some Varieze questions - looking for info and suggestions

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Offline thenrie

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some Varieze questions - looking for info and suggestions
« on: February 01, 2010, 11:56:02 AM »
I am going to purchase my dad's Varieze project from him (price is just right).  It's a legit VE, 70% finished, 90% to go.  However, my thoughts seem to be a little different than his on some things.  While he was intending to make it a full IFR traveling aircraft, I am thinking more along the lines of light and fast.  I think that's what the VE was designed for.

The tub, wings, and canard are made, gear is mounted, all parts are there.  A Subaru E81 will power it.  It has wing cuffs and the VE winglet.  Other than Dad adding a landing light in the nose and the Subaru engine, I believe it is built to the plans.  It appears to be well-built with good craftsmanship (my dad bought it years ago in almost the same state it is in now).  I would appreciate some discussion/suggestions regarding the following topics.

-  I have read the wing cuffs work, but cost some knots.  There seems to be some disagreement regarding vortilons vs. trailing edge fences for reducing the approach/climb-out speed.  Should I remove the cuffs and add vortilons or fences?
-  Some have suggested the VE winglets are only useful for protecting the main wingtip in case of a tip-touch.  Others suggest the LE winglet on the VE improves flight characteristics of the wing in much the same way as TE fences.  Do I need winglets at all?
-  The original design of the VE had anhedral in the main wing due to the lack of control surfaces, relying on elevons in the canard for     control. There were some accidents during landing when a tip dropped and the pilot instinctively tried to correct using aileron rather than rudder (as per Rutan's instructions), thereby causing the canard to stall and nose-in.  Rutan then modified the design to include ailerons on the main wing and apparently went away from the VW engine.  That is when the weight started increasing.  The original plan had the empty weight at 320 lbs and used a 65hp VW conversion (per a 1976 Popular Mechanics article).  It seems empty weight to the plans is now about 1050 lbs.  Where did all the extra weight come from and where can weight safely be cut?
-  What is the max safe speed, built to the plans.  What can be done to increase it?
-  I have read the VE is now rated for +/-2.5 G.  How can that be increased?

To sum things up, I want to build the VE to be a light, fast, get-from-point-A-to-point-B-on-very-little-gas flying machine.  As I start my planning, I would ask for suggestions on what others have found to work and what to stay away from, what to keep and what to lose.  I am a member of EAA and will soon be a member of CSA.  I don't yet have dad's plans/newsletters in hand, and won't for a number of months.  I'm just excited and trying to look ahead.
Tony
"'Tweren't my ignorance dun me in, but what I knowed that wasn't so."
from Uncle Tom's Cabin

Offline go ez

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Re: some Varieze questions - looking for info and suggestions
« Reply #1 on: February 01, 2010, 03:36:49 PM »
Take off the wing cuffs and add the vortilons - they are mandatory and very effective. I have trailing edge wing fences too - they lower approach speed & give better viz on approach.
I removed the lower skegs as a safety feature since it makes the risk of a wing digging in during a forced landing less likely  - they do very little aerodynamically - unlike the Long ez where the lower winglet is necessary
Empty weight with an O-200 engine is between 600 (light) to 700 + (heavy). Rutan's N4EZ VE bare equipped with elevons weighed 525 (declared)with O-200 , while the addition of the ailerons, landing brake etc etc bought it to nearer 585
the 1050lbs  is the gross weight
VNE  max speed is 190 kts but a good cruise is 140 -150 kts
+2.5 G / -1.5 G  restriction is due to the risk that the spar to wing fittings transition may be faulty and is difficult to inspect on a completed a/c. If the wing fittings are exposed and you or an expert can see & be sure it is done right the G limit may be less of an issue. If you are that stage, I'd think about removing the wing fittings and alodineing them to avoid future corrosion problems - big job though.
I'd fit bigger tanks - I used  PVC foam instead of urethane & mine hold 34 US gallons total plus 3 US Gall fuselage tank/reserve - excellent range
Plans & CSA will be a real education
Good luck - a great airplane

Offline dorr

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Re: some Varieze questions - looking for info and suggestions
« Reply #2 on: February 14, 2010, 10:27:32 PM »
I'm not in a Varieze - a few comments to add to this full response.

Larger tanks are good idea.

Al Fink also widened the interior from arm rest to upper longeron about 4" per side and the plane became wonderfully roomy - as Tackabury's Vari/Long is.

Burt designed the Long EZ because people were overloading the panel of the Varieze - keep the weight down - it is more critical in the Varieze - although I've seen them up over 800 lbs empty and flying fine way over book limits.

The Long EZ lower winglets are not necessary - despite Nat Puffer's tests of Cozy with longer and shorter canards and lower winglets.  We've got a fleet of them flying without - and they are just slightly mushier.

