Discussion Ventus 2cx 6-meter Build

[GudmundT]

Hi guys,

I have just acquired a 6-meter Ventus 2cx from Icare to replace the 5-meter Ventus I lost earlier this year.

The Ventus, an HF model, is gorgeous, but I fully intend to incorporate some changes during the build.

Some of the "innovations" that I intend to think about incorporating are:

- no servos in the tail - this is in the search of lightness. I see no reason to add useless weight to compensate for servos in the tail. If the model needs ballasting to fly right, I will do that later.

- a split elevator - I am always concerned about losing an elevator on these models. Spitting the elevator and driving it with two servos may make me feel better (even if it doesn't accomplish anything else).

- fenders - both the tail wheel and the retractable main wheel need fenders to keep the grass and dirt out of the fuselage.

- instrument panel removal - I always remove the batteries from my models for charging, so I need an easy and quick way of accessing the space in the nose (the best place for battery weight). The three screws that hold the instrument panel in place will need to go.

- CF wing rods - the 123 gm steel rods that hold the tip panels onto the main panel will be replaced by 23 gm CF rods.

- retract doors - the problem with these scale gliders is that we don't land on scale grass. The consequence is that the doors for the undercarriage regularly get torn off. My intention is to find a way of preventing this from happening, either by bringing the doors inside the model, or by flipping them up against the bottom of the fuse.

- flap/aileron control - the earlier HF models had a difficult to setup, but nicely hidden, way of connecting the servos to the control surfaces. The one I have has been updated to a more straight forward, but less elegant direct system. I will want to hide most of these control rods.

- canopy release - one of the weak points of the model is the way the canopy latch is attached. This needs to be strengthened/solved.

- strobe light - I have always wanted to experiment with a nice bright strobe light to see if it could help with the "OMG I can't see my model" situations.

- a pilot needs to be added.

- the underside of the wings need to be darkened.

- a redundant (2.4G) receiver system needs to be installed.

- my Sky Assistant (a variometer and battery voltage monitor) needs to be installed.

Now, I will admit that some of these "innovations" may not pass the engineering phase causing them to be abandoned, but not likely very many of them.

I would, of course, greatly value advice from anyone that has attempted (whether successfully or not) any of these changes.

This process is not going to be a quick one, but I intend to keep this forum updated on my progress.

Wish me luck.


Gudmund
Keep your tow lines tight!

[egall232]

Gudmund,
Very nice look forward to your build log ,
cheers Euan.

[GudmundT]

Here are the weights of the various components of the Ventus:

Ventus 2cx

Fuselage
3,160
Rudder post
39
Rudder
120
Horizontal stabilizer
245
Right wing panel
1,780
Right wing tip panel
456
Left wing panel
1,798
Left wing tip panel
455
Wing tips
34
Wing rods
46
Hardware bag
77

Total grams
8,210

Sorry, I couldn't figure out how to insert a table.

Gudmund
Keep your tow lines tight!

[Lbuff1]

Hey Gudmund

I flew my Ventus again today and rung it out. With both 5 and 6 meter wind setups
The plane flies very well, you will probably want to ballast it up though. The Idea of the servos out of the tail is not a bad one, however, you will want some weight for get up and go.
The split elevator seems to be a ton of work and self defeating. If you intend to make the linkages go away, that may be short of a miracle with a split elevator. Just buy a real top quality servo. The two receiver is another interesting thought, With the JR system, I don't know what you fly, there are 2 ,3, and 4 receivers already onboard. with the little satellites.
I agree about the fender. If you mold one, keep me in mind. I will buy a copy. The latch on mine seems fine for the canopy. But I agree with you about the three screws in the panel. I inserted a bind plug receptacle in the panel.
You will want to order the multiplex connectors for the wing and fuse. It makes the setup at the field a piece of cake. Hobby lobby has some and so does Desert Aircraft.

Good luck with the build. I look forward to following along.

len

[ShredAir]

No servos in the tail AND a split elevator... that sounds like serious Klapperatismus (<-- German technical term). Have you figured out what the required linkages back there will weigh and how to minimize linkage slop?

Dieter Mahlein, ShredAir

[s2000]

Dieter is right, be very wary of trying to save 2 or 3 ounces in the tail of what is probably a 26 pound model, so you save 10 ounces overall but have even a small amount of slop or double neutral in the elevator. 2 or 3 pounds added or subtracted to this model won't make any difference in the way it flies, better to go with a tight elevator, you can do pull pull on the rudder no problem though.

[Harm]

Regarding the instrument panel, consider to connect it to the canopy. This way you can access the nose when the canopy is lifted.

[MTT]

I'll chime in here, too, Dieter and s2000 are absolutely right, on a 6m ship with t-tail, it's almost imperative to put the elevator servo(s) in the tail...

