Works just as good for models in the 62 - 64 Oz range.
Think about this : If a HEAVY model becomes a good performer, imagine what a light model becomes. More on that later.. I dont want people to think this is just a fix for heavy ships.. That is ONE aspect to what they can do.. I prefer to think of it as giving a top line well trimmed model more consistency. This is something Paul Walker goes on and on about. CONSISTENCY. From day to day, trim to trim, site to site - and control input to control input. This is how you get precise.
Its about controlling the airflow, obviously for a heavier model it will make it perform better because you are controlling the airflow and giving the wing " more grip "
I experiemented with them in various locations, amounts - as many as 10 pairs top and bottom, I found that you can reduce it down to only 1 pair - just outside of the prop wash and this is just as effective as having multiple pairs. It came about from consistent flying and having them knocked off - I noticed performance didnt waver - so each subsequent incarnation was reduced. I had one test ship where I went down to only 1 single generator on each wing but found that wasnt really doing anything.
I experiemtned with various sizes, shapes, lengths over a span of 15 years. I even consulted with a company who makes them to spec for full sized aircraft - to keep it in scale from what the full size guys are doing, we would need to make our VG's 2mm long by .5mm high.. This is simply a sliver of carbon.. The size I have designed work well, are easy enough to be applied with tweezers and a steady hand, and are still small enough to be fairly unobtrusive. Go smaller if you feel you can apply them - I have gone as small as 1/2 size you see on my current design - but were a pain to install, people tend not to see them, and they were no more effective.
I think the key is the pidgeon toed approach, having the airflow swirl in opposite directions. Looking at your photo's they are spot on with my previous "how to" Article.
I've also submitted the article to Stunt news and should appear in the coming months.
There is little emperical doubt as to their effectivness for heavier models turning them into solid performers. I dont have much problem with building 62 - 65 oz ships with big modern engines - I still apply them.
As Doug Moon found out on his test Stunt ship - what it does for a top line stunt ship is improve your consistency, each courner is more dependable, more reliable and more accurate. Your not ever worried about having the airflow wash off and bottom out if you bang it harder - or you can leave the turn later and deeper.
When your at the top of an hourglass you still have amazing tail control even with a wind shift. This is where I think they come into their own, on a lighter aircraft that's well trimmed.
I also find models response more linarly to trimming - and are more stable from site to site. Air denisty changes seem to effect it less and less. You still have the issues of getting trim correct but the changes seem minimal.
They are fairly easy to make - I have been playing around with the idea of offering Vortex Generator Kits for sale made out of .0014 Rigit Carbon Fiber, which is what I currently use. These would be made to my specifications for Control line aerobatics and would be supplied in a kit of 10. ( 8 for the model and 2 spares ) With a short how to instruction sheet.
If there is sufficent interest I will offer them for sale - I have helped out a couple of people so far - Just email me if your interested.
I dont bother with recessing them in - with a drop of CA on the top of the Carbon generator they are solid enough to stick. In the past when i've retired planes I've tried to remove them - which isnt easy, you tend to remove copious paint in the process.
I dont put them on during painting or clear becasue its impossible to buff out with them in the way.
About speed control : This is tricky... I dont actually feel they control the speed persay.. If your engine is going to speed up thats controling the overall speed of the ship. They simple control airflow. Now - this is where is might get confusing.. When you pull out of a hard corner, there is still sufficent airflow being generated by the VG's - lots of airflow engery that doesnt dissipate, so the model wont drop out of the sky, and the engine isnt under any strain to make it fly straight. This does translate into a more controlled airspeed.. But its not going to slow you down if your engine isnt set up correctly.
Think of it this way : When you see a bird flying into the wind - stationary but airborn, its a result of sufficent airflow flowing over the birds lifting surface.
With the Vortex Generators, they force the airflow to conform to a swirling Vortex that intrinsically has more energy so takes longer to dissipate. You could have no forward momentum and still be airborn for a moment. This is when you hit a dead air pocket, or you have a sudden rush of wind coming from the reverse direction.
Look at what happened to Doug Moon at the nats - his crash was a direct result of hitting a turbulent "dead" pocket of air, and although had forward thrust - had insufficent lift to remain airborn.
We have all experienced, landing downwind, having the model simply " fall out " of the sky. The Generators prevent many of these issues from occuring.
At the pointy end of competition I find they improve my consistency from flight to flight, and manouver to manouver - I never second guess my control input or wind conditions.
Great to hear you had success with them - Well done. 
Still waiting for the New Riff Raff to have them installed............ doug..........
Topic: PJ's vortex fins (Read 22321 times)