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Marc Zeitlin

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Marc Zeitlin last won the day on June 25

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About Marc Zeitlin

  • Rank
    Flying Cozy MKIV N83MZ
  • Birthday 08/06/1957

Personal Information

  • Real Name (Public)
    Marc J. Zeitlin
  • Location (Public)
    Tehachapi, CA 93561
  • Occupation
    Principal - Burnside Aerospace
  • Bio
    www.mdzeitlin.com/Marc/bio.html

Flying Information

  • Flying Status
    Flying - 1300 hrs.
  • Registration Number
    N83MZ
  • Airport Base
    KTSP

Project/Build Information

  • Plane
    Cozy Mark IV
  • Plane (Other/Details)
    COZY MKIV
  • Plans Number
    386

Contact Methods

  • City
    Tehachapi
  • State/Province
    CA
  • Country
    United States
  • Email (Visible)
    marc_zeitlin@alum.mit.edu
  • Phone Number
    978-502-5251
  • Website URL
    http://www.cozybuilders.org/

Recent Profile Visitors

56 profile views
  1. Marc Zeitlin

    New Facebook Group for Cozy Mk IV Pilots & Builders

    Because two mailing lists, two web fora, and multiple generic facebook pages (which are horrible places to attempt to actually collect information) aren't enough?
  2. Marc Zeitlin

    Kent's Long-EZ project

    First, I am always impressed by Kent's willingness and ability to make stuff that most folks just purchase. Second, you might think that a CHT probe should last forever, but I've had two or three die on my over the course of 15 years. I have (for the past 10 years, anyway) used Dynon probes with my Dynon EMS. So for CHT probes, I HIGHLY recommend using bayonet mount probes (which the $38 Dynon probes are), since you can install and remove them with a quarter turn, and it's easy to adjust the compression of the spring to achieve good contact. Having worked on many engines that have the probes screwed into the head, it's a total PITA to install/remove them, whereas installing the bayonet mounts themselves only requires a long, large slotted screwdriver - the probes themselves install with fingers into the adapters. My $0.02.
  3. Marc Zeitlin

    Turbo Normalized

    So Dick Rutan had a turbo O-360 on his Berkut for a couple of years. It was a nightmare of trying to cram 43 lb. of sh*t in a 3 lb. bag, as well as having 36 lb. of heat from the turbo to dissipate in a 2 lb. heat dissipation bag. There just isn't enough space in an EZ cowl for the turbo, heat shields, and extra exhaust tubing (and still leave enough space to pour a pint of 100LL). He eventually removed the whole thing for an O-540, and is much happier with the performance and maintainability. If you're going to have water cooling and a radiator/water hoses, I cannot imagine (on an EZ - MAYBE on a COZY MKIV) where you'd stick a turbo and the associated extra hardware as well (intercooler?), with any access to anything. My $0.02.
  4. Marc Zeitlin

    Can she be salvaged?

    Maybe. Some hardware - axles, wheels, brakes, nose gear casting, firewall belcrank, rod-ends, etc. But it all depends on their state of corrosion and/or weather exposure. Might be worth something, might be a pile of crap.
  5. Marc Zeitlin

    Can she be salvaged?

    A beat up Varieze, with deteriorated fiberglass/epoxy both inside and out, and no records of the build or who the builder is/was. and 60% to go. No engine, no systems, unknown wing attach fitting status (look up Varieze Wing Attach Fitting issues). Anything can be done/repaired/fixed/completed. The question is how confident you would be in the result and whether it's worth the effort and cost. Since you don't know anything about these planes by your own admission, you are not out of your mind for considering it. If you DID know a lot about these planes, THEN I'd say you were out of your mind. Walk away from this disaster of a smoking hole and look for a Long-EZ or COZY project if you want to finish something someone else started, or just start a build from the start yourself if this is the type of plane for which you're looking. My $0.02.
  6. Marc Zeitlin

    More epoxy & glass questions?

    If you're going to build a LE or COZY, you should review the documentation for approved materials. There is a list of approved epoxies in the CP's and COZY newsletters. Proset 125 with 226/229 hardeners are approved epoxies. If you can get it for $90/gallon (including the necessary hardener), you should become a distributor. ACS sells resin gallons for $119 and hardener 1/3 gallons for $75 - $85. So a "kit" is about $200. I just bought 5 gallons of 125 from CST Sales for $104/gallon, and the 226 and 229 hardeners were $72 per 1/3 gallon. What's nice about the slow hardener (229) is that you get a nice long pot life with low viscosity for easy wet-out, and with even a low grade post cure get a reasonably high Tg and HDT. Even without a defined post-cure, the HDT is around 130F. IIRC, I used about 10 - 12 gallons of resin (not counting hardener) for my COZY MKIV, not counting West 105/205/205 for the micro finishing.
  7. Marc Zeitlin

    More epoxy & glass questions?

