Uncovered landing gear struts

[Nev]

Is anyone flying with uncovered landing gear struts ? What is the drag penalty in the cruise ?
Besides additional drag are there any other pros or cons ?

[zkelley2]

I haven't covered mine... yet. So I don't know what the drag penalty might be, though I'd guess it's a lot. On 8.00 tires, it still does 130KTAS.
Cons are access to the brake line I guess. Also in the very long term, visual inspection for corrosion, but that's not where they're likely to corrode.

[Battson]

There must be a penalty, but I've yet to hear anyone complain.

In practice, you'd probably burn an extra 1.5 litres of AVGAS per hour and go the same speed anyway. So you need to know exact power settings to compare between setups.

Theoretically it does make some difference.... the Bearhawk undercarriage with 8.00 tires is probably more than 10% of the total aircraft drag, before you up-size to bushwheels.
A round body has approximately ten times more drag than an aerofoil (all other variables being equal). Every other surface on the aircraft is streamlined / aerofoil shaped for obvious reasons. However, area is equally important as drag. They are quite skinny legs compared to the rest of the plane.

For reference, a bare wheel about 8.00 size has a Drag Coefficient of about 0.25.

​​​

The only material advantage I can think of is weight savings. Probably a few pounds at least.

A word on streamlining elsewhere. I think that putting fairings on the leg and strut interfaces to the wings and fuselage, well - that's extra weight. If you were leaving the legs uncovered... every gram must be important. I guess you might not bother with all those fairings either.

I think it is best decided by personal preference and mission.

[Bcone1381]

Battson, your attachments are not appearing for me....I see 4 blue questions marks instead.

[Battson]

It's just drag coefficients from Wikipedia - Try this - https://en.wikipedia.org/wiki/File:14ilf1l.svg

[marcusofcotton]

Do a search over on Supercub.org and Backcountrypilot.org sites. Some have looked at it quite a bit, seems to range as I recall about 1-4 knots on airplanes that are only flying 70-90 knots.

[svyolo]

I guess if depends on what you plan on doing with your plane. If it is a cross country cruiser then lower drag is more important. If you are on 31's, you might not notice the drag, but probably want to keep the weight down. I am no where that I can measure it but I am guessing both gear legs are less than 1 sq yard of fabric, combined. Even heavy fabric and paint should be only a bit under a pound. The other side of the spectrum would be Oratex at about 4 oz combined for both gear legs.

If I were building a cross country plane I would make the gear legs airfoil shaped with ribs, and install wheel pants. I already covered my gear legs, but I am not sure if I would bother next time.

[Battson]

You would likely also cut off the steel fairings, if you didn't cover the gear legs and wanted weight savings. Hence my higher guesstimate of the weight.

[svyolo]

Didn't even think of cutting off the aft steel fairings. That would make the weight savings even better. Had I thought of it, that might have been my choice.

[Bcone1381]

Will the weight saved by leaving the fairings off be less than the weight of the extra fuel that must be carried to accommodate the drag increase?

I'm not a backcountry guy, but why do Cub guys leave the gear uncovered? I believe its to eliminate possible damage item and improve dispatch reliability. Then I wonder if bare gear legs for reliability grows to becomes a fashion statement. Thats ok, too. I like fashion.

[Battson]

A fantastic comment about the weight of fuel, Brooks.

[svyolo]

I have a pretty hard time trying to argue with that logic Brooks.

[Rollie]

Cubs don't really need to streamline anything. Drag goes up exponentially as speed increases and since Cubs don't have any speed, they don't have any drag. Cleaning it up aerodynamically becomes more important at higher speeds.

[Battson]

I have to say that the gear legs experience almost zero damage during off airport work. It should last longer than the tail wing coverings, provided you are not regularly landing on brush. Let alone driftwood - I highly dangerous act, in all respects.

[Gerd Mannsperger]

I would not worry about airfoils and coverings below a 100 mph cruise speed.

Above that the whole world changes. When we fly external loads that is the magic number. My maule on 31s would still do 145 MPH at 7500 feet and there it does matter a fair bit.

All depends on how much gas you want to burn The BH is a clean bird its a shame to wast the efficiency designed into it.

[Battson]

Looking at the SuperCub.org threads - e.g. https://www.supercub.org/forum/archi...p/t-29416.html there doesn't seem to be an obvious reason for leaving them uncovered, other than looks.

[Gerd Mannsperger]

The Bearhawks will never have the real cool look anyway as it is to difficult to mount a Gunn boot to the single strut