Nat Puffer

Builders, The Cozy Mark IV design has grown in popularity each year. We were concerned about what would happen when Shirley and I were no longer able to carry on (our children are all in the medical profession and not involved in aviation). We considered it very fortunate that Aircraft Spruce wanted to purchase our copyrights and take over the sale of plans, and we wanted to make the transition while we are still able to help. So, effective January 1, 2004, Aircraft Spruce is the only authorized supplier of Cozy plans, and no one is authorized to copy and sell all or parts of the Cozy plans, without their explicit permission. We have agreed to continue to support builders as we have in the past, and publish the newsletter, and display our airplane at airshows. Aircraft Spruce will issue serial numbers for the plans they sell, and plans to revise the license agreement slightly to cover them as well as Co-Z Development. There has been a lot of planning, and we are hopeful that the transition will be smooth. We hope that you will look at this, not as our dropping out, but rather our bringing in help for the future. Best regards, Nat

Would like to comment on building time for plans vs kits and also empty weight for the Mark IV Build time: I have personally built 5 composite airplanes from plans. These were always part-time, either while working for 3M or drawing up plans and instructions for builders, helping builders, writing newsletters, etc. All were built in 2 years or less. I estimate 2500 hours on the 4 place models, and I was not able to buy pre-fab cowlings, turtlebacks, or other prefab parts. Phoenix Composites is located at Falcon Field. They assemble Glasairs, and maybe occasionally some other kits. I stopped by to watch. The Glasair is a very complicated design. The wings must be assembled in one piece from skins, ribs, baffles, spars, hardware, fuel tanks, etc. They use dedicated jigs. I asked Dace Kirk how many hours it takes them to assemble a 2-place Glasair. He said about 3500 hours and they charge about $130,000 for labor and on up. This is with experienced labor and dedicated jigs. One of our builders used to work for a shop that assembled Lancairs. I asked him about his experience. He said that putting a Lancair together from a prefab kit took 4,000 to 5,000 hours, and cost from $400,000 to $500,000. He must have been talking about the 4-place Lancair IV, but that is what we are comparing the Mark IV to, right? So we think that 2,500 hours for a Cozy Mark IV is a realistic figure (more so that pre-fab suppliers advertise), and less than most pre-fab kits, whether 2 or 4 place. I can't believe that some people would think that 2,500 is too long a time for a 4-place. Empty weight: Airplanes always increase in weight after the initial weight and balance. The weight on the dataplate is the weight before the first flight. Builders usually make their first flight before installing wheel pants, spinner, etc. Some even before painting or upholstery. In our case, the empty weight was 1050 lbs before wheel pants, before spinner, before lower winglets, and before the fancy upholstery job that Alexander Aircraft talked me into, with headliner, armrest padding, carpets, etc. I am sure we have added at least 50 lbs since our initial weighing. I have gradually thrown out parts of the upholstery. Be careful what you put in your airplane! Best regards, Nat

First let's address the "vehicle on its side" concern. A Varieze, Long EZ, and/or a Cozy overturning is an extremely rare event. We are talking upside down. I can only remember one Cozy that turned upside down, and that was caused by landing on a muddy field. With both the canard and the wings sticking out to both sides, I can't imagine how any of these designs could end up "on its side", so I think we can dismiss that concern. How big a hole can you cut in the panel? Remember, the panel is structural, but it was designed to cut holes in it for instruments. At what point does the hole become "too big"? That is sort of like the question "how strong should the roll-over structure be"? The only way to answer that question is, "how hard are you going to land up-side-down". I don't know when the hole becomes "too big". Everything is a trade off. The more you cut into structure, the more you weaken it. As far as a hole for an EFIS is concerned, obviously Greg Richter (Blue Mountain Avionics) has one mounted in the instrument panel of his Cozy. I think his unit is about as large as they come. Then there are many other EFIS designs. Some even mount in a 3-1/8 inch instrument hole. As far as the leg holes are concerned, I sit on 4-1/2 inches of foam and still have plenty of leg space. I designed my last seat cushions in several layers or sections, so I could accommodate pilots from small to large. I haven't seen a builder yet who didn't fit after the seat cushions were adjusted for him. I keep telling people that once they are airborne, they should take their feet off the rudder pedals and extend them, legs straight. Of course you can make the leg holes larger, but you give up panel space. That isn't too much of a problem if you are prepared to use miniature instruments, or use an EFIS like the new Dynon, which contains all the flight instruments including solid state gyros, which fits into a standard 3-1/8 instrument hole, and one of the new electric engine monitoring systems (like the Stern Pulsar) of a similar size which replaces all the old analog engine instruments. We find that some builders are concerned about things which they will later discover should have been of no concern. For most builders, all they have to do is to follow the plans.

