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Sep 15, 2014, 10:22 AM
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bozodude's Avatar
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Sep 15, 2014, 10:40 AM
Can't fly 3D for toffee ...
GoAround's Avatar
Originally Posted by bozodude
I suggest not to adjust the horizontal as in video. Change can be made by removing the tape just forward of tail, and SLIGHTLY bend the fuse, release and re-tape. Unlikely, but if bigger adjustment is needed, the fuselage gap can be shimmed or cut.
Originally Posted by Jovanx
I cut with the tip of a sharp knife and then pulled bits of foam out with tweezers. You only get about 1/4" and then you break free into the hollow part of the fuselage. There is a foam lug on one side that prevents the battery from slipping back too far.
Originally Posted by malapardis
I've only read about decalage problems with the big Radians. Can you point me toward any info about people having modified the baby Rad's decalage? It'd be pretty easy to do with a little shimming in the tail boom, but I'm no expert on this matter and I'm looking for more experienced flyers & modders to weigh in.
These posts inspired me to sort out my porpoising so I cut out 5mm of foam. I then cut the rear fuselage tapes, shimmed the top gap with a 1mm width bit of CF strip and retaped. Hand chuck OK so took it to a small local bit of grass.

It was a bit too windy for the baby Radian, or so I thought but I was wrong. It was fantastic! After a bit of messing around low down, I took it higher and found a thermal. The rest of the flight was spent thermalling downwind till I was worried I'd lose orientation then high speed flying back into wind to pick up another thermal. It was so much fun. After 16 minutes total (2 minutes engine at the start), I dived it down and landed as I have no real idea how long the battery would do. I'll charge and see what I used.

I'm so happy with the flight, I've forgotten to write about the porpoising! Anyway, it was slightly evident but much reduced. This was the stock battery and my other ones (190s) are heavier so I'll trim another mm or so out before the next flight.

I love this model. It's the only micro I have zero regrets about buying. I love my Sbach 3D, Stryker 180 and UMX T28D but I never really fly them as I always take Twisted Hobbys stuff to the park. However, this little Radian is unique and can allow me to soar in places I wouldn't dream of taking the big one to.

I'm seriously wondering about buying a second to store away in case anything happens to mine ....
Sep 15, 2014, 11:18 AM
I meant to do that....
crashnburned's Avatar
GoAround, after your mods, did you leave the CG stock or did you move it back at all ?
Sep 15, 2014, 12:42 PM
pull up -- PULL UP!!!
Originally Posted by GoAround
These posts inspired me to sort out my porpoising so I cut out 5mm of foam. I then cut the rear fuselage tapes, shimmed the top gap with a 1mm width bit of CF strip and retaped.
Afraid that all left me a little confused. You cut out 5mm of foam from where? The back wall of the battery tray?

Did you just make an arbitrary change to the decalage with the 1mm insert, or did you measure the difference angle, before and after?
Sep 15, 2014, 12:42 PM
Registered User
bozodude's Avatar
Glad it worked out for you. This mod isnt for everybody. Most are perfect out of the box. But if left in the car and had some sun/heat and just doesnt balance properly anymore, and no amount of battery shift corrects it, you might need the mod. If your plane glides in calm air straight and almost level with no pitching, and your elevator is at neutral, dont touch a thing! make registration marks on wing, fuse, and battery.
Sep 15, 2014, 01:04 PM
Simple, Easy, Fun
Gabe_BigApple's Avatar
Originally Posted by bozodude
Glad it worked out for you. This mod isnt for everybody. Most are perfect out of the box.
Mine was fine out of the box, too.

I'm wondering about other factors may account for the variation in performance.

There are a lot of parameters that come into play when manufacturing foam sheet, and there might be minute differences in the weight of the horizontal stabilizer of some planes.

Since the solution here is shifting a 5 gr battery located close to the CG (very short moment arm) it indicates that the problem is very small.

It seems possible that a miniscule change in the weight of the H stab, combined with a very long moment arm could well have about the same sort of effect, and that this is what the rear location of the battery compensates for.

Sep 15, 2014, 01:50 PM
Mr. Magoo's Co-Pilot
GRUMPEE's Avatar
Mine would porpoise as soon as I let off the throttle....duh splapping my head, I had mounted the wings backwards. All fine now
Sep 15, 2014, 02:52 PM
Registered User
Mine has always porpoised, from Day One. Since it was my first plane, I didn't know at first that it was a problem!
Sep 15, 2014, 04:13 PM
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Brown Shoe's Avatar
I will try cutting the hole and moving the battery back as far as possible to see if it cures my porpoise problem. As previously stated, it does not matter what I do, mine will porpoise an porpoise and porpoise. It is not fun to fly at all and I'm very disappointed. I thought about buying a second one and using "Flipper" for spare parts, but I don't want to end up with another fish!

