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cozy 3 weight & balance query


jforeman

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Hi all. Newbie Cozy driver and forum member!!

so, i've got this Cozy 3 in the UK. Looks fab, flies better :o) but i have an 'issue' with calculating CG. the owners manual quotes 2 datum points for the pilot station. the first is 59" aft of datum in the text and table (which corresponds to the Long-Ez datum point) the second is 65" aft of datum using the scaled half diagram on pg38. if i run the numbers using the 59" it doesn't work! the pilots position measures at 65-67" in the airframe.

 

can anyone shed any light on this anomaly?? was there a typo when translating the Long-Ez manual for the Cozy originally?? am happy to accept email to jamie@jforeman.co.uk

 

thanks all, J

Do or don't do, there is no try: Yoda

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Hi all. Newbie Cozy driver and forum member!!

so, i've got this Cozy 3 in the UK. Looks fab, flies better :o) but i have an 'issue' with calculating CG. the owners manual quotes 2 datum points for the pilot station. the first is 59" aft of datum in the text and table (which corresponds to the Long-Ez datum point) the second is 65" aft of datum using the scaled half diagram on pg38. if i run the numbers using the 59" it doesn't work! the pilots position measures at 65-67" in the airframe.

 

can anyone shed any light on this anomaly?? was there a typo when translating the Long-Ez manual for the Cozy originally?? am happy to accept email to jamie@jforeman.co.uk

 

thanks all, J

The 59" number is a closer number but because it is a homebuilt aircraft the only way to really know is to do a W&B on that aircraft. here in the United States it is required to do a W&B and determine the exact pilot position. the manual is meant to be a guide only and assumes that the aircraft is built exactly the same as the plans. In my aircraft the seat is moved back 8" and my seat station is at 67".

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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hello, thanks for taking interest. i may be providing evidence for my own ignorance here but... dont you need the pilot position before carrying out the w&b? to establish the moment?

out of interest, at which point did you measure your 67"? where the seat back joins the floor? did you measure back from the instrument panel, the canard bulkhead or forward from the wing join? i have no plans to compare to so any help is appreciated.

regards...

Do or don't do, there is no try: Yoda

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hello, thanks for taking interest. i may be providing evidence for my own ignorance here but... dont you need the pilot position before carrying out the w&b? to establish the moment?

out of interest, at which point did you measure your 67"? where the seat back joins the floor? did you measure back from the instrument panel, the canard bulkhead or forward from the wing join? i have no plans to compare to so any help is appreciated.

regards...

the instrument panel in your cozy 3 should be at 40". the seat station should be measured by weighting the plane empty and finding the empty CG and then put in a pilot and use the now loaded weight and CG shift to calculate the location of the actual pilot station. if your plane is built to the plans it should be at 59" with an average pilot of 175 lbs.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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Did you get a pilot handbook with the Cozy III? There is a pretty good explanation of how to work through the weight and balance and the datum point to start with. As i recall, the starting datum point was the intersection of the strake and wing at the leading edge. I suppose that was used because it's the best verifiable point nearest the wing center of lift.

 

You don't need a pilot in the seats to figure empty W&B but you have to add pilot weight and moment when calculating various flying CGs.

 

It's a good exercise to reweigh your airplane. No telling if the original W&B was correct and how it has been altered over the years. The Cozys are a little tricky because you may have to place weight on the nose during the weighting process to hold the nose down. I used to put it right on top of the nose tire. Makes it easy to subtract the moment for the extra weight to arrive at empty C of G.

-Kent

-Kent
Cozy IV N13AM-750 hrs, Long-EZ-85 hrs and sold

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Lots of talk,in the past, about the 3 scales to be used for this. Maybe there a EAA chapter somewhere that has some quality scales you can check out. Racing scales can be found at various Mazda racing groups [most popular racing league worldwide], and etc. Renting them would be good vs. buying the buggers as good scales are a must.:)

Self confessed Wingnut.

Now think about it...wouldn't you rather LIVE your life, rather than watch someone else's, on Reality T.V.?

Get up off that couch!!! =)

 

Progress; Fuselage on all three, with outside and inside nearly complete. 8 inch extended nose. FHC done. Canard finished. ERacer wings done with blended winglets. IO540 starting rebuild. Mounting Spar. Starting strake ribs.

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Follow the directions closely. Gear has to be all the way down---longerons have to be level (use wood under the nose gear to level---but make sure you either reset the scale to zero with the wood on it (or subtract it and the moment out)---make sure it is level left to right.

 

You will probably need some ballast to hold the nose down----make sure you subtract that weight and moment out also.

 

If you have a "standard" EZ, the inst panel will be at a known location---you can determine the pilot seat location from there by measuring.

 

It is not complicated---making a spreadsheet really helps when you want to play around with different configurations (especially for a Cozy).

 

I carry a quick reference graph with me that shows me how much ballast I have to put up front for various pax weights sitting next to me. For the most part, I don't worry about how much fuel and pax in the rear seat since it is pretty near the CG. However, I built my ref chart with the changes in fuel and rear pax weight in mind (the ballast weight is always conservative).

 

Since that last paragraph is kind of complicated---said another way---my quick ref graph has only one input (front seat pax wt). The output is ballast wt---and considers the range of rear seat and fuel wt.

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