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Cover my gear legs or not

The Kid

FOUNDER
Thompson Falls
I am having my cub rebuilt. I have the std heavy duty gear legs with 31s. I am tired of 82 mph TAS. Would I pick up any mph with covered gear legs or not? Any disadvantages to covered legs? I also have my bungees covered with a bag. Would going back to the metal streamlined covers give me more mph? Any disadvantages to that?
 
Wanna go fast? Cruise prop and stock tires ought to get you over 100 mph. Wanna go into the bush? Your airplane will be slow. I bet the gear leg fabric is 1-2 mph.

My Decathlon has these super neat pants with special fairings on the bottom. I cannot tell the difference, on or off.
 
only had ONE customer want covered gear(redone at rebuild)...

we had to replace their gear legs because of rusted clean through at the bottom......
 
Mike above has a point. If you are tied down outside all year it might hold moisture and promote rust and corrosion.

I have heard (but not tested) 2 to 3 MPH. The streamlined bungee covers might add 1 or 2 more. It does make a difference. Not much downside really unless you are running 50 year old gear and need to constantly check for cracks and rust.

IMHO only

Bill
 
Covered my gear when I rebuilt my cub. It lasted about 150 before it cracked and looked like hell. Ended up cutting it off. Lost 3-4 mph. Picked up 5mph with a firman pod on.


Sent from my iPhone using Tapatalk
 
When you say "cover my gear", are you also fairing the trailing edge of the aft leg? Or just leaving it round? They had this all figured out decades ago, hard to believe it's still a point of discussion! OF COURSE covered AND faired gear will be less draggy then naked gear. Whether you notice or not isn't the point, the extra drag is there regardless, also the lessened climb and range. There's nothing special about a Super Cub in this regard, other then perhaps some excess power to mask the effects, but they are still there. Fairing the aft leg is as easy as going to any lumber yard and getting door casing, gluing 2 pieces together, and then ripping a 45 degree angle in the front, a notch in effect to cup the chrome moly. Use JB Weld to attach it to the CM. It will have a mechanically stout blunt trailing edge,about 5/16", (which is less draggy then a sharp trailing edge, unless that sharp trailing edge is so elongated that it is then cleaner but now very fragile) in about 2 1/2" of width, with the wide part being 1 1/4" or so. That can be adjusted to meet the tubing dia. so it all matches up. So now, instead of TWO round tubes out in the airflow, you have "less" then one, just the leading edge of the forward leg, NO turbulence between the two legs, and a faired rear leg.
 
Streamlined covers are good for 1-2 mph as Bill said above. I put them on mine last time I replaced bungees. I struggled with covered vs uncovered legs at rebuild and stayed uncovered. Although I think covered looks nicer and I know it has to be good for another 2 mph (possibly 3) I figured they'd either get beat up and ratty, or the first time I missed the step I'd mess it up good.
 
Here's my experience. Like Perry, I picked up 2, maybe 3 mph by installing streamline bungee covers to replace the bags.

So I figured that covering the gear legs should be good for at least that much. I was surprised that covering my gear, standard -18 style on my -12, gained almost nothing - maybe 1 or 2 mph max. Dunno why that's the case, but there's a data point.

I was also surprised that going back and forth between 8.50, 26 ABW, and 31 ABW tires didn't make much difference in speed. Again, maybe 3 mph.
 
My homemade belly pod gave me a couple mph too. Must clean up some of the turbulence around the cabane/shock strut area.
 
Ray Stits detailed the “fabric drumming” issue on the gear legs in a technical bulletin some 30 years ago. Personally, the airplane looks unfinished to me with no fabric on the gear legs but I don’t fly where I have a potential need to vigorously inspect for cracks. Apologies for the lousy pic
 

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Mike above has a point. If you are tied down outside all year it might hold moisture and promote rust and corrosion.
This issue can be prevented by leaving the lower 1 or 2 inches uncovered.

I am tired of 82 mph TAS.
What prop diameter and pitch do you have? If you are running a "Borer" with a 41 pitch, that is your speed issue. Increase the pitch by 1 or 2 inches. Your initial acceleration may be reduced slightly, the climb will not change much and your cruise speed will increase.

Fairing the aft leg is as easy as going to any lumber yard and getting door casing, gluing 2 pieces together, and then ripping a 45 degree angle in the front.......
You can reduce the weight gain by using balsa wood. That is what the old airplanes used to streamline the wing struts.
 
its really a personal decision. It probably simply boils down to your mission, and how you want it to look....I struggled with this one recently since i'm doing my fabric right now...in the end I decided to cover my gear....mostly because of looks....(my preference).....I will alternate between floats and wheels and skis....so it probably was a waste of my time...but it's done now.
 
I went to great lengths to fair gear legs with streamlined ribs and aluminum,
gained maybe 2-3 mph.
I think objects in turbulent air aft of prop arc don’t produce the same drag penalty as what’s been demonstrated in clean air wind tunnel experiments.
 
You can reduce the weight gain by using balsa wood. That is what the old airplanes used to streamline the wing struts.[/QUOTE]

True, but it's not readily available at any lumberyard. Pine door casing is. Way back when I was a finish carpenter, a standard mass produced door casing was officially referred to as "2 1/4" Streamline," available in clear (one piece, not finger jointed out of short sections) or a less expensive finger jointed version. I installed miles of the stuff, and it's still super common. An odd coincidence in it's name but that's the stuff! Of course anything could easily be made, but this product was so inexpensive and perfect for the job it was hard to improve on. My shock strut fairing, with a 1380 HD shock cord with a Fox airshock to control the rebound, Idaho welder John Roberts (AvWeld) made this for me and it works great, splat and stick, with no bounce back.

