Original design cuffs vs vortilons n fences

[Bugstrider]

Good evening,

I am looking at a VariEze that has the original cuffs on the leading edges.  I am having a challenging time finding data on the reasons for the leading edge change and the implementation of the more traditional leading edge vortilons and trailing edge fences.  Any pointers on better search technics welcome.  Obviously I am doing something incorrectly in my search criteria.

How many Vari drivers out there still run with cuffs and what has  been  your experiences?

cheers

Edited February 15, 2021 by Bugstrider

[slk23]

If my memory is correct the change to the cuff-less wing was documented in the Canard Pusher newsletters. Marc Zeitlin may be able to advise you on the effort and cost to convert to cuff-less. 

Edited February 15, 2021 by slk23

[Marc Zeitlin]

47 minutes ago, slk23 said:

If my memory is correct the change to the cuff-less wing was documented in the Canard Pusher newsletters. Marc Zeitlin may be able to advise you on the effort and cost to convert to cuff-less. 

Stephen is correct here - CP-42, pages 5 and 6 have the information on using Vortilons on the leading edge instead of cuffs. They seem to indicate that the Vortilons hold some reasonable advantage over cuffs, but obviously the cuffs work well too.

It's interesting that they indicate that there wasn't good data for installing Vortilons on the Long-EZ, but obviously at some later point, they changed their minds.

[Bugstrider]

Thanks guys for your reply's.  Thanks Marc on the heads up on the CP newsletters.  I found the one you mentioned after a bit of searching, now that I know where they are located, I look forward to educating myself.

Are rear trailing fences not recommended if the original leading edge cuffs are left in tact for now?  It is interesting how initially they did not recommend the vortilons for the LE but reversed that thought process as you mentioned Marc.  I honestly do not recall seeing a flying canard, other than some VEs that do not have them.

With the advent of 3D printing, I wonder what or if there is a possible market.  Although I do not have a printer or experience with creating a product.  Just thinking outloud.

 

cheers

Edited February 16, 2021 by Bugstrider

[Bugstrider]

I also ran a cross this product, but it is listed for the LE and no mention of the VE platform.  I also wonder by installing the VG's, would or could it affect the stall characteristic of the main rear wing since you are changing the stall speeds of the canard.

Again, I am just passing on things I have seen and now have questions about. I am still learning and hope that someday I will have a large enough knowledge base to have an intelligent question with the canard experts.😉

 

Edited February 16, 2021 by Bugstrider

[Marc Zeitlin]

1 hour ago, Bugstrider said:

Are rear trailing fences not recommended if the original leading edge cuffs are left in tact for now?

That's an interesting question. So few VE's have the cuffs at this point, and so few have the fences that there's no overlap between the two groups, to my knowledge. There's no reason the fences, which are installed both for aileron effectiveness at low speeds as well as some deep stall resistance margin, shouldn't work with the cuffs as they do with the vortilons.

1 hour ago, Bugstrider said:

I also ran a cross this product, but it is listed for the LE and no mention of the VE platform.  I also wonder by installing the VG's, would or could it affect the stall characteristic of the main rear wing since you are changing the stall speeds of the canard.

There are two versions of VG's for canard aircraft. The first (not mentioned in that ad for extremely expensive VG's that you can make yourself for $10) are :

GU Canard trim change in rain eliminators

These are installed on the canard ONLY, and far enough forward that they do NOT affect the maximum Cl that the GU canard can produce - they ONLY eliminate the change in pitch trim with contamination (rain, bugs, whatever else gets on the airfoil).

The next version is the ones mentioned, that are installed on a different chord point on the canard, as well as on the main wing. These are installed to lower stall speed, and hence approach and landing speeds. On Long-EZ's, they were developed by Jim Price for his altitude record flights (he gained over 2K ft. of altitude due to the lower speed he could fly at with the VG's).

You NEVER put the second version of the VG's on the canard alone, because then a deep stall is likely. And you don't put them on the main wing alone, because it won't accomplish anything. If one installs the second version of the VG's, expect to lose a couple of knots on the top end in exchange for the lower stall speed on the bottom end.

[Bugstrider]

Thank you Marc,

 

That was very helpful in understanding the differences of the VG's.  I have seen them on only a few Long-EZ's in photos and video but I am unsure which ones they are.  Without being able to talk to the owners of those planes, I will assume that the first set of VG's you mentioned since these planes are used for pleasure flying and not the second, but then again it is a S.W.A.G. on my part.

Here on field, I have two good friends with Long-EZ's who fly with two different canard designs.  Neither have VG's and both have totally different attitudes about flying into rain due to the reduction in lift or negligible reduction.  To be honest, it makes my head spin when their respective perspectives differ.  

[bmckinney10]

I have the cuffs on my VariEze that I started flying in November.  I have 25 hours in so far and have no issues.  I have never flown one with vortilons, so I have no comparison.  Someone posted to me early last year that the cuffs may produce dutch rolls if too slow on touchdown.  I have not experienced this condition, but I may touchdown a bit faster at this point as I am still in the learning phase with my VariEze.  I always thought they switched to the vortilons because they were easier to install and provided the similar effect as the cuffs, but there is more to it as we have read.  Some have indicated you may pick up a few knots with the vortilons over cuffs.  Right now the VariEze is fast enough for me.  I came from flying  Cherokee 140.