    So my first question when folks ask about different materials, etc. is "What problem are you trying to solve"? The airplane does not need to be stronger - no Long-EZ or COZY has ever had a structural failure in flight when built anywhere near the plans specifications. Unless you're going to use non "moldless construction" methodology - meaning building molds and using vacuum bagging type techniques, you're not going to substantially reduce the amount of epoxy in the build. You can't substantially reduce the thickness of most of the layups, because strength isn't necessarily the driving factor - damage tolerance on fuselage and wing skins is. So you're really not going to make them any lighter by changing cloth or epoxy - you could use lightweight engines, instruments and systems and save a lot more weight than you ever would with layup changes. Whether a fiberglass weave is measured in oz/sq-yd or in thickness is meaningless - you need a certain amount of glass to provide the stiffness/strength/puncture resistance required. Using Carbon in a contact (non-vacuum bagged) layup for structure is contraindicated, so unless you're going to bag everything, you should not use carbon (and it's way more expensive than glass, negating one of your goals). Kevlar is right out, as it has really crappy compression capabilities. There may be one or two places where a bit of Kevlar could be useful (under the nose puck for scraping resistance, for example), but nowhere else. So the short answer is really "no". Unless you're going to redesign the airplane to use different materials or build techniques (and it's been done - see the Berkut, which doesn't weigh any less and usually more than a Long-EZ) you're not going to be able to make the build time shorter, the airplane cheaper or stronger by changing materials. Feel free to argue the point - many have over the past 25 years - but none have shown one instance of any of their arguments holding water. These planes are what they are, and they're pretty well optimized from a design standpoint with respect to a balance of build time, cost and structural capabilities.
  8. Marc Zeitlin

    Aircraft Epoxy, Marine Epoxy what's the difference?

    Nothing, because there's no such thing as "Aircraft" epoxy or "Marine" epoxy. There are epoxies that designers have chosen based on their properties to ensure that the specifications of the device in question (aircraft or boat) will be met. If you use an epoxy that was not approved by the designer, then maybe those specifications won't be met, and you may either fall into the water or out of the sky. Since you're interested in LE's or COZY's, there is a clear list of approved epoxies that can/should be used, and you should pay attention to it, particularly to the fact that the best epoxy for the strakes/fuel tanks is the EZ10/87 due to its fuel resistance capabilities. There are reasons NOT to use particular epoxies as well - the West 105/205/206 are NOT approved due to the low pot life and high exotherm probability on structural (read thick) layups. In the grand scheme of things, the cost of the epoxy is a tiny percentage of the total cost of the aircraft - don't skimp here.
  9. Marc Zeitlin

    Red coloring after anodising 2024T3

    I hope that you are not anodizing any structural aluminum parts - only cosmetic ones...
  10. Marc Zeitlin

    Resin and Glass

    https://www.aircraftspruce.eu/composite-materials/fiberglass-cloth-tape/cloth/rutan-fiberglass-cloths.html
  11. Marc Zeitlin

    Chapter 13

    So..... how did you install a COZY MKIV strut / electric gear on your plane if you didn't have the COZY MKIV plans to work from? In any case, if you don't have a set of plans, find a COZY builder/flyer somewhere near you in OK (yes?) or TX or KS or NM, etc. and take a look at theirs. Or spend $500 and buy them from ACS, or find someone with an electronic PDF copy of the Aerocad plans for Chapter 13 (hint) and ask them (via private email) to send you a copy (via private email). The Aerocad plans are functionally identical to the COZY MKIV plans.
  12. Marc Zeitlin

    Varieze Canard Bolt Torque and quick disconnect pins

    Does it occur on the ground at 2K RPM? If you bring the engine to idle in the air, then accelerate again, does it happen at 2K RPM? What's "low frequency"? Do the canard tips oscillate at the low frequency? Is it only a "buzz" in the seat of your pants? How pronounced is the vibration? Bad enough that you can't read the instruments? Have you looked at the engine mount rubbers to see if they're in decent shape? Is there something loose in the airplane that's flapping around? As you change IAS, does the frequency of the vibration change? If you decelerate through that speed range at 1800 RPM, does the same thing happen? If you decelerate at speeds below 140 mph ias but at 2K RPM, does the same thing happen? If you accelerate through that speed range at any RPM, does the same thing happen? Have you asked Chris or Burrall about this? They've got about a zillion hours in that plane together - I'm sure they know it like the back of their hands... Without feeling it, hearing it or seeing it, it's VERY hard to say if there's even anything abnormal, much less what it might be...
  13. Marc Zeitlin

