View Full Version : Pre-production Twinn-Rexx build pictures

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12-30-2007, 05:08 PM
So here's the plan:

1) As I have an early pre-production model, I need to replace the rear frames with new ones Joe provided which allow for the elevator servo to be mounted lower in the frame. This is to ensure the servo doesn't interfere with the body.

2) Replace the motor with a Just-Go-Fly JGF 500T 1950 KV Motor. The Medusa I have been using so far has plenty of power but gets too hot for my taste (way too hot to touch). When the body is on, there will be much less rotor-wash blowing over the motor so this is the time to make the change.

3) I've decided to keep the flight stabilization electronics. Although the heli flies great without it as well (see also other build/flight reports), and even though it adds cost, weight and complexity, I like the "gadget factor" and the fact that I can (or: dare to) fly in stronger winds than without it.
Actually, I'm going to add some more complexity (i.e. weight and cost :-) ). I've found a little device called "Equalizer II" which allows me to generate the DCP channel (which is 70% of the elevator channel) on the heli itself. This means that I can give the Spartan-RC unit control over both DCP *and* elevator (currently it only controls DCP). This will further improve the flight characteristics when I turn the stabilization gain on.

4) Install/paint the body. Still need to decide on a paint scheme. I'm considering the Canadian civilian scheme (attached).

12-30-2007, 05:28 PM
Looks like a neat bird . love the paint scheme ... but what did they do with the sponson of the Chinook ??? Am I seeing right or do I need new glasses ... but aren't they chopped off between the wheels ??

Am going to be interested in how the Equaliser ll works with all this setup you have.

12-30-2007, 06:06 PM
Guess they removed them. Interesting! Not a big deal as I'm into sport-scale... If we keep silent about it, I'm sure nobody will notice... :-)

12-30-2007, 06:10 PM
Perhaps I'll choose this scheme (see attached pic). Only thing is that I'll need Joe to provide a kit for the F16 then...

12-30-2007, 06:19 PM
And here's the wiring scheme (power-bus not indicated) showing how I plan to connect the EqualizerII in order to generate the DCP channel "after" the AP2000i. This effectively allows the stabilizer to control both the elevator and DCP.

12-30-2007, 06:22 PM
O.K. I won't tell any one ....whoops ... guess we just told millions ... Still love the paint scheme and I'm with you ,,I would do it ... I like it better than the normal military green and gray .
I actually am going to probably do mine in a sea knight color scheme ,,,just because I like it and it is different ... ;) :)

12-30-2007, 06:34 PM
I finally found the other paint scheme I like ...but darn it really is a CH-47 ;) :O

12-30-2007, 08:52 PM
What I like about the NAVY one is that it'll be easy to distinguish the nose from the tail when in flight...

12-30-2007, 08:58 PM
Yes and that will help I am sure ...
Found some more of the Columbia one that your looking at first ... it is really a unique bird ..with bubble pilot windows and yellow stripped blades .I am liking it better ..... darn it you got me looking through about 70 pages of airliners photos at Ch-47 paint schemes ;) ,,, as if you twisted my arm :)

12-30-2007, 11:14 PM
I believe that Columbia chinook had it's tanks (and apparently ramp, too) to save weight for logging use. Note the bubble windows so the pilots can get a better view slingloading.

I'm thinking CH-47D 91-00264, but she's got some personal signifigance to me. :)


12-31-2007, 08:38 AM
Yea 264 was awsome ... have you tried that with a pail or box duct taped to the floor yet !!!! I haven't but another guy I know has .... braver than me ;)

12-31-2007, 04:59 PM
No mini buildings ... yet. The closest I've come is trying for a small piece of 1/2" plywood that was laying on the floor.

01-01-2008, 08:05 PM
I believe that Columbia chinook had it's tanks (and apparently ramp, too) to save weight for logging use. Note the bubble windows so the pilots can get a better view slingloading.

I'm thinking CH-47D 91-00264, but she's got some personal signifigance to me. :)


Bubble windows? Do you mean the ones in middle of the fuselage? That's hardly a flight position. It's to allow a flight engineer to clear the aircraft.

01-01-2008, 08:47 PM
Nope ... pilot bubble windows ,, remember this is a civilian work horse --- not military ...so anything goes....

You should be able to click on the pictures and make them bigger ... unless your browser is not set up for it .

01-01-2008, 11:18 PM
Bubble windows? Do you mean the ones in middle of the fuselage? That's hardly a flight position. It's to allow a flight engineer to clear the aircraft.

I know ... I've broken a half-dozen with my thick noggin. :D I keep forgetting how big my head is with a flight helmet on. ;)

01-03-2008, 03:43 AM
Short update. I've now installed the new rear frames in order to relocate the elevator servo. I've also finshed the body prep (cutting the body halves, tower holes, battery access holes and landing gear holes; drilled the body mounting holes; attached the body joining tabs, etc.). Picture 1 shows the heli suspended for test fitting purposes.

