Hangar Flying => Hangar Flying => Topic started by: walter on December 17, 2005, 11:19:36 AM
Title: varieze cg and weight question
Post by: walter on December 17, 2005, 11:19:36 AM
What, if any, is the effect on CG during fuel burn in the Varieze? Also, I know the POH number on max operating weight but I was wondering if anyone consistently operates safely above those numbers? If so, what are the numbers you are using (i.e. weights, horsepower, environmental conditions)?
Title: Fuel consumption and CG
Post by: Gilbert DRIEUX on December 17, 2005, 04:09:01 PM
Due to fuel consumption, CG will move about one inch aft. (25.4 mm).
In my VariEze, full fuel CG is 2545 mm => 101.97" Fuseage fuel only CG is 2535 mm => 99.80" Dry (no fuel .....) CG is 2527 mm => 99.48"
Lyc O-235 C2C Short canard. Make your own calculation, as described in VariEze Owner's Manual Pages 26. Sample loadings There, you can change the fuel quantity, and see what is the result.
Regards.
Title: Re: Fuel consumption and CG
Post by: Graybird on December 18, 2005, 08:58:08 PM
Quote from: "Gilbert DRIEUX"
Due to fuel consumption, CG will move about one inch aft. (25.4 mm).
In my VariEze, full fuel CG is 2545 mm => 101.97" Fuseage fuel only CG is 2535 mm => 99.80" Dry (no fuel .....) CG is 2527 mm => 99.48"
Lyc O-235 C2C Short canard. Make your own calculation, as described in VariEze Owner's Manual Pages 26. Sample loadings There, you can change the fuel quantity, and see what is the result.
Regards.
Title: fuel consumption and c.g.
Post by: Graybird on December 18, 2005, 09:59:05 PM
Walter It appears that my last post didn't come through, so I'll try again. Gilbert is correct in the information that he posted on c.g. changes with fuel burn. Each aircraft may be a little different due to construction differences. He failed to answer your other question tho. First No one is saying in any way that you should EVER overload any aircraft above what has been declaired as it's maximum operating weight by it's designer. Mr Rutan is a very intelligent individual as we all know. A higher than regular m.o.w. can really open up subjects for discussion on this forum,BUT-I have knowledge of one veri that was operated at 1300lbs. at over 110 degrees for over 500 miles with no problems---keep in mind this can reduce the safety factor built into the design, add to runway takeoff length, stopping length, and the biggie-- an off airport emergency landing. Point is, you're rolling the dice if you do it. I'll bet we all know someone who's done it because of bad planning, or the fuel guy misunderstood the fuel load request, or the passenger fibbed about their weight etc.
Title: varieze cg and weight question
Post by: walter on December 18, 2005, 11:17:08 PM
Thanks for the response Graybird. I was just curious if anyone had squeezed any extra performance out of a vari and done it safely! Would it be safe to say that the MOW is limited by performance versus structural limitations? If anyone else is reading, I would appreciate any other input! You could do it anonymously even! I don't care just as long as I get some good feedback!
Title: veri c.g and fuel consumption
Post by: Graybird on December 19, 2005, 02:10:15 AM
Walter: I believe that the M.O.W is for the most part a structural design consideration. The designer will calculate or in some cases build a test pair of wings for example then test them by loading them with sandbags until they begin to fail. Knowing this figure the desiner will figure in a safety factor of say 25% just for a number to work with. The yield figure minus the 25% is what the m.o.w works out to be. This 25% is what helps to protect us when we inadvertantly fly into medium to heavy turbulence for instance, or accidently find ourselves getting close to the never exceed speed, or in a heavier weight condition than the M.O.W. calls for. By exceeding any perameter we reduce our safety factor by some percentage. To get a GREAT deal more performance out of a Verieze you would have to "beef up" the aircraft to take more stress and that adds weight-which requires more power that adds more weight etc. etc.etc. Hope this wasn't more information than you were looking for.
Title: Exceeding maximum gross weight for takeoff
Post by: Barney on December 19, 2005, 11:07:30 AM
Pertinent questions (any aircraft):
What might the consequences of exceeding maximum gross weight for takeoff (POH/Flight Manual) be; should the FAA discover such; should an accident result (with/without injuries to crew/pax/people on the ground); or no one finds out & nothing happens (this time!)?
Title: varieze cg and weight question
Post by: Waiter on December 19, 2005, 01:37:58 PM
Consider the following when operating overgross:
A) ability to accelerate to takeoff speed is diminished. Most EZ's are poor performers in this category to start with. Add a couple hundred pounds, and takeoff distances can easily double.
B) Stopping distance. i.e. aborted takeoff near flying speed could easily exceed the design limits of the brakes.
C) Survivability during off field landing. as the weight goes up, survivability goes down.
The lighter the plane, the better.
Waiter
Title: varieze cg and weight question
Post by: JB on December 20, 2005, 07:43:24 AM
Hey this sort of an add on to this thread. I was wondering about the cockpit size in the front on a Vari. I'm 6'4" 185 lbs with a tall sitting ht. I sat in a Long EZ and fit although not with a ton of space.
Title: varieze cg and weight question
Post by: Gilbert DRIEUX on December 20, 2005, 02:50:23 PM
I fly a VariEze. I'm 6'0" (1,83 m) and 230lb (108kg). Cockpit is about 3" above my head (in pilot seat). Not too big, for sure, but enough and confortable !
Title: varieze cg and weight question
Post by: JB on December 22, 2005, 04:11:21 PM
Thanks for the reply. I just trying to figure out all the differences between a Long and a Vari.