Higher level of cg understanding

[Aclouston]

Been trying to firmulate this into an intelligible question for days. Failed so far. 

People here are smart enough, just write down in point form, the question will emerge by itself.

- LEZ Nose lenght/volume is fonction of batterie size, electric nose lift, presence of starter, alternator, glass pannel support equipment and oil heating at the front.

- Light vfr pilot like me (160#), flying mostly solo, need to be carefull of forward cg with either 235 or 320 engines. Unless no starter/alternator, so a closer basic L ez

-big negative of starters/alternators besides cg affect, is weight of cables adding to total a/c weight.

- very small alternator (B&C) vac pad mounted is doable ( 320&235?) but is it desirable? Hand proping is not the end of the world if the engine is tuned.

Your are never really stuck with cg forward a/c. I.e. Longer prop extension and others rearward mass transfer that do not contribute to total mass increase and moves ch aft ( even gas tank size could  theorically be reduced at forward end ) if one is building strake while beeing concerned, especially if the engi e is still unkown. I want a 235 but might end up with the 320 if...

-Surprizingly, I don't dislike the vintage stubby short nose. However it does or may have consequences!

I think I can stop here and let people bring in their thougths. I DON'T have clear question yet! The brain is trying to process....

 

[Marc Zeitlin]

7 hours ago, Aclouston said:

- LEZ Nose lenght/volume is fonction of batterie size, electric nose lift, presence of starter, alternator, glass pannel support equipment and oil heating at the front.

One increases the length of the nose for two reasons - first, aesthetics (which is obviously NOT a functional reason) and secondly, to provide space to move the battery further forward if one has an O-320 and the empty CG is too far aft. There is no other reason.

7 hours ago, Aclouston said:

- Light vfr pilot like me (160#), flying mostly solo, need to be carefull of forward cg with either 235 or 320 engines. Unless no starter/alternator, so a closer basic L ez

You have this backwards. The empty CG of the plane is generally between 109" and 112". ANY weight in the front seat moves the loaded CG forward, but a lighter pilot moves it forward less than a heavier pilot. A 160 lb. pilot in a Long-EZ will NEVER have a forward CG issue and will never get anywhere near the forward CG limit. With an O-235, you MAY need some additional nose weight to stay forward of the 103" aft CG limit, and with an O-320 you will almost certainly need a lead-acid battery in the nose in order to stay forward of 103".

7 hours ago, Aclouston said:

- very small alternator (B&C) vac pad mounted is doable ( 320&235?) but is it desirable? Hand proping is not the end of the world if the engine is tuned.

While you may not be averse to hand propping (which is a function of battery capacity, not alternator size), unless you're building an airplane that will only ever be day VFR, even a 20A pad alternator is marginal at best. I have the B&C 462-H pad mounted alternator, and that is 35A - 60A. It's OK for a primary alternator (it's my second alternator), but will only put out current when above 1100 RPM. If one is going to install a single alternator, there's no downside to a 40A or 60A belt driven alternator. Weight's about the same as the 462.

When you ask these types of questions, the first thing to think about is: "What problem am I trying to solve"?

[Kent Ashton]

My EZ had a long nose, O-320, battery in the nose, electric start.    Attached is the W&B that you can compare.  I used 16# of ballast for weighing purposes for an empty weight and CG of 993# at 110.51" (ballast removed for the calculation).  For flight testing I was 225# myself and I used the 16# of ballast which gave me a wt/CG of 1234# (less fuel) and 99.79" which gave me good stall warning indications, however I generally flew the airplane without the extra ballast which gave an empty wt of 1218# (less fuel) and a moment of 123011 which gave me a CG of 100.99" which is within the 101.5" aft limit.  Fuel doesn't change that very much.

There will be other difference with yours but I would say a 160# pilot with an O-320 will certainly need a battery in the nose and might need some extra ballast too, but it wouldn't be huge.   I wouldn't rely only on a spreadsheet.  Talk to other pilots of various weights and engine combos and see how they are configured.

I wouldn't build an EZ without a starter.  I hand-propped an O-320 Cozy III (same as an EZ) for a while after I removed a heavy certified starter but finally went back to electric start using a lighter starter.  It is just too much hassle to hand-prop, IMO.
 

N16AVWtz&Bal.pdf

[Marc Zeitlin]

2 hours ago, Kent Ashton said:

... which gave me a CG of 100.99" which is within the 101.5" aft limit...

Not so minor nit - the aft CG limit for Long-EZs is 103", NOT 101.5". For COZY MKIVs and IIIs, it's 102".

