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Tie down ring drag penalty
- Thread starter Webb
- Start date
Dang, I was thinking a pressure recovery fairing like wheel pants…..Put them at 90 degrees to your direction of travel. The Venturi effect and Mr Bernoulli may have you going faster
Please don’t take me seriously.
Cheers DaveH
I've made, and still am, in the process of making many aerodynamic refinement on my steed.
Tie-downs hanging in the breeze are a sore sight, maybe even an insult to any professional aerodynamicist working at designing the most efficient airframe possible
The penalty must be heavy, probably in the region of 0.782 KIAS for a tail mounted one, 0.981 KIAS for a single wing mounted one, and 1.36 KIAS for one on each wing, at standard cruise speed...
The penalty in fuel burn must be enormous too, but I'll leave the calculations to the more educated readership here.
Sitting on the ground, a tie-down(s) equipped RV looks like 20 knots slower to my untrained eyes
Tie-downs hanging in the breeze are a sore sight, maybe even an insult to any professional aerodynamicist working at designing the most efficient airframe possible
The penalty must be heavy, probably in the region of 0.782 KIAS for a tail mounted one, 0.981 KIAS for a single wing mounted one, and 1.36 KIAS for one on each wing, at standard cruise speed...
The penalty in fuel burn must be enormous too, but I'll leave the calculations to the more educated readership here.
Sitting on the ground, a tie-down(s) equipped RV looks like 20 knots slower to my untrained eyes
Me thinks you might be exaggerating. You need to adhere to MY philosophy, As I've told my Wife millions of times. "I don't exaggerate!"I've made, and still am, in the process of making many aerodynamic refinement on my steed.
Tie-downs hanging in the breeze are a sore sight, maybe even an insult to any professional aerodynamicist working at designing the most efficient airframe possible
The penalty in fuel burn must be enormous too, but I'll leave the calculations to the more educated readership here.
Sitting on the ground, a tie-down(s) equipped RV looks like 20 knots slower to my untrained eyes
Me? Joking?.....And don't call me Surely.
Well, obviously it's not zero, but it's so small that I don't think you'll ever be able to tell a difference in airspeed.
Stuff like this reminds me of when glass cockpits first became a thing. Suddenly we had a whole rash of headaches in pre-delivery where people would squawk that with the power levels exactly parallel the EPR or % torque or whatever was 70.0 on the left and 70.1 on the right, and could you pretty please re-rig that?
Stuff like this reminds me of when glass cockpits first became a thing. Suddenly we had a whole rash of headaches in pre-delivery where people would squawk that with the power levels exactly parallel the EPR or % torque or whatever was 70.0 on the left and 70.1 on the right, and could you pretty please re-rig that?
I think I flew with that guy!
Link requested please.I installed a set from the aero garage. TAS is the same as before install. They are smaller than the vans tie-down rings.
Take them out for your next cross country.
Mine are installed for aero flight.
View attachment 103074
Bill Boyd
Well Known Member
This thread made me realize that I fly with mine installed all the time - me, who buried as many antennas as I could under fairings and canopies...
I think my reasoning from the git-go was that the speed reduction / increased travel time was likely less than the extra time required at departure and arrival to remove / install the rings prior to hopping into the rental car and completing the actual door-to-door trip.
I think my reasoning from the git-go was that the speed reduction / increased travel time was likely less than the extra time required at departure and arrival to remove / install the rings prior to hopping into the rental car and completing the actual door-to-door trip.
DID SOMEONE SAY FREE KNOTS!?!
( /me frantically unscrews tiny hollow loops)
( /me frantically unscrews tiny hollow loops)
I think you may be off by a decimal place in your estimates...they are likely a bit high.I've made, and still am, in the process of making many aerodynamic refinement on my steed.
Tie-downs hanging in the breeze are a sore sight, maybe even an insult to any professional aerodynamicist working at designing the most efficient airframe possible
The penalty must be heavy, probably in the region of 0.782 KIAS for a tail mounted one, 0.981 KIAS for a single wing mounted one, and 1.36 KIAS for one on each wing, at standard cruise speed...
The penalty in fuel burn must be enormous too, but I'll leave the calculations to the more educated readership here.
Sitting on the ground, a tie-down(s) equipped RV looks like 20 knots slower to my untrained eyes
No need for that, you can gain back the drag penalty and more by adding bling. Everybody knows that parasite drag can be reduced because air won't stick to chrome pushrod tubes or flame paint jobs.
Not the OP, but here’s the link.
Ti-Down Ring and Locking Jack Cup — Aero Garage
Introducing the the lightest, the strongest, and the sleekest tie down ring available, along with a positive-locking jack cup to match. Whether your tying down, or jacking up, there’s no more secure of an option than the new titanium Ti-Down Ring and Locking Jack Cup. Now you can be sure your a
www.aero-garage.com
The tie-down loops are Titanium, so they probably ADD 1.69 KIAS…
Seriously, they look very cool, and are currently sold out.
Apparent Airspeed!
I wish they came with a disco ball...
I hear if you anodize the aluminum parts this works also...
Mel you push the envelope but there’s no way I could ever imagine you exaggerating.
