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speed wings/stol wings.


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Posted

I have an Avid speedwing with a 582 on it, and I do not like the way it handles/ It "pops" off the ground and although it doesn't fly bad, it stalls suddenly and without much warning.

I have a second set of speedwings that need some work. Do I want to: (1.) extend the Speedwing to full length or: ( 2)  Extend the spars and replace the speedwing ribs with STOL wing ribs. I have to make ribs anyhow, and it is just as easy to make a dozen as it is to make six.)

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Posted (edited)

Why not extend the second set to full length, or Kitfox length which is a little longer, and use Kitfox 4 Riblett type ribs, with hanger-tails like Avid, which are supposed to be better than the STOL or Speedwing ribs?  It would also be a good time to reduce the washout to about 1/2", and add the leading edge protection with the Kitfox plastic bumper.  You should get better cruise and slower stalls.   EDMO

Edited by EDMO

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Posted

The very first Avid I ever flew in had full length wings with speed wing ribs.  The owner said it flew a good deal faster than the STOL wing Avids he flew with, and was almost as good getting off the ground.  He flew it quite often with other Avids, so had a good way to compare with planes with same engine and such.  After flying my Kitfox 1, I wonder if I wouldn't extend the wings another foot on each end to have same length as the Kitfox, but with the speedwing ribs.  Wouldn't be surprised if it beat a STOL standard wing both ways.  Don't have any real proof, just my gut feeling.  JImChuk

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Posted (edited)

The very first Avid I ever flew in had full length wings with speed wing ribs.  The owner said it flew a good deal faster than the STOL wing Avids he flew with, and was almost as good getting off the ground.  He flew it quite often with other Avids, so had a good way to compare with planes with same engine and such.  After flying my Kitfox 1, I wonder if I wouldn't extend the wings another foot on each end to have same length as the Kitfox, but with the speedwing ribs.  Wouldn't be surprised if it beat a STOL standard wing both ways.  Don't have any real proof, just my gut feeling.  JImChuk

Jim, Your experience says a lot - Just remember that on your Kitfox the squared droop tips add to wing area and span.  Kitfox Hoerner tips should be even more efficient than the round Avid tips too.   I would still put the Kitfox plastic leading edge bumper on Speedwings, and change the washout to 1/2".  Any design can be improved on, and that is the greatest thing about Experimental Aircraft, you can strive to build better.   EDMO

Edited by EDMO

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Posted

I ran across a study done on wingtip advantages on line a few years ago, and it showed that drooped tips gave a slight improvement over other types of wing tips, but it was a very small amount.  I have not been able to find that study again when I looked for it, but I know what I  read.  On the same topic, I once talked with Wayne Ison who designed the Team Mini-Max and High-Max as well as other planes, and he told me that the drooped tips didn't do much better than the squared off wings.  Mostly just looks.  Interestingly, now Kitfox has gone away from the drooped tips as well.  I do know they can put a good sized dent in your head, and act as a skid in a ground loop.  (I don't know that last part from experience however) :-)   JImChuk

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Posted (edited)

I ran across a study done on wingtip advantages on line a few years ago, and it showed that drooped tips gave a slight improvement over other types of wing tips, but it was a very small amount.  I have not been able to find that study again when I looked for it, but I know what I  read.  On the same topic, I once talked with Wayne Ison who designed the Team Mini-Max and High-Max as well as other planes, and he told me that the drooped tips didn't do much better than the squared off wings.  Mostly just looks.  Interestingly, now Kitfox has gone away from the drooped tips as well.  I do know they can put a good sized dent in your head, and act as a skid in a ground loop.  (I don't know that last part from experience however) :-)   JImChuk

I read and posted some info from a study that the Short Wing Piper group published that showed squared tips being more efficient than round tips.  I agree with Jim on the Drooped tips sometimes being a pain in the head, but if they act like a skid in a groundloop that might not be a bad thing.  If I was buying new tips I would get the Kitfox Hoerner type, as they are supposed to have less drag.   TJay put them on his undercambered wings, so they should also fit the Speedwings.   EDMO

Edited by EDMO

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Posted

Couple of questions: Where could I get a drawing or pattern of the Riblett Airfoil?

