[Cozy MKIV Information]
COZY NEWSLETTER #47
Table Of Contents
Extensions are designed to withstand the normal vibrational loads imposed by the engine-propellor combination, as long as these loads are not imposed at the resonant frequency. The resonant frequency is the natural frequency a part would vibrate when struck (like a tuning fork). If loads or stress are applied at the resonant frequency, the loads or stresses are not damped out, but become additive, and can eventually build to a high enough level to fail the part in fatigue. Mike Melvill has been making a vibrational analysis on his Long EZ with an 0-360 Lycoming, 6" Brock prop extension, and a Great American propellor, and found the resonant frequency to be approximately 2750 rpm. He has accumulated 1300 trouble-free flight hours on this combination, which he attributes to the fact that he does not exceed 2600 rpm in cruise.
We normally select a propellor which will not overspeed (not exceed 2700 rpm) at full throttle cruise. In fact, we have our high-rpm alarm set at 2700 rpm, and generally cruise at a lower rpm, in the 2450 to 2500 range. A propellor which will not exceed 2700 rpm in cruise in a high-speed aircraft like a Cozy will not produce more than 2400 rpm static (full throttle, standing still on the ground). The builder-pilot whose extension failed said he was able to get 2600 rpm static with his propellor and over 2800 rpm in cruise at full throttle. If the resonant frequency of his propellor-extension combination was somewhere between 2700 and 2800 rpm, and the same as the rpm that he cruised, it would explain why the extension failed. What do we recommend to prevent this type of failure on a COZY?
Given that the power pulses on an 0-360 Lycoming are particularly harsh, we wouldn't want to make matters worse by having a bent crankshaft flange, which would cause the extension to wobble, or an unbalanced propellor. We would suggest that the run-out of the propellor flange on the extension should not exceed .002", and you should check your propellor for balance, not just for static balance, but also to verify that both blades are identical. For sure we would want to avoid running our engines at the resonant frequency of the extension-propellor combination. Mike says that on his airplane with his propellor, the resonant frequency for the Brock extension is about 2750 rpm, and that he considers speeds up to 2600 rpm to be safely under the resonant frequency.
On our plans Mark IV, we are using an extension by Woofter Mfg. (1951 NW 84th Terrace, Pembroke Pines, FL 33024 (305) 436-9496), which is a slightly different design than Brocks, and stronger at the propellor flange. We don't know what the resonant frequency is, however, but Mike is going to measure this. Woofter advises that if we desire, they can thicken the wall to provide an additional safety factor on strength. By increasing the stiffness and mass in this way, it would also move the resonance frequency farther above the approved operating rpm range of the 0-360 Lycoming. We will keep you apprised of future developments.
We made a brief stop at Boise, ID to stretch and you know what, and then continued on to Everett, WA, where we were greeted by Eric Westland, a Cozy Mark IV builder. Everett is only a short distance from Arlington, and Eric and his wife, Victoria, had invited us to stay with them. We inspected Eric's Mark IV project, which was about 50% complete. We were very impressed with the fine job he was doing. The next morning we flew on to Arlington, which was just a short hop away. Ken and Carol Murphy showed up shortly after we arrived in N44CZ, the Mark IV prototype.
We very much enjoyed the 3 days we spent at Arlington. The weather was wonderful, and the scenery was beautiful. The fly-in was very well run, and we were made to feel very welcome and at home. We departed Arlington Sunday morning, to fly across the northern states to St. Paul MN, where we spent a few days with our daughter and her family. Then up to Duluth for a fly-in there. The fly-in at Duluth didn't have many home-builts in attendance, but it sure had a lot of military heavy-metal.
After Duluth it was back again to St. Paul to visit more family, and then off to Oshkosh. For all this flying, we were blessed with very good weather. Ours was the first Cozy to arrive at Oshkosh, and a short time later, our good friends, Gene and Carol Davis, arrived in our 3-place Cozy prototype, N22CZ. All in all, 15 Cozys arrived at Oshkosh. Some were parked in the camping area, and Mike Pinnock was a bit intimidated by the Oshkosh traffic, so he parked his Mark IV at Fond du Lac. Doug Koster flew his brand-new Mark IV to Oshkosh, and it was gorgeous! We heard that he won an award for best plans-built, but this must have been an error, because it wasn't reported by Sport Aviation. He should have won!