Every time I hear those reports of belly pods adding a bit of speed, I wonder why I have yet to fabricate one. What a win/win.

"So I figured that covering the gear legs should be good for at least that much. I was surprised that covering my gear, standard -18 style on my -12, gained almost nothing - maybe 1 or 2 mph max. Dunno why that's the case, but there's a data point."


Yes, but was the aft leg faired?? 1 or 2 mph is nothing sneeze at regardless.
 

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not worth the effort

Couple pics:

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2-3 mph, while lower then in my experience, isn't worth the effort? Then again, my daily driver is a Prius, so my take on drag reduction is skewed!
 
Prop pitch becomes the ruling factor at some point.

Props pull to a certain speed, then it does not matter with fixed pitch- above that speed you are just making noise.
 
2-3 mph, while lower then in my experience, isn't worth the effort? Then again, my daily driver is a Prius, so my take on drag reduction is skewed!

seems folks are getting same result from fabric covering vs faired aluminum covers.
 
You can reduce the weight gain by using balsa wood. That is what the old airplanes used to streamline the wing struts.
True, but it's not readily available at any lumberyard. ....

Every time I hear those reports of belly pods adding a bit of speed, I wonder why I have yet to fabricate one. What a win/win.
I guess that I'm more fortunate. There is a hobby shop with balsa wood closer than any lumber yard to me.

The speed increase from the belly pod comes from the pod streamlining the cluster of the landing gear and it's parts. Also some depends on the fuselage shape with the pod, improving the aerodynamics of the belly.
 
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To me it's just more efficient and efficiency is range and time. When you're NOT flying near airports, range and time are huge. If you flew for 5 hours, at a speed of 4 mph faster, then you'd be 20 more miles further and about 12 minutes sooner (at 100 mph) than the guy without the covered gear and metal bungee covers. I gotta think about this.
 
Cleaning up your aero can help fuel burn at the same airspeeds.

Even if you’re prop limited in speed, lower fuel burn equals longer range.
 
To me it's just more efficient and efficiency is range and time. When you're NOT flying near airports, range and time are huge. If you flew for 5 hours, at a speed of 4 mph faster, then you'd be 20 more miles further and about 12 minutes sooner (at 100 mph) than the guy without the covered gear and metal bungee covers. I gotta think about this.
Think about this while you are looking at a map of Canadian airfields: Suppose that you get the urge to visit one of our fellow members who happens to live in one of the lonely outposts in Canada's far north. Know also that weather reporting between these airfields is sometimes rather sketchy. Head winds are on occasion more than anticipated. Low clouds block routes requiring deviations around whatever. Now after dealing with these issues you are almost at your destination, only a mile or two to go, over a large lake or forest, the engine sputters as the last drop of gas is consumed. You had decided to leave your gear legs uncovered, what are you thinking now? "OH I WISH I HAD JUST ONE OR TWO MORE MPH! Perhaps I could have made the field." You may not be hurt, but? Even if only slightly damaged, your airplane may not be recoverable due to the distance from help. Can you walk out?

Those who fly only in the very populated sections of the lower 48 don't as a rule have to think very seriously about this issue. If you are at all adventuresome, you will want and need every last speck of speed and drop of gas which is possible.

Take this as a very strong hint from someone who has been there and done that on more than one occasion. Never ever leave any MPH or OZ. of fuel behind. I never bent metal, but I'll tell you that my nervous system had to rest up a few times.
 
I have a friend who got a great deal on a hail damaged Subaru with almost no miles on it a few years ago, and I once asked him if he noticed if it got unusually high MPG. Not a pilot, he didn't get it. The funny part was, his last name is Hale, and he is well known for working any of his vehicles extremely hard, so a Hale/hail damaged car was right up his alley.
 
How about balsa fairings on both tubes, no fabric? Wetted area, spiral slipstream, turbulence. I notice no one is covering the lift struts like Bellancas' early designs.
 
We covered my extended cub gear on my Husky in aluminum, tapered the aft end. Gained 5 mph. Then covered the AOSS shocks with tapered cover about 8" long, gained 3 MPH.
Use the formula of 3 times the length of whatever the diameter is to gain the best speed.
Not a cub, but have essentially the same covers for the cub, same gear legs. At least 3 MPH minimum. Husky is just faster so gains are bigger.
John
 
I've wondered about different options for increasing airspeed, so appreciate this discussion. A number of things have been discussed, but they're likely not cumulative. Seems like temporary fairings for gear legs, bungee/hydrasorbs, wing strut fittings, tailsprings(?) could be made from carbon fiber or Kydex. Paperwork probably wouldnt be an issue as they'd be easily removed. That way we could put them on when making a long trip, and take them off before our friends see us.

Ive also thought about changing props, for say a trip between Alaska and the Midwest. I run a 41 pitch Borer, but also have a faster prop. But that would require having a different prop at your destination, a licensed mechanic and logbook entry, as well as different weight and balance paperwork. Makes a controllable pitch prop sound interesting.

Jim
 
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