Build Thread: RCRCM Sunbird build

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I told myself not to get any plane for this slope season as I have quite a few birds to fly and will have trouble flying them all this season. But... as usual I broke that promise to myself, got the RCRCM Sunbird and have two planes which have not seen any slope time at all.

Reasons for getting the Sunbird:
1. I wanted something to be fast
2. Small and handy to bring around (the Sunbird has a two-piece wing making for easy transport)

My first impressions when I received the kit from Soaring Composites as that this was very well-built plane with a lot of the details done up for you. The finishing was excellent and it generally looked like a very sexy plane, especially at the tail ends where it was nice and rounded.

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I started the build with making holes for the 4-pin connectors between the wing and the fuse. I used a transparency with the outline of the wing to mark out accurately the placement of the holes on the wings and the fuse.

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Instead of working on the wings first, I decided to work on the more challenging part of the build first: the integrated ballast tube servo tray.

After measuring out the ballast tube to get the "optimal" CG location, I proceeded to cut out the holes for the rx and servos on the given plywood for the servo tray.

For added "bling", I added some silver-coloured carbon to the top of the servo tray. This also covers all the ugly marking i had made on the ply.

I then added a triangle balsa stock to the bottom of the ballast tube for extra support. I don't want the ballast tube to give way when it's fully loaded in a dive.

[msc]

I read a few reviews and had always wanted to get this Sunbird. However, I already fulfilled my quota of 3 new gliders this season. I noticed that my store room is almost packed to the brim. There is hardly any useable space there.
Let's see how this bird handle light winds, I already knew what it could do in strong winds!
Are you aiming to maiden it up north this weekend?

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Hi Kah Marn,

This bird has had its maiden flight out of the way. The CG stated on the instructions are way too forward to my liking, but that could just be me.

Already flew this bird in light conditions and it just stays aloft effortlessly. The lift seems free on this bird. But it doesn't react well to sink, as I have yet to get my CG set optimally for my kinda flying.

Cheers,
Adnan

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After splooge-ing the end of the ballast tube and applying loads of epoxy on the edges of the tray, I let the assembly adhere itself secure onto the fuselage. As usual any extra epoxy was removed.

After the servo tray has set itself nice and good i proceeded to screw in the servos and velcro down the rx "face down" onto the assembly. I added a power output/input extension just in case i wanted to have an altimeter or something in the fuse. The extension will allow me to just plug it in without having to pry the rx out of the assembly.

I know it may seem excessive to put in a battery checker for a 1.5m glider but I'm just paranoid. Running 6 digital servos, I don't want any accidents happening. I'd like to know my batts are in good shape everytime I plug them in and toss em off the slope.

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I then proceeded with the tail surfaces installation. The elevator went ahead without any problems, but was faced with a totally different situation with the rudder.

First issue I faced was that i was getting very little "left" travel for the rudder. To overcome this i had to sand the the hinge on the inside and sand off some of the wiper so that it would have some decent travel.

Moving forward, I trial fitted the clevis and found that i could not get a decent right rudder as it was binding with the clevis. I proceeded to sand the clevis down to what i felt was a comfortable amount of material left but still could not get decent enough throw. So I proceeded to remove some material on the rudder itself. I felt comfortable removing stuff from the rudder side as the was a big mass of splooge holding down the rudder control horn.

After all that, I finally got the kind of rudder throws that I am comfortable with.

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Now that the fuse part was generally done I proceeded to work on the wings which I initially thought was a walk in the park.

Firstly, I sanded the wipers as some of it had some binding issues. I did not want my ailerons or flaps to bind as it was going back to neutral in flight or I'll be in a bind myself. Corny? I think so too.

I learned the importance of getting proper geometry of the pushrods for control surfaces when I was building my DLGs last year. In short if it's done well I will avoid getting control surfaces with double neutrals, avoid binding and get proper throws. I really needed to look out for binding in this particular build as I was running digitals and I don't want the servos to suck up any more juice than necessary and find myself out of power in the sky.

