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Tie down ring drag penalty

Fly2KiteSurf said:
What about a flat airfoil shaped blade with a hole for tie-down, and machined threaded shaft that goes up into the wing, and for alignment since the threads won't ever be perfect when tight with blade to align with airflow, the airfoil flat with hole could swivel freely to aid in tie down alignment and flight alignment which could be different. Yes, a lot of engineering and fabrication involved, but isn't that what we enjoy?
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So you're making dorsal guiding feathers?

Webb said:
You have to know these things if you are a king.
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How do you know he's a king?!?

ds
 
I leave my tie down rings in place as well and just accept the massive speed loss so I don't have to test my failing memory trying to find them. :)

PXL_20251127_202826146.jpeg
 
RV6-KPTW said:
I see 2+ knots penalty (I want to say 4 but that seems absurd…) using the standard Vans tie down rings. I replace them with an appropriately sized screw.
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Don't install screws. That will trap the heavier sea level air which you will have to carry to altitude
 
6al4v titanium could be a serious issue…think of the galvanic reaction that should occur…intragranular corrosion could destroy the whole structure…

(okay…I’m kidding. In ten lifetimes, I don’t think this would be an issue….i’m going back to wishing for a damn disco ball….)
 
"One good test is worth a thousand expert opinions" -- Tex Johnson, Boeing Test Pilot
 
Good points about a variety of aspects. I replace my tie down rings with jack points.

For those who pull the tie down rings (there has to be some of you), do you leave the hole as is?
 
RV6-KPTW said:
Good points about a variety of aspects. I replace my tie down rings with jack points.

For those who pull the tie down rings (there has to be some of you), do you leave the hole as is?
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Yes. What is the perceived risk of doing so?
 
Can you take off from a conveyor belt,,,,, yes! it was proven on Myth Busters


But if you are still concerned about the drag coefficient, just add a bigger motor!
Formula added for your convivence

Fd = cd 1/2 ρ v2 A (1)

where

Fd = drag force (N)

cd = drag coefficient

ρ = density of fluid (1.2 kg/m3 for air at NTP)

v = flow velocity (m/s)

A = characteristic frontal area of the body (m2)
 
Used these for a very long time on my Mooney. At least the install/remove cycles on the aluminum aircraft threads get reduced. No shimming needed for aero alignment though I did put thin layer of teflon tape under it. Never saw any related galvanic corrosion. I will use them on my build if I can stay alive long enough. I’ll let others debate their aero impact.


LASAR tie down/jack point
 
RV6-KPTW said:
do you leave the hole as is?
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Certainly not, this a major nogo. Think about these gaping holes, and @RV6-KPTW post above is right on the money. I usually tape them over, but a flush cover would be better since applying some tape will no doubt induce a lot of vortices disturbing the boundary layer.
That being said, leaving them holes open in the slipstream might also, given a certain AOA, lead to them act as a whistle, which could be interpreted as the sound from the stall warning.
We have to play it safe out there!

Ok, now kidding aside, the total drag of my Insta360 on top of the VS, and the Drift Ghost installed close to the pitot probe under the left wing, have a noticeable bearing on speed (about -1.5 KIAS), and the skid ball definitely shows some deflection...
Ok, back to the tie-downs, those are more fun.
 
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