Second: My brother has a Kitfox Classic Four with a flat bottomed airfoil. It is six inches longer in the fuselage, and about 26 inches longer in span than my avids are. It also has a significantly larger fin and rudder.  I also had at one time a KF IV fuselage that I was going to put Avid wings on, but gave up on that project. I have done extensive measurements on the geometry of the carry- throughs on the Avids and the KF IV and; on the Avids the front spar carry through is 1 1/8 inch lower than the rear spar carry through, but on the KF IV  they are in line. This would have the effect of raising the leading edge on the Fox. by 1 1/8 inch. How would that play into the Riblett airfoil? Also how can I reduce the wash-out without de-glassing the tanks" Other pilots have told me that the Speedwing appears to be flying nose- high when it is in level flight. This would make a certain amount of sense if the necessary Angle of Attack of the flat bottomed speedwing is higher than the AOA of the STOL wing. It also makes sense if the KF uses a flat bottomed airfoil on the Classic IV.

My brothers Fox has a flatter bottomed airfoil, and the ailerons are much closer to the wing than are the Avids.

I am flying an Avid Speedwing, and an Avid Heavy Hauler wing with a KF front end on it, and I don't like either one. The performance of neither is very good, and the forward visibility out of the KF on the ground sucks. I am building a third one out of parts I collected, but it doesn't appear that the finished product is going to be any different than what I already have, and so I am not very enthusiastic about it.

 

Bob

 

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Posted (edited)

I posted a drawing "KITFOX RIBS" comparing Kitfox 2 undercambered and Kitfox 4 Riblett ribs in FILES AND FORMS in 2 Aug 2013 (about page 3 of that section index)  Included was some lines showing the modification I made to my undercamber ribs to make them like a modified Riblett only with hanger tails.  Not included there is the fact that I had to replace my rear jury strut attachments with longer ones.   I also posted some pictures of my modified ribs in Kitfox IV section, I think.  You might be able to get a drawing of a root rib from someone who has a Kitfox 4 or later model. 

 Kitfox may have made some "Speedster" ribs for the KF4 that were flatter on the bottom, but this may have been a Kitfox 5 option.   I think Speedster wings were shorter than standard Kitfox wings.  That info might be in the "Kitfox Pilot's Guide" book written by Ed Downs and is still sold by Kitfox. 

The height of the rear wing attach crosstube has been changed as the Kitfox models progressed.  Some flew tail low.  One of our members measured some of them and posted drawings and measurements on this site.  I don't know how much difference it makes since I haven't flown all models.   EDMO

Edited by EDMO

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Posted

I have some Kitfox 4 ribs lying around.  I could perhaps trace one out for you. PM me your address.  As far as the Kitfox front carry through goes compared to the Avid, as long as the horizontal stabilizer was in line with wing I'm not sure what difference it would make.  Wouldn't it just help to see over that high cowl on the Kitfox while in flight?  I don't think the wing cares where the fuselage is other than drag as long as the stabilizer is lined up correctly with the wing.  JImChuk

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Posted (edited)

 

Couple of questions: Where could I get a drawing or pattern of the Riblett Airfoil?

This is still the standard rib airfoil offered from Kitfox.  They will not willingly publish it so that people can make their own.  You will need to find a rib to reproduce it.

 

I also had at one time a KF IV fuselage that I was going to put Avid wings on, but gave up on that project.

This is opposite from what most folks do to create a hybrid.  The Model IV Kitfox wing and control system is far superior to anything that Avid ever offered it is usually put on to the Avid fuselages.  This is what my friend Dave did with his stretched "C" model Avid fuselage.

 

Kitfox may have made some "Speedster" ribs for the KF4 that were flatter on the bottom, but this may have been a Kitfox 5 option.   I think Speedster wings were shorter than standard Kitfox wings.  That info might be in the "Kitfox Pilot's Guide" book written by Ed Downs and is still sold by Kitfox. 

The Model IV Kitfox "Speedster" has the exact same Riblett rib profile as the long wing.  The only difference is the wing is shorter in span by one rib bay. 

Edited by Av8r3400

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Posted

Just out of curiosity what about it do you not like? Are you flying it close to stall a lot? These guys have MUCH more experience than I and they have helped me out on my journey with my own flyer. One option may or may not fit your bill and would be a lot easier. Vortex generators. I didn't like the wing walking my flyer did when I came in to land. If I didn't come in pretty hot 60 or higher the wings would take turns dropping as I came in to land. It just didn't feel very secure especially the closer and slower I got to the ground. I put VGs on the wing and under the H stabilizer from Land shorter.com (only plugging them because they were the cheapest I found at the time to experiment with) While they didn't turn my flyer into a short field f-16, it did drop my stall about 3mph but it REALLY solidified the wing in the air coming to land. It is SO much more comfortable to land now. I wouldn't go back now. Take it for what it is worth. I am a low time pilot about 200hrs so this may not be of benefit to you, but I am very glad I put the VGs on for no other reason other than what it did to my landing ability. I fly out of a 1000' grass strip with power lines on the north end. I have to slip hard to get down and stopped and vgs gave me more confidence in doing that.

