L2 on Steroids

[Ed O'Brien]

I picked up my L2 on Saturday. Bolted on her is a new (rebuilt to new by Don's Dream Machines) C-85 supposedly kicking out the power 95 or so, horses. I've got a Sennsenich wood prop 72x42 and a Stromberg Carb. Good news first. It flies faster. Into a 5 knot wind I was still making 80-82 nautical miles of Kansas farmland pass under the L2s belly. So I calculate it's now about a 95-97 mile per hour plane at 2450 rpm. It's very quick on take off. Tail rise and nose lift off are faster but I can't give you a figure here. The climb was about 5-600 feet a minute... meaning 3-4 minutes to my standard 1500-2000 Agl cruise altitude. I felt like I was in complete control in every part of the flight regime as opposed to inputting a flight command and waiting for the plane to react then negotiating with it for the rest of the manuever. Which is a standard way to fly these very light birds.

I met some wonderful Army Blackhawk Drivers and their crews. They were transitioning from Ft. Leonard Wood in Mo. to Ft. Carson near Colorado Springs. They offered a straight up trade... my L2 for one of their Blackhawks. Seeing they were great guys but unlikely to actually sign off on the deal, I passed on their offer but thanked them for making my day.

Now the bad news. Twelve gallons of gas used to take me
nearly 225 miles. With the A-65 engine I'd burn 4.2 gallons
an hour and get 2 hours and 30-40minutes of flight time.
With the new "big engine" I'm 1 hour and 40 minutes...
1 hour and 50 minute legs tops. I think I've shorten the short little legs of this baby bird by about 40-50 miles per tank. Meaning on this trip (Wichita to Denver) I had 4 gas stops and could have driven the distance a little faster in my car. Given that some of my gas stops required me to call the FBO man and have him unlock the pump (a 30-40 minute wait) or have me inspect a US Army Blackhawk helicopter and talk to the pilots about a possible trade for my L2... afterall even fantasy bartering takes time. You can see the speed up in cruise is more than reduced by return trips to the ground. So shorter legs that run faster and climb faster too. I've got an L-2 on steroids. BUT, as with all the ball players that have used steroids know: The stuff will juice your performance but shorten your career... or in my case the distance between gas stops. There you have it and with regards; ED OBRIEN

[VictorBravo]

Re: L2 on Steroids

Ed, sorry to cast doubt, but something doesn't seem right. With 90-95 HP and 42 inches of pitch, the L-2 should be leaping off the ground and into low earth orbit with great gusto, not 5-600 FPM.

If it was climbing poorly because it's a cruise prop, then you should have gotten 100 MPH out of 95HP, which would at least be some consolation for the climb.

But poor climb AND low cruise with 95HP? Somethin' ain't right.

IMHO you need to immediately borrow someone's metal prop and do a flight test. A badly contoured propeller or a propeller with a rough surface or the brass and rivets causing bad airflow... those are things that would give you the bad results you are getting.

You also need to be looking at your airframe closely... Some versions of the L-2 have a built-in boat anchor because of the triangular cutouts at the rear of the wing root, it effectively puts a big whoop-dee-doo in your "elliptical lift distribution" curve. That's the reason the L-2's don't climb as well as the civilian airplanes. But that should make a little difference not a big one.

If your airplane has spoilers you need to make sure they're shut in flight, not just on the ground. You also need to make sure they are completely flush at the front edge when closed.

If no spoilers, I'd look at things like the wing root cover strips being loose and letting a lot of air through.

If your airplane weighs a couple of hundred pounds more than other L-2's, maybe that's it.

I have no experience with the L-2, so others may know a lot more than me, but it sure seems to me that there is something airframe or prop related that is not kosher.

Bill

[Ed O'Brien]

Re: L2 on Steroids

VictorBravo;
6500-6700 ft pressure altitude could be the issue. IT was hot and I did the reported test at Goodland, KS with about 94-96 degrees outside. You sea level boys always think we're fibbing about altitude... it's why every little ol' mountain in Colorado has some flatlander pasted to the side. I'm still analyzing my data off the GPS. As far as the prop goes. By the way, I am buying a metal prop (I think a McCauley 72/44 or 45 will be the choice but I'm still thinking about that... because, I can't afford it at the moment as the months (3 months actually) extra money was just given over to the engine transfer shop.
All the best; ED O

[Ed O'Brien]

Re: L2 on Steroids

Victor Bravo;
A couple of more goodies to be fully responsive. (And by the way I thank you for your missive) NO spoilers! My L2 is an A model. Straight as an arrow as we've just rebuilt her from the ground up. It is heavier than nomal. We just reweighed it at the shop and I don't have that number (log nbooks are in the plane right now) but me, full tanks, and the gear I had in back left me 72 pounds under gross of 1300 pounds.

