Marc Zeitlin

There are no brakes that might have been used for a LE that would be appropriate for a COZY MKIV, or even a COZY III.

These will be the highest loads that this pin sees, and they can be VERY large. You've got a moment arm multiplier too, from the force at the wheel (think about landing in a 5 degree slip, and the forces created at the wheel by that, and then multiply by 3-5 or so) to the force at the pin. That force should be far lower than the landing forces described above. The pictures, though a bit blurry, show a very clear brittle fracture of the metal right through the stress concentration (factor of three) caused by the roll pin drilled hole. The 45 degree "divot" running across the fracture face could be one of a number of things - inclusions in the metal (what's the metal? High strength steel? Low carbon steel?), crack initiation points, manufacturing defect, etc. Here's what I surmise is going on. The main pin that broke is installed in the gear leg and retained with the roll pin. _IF_ the main pin (don't know the official name) was a perfect, zero clearance fit into the gear leg hole, then the pin would be in single shear as force was put on it in BOTH directions (since the force direction changes with left or right turning forces from the gear). The roll pin area would never see any stress. However, if there's clearance in the hole (and more clearance is worse), the pin would be in an oscillatory bending mode as the forces went one way and then the other - think about the case where the pin was 1/8" smaller than the hole - it would have to bend to resist the forces on it. Even a few thousandths of clearance MIGHT be enough to cause large bending stresses. Turns and bumps while taxiing and taking off/landing would put hundreds/thousands of cycles on this pin, at possibly very high force levels (depending upon runway/taxiway condition, crosswinds and manufacturing tolerances). The stress on the pin from bending will create tensile stress, which leads to stress cracks at the stress concentration (roll pin hole). Eventually, the crack grows, and then bang - one more cycle of stress while turning and hitting a small bump - the material fractures at the stress concentration and stress crack. The side of the pin inside the drag link sees similar issues, but since there's a spherical bearing, no roll pin hole, and a retaining clip on the end, the stresses in that side of the pin will be far lower than in the fixed side of the pin. I would suggest a design fix, since this seems to be clearly a design and manufacturing issue, but I"m just speculating here and won't suggest anything unless I could examine all the parts myself and take a bunch of measurements.

One of the major issues in landing gear design is spin-up loads, for which an estimation process is given in FAR 23, Appendix D, section 23.1. These may be a large factor in applying loads to the system. However, since the gear collapsed under a side load, it's likely that there had been fatigue of the pin at the drilled hole, and the side load imposed by going around the turn was just the straw that broke the camel's back. Without knowing more about the exact design of the drag brace/downlock system, it's impossible to speculate on how the loads are imposed and what the design issues might be.

If you believe that a high performance aircraft such as a Lancair will have substantially (or any) shorter runway requirements than a canard aircraft, you're mistaken. There's no substitute for wing area when looking for short takeoffs and soft field performance. Looks and aesthetics are not a reason to choose an airplane that doesn't meet your mission requirements.

Wet, in this context, means prior to cure or green stage. Not the quantity of epoxy in the layup. Enough to keep it flat and bonded well. A few shot bags distributed across the surface should work well - 5 lb. each or so. If there is a foam surface touching glass/epoxy, it should be micro'ed. The doubler foam should most certainly have micro squeegeed on it prior to attachment.

Not really. It's how you interpret it. So, what that means is that the some of the engineers who worked on the SS1 program left Scaled and became the core of ICON. There is no claim anywhere that Burt had anything to do with ICON, and he didn't. The statement SHOULD say "...designed by folks associated with the SS1 program..."

Not just hard, but essentially impossible. I've had people send me pictures of their layups and then I've seen the actual thing. Many times, I've had diametrically opposed opinions as to what was going on after seeing the real thing. I don't even bother to attempt to diagnose layup issues from pictures anymore. Light angle, focus - there's just no utility in it. Being one of those people that encourages peel ply usage everywhere (and believe me, Scaled peel plies EVERYTHING), you are stating your opinion about weight - that's not a fact. In my opinion, you can get a lighter layup with peel ply usage - I find that I do a much better job of squeeqeeing out excess epoxy and air, while ensuring a good surface for both secondary bonding and finishing. Jury's out - until someone does a honest weight study, it's all handwaving.

So all of that tends to support my contention that the theoretical improvement in yaw capability with split rudders is small if existent at all. Interesting info, and good that it's consistent with the Cl info I saw via the NASA reports/book. Drag-wise, that's what I would have expected - not much difference at high deflection angles. So, back to doing it for aesthetics and/or protection from cross-wind breezes and banging around.

