Leading Edge Question ...

[Moose]

Can anyone chime in on how they worked their leading edges, using the aluminum ribs, as to prevent them folding? I've heard stories about a couple clip wings with the nose ribs working the leading edge to a failure point?

I was wondering if scalloping the leading edge material in the area of the ribs would help strengthen and stabilize the leading edges? (Much like the Monocoupe wings did.)

Thanks!

[Hank Jarrett]

Re: Leading Edge Question ...

I'm not sure what the "nose ribs working the leading edge to a failure point" means. I didn't know we had any leading edges fail. Did the leading edge tear off to the spar like in WW-I planes or did the leading edge skin crack, or was it a fabric failure. I would be interested in any photos or information on the failure so we can determine the mode of failure and the initiation points. Once we analyze the failure we can determine the cause and make design mods to stop it.
Who has seen a failed leading edge and exactly what did it look like? Pictures would be a great help for an analysis.
Hank

[Acroeric]

Re: Leading Edge Question ...

A clip wing that has been flown especially hard will exhibit some flattening of the leading edge about 6" aft of the L.E. on the top side of the airfoil just fwd of the spar. To stop this on a clip wing you need to just make sure you use a false rib between each regular rib. Using .025 leading edged that creates a "D" section also helps.

[Hank Jarrett]

Re: Leading Edge Question ...

Can't imagine any better advice on making a strong wing than from Eric. He needs to post links to videos of his aerobatic flights. My planes leading edges might be able to take those loads, but my body couldn't!
Eric, have any of your planes had this happen? I would still like to see what it looked like. I also work with some WW-I groups and Fokker and Nieuport had problems with EVERYTHING ahead of the front spar ripping off! THAT scared me!

Hank

[Moose]

Re: Leading Edge Question ...

I've had two people that commented to me that I wanted to make sure the leading edges on my airplane are well secured, because they want to "work loose" and "fold up". Then Warren Pietsch made a comment similar, and being that he's had his airplane, it made me take more than a passing notice to the comment.

[Hank Jarrett]

Re: Leading Edge Question ...

There is NOTHING wrong with extra caution! You "done right" to ask. Anytime any of us thinks there could be a problem with these old birds we need to kick it around and make sure they are safe. Taylorcrafts have an OUTSTANDING safety record. Rarely does the plane fail the pilot, usually it's the other way around, but we want to keep it that way.
Hank

And make sure we make the pilots better too! There are only a finite number of planes AND pilots. We don't want to loose ANY! I am still interested in seeing any info or incipient failures. The guys flying aerobatics in the clip wings are testing the waters for the rest of us. ANYTHING shows up on ANY plane and we need to warn each other.

[Moose]

Re: Leading Edge Question ...

A clip wing that has been flown especially hard will exhibit some flattening of the leading edge about 6" aft of the L.E. on the top side of the airfoil just fwd of the spar. To stop this on a clip wing you need to just make sure you use a false rib between each regular rib. Using .025 leading edged that creates a "D" section also helps.

My wings are the "elusive" third set of "shorter than Swick" wings that Swick helped put together. They have wood spars, and stamped ribs. The spacing is about 8" - 8.5" apart (measured on center). There's no extra nose ribs in between. Should I add some before I put the leading edges back on? I would think 4" spacing of ribs on the leading edge would make it really stiff, but might be overkill for the weight addition.?

[Acroeric]

Re: Leading Edge Question ...

