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Sealed or “Blocked In” Ends of Elevator/HS

Macdaddy53

I'm New Here
Rick Gray has a YouTube video of his champion RV-8 with the ends of his elevator and HS “blocked in” as he describes it. Anyone know how this might be done? What product could be used to seal the ends for a professional look? See screenshot from his video below:
 

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There is a youtube video on this. In short foam to fill the gap and then epoxy and flox on top. I dont like sanding flox, so i plan to use epoxy and micro instead.

I did something similar when i filled in my tip fairings i used foam then fiberglass cloth to hold the tip fairings to shape, then epoxy and micro. YMMV
 
Be aware there is a small degree of risk here (control jam) in return for no known aero benefit. And it complicates things when it's time to balance the elevator.

There is some benefit to capping the top of the vertical stabilizer, just to seal out rainwater.
 
I'm a poet but dont know it

Be aware there is a small degree of risk here (control jam) in return for no known aero benefit. And it complicates things when it's time to balance the elevator.

There is some benefit to capping the top of the vertical stabilizer, just to seal out rainwater.

Wow, this is exactly what i did.I sealed the vertical stabilizer to keep out rain water. I dont plan to do the horizontal stabilizer yet.

Off subject, should the rudder be 100% mass balanced, mine is not?
 
Off subject, should the rudder be 100% mass balanced, mine is not?

They are not 100% balanced, but here's the caveat...do not add mass aft of the hinge line. Doing so adds imbalance, which may reduce flutter margin. "Mass" includes filler, excess paint, and things like trim servos and tabs.
 
They are not 100% balanced, but here's the caveat...do not add mass aft of the hinge line. Doing so adds imbalance, which may reduce flutter margin. "Mass" includes filler, excess paint, and things like trim servos and tabs.

AND those ADSB/Nav/Strobe units that folks often use.
 
I enclosed all of my control surface end ribs except the inboard flap ends (and I tried doing that before realizing they needed trimming in place against the fuselage and had to grind it all out again). To me it was a lot of work but looks nice and it is difficult to imagine it could not reduce drag - those cupped surfaces are like barnacles on a ship hull. I do realize the risk of control surface jamming and have inspected my method and results carefully with an eye towards what could happen if anything slipped out of place.
 
It definitely looks nice, and you can’t argue with the beauty that Rick has accomplished with his many award winning airplanes, but I don’t understand the aerodynamic benefit. In fact I don’t think there is any, and maybe it’s a detriment, aerodynamically. These gaps aren’t seeing straight line relative wind like your wings, or your wingtips. They are seeing “spilled lift” that leaks from the high pressure side of the airfoil to the low side. It’s either positive lift on your wings, or download lift on your tail, but the argument is the same. You are using energy to create this lift (up or down), and allowing that lift to easily squirt unimpeded through that gap, destroys some of the lift. That tail needs to provide a certain amount of download, and if some of that download slips away, then it has to provide a little more. This results in an increase in induced drag over and above what would have been required, had you not created an improved pathway for the lift leakage. Does it amount to anything measurable? Probably not, but to think that this will be more aerodynamic and make you go faster doesn’t make sense to me. It’s heavier, and if you don’t build it correctly (not just foam and filler) it WILL crack eventually and look worse than it would have if you had done nothing. Make it look pretty, but realize, there’s no benefit outside of cosmetics.
 
Disagree

I....Does it amount to anything measurable? Probably not, but to think that this will be more aerodynamic and make you go faster doesn’t make sense to me. It’s heavier, and if you don’t build it correctly (not just foam and filler) it WILL crack eventually and look worse than it would have if you had done nothing. Make it look pretty, but realize, there’s no benefit outside of cosmetics.

I disagree, if it looks fast, it must be faster. QED ;-)

Isnt that why we paint airplanes??
 
I've given this process a lot of thought since I first saw an example of it.

While it looks beautiful, I don't think that there would be a measurable aerodynamic benefit in most cases.

Given that it adds weight, fabrication time, eliminates (or at least complicates) the ability to use piano hinge to attach the wingtips, makes it hard to see what's going on it there at inspection time, and can potentially entrap water, I'm passing.

