Leading Edge Extensions

32 posts in this topic

Posted (edited)

Anyone,

I am trying to find the post that Jim did for the leading edge extensions for the HH wings.  I think Joey said his barn Avid had these on it.  Jim had posted a drawing of these that I would like to print and he is out of pocket for a week so suggested someone on the Forum might know where to look?  Also, has anyone read any performance reports to extending the LE on the HH rib wing?  The KF extension seems to be helpful, but is very minimal.  Thinking a little bit more might be better?

 

Edited by SuberAvid

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Posted (edited)

Randy try the attachment in this thread.

Edited by C5Engineer

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Posted (edited)

SuberAvid,  I posted a couple of photos somewhere, and one drawing in files and forms of how I made wood rib extensions, using an aluminum tube for the leading edge, and covered top and bottom with 1mm plywood to extend my leading edge about 4 inches. 

I think that both the .032 tube (I forget if it is 1.25" Diameter) in the leading edge and the plywood cover would prevent dents and deformations more than the .016 sheet aluminum, although I think I added about 10 lbs to wings.     EDMO

Edited by EDMO

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Posted

Thanks Joey and Ed. That is what I was looking for.  I am thinking about doing that Lee Dubay LE mod on my new wings.  Ed, I think your 4" mod is more than I need.  I sure wish there was some performance testing information in these to see if they are worth the effort.

I think I will try to form some mini leading edge ribs out of aluminum and see how successful I am.  It should give the .016 aluminum sheet much more support than just being out there unsupported.  If someone knows the designation for the soft aluminum to use in forming ribs that would be much appreciated as well.  Also, any ingenious way to shape that LE curve?  I will probably try to do it in 4' lengths to keep it manageable.

Thanks for the help.

Randy

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Posted (edited)

Randy,  I considered doing what you are thinking about, and decided that it was too much work to try to form aluminum rib extensions, and then how do you attach them to the spars? - I wouldn't want to put more rivets in my spars.  It was much easier to just cut some 1/4" plywood and use 9460 to attach them to the spars and old ribs.  You wouldn't have to go 4" like I did - you could make them shorter, and match the profile of the old spars and ribs, and glue/rivet your aluminum sheets to the new LE tube and on ribs, top and bottom.  Any annealed aluminum would be soft, like 6061-0, but you can form them just as well out of T6.  EDMO

Edited by EDMO

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Posted (edited)

This made me think of the STOL leading edge kits I've seen people install on certified planes. Here are some examples:

https://www.backcountrypilot.org/forum/added-some-weight-to-the-plane-sportsman-stol-15225

https://www.backcountrypilot.org/forum/horton-sportsman-stol-kit-questions-18023?start=20

Notice the foam ribs they use. One benefit is that the wider foam ribs provide more surface area for the sheet metal leading edge. Just a thought.

Edited by Luked

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Posted (edited)

One other thought, if you could find a PVC or some kind of vinyl sheet, that wouldn't dent like aluminum, and you could glue it, but it may be heavier than plywood or aluminum.    EDMO

Edited by EDMO

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Posted

are you looking for this?  This is what i put on my Catalina- I think they're still available from kitfiox

 

leading_edge.thumb.jpg.4179a6faf53b5d5c6

 

Jack

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Posted

Jack,   SuberAvid has that - I think he is looking for more leading edge extension than this gives.   EDMO

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Posted

Or...this one (Jim Chuk sent this to me, a while back...)

 

leadingEdgeExtention(Large).thumb.jpg.a1

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Posted

I would use the second picture and forget the ribs in there also go back another half inch and rivit into the wood capstrib top and bottom instead of the spar that would be strong

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Posted

Randy, 

For what it' worth when I bought Pursang it had the plastic leading edge cuffs on it. John said that was the single biggest change in flying that he made to the airplane after it was finished and already flying. Since I have no idea how it flew without them I can't really tell you first hand. Just thought I'd pass that information on though. Personally I like the idea of the .016 aluminum too. That seems like it would be an easy add on. The cuffs on pursang had no glue or anything holding them on other than another layer of fabric over the old stuff. It help them on just fine. 

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Posted

I would wonder if a guy glued foam to the front of the spar, shaped it to what you want, and then fiberglassed it instead of the aluminum.  You wouldn't have to drill the spar that way, and it should be a bit stiffer than sheet aluminum.  Probably no heavier either.  Jim Chuk

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Posted

Thanks everyone; a lot of good ideas and information.  I have flown Jacks Avid+ with the KF LE and mine with nothing and Jack's plane will out climb mine.  I bought a set of the KF leading edge from Ed so have that available but the configuration of the Lee Dubay LE mod with just a bit more is very intreging.  The question is how best to do this.  You guys gave me a lot of good options.  I don't want to put any rivets into the spars so will plan t wrap it to the wood ribs.  If I was good at fiberglass that might be a good way but I have a hard time keeping it light.