Dear Questioner, We don't know exactly how many Cozys are flying, because many "first flights" are not reported to us, or if so, not until a year or two has passed. So the best we can do it to estimate the number based on the frequency that first flights are reported to us, with an allowance for those that are not reported. World-wide (because a lot are under construction around the world) we are guessing that about 360 III place Cozys and 60 IV place Cozys are flying. The exact number is probably not as important as the fact that there are a lot, we have had many reports of very satisfied builders, and no reports of dissatisfied builders. Hope this helps. Regards, Nat (the designer)

Dear Marbleturtle, Greg has a 3-place. It is smaller than our Mark IV. Please call me. Best regards, Nat

Dear Marbleturtle, Please call me. (480)981-6401.

Dear Marbleturtle, I have a suggestion. Why don't you contact BRS and tell them you wish to build a Cozy Mark IV, and you would like to install a BRS chute. Ask them if they could instruct you as to how to do it, would they guarantee it would work without totalling the airplane or injuring any of the passengers, and how much it would cost. Then let the rest of us know the answer. Best regards, Nat

Dear Marble Turtle, Please call me. We need to talk about this again. I need to make sure you make the right decision. Best regards, Nat (480)981-6401

Dear Marbleturtle, I am sorry if I offended you. However, I would prefer to be honest up-front in telling people what the limitations of our design are, rather than have them discover many thousands of dollars and years later that they have been mis-led. Here are the facts; 1) We have builders as tall as 6 foot 6 inches. I coach them on what simple changes, which I have approved, they can make to either increase the leg room or head room, or both. 2)We have builders over 220 lbs, in fact some 300 lbs or more, but I advise them they should make the front seat a bench seat, and either take up only very light passengers, or sit in the middle of the front seat with no front seat passengers at all. 3) The 400 lb limit in the front seat was my judgement call, based on c.g.and structural limitations. I and others have flown with more than 400 lbs in the front seat, but performance is degraded. It takes longer and a higher speed to rotate, and landing speed and distance is increased. Normal operation with more than 400 lbs in the frontseat is considered by me to be unacceptable. 4) Buying Cozy plans from someone else, or plans based on our design for an airplane that looks like ours will have the same limitations. If you are told differently, you are being mis-led, because we did the flight testing on this design. 5)I would rather not sell plans than mislead someone about the capabilities or our design. 6) As for BRS, it would take a lot of experimentation and testing with a canard pusher design to determin what it would take to make it work. This would be very expensive, because the airframe would probably be totalled, after deploying a chute and hitting the ground. It could not be proven safe without occupants during testing, which would risk serious or fatal injuries. 7) We have been flying over mountains now for 24 years in one or more canard pushers with aircraft engines, and I have never had nor could I visualize a situation where I would be willing to pull the cord, be completely helpless, and trust my fate to an uncontrolled touchdown in an uncertain location, particularly in the mountains. Again, if I offended you, I am sorry. Better that, however, than to mislead you. Best regards, Nat

John, It is not possible to access this Boston Globe article, so let's forget it.

There are at least 2 occasions we are aware of where the #4 pipe has not been adequately supported where it goes through the rear baffle, and it has fatigued and broke. A number of years ago, it happened to Mike Pinnock, who lives in Florida. He was flying over the Gulf and heard the sound of the engine change. When he reached land he learned that #4 pipe had broken, fallen down into the cowling, and the #4 exhaust had exited into the cowling. By the next morning the wings had sagged about 1/4 inch, leading edge down. What had happened, was that the hot exhaust had traveled along the centersection spar and exited at the end of the strake. The centersection spar had softened, which caused the wings to sag overnight. The second case, the builder had allowed about a 1/4 inch of space around the pipes where they exited the rear baffle, the pipes had vibrated, and #4, which is the longest, had fatigued, broken, went through the prop, broke a blade, and cause an emergency landing. Fortunately the pilot was able to reach a runway and the landing was executed safely. The designer recommends that there be no clearance around the pipes where they exit the rear baffle for 2 reasons. 1) We need high presure underneath the cylinders to force cooling air through the cylinder fins. If there is clearance between the pipes and the baffle, it will allow the air to leak out, reduce the pressure, and adversely affect cylinder cooling. 2) If there is clearance around the pipes where they go through the baffle, the pipes are not adequately supported, will fatigue, and brake. #4 pipe is the most likely to break, because it is the longest. If there is wear, either the baffle or the pipe, where the pipe goes through the baffle, the logical thing to do is to increase the surface contact. We recommend a 1/8 inch aluminum reinforcement of the baffle at that point. If that isn't enough, then 1/4 Inch. We also recommend that the two pipes on each side be strapped together with a hose clamp forward of the aft baffle, so that in the remote chance that one pipe might break, the other one will hold it from going through the prop. Lastly, it should be remembered that even for stainless steel, being repeatedly heated to 1500 deg F and vibrated is very extreme duty, and the pipe will not last forever, so it is very likely that it may have to be replace sometime in the future. The plans model Mark IV now has 600 hours on it and the stainless steel pipes still look good, probably because we have followed the above advice.

