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Cruise performance

Oliver

Registered User
I recall an old thread that discussed cruise performance of cubs - speed penalties for different mods etc.
I regularly fly with a friend with a bone stock cub, 1500+ hr 150 hp, only mods are a 82/42 borer and 29"s.
if were both cruising at 2450 (both using digital tachs) hes got about 8 mph on me.

Im flying a recently rebuilt cub, rigged to spec, 70 lbs lighter, 160 hp (port/polish lycon), 82/43, 3" ex gear (uncovered), bags over my hydrosorbs, 31", bby bushwheel. 2450 im about 87mph 1500 msl 70*.
I would have figured turning a 43 pitch prop at the same rpm (and burning alot more fuel) would even things out. Guess not.

Anyone have data on common mods and associated speed penalty?
 
What is your loaded CG when compared to his while flying together? The plane with the further aft CG will have less drag.
 
Things that have made a difference in my limited experience:
1. Tire size can make a huge difference
2. Uncovered gear
3. larger tailwheel
4. Two many gopros

sj
 
Data point
160 hp, 82/43, 31" Bushwheels, standard covered gear, Scott tailwheel, 2450 rpm, 2000 AGL: 94 mph TAS
 
SJ time for a new bumper sticker: "Super Cubs make a Harleys look streamlined!"
 
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Can,t stand less than 100mph in an airplane. Aren,t those 35,s just wonderful. If you got to have em, recalibrate to kilometers/hour.
 
1950 manufacture: flaps, 160 engine, cruise prop, 8:00x6+Clevelands, radio and xpdr, no other mods - 115 mph at 7.5 gph. It has since received several bush- style mods and now cruises around 97. It is still a wonderful airplane, but I liked it better before the bush mods.
 
1950 manufacture: flaps, 160 engine, cruise prop, 8:00x6+Clevelands, radio and xpdr, no other mods - 115 mph at 7.5 gph. It has since received several bush- style mods and now cruises around 97. It is still a wonderful airplane, but I liked it better before the bush mods.
The real reason we hang all that stuff on our Super Cubs is so we can justify a Skywagon for trips!
 
In my experience, there is often significant differences in cruise speed (and other performance parameters) between similarly equipped cubs. Some I was never able to explain.

These are old airframes and many have been tweaked, rigging can be all over the place, angle of incidence of the wings can vary a bit, etc, etc.

Theyre all a little different. So be it.

MTV
 
Anyone have any idea how much difference it would make taking the dihedral out of a cub wing. I'm sure it would make it a little faster and fly slower, but how much?
 
Prior to cubs, spent alot of time in a Maule. Often switched back and forth between 8:50"s and 31"s.
about 8 kt difference but what i noticed was the wing AOA at level cruise and the different elevator position.
31"s created so much drag under the plane that to compensate, you were trimmed back to a higher AOA at level flight.
Im sure that flight attitude cost a couple knots along with aerodynamic drag of tires.

Re Cub, Considering covering gear and installing original bungee covers if I could gain a few knots...
 
You should fly faster and slower if you take some of the twist out of the wing. Dihedral should effect stability more than speed, The slower you want to fly the more stability you will want.
DENNY
 
1960, 160hp, 74/56 cruise prop, 8.50's,1125lbs, 2450 108mph, 8.1 us/gph (30lph) then I fitted 31's and bbw and saved a load of weight with electrical refit and other mods inc sutton exhaust under seat battery etc, weight saved roughly equalled added weight of ABW's . still with 74/56. 102mph @2450 8.1gph (30lph).
This summer I fitted the Sutton CS MT prop and now as follows:- 1144lbs, 31's inc bbw, lightweight elec, u/s battery as before. 110mph 2300/24" 8.3usg/h(31lph), 102mph 2200/23"6.7usg/h (25lph), 94mph 22/22" 5.9usg/h (22lph), all these figures are low down, approx 2000'amsl or less and have been leaned, I have a fuel flow so the flow rates are fair. It'll do more if you want to burn the fuel but it feels like the airframe max on 31's is mid-late teens flat out, definately so if I refitted the 8.50's but why would I do that!! I did the prop to increase flexibility, range and comfort, I still generally cruise at the speed I did before, circa 100mph, but now have greater range, does'nt feel like I'm thrashing the engine and have a hell of a prop to drag me out of whatever crap I found to land in!! Prop is smooth as silk and slows you down great on approach. Not for everyone but for the flying I do in the UK I'd do it again. Cheers, Ed.
 
Can,t stand less than 100mph in an airplane. Aren,t those 35,s just wonderful. If you got to have em, recalibrate to kilometers/hour.

Yup! Same here. I was actually trained on a 35. Now I'm waiting to invest in a Icon A5. Fell in love with that sucker.
 
I recall an old thread that discussed cruise performance of cubs - speed penalties for different mods etc.
I regularly fly with a friend with a bone stock cub, 1500+ hr 150 hp, only mods are a 82/42 borer and 29"s.
if were both cruising at 2450 (both using digital tachs) hes got about 8 mph on me.