Understood. There will be no loss of effectiveness, but the INCREASE in effectiveness is questionable, and that was the original rationale for the modification. Because the lift predominates. If the L/D ratio of the vertical stab is 20 (wild guess with the rudder extended), then even if the moment arm (discussed below) is a factor of three different, the lift component will still dominate. I agree that Todd is usually correct. I will also state that his claim is not necessarily in conflict with the claim of a 5% higher maximum Cl, if the split flap changes the lift curve slope. It's also possible that various sets of data indicate various things, depending upon how the experiments were done - i.e., flap %age of chord, aspect ratio of wing, etc. Three times as much drag is a claim I'd not heard before - I'd certainly be interested in references for that. As you state, without doing some superposition calcs on lift and drag, it's hard to say what the overall effect will be. It may be a little more effective, if at all (my guess), or it may be somewhat more effective. It's very difficult for me to believe that it'll be a LOT more effective. One very simple way of testing this would be for someone (if I were flying now, I'd do it, but I won't be for a few months) with a standard rudder installation to fabricate a 3 BID "plate" that backed up the standard rudder, and hold it on with some aluminum tape. Install it on one rudder without changing the installation in any other way. Extend both rudders to the maximum extent (equally), and see if or how much the plane yaws. Done.

In theory, and not by much. NASA reports indicate a maximum Cl for plain flaps (what the regular rudder is) of about 2.5, give or take, theoretically. They also indicate a maximum Cl for a split flap of about 2.6, give or take, theoretically. BFD, IMNSHO. Unless someone's done some testing on standard vs. split flaps on Long-EZ winglets and gathered ACTUAL Cl data, I wouldn't bother modifying anything based on a theoretical increase in Cl of 0.1, which would be unmeasurable and unnoticeable anyway. My guess is that the EZ/COZY rudders don't generate anywhere near that level of Cl anyway, since the rudder is far less than 30% of the chord, and you never get to the AOA's that would generate those numbers because the slip angle would be crazy. In that case, it's hard to imagine that the lift curve slope for the split flaps would be any different at all from the plain flap. Now, if building from scratch, as Mr. Mann is doing, and it's not really any extra work to do the split flap over the plain flap - what the hell - it doesn't hurt anything, and does have a couple of advantages - aesthetics, and more importantly, the rudder won't flap around (crappy pun) in the wind, since the breeze can't get at the back surface to push it off its stop. I might consider it for those reasons, but not for extra effectiveness - if it increased the crosswind capability of the airplane by 0.5 kt, I'd be really surprised.

It's an AeroCanard molded kit, but why it has two huge holes in the front left side of the fuselage, I don't know. But it's definitely an AC.

Everything Kevin said about what Lycoming intended is true, but modified or not (there's no such thing as "de-certified"), there is no requirement to do anything to an engine that is not used for commercial purposes just because it reached some arbitrary hour limit. In other words, unless the airplane is being rented (or something equivalent commercially), you can run it as long as you want, no matter what the TBO is - the TBO in that case is merely advisory. Many people run their engines well past TBO. What ad?

I'm fascinated when people lose the ability to discern irony or sarcasm without emoticons. What have we become?

Why do you ask?

Yup. Polycarbonate (the generic name for which Lexan is one trade name) is a lousy material to use for this purpose, for exactly that reason - it scratches really easily. Acrylic (the window and canopy material, usually referred to by one trade name - plexiglas) is a far better choice, not least of which for the reason that it CAN be polished if it does get scratched, which it will do far more slowly than polycarbonate. This has been discussed many times on the COZY mailing list and is in the archives. People think "Oooh, Lexan is bulletproof - it must be a good material for windows". But it's not - at least in this case. Especially for a window on the bottom of something that will have other crap put on top of it. Big mistake.

It's not conditional on anything. It's a "Condition" Inspection - an inspection of the condition of the aircraft. Not "conditional". Not conditional. Not conditional. Not conditional. Did I say it wasn't a "Conditional" inspection, but a "condition" inspection? Don't know if I've mentioned that. And yes, I've got a copy of the CI checklist I use at: http://www.cozybuilders.org/docs/

See Lynn's comment above. The gloves are NOT impermeable. Stuff DOES get through. The more epoxy you get on your gloves, the more gets through. If the gloves were made of aluminum, then I'd say "use the gloves to smear on the epoxy all you want". But they're not - they're Nitrile, and they ARE permeable. Far better than latex or vinyl, for sure, and not as good as Butyl (the thick butyl gloves are the only ones that I would EVER consider getting epoxy on as a matter of course). If you use disposable gloves, you should be changing them every 1/2 hour or so even with incidental contact. Don't stick you hands in the epoxy on purpose.

