Marc Zeitlin

After some prodding from Wayne Hicks, I did a bit more research to figure out where I got that 140F # from. Wayne wrote to me: >----> Reading chapter 25, room temperature cure epoxies soften and lose >rigidity at moderate temps. (160F.) Foams soften and swell at moderately >elevated temps. (250F.) That sure is what it says, doesn't it. For some reason, I thought that I had read that the wing foam had lower temperature capabilities. In fact, the Dow web page says that Styrofoam Brand Insulation's maximum continuous operating temperature is 167F (75C). Most of the "Last-a-foam"'s have a max. cont. service temp of around 200F. I'm not sure where I got the 140F from..... Aha - close. From, http://www.netcomposites.com/education.asp?sequence=47 the max cont. op. temp. of some PVC foams can be as low as 120 F, with processing at up to 150 F. So, Nat's probably not being conservative enough if folks would use his #'s for fabrication temps. At any rate, as long as you're not cooking your layups, either while bagging or not, you're extremely unlikely to harm the foam.

First, I'll say that I'm not a big proponent of vac-bagging for our aircraft - I just don't believe that the slight weight savings justify the extra work. Others disagree - that's fine. However, foam cores of the types that we use in our homebuilt aircraft are used regularly with wet layups and vacuum bagging, at the vacuum levels that Steve has indicated. Since the cores can withstand up to 140F, we can heat tent our parts to 100 - 120F while curing under the bag (or NOT in a bag) if desired with no problems. With respect to pulling air out of the foam and into the layups, there is no evidence that this happens. Measurements have shown good epoxy/glass ratios in foam core vac-bagged layups using standard techniques. In fact, it's FAR easier to get a quality sandwich layup using foam, micro, and a wet layup than it is with honeycomb core, which is a real PITA. This is all for wet layups - pre-pregs are an entirely different story. So, if you're willing to do the extra work for whatever weight savings there MIGHT be, don't be worried about these issues - there are enough issues to worry about :-).

OK, so once you've decided that the steering can be overcome with large enough forces, and will only be used at relatively low speeds, what's the advantage? Any large crosswind on takeoff at low speeds will require more force than the springs can provide, and you'll be castoring. I think that you'll find that if you set the springs appropriately, you'll essentially be castoring almost all the time, and steering only at very los speeds and very low turning angles. Plus, the steering can never have the throw of a castoring wheel, so your turning radius when steering will be much larger than your turning radius when castoring. We're not talking about heavy iron here - it seems as though small GA aircraft are moving away from steerable nosegear to castoring nosegear. There's a good reason for that - it's lighter, simpler, and works at least as well. So, yes, your system can certainly be made to work - of that I have no doubt. It will weigh a bit more, and it will be more complex, but it can do what you propose. I just don't see where any advantage is to this combined system.....

Accepted, and if I made you feel that I was attacking you with my responses, I am also sorry - that was not my intention. I'll be happy to discuss this with you in person at OSH, if you like. Sure. Let's say that you're either taking off or landing at a high density altitude airport, and you're relatively heavy. Your IAS on final may still be 90 - 100 mph, but at 6685 ft. altitude, on a hot day (say, at Durango, CO in the summer, like when I landed there last August with my wife, tons of baggage and full fuel), the density altitude will push 10K ft. That means that as you touch down (or rotate) at 100 mph IAS (which, in the COZY at gross weight and mid CG, is about the speed I needed to begin a climb), your TAS and GS, with no wind, will be about 120 mph. These speeds are realistic for LE's and COZY's - many canard drivers land even faster than this, although I'm not sure why. If you have nosewheel steering coupled to the rudder pedals, then as you attempt to maintain directional control using the rudders, you'll also be adding nosewheel steering inputs. The nose gear needs to be able to handle those loads at those speeds (and all lower speeds). These forces can be substantial as velocities get higher than walking speed. If you set the castoring breakaway so that it will castor at low enough forces so that you don't overload the nose gear and attach points at these speeds, then the question becomes "what is the nosewheel steering doing for you"? Make sense?

