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Hangar Flying => Hangar Flying => Topic started by: flyboy on August 30, 2009, 06:58:00 PM
Title: what's the deal with varieze wing cuffs?
Post by: flyboy on August 30, 2009, 06:58:00 PM
I see some Varieze's with wing cuffs, but notice that most do not have them. The POH puts aft CG limitations with planes that do not have them. Since most folks don't seem to have wing cuffs, is it not a big deal?
Title: Re: what's the deal with varieze wing cuffs?
Post by: A. Bruce Hughes on August 31, 2009, 07:35:08 AM
There is a narrow Cg range for ANY airplane, including certificated ones.
I know very little about variezes so will not comment.
Bruce Hughes :)
Title: Re: what's the deal with varieze wing cuffs?
Post by: Bill James on August 31, 2009, 08:58:34 AM
The way I remember, cuffs were a temporary fix to address low speed stability. Retaining the cuffs is an owner's prerogative. One person at the Kerrville flyin years ago said he kept them to keep from disturbing the paint. Functionally, from the shade tree mechanic/aerodynamicist's position, it seems to me that the cuffs simply provided the effect of two vortelons at their ends. But technically, per the CPs, vortelons are required. When my plane was painted a couple of years ago I flew it once on a 6000 ft runway without the vortelons, observing their significant benefit. Both the vortelons and TE Fences are of benefit in my current flying, shortening the ground roll for takeoff and landing.
Per the comment, “The POH puts aft CG limitations with planes that do not have them”. It is very comforting that comments from the POH and CPs would appear here for clarification. I commend and applaud you for doing your homework. This is a positive indication in an area where many have concerns about adequate Eze knowledge. I would offer that the phrase is an incomplete reading, which benefits from being brought up in this particular thread. My response, obviously all VariEzes have an aft CG limit. To continue, the vortelons should be installed. I don't see them making a difference to the way we determine CG. The plane is set up for first flight per the plans, CPs and POH. During the restricted period, actual flight will indicate the preferred CG within the CG range. This would also be prudent (required) after purchasing an Eze. After the proper CG determination, nose wheel liftoff speed provides an indication on each flight that the CG is correct. Minimum speed tests at altitude provide for setting the approach speed. It has been stated, I believe correctly, that Ezes need a 22 mph buffer over minimum speed for adequate energy to reduce rate of descent. I don’t use the term stall speed because at full aft stick my plane just sits at a very high angle. I’ll just let that irritating stall rabbit chase end there.
At my first Jackpot, after the race one of the other racers noticed that I had two quarts of oil stored in the nose. He was astounded that I would leave them there during the race. That is what I think of when being told that an aft CG reduces wt on the canard, allowing a faster speed. That aft CG attraction must be balanced with the other operational concerns, and not carried to an extreme.
The details are in the CPs. Many current flyers benefitted from growing up through the VariEze birthing pains, reading the CPs multiple times and understanding the growth process. Actually it wasn’t any easier to be knowledgeable then than it is today. Congrats on doing it right.
Title: Re: what's the deal with varieze wing cuffs?
Post by: Bill James on August 31, 2009, 10:19:07 AM
Just for fun, some CG comments heard years ago from other Eze drivers that I believe are accurate- A forward CG will result in a longer takeoff ground run to get the nose of the ground. In flight at min speed with full aft stick and minimum speed (canard at max lift) the nose won’t raise as high. In flight an aft CG with full aft stick and minimum speed (canard at max lift) the nose will lift higher making a nod more likely or pronounced than with a forward CG.
A extreme condition, after inadvertently flying a VariEze with the CG aft of the allowable range, the pilot said the stick was positioned well forward. When attempting to reduce speed for approach, around 110 mph, he described the plane as wanting to flip nose up, requiring him to repeatedly “punch” the stick forward every few seconds to keep the nose down. He was flying over a long runway and was able to land fast. Other comments please :)
Title: Re: what's the deal with varieze wing cuffs?
Post by: flyboy on August 31, 2009, 01:49:18 PM
Thanks Bill,
I'm considering purchase of a Varieze and the more I learn the more I realize there's alot I don't know. Complicating things is that no 2 EZES are alike. Thankfully I have some respected builders advising me that are a big help. I value your comments and experience with the VE.
So am I understanding your comment correctly? Are the vortilons a replacement to the cuffs or are they both advised? I'm figuring hypothetical CG's via the info from the POH, and without cuffs I'm in the danger zone.
Also, what's your opinion on a drop dead max. empty weight that's safe? I know what the POH says. ;) Thanks again!
Title: Re: what's the deal with varieze wing cuffs?
