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Aileron Gap Seals printer friendly version
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Posted Tuesday, December 26, 2006 @ 09:00 PM  

The pictures of Bob G's modifications on the CFI-UK website show aileron gap seals which I assume are constructed like these: http://www.wingsandwheels.com/page28.htm Bob says it is appropriate to reduce Va (or at least the speed at which max aileron may be applied) but what is Va for an RF4D and by what amount should it be reduced if gap seals are installed? - Bob?

Steve

Bob Grimstead
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Posted Sunday, December 31, 2006 @ 10:53 PM  

Hello Steve, Folks,

Section 2.2 of the RF4D Flight Manual quotes manoeuvring speed (they call it Vp) as 124 mph/ 107 kt.
I use knots, so if you fly mph you'll have to convert by multiplying by 1.15.

I fitted this 3M Mylar gap seal tape (with the PTFE anti-chafe tape on the ailerons), but not having any better recommendations, I used the self-adhesive tape with the zig-zag leading edges. It came from Germany. I stored it rolled up for over a year, and it glued on quick and sweet as anything. That was in 2005, and they're still on there over 250 aerobatic hours later. I pre-flight it every day, and have not seen any sign of it peeling off. I did clean the area with acetone first of course. I have since incorporated exactly the same mod on my British (red) RF4, and it is approved by the LAA.

By how much should you reduce Va? By as much as you think appropriate. I really don't know, but I ensure I do not have full aileron above 100 knots. This tape has very significantly increased my roll rate -- nearly doubled it, but that will increase torsion on the whole wing. Do NOT roll and pull at the same time, the combined rolling and pulling loads could easily tear off a wing. I would suggest you get familiar with the standard airplane first, before adding the tape. Rob Dorsey, David Perrin, the Unipart Duo and the Skyhawks (among many others) all flew upward vertical quarter rolls in standard airplanes.

Previously I could fly a quarter vertical roll up and down, but with these seals I can almost fly a half roll each way with a humpty-bump flop over the top. Be very careful going downhill, you can easily exceed Vne if you don't start at stall speed and pull at least 4g to recover. Start by rolling through a small angle, with the throttle closed, and gradually increase the angle. Then you can transition to the full-power recovery.

Going upwards, be prepared for a tailslide. If the airplane slows to a halt pointing upwards, I find it best to hold the stick rigid in the central position with both hands (jam your elbows) and clamp your feet hard on the pedals, although some folk suggest putting everything over into one corner. Whatever version you use, the important thing is not to let the controls whack against their stops as you slide backwards through the air.

And start all this sort of experimentaion high up (5,000 feet agl) and over the sea or the desert. These airframes are more than forty years old, and you know how easily a dry old twig snaps. You don't want a heavy old Volkswagen engine falling on somebody's head... or your heavy old (or young) body.

Where these seals really help is in flying a clean Immelmann (roll-off-the-top). Pulling into a loop at 120 kt, even if you pull 4.5g all the way around (so the loop won't be circular) you're lucky if you're still doing 65-70 at the top when you have to make that half-roll. You're way below Va, so you know you can whack on full aileron, with rudder to taste, and get a much cleaner half-roll without sagging too much.

The best book on aerobatics, by far, is Alan Cassidy's Better Aerobatics. My well-thumbed copy is down at the hangar right now, but I guess we'll start an aerobatics section, and I'll put his address in there.

Happy Fournicating, Bob

[Edit by Bob Grimstead on Tuesday, November 18, 2008 @ 00:00 AM]

[Edit by Bob Grimstead on Tuesday, November 18, 2008 @ 00:06 AM]

[Edit by Bob Grimstead on Tuesday, November 18, 2008 @ 00:09 AM]

[Edit by Bob Grimstead on Friday, June 10, 2011 @ 06:17 AM]



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Posted Tuesday, January 2, 2007 @ 01:43 PM  

Thanks Bob - Sounds like good advice. As it happens, Rob Dorsey lives only a few miles from me and we meet from time to time. I took the RF4D down to show him last October when I did an annual on his Zlin. - I could tell it brought back memories.

Right now, I'm trying to get the basics right with the Fournier, the loop, the barrel roll (which have been working out very nicely) and particularly the last 1/2 of the slow roll. - It's a demanding little bugger! The Skyhawks made it look so easy! Once I get that consistently right, I'll move on to some sequences.

Steve

Bob Grimstead
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Posted Wednesday, January 3, 2007 @ 03:49 AM  

As you say, Steve, she's a demanding little bugger to get the aeros right... but how very satisfying when you do start to get there.

Rob was my Fournier instructor back in 1970 and could fly a beautiful vertical upward roll.

I watch the Skyhawks' routine over and over again, and still learn something more every time I see it. They were the masters.

A good inital sequence is:

Loop into wind, barrel roll, wing-over (or hammerhead if you're brave) and slow roll downwind. Then you could dive into a Cuban eight, or maybe an Immelmann, followed by a spin. The possibilities are endless. And it is all so cheap as she just sips fuel.

Happy Fournicating.

Yours, Bob

[size=small][Edit by Bob Grimstead on [TIME]1226980480[/TIME]][/size]

[size=small][Edit by Bob Grimstead on [TIME]1226980503[/TIME]][/size]

Bob Grimstead
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Posted Wednesday, January 3, 2007 @ 08:38 AM  

oops, of course that was an upward QUARTER roll.

Bob

Kadir
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Posted Thursday, June 17, 2010 @ 05:07 AM    MSNM

Hi guys,

It has taken me longer than anticipated ( doesn't it always? ) to get all the necessary parts for my RF5B, TC-PDK, but I think we have made progress.

While I wait for the parts to arrive I have been looking at modifications section of the forum.

RF5B is not cleared for acros and I have no intention to try even basic ones, yet, what is your view on any benefit of installing aileron gap seals on the RF5B? Would it be even legal?

Kadir

Jorgen
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Posted Thursday, June 17, 2010 @ 05:10 PM  

Hi Kadir,
at least in Sweden there is a general permit to install gap seals on gliders. I installed aileron gap seals on RF 5 b "SE-UDI" and I have to say I think they made a noticeable positive difference in low airspeed handling. I think you can find the description on how to install them here on the forum, otherwise I have the Swedish AD. Just two sorts of tapes, some mylar and it's easier if you're two people. I made cuts in the mylar over the hinges to reduce the risk of hang-ups there.

May the 4's be with you/ Jörgen

[Edit by Jorgen on Friday, June 25, 2010 @ 03:38 AM]

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