Nope. Not unless John Roncz kept the data (or Beech did). If the UIUC database doesn't have them, you'd have to go to the source.

The best you're going to get is from: http://agert.homelinux.org/~fredrik/flyg/aircraft.html which indicates that both the canard and main wing airfoils were custom Roncz designs - a Roncz 1085 on the canard, and Roncz 1107 on the main wing.

Most folks are not engineers (either school taught, or self-learned). The safe assumption to make is that the folks we're addressing are laymen. YOU will need to steer at 120, because YOU will have nosewheel steering on your plane, and YOU will touch down at 120 mph GS every once in a while. _I_ will only have to steer with something other than the rudders below 40 mph, although I have the capability of doing so with the brakes as well. If YOU attempt to steer with the brakes at your 120 mph touchdown speed, you will put a very large side force on the nose gear. If you put in springs that allow castoring with any substantial amount of force on the nose gear, then you will have defeated your nosegear steering purpose. Maybe you should think these things through before throwing the insults around when someone points out facts to you. So, someone other than you (cybersushi) starts this thread. Then, someone other than you (airwrench) posts a statement to which I responded, saying NOTHING about your particular design. You then take it upon yourself to assume ownership of the thread, as if no one else has a right to respond on it unless they get your approval, and you think that it's YOU that are getting happy horseshit? You don't know the history of the design you're building, you don't know what modifications have been attempted and/or discarded by other folks before you or why, you think that you're the only one that has the ability or drive to complete this particular modification, you admit that you insult me without knowing MY history, you DON'T address the valid issue of other aircraft that have castoring nosegear, and you think that I'M full of myself? At least I realize that I don't own this forum or thread, not to mention drive, ambition, and capability, and that everyone has a right to have their say, whatever it might be. Listen, Tony. You're obviously a bright guy, and you're attempting some pretty interesting stuff with your airplane, even if a lot of the changes seem to be for the sake of change alone. But I hope you succeed, because it would be cool if you do. However, jumping down people's throats and insulting them because they write stuff you don't want to read isn't going to help you any.

Actually, the Wright's were far closer philosophically to my position than to yours. They studied the existing theories, developed their own, tested everything they developed, and attempted to come up with the best, most efficient solution they could using the technology available to them at the time. They did nothing just so that they could be "different". They were engineers in the best sense of the word - they were NOT laymen, by any stretch. With respect to your nosegear, as soon as you have it built, mounted on your airplane, weighed, and tested to 120 mph on the ground, and it weighs less and works better than a castoring nose gear, I'll be happy to state publicly that you've come up with a better mousetrap. Until that time, it's hardly reasonable to state that your two drawings are an example of working steerable nosegear for a flying canard aircraft, any more than it's reasonable for Infinity to state it for their design. There are over 2000 examples of working castoring nose gear on canards - I was looking for ONE example of working steerable nosegear on canards. Can you point me to ONE? With respect to your attempted insults, I have almost never said "it can't be done". Almost ANYTHING can be done - the only things that can't are those that defy the laws of physics, which steerable nose gear certainly doesn't - the question is whether it's useful, reasonable, economical, or smart to do so. I was merely addressing airwrenches astonishment, when you stepped in with your insults and objections to reality. You haven't addressed the issue as to why Cirrus etc. have gone the castoring route. Are they all stupid, Luddite, anachronistic, neanderthal naysayers like me, too? I suppose I got my current job just so that Scaled could say that they had one idiot working for them - kind of an equal opportunity thing going on.

