Izzy’s Cozy Journal - Monday, March 01, 2004

Wednesday, July 7, 2004

I started this entry on July 2^nd. With the holiday arriving, I haven’t been able to finish until now. Since the last time I’ve written, I finished the newsletters. I’m impressed at how much time it took to go through all of them.

Additionally, I’ve finished reading Zeke Smiths Book and am happy to report that the $30 investment was sound. It’s helped me understand the Spar and Spar cap, the reasons behind the various shapes and techniques in structural design. I’m able to look at all sorts of aircraft components and see the engineering in the design. The book also touched on the different materials and helped explain why fiber glass is strong and plate glass is not. In addition to learning about vacuum bagging I learned about mold construction and mold making. It’s interesting to note that Aero Canard is offering their molds for the Cozy for about $45,000. I would be interested to see them sometime.

With my new found knowledge and advice from Mr. Maddy and others vacuum bagging has passed into the ideas that will stay on the shelf for this Cozy project. The cost and weight savings do not seem important in the case of this builders bigger picture.

Since last update, I’ve finally purchased my original set of plans. I was a little disappointed that I didn’t get Nat’s signature in them, but perhaps I’ll get him to sign my owners handbook at Oshkosh this summer. Armed with all the newsletters and a pretty good idea of where to look for things, I embarked on the update process for the plans. It was tedious and took about 20 total hours but I got through it. I discovered some anomalies I’ve reported to the group. You can review the consolidated Updates for Third Edition Plans here or on Mr. Zeitlin’s site.

My education continues with the recent purchase of the FAR/AIM 2004 edition. I’m hoping to get through that as I wait for a break in the financial weather to continue building my Cozy. You’ve probably been wondering why I’m still screwing around with reading and not actually building. The sad truth is lack of funds. I spent everything extra I could spend (and then a little more) getting the plans, some of the tools and parts for the Beemer. Of course the Beemer is still in the garage, but now a little closer to the point I can begin reassembly. The major undercarriage components have been powder coated (Red Baron Red of course!) Now I’m waiting for about $800 in bushings and another $400 for miscellaneous parts. It’s beyond the point of “is it worth it.” I have to finish it and get the car back in running order. I’m betting it will be the end of next month before I’ve gotten everything done that needs to be done on the car. Then I can start construction.

So obviously, I’m not going to make Chapter 4 by Oshkosh. But at least I can still read and study the AIM. I would still like to at least do the Bookend sometime this month.

I’ve joined the local EAA chapter 129 and have had the opportunity to meet some interesting folks. I’ve been cooking pancakes on Saturday mornings and learning where all the cheap instruction can be found. For example, I was informed of a local FBO that provides training in a C-152 for $52 an hour. Some of the instructors don’t even charge. On the high end, I’ve found a flying club that provides an airplane ownership for a $500 buy-in and a minimum number of hours per month.

I’m going to Oshkosh and have convinced my Dad to come. We’re going to crash the place on a Saturday for about 9 hours. I’m hoping it rains so the crowds are less and the heat is less. We’ll see. I’m hoping we can go see the Rutan presentation on Private manned space flight. Speaking of which, I should probably go check out the Scaled Composites website to see why the tail cone buckled on reentry (if that’s what happened) and learn more about the pitch trim freezing up. And how does this Feather work? I wonder if he will publish that information.

Among the other details to be done this month include a new flight medical and a “getting back into it” flight for later.

To finish this month’s entry, I would like to include a discussion on Brake Technology I posted to the newsletter board this evening. It is my impression that the brakes and rotors that are available for the Cozy were not designed specifically for canard aircraft. The following talks about some of the technologies that could be incorporated to improve the margin of error for Cozy Pilots and other Canard aviators who might land a little fast and need some brakes on occasion.

Enjoy!

Izzy

Brakes…

Catching Warbirds

I remember working as an End Of Runway (EOR) specialist in the Air Force catching and disarming F-16's returning from missions and getting a "hot pit re-fueling." Sometimes Pilots would land with Mk-84 2000 pound bombs and near full loads of fuel for one reason or another and use a lot of brakes on landing. One of the procedures I was required to perform was to take a wax stick that melted at 700 degrees and touch it to the brake rotor on the fighter after it landed. If the stick melted I would test the rotor with a 1,200 degree melting stick. If the 1,200 degree stick melted the jet was parked to the side for 45 min or so until the brakes had a chance to cool down. At that temperature, it could ignite fluids such as fuel and hydraulic fluid. I had heard horror stories of Airman approaching the hot tire from the side immediately after a pilot would land. The rotors would transfer heat into the high pressure nitrogen that was in the tires and cause the pressure to be so high that the hub would split in two and blast the poor guy in half. The proper approach would be from the rear of the aircraft under the wing. It was really hot under there with the APU and engine exhaust and the hot tires. And a little scary of course.