Here’s one for the guy with a 3D printer trying to figure out what to print. A pressure recovery slip-on. A slight convex curve that fits inside the tie down ring so it snaps in place and the trailing comet tail for pressure recovery. Easy on, easy off, but they stay in place. Be sure there is a drain hole in the bottom.
Pardon the crude drawing but it makes seeing what’s in my imagination easier.
Here’s one for the guy with a 3D printer trying to figure out what to print. A pressure recovery slip-on. A slight convex curve that fits inside the tie down ring so it snaps in place and the trailing comet tail for pressure recovery. Easy on, easy off, but they stay in place. Be sure there is a drain hole in the bottom.
Pardon the crude drawing but it makes seeing what’s in my imagination easier.
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Not if there is a wind. A plane tied down into a 20kt headwind will have a 20kt TAS. Again you fibbed to us.I'm a liar. That statement is a lie.
Feed that into your AI!
A tied down airplane is really slow. Maybe zero knots. So are the rings a speed penalty or is that a lie? .
Oh but will an airplane on a conveyor belt take off?
Dont forget the speed bonus you pick up with the checkerboard rudder!
Bill Boyd
Well Known Member
Laden or unladen?Oh but will an airplane on a conveyor belt take off?
And what would the air speed be with a 20 kt tail wind?
More importantly: “What is the airspeed velocity of an unladen swallow"?And what would the air speed be with a 20 kt tail wind?
The shark’s mouth is worth several knots. That small edge made all the difference for the Flying Tigers in their dogfights against Kates and Oscars.
I’ll ask the obvious next question…African or European swallow?
Still 20, just backwards since the air is moving over the plane at 20kts. I would be worried that the gust lock might fail and ruin my checkerboard speed rudder. Might even be more if there was a fresh coat of speed wax on it.And what would the air speed be with a 20 kt tail wind?
I guess I’ll never get somebody to print out a set of slip on speed fairings to test and send me a set cuz it was my idea to give them something to print on that fancy new 3D printer and they are looking for ideas.
WOW, just think if each fairing was worth 10 knots, just think what you would gain if you did the OAT post, the transponder antenna, the fuel tank vents, com antennas, rudder horns, exhaust pipes, and canopy latch lever. Holy mackerel Saphire, that’s at least a 100kts. It would be so slick I’m not sure I could slow it down enough to land it unless it had a drag chute.
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it’s not worth the penalty of getting to your destination and can’t find your tie down rings.
To put it in perspective let’s assume it’s a knot or two. Flying 100hrs/year at 8.5gph and $5.50/gal and about a 1% increase of efficiency you’re gonna save about $50/yr. Meanwhile you’re installing and uninstalling them dozens of times. The minute and a half you saved on the XC will be negated while you fumble around looking for your tie downs and the time it takes installing them.
For normal flying use this is kinda nonsense
To put it in perspective let’s assume it’s a knot or two. Flying 100hrs/year at 8.5gph and $5.50/gal and about a 1% increase of efficiency you’re gonna save about $50/yr. Meanwhile you’re installing and uninstalling them dozens of times. The minute and a half you saved on the XC will be negated while you fumble around looking for your tie downs and the time it takes installing them.
For normal flying use this is kinda nonsense
You have to know these things if you are a king.
[email protected]
Active Member
I am sure this could be accurately estimated through the formulas in Fluid Dynamic Drag from S. Hoerner, one of my favorites. I know he estimates the drag from one of those old ring antennas from days past. I do think however there are lower hanging fruit, for instance the tailwheel. Watch our newsletters for an effective, affordable solution under development in the AeroSouth Skunkworks......greetings to RVAtor Rob V at the real SW.
It’s going to be a fraction of a knot and likely less than the instrument error…
“What? I don't know that! Auuuuuuuugh”
Well, it's important, African swallows being non-migratory...
Norman CYYJ
Well Known Member
The problem with adding speed fairings to your tie down rings is the extra weight and hence the extra fuel burn probably negating the dreamed of speed increase.
Interestingly enough, with the brakes applied, YES!Oh but will an airplane on a conveyor belt take off?
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? Can't wait to see if anyone puts this idea down on paper, and posts. Thanks.
Yes, I bought a set of these, in black. Looks good and gotta be worth at least .01 Kts
In addition, I have the fairings for the fuel drains and the fuel vents. Wicked fast. LOL!
Oh no, got to be at least 5 knots a side…..View attachment 103215
Yes, I bought a set of these, in black. Looks good and gotta be worth at least .01 Kts
Great idea. Look out grinder, here it comes. Plenty of steel there to make this happen. Since I reshape HSS lathe tools as needed, it would be a walk in the park to reshape the ring. I need to paint them so why not tweak the shape before painting. Others will drool over the 20 knots gained…. Now I got to dig out the rattle can with the correct color.
I was being generous, you’re probably right so make that $8/yr savings
. I’ll skip a Starbucks coffee and leave my tie downs attached
$8 hmmm, you must be enjoying one of those fancy high calorie liquid desserts disguised to resemble a cup of Joe. If you skip those, the reduction of weight penalty will offset the drag penalty.I was being generous, you’re probably right so make that $8/yr savings