Klaus has proven to me how wonderful the trailing edge fences are on the Varieze - I hear he's advocating them for the Long EZ too, but didn't initially - due to less wing sweep.  Everyone who has the Varieze fences are very excited at the difference. 

Send me an e-mail and I'll get you the nearest good Varieze advisors.  The one thing we learned with a 100 member builders club in Los Angeles was not to be a loner.

Beagle
David A.C.Orr
"Beagle"
www.canardfinder.com

Offline flyoz

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Re: some Varieze questions - looking for info and suggestions
« Reply #3 on: May 28, 2010, 01:47:53 AM »
I have a set of Varieze plans and am considering building this as my second project ( built and flew Jabiru for 8 years )
I understand it would be easier to build a Long ez but the Varieze is closer to an almost single place aircraft and its what i would like to build
I have read quite a bit including some of the CP newsletters
I would like to build fairly close to standard  . But i have many questions and hope you will give me some of your accumulated wisdom
One of the things i dont like about the design is the wing spar attach system . The long ez is a much better more robust system IMHO
I am in the process of turning the original drawings into CAD . Without changing the geometry significantly it would be possible to attach the wing to the spar like the long ez
It would mean that i would have to move the root of the wing ( along BL 32 line ) 4.35 Inches ( 110.67 mm ) back ( chord remains standard just moves back )
The section remains standard the tip position remains standard ( no anhederal though ) The wing area remains the same
It means the wing leading edge sweep angle will change from 26 to 24 deg ( fairly small )
It will change the C of G point but maybe the engine can be moved forward to compensate .
Any ideas appreciated
Flyoz

Offline go ez

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Re: some Varieze questions - looking for info and suggestions
« Reply #4 on: May 28, 2010, 03:51:49 AM »
I think what you are suggesting is very ambitious. The existing full CoG range is only 6" so moving the main wing aft 4" is 'changing the geometry significantly'.

Altering the wing position relative to the canard, fuselage & engine would need very significant aerodynamic design thought & testing. These are very safe aircraft and it would be a shame to risk losing that attribute.

Remember, even Mr Rutan, with his vast design expertise, computer design/simulation capability, financial resources & canard experience found he needed to modify (ie add area) SpaceShipOne' rear wing surfaces  to avoid unanticipated & undesired stalling characheristics that were only discovered during Mike Melville's test flights.

Structurally the box type Vari Eze main spar and wing spar & full width spar caps are very different to the Long Ez C shape main spar and  wing spar. It is certainly possible to incorporate the Long Ez spar design & overlap attach methodology. I've had some thoughts on this myself to eliminate the wing fittings and perhaps additionally extending the wing spar to full span as per the Long Ez design to enable fewer layups/ better use of UNI glass in the wings thus reducing aft weight.

Personally, I'd try to accommodate this within the existing aerodynamic platform.

Regards
Steve
« Last Edit: May 28, 2010, 04:00:28 AM by go ez »

Offline flyoz

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Re: some Varieze questions - looking for info and suggestions
« Reply #5 on: May 28, 2010, 05:27:46 AM »
Thanks Steve
I have had a careful look at the long Ez wing . Its only when you start to redraw in CAD that you can appreciate
how Burt Rutan could do this in his garage without a computer . Amazing stuff . And its very accurate .
Just to clarify what i had in mind.....
Only the root portion of the wing would move back 4+inches at the BL 32 line nothing else the wing area could remain the same
The main spar remains in exactly the same position although the tip is moved back about .75 inch ( 19mm )
The C section Long Ez spar looks lighter than the box section of the Varieze and does not have as much weight in the wing root fittings
Those wing root fittings mean the glass attached to them had to be much heavier to handle the loads at that point 
It would be interesting to calculate just how much weight goes backward if you take all that into account - i have not done that yet 
But i suspect its very little . My concern is the aerodynamics . The long Ez wing changed significantly , moving back and getting bigger so
the design can absorb some change .
My question is if the Cof G range could be made the same as original do you think moving the root back slightly would
have implications on the aerodynamics ?
Flyoz

Offline go ez

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Re: some Varieze questions - looking for info and suggestions
« Reply #6 on: May 28, 2010, 06:27:15 AM »
I understand what you are saying (ie reducing the sweep) but the main wing centre of pressure will move back and possibly spanwise. The size/mass of the glass pads in the wing fittings etc are necessary to transfer the flight loads in the spar cap to/from the 1/4" bolts in the wing fitting and this mass  will be immaterial  compared to the overal mass of the a/c.

My point is indeed that the aerodynamics are the prime issue ie matching the revised centres of pressure of the two wings with the revised CoG of the a/c at all angles of attack.