    Varieze Canard Bolt Torque and quick disconnect pins

    Unless the POH for the engine or the airplane states a restricted area for continuous operation, no. Generally, RPM restrictions are put onto engine/prop combinations, not an engine alone (although there are always exceptions). And since there's no way for the designer to have a clue what prop you're going to have, Burt didn't put any restrictions on RPM for the O-200 on a VE. OK, so precision in language will help a great deal in diagnosis. We couldn't possibly begin to discern what an airplane that "feels not happy" might mean in the context of vibration, aerodynamic behavior, oil usage/leakage, canard/wing/winglet motion, control system forces, or any of the other things that might not be optimal on an airplane. Nor what "210 to 140" means. IAS? TAS? Kts? mph? Descending? Climbing? Precisely what are the symptoms, and under what circumstances, and how do they differ from what the airplane does in other circumstances?
  14. Marc Zeitlin

    Varieze Canard Bolt Torque and quick disconnect pins

    Good enough. I'm slightly suspicious of the values noted in the document - they seem high for fiber lock nuts. But I've never done a study, so I can't say for sure. You would add some torque based on the value the torque wrench measures before the bolt/nut is tight. The "tare" torque of lock nuts is actually pretty low after the first installation. Even for metal locking nuts, the MAXIMUM tare torque for 1/4-28 nuts may be around 30 in-lb for the first install, but then drops to around 2.5 - 5 in-lb for subsequent installs. See Page D-38 of this document: http://tinelok.com/wp-content/uploads/2013/09/IFI-100-Prevailing-Torque-Locknuts.pdf for more info. The fiber locknuts will be lower in "tare" torque, so I'd say to ignore the tare torque if the nut's been used before and still can't be turned by hand, and use the torque wrench measured value of "tare" torque on the first installation. But it certainly can't hurt to see what torque is required on the torque wrench to turn the nut/bolt prior to getting tight, and then add that value to the required torque value to get the necessary reading on the wrench. For further confusion, Table 7-2 of Chapter 7 of AC-43.13-1B gives minimum prevailing torques (tare) for AN365 nuts, but only for nuts larger than 7/16" (go figure). But the 7/16" nut has a minimum value of 8 in-lb, which would lead me to believe that the AN4 (1/4") nut would be in the 3 - 5 in-lb range, as indicated above. So, if you're shooting for 50 - 100 in-lb as a range, and you set your wrench to 80 in-lb, you can't go wrong - you won't break anything and you'll have more than enough torque no matter what the prevailing nut torque or nut type is. Is this getting any clearer? :-).
  15. Marc Zeitlin

    Varieze Canard Bolt Torque and quick disconnect pins

    Good question. Because on further reflection, although the canard lift tab bolts are in single shear, part of their purpose it to put substantial friction force between the lift tab and F-22 in order to transfer the lift loads. Because, if the F-22 was build correctly, there's an AL bushing that the bolt/nut squeezes (and the plans call for an AN4-12A bolt, not a 13A, so be careful that you're not bottoming out the bolt threads) you can't crush the foam/fiberglass structure of the F-22 bulkhead, I think that it's better to go tighter than just a "bolt in shear" level. But I don't think that there's anything unsafe about the 50 - 70 in-lb range - you just get more margin if you go to the maximum capability of the bolt and nut, which is 100 in-lb. I'm sorry for revising my thought process as I went along and confusing you. As long as you've got more than 50 in-lb on the bolt, you'll be safe. Sadly, the plane (VE, LE, COZY) don't spec a torque for these bolts, which are just about the most important ones in the plane :-). So that table you found is 1/2 of Table 7-1 in Chapter 7 of AC43.13-1B (downloadable from the FAA, and an indispensable reference tool). It's only the torque levels for bolts in shear - it doesn't show the maximum allowable torque limits for bolts in tension, which is where the 100 in-lb. comes from. Unless there's some good reason to use some random document found on the web (like the AC doesn't mention the issue and there's no other master source), AC43.13-1B is the canonical document for aircraft maintenance. You won't crush the structure of the VE if the bushing was installed during the build process, but you WILL deform the bolt, possibly stripping the threads and/or stretching the bolt. 100 in-lb is 8 and a tiny bit ft-lb, so yeah - 10 ft-lb (not 10 ft/lb) is way too much and will harm the bolts. Sorry for confusing you and changing the story midstream. Basically, in this case, anything between 50 in-lb (lowest # to use for bolts in shear with an AN365 nut) and 100 in-lb (highest # to use without harming the bolt/nut) will keep your canard on the airplane safely. Which is why I rarely use a torque wrench to install the bolts - once I know by feel with a certain wrench how much 100 in-lb is, I just go somewhat less than that, and call it good. Hope this is clearer than mud.
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