This year the weather on the east coast was socked in for a couple of weeks at Oshkosh time, so some of our Cozy friends were not able to make it to Oshkosh, and we missed them! The Cozy builders forum was well attended. Several high-time Cozy pilots talked-Walt Suminski, Dennis Oelmann, Chris Esselstyn, and Vance Atkinson. Also, Bill Peterson of Superior Aircraft Parts attended and assured everyone that they were still serious about marketing an 0-360 engine kit.
We had 104 people attend the Cozy banquet on Saturday evening at Robbins. The meal was family-style with 3 different entrees, and the food was plentiful and very good. The Pershings had arranged door prizes, and a very entertaining speaker, Barry Dawson, a Brit who built his Cozy in France, and had a hilarious story to tell about his bouts with the French bureaucracy. We have had several very complimentary comments from prospective builders about the very friendly Cozy "family". Thanks to the Pershings for the banquet arrangements!
Monday noon we had a little ceremony at the announcers stand on the flight line, conducted by Greg Anderson, Vice President of the EAA. The occasion was our donation of the 3-place prototype, N22CZ, to the EAA museum. It will be displayed in the EAA museum at some future date. Later that evening, when we were dining with the Davises at Nick and Joan's Supper Club in Appleton, they had heard about it, and told us our dinner was on the house! The Davises, who had flown N22CZ up to Oshkosh, had to return to Arizona commercial, sans Cozy. Thank you, Gene and Carol.
As we were leaving Robbins restaurant Tuesday evening, the manager, Mark Haigh stopped us and asked if we had seen the August 8th issue of Time Magazine. There was a one-page report on the EAA fly-in, with a picture of Gene Davis examining the engine of Cozy N22CZ, and a quote from yours truly at the end of the article.
We left Oshkosh on a Wednesday, and this time the central states were socked in by a low pressure trough. We detoured to the east and south to get around the worst of it, but it completely closed in on us before we could get to Albuquerque. So we overnighted at Tucumcari and continued on in the morning. At Albuquerque we visited friends, Herb and Jane Peterson, who are building a Mark IV. Their project also looked very good. It is encouraging to us to see so many people doing such good work! We finally arrived home August 6th after a month on the road (in the air), and after a very wonderful trip!
Enclosed please find a photo of our Cozy Mark IV. I completed this project in just under 21 months and am currently flying off the forty hour requirement. My first flight was on 5/12/94 and it was a great feeling to be up in the sky again. Three attempts at landing and I was successful. Since that time, I have found that landing takes precise speed control for successful landings on a 3,000 foot runway. For my aircraft, the approach at 75 KIAS seems to work well.
My Mark IV has a 180 hp Lyc. with a 64 x 76 three blade propellor, and weighs in at 1,040 pounds. At this point in the testing I have taken her to speeds of 178 knots, without wheel pants, and have climbed at 1,800 fpm. Needless to say, I ain very pleased with the performance and have really enjoyed the open view that I receive from the design of the canopy.
I would like to thank you and all those associated with the EAA for making my first attempt at building an aircraft a successful one.
See you in the sky!
David and Vicky Higgins
Pembroke Pines, FL
Thank you for a wonderful Cozy banquet at Oshkosh this year. This was our first time in attendance and we were thoroughly impressed by the family environment. At the banquet Todd Winegar won a coupon for 3 Cozy decals. Since Todd doesn't have an airplane yet, he gave the coupon to me. I would like 3 Cozy decals to brighten up our white aircraft. Our Cozy N5310L is flying well and we should have our time flown off by the end of the month. If you ever get up to eastern Washington, you are welcome to stay at ffie Runyon.
Here is a photo of Cozy N151JE, completed in just over 6 years. It would have been finished in half that time, but I underestimated the time demands of building a new house. My Cozy flies just great, and the first flight was 5/15/94. To date I have 7.5 hours logged, and I have taken a year off from teaching at Prescott College so I can fine-tune the Cozy and build up some flying time. Thank you for all of the much-appreciated help.