You'd also need to check the CoL & CoG in relation to the position of the main gear attch & wheels so the a/c sits stabley on the ground & rotates at a reasonable speed.

Am certain the design can absorb change - main question is - will the change be nett beneficial?

Offline flyoz

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Re: some Varieze questions - looking for info and suggestions
« Reply #7 on: May 28, 2010, 02:51:02 PM »
I think you are correct
I know too little about the effects of moving the wing back . The collective information of canard aircraft of this type is essentially
understood by very few . Not a lot of written data - and the existing data is very questionable .
I guess i must try to find a way of mechanically attaching the wing like the long Ez and retain exactly the existing aerodynamics
Not because they are absolute but simply that i am unsure( at this point )  what changes would bring .
Anyway its an interesting topic .
Some things have been done and tested ( thats the beauty of the collective information  of the net )
The wing does not need anhedral
The main wing and canard can be set to the same incidence as the Long Ez
The strakes can be enlarged slightly without negative effect .

Offline Tom

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Re: some Varieze questions - looking for info and suggestions
« Reply #8 on: May 29, 2010, 09:34:06 AM »
I wouldnt worry about the wing attachments,

The current VE wing fittings are fine,  the problem spawned out of a couple of old clunker aircraft
that had lived outside near the ocean for many years.

Burt also imposed the 2.4 G limit to deal with the dry layup on the spar on the aircraft with the corroded wing fittings....
completely unrelated.


Almost every weekend, I pull 5gs in my VE and NEVER once, NOT ONCE, have I ever been worried about the wings failing...  The factor of safety in the Rutan designs are HUGE!-- much higher than in most certified aircraft....

Bottom line is built it as per plans, and you wont be dissapointed... 

PS scrap the subaru.. that motor belongs on the road, not the air,,  we dont need another statistic.

Offline flyoz

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Re: some Varieze questions - looking for info and suggestions
« Reply #9 on: May 30, 2010, 04:17:37 PM »
Thanks for the reassurance
I am sure built correctly most of the Varieze's flying are as robust as yours
I have seen some destructive testing of a Varieze and one other issue is twisting
When the wing is loaded up starts to twists at the Strake wing joint
It makes sense if you see just what that joint has to take and the load paths to it
All i was looking at is the possibility of joining it like a Long Ez which from an engineering point
of view is a  much much less stressed joint with better loadpaths
The Varieze wing in that test failed at 7 Gs and the canard at 8
Actually at the inbord central spar section of the wing spar joint
If you want i can post that test ( PDF )again
Flyoz

Offline Tom

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Re: some Varieze questions - looking for info and suggestions
« Reply #10 on: May 30, 2010, 09:07:56 PM »
Sure post it again,

the 7g failure of the wing seems a bit wonky..

As per the plans, the limit load is 5gs... which is VERY conservative....

Offline flyoz

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Re: some Varieze questions - looking for info and suggestions
« Reply #11 on: May 30, 2010, 09:56:58 PM »
RAF Varieze structural test ( PDF file )  is 600 KB but Max allowed is 300 KB for attachment
Any way around that ?
Flyoz

Offline go ez

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Offline flyoz

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Re: some Varieze questions - looking for info and suggestions
« Reply #13 on: May 31, 2010, 02:48:16 PM »
Thanks
Thats the one ... 
Interesting to note the 3.5G rating , based on this test
Thats partially my reason for finding another way of fixing the wing
Also the long ez system is easier to build with more repeatable results
I am sure most Varieze aircraft were built well so my attempt to find another way
is simply to my own personal decision
Another issue that came from this test is the wing twist issue
The original spar /wing joint is only 3.5 inches ( 89 mm ) from bolt center to bolt center
If you take the lever from the center of the spar to the center of the tip roughly 48 inches ( 1213mm )
Putting a pin at the leading edge of the root into the strake would help in keeping this area from twisting
In hindsight it easier to look back at the design and make smaller changes but i never lose sight of the elegance of the original design
Flyoz

Offline go ez

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Re: some Varieze questions - looking for info and suggestions
« Reply #14 on: June 01, 2010, 01:08:06 AM »
I think Germany or perhaps Switzerland required that a structural anti twist pin be installed near the leading edge at the strake /wing interface - might have just been the Cozys or MkIV though.

I think I recall that Nat Puffer & Rutan both said it was unnecessary - which I guess with the reduced sweep compared to the VE is logical.

With the VE wing sweep, if you used the LEz type wing spar arrangement which is a C section rather than a torsionally stronger VE type box section then perhaps a leading edge pin might be prudent. It depends too on how much the wing and strake skins contribute to the overall stiffness.

The pin might need finally installing after the a/c has been flight tested so the ability to adjust the LEz wing incidence to compensate for small builder alighnment errors etc is not lost.

Regards
Steve