LLE Kit (Laker Leading Edge) Composite Leading Edge ??

[rosslr]

Agreed Jim - and if I was really trying to save some dollars I would not sweat leaving it out of the mix in preference to going flying!

I liked your description of the leave fall stall Jim. I too did it during the testing phase - and a few times since. It really builds confidence in the plane. I think I ay have had the pleasure of experiencing Floog's unique "altitude adjustment" technique! Not exactly textbook but it does keep the aircraft pointed towards the target!

Hope all is good up there with you guys - I still have fond memories of your generosity and look forward o repaying it some day!

cheers

r

[HighWing]

I put an aluminum leading edge on my 2014 completed Model IV, about the time the LLE began development. A comment on the oil canning. Back in the day we flew very often along side a Rans S7 - an earlier model - and oil canning was a frequent event when it was on the ground. The guy, Hal, a name familiar to many, would just grin and walk up and shake the wing and presto "pop" and all was well.

With that in mind, though, when I was installing mine, I decided.to support the wing during leading edge installation as if it was supported by the fuselage and lift struts. In other words, supported by a saw horse like stand at rib #1 and a similar stand at the lift strut attach bracket. I am not sure if this had any effect, but I have never seen any oil canning while on the ground. I guess I need to do some in flight video testing - though it flies without any apparent downsides.

[southwind32]

I put an aluminum leading edge on my 2014 completed Model IV, about the time the LLE began development. A comment on the oil canning. Back in the day we flew very often along side a Rans S7 - an earlier model - and oil canning was a frequent event when it was on the ground. The guy, Hal, a name familiar to many, would just grin and walk up and shake the wing and presto "pop" and all was well.

With that in mind, though, when I was installing mine, I decided.to support the wing during leading edge installation as if it was supported by the fuselage and lift struts. In other words, supported by a saw horse like stand at rib #1 and a similar stand at the lift strut attach bracket. I am not sure if this had any effect, but I have never seen any oil canning while on the ground. I guess I need to do some in flight video testing - though it flies without any apparent downsides.

What thickness aluminum did you use? What technique did you use to shape it? Thanks

[David47]

Just some thoughts on the Aluminium vs fibreglass LLE. The reason you get oil canning with the Aluminium leading edge is that it is quite stiff compared to the rest of the wing structure so it's picking up more load. Oil canning, or more correctly buckling, is a symptom of that. The fibre glass LLE is relatively flexible so you won't see the same effect. So to answer your question Highwing, about whether by supporting the wing at the root and strut attach points in the build you've overcome the oil canning issue, I doubt it. It all depends on the thickness of the Aluminium LE you put on. If it's thick, it may be that the loading it picks up isn't sufficient to cause buckling. If it's thin, it may buckle in flight without you noticing, but not sufficient to stay buckled when you get back to ground.

Having said all this though, there are advantages to an Aluminium LE. One is durability from smashing bugs and anything else coming your way, perhaps with the exception of a tree as in Jim's case, the other is it provides a nice smooth aerodynamic surface at the LE which, incidentally, carries the majority of the aerodynamic pressure loading on the wing - around 50% or so over the first 30% or thereabouts, of the wing chord. So all in all, some form of LE skin that maintains profile is a good thing. But that's not to say that it will materially improve stall characteristics, because there's more to it than that.

For my build, I've gone with the LLE fibreglass option. I thought about using an aluminium alloy LE as well, but decided against it because I wasn't comfortable in handling a long length of aluminium sheet without creasing it. I also suspect I would have to have joined it it somewhere along the span because of the limitation on sheet lengths.

In summary, for mine, investment in some form of LE skin is worthwhile, whether it be aluminium or fibreglass. But then aeroplanes have flown for decades without them so it comes down to choice. And I don't think there is a right or wrong answer either way. They're both relatively safe, performance issues aside.

FWIW.

[HighWing]

I appreciate the comments. I am in Chandler, AZ for a grand-daughter's HS graduation and time is limited - more when I get home. I purchased the leading edge material from Aircraft Spruce. Search Leading Edge. It comes in 12 and 18 inch widths and lengths that will accommodate our wings. Thickness is .016" it is shipped rolled - no creases or dents. Installing was a challenge - more on that later.

[HighWing]

I have to apologize for not fulfilling my promise for more info. Busy busy with returning home from Chandler and diving into a community yard sale all day tIinitialoday. Will respond as promised, but will likely take another day.

[HighWing]

At the time I was building, there was talk about a leading edge modification using aluminum. A buddy and I were building at the same time and we both talked about trying it. The aluminum (12"X144"X.016") was ordered from Aircraft Spruce and sent coiled. My aluminum had taken a set during storage or shipping and to help getting a snug fitting of the aluminum to the spar, it was placed along the leading edge of the wing with concave curvature up. Trial fitting showed that the aluminum didn't want to lay firmly against the decreasing curvature of the rib from spar to the end of the false ribs. Also, it wasn't long enough to cover the entire length of the wing. Those issues became the challenges.

The length issue was solved by cutting the strip so that it would terminate over the #2 rib. and when all was installed, using "Micro" to fair the surface into the wing tank surface. What eventually worked for getting it to lay firmly against the ribs was a series of - one on each rib - ratcheting tie-downs that extended over the leading edge, then sidestepping the rib at the trailing edge of the aluminum and around the aft spar and return. The aluminum could then be forced to conform to the surface curvature. The first thing that was done after the experiments was to rivet an aluminum "Z" shape near the trailing edge of the aluminum strip between each rib that would capture the wood stringer that the false ribs were designed to rest on. (For weight conservation, I decided not to use the false ribs.) The "Z"s were used to maintain the straight - level - surface of the aft edge of the aluminum while under stress from the shrunk fabric and the possible lift while in flight. A note on that. A neighbor and friend had built two Pitts and a Christen Eagle. In discussing the trailing edge "Z" he mentioned that on his builds, the manual called for using a "Joggle Tool" for rolling the trailing edges of the aluminum to essentially accomplish what I did with the Z.

The aluminum was scuffed in the areas of the leading edge and the rib capstrips and a hole cut out that would accommodate the fuel tank filler neck. It was positioned and Hysol 9430 was used to glue in the leading edge along the front spar. Several bar clamps were used to secure the leading edge temporarily while the tie-downs were positioned over each rib starting at the inboard end. Once the Hysol cured, the straps were loosened and Hysol was applied to the remainder of the capstrips - starting aft and working as far forward as possible, the"Z" strips were snapped over the stringer and the straps re-tightened. Early morning or the cool of the day will give more working time with the Hysol.

For aesthetics, I extended the rib lace tape and finish tapes to the front spars. This also helped mask the inboard termination of the aluminum leading edge at the second rib.

That's about it.

Internal showing one bay with "Z"
Leading Edge 3.jpg
Wing
IMG_2710.jpg

[David47]

Nice job Lowell. That "z" former you've attached at the aft edge of the LE with help maintain profile of the LE really well. I don't think I'd like to be trying to form a "z" section on the aft edge of the LE skin as in the other builds you mentioned. I think your solution is way better and you didn't have to fiddle around with recessing the "z" to clear each rib. In a way I wish I'd gone down this path.

[av8rps]

I agree that the Riblett wing works well as it is and therefore the LLE option is probably more for aesthetics than anything. Ive flown Avids with tbe same basic mod as the LLE and frankly couldn't decide if it did anything or not? But I have to admit they sure make tbe wing look better.

A comment just made about the newer wing being beefed up by adding ribs... can someone confirm the Model 5, 6, or 7 having more ribs than say a Model 4-1200? I've never known that, so I'm curious more than anything.

Paul