SU-27 ULTRAFLY Build / Contruction - RC Groups
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May 05, 2005, 04:38 AM
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SU-27 ULTRAFLY Build / Contruction


Since I could find no build contruction thread on the Ultrafly Su-27 I have decided to start my own.

This thread is for everyone to contribute their comments and suggestions.

I got the Kit supplied in australia with the included D series 3200 kv brushless motor. I paid $189 australian for it. The kit was a bit damaged when I opened it with the nose dented slightly and one of the wings slightly scuffed up.

I started to build early this morning. Some comments so far.

The foam quality seemed quite good and is fairly dense. All the parts seemed to be included.

I found the manual to be below average. It is not written in English. It is simply a series of diagrams. Even though the first page of the manual indicates some of the parts in English the rest of the manual is no longer in English this makes it a bit confusing when trying to work out which part to use next when you halfway through the manual.

Firstly I assembled the canopy magnetic latch and then cut the plastic canopy and stuck it to the foam cockpit. I then as per the description in the manual cut the ailerons from the main wings and use the included plastic hinges to attach them. The manual recommended two hinges per wing however I used three for strength.

It then suggested to CA together the plywood back spine. This is where I ran into a major problem.

There's an error in the manual!!

Page 4 Procedure 3. This diagram indicates that rounded hump should be upwards and the same direction up as the black plastic runners for the elevator rod. I CAed these two parts together as per the diagram. I then turned the page...

Page 5 Procedure 5. Now indicates that the hump on the plywood spine should be up and the black plastic runners and elevator assembly should be pointed down. This is a major error. Fortunately I was able to use CA debonder and reglue the part.

Make sure that you do not make the same mistake as I did.

More to come..
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May 05, 2005, 04:51 AM
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The elevator assembly is rather unusual and involves inserting a metal rod 2mm into the plastic runners and having to bend them 90° 25 mm from each end. The problem with this is that unless you have very accurate equipment is very difficult to have exactly the same angle and to have both bends completely flat.

You then have two insert a metal circular part, onto the 2mm metal rod which is then placed inside of a plastic horn arm which is used to attach to the elevator servo. The problem of these is that you have to place a small screw into this metal part. This is supposed to grip the 2mm metal rod. I doubt it would be reliable or safe. It seemed like a major design oversight or flaw to me. I took the advice of other members on this forum and used my dremel to flatten a section of the 2mm rod to give the screw something to grip. I don't think it would be safe without this mod.

After this you need to glue the wings on, the manual does not indicate how to line these up. I took my best guess and use the channel for the fibreglass rod as a guide.

You have to glue the plywood section with the elevator assembly onto the main public model at this point. It is fairly straightforward and clear.

Now you have to assemble the elevator. This involves gluing two halves of each of the elevator sides, made out of depron. It doesn't seem very strong or Robust using this method. As each half of the Depron is simply glued over the thin metal 2 mm rod that has been bent. After you glue them together and align them you have to shape the leading and trailing edge using sandpaper. I didn't find this method very good and it doesn't seem very strong to me. I would think balsa or thicker dense foam would be a far better solution.

More to come..

May 05, 2005, 03:21 PM
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Last edited by Holtenbacker; Aug 24, 2005 at 09:32 PM.
May 06, 2005, 10:22 AM
druegeme's Avatar
I have just started building.

The plastic covers for the belly are way too heavy (48g). I decided to leave them off but glass the belly ducts with Epoxy and put some light glass fabric over. Same for the nose. Came out nice, will post pictures soon.

Also I have hollowed out the ducts, intake and outlet. The ESC will go into one of the ducts and will get cooling this way. For battery cooling, I'll make two holes into nose to get some air flowing. It is amazing that the concept of cooling appears to be completely absent from the design of this kit.

As in my F-16, I will not use the stock foam elevators but will make my own out of Balsa. It is not very difficult and they work great on my F-16.

I agree that it is mandatory to file a flat spot into the elvator linkage where the screw will go on, otherwise you risk slippage- not good! Just a little work for you, but a great improvement for the model.

Started to cut out the decals- this is a lot of work! Takes hours, literally. But it will be worth it, like on the F-16. The decals look great.

Will post more, with pictures by the end of this weekend.

Suntzu, if you hit more errors in the instructions, please post soon, I will appreciate it!!!
May 06, 2005, 08:39 PM
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I have found that the included plastic linkages to be soft and very weak. I have no confidence in them at all. I'm at an impasse as I dont have stronger linkages in my garage and I really really dont want to use the included ones.

How are you finding the included linkages?
May 06, 2005, 10:27 PM
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Last edited by Holtenbacker; Aug 24, 2005 at 09:33 PM.
May 06, 2005, 10:37 PM
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I actually meant the clevis. They are so soft and weak. I will use others. Yes the horns are good and strong though. I will also tape the bottom, it will save weight and allow for CG with LIPOS.
May 08, 2005, 07:18 PM
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Ok, I have ditched the included clevises. I have used the small EZY connectors instead. Unfortunately a combination of the heavy wire and EZY connectors has overloaded my 6g wing servos so I had to install 9g 084 waypoints, which I have also used as elevator.

I did some testing on the included BL motor and gearbox and have not found to be any more efficient than mu old Align 1500kv short can BL motor. So I am ditching the included motor and using the align as it is Direct drive and much quieter. The 3S lipo and 7x5 looks about right at 13amps and about 11000 rpm. I might get a few more rpm when my new batteries arrive.

I will put my ESC in the right motor cover on bottom so it gets cooling and so I dont have to extend the 3 motor wires, just the 2 battery wire. I will use heavy guage wire to do the extention. I will not be using the plastic belly covers. I will tape it for now and glass later on.

More to come.
May 09, 2005, 08:38 AM
Registered User
How did you determine that the Ultrafly BL is not more efficient than the Align 1500? Which Ultrafly BL is it? I happen to have an Align 1500 long on my Align 400 F-16. It behaves a lot like a Mega 16/15/6 but sounds different. (Just curious, not to start arguements.)
May 09, 2005, 08:45 AM
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You get the D series 3200kv and a gearbox to gear it. My align is the old 1500kv S short design, it is my least effiecient motor but is as good as this ultrafly one geared. I used to have a A series ultrafly 2400 kv and it was brilliant. But not this D series, its a budget one.
May 09, 2005, 10:02 AM
Akura2's Avatar
Build pics?
May 11, 2005, 01:03 AM
druegeme's Avatar

halfway there

some pics from my build so far.

1: dig into fuse to accomodate LiPo in anticipation of Cg challenge. Used hot copper wire heated with gas lighter.
Last edited by druegeme; May 11, 2005 at 01:17 AM.
May 11, 2005, 01:33 AM
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Im in a dilema. Do I extend the ESC to Motor Lead or ESC to battery lead, and how do I cool the ESC?

I think I will put the esc in the engine cover also with an intake hole like Druegeme.

Nice elevator mod. Whats the alcohol do to the epoxy? How many wattas are you thinking of jaming through this russian beast?

I think I will fly before I pretty it up in case I crash on maiden

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