COZY: Cozy dry weight

Marc J. Zeitlin

Greg Norman wrote:

I have the first edition of the Cozy MKIV owner's manual. It shows the Cozy dry weight of 1050 lbs. I don't think I slapped on too much epoxy but geeze.

No one knows where Nat got the 1050 lb. empty weight from for the first plan-built COZY MKIV (not the prototype, which was narrower, although that can't have made a 10 lb. difference). I make the assumption that he weighed it with a day VFR panel, no lights, and no upholstery and possibly before it was painted.

The closest I've ever heard of anyone getting to that 1050 lb. empty weight was Al Wick, in his 165 HP Subaru flat-4 powered COZY MKIV - IIRC, he said his plane weighed 1075 lb. empty. On the other hand, after he switched to a bigger, flat-6 Subaru, his empty weight ballooned up over 1300 lb. I don't think the plane's ever flown since the engine change, but I could be wrong.

At this point I can't carry passengers with full tanks.

You don't say what your empty weight is. I can guarantee you that you will NEVER want to put 4 people in it and fill the tanks (and fly for 6 hours like that - the back seaters will have murdered each other before you land, and the co-pilot will be beating you over the head with your headset to get you to land). Now, if you're saying that you can't put ANY passengers in with full fuel, and full fuel is about 52 - 58 gallons, depending, then the 320 - 348 lb. of fuel plus 220 lb. of pilot, being 570 lb. total, give or take, means that your plane weighs over 1450 lb. empty.

If that's true, even with the O-540 engine (give or take 100 lb. more than the O-360), yeah - you've got a pretty overweight airplane.

Anyone care to report their weight with a 320, 360, or 540?

I've done a bunch of W&B's on COZY MKIV's. Most of them are somewhere between 1150 lb. and 1250 lb. empty. A few are a bit over 1300 lb. Mine is 1225 lb, including two O2 tanks and a second alternator, with a pretty full panel. Tim Andres' plane is just over 1200 lb, and Jon Dembs' is about that as well. They're both OSH award winners. I have NOT seen a correlation between quality of build and weight - some great planes are heavy, some great planes are light, some crappy planes are heavy and some crappy planes are somewhat less heavy.

Vance Aktinson wrote:

Gross wt of the plane is determined by THE BUILDER... the designer only recommends gross wt that he has tested (or calculated).

While this is absolutely correct from a legal standpoint, safety should prevail over legality. The COZY MKIV's POH lists it as a 3.8G aircraft at a MGW of 2050 lb. Should you choose to fly it (and therefore, TEST it during Phase I) to 2300 lb MGW (as a few people have), you'll need to derate the maximum "G" loading to approximately 3.4G. You'll also need to realize that you'll take a LOT more runway for takeoff, have to land faster and use more runway for landing, as well as derate the landing vertical velocity that's acceptable (most LG is designed for a 10 fps (600 fpm) decent rate - if you weigh 12% more, then you should derate your maximum landing vertical velocity by somewhere around that - to 535 fpm. Now, that's a pretty hard landing, and you probably won't want to do that more than once, but by having a heavy plane you're decreasing margin in just about all areas.

And the article that Bill Allen posted a link to by Dick VanGrunsven is one that I've referenced and quoted in every OSH Forum I've given since 2012. Extremely relevant.

Now, practically, since 95% of COZY MKIV flights occur with 2 people or less, some baggage, and have 3 - 4 hour legs max., the NEED for flying the plane over 2050 lb. is low. Even 1300 lb. COZY's can generally stay below that GW. 

Marc J. Zeitlin                      marc_zeitlin@...
Copyright © 2020                     Burnside Aerospace