Kitfox wingspan was about 32 feet compared to the 29 foot Avid wingspan.

As soon as I get some colored markers, I will post a photo in "files" showing the difference in the early and late Kitfox ribs, and some mods I have made or plan to make - just so everyone knows.

EDMO

Edited by Ed In Missouri

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Posted

are you looking to buy a specific plane or to build these wings? my kit came with the speed wing but i built it on HH spars to HH specs just used the speed wing rib profile except for the first 3' which was higher to accommodate the HH wing tanks.

I have flow an extended speed wing and it was a pleasure to fly! very light and sporty on the controls, yet I could get it in and out of every place I bring my "C" Heavy Hauler.

 

 

Leni do you remember if this extended speed wing had the original short flapperons or where they extended? still trying to decide if i'm going to extend them or not.
:BC:

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Posted

are you looking to buy a specific plane or to build these wings? my kit came with the speed wing but i built it on HH spars to HH specs just used the speed wing rib profile except for the first 3' which was higher to accommodate the HH wing tanks.

I think I remember Leni Akflyer, saying that the Kitfoxes could get off a few feet shorter than his Avid??

EDMO

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Posted

Does anyone have the specs (esp. cruise speed) for an Avid Mk IV with the 3' wing extensions (that means 35' span).

Engine is a 582.

And one other thing - how's the standard (not 'wide') gear on that plane for a taildragger newbie?

Thanks!

I would recommend the wide gear; there are several to choose from including the wide Airdale bungee gear or bush gear, or Grove spring gear.  The wide stance make the plane a lot easier to control on the ground and you can recover from some not so great landings to take another turn around the patch instead of repairing your plane.

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Posted (edited)

Bob, I forgot to put this in the answer to your PM: From what I hear, the Speedwing ribs are not the same as the later Kitfox ribs. Harry Riblett designed the Kitfox ribs for faster cruise with the long wing. The Kitfox wingspan was about 32 feet compared to the 29 foot Avid wingspan.

As soon as I get some colored markers, I will post a photo in "files" showing the difference in the early and late Kitfox ribs, and some mods I have made or plan to make - just so everyone knows.

EDMO

 

Ed is correct. I have posted photos in numerous threads comparing the various early/later kitfox ribs vs. Avid HH/STOL and Speed/Aerobat ribs. Someday I'll just make a post and put them all together for easy reference. To save search time, here are some photos showing the diff between Riblett designed Kitfox models 4-7 laminar flow rib (truss style web cutouts) and Dean Wilson designed Avid Speed/Aerobat rib (oval style web cutout). Also interesting to note that KF 1-3 and Avid HH/STOL under cambered rib airfoils are not the exact same profile as most folks seem to believe.

 

[edit] I would add that, while not shown in the pics below, the extruded leading edge cuff is an integral part of the Riblett laminar airfoil.

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Edited by dholly

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Posted

I see the difference in the ribs I will bet that if you change to some of the rib designs that I see that you would also have to deal with the angle of attack on the wing also [just by looking at the location of the rear spar cutouts] correct?

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Posted (edited)

I see the difference in the ribs I will bet that if you change to some of the rib designs that I see that you would also have to deal with the angle of attack on the wing also [just by looking at the location of the rear spar cutouts] correct?

Probably a little more than that - Yes, the angle of attack,(engineers call this "incidence"), will set the angle of the fuselage in flight, setting the angle of the horizontal stabilizer, prop angle, etc.

For instance, My Subaru engine is heavy, and I wanted less downslope on the rear of the bottom of the rib, which pushes the nose of the plane down, requiring the up elevator or up flaperon, or even weights in the tail, to trim it, like a lot of the planes flying with this and other engines and the undercambered ribs.

So by using the profile of the Kitfox 4 rib on the bottom, I hope to eliminate some of the downward nose forces, and trim out better for all conditions. (I hope)

Note that I did not change the angle at which the rib sets on the spars, like the later Kitfoxes.

