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-   -   Lazy Ace Biplane build from coroplast (http://www.rcuniverse.com/forum/scratch-building-aircraft-design-3d-cad-174/11641617-lazy-ace-biplane-build-coroplast.html)

Joystick TX 09-12-2017 07:17 AM

Lazy Ace Biplane build from coroplast
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I have always liked the looks of Chuck Cunningham's Lazy Ace biplane.

Since I don't have a biplane, it seems like that will be a good one to add to my fleet.

It took me five years to build the Bell Hop/Faux Cat from scratch and I don't like the idea of painting or covering a plane, so I decided to make the 76" plane from coroplast.

Joystick TX 09-16-2017 03:21 AM

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Getting closer to the coroplast "covering" point.

It sure takes a lot of time, work, and decisions to just get this far.

The wings weighed in at 2lbs 12oz at this point.

The fuselage weighed in at 2lbs 14oz. Of course after the engine, wheels, bracing, etc. get added that weight may quadruple.

Joystick TX 09-16-2017 07:04 AM

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Just finished setting up the engine mount. I always hate figuring out how much correction I need to line up the prop C/L to compensate for right and down thrust.

Seems like the muffler will be pretty close to the side of the cowl. I don't think that will be a big problem, it should just melt the coroplast and let me know where to put a bulge in the cowling so it has plenty of clearance. I'm pretty sure that's how real planes are designed.

Joystick TX 09-23-2017 03:59 PM

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Got the holes in the tail of the fuselage drilled for the rods. Had to make a jig to get the drill to line up correctly. The right and left stab halves will slide over them and be held in place by the flying wires.

I don't trust the use of flashing and CA to hold the plane together under the pounding of a 30cc gas engine, so there will be a few Chicago screws used to hold critical parts together. I also have some good large-head wood screws to use to hold the coroplast on the fuselage mostly around the firewall and on the wing ribs.

The wing ribs and "I" beam seems pretty rigid. I did add a center rib to the top wing because I'm going to need it to support a seam on the top. I was going to make the top and bottom using single pieces of coroplast, but that will be too hard to glue and hold. Two three foot sections will be much easier.

Found some really neat little clamps at Harbor Freight for a good price.

Joystick TX 09-30-2017 06:44 PM

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Got quite a bit done since the last post.

I need to put the coroplast on the wings yet. When they are finished they will weigh about 4 lbs each.

The fuselage is finished, just need to mount the engine. It weighs 7 lbs as shown in the picture without the engine. The engine weighs 3 lbs 12 oz.

Looks like the final weight will be right at 19 lbs.

Propworn 10-01-2017 12:48 PM

19 Lbs for a design that should weight in at 10 to 12 lbs. Heck even on floats I don't think its much more than 14 lbs. I bashed mine into a trimotor with 3 .60 OS and it was up near 17 lbs tons of power. With all that weight it flew like a dog compared to how the original flew. Good luck.


Joystick TX 10-01-2017 01:52 PM

Originally Posted by Propworn (Post 12372219)
19 Lbs for a design that should weight in at 10 to 12 lbs. Heck even on floats I don't think its much more than 14 lbs. I bashed mine into a trimotor with 3 .60 OS and it was up near 17 lbs tons of power. With all that weight it flew like a dog compared to how the original flew. Good luck.


I'm not looking for a floater, or a 3-D aircraft. I need something heavy that will fight winds.This plane will have more drag, but my GSS at 14 lbs has 1.559 lbs sq ft of wing loading and this one at 19 lbs will have 1.583 lbs sq ft so it should not be too bad. That's not even counting the the area of the "lifting stab." The power for both planes will be the same sized 30cc engine.

I may also need to add a couple of pounds of lead to the nose, like most of the warbirds.

I'm also playing with the idea of putting 2 or 3 degrees of down incidence in the top wing to help with the slow speed handling. It could use that since the top and bottom wing are the same size and not tapered or swept back. I'll see what happens after the maiden flight.

Propworn 10-02-2017 12:29 PM

Even the 10 lb version has no problem in a strong wind. Even off water

Rodney 10-08-2017 05:37 AM

I've built two of the Lazy Ace's, both flew very well. Had a Quadra (a 45cc if I remember correctly) on one, a 1.20 glow on the other. Both seemed to have plenty of power. Coincidently, that Quadra alone weighed 7.5 pounds so I did build a much stronger wheel mount out of 1/4 inch music wire with appropriate structure beef up. Had to set the firewall back about 1.5 inches with the big Quadra. Both planes flew best with the upper wing 1.5 degrees LESS angle of attack than the lower wing. Both required about 1.5 degrees down thrust and about the same right thrust.