I just don't see that the coolness factor outweighs all the potential downside.

I agree, when done right they look beautiful, but it's not for me.
 
Lots of sentiment here, both ways.

Anybody with a wind tunnel? We need DATA.

...Lots of beautiful data. Anything less is argument from inference, thought-experiment and appeal to "common sense."
 
There is an old VAF post by Bob Axsom who measured a speed increase with the tips closed.

But if we ignore that, it will quietly go away ;)

If I get bored enough in my upcoming retirement years, I might build a drag-measuring balance beam like the Wright brothers are said to have mounted to a set of bicycle handle bars - ride into the wind and see which test article out-drags the other. Anyone care to donate a trashed horizontal stab and elevator for a little research?
 
No windtunnel needed

Anybody with a wind tunnel? We need DATA.

...Lots of beautiful data. Anything less is argument from inference, thought-experiment and appeal to "common sense."

We dont need no stinky wind tunnel…..


We just need someone to do just one side of the elevator and go fly. If the plane yaws, then we know if it has an effect. If no yaw, then no effect.
 
AND those ADSB/Nav/Strobe units that folks often use.

That weigh the same as the Whelen bulb they were designed to replace?

When I see this kind of modification I wonder why someone wouldn't just build a fibreglass airplane if they wanted their plane to look like a fibreglass airplane...
 
i sealed all of my Rocket control surfaces to minimize excrescence drag. I also sealed the interior wingtips with aluminum tape for the same reason.

I used carefully shaped aluminum plates and trimmed standoffs underneath.

Given the time to fabricate all these modifications, the speed increase due to decreased drag should save all the extra build time sometime this century :).

Note: The wingtip sealing tape 'burst' due to the high internal wing pressure...

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EMP_0006_1.JPG.

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During flight testing, I did reach 208 knots 8500' cruise speed. (IO-540, Hartzell BA). This included several speed modifications. Put another way... 175-180 knots TAS at 10 GPH.
 
We dont need no stinky wind tunnel…..


We just need someone to do just one side of the elevator and go fly. If the plane yaws, then we know if it has an effect. If no yaw, then no effect.

You my friend have more confidence in the magnitude of forces involved and the lever arm afforded by the horizontal stab than I do.

The position the nose gear is in at the moment of liftoff has more effect on yaw than mods to the horizontal stab could, in my speculative opinion. But the Wright brothers bicycle-mobile wind tunnel would probably actually answer the question once and for all.

https://airandspace.si.edu/exhibitions/wright-brothers/online/fly/1901/apparatus.cfm
 
Obviously anyone who has a nosewheel doesn’t really care much about drag

(Grenade thrown, crouching in foxhole)
 
i sealed all of my Rocket control surfaces to minimize excrescence drag. I also sealed the interior wingtips with aluminum tape for the same reason.

Note: The wingtip sealing tape 'burst' due to the high internal wing pressure...

Now we have something interesting. Vern, how and where was that tape installed?
 
Some interesting wind tunnel data in NACA wartime report ARR L4J16 "Wind-tunnel investigation of rounded horns and of guards on a horizontal tail surface".

They were looking at planform shape, which is not exactly what is being discussed here, but lots of numerical data and some detailed tufting work indicates that big changes to the shape of the slot have negligible effect on drag, and the effect on control effectiveness and hinge moments is proportional to the change in planform area, not to slot shape.
 
Example of easy access for elevator balance after paint. When balanced independently, the left (trim tab side) elevator might need some. This a stack of steel plates. Other builders have installed a nutplate on the inside of the rib prior to close, then bolt on some 970 washers at balance time.

HS got a flush close out on the cap, but not the end rib.
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Rudder

Example of easy access for elevator balance after paint. When balanced independently, the left (trim tab side) elevator might need some. This a stack of steel plates. Other builders have installed a nutplate on the inside of the rib prior to close, then bolt on some 970 washers at balance time.

HS got a flush close out on the cap, but not the end rib.
.

THREAD DRIFT!

If I wanted to 100% mass balance my rudder, how would i do that, now that the cap is on and the rudders do not have a indentation; the rudder ribs are flipped around as compared to the elevator.
 
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