Says all the folks that haven't bothered to implement (or attempt to implement) the modification. Point me to ONE, please. My point was:a) It's non-trivial b) There's no demand Sure. A little shorter, maybe. But if you review aircraft with similar performance (Glasair, Lancair, etc.), you'll see that the TO distance is not substantially different. Most of the difference (if any) can be accounted for by the fact that our aircraft are canards (which intrinsically have longer TO distances), rather than that they have castoring nosegear. It might be, if there weren't perfectly good techniques that didn't require nosegear steering and it's associated complexity and weight to compensate. So, you'd rather greatly increase the complexity, weight and cost of the nose gear, instead of replacing $50 brake pads at the conditional inspection? I can buy a LOT of brake pads for the extra cost of the heavy, strengthened nose gear you're going to need to steer. The tire wear difference is inconsequential. Brakes fail, steering fails, nothing's perfect. airwrench. Go back and read his posts. I said nothing about the IDEA of nosewheel steering until airwrench stated that he was "astonished" that no one had dealt with this critical problem in the 30 years that these planes have been flying. If folks want to experiment with modifications that they think will work, more power to them, if they've done enough investigation and analysis to indicate that they can do the modification safely. I was trying to point out that there is no "problem". There are many ways to skin a cat, and castoring nose gear (as shown by the many aircraft, some of them very new designs, that use this technique) is one of them, as is steerable nose gear. Each has pros and cons. Given what seems to be a move (by Cirrus, Diamond, and Columbia [Lancair]) to castoring nose gear away from steerable nose gear, I'd say that the engineering tradeoffs probably favor castoring. Unless, of course, you know more than all the engineers at these three successful aircraft companies. Funny guy. You've obviously been paying no attention to the 11 years of arguments that I've had with Nat Puffer regarding various modifications to COZY's, nor the engineering analyses that I've done either supporting or not-supporting modifications, as the facts dictate. But hey, don't let facts stand in the way of your opinions - few others do. I've got modifications to my plane, and I've supported others with modifications to theirs, when it's warranted by analysis and testing. However, when someone claims that there's a DESIGN DEFECT with these aircraft when there isn't, I'm going to say something. I think having an objective, balanced view of any particular proposed modification is far more likely to result in success if the mod is attempted, or in a successful decision to not attempt it. You are welcome to attend and ask questions (or answer them) just like anyone else. You're hardly the first person to object to my pointing out that they don't have a full understanding of the subject of the discussion that they're engaged in.

Why is it astonishing that no one has "addressed" an issue that doesn't need addressing? Infinity has been threatening nosegear steering in their canard for over 10 years, but that's gone nowhere. If there are any canards out there that have installed nosegear steering, no one I've ever talked to has ever seen one. There's a reason for that - it's like trying to exterminate all the giraffes in Alaska - it's really not a big problem that needs addressing. Have you ever flown an aircraft with differential braking, like a L.E., V.E., COZY, Katana, Cirrus, Lancair Columbia or a Grumman Tiger? It's pretty simple. I can spin my airplane in it's own length - try that with nosewheel steering. The ONLY issue with differential braking is taxiing (and the early part of a takeoff run) with a strong crosswind, but there are relatively simple techniques for dealing with both of those. I don't know what airplanes you rent, but if you think that you can do any amount of steering at 90 mph using the nosegear, rather than the rudders, you're fooling yourself. The COZY rudders kick in at about 40 mph, and differential braking (or simultaneous braking, as the case may be) works at ANY speed.

Well, come to OSH, get a ride, get yourself psyched, and get started!

Lots of people know for sure. Yes, the Berkut is faster than the COZY. The Berkut type wings are essentially identical aerodynamically to the COZY type wings. The Berkut is faster because it's a smaller aircraft with retractable gear with a larger engine. There's no magic.