[Ragwing nut]

Re: L2 on Steroids

Your numbers are on par with our L-2M. Worst thing about the L-2 is range. They are pigs compared to a BC-12 with an average empty weight over 900 lbs. I have only flown one with an 85 in it and can't imagine flying one with anything less. Ours was over propped with a 71-48 metal prop and would climb out 4-600 fpm on most days as was less than that when it pushed 100* or better. Criuse about 105 with a closed cowl. I look foward to getting our YO-57 together with an O-200 or a stroked C-85 which is the lightest of all the tandems.

mike

[O.Taylor]

Re: L2 on Steroids

I followed John Collier's advice and put two 12 gallon wing tanks in my bosses L-2, it has the O-200, just got the wings on Friday, so it will still be awhile before the first flight, but I'd like to think 26 gal. should help some, O.T.

[VictorBravo]

Re: L2 on Steroids

You sea level boys always think we're fibbing about altitude... it's why every little ol' mountain in Colorado has some flatlander pasted to the side.

SEA level !?! I'll have you know that I learned to fly at Santa Monica airport which was nothing short of 75 feet above sea level, Sir!

I have some time flying in the mountains back in my sailplane days. I routinely take the T-craft to a couple of airports above 4000 MSL, but I have not yet taken it in and out of genuinely high altitude strips.

The performance you have noted seems far more appropriate considering a DA or PA of 6500. I still think the metal prop will give you something useful, glad you had the same idea.

Assuming for the moment (based on engine swap) that you are not trying to have an Oshkosh champion down to every detail, I might suggest a couple of things for you to consider to give the old girl a little more oomph at altitude... forgive the rant or the repetition if you've heard this before:

I sincerely believe you will get a significant benefit by combining 1) vortex generators, 2) gap seals, and 3) fiddling with the thrust line just a smidgeon.

Gap seals on the ailerons will help in climb. There are two big offenders, the curved slot between the aileron and the wing (which is indeed there for a reason but costs you something), and the big hand-size holes where the hinge brackets go. Any loss of air through those gaps is reducing the L/D of your airplane.

I have the square aileron hinge bracket holes covered on my BC and I swear it helps a little. Maybe someday I'll measure it, and maybe someone will prove me wrong, but I think they do something. They don't interfere with the roll rate AT ALL because they don't affect the slotted aileron concept. If you are interested I'll post photos of my seals.

The slot in the aileron, and the way the aileron leading edge moves down into the airstream is there for two reasons. The slot is (hopefully) to accelerate air through the slot under certain conditions to delay the wing from stalling, and/or to prevent "tip stall" if you deflect the aileron downward (more lift on one wing) by adding some high energy air into the boundary layer. The "Frise" aileron concept helps reduce adverse yaw by providing "proverse" yaw via adding some drag to the wingtip that you are trying to turn into.

So much for 'aero 101'... now into the mad scientist quadrant.

If you keep all the high pressure underneath the wing and don't let it get through to the top surface, you will very likely get a better climb, higher service ceiling, etc. But having the slotted aileron effect MAY have been an intentional design to keep the tips flying until after the root has stalled, per long-known principles. So of you don't add that higher energy air into the boundary layer (through the slot) at slow speed when you move an aileron down, you could have a very bad situation where the pilot is flying slowly near stall, he moves the stick to the right (for a right turn), and the left wingtip partially stalls. The pilot sees the plane rolling left and instinctively puts in more right aileron, making the left wing stall worse and a possible spin entry.

Enter the vortex generators. The VG's by definition are adding more high energy air (the little spinning vortices) into the boundary layer, delaying the stall and delivering other welcome benefits. If you close off the gaps AND put on the VG's, then the extra boundary layer energy is still put into the system (albeit from another source). So you COULD stand to see three benefits: Lower stall speed (as advertised by the VG company), better climb rate (because of the gap seals and the wing's new ability to remain efficient at high lift/AOA), and more solid control feel (as advertised by the VG company).

The only wild card is doing the gap seals without losing the proverse yaw effect. I have been thinking about how to accomplish this but I have not yet had the time to do it. I'll be glad to share my ideas, but in most cases I would like to be the Guinea Pig in case it doesn't work... and I haven't done the full gap seals yet.

In a previous discussion it was mentioned that aileron gap seals on a Taylorcraft reduce the roll rate. This is entirely possible. The VG's may or may not mitigate a loss of roll rate. It may be a small price to pay for the improvement, I just don't know.

If you are in the mood to tinker with something potentially cool, adjust your engine thrust line so it is pointing about two degrees upward, instead of level or a degree down. The Super Cub guys have been fooling with this and found that it decreases takeoff roll and improves climb.

Bill

[Ed O'Brien]

Re: L2 on Steroids

Tribe;
The 26 gallon (2-6 gallon orginal wing tanks, 2-6 gallon add-on STC'd wing tanks, and the preposturous 2 gallon header tank...
which is good only to header you to the scene of the forced landing in a field somewhere) is the way to go. I'll upgun the tanks one day. I'm out of money at the moment and will fly to little gatherings locally and $50 hamburger rendevous for the time being.