Im flying a recently rebuilt cub, rigged to spec, 70 lbs lighter, 160 hp (port/polish lycon), 82/43, 3" ex gear (uncovered), bags over my hydrosorbs, 31", bby bushwheel. 2450 im about 87mph 1500 msl 70*.
I would have figured turning a 43 pitch prop at the same rpm (and burning alot more fuel) would even things out. Guess not.

Anyone have data on common mods and associated speed penalty?

Whitewings Aircraft Services, Starr Farmer at Lake Hood has done some fairings for cub extended gear, I got about 7-8 MPH increase on my Husky ( has cub extended gear and AOSS) and about 4MPH on the supercub. Also did streamlined fairings on the AOSS shocks too, both added quite a bit of speed compared to uncovered. My cub is about the same as yours, same pitch prop, 1250 lbs, 2450 is near 100MPH on 31's, now has 35's.
Well worth the added speed gain compared to uncovered gear, and looks good too.
John
 
Whitewings Aircraft Services, Starr Farmer at Lake Hood has done some fairings for cub extended gear, I got about 7-8 MPH increase on my Husky ( has cub extended gear and AOSS) and about 4MPH on the supercub. Also did streamlined fairings on the AOSS shocks too, both added quite a bit of speed compared to uncovered. My cub is about the same as yours, same pitch prop, 1250 lbs, 2450 is near 100MPH on 31's, now has 35's.
Well worth the added speed gain compared to uncovered gear, and looks good too.
John

Berringer had a set of gear at their trade show booth this weekend, carbon fiber gear fairings looked pretty streamlined and aerodynamic.
something similar tailored to PA 18 gear would work well.

IMG_2460.jpg
 

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Whitewings Aircraft Services, Starr Farmer at Lake Hood has done some fairings for cub extended gear, I got about 7-8 MPH increase on my Husky ( has cub extended gear and AOSS) and about 4MPH on the supercub. Also did streamlined fairings on the AOSS shocks too, both added quite a bit of speed compared to uncovered. My cub is about the same as yours, same pitch prop, 1250 lbs, 2450 is near 100MPH on 31's, now has 35's.
Well worth the added speed gain compared to uncovered gear, and looks good too.
John

would you mind sharing a few pictures of the fairings?
 
Berringer had a set of gear at their trade show booth this weekend, carbon fiber gear fairings looked pretty streamlined and aerodynamic.
something similar tailored to PA 18 gear would work well.

View attachment 31332

I've thought that would be pretty nice. Just shrunk wrapped mine per Douten's suggestion, but not sure if there's a diffference yet.
But a set of CF fairings might work well.


Sent from my imitation glass cockpit using SuperCub.Org mobile app
 
would you mind sharing a few pictures of the fairings?

Shots of fairings on Husky, essentially same as cub as the Husky has extended cub gear.
John
 

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Not that familiar with Oratex, but from what I gather, looks like you could cover the gear legs in place using their process
save a lot of downtime and simplify the task.
anyone used Oratex before? Thoughts?
 
You want to fair that aft leg of the A frame, in addition to covering it. You don't want to leave that trailing edge round.
 
You want to fair that aft leg of the A frame, in addition to covering it. You don't want to leave that trailing edge round.

Very correct, if no tapered trailing edge a waste of time as turbulence is still there. Ideal length from front to trailing edge is 3:1 ratio, we made the AOSS fairings slightly less as they looked odd too long, but the fairings work on gear legs and AOSS if made correctly, speed addition is pretty big for these minor mods. Where else can one get about 5% or more increase in speed this easy?
John
 
A friend (who is a member here but doesn't post frequently) just covered the gear on his -18. He said he got 3 or 4 mi/hr gain by doing so, no aft fairing, 31 tires. Just a data point - - -
 
A friend (who is a member here but doesn't post frequently) just covered the gear on his -18. He said he got 3 or 4 mi/hr gain by doing so, no aft fairing, 31 tires. Just a data point - - -

Will be faster with the correct trailing edge for sure. Read about the testing done on round balls vs bomb shaped ones, all with same diameter frontal area, huge difference in aerodynamics and speed.
John
 
There's a difference in a linear, blunt shaped trailing edges (covered gear, no aft fairing) vs pure round cross-sections (like bare tubes).

Here's why: https://en.m.wikipedia.org/wiki/Kármán_vortex_street

Interesting. Per this page, it appears that simply adding a single fin trailing edge makes a tremendous difference. I'd be curious the real difference between a full airfoil enclosure vs adding a trailing edge fin.

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Found the answer I think - the video link shows increasing speed around the tube with the fin. As speed increases, the air starts breaking off the fin's trailing edge, as shown in the screenshots:

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I actually have an experiment in mind when I mount my GY26s that's along those lines, Farmboy.
 
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