[Kent Ashton]

3 hours ago, Marc Zeitlin said:

Not so minor nit - the aft CG limit for Long-EZs is 103", NOT 101.5". For COZY MKIVs and IIIs, it's 102".

Hmm, now that you mention it, I am checking the Long-ez POH and it seems to show a 104" aft CG limit.  I suppose I was using 101.5" as a first flight aft limit.  Pic from the POH.

[Marc Zeitlin]

49 minutes ago, Kent Ashton said:

Hmm, now that you mention it, I am checking the Long-ez POH and it seems to show a 104" aft CG limit.

The 104" aft limit was superseded in the CP #37 Page 4 - changed to 103".  LPC #116 - change 104" to 103" on page 30 of the POH.

It was a mandatory change. I'm always amazed and surprised by how many LE builders/pilots/flyers are unaware of this...

Edited July 22 by Marc Zeitlin

[Aclouston]

22 hours ago, Kent Ashton said:

"My EZ had a long nose, O-320, battery in the nose, electric start."

"There will be other difference with yours but I would say a 160# pilot with an O-320 will certainly need a battery in the nose and might need some extra ballast too, but it wouldn't be much."

Thank you so much for the replies.

Does this implies that for the little extra effort required and mourning of the pretty (but yes awkward) short nose, one should definitely opt for an extension especially if the engine size and configuration is not yet known? I only saw 15" as a real number for the extension lenght. Is there a standard? Plans?

Regards

Allan

 

[Marc Zeitlin]

31 minutes ago, Aclouston said:

Does this implies that for the little extra effort required and mourning of the pretty (but yes awkward) short nose, one should definitely opt for an extension especially if the engine size and configuration is not yet known? I only saw 15" as a real number for the extension lenght. Is there a standard? Plans?

Due to the fact that the longer one makes the nose, the lower the pitch and yaw stability of the airplane, one should only lengthen the nose by the absolute minimum amount required to fit the battery needed for W&B reasons. 15" is a substantial increase, although I've seen up to 30". A 30" extension definitely negatively affects the Dutch Roll and slipping capability of the plane - I've flown extended nose aircraft, and the differences can be noticeable. I'd suggest 8" - 12", with 15" as an absolute maximum, if any

The longer nose also affects the position of the nose bumper, and increases the potential for fuselage side damage in the event of a nose gear up landing, due to the longer moment arm for impact forces.

Do make the nose door large so that you can get both hands inside to work at the same time, and for Cthulhu's sake, make the fuselage top removable like the COZY MKIV for maintenance and accessibility.

[Kent Ashton]

If you check the EZs pictured here, you will see some pretty long noses.

https://www.google.com/search?q=site%3Acanardzone.com+kent's+long-ez&udm=2&fbs=AEQNm0A2upiO_GHeTz6R89sNEjTHXSUfB8x3gweQ77S5CBNH1tzEOsaivoIUdA-AqC0ULxqEU6_JAVAk23cd09fLsdbCmU2G8PVUI1YBAgKBNZdMVmr4-uRs6WXLhwmwezwY4gBPL9TtFQ_qwfCzqT60ExcLdUNt81pv1CwPEf391fK-9sQJLsENr8hu6rxJsTWx0vu_FC4YY5X5H1gGGU3bIcXFdBaxUw

I never flew a regular-nose EZ but I didn't notice anything objectionable with the nose I built.  I can't say how long it was but here is how I started it (pic 2).  Marc makes a good point about the nose gear pivot point.  Doing it again, I would draw the nose shape I wanted and redraw the NG30s to move the pivot point a bit down and forward.  I started a CAD drawing (pic 3) but never got it finished.  Here, the pivot point is moved to FS 2.146, WL 5.5.   That allowed for a symmetrical nose in profile. FS 0.0 is also on the drawing.  I was also trying to build-in more space for the noselift mechanism.   I was barely able to fit an 18AH AGM battery in the nose.  The access covers could have been made bigger.   Yeah, building is fun.

Edited July 23 by Kent Ashton

[Marc Zeitlin]

1 hour ago, Kent Ashton said:

If you check the EZs pictured here, you will see some pretty long noses.

Yep. Many of them WAY too long.

1 hour ago, Kent Ashton said:

I never flew a regular-nose EZ but I didn't notice anything objectionable with the nose I built.  I can't say how long it was but here is how I started it (pic 2).

Having worked on your plane for the current owner, I'd say that your nose is ~12" longer than stock, give or take. And I would not expect that increase to be particularly noticeable in the stability regime. But some of the much longer ones, such as on N506DB, or the now destroyed Lance Hooley highly modified jet Long-EZ, are just ridiculous, and do substantially affect handling qualities, as measured on the Cooper-Harper scale.