Propworn 10-08-2017 10:48 AM

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First Lazy Ace pics one through 3
One Glider tug
Two float plane
Three spreading the ashes of a good friend and modeler over the flying field.

Lazy Ace Two
Four is also a glider tug
Five is as a tri-motor

Joystick TX 10-16-2017 01:44 AM

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I got the top wing skin size, slots, and aileron hinging figured out.

I drew it up full size used a piece of scrap and cut out flutes in the bottom of the wing skin so it would be flexible enough to make the bends and for the location of the flute on top to make the hinge.

Now all I need to do is transfer these cuts to the top skins and glue them on.

Joystick TX 10-16-2017 10:40 AM

Originally Posted by Propworn (Post 12372412)
Even the 10 lb version has no problem in a strong wind. Even off water

Regular winds don't bother me. I want a plane that can handle 10 to 15 mph crosswinds. My light planes don't do so well in those.
Looks like you have a great fleet of bipes. I don't have the patience to build anymore.

Joystick TX 10-16-2017 10:41 AM

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Almost have the bottom wing finished. Just need to install the servos and control horns.

It is the hardest to build and also the heaviest since it has dihedral and the ailerons. The Chicago screws should work well to keep the wing together under the vibration of the gas engine. Time will tell. Like the first flight.

The weight is right at 4 lbs. Not too bad for a 6 square foot wing.

Time for a nap, then I'll get started on the top wing. I have the coroplast sheets cut already, just need to glue them to the ribs.

Joystick TX 10-17-2017 12:17 PM

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90% done.

Needs some work on the CG.

Joystick TX 10-19-2017 03:07 PM

Hey Propworm, have you experimented with moving the CG back past the 5" point on the top wing?

Seems like with a lifting tail, it could go well past that point.

My engine is pretty light and the coroplast is pretty heavy, so I need to take a lot of weight out of the tail, put weight in the nose, or reduce the top wing stagger to get the CG at the design location.

Propworn 10-19-2017 04:13 PM

Towing gliders, spreading ashes where the weight is all 6 inches above the top wing I imagine the CofG got shifted all over the place. Your right about the lifting tail allowing the model to be more forgiving as to the CofG. I even had a glider get hung up on the cradle crosswise and had no problem controlling the model all the way back to the field. That being said I increased the size of the rudder about 40% and the elevator 30%. Look at the third picture the yellow one with the glider on top and you will notice the increased rudder area.


Rodney 10-20-2017 06:53 AM

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Hopefully, I managed to post a picture of my last Phaeton

Joystick TX 10-27-2017 05:04 AM

Wow, that Phaeton should do well with a 72cc engine.

Here was a helpful site that I used a lot: 8 Ft Wingspan Coroplast RC Piper Cub Flown by 25cc Weed Trimmer: 27 Steps (with Pictures)

I have the bottom wing incidence adjusted. Now all I need to do is remount the top wing with no stagger. That will put the CG at the right point without adding any more weight.

The weight is 17 lbs, which makes the wing loading a little less than the 8' Coroplast Cub in the article above.

Joystick TX 10-30-2017 10:32 AM

Maiden Flight
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Flew the maiden flight this morning, Oct 30, 2017.

The plane surprised me by taking off in about 3 seconds. It has plenty of power, it will fly at throttle with no problems at all.

It did require about six clicks of down trim.

Loops, rolls, etc. are slow and graceful.

Landing is a breeze, it comes in like it’s on rails. Just needs a little up elevator to flare for a walking speed touchdown.

No bad habits.

Joystick TX 10-31-2017 06:22 PM

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Added "bug-out" handle and some trim.

Joystick TX 11-01-2017 04:42 AM

Final thoughts:

Chuck Cunningham did a great job of designing this plane.

The plane flys great even though I had to do some "bashing" to get the CG correct. I really hate to add weight to an airplane to make it balance correctly and none was required for this one.

Coroplast weighs over 2 oz per square foot which makes the tail really heavy compared to the normal materials used for model planes.

I don't have the manual dexterity to deal with a bunch of 4-40 bolts and nuts to mount the wings and rigging, so the bottom wing is held on with four 3" x 1/4" nylon bolts. The top wing is held on by four 3/4" x 1/4 nylon bolts. The cabane struts are held on by eight 3/4" by 1/4" nylon bolts. The two interplane struts, one on the right and one on the left, are held on by two 3/4" x 1/4" nylon bolts, one for the top wing and one for the bottom wing. Yes, I did buy the 3/4" bolts by the bag of 100. I have holes for the rear interplane struts, but since the Coroplast wing is so rigid, I don't use them. Wing mounting at the field is quick and easy.