James B. Edwards
We have recently noted that one of our suppliers is promoting an epoxy called "Poly Epoxy". It has not been tested and approved by the Rutan Aircraft Factory nor by us, and when we studied the physical properties, they do not appear to be as good as Epolite 2427. It is therefore not recommended!
Polyester resins, commonly used in boatbuilding, are not recommended, nor are vinyl resin systems.
With polyester resin systems, the ratio of catalyst to resin is not critical, because the amount of catalyst only determines the rate of cure. With epoxy resin systems, however, the ratio of catalyst to resin is very critical. Think of the resin as bolts, and the catalyst as nuts. To get the designed strength (and resistance to solvents), it is critical to have the same number of nuts as bolts! Therefore you must strictly adhere to the mixing ratio stated by the manufacturer. It is an advantage that Epolite 2427 has exactly the same mixing ratio as the Safe-T-Poxy it replaced.
Now we have arranged with Gulf Coast Avionics to help on the avionics installation. Gulf Coast is pretty well known in the avionics business. They sell all of the major avionics lines at greatly discounted prices, just a little over their cost. We are partial to the Bendix/King line, which is top of the line and which we have used for years. King has introduced a Crown Series, just for home builders, or you can also get the Silver Crown Series as well through Gulf Coast. Gulf Coast will sell to Cozy builders a radio stack, with the trays mounted together with sockets installed in the trays, and with a wiring harness with the ends clearly labeled and ready to connect to the switch and breaker panel, mic and headset plugs, antennas, etc. In other words, a complete avionics package ready to slide into your panel and hook up. They also carry a complete line of electrical supplies, like wire, cables, connectors, etc. If interested, you can get more information by contacting:
Brad Miller, Gulf Coast Avionics 4243 N. Westshore Blvd. Tampa, FL 33614 Phone: (813) 879-9714
Thank you again for receiving me as a guest in you home. I wanted to meet you and talk about the airplane firsthand before purchasing the plans. I enjoyed meeting you and really appreciate you indulging my questions. The demo ride was an unexpected treat as I had only hoped to just sit in the Mark IV! Thank you also for the ride back to Sky Harbor. I'm looking forward now to construction, the first flight, and being a member of the Cozy family.
Please send me your info. pack. I just started dating a beautiful woman who is also a pilot. We are anxious to get started on a plane. This may be the tie that binds.
Dear Nat & Shirley,
I just discovered that I neglected to renew my newsletter. I do have an excuse...his name is Brian Adam Mackowiak, just over two months old. The news of his "flight plan" last fall caught me, my wife, and 13 year old son by surprise. We had just given away the last of Jason's old baby clothes and stuffed animals, figuring we would never need them again. We have been busy getting our house ready to sell, because now we need a bigger one.
It looks like I'm going to need a bigger airplane! I had the opportunity to finally fly a Cozy at the fly-in in Rock Falls IL. It was very nicely built, nimble and extremely responsive. I was impressed. Brian's birth seems to have clinched it; I need to build a Mark IV. So I will have to sell my 3-place plans to offset the cost of Mark IV plans. Let me know if you have any interested parties.
Glendale Hts. EL
Progress on my Mark IV is proceeding forward slowly. There are times when I don't think I'll ever see the light at the end of the tunnel. Fortunately, I enjoy the building process as much or more than flying itself. I've got the Cozy on the main landing gear and am nearly finished with Chap. 13 (nose). The canard is built - kind of. I still need to make the modification from your c.g. testing. I got the good news in your newsletter one week after completing the canard - guess it's better to find it out now while mods can be made, rather than later when we are flying. My main spar is also complete. Hope to see you at Oshkosh once again.
I have been reading your plans and adding the changes from the newsletters. So far I'm impressed with what I have been reading. I am assisting a friend to build a KR-2, who wishes his plans were written as comprehensively as yours. I plan to start building after I complete my check ride for my private license in July. I will be the first member of EAA Chap. 52 (Sacramento) to be building a Mark IV, and the members with composite projects are anxious for me to get started. Have a wonderful trip to Oshkosh, and some day I will meet you there.