EDMO

Edited by Ed In Missouri

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Posted

-snip- So by using the profile of the Kitfox 4 rib on the bottom, I hope to eliminate some of the downward nose forces, and trim out better for all conditions. (I hope)Note that I did not change the angle at which the rib sets on the spars, like the later Kitfoxes.EDMO

I was unaware Kitfox made changes either to the airfoil or angle of incidence relative to the wing spars on the KF4-7 wing??

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Posted

I don't believe they did from the IV through the SS.  

 

The I, II and III had incidence changes between them culminating in the extreme high tail flying III.  I believe this was an attempt at alleviating the yaw proclivities from the overly small P51 shaped tail that Denny was so attached to.

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Posted (edited)

I don't believe they did from the IV through the SS.  

 

The I, II and III had incidence changes between them culminating in the extreme high tail flying III.  I believe this was an attempt at alleviating the yaw proclivities from the overly small P51 shaped tail that Denny was so attached to.

 

Again, I don't believe there were any changes at all to either the 4-7 rib profile or angle of incidence relative to the wing spars. I also do not believe there were any changes at all to either the KF 1-3 rib profile or angle of incidence relative to the wing spars. To the best of my knowledge, the location of the rear spar cutout in the rib web never changed in 1-3 models or 4-7 models and are completely interchangeable respectively. The only changes that I am aware of that would result in an overall aircraft angle of incidence was the addition of front adjustment holes for the KF 3 elevator and the different elevator adjustment methods used in the KF 4-7 models. Please enlighten me if I have that wrong!

 

[edit] add pic of my KF3 showing elevator adj holes, I used middle position IIRC

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Edited by dholly

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Posted

Doug, the wings were built originally with 1 3/4" or even 2" of washout in them.  I think they are now built with 1/2" total washout.  I am thinking this is what other are talking about as AOA.  I could be wrong, it wouldn't be the first time :lol:

 

FWIW, I am going to rebuild my wings at some point using the KF IF profile and 1/2" washout.

 

:BC:

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Posted (edited)

I think the illusion that the ribs set on the rear spar differently between the KF1-3, and the KF4-7, may just be an illusion - the distance from the bottom of ribs to rear spar are different because of the profile of the 4-7 in that area is thicker. The distance from spar to top may be about the same?

The incidence was changed from the KF-1 when the KF-2 was built, according to Ed Downs - This was done by changing the height of the rear crossover tube. I don't know about any later changes in incidence, but there could have been some.

I don't think the washout has much to do with this, but I sure wish I had 1/2 inch instead of the original amount. Too late to worry about that for mine.

EDMO

Edited by Ed In Missouri

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Posted

Doug, Seehafer told me of the incidence changes between the early Kitfoxes. I consider him a fairly accurate, if not long winded, source.

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Posted

Doug, Seehafer told me of the incidence changes between the early Kitfoxes. I consider him a fairly accurate, if not long winded, source.

Can you put his "long winded" explanations into something "short winded", for us?

EDMO

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Posted

I'm sure Doug is laughing at that request, Ed.  You would have to meet and speak with Paul S to know there is no possible short explanation to anything!   :lmao:

 

My earlier post is a good short synopsis of his observations to me.  The KF-I was a good little [copy of an Avid].  One of the things of the Kitfox design is the P51 looking tail, that Dan Denney had a hard-on for.  To make it look right, it was in fact too small.  To compensate for this the II re-incidenced the wing and tail to lift the tail into the slipstream more to gain effectiveness.  The III did this further, making it fly tail high.  Ironically this process did little or nothing to help the Yaw issues.  Denney is not an engineer or airplane designer. He's a salesman.  (And it showed)

 

With the IV, Denney actually hired an aeronautical engineer.  This is why the control system changed along with the airfoil and finally the tail...

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Posted

Great explanation, thanks Larry.

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