Dear Dale, I will apologize for my jab at you, but it was a reaction to what you said about me. Remember, that your engineering was more current than mine? That was completely uncalled for. I have worked in engineering all my life! I thought my comments were factual, and presented much data in support of updraft cooling as shown in the Cozy Mark IV plans. Apparently your interest in downdraft cooling has nothing to do with cooling, but rather that you believe the cowling design would be better. That could well be with the Long EZ, which is quite cramped, but not necessarilly true of the Cozy Mark IV. I believe Lycoming supplies engines for updraft cooling as well as downdraft, so it really doesn't seem to make a whole lot of difference to Lycoming which way the air flows. And the data I have shows that there is very little temperature difference across the engine anyway. So cooling isn't really the issue, is it? It is a scientific fact that air tends to rise as it is heated, so updraft cooling will always have that advantage over downdraft cooling. This can be very important in ground operations. It would be especially hard on an engine to climb at high power and low airspeed after it has overheated on the ground. If you find that there is some huge advantage in downdraft cooling (after you have demonstrated it), I am sure we would all be glad to hear about it.

Dear Niceeze, I see you are an insurance broker and fly a Long EZ. Good luck on your downdraft cooling. What problem do you expect it to solve?

Wheel pants designed for the Long EZ will require some modification to fit the Cozy Mark IV, mainly because the Mark IV struts are wider and the struts exit the wheel pants lower than on a Long EZ. What I did to make sure I had enough clearance between the tire and the wheelpants was to stick some 3/8 in. pvc foam to the tire at the spots which would come the closest. This provided clearance at the top of the tire, and also mounted the pants as low as possible. Low as possible will give the least drag, but can be very close to the ground when parked with the nose down, can bump the hangar door threshold when moving in and out, and can rest on the ground when parked on soft ground (like at Oshkosh and S & F). Both Vance and I found this out. So you may want to mount them with a little more clearance than 3/8 on top, and sacrifice 1 or 2 knots of speed. The Long EZ pants should be wide enough for the wheel, strut, and calipers. That is with Clevelands. Can't speak for something else.

I can understand David's concern, since he broke an exhaust pipe, it went through the prop, broke off a blade, gave his engine a pretty hard shaking, and forced a forced landing. The cause, I believe, was later determined to be that the pipes, particularly the long one, #4, which broke, were not adequately secured, so they were able to vibrate and fatigue. The situation was aggravated by the two pipes (#4 & #2) not being tied together, and too large a clearance around the rear engine baffle so the pipe could fall through the baffle into the prop. Soooo, how to prevent? The forward end of the pipes are attached to the exhaust port flange via a slip joint, which holds the pipe in place with strong, stainless steel springs (two per pipe). Then where the pipes go through the aft engine baffle, there should be zero (like no) clearance. Since both the pipes and the baffle are attached to the engine, there should be little, if any, relative movement. The baffle should be reinforced with 1/8 inch aluminum where the pipes go through, to maximize the support and minimize the wear. Next, on the side of the engine where the longest pipes are (the passenger side) there should be a shroud around the heat muff, which clamps the two pipes together, to minimize relative movement, if any. And lastly, one should clamp both pipes together on both sides of the engine (in front of the aft engine baffle) so that if one pipe broke, the other pipe would hold it from departing the airplane via the prop. All of these things, taken together, will greatly prolong the life of your exhaust pipes. However, these pipes, even though made of stainless, are repeatedly heated to 1500 deg F (red hot) and will not last forever. So it is good practice to inspect them whenever you remove the cowlings for oil changes or annuals. We do not know what the life expectancy is, but ours are still going strong after 500 hours.