Quent K Toyloy
Please continue my newsletter for 2 more years; I thoroughly enjoy reading each issue. You certainly have advanced sport aviation with your design and intense flight test programs. I've never seen data as extensive as your c.g. data on any of the popular 2/4 place kitplanes -- I wonder why?)
Dear Nat & Shirley,
Good to see you and the Mark IV at Sun 'N' Fun. Brought my girlfriend this year to see the plane. She spoke with Shirley for awhile. I don't know what she said, but THANKS! She now is all for building a Mark IV.
So .... here's my check for $500. Please send the plans.
W. Palm Beach FL
I must confess that after a bout with what I thought was an epoxy allergy, I had given up on the project and was dallying with a more conventional design that was less expensive, but had 3 less seats. Without even batting an eye, I threw out ten years of wanting a canard IFR platform and took a giant step backwards to tubes and wood. This might have continued to my completing an aircraft only to discover it wasn't the one I wanted in the first place, except for three things:
The first was taking my son to Ins first airshow (he was 4 weeks old). I noticed that the only airplane that Nicholas (my son) was interested in was a beautiful Varieze. It could have been because it was so very WHITE, but I prefer to think he inherited his father's aesthetic sensibilities.
The second was comparing the plans for the two aircraft I was considering. With the Cozy plans I had a good support network of builders and a proven design, along with COMPLETE plans that explained things in an EZ to understand manner. In the other design, I had an incomplete set of blueprints (second package to follow on completion) for an aircraft where only ONE was flying, and a support newsletter that was sketchy at best. I also ran the numbers on how much the two aircraft would cost, and the Cozy came out on top.
The third was our phone conversation. Since then I have started using a barrier cream that is sold at TAP plastics and ceased using latex gloves. This seems to have eliminated my problems.
Anything this easy to do (building a Cozy) has to be either illegal or immoral. Best in all things,
Dear Shirley & Nat,
Enclosed are the pictures I took at the "Cozy Prototype Donation Ceremony". Richard Randall and I are charging ahead on our Mark IVs,. Oshkosh is always inspirational, particularly the Cozy family.
May 31, 1994
Dear Nat and Shirley,
I'm really pleased with your aircraft (Cozy MK IV. I've had a chance to fly the 3-place Cozy - it was a wonderful experience! I'm really glad to see the work you have put into the plans and instructions. I'm helping a friend build a MK IV and it seems to go together very easily and per the plans.
I intend to build one of my own in the near future - but for now I'm still in the planning stage. I am planning to purchase the plans at Oskosh '94 and I look forward to seeing you there. Thanks for all the hard work and dedication!
June 6, 1994
While my visit to Sun & Fun was too brief, I enjoyed the time spent. Late Saturday afternoon several builders retreated to the shade of Mike Pinnock's Mark IV and an exchange of bualding experiences poured freely. The fraternity was biulding and I felt like a brother to these guys!
While on a recent business trip I was able to detour "slightly" and visit with John & Becky Wilemski in Mason, Ohio. John's Mark IV is a credit to the breed. I talked to him again a few days ago and he is working on the main gear. He does such nice work that I have no doubt that he will continue to progress at a constant pace.
As for my own Cozy, I am putting the final touches on the engine cowling installation. This week I will collect a small army to invert the fuselage; for the last time, and finish the bottom. I have decided to take your advice of painting the bottom while inverted this final time. I have made my choice of paint; Ditzler Durethane in Juenue White. All of the covers for the interior are complete. Now if I can con my mother-in-law to stitch up the upholstery ..... This long, sleek airplane in my shop is taking its final shape. Thank you for your support.
I enjoyed seeing you again at Lakeland - my Cozy is coming along slowly but surely. I am doing as much as possible in the interior before attaching the center spar, starting on armrests, etc. Please send me an Owners Manual. My theory is that reading about flying the Cozy will help keep me motivated (although my wife already believes that spend entirely too much time "buried in the basement").
Thanks again for making the dreams of so many people attainable, by providing plans for a great airplane.