The major change, which also affects the looks, was to move the top wing back four inches to get the CG on the right spot. One thing that is interesting is that there is no CG change with the top wing on or off. I could fly it as a monoplane, or a bipe. Of course the wing loading would be pretty high without the top wing. I may try it later just for kicks.

The other change, which is minor, was to add about 3 degrees of down incidence to the top wing. That was to help with the slow speed flight. The top wing will stall shortly after the bottom wing. Since there is no sweep to the top wing and no stagger, I felt that it would be wise to make that change to prevent a wing drop at low speed.

I was a little concerned about the "lifting tail" design and saw that some of the people who built the plane decided to just use a flat stab or a symmetrical airfoil. The choice does affect how the plane will behave with throttle changes. I put in about 2 degrees of right engine thrust and 3 degrees of down thrust. With that set-up, as I added throttle the plane did not climb at all since the tail provides more lift which keeps the nose from pitching up. With two huge Clark Y airfoils they would provide a lot of lift as the airspeed increases, so Chuck made a good design decision to have the tail airfoil so some lifting to keep the plane from pitching up too much as the speed increased. I don't need any trim changes from 1/4 to full throttle. I could have used a little less down thrust on the engine to make the plane fly more like a real plane.

There is a lot of drag with this design, so there is not much change in speed from 1/4 to full throttle, and just noise change from 50% to full throttle. The plane is "lazy" in the air, it just seems to float along. It looks very realistic.

Takeoffs are a little tricky due to the short fuselage. Slow throttle inputs and fast rudder inputs are required to keep the plane straight until a little speed is built up. I think that may be why some people have increased the size of the moveable portion of the rudder. I added 1/2", it could probably use a little more. I also took out all the rudder expo that I had initially. The plane will be airborne before you know it.

Landings are great, the plane comes in like it's on rails. Due to the weight, a little up elevator, to stop the sink rate, is required a little earlier than I'm used to. I'll get the hand of it after a few touch and goes.

If I were to build another one out of Coroplast, I'd lengthen the nose a couple of inches and leave the wing stagger alone unless it needs to be moved to change the CG.

Joystick TX 11-02-2017 01:34 PM

Some people have asked how long it took to build this plane.

I started it on Sep 12 and finished on Oct 30, so about 49 days.

So far, I spent about 150 hours on it, but it seems like a lot more than that.

I'm still doing little things to it, mostly trim, tweaking controls, etc.

Joystick TX 11-03-2017 10:04 AM

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Got another four flights on the plane this morning.

Takeoffs are a lot easier now that I removed all of the expo from the rudder. It allows me to make corrections a lot quicker. All the takeoffs were straight as an arrow.

It really did well in the crosswinds today.

Had three dead sticks today. Time to replace that old engine, I'm tired of messing with it. Got a new DLE-35ra to put in it.

Latest picture of the plane with some decals and trim.

Joystick TX 11-04-2017 04:12 PM

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Got the DLE-35ra engine mounted and did the first run.

This is the most well-behaved engine I've ever seen. This one is #5 for me and they all ran great.

The engine was pretty "dry", and rough to turn, it felt like bad bearings. I added about six drops of oil to the cylinder with the plug out. Spun it for a few seconds with the electric starter. It loosened up okay.

Changed the plug to the CM-6. Will use the DLE plug for a fishing weight as usual.

Checked the timing before the run and it was set at 35 Deg BTDC, I don't like that much advance, so I set it to 30 D BTDC. The 46 Deg BTDC in the manual is a joke. I would like to see the video of them doing it. I set the H and L needles for 1.5 turns.

For the first start, I primed the carb with a few drops of fuel, then hand flipped the prop a few times with the ignition OFF, switched it ON and the engine started with four flips of the prop. I ran it for 10 min., mostly at the mid range and it never died even at a pretty low idle.

I'll do two more 10 min. engine runs, then adjust the carb and fly. Monday looks like a good day.

Something struck me the other day when I was bolting on the wings. Since there is no stagger between the top and bottom wing, this plane will not have a CG change if it is flown with the top wing off. Same with the bottom wing.

Later, after I'm used to the plane and the new plane smell is gone I'll try flying it as a low-wing monoplane, then as a parasol wing style plane. I'll need to see if the plane can turn without ailerons first since the top wing doesn't have them.

Joystick TX 11-06-2017 08:15 PM

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Got six more flights on the new plane and engine today.

Performance is great. It takes off in about 30 feet and has almost unlimited vertical.

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