I always install the elevator servos in the tail, even in 1/4 scale ships such as my 3.75m Flair Ka8. In the case of the Ka8, installing a .80 oz HS-85MG in the tail requires only an additional 3 oz in the nose. Hardly worth mentioning in a ship with an AUW of 10lbs.

Like s2000 said, the added weight is insignificant, and is more than compensated by the direct, slop-free elevator actuation and ease of assembly at the field.
Plus, 2 pushrods running all the way back to the tail, and 2 bellcranks for the split elevators also weigh something....

Just thinking about installing 2 elevator pushrods in a 2m long fuselage, plus 2 bellcranks in the tail gives me the shivers....

[SteveR]

And now that the guys have convinced you to put the elevator servo in the tail, I'll offer my 2 cents and suggest you install it in the stab and skip the mechanical linkage when mounted in the fin.

Once you get over the horror of cutting a hole in the bottom of the stab to install it (concealed with servo cover, of course), you'll appreciate the very precise and super short linkage between the servo and the elevator as well as the ease of simply plugging in the servo when attaching the stab.

Steve

[SPasierb]

Congratulations on new new acquisition. Best wishes for many years of enjoyment! I've been searching for one in the secondary market -- hint, hint to anybody with a 6M cx or ax?!

We all have a desire to improve our models, but even with 29 years of sailplane flying experience, I can't tell you how much I've learned along the way from the sorts of Dieter, Tony, Len, Steve and others. Keep it simple, keep it strong.

Thanks for posting your build. Will be following closely.

Steve

[GudmundT]

Thanks for all of your thoughtful comments.

I do, however, have some experience with driving slop-free elevators from servos located in the nose of big models (Fox, Ventus, Super Dimona). I do not use a bell crank at all (which seems to be almost universally reviled) but rather a steel or "carbon" rod, held captive in a full-length sheath. The black Sullivan system is reasonable, but the only-to-be-found-in-Europe system is even better (it is a thin steel rod, encased in a plastic sheath, running inside of another, well-secured, plastic sheath).

My paranoia, with this build, can only be eliminated through the development and installation of a fully redundant flight control system. The front end of such a system is easy. Two batteries and two receivers, split the flaps and ailerons between the two and add the non-essentials (tow release, retract, etc.) to one or the other. The problem comes with the elevator (critical to most landings) and the rudder (less critical, but still handy to have).

Setting aside both the it-does-not-need-to-be-that-light argument and the be-careful-of-slop argument for a moment, the question comes down to - how do I provide the redundancy I want in the elevator? One solution, as I have already suggested, is to split it and drive the two halves with two servos connected to the two receivers. Another potential solution (and this only came to me on the bus ride home this evening) may be to leave the elevator in one piece, and drive it with two, independent elevator servos. I am imagining the servos being connected in series, not in parallel (if you know what I mean) so that with both operating full deflection will be available, but if only one is working then only half the deflection will be available. The engineering of such a system is challenging, but not overwhelming.

Then, if that is possible on the elevator, why not use the same approach with the rudder (who ever heard of splitting a rudder and driving it with two separate servos!!)?

So, what do you think?

Gudmund
Keep your tow lines tight!

[egall232]

Gudmund,
You like to make things complicated? i have used two servos to operate a single elevator one a L39 jet but mounted both in the stab and used separate rx channels via a matchbox ,of course the elevator surface was split in two.I watched a friends 40% Extra crash recently after one of the two servos on the ailerons siezed up ,he had a single control surface and the working servo could not power the aileron,
cheers Euan

[SteveR]

Gudmund, you can spend a lifetime worrying about all the zillions of things that can go possibly wrong with an RC sailplane. Statistically what fails most are batteries and switches. After that, just about anything's fair game.

If you're worried about the elevator servo, what about the tow release? What about the TX batteries? You can go on forever.

From my experience KISS rules the day: 2 RX batteries, 2 RX switches everything else is typical RC installation.

Since this is your hobby, go crazy and have fun building in as much redundancy as you can think of. At the end of the day, it's much more likely that something real simple will wreck havoc. And hopefully if all goes well, you'll have lots of flying fun before that happens. Keep in mind: they come in a box and go the same way.

Steve

[SteveR]

Only other recco: separate battery for the retract servo.

[Lbuff1]

Good elevator servo mounted in the tail. Rudder Pull Pull up front. Two Batteries for the receiver, one for the retract alone, and separate switches for all of them. Two receivers if you feel so inclined.

If something happens to the elevator servo and disaster strikes, Then you get to start a new project.
Don't make a career out of it, Just build it and fly the paint off it. You will love the way it flies.

Now go get building.


len