Folks: I am pleased to announce that Daryl Lueck and I will be co-hosting the COZY Forum at OSH 2006. We have not received the paperwork from Nat quite yet, so it's not clear what the day and time will be, but we'll announce that as soon as we get it settled with the EAA. So, two years ago, when I gave the forum last, I gave a very general history of the COZY, it's benefits, some building info, and some personal experiences with the plane. Last year, Nat gave a very good presentation on canard/COZY aerodynamics. Both of these presentations can be reviewed on the COZY builders web site. I've got a few ideas for things to talk about, but I would like to solicit ideas and requests from you all - what would you like to hear/learn/talk about, with respect to COZY's and/or canards in general? Info for prospective builders, info for builders, info for flyers, technical info, whatever - suggest away. If I need to do some research to address your issue, I will. Please reply directly to me via email at the address below - have at it.

What makes you think the gear legs are metal? I couldn't find a definitive answer, but: http://www.berkut13.com/berkut15.htm says: "The first step was to micro fill, and primer the gear legs -" You don't do that with metal legs. And "103 lbs."? That's a strange number to guess. From a semantic standpoint, sure. From a "make a decision regarding engineering data", uh-uh. If the guy that designed my wing spars put as much spar cap material in it as he did because it "felt" right, I'd chop the plane up and never get in it again. Either the Infinity gear is as good as the Berkut gear from a drop test standpoint (and since Infinity has published FAA drop test results, and Berkut hasn't, I'd say that if anything, it's better) or it isn't. Having "feelings" about it doesn't change anything.

I'm always fascinated when people have "feelings" about things like this. On what do you base these "feelings"?

Speaking of maintenance, why'd you remove the Islamic screed? I thought it was just so applicable to canards.....

You might want to search the COZY mailing list archives before making that judgement. There have been many discussions over the years on this technique, and it has it's place. When done correctly, the strength is more than adequate.

I'm with you - I think it looks like crap, but that's what makes the world go round.

That may have been the original theory, but the folks that have the dihedral canards say that they can't tell any difference whatsoever from the straight one. Mostly, it's for looks.

Thanks. I can see how the hydraulics could ameliorate that issue (if it was one).

Not yet. What would be the mechanism for this "de-coupling", in relation to mechanical actuation?

And you determine this how - by induction? Other than handwaving, is there ANY evidence anywhere that rotary engines (wankels) are more reliable, once built up into something usable, than piston engines of ANY type? If so, I'd be glad to see it, and glad to consider using a more reliable engine, with a longer TBO, believe me. But if all you've got is "well, it's obvious, isn't it", then that doesn't cut it in the world of science, evidence, and proof. Now, you're perfectly welcome to your religion, but admit that that's what it is. Other than having parts that move in a vaguely circular motion, there is no familial connection between gas turbine engines, which run on the Brayton thermodynamic cycle, and wankels, which run on the Otto thermodynamic cycle. One is continuous combustion, and one is intermittent. No comparison. Absolutely. But without the fuel burn or expense. But this has nothing to do with Wankel engines, because they're not gas turbines. I've flown 338 hours in the past 3.5 years. There are a couple of auto engine conversions in canards that have flown that much, and reliably, but it's certainly not the norm. I would have liked a Subaru in my plane, but I wasn't willing to be the first to do it, and given the lack of evidence of reliable operations of either Subarus or Mazdas in canard pushers, I'm still glad I went the direction I did. When you've flown 100 hours/year for 3 to 5 years running, without having to perform any major surgery, I'll be happy to consider copying your engine installation. Why, thank you for the permission. This thread was reanimated by someone asking about resale value. The answers that he got were accurate with respect to that - the resale value will probably be lower, but the cost of the build will be lower too. What was forgotten is that aircraft engines, over the past 5-15 years, have been APPRECIATING in value - you can sell a runout O-360 for what you would have purchased a 500 hour engine for 15 years ago. I don't think that has happened, or will happen, with auto engine conversions. Calculating the cost of ownership of a homebuilt aircraft is not simple - it is extremely dependent upon what assumptions you make regarding the cost of money, the appreciation rate of the engine and/or airframe, and many other factors. Maybe auto engines are more cost effective in the long run, and maybe not. I could cobble #'s together to prove it either way. Use an auto conversion if you like - there's nothing wrong with doing so, and you'll have a good time trying to figure out how to make it work (just as I did with my Lycoming engine). But don't do it on the false premise that there's some intrinsic advantage, either in reliability, cost, or fuel economy. All of those claims have yet to be substantiated by evidence. I have - a couple of times. One four cylinder motorcycle, and one car. No big deal.

