acrojack202

After 30+ years of RC, I decided I needed to build at least one twin. Most of my flying has been focused on pattern competition, with a good number of sport planes as well. Lately, I've been intrigued by float planes, so I decided a twin engined float plane would be just the ticket. Probably not one of my smarter decisions.

Nonetheless, I purchased a G&P Canadair CL-215 kit and am well into the construction. While I'm making a signficant number of changes in the construction methods, I'm not altering any of the basic design parameters. I am using engines that are larger than those used originally - I believe they were .46 2-strokes and I'm using Saito .82 4-strokes. A liitle heavier for sure, but I'm flying off a lake at 6,000 ft elevation and need the power.

If anyone has built this model, and has advice on the construction or flying, I'd appreciate your input.


Acrojack

William Robison

My Feedback: (3)

Jack:

You are not learning one new trick, you're trying to learn two tricks at the same time.

If that plane has provision for wheels, get its flight characteristics sorted out dry, then when you're comfortable with it put it in the water.

If that's not practical just make sure your engines are dead reliable, with both running it wont be any amount different from flying a single.

Personally I'd jump into one, then the other, combine them later.

Bill.

acrojack202

Bill,

I hadn't planned to add functional wheels, mostly because I'm concerned about weight. but I'm rethinking that now. Been woking on the wing and nacelles so I really haven't gotten to that decision point. Another few weeks to decide.

I will definitely run the engines in thoroughly before I put that bird up over water. I have an old trainer test bed plane to get a few hours on the engines. I've had good luck with the Saito 72, so I'm assuming the 82's will be similar. We'll see.

Jack

BillS

In my opinion Bill is correct in the caution about ‘two tricks’ at the same time. Working on two complete unknowns at the same time likely reduces the probably of success by a factor of ten. Good designers don’t knowingly invite Murphy’s Law to the party. Enough stuff will go wrong all by itself.

Bill S

twinman

My Feedback: (2)

While I have flown single engine plane off the water...( Ok, before I saw the "LIGHT OF TWINS") and found them somewhat twitchy on roll out. Normally different throttle up characteristics with a land based tricycle gear are really not a big deal. It gets worse with a tail dragger and on water, wild and possible flip.
Some possible aids or first flight thoughts. 1. Have an assistant hold the plane as you accellerate the engines to full power and let go for the first flight. At least it will start straight. 2. If you have a computer radio, consider to use the various control curves to "Map" one enigne throttle up to the other. The engines need to come up much closer than normal to hold the plane in line. 3. Make sure you have a good and effective water rudder. 4. Consider a gyro on the rudder to aid in a straight roll out ( I wonder if "float out" applies here). 5. Yes, you can mix the engines to the rudder, but on land, I have found this dangerous unless the mix comes in above 50% throttle, and then it works well. 6. As an experiement for hovering, I installed a Hobbico Aero gyro between the reciever and the separate channels of the two engines. It did work and MIGHT ( I say might as I personally have not tried this) work here to aid holding the plane straight on take off.
It is obvious that you are an experience pilot, but I must ask,,,do you ALWAYS fly with the rudder and ailerons used together? If not, LEARN NOW OR DO NOT DO THIS.
Keep us posted.
Twinman
PS Pictures??

acrojack202

Twinman,

Thanks for input, a lot of food for thought.

Yes, a launch helper for sure, maybe two. I'll be using a JR 10X radio so I have lots of channels and mixing capability. I'm planning 2 servos each for the ailerons, flaps and throttles, one for the elevator and rudder. And possibly one for a water drop, not sure about that. If I do decide on wheels, I'll used a fixed arangement for land and remove it for the water.

The gyro is an interesting idea. I've never used one but I can see the value with a twin. I'd be a little leery about mixing throttle onto rudder, at least until I really understood the torque reactions and had a lot of confidence in the engine's response to throttle. I like the gyro approach better.

I'm not sure I understood your comment regarding using aileron and rudder together - did you mean to get a coordinated turn? Its true, most of the time we turn with aileron and elevator, not worrying about keeping the ball centered. The 10X allows you to couple the rudder to aileron with the flip of a switch - I'll make it a point to use it.

The CL-215 has a flat wing, no dihedral, and a very large and tall vertical stab and rudder. Makes me wonder what the roll coupling will be, probably pretty significant. All the more reason to employ the automatic rudder/aileron mix.

One question about throttle control - do you set up your system so you have differential throttle control during flight? Or just rely on the preset mapping of one channel onto the other? It'd be easy to do that, in fact I think I'll get thet capability automatically if I use the correct channels, just wondering if its of practical use.

Jack

twinman

My Feedback: (2)

On the engine mapping, yes it works all the time.
The rudder mixing is definately used in flight at all times for more aerobatics, but not below 50% throttle for safety on the ground.
The gyro on the rudder as a minimum with help with take off and more so if it is connected to the water rudder.
The gyro in the engines did work, but I have never tried it in this application. I was after hovering control with the rudder out of direct prop blast.
On the use of the rudder in turns. Sorry, I am NOT suggesting an electronic mix to ailerons. I am suggesting strongly that you fly with the rudder input all the times and on every turn. No, it has nothing to do with a beautiful turn, but being able to AUTOMATICALLY contol the plane with an engine out.
Good Luck and keep us posted.
Twinman

acrojack202

mk

Paternguy

My Feedback: (1)

I would play with a Duelest 2/40 before making the leap into scale twins. You will find that it flys alot like an older pattern plane and will help you with the quirks of a twin.

acrojack202

Well, after only seven months, this project is coming to fruition. Seems this Canadair has been hanging around my workshop forever. It may actually die of hangar rash before I ever get it in the air. Actually, its been a fun and learning project. Lots of room for creativity in this aircraft. It didn't really take seven months of work - I built a couple other planes in parallel, but there are quite a few hours invested here. Got the kit from G&P as a Christmas present from my son and my goal was to have it ready for our local "Float Fly" in August and I think I'll make it. I hope to do the test flights next week

I would love to hear from anyone who has experience with this plane. I have made a few changes; most notably bigger engines. The kit has been aound for quite a while and was designed around .40-.46 2-strokes and I'm using Saito 82 4-strokes. Considerably more power but also more weight. All up weight, less fuel, is 13 lbs. With 870 sq in of wing area, thats about 35 oz/ sq ft. Not exactly a glider. Especially when the lake is at 6000 ft elevation and the temp is likely to 90F.

I'm a bit concerned about the CG location. Plans call for a CG at 35% MAC. That sounds like it could be a little squirrelly to me. The plane has a huge vertical stab and rudder and a lare elevator which puts a lot of weight in the rear. I probably aggrevated matters by glassing and painting everything rather than using Monokote. Anyway, to get the CG at 30% MAC I'll need to add nearly a pound to the nose. 37 oz/ sq ft ??? Wonder if it'll get off the water at that weight? We'll see.

Sure would like to hear from someone who's built and flown this plane.

Jack




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