I worked on all the measurements on one wing first. Trial fitted the flap and aileron servos a million times just to get everything right. Jotted down the measurements and transferred this info onto the other wing. Only to find the other wing was very different from the first. I couldn't get the same servos to fit under one of the wings, the servo bay holes was off by a bit, etc. So i had to do all the tedious work of getting everything right all over again. Maybe I could have let it go as stuff was just off by a few millimetres but I guess I'm anal that way

Yes I did forget to mention that there was a lot of grinding and removing of "stuff that got in the way". I had to even grind off some of the shear web (? is that what you call it) to get enough throws for the flaps. I also had to grind off the ball links thing so that it won't bind. Lots of grinding and sanding for the wings. Not for the weak-hearted.

After that I soldered the tangle of wires double checking that I will not short circuit anything, then hot glued the wires down so that it won't knock against anything.

Once all of that was done, I epoxied the servos into the wing. wrapping the underside of the servos with painter's tape before epoxying it down. I taped the servos down and then weighed them down as the epoxy cures. Phew nothing moved, or I would have pulled out my hair in sheer frustration.

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I initially planned to use MKS DS450 for all the control surfaces but i found out that this relatively thin servos were still not thin enough for the ailerons. I then switched them out to Tahmazo D6011. I've had good experience with these servos on my Predator DLG. I use them on the elevator and find that they centre well and don't buzz. They also have quite decent torque for the size and it's priced reasonably.

"Thin wings = Fast plane", I hoped.

The one thing which bothered be even before i got the kit was that the Sunbird came with flat servo bay covers. I knew this was going to be a problem with the servo control horns. No other way but I cut holes into them.

I can't be flying with big gaping holes in the wings. A simple fix: I used the MKS servo plastic packaging and made them into blister covers for the holes. Once I have the time I gonna make me the blister covers out of either carbon fibre cloth or fibre glass cloth. We'll see how that goes. For now I'm happy that this quick fix is working rather well.

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After that it was just a matter of lining up the 4-pin connectors in the wing to the fuse for a perfect fit. I read somewhere that it's better practice to have the male side of connectors on the wing side. This is to avoid the miniscule chance of shorting out on the fuse side when the battery is plugged in.

After that, I'm done with the build.

Brought the Sunbird out for its maiden flight and i balanced the plane out with the CG at 67mm. Recommended CG settings in the instructions was between 60-65mm.

I had a tough time on the first toss. The plane was nose heavy. I was struggling to keep the nose up even in the strong winds. I then moved the CG to 69mm and it felt so much better.

Immediately after the toss the plane climbed up effortlessly. I did not even have to try to climb, just pull on the elevator and it will just go up. Once I was at a comfortable height I did a dive test. The plane did not pull out but went down straight as an arrow. It was quite scary for me as I don't have the guts to do real fast dives and pull out at the last moment.

First impressions; with all the grief I went through during the build process I wasn't that much impressed on the maiden either. But the change in CG brought out a totally different plane. I like how light it is on the wings while still being able to go fast on a dive. I also like the fact that it is a full house plane in a very small package. It has a two-piece wing which makes for easy transport. All in all, I'm beginning to really like this little bugger, but for now it has a long way to go to match the fun factor I'm getting with my Ginger.

Cheers Y'all,
Adnan

[joe yap]

Wah, you must have a lot of free time to build and fly, in between sending and picking your kid up from Playgroup lessons.

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Wah, you must have a lot of free time to build and fly, in between sending and picking your kid up from Playgroup lessons.

Can fit in flying sessions in here and there

Cheers,
Adnan

[Sunstorm]

Good job Adnan/Optimus.

See you at the slope this week. I'm going running.

[Ghostfit]

Good Job bro ! ...I need all the inspiration I can get on my first mouldy.

[randomtask]

Thanks Jules, Tony.

@Jules, hopefully have some time this week for me to go down to the slope.

@Tony, c'mon man, The slope is calling for the other Typhoon to make an appearance. Should be a simpler build than the Sunbird as the bigger size makes it easier to handle.

Cheers,
Adnan