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Posted

The speedwing does not want to get off the ground. I believe it would run the length of our 5000 foot paved runway with the tail in the air and never lift off. With the flaps at 10 degrees and the tailwheel hard on the ground it will "pop" off the ground and then climbs like a rocket. On approach at less than about 60 per it will come down at about 750 fpm. It stalls suddenly and without warning except that it begins a flat  turn to the right. In its defense, it doesn't bounce. When it's on the ground it stays there.

I am skeptical that it would lift two people.

I talked to Snaps down in North Carolina and he basically said "that's the way they are".

Before you ask, it has been measured, weighed rigged, re- rigged, and compared dimensionally with other Avids at least fifty times. I have not tried VG's yet.

I had a STOL wing that was a pleasure to fly. It wanted to float.

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Posted

Interesting thread. Now with all due respect to Snaps, to say all Avid Flyers with speedwings will not lift off from a 5000' runway in clean configuration seems a bit extreme. There are just way too many flying today that have proved otherwise, even it they aren't near the performance equivalent of of a STOL wing Avid. Makes me think something specific to the aircraft/engine/prop is still wrong, particularly when you also say it climbs quite well once airborn. Sounds like adding the VGs might be a pretty cheap experiment with positive landing benefits, even if it doesn't completely 'fix' the underlying takeoff issue. Keep us posted.

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Posted (edited)

From what Av8r3400 has said, his Kitfox 4 with Riblett wings floats a lot more than the undercambered wings on landings, and gets off the ground as quickly - but you better ask him about that - I am just repeating what I think he said before he added more horses under the cowl.  EDMO

Edited by EDMO

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Posted

Yes, Ed. With the Riblett wing if you are fast, it will float and float. If you are on target with your speed and energy it will stay right where you put it. 

I'm getting better with mine. I can be down and stopped in less than 300' and off in less than 250' (thanks to the hp and Prince prop). 

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Posted

Ed, my KF3 w/ 582 blue head got off the ground q-u-I-c-k and I was very surprised at just how fast things happened the first time! My KF4-1200 w/ 912ul off not quite as fast, it was heavier of course, but it pulled a lot stronger and you didn't have to drop the nose near as soon on max performance TO's. Unless it was an early Avid model and very lightweight, I would expect a short speedwings to be a slug in comparison. BUT, they do fly...

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Posted

I agree with Larry, my KF4 was a real floater when landing fast! I actually did mostly wheel landings to get it down where I wanted, rollout not really an issue where I flew. But it also and a pretty damn fast sink rate if you let it get too slow on final, original builder/test pilot even noted it in the Logbook after the 1st flight.

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Posted

My mkIV has the speed wing and I have video solo take off and with passengers. The plane takes a couple hundred feet and I'm off the ground. What is the prop pitch at size etc ? I have a warp drive 3 blade taper tip and it climbs fast and cruises unbelievably.

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Posted

Use all the flap you have to pop it off the ground.  I have flown the extended speed wing and my HH wing same day same conditions and I could get the extended speed wing in and out just as short but it cruised a good bit faster and felt a little "sportier" in the air.  In short, I loved the way it flew.  If ya'll are not using the flaperons (setting such ad 10 deg mean nothing its not a cessna) to the full travel your leaving performance on the table.

I start off the ground roll with full down elevator and no flaps.  As the tail starts coming up start relaxing on the stick.  At 35MPH I yank in full flaps and pull back on the stick to pop it off the ground.  While staying in ground effect drop the nose a little and start bleeding off the flaps gaining speed till 55 then start pointing the nose to the sky.

Granted, I am at sea level and moderate temps.  Hotter days I may build speed to 40 before I yank flaps.

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Posted

My way of getting off quick is similar but I use about 1/3 flap to help get the tail up as I have a short prop and acceleration is poor until the tail is well up.Getting rid of flap while still in ground effect is a wise move(an engine failure with full flap isn't fun)

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