After which I hope that you are immediately removing your gloves and replacing them with fresh ones, unless you're using thick butyl gloves.

Since the only reference to a 12" radius on the wing/winglet blend area was originally (at least to the people that I worked with, in the OSH presentations, and on-line that I've seen) mine, I ASSUMED (as I clearly stated in my posting) that you were referring to my recommendation. If that's not the case, I'd certainly be VERY interested in seeing whatever other reference you have for a 12" radius.

Apparently not.

Wayne, you wanna use potential crap on your plane, go right ahead. When I talk to 10 people who've used a material and 1/2 of them tell me that it's failed in one way or another, and I talk to 10 people that have used another material, and none of them tell me that they've had any type of failure, and then I ask another 10 who've used each, and I get the same types of answers (multiple failures of one, and none of the other), I can infer that the failure rate of one material is far higher than the failure rate of another. I did not pick the sample population - it's random - I just ask folks what they used to paint their planes when I see the plane, and I've certainly heard many tales of SP being used successfully. But it's clear to me that the failure rate is far higher than for other systems. Why? Don't know, and don't care. If it's only possible to use successfully with a skillset that most homebuilders don't have, then it's not something they should be using. At any rate, since there are many other, just as good, materials out there that don't have high failure rates, there's no reason not to use them. And Scaled is quite familiar with A-basis, B-basis, and material allowable issues associated with composite laminates, as well as FAR requirements, thanks.

Vinyl is as useless with epoxy as latex is. Please read the multitudinous information in both the canard-aviators and COZY mailing list archives. Butyl or Nitrile gloves for epoxy protection are what you want. So? If 95% of the people that use it don't have problems, then only 5% will have problems. But if 5% have problems with SP, and only 0.1% have problems with standard primers and paints, which one would you rather take a chance on? But your "number of batches" is somehow more meaningful? Would you like to know the upper bound of failure rate for a single failure when using a population size of 10 or twenty, with a 95% confidence level? Look it up. It's the number of failures that matters - not the number of successes, and like I said, I've got a list of actual failures - not hearsay. No luck involved at all - it's statistics, and the stuff fails far more often than alternatives. Not all the time, by any means, and the failure rate is still relatively small, but it's FAR higher than anything else out there.

In other words, you were one of the lucky ones. Other people have had miserable results with the UV SmoothPrime, and I can give you a list of names if you'd like, on COZY MKIV's alone. In other words, you are one of the lucky ones, as Mike Melvill has been. Please do NOT use your luck as an indication that it is reasonable for ANYONE to assume that they will be as lucky as you if they are as reckless, which is exactly what you have been. Barrier cream is useless. Good gloves are the only localized protection, and good organic vapor masks or air flow hoods are the only systemic protection for long term exposure. There was a very good discussion on the canard-aviators mailing list on this exact subject recently. It amazes me, with what medical science knows about allergic reactions, their severity and the causes, that anyone is willing to take the chance of getting epoxy on their bare skin on a regular basis.

And if you can get BMW, MB or Porsche to paint your plane with their paints in their booths with their robots and processes, and bake it in their ovens, then you will get the results that they get. If you use the airplane waterbased paints available in the US, you won't.

I would strongly recommend against using either Smooth Prime OR any water based finish. I know of at least five people (myself included) with COZY MKIV's alone that have had major problems with both. While certainly not guaranteed to have a problem (there are numerous reports of people using smooth prime sucessfully, although I have never heard of a successful report of a water based top coat produced for airplanes) it is far more likely to have a problem that with using standard auto or boat type finishes, some of which can be rolled/brushed. The COZY archives are replete with stories of the problems with Smooth Prime and the Top Gloss water based top coat (which I used, and am now peeling off for a repaint, which John Slade did a few years ago as well). Polyfiber took the Top Gloss paint off the market due to the acknowledged issues. It's beyond me why they continue to sell the Smooth Prime. They currently recommend an epoxy primer (which, no surprise, they also sell) as a coating OVER the smooth prime prior to application of ANY top coat. If I were you, I'd remove as much of the smooth prime as is reasonably possible and go with a standard coating. That's what I'm currently doing to my plane.