Does anyone who keeps bandying about the claim that rotary's have only 3 moving parts have any statistics on how much less engine maintenance the Mazda rotary engine cars need in comparison to say, flat four opposed engine Subaru's? Or any other 4 cylinder car? Did Mazda EVER make any claims of their engines being more reliable than any other engines? I didn't think so.

In order to be able to ensure a reasonable level of O2 in the bloodstream (generally, saturated O2 levels of 90% or better for the brain to work properly, and over 70% or so for it to work at all and for you not to die), you need to have a "partial pressure" of O2 that's above a certain level. Since at all altitudes the O2 is about 20% of the air, as the air pressure goes down with altitude, so does the O2 partial pressure (this is why you get less O2 as the altitude climbs). Pressurized aircraft deal with this issue by ensuring that the pressure inside the cabin is always high enough so that the partial pressure of O2 is always within safe levels (commercial airliners pressurize to an equivalent of 5K to 8K feet, usually). Now, in an UN-pressurized aircraft, unless you're wearing a pressure mask or astronaut space suit, you'll be wearing a cannula or regular mask (like airliners have), so as soon as whatever gas is in the bottle comes out, it'll be at the ambient pressure. If it's just AIR in the bottle, then you haven't raised the "partial pressure" of the O2 going into your nose any, and it won't help your saturated O2 levels in your blood. If the bottle holds O2, then the gas entering your nose will be mostly O2 (along with some ambient air diluting it), so the "partial pressure" of O2 in your nose will be a lot higher than the O2 PP further away. This is good for your SpO2 (saturated O2) levels in your blood. SCUBA has the opposite problem - as you descend, the pressure rises, and if you use pure O2, you'll have TOO MUCH O2 in your blood, and it'll poison you. On the other hand, if you use plain air, then you have to be very careful about going too deeply, or the nitrogen can come out of solution as you ascend, and you'll get the bends. Gas for breathing in SCUBA gear has to be tailored carefully depending upon how deep you're going, and your ascent rate has to be slow enough to let the dissolved gasses come out slowly, if necessary. a) correctb) correct c) nope - hand layups COULD be designed to withstand the pressure - they just weren't in this case Hope this helps.

For what? Breathing? Pressurizing a cabin? Are you talking in general, or about COZY's in particular? COZY's are NOT pressurized (and cannot be). If you're talking about breathing in an unpressurized aircraft, then above 12.5K ft., you need oxygen, not pressurized air. It sounds like you're talking about breathing at high altitudes, so since you need O2 for that, pulling compressed air off the engine (either from a turbocharger or some other compressor) will be useless - you need pure O2. I know of no GA aircraft that have O2 generators on board - everyone (myself included) uses O2 tanks, which need to be refilled on occasion. The standard COZY fuel selector is L-R-Off. No Both. Same as in low wing GA aircraft, like a Piper Warrior. There's no magic about COZY fuel system. "Both" only works if you can guarantee equal fuel flow (and fuel return, if there's a return line). This is more difficult in low-mid wing planes. Hence the L-R-Off. Some folks (Steve Wright in particular) have put in LARGE cross flow tubes so that he CAN guarantee equal flow, and he also has a single point refueling port, with only an "on-off" valve to the engine. This is the simplest solution (but of course, means that there's only one fuel tank, in practice, so contamination or leakage leaves you with no backup. This is not a common problem, however, so the increased risk is small IMO). The COZY fuel system is no more complex than any other low wing GA aircraft.