The stock Swick spacing is between 9 and 12" depending on the position along the spar if I remember correctly. I do not have the extra ribs in my Swick either and fly it pretty hard. With that said- I am also just running an O-200 and I keep it to 140 mph and +6G on a very light airframe. I rarely ever see above 5G and 140 mph is only while entering the box for a sequence. I am starting to plan the rebuild on N43740 and will add the extra nose ribs at that time. I am seeing some flat spots just outboard of my strut attach fittings. They have been there as long as I have had the plane and I have never seen them change. They are most likely handling damage from a wing rack but I do watch them closely.
My old Cole Tcraft did not have the extra ribs and it also had a much larger (180) Lycoming. I did collapse the leading edge on it. At the time I was observing a 160 Mph Vne. I exceeded it a little and felt a little "bump" during a pull to vertical. I landed immediately and found a small section of leading edge where the nose ribs were not ever secured to the leading edge and they collapsed. This was at least 10 years ago and I never photographed it. I did speak with Forrest at the time and he had encountered a similar situation. Maybe he can chime in. He is a really good clipwing driver.

If you plan to run the O-200 I would probably just use .025 leading edges and make sure they are secured to the top and bottom of the front spar. A stringer is also an easy addition if you do not want the trouble of extra ribs. Just make sure you use a mechanical means of attaching the L.E. to the ribs. If you are going with a Lycoming 320 or 360 you would want to add the ribs because it is easy to get well above 160. In the Hangar 9 Clipwing I am presently doing all the phase 1 flight testing. I just finished flutter testing to 180 mph and 4G pulls. It has doubled up nose ribs and is built like a tank. Even the spars are much larger in thickness than a Swick. No nose rib issues at all even at those speeds. For IAC and acro I will be observing a 160 Mph Vne in it as well.

One of the key weak points of the Swick design is the tail brace wire arrangement. If your fuselage is uncovered you would be really wise to address a few items while it is down.

[Moose]

Re: Leading Edge Question ...

I plan on running around 180hp on the front, and want to make sure the leading edges are addressed. I wonder if the slightly tighter spacing of these ribs (8", versus 10") would help overcome that, or if I should plan on adding some nose ribs for added structure?

Eric ... Would the problem with your leading edges on that airplane have been prevented had the ribs been secured properly?

MY airplane is stripped. It had been constructed with 8 streamlined flying wires on the tail, but I actually don't like the geometry of the attach points. I plan on reworking the tail a bit, as I am considering adding a little height to the vertical stab, as well as enlarging the rudder.

[Acroeric]

Re: Leading Edge Question ...

The way both sets of tail brace wires terminate to the same lug on the bottom of the fuselage is pretty silly from an engineering POV. I add a new vertical member and a seperate independant set of tail brace wire lugs for the front set of wires- this is located about 16" forward of the stock tail brae wire mount. It takes a little welding and careful placement due to the rudder cable exits but it adds significant strength to the tail. In some of my youtube videos where I had the tail mount cam watch it shake as I put stress on it. With the extra lugs for the tailbrace wires this totally goes away. I can send you some pictures of my tail mods if you wish. Pretty simple stuff.

As for the leading edges- I have never heard of a failure with the doubled up nose ribs. I'm sure it will look like overkill with just 8" spacing but it adds very little weight and the peace of mind of knowing you should not have to worry about it would be worth it. I can't stress enough the "D" section that the clipwing leading edges should be. You will need to add a strip of capstrip material between each rib so the leading edges can be attached top and bottom. When I built the all wood clipped wings I used a ply leading edge and after adding this it made the wing extremely strong. In fact- I had to be careful to trammel the wing exactly like I wanted it because after the glue dried there was not much ability to twist it.

[Ragwing nut]

Re: Leading Edge Question ...

Why no just increase the material thickness of the leading edge?

[Acroeric]

Re: Leading Edge Question ...

I already use .025. Going up another size gives a little extra strength but alot of weight and becomes really hard to form.

[Moose]

Re: Leading Edge Question ...

My flying wires on the tail need a little tweaking for my liking. The aft one goes from just in front of the aft tube on the horizontal stab, to the lower longeron near the tailwheel attach point. Which is pretty straight in line. The forward one goes from just aft the leading edge of the horizontal stab, forward to the lower longeron. I don't understand why that one isn't more square with the fuselage?

I'll send you an email to exchange some pics, Eric.