The body halves are now almost ready for priming. I've decided I want to keep the windows transparent so I've masked them using liquid masking tape (made a window template from scrap lexan first). See picture 2. This -of course- needs to be done before priming. Note that the heli will be loosely based on the Columbia helicopters one.

I plan to make the windows semi-transparent using "transparent black window tint" spray paint which will be applied on the inside of the fuse. Picture 3 shows the body ready for this inside paint application. Note that I masked everything but the window areas as I don't want overspray everywhere inside the fuse.

This is the first time I'm spray painting a fuse. Lots to learn here... :)

01-04-2008, 06:25 AM
Anyone can sugggest any source for replacement of the 4 bevel gears ?


01-04-2008, 01:36 PM
Miter gears are here




01-04-2008, 03:11 PM
That was going to be pretty much my reply Joe.... never ,,,never put anything but what the company supplies on something this complicated ,,, unless you happen to be an aeronuatical engineer . Chances are they have done the research and know which hold up the best ,,,, and besides trying to find an exact fitting match would be 1 in 1000 chances ... if you haven't ever looked for gears you don't know what a pain it is ... I had a company build gears for my V-22 project because no one in the world made exactly what I needed to make it work ... and believe you me it cost too.

01-05-2008, 08:02 PM
Thanks, Joe

I cannot see that a week ago! I have to re-order then.

01-09-2008, 02:36 AM
Time for an update. Progress has been a little slow, but the body halves have now been primed and painted white. See the attached picture. Note that the windows are still masked off using liquid mask film as the red stripe still needs to go on. My experience with spraypainting (this is the first time I'm painting a fuse) is that it's easy to get a *pretty good* result. At the same time however, it seems very difficult to get a *truely great* result... On close inspection you can certainly see some imperfections, but overall I'm pretty happy with my efforts so far. :smokin:
Note that I can highly recommend the instruction DVDs from JMD models available at: http://www.jmdmodels.com/index11.htm. The techniques described in the video have helped me a great deal. :thumbup:

On the heli itself, I've now installed the Equalizer II (see earlier post). This means I'm "generating" the DCP channel "onboard" now (rather than in the transmitter) giving the stabilizer control (dependent on the gain setting) over both DCP and elevator channels. It works great on the bench but I haven't been able to test-fly it yet. An added bonus is that this frees up a channel on the transmitter (down to using 6 channels out of 7 now) which could be used for gyro gain in case I'll try a 401 on the rudder sometime in the future (or other gadgets of course... :D).

Another plan going forward is to install 3-bladed heads. I've ordered them from Flying-Hobby: http://flying-hobby.com/catalog/product_info.php?cPath=3_27_53&products_id=1528. :YeaBaby: I figure that with all those stabilization gadgets, I might as well challenge them a bit... :wink:

Question: any recommendation which blades to use for 3-bladed heads? Can I simply add two of the same blades (after balancing of course) or should I go for ones with a smaller chord?

01-09-2008, 06:22 AM
Looks good for a first timer :noteworthy .. I would hate to show my first one :wink:

On another forum a guy flies Trex multi heads all the time and he uses the Trex 325 's on most of his ..I would be tempted to use maybe 315's or so ...but I think the JGF 500 will handle them just fine ,and if you are like me probably have some orphan ones laying around :o:roll:

01-09-2008, 01:45 PM
Gra55h0pper, I love the three blade heads! I haven't read this whole thread, is Joe on board with those heads for the Trexx? Or are you forging out on your own with them?

I own the CH-46 with the 3 blade head from mscomposit and it is twitchy, very tough to fly that heli. It will be interesting to see how that setup works on the REXX. I expect the REXX will be much better to fly with the superior electronics and design over the micro CH-46.

Anyway I am sure you will keep us posted.

I also hate having the spare channel just spitting out a gain, seems a waste. I will read into your onboard processor approach, sounds very interesting. I would like to go with a 401 on the rudder in the future as well.

01-09-2008, 05:55 PM
As far as I know Joe is looking at different types of heads .. The last I heard he had some of the china ones . Personally I don't like them ... I have one that I bought used and it is very twitchy ,, even with gyros on a mechanicall mixed rex I have . These from china are non flexing (rigid rotors ) The only flapping or flexing you get is what little the blade does itself .

What I have read on other forums tell me that a semi rigid head or articulate head are better ...as they tend to allow the bird a little gyro effect even though it doesn't have the flybar there ... but there is only one manufacture of these type that I know of now ,, and they are really expensive and who knows how long they will produce parts for it as it is just a modeler that did this on his own . I want a company that is going to be around for awhile ,,,cause I plan on keeping this bird for a little while :thumbup:

I am waiting to spend the money until I see what Align brings out or Joe and from what little I have flown multi heads ... I hope that it is a articulated head .

01-09-2008, 07:00 PM
We are currently working on our own 3-blade head design. It is articulated and has dampers.

We hope to have a flying prototype ready in a few weeks. As before, progress will be documented on the Twinn Rexx development page. Stay tuned.