Anyway, here is what I've learned about the topic of brakes. This was prompted by a web discussion and the many other stories I've heard of struts warping after hot landings and high speed taxies. Of course the best option is to use the rollout all the way and not get heavy on the brakes. In an emergency one could drop the nose gear.

So, I understand the presently accepted and recommended procedures and limitations. I also know that people can get a little wired or excited and maybe come in a little hot. It seems that recent technology advances in brake technology should provide some options for our unique gear configuration that could help us widen the gap between hot brakes and melting gear. Here is what I've learned. Please forgive any plagiarism. I'm short on time and want to get the info out. References and sources are posted towards the end.

Rotors and Heat

Rotors dissipate heat in two ways: Volumetric Displacement and Thermal Dissipation.

Volumetric uses the mass of the rotor to absorb the heat energy. A larger the mass of the rotor the more heat it can hold (to be dissipated in the convection and radiation process). This is the only way that a solid rotor can lower its temperature. Thermal dissipation uses a vented rotor to pump air through the center of the rotor to reduce the core temperature. The number of veins and their configuration is a major factor in determining how much and how fast heat is dissipated. A vented rotor also uses thermal dissipation.

Air Cooling through Vents

Vented rotors work by allowing air to enter the center of the rotor and sucking that air through the interior of the rotor by the pumping action of the curved veins (impeller action) in the rotating assembly. The first known use may have been in 1966 on the Ford GT that won LeMans that year. The primary types are the Pillar vane (comprised of many small posts) and the Curved vane.

Temperatures between the pad and disc do not normally exceed 700F even in heavy street use. In race use 900-1200F is common on smaller cars and in Championship Cup race temps. shoot up to around 1500F where discs will glow red or orange. As an educated guess, I suspect our Cozy would probably not exceed 650 degrees. Anyone ever measure this?

Rotors made from carbon and carbon composites (formula cars) dissipate heat rapidly. For a car, the changing torque output of the rotor varies widely with temperature variations creating unpredictable handling for a car on a race track. However, an airplane will stop from high speed once on landing and the airplane does not have to repeat heavy braking such as on a curving race track. Titanium or Carbon Ceramic rotors would be fantastic for aircraft applications. These rotors are very light and are great for certain limited applications, but are costly. The Titanium doesn’t dissipates thermal energy as well as other metals.

Drilled and Slotted Rotors

For many years most racing rotors were drilled. There were two reasons - the holes gave the "fireband" boundary layer of gasses and particulate matter someplace to go and the edges of the holes gave the pad a better "bite". Unfortunately the drilled holes also reduced the thermal capacity of the discs and served as very effective "stress raisers" significantly decreasing disc life. Improvements in friction materials have pretty much made the drilled rotors less important. However there are differing opinions. Brake warehouse reports that a properly cross drilled rotor can increase cooling effectiveness by as much as 40%. In terms of temperatures the claim is 200 to 250 degrees cooler. Most of today’s racing rotors currently feature a series of tangential slots or channels that serve the same purpose as the cross drilled holes. The tradeoff is that Cross drilled rotors may be more likely to develop cracks between the holes.

A note about brake fluid boiling...

For applications where boiled fluid is possible, it's recommended the fluid be replaced with at least a 550 degree non-silicone brake fluid and make sure they are bled properly. Brake fluid is hygroscopic in nature - given any chance at all it absorbs water. A fraction of one percent of entrapped water lowers the boiling point of any brake fluid dramatically - and causes corrosion within the system. Replace all of the brake fluid in the system at least once a year - more often if you constantly use the brakes hard.

Coatings:

Swain Tech adds a Thermal Barrier Coating to various brake components to protect and insulate various components and "wick" away heat to specific parts of the braking system.

Conclusion

There seems to be technologies available to us that can reduce our risk and increase the safety and utility of our aircraft braking system. Perhaps with enough encouragement, the canard community can get together and encourage the major brake manufacturers to adopt some of these very valid and well developed technologies to help us improve our margin of error.

References and Sources...

http://www.thebrakeman.com/rotortech

http://www.stoptech.com/whitepapers/brake_systems_and_upgrade_selections_122701.htm

http://auto.howstuffworks.com/disc-brake.htm

http://www.brakewarehouse.com/brkewrhsefaqs.htm#top43

http://www.swaintech.com/htbrakes.html

H. Dittrich and R. Lang, Finite-Element Analysis of

the Thermal Loads Acting on a Passenger Car Brake

Disk, Automobiltechnische Zeitschrift, Vol. 86, No. 6,

pp. 265-269, 1984.

A. Fukano and H. Matsui, Development of Disc-

Brake Design Method Using Computer Simulation of