Post by: Bill James on August 31, 2009, 05:21:36 PM
Yes Vortelons are the required leading edge devices. As you say there are differences in planes but the initial CG box is appropriate for all first flights or second first flights :) Data gathered in the restricted period may result with Center of Gravity operating results per the CPs and POH. Or some aircraft may require nose ballast. Your advisors will be your best assets here. An interesting thing to follow in the early CPs, a VariEze was having low speed stability problems. Evidently on that plane the canard was raising the nose high enough for the plane to be unstable. The pilot flew the plane to Mojave and their answer was adding 12 lbs in the nose. Then the plane flew per the POH. Later, the CP announced the solution to cut 4 inches off the ends of the canard, which accomplished the same thing without adding the 12 lbs nose ballast. I read this account recently here on ez.org. As you know, the VariEze was designed for the 175 lb engine. So with everyone using the heavier 0-200, shortening the canard worked as a universal fix for that engine. But it can't be shortened again. It took me several brain cycles to understand this sequence. Normally with a heavier engine you would want more wing area. But with the eccentricities of the Eze design, this is what worked. The other interesting fix was making the elevator cord longer to make the pitch less sensitive, which also didn't make sense to me until after several brain cycles. I thought that would make it more sensitive, but in fact it made the stick harder to push, and thus less sensitive. These thoughts are from memory. Your use of the POH and CPs will provide the accurate details.
Title: Re: what's the deal with varieze wing cuffs?
Post by: cloudman on September 04, 2009, 05:58:50 PM
Regarding wing cuffs or vortilons........ I first flew my Varieze way back in 1981 with wing cuffs and later changed to vortilons. My CG was never an issue since I had a C-85 with starter but carried a fairly heavey 28 amp hour battery in the nose. I have always been interested in a slow approach and landing speed and noticed with wing cuffs and trying to fly final below 80 mph my plane would rock side to side. With the vortilons this improved some along with a lower angle that improved visability over the nose. When trying to touch down at the lowest possible speed (about 68 mph) I would have to look out the side since I could not see over the nose. The vortilons helped this some. I also added trailing edge wing fences later on, but it was after installing LongEz style lower winglets. The lower winglets provided more lift at the rear most part of the wing and really improved my forward visability. So when the trailing edge fences were added, they did not seem to make any real difference. I originally built them fairly large and have cut them down in size three times. They were giving me too much of the weather-vane effect when taking off in a cross wind. I wish that I would have installed the fences before the lower winglets to see what the effect was, but I feel that the LongEz lower winglets were the best modification of the bunch. I can fly final at 75 mph, but usually at 80 or higher, but I like knowing that if I have to make an emergency landing, I will be able to land at a low speed (for a Varieze) and with the lowest KE for my weight. Cloudman.....WT Johnson
Title: Re: what's the deal with varieze wing cuffs?
Post by: Bill James on September 04, 2009, 07:13:24 PM
Great info. Can you please describe your lower winglets. Are they thin or thick? Do they pretty much match the winglet outline at the wing tip? How would you change them, or what do you think in particular works well, particularly under the rudder area. Thanks
Title: Re: what's the deal with varieze wing cuffs?
Post by: cloudman on September 06, 2009, 12:26:45 PM
Great info. Can you please describe your lower winglets. Are they thin or thick? Do they pretty much match the winglet outline at the wing tip? How would you change them, or what do you think in particular works well, particularly under the rudder area. Thanks
Lower winglets............I patterned mine pretty much along the LongEz design. They are about one inch at the thickest next to the lower surface of the wing. The thing to make sure is to check and make sure that there is plenty of clearance (at full deflection) between the non-modified rudder bottom and the added lower winglet. I saw a Varieze recently with them that stopped rudder travel at less than one inch max. I can measure, but think they are about five inches tall. Initially I used expandable foam to attach and fill any gaps and of course removed the original lower winglets. They have been bookends next to my desk at home for quite a while now. I used a couple of pieces of sheet steel with 90 degree bends. WJohnson
Title: Re: what's the deal with varieze wing cuffs?
Post by: A. Bruce Hughes on September 07, 2009, 12:24:59 PM
This was very informative and made sense until the last sentence. What do you mean about the sheet steel? I don't use steel anywhere that I can avoid it.
Bruce Hughes :)
Title: Re: what's the deal with varieze wing cuffs?
Post by: Bill James on September 07, 2009, 01:13:35 PM
I'm bettin Cloudman either stores lots of books between his winglets when he is not airborne, or he has bookends made of the original small lower winglets, with the 90 degree steel sheet stuck up in them as the base. Either way Cloudman, i would claim at least 5 knots :)
Title: Re: what's the deal with varieze wing cuffs?
Post by: cloudman on September 10, 2009, 06:28:48 PM
I'm bettin Cloudman either stores lots of books between his winglets when he is not airborne, or he has bookends made of the original small lower winglets, with the 90 degree steel sheet stuck up in them as the base. Either way Cloudman, i would claim at least 5 knots :)
Bill, Yes, I figure that anyone who is building an EZ type would figure that one out !! My bookends are going with me to the old folks home along with old issues of Sport Aviation and other mags. The bookends will not hold the mags very well, but will hold old VCR's, etc. Wayne..........cloudman