That's not a complaint... just an observation. With my L2A,
I fly LSA in a real plane and love love love the views. I open the two windows and watch the scenery move at a pokey pace and I think good thoughts while live a most happy life. For me the L2A is perfection. Not as perfect as my wife, grandkids, and dogs but right in there.

If you're ever in Denver please look me up and we'll go fly -- Oh by the way Lindberg flew the Atlantic at precisely the same speed and altitudes I fly everyday... so you can go places if time permits and you have a bit more tankage.
With regards;
Ed O'Brien

[flyguy]

Re: L2 on Steroids

Bill, I would like to see a photo of how to cover up the hole at the aileron push rod, if that is what you are talking about. I have looked at it with that in mind, but have not come up with any good ideas so far.
As for sealing the ailerons I think it is a probably a good idea for aircraft with 20 or 30 lb wing loading and dumb dumb ailerons, but Ole C.G. had this particular design pretty well figured out and I think I'll keep my boundary augmentation (I think that is what it is, perhaps not....LOL)
Darryl

[VictorBravo]

Re: L2 on Steroids

The "holes" I'm referring to are the big square cut-outs in the leading edge of the ailerons, where the hinges are and the control rod. It's a very simple flap made of plastic that simply covers that square cutout but allows the aileron leading edge to move downward "around" the plastic flap. Itis less complex and sophisticated than you probably are imagining.

There's also a way to seal around the aileron push-pull rod where it comes out of the wing, but I haven't done that yet either.

[VictorBravo]

Re: L2 on Steroids

The "holes" I'm referring to are the big square cut-outs in the leading edge of the ailerons, where the hinges are and the control rod. It's a very simple flap made of plastic that simply covers that square cutout but allows the aileron leading edge to move downward "around" the plastic flap. Itis less complex and sophisticated than you probably are imagining.

There's also a way to seal around the aileron push-pull rod where it comes out of the wing, but I haven't done that yet either.

The sealing of gaps worked very well on sailplanes of 5 to 11 pound wing loadings.

[flyguy]

Re: L2 on Steroids

Ok, I have the picture now. Piece of plastic on the underside that trails back from the wing structure and streamlines in the airflow. I would like to do the actuator rod hole, even more so than the others, as it seems the worst offender.
Gap sealing the entire aileron, in the end I guess, is just a matter of functional priorities.
DC

[Ragwing nut]

Re: L2 on Steroids

I followed John Collier's advice and put two 12 gallon wing tanks in my bosses L-2, it has the O-200, just got the wings on Friday, so it will still be awhile before the first flight, but I'd like to think 26 gal. should help some, O.T.

Any legality to this?

Mike

[Ed O'Brien]

Re: L2 on Steroids

There are STCs to do both the 0-200 and 12gallon wing tank -- in a L2 -- so are there legal issues? Yes! But, it's about getting the right STC, doing the work correctly, getting the inspection for compliance, and the paperwork properly filed with the FAA and all legal problems will be satisfied.
With regards;
ED OBRIEN

[VictorBravo]

Re: L2 on Steroids

Ok, I have the picture now. Piece of plastic on the underside that trails back from the wing structure and streamlines in the airflow. I would like to do the actuator rod hole, even more so than the others, as it seems the worst offender.
Gap sealing the entire aileron, in the end I guess, is just a matter of functional priorities.
DC

The actuator rod should not be a big issue once the air is stopped from coming up through the big square hole. (There's not a LOT of air coming into the inside of the wing, so there can't be that much coming out of that hole.

However, it is relatively easy to seal an actuator rod exit, so have at it if you like Here's a slightly less fancy version of how we did it way back in prehistoric times on the gliders:

Make a little cone out of thin "ripstop" fabric, about four or six inches high. The base of the cone should be a couple of inches larger than the hole in the wing where the rod comes out. Have your wife or someone sew the cone together securely.

Snip off the small end of the cone so you can slip it over the push-pull rod.

Clean the S**T out of the wing surface around the hole with rubbing alcohol.

Using small strips of strong carpet tape, put the strips around the perimeter of the hole in the wing. Cut four little slits around the base of the cone so the fabric will not wrinkle when you stretch it around the hole. When everything fits, peel off the second backing on the carpet tape strips and attach the base of the cone around the hole. Cover this joint with 3M "Blenderm" surgical tape for the best seal and security.

Use a wire tie to clamp the small end of the cone around the pushrod, wrap it with one layer of the Blenderm if you like.

Make a FULL and THOROUGH check of the control system to be absolutely sure that the seal does not interfere with any of the movement of parts of the aileron system. The cone has to still be "loose" t both ends of the aileron travel and CANNOT get into any bushings, bearings, bellcranks, etc.

The shape of the wingtip is one of the areas on T-crafts (any many other airplanes) that needs some serious attention, but that's another rant !