Sep 15, 2014, 05:40 PM
Registered User


boys, some posts ago i commented on this problem, as i was facing same situation, and it was not until i changed the stabilizer incidence that i could solve it. (the so-called 'decalage')
it is not a matter of playing with elevator trim or shifting cg.
i may try to rescue those posts where it was detailed (or some1 can help bringing those comments here).
i wish could be a 1st post with an index so this and many other issues could be presented so there is no need to explain everything over and over.
but as it is, we can bring it again. no problem.
Sep 15, 2014, 05:45 PM
Registered User

more on decalage

found this: (posts 3168/9/70, page 212)
Originally Posted by phil alvirez
no matter how many packs you try, if decalage is wrong and you don't correct it, there is no way to fix the problem. i had 1 with that and could do nothing until fixed it. it is not anything wrong with the design, it is your specific model. am talking based on personal experience and not on guessing.
Originally Posted by electrich
I agree with Phil. While the foam technology has come a long way, it is still soft and subject to "bad memory" due to how the plane is stored or even how the tail was taped in place - and it will effect your flights. After my dog ripped the stab off mine and I repaired it the porpoising was a problem. It wasn't an issue previously. I bent the fuse/tail joint slightly to give me some more "down" in the stab and then retaped it. Good as new.
Yep. Reduce decalage. Just cut tape and retape. So the stab produces less down force, so the plane flys more nose down. I had to do it on mine and now it flies great. I also had to cut the battery compartment to get a more rearward placement but I usually push the CG to max rearward on my gliders, just shy of unflyable instability. Floats like a dream
Last edited by phil alvirez; Sep 15, 2014 at 05:57 PM.
Sep 15, 2014, 06:07 PM
Registered User

found it

changing decalage
post 1583/page 106
Originally Posted by RealGambler View Post
My bird fly fine, but I'm curious, how do you did all the corrections? From 0 to too much, back to somewhere in between, without damaging the aircraft?
the fuselage is made of 3 pieces: bottom, top and rear. they are attached with clear tape. where the rear matches the top, i lifted the tape and initially sliced and removed a paper-thin vertical section in order to increase the stab incidence, then pushing the rear section to fill-in the space and pressing the tape in place . as it was too much, now i inserted a piece of about half the original thickness and sealed the parts with the tape. this way, the amount is half the 1 it had before. i hope this will give the needed decalage. this is a critical dimension.
by carefully lifting the tape there is not much damage to the adhesive and it sticks again sealing the parts together. the point is in dealing with small dimensions, where you have to be very precise.
i don't like to call this easy or difficult, it's just a matter of doing it carefully and taking your time. after all, time does not count. the results do.
Sep 15, 2014, 06:08 PM
The "Foaminator"
mikeruth's Avatar

Motor/gearbox removal

Welll I asked this on another thread some time ago and got ZIP, Nadda.
My first UMX radion is flat worn out and beat up Enjoyed the heck out of it.
Now the second one is in service and this one needs service

My motor/gearbox is really glued in. But of course the brick has popped loose.

Any good tips suggestions on getting it free with out damaging the foam?

Thx as always guys.

Mike R
Sep 15, 2014, 06:09 PM
Registered User

post 1577

and how it started:
decalage and trim
after been able to fly my plane several times, i noticed that to fly and glide without stalling, i had to feed full trim down, and the elevator sits at about 3/32" down, so it was telling me that it had too much decalage (angular difference between wing and stab) , so i measured it again: i had it at -2 degrees (2mm), so i changed it to -1mm .
the cell had to sit full forward, otherwise it stalled wildly no matter what.
another thing i noticed was that if flies fast, and if i try to stall it at the moment of catching it, it does just a snap and falls, not a gentle stall as expected, so it confirms that something was not right.
whenever the weather allows me to try this, i will see and tell here.

just in case this is of any help to some1 that has similar problem (my plane came with zero wing-stab incidence (decalage).
Sep 15, 2014, 06:12 PM
Can't fly 3D for toffee ...
GoAround's Avatar
OK, to clear up the confusion about what I did:

1) I removed 5mm of foam at the rear of the battery bay so the lipo can sit 5mm more to the rear
2) I removed the tape that holds the rear of the fuselage on
3) I inserted a 1mm shim in the gap made by cutting the tape on the top, i.e. a couple of cm in front of the fin
4) I retaped it with the bottom tape tight and the top tape normal.

Now the tailplane sits at a subtly different angle. I measured nothing, just took a guess based on the video posted recently of the full sizes Radian mods.

I lobbed it over the lawn to check it flew OK then went and soared it.

As a postscript, I've just cut another 2mm from the bay to test with both my standard battery and 190's. Report will follow.

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