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Posted (edited)

Or...this one (Jim Chuk sent this to me, a while back...)

 

leadingEdgeExtention(Large).thumb.jpg.a1

The diagram above reminded of the installation procedure for TKS panels on Caravans.  There's some good techniques mentioned in the vid below that you might be able to adopt and likely without having to drill holes into the spar and the use of rivets you mentioned.

https://www.youtube.com/watch?v=HnU5G_wSxng

 

Edited by allonsye
content

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Posted

I added the plastic KF leading edge to my KF III. Easy to install.  You could probably even add it without recovering the entire wing.  Climbed like a shot and would easily go through the red line with a 912ul.

Skip

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Posted

I think one good thing about Lee Dubay's design is the fact that it would make the wing about 1 1/2" wider, expecially where it would do the most good, on the front.  Most Avids are on the nose heavy side, and if a heavier engine is used, it would help there as well.  Remember that Kitfox has angled the wing tips forward on some models to help the CG if a heavier engine is used.  This I believe would give the same effect.   That all depends though on whether this leading edge has any bad flying characteristics.   I can't remember anyone saying the have flown with it so who knows.  Jim Chuk

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Posted (edited)

I think one good thing about Lee Dubay's design is the fact that it would make the wing about 1 1/2" wider, expecially where it would do the most good, on the front.  Most Avids are on the nose heavy side, and if a heavier engine is used, it would help there as well.  Remember that Kitfox has angled the wing tips forward on some models to help the CG if a heavier engine is used.  This I believe would give the same effect.   That all depends though on whether this leading edge has any bad flying characteristics.   I can't remember anyone saying the have flown with it so who knows.  Jim Chuk

As long as the forward radius is kept about the same as the Kitfox plastic leading edge, which is probably about equal to a 1 1/4" or a 1 1/2" circle, and the upper and lower profiles are kept the same as the original ribs, then it should fly like the Kitfox undercambered wing with the plastic leading edge, with the added benefit of moving the CG back about half of the length of the extension, and adding a little bit to the square feet of the wing surface for more lift.   EDMO

Edited by EDMO

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Posted

I wonder  how much it would help the stall speed,I think I'll have to add this to the new wing project too

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Posted (edited)

I wonder  how much it would help the stall speed,I think I'll have to add this to the new wing project too

I would have to look in my books for the formula to figure stall speed, but weight and wing area are two factors - if you reduce weight, or increase wing area, you should lower stall speed.  Just remember that in a landing stall, you still have to fight the wind.  I watched a PPC flyer start to land on a taxiway, and a gust of wind picked him up and sideways, and then turned him loose over a hanger where he put his legs thru a skylight...

"Too slow and the earth will come up and smite thee"!   EDMO

Edited by EDMO

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Posted

I was just looking at the kitfox site in there catalogue for the plastic leading edge,the only thing I found was the" laker leading edge ".It says it will not apply to the model 1 through 3 hi undercamber wing. Im not sure if that is the leading edge that some of you have used from kitfox ??? Kind of pricy too at $995 for the kit. Has anyone used anything else beside the aluminum leading edge

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Posted (edited)

I was just looking at the kitfox site in there catalogue for the plastic leading edge,the only thing I found was the" laker leading edge ".It says it will not apply to the model 1 through 3 hi undercamber wing. Im not sure if that is the leading edge that some of you have used from kitfox ??? Kind of pricy too at $995 for the kit. Has anyone used anything else beside the aluminum leading edge

I've never heard of the "Laker leading edge" - the Kitfox plastic leading edge I had on mine would fit any model, but it was designed for the model 4 and up - and it probably was more like $150 or $200 - I forgot how much it cost - sold my used one to SuberAvid when I added the 4" leading edge extension to my wings.   I think I posted a copy of the template with drawing of the leading edge - maybe in files an forms or somewhere?   EDMO

Edited by EDMO

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Posted

I am pretty sure the laker kit was a fiberglass leading edge extension that was pretty close to the pics that Jim posted up.  Maybe a bit more of an extension.  It will work on the earlier undercambered ribs but does not help as much as it does on the later airfoils from what I read.  I have the aluminum extensions that Jim posted but I am not sure how much they helped.  I think it would be a lot bigger help if there was not as much washout than mine has.

:BC:

 

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Posted

Ya I seen the drawing Ed, I dont think that laker leading edge is the same stuff but that was all I could fine on there site.

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Posted

What about just sawing a thinwall pvc pipe of the correct size about in half, or whatever fits good, and glue it on with 9460 or Leni's Loctite 5200 or something - that should give you about an inch of extension and protect your spars from bumps - I think the protection of the spars is the most important thing that the plastic LE does anyway.   EDMO

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