Hobby King SunBird Motorized Glider Build Thread

Joker 53150

Mmmmmmm, balsa.
Mentor
The canopy construction is very similar to the Red Swan builds - two sides and a curved top. I did the Red Swan canopies each differently - one was scored heavily on the inside allowing it to curve easily and one was left flat without the curve. As I do more building I learn better ways to do things. Since the last canopy I found that soaking the balsa in Windex makes it much more flexible. When it's wet you bend it as needed, clamp it into place, and let it dry. Once that happens it holds most of the curve easily. The canopy top in this case doesn't need much of a curve but I still used the Windex trick. Pic one shows the top clamped to the sides which set the curve.

1.JPG


Once dry I was able to glue the pieces together and set it on the fuselage to help align all the parts properly. You can see in Pic 2 the dents in the top of the canopy caused by the clamps - the wood was pretty soft when wet. A little balsa filler will easily take care of any dent left after sanding.

2.JPG


With the canopy pieces dried and sanded I was able to take care of the latching mechanism to hold the canopy shut. As with the Red Swans I went with a simple and secure layout. A short section of popsicle stick at the front keeps the front of the canopy from lifting in flight while a magnet at the back keeps it closed. The magnet is glued to the inside of the canopy and it sticks to a generic thumb-tack. The tack is simply stuck into a piece of scrap balsa glued in place. When the canopy is closed it pushes the tack down into the balsa only as far as needed. Let the epoxy cure before opening it again, and if all goes well you've got a very secure hatch. To be extra safe I usually use some hinge tape across the front of the canopy as well. The hatch doesn't need to come off completely, and the tape hinge will still allow me to flip the hatch open for battery access.

3.JPG


Pic 4 - There is a small gap at the rear end of the canopy which should allow some airflow past the battery, ESC, and motor.

4.JPG


The elevators are tied together with the shown bent wire piece, which fits into each elevator section. I used a small drill bit and ran it through the balsa by hand. DO NOT GLUE THESE TOGETHER AT THIS TIME! The elevators get installed after the horizontal stabilizer is installed on the fuselage.

5.JPG


Most of the fabrication is complete, and I'm focused now on all the remaining details - creating aileron servo mounts, pushrod installation with the clevises, etc. I'm waiting for the motor and transparent covering to arrive so I can finish it up, however test fitting with the prop has shown a potential problem. The prop I want to use doesn't fold back properly over the fuselage as it's too tall at the nose. I already have the prop I want to use - it's the same one I used on the second Red Swan build. It is convenient having multiple planes using the same parts so I'm going to look into making it work.

6.JPG


The tail just needs pushrod hardware installed and it's ready for covering. It should look nice with a combination of white and transparent colored film.

7.JPG
 

Joker 53150

Mmmmmmm, balsa.
Mentor
I'm waiting for the delivery on the transparent film I'm going to use for the highlights on this bird, but the rest of it will be white so I'm able to get some of that covering done now. The movable tail surfaces will be transparent red, but the fixed surfaces and most of the fuselage will be white. The pieces pictured have been glued in place before covering so I started off by adding a 1/4" wide trim piece between the tail surface and fuselage. This will make the finished work look cleaner as you don't see a gap where the surface meets the fuselage. Before covering I ran a small drill bit through the internal pieces to allow the air to flow out as I shrink the plastic. I've had some pieces balloon up during the shrink-phase because the air couldn't escape.

IMG_2475.JPG

It looks pretty plain right now, but once the color is added it should really pop! I'll add some extra detail on the fuselage as well to keep it interesting.

IMG_2477.JPG
 

Foam Addict

Squirrel member
Beautiful job! I am in awe of that framework shot.

That doesn't look like a lot of stabilizer for that plane, I hope you have good pitch stability.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
Although not quite doubling the surface the elevators do add a lot of extra surface. I'm sure the Chinese would have fixed it while reverse-engineering somebody else's design it had it been a problem. :rolleyes:
 

Joker 53150

Mmmmmmm, balsa.
Mentor
If you lived some place warm I might consider it! I've got a lot of covering in my near future... This SunBird needs to be finished, I'm going to help my dad cover his contest airplane for his first try at using anything other than tissue covering, and there are two heavily modified Sun Birds that will be started within a week. The more I use it, the more I really like the SoLite light-weight covering. I'm finally getting the hang of it, and though not perfect, it's usually enough to keep me happy. The heavier coverings are still a real pain for me to use, but I'll eventually get the hang of those as well.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
The covering arrived a few days early so I'm trying to get as much done over a long weekend as possible. I'm still missing one of the servos for the wing so I won't be able to finish it, but it'll be close. Tail surfaces are covered and the wing will get about 3/4 done while waiting for the last parts.

To date this is the trickiest wing covering I've tried. A previous build had two-tone covering, but it was a smaller and easier job. Here the goal is to go the full length and throw a curve in at the tip. To make it more fun I'm using two completely different brands and weights of covering film. The leading edge gets SoLite white and the remainder is transparent red from Hobby King. The films stick and shrink at different temperatures so I have to be very careful when shrinking the film so that both come out smooth.

The white is also a little transparent since it's a lightweight film so the overlap is partially visible. I might fix that with an accent pinstripe along the length of the seam, but I'll decide on that later. After the wing is fully covered I'll go over it and do the final shrinking to get rid of the remaining small wrinkles and work out any twist.

The motor also needs to be tested so I can get that installed. Covering on the nose can then be done.

IMG_2512.JPG
 

Joker 53150

Mmmmmmm, balsa.
Mentor
The wing servo I needed to complete the build arrived today, so I plugged it in to center it and installed it. The rest of the wing was covered and I hooked up the linkage to the aileron so I could test everything out.

And the servo doesn't work... Well, it works intermittently which is just as bad. Damn! :( I've ordered dozens of servos for my planes and this is the first one I've had fail (not including the ones which were destroyed during crashes).

So now I need to re-order one and wait so I can finish the plane. Could be worse, it could have failed during flight!
 

Joker 53150

Mmmmmmm, balsa.
Mentor
The replacement servo arrived today so I was able to finish up the build. Everything tests out fine, the CoG was checked, lock-tite on the screws, and a final check was made for air-worthiness.

And then I hung the plane up from the ceiling to wait for warmer weather. :(

I still need to swap out the Orange RX for a FrSky with telemetry, but otherwise it's ready for flight.

IMG_2583.JPG
 

Joker 53150

Mmmmmmm, balsa.
Mentor
Today is about as good as the weather is going to get for a while, upper 30's, sunny, winds at about 10 MPH. Still plenty of snow on the ground, but the roads are clear and dry, as was the small cul-de-sac I often fly from.

After checking the controls and radio programming again this morning I grabbed a couple 1000mAh 3 cell packs and headed out. Surprisingly, recommended throws aren't included with the kit so I did a little guessing based on how the Red Swans fly. I programmed ailerons to give me maximum throw without overworking the servos. From what I've seen with the previous planes a lot of aileron shouldn't get me into trouble, especially when I temper it with a little expo. Rudder was set with high and low rates. Low rate was about 5/8" each way and high rate about 1/4" more. The rudder is pretty big so I figured this would be safe. Turns out low rate was just fine and I never used high rate. Elevator was about 1/2" each way on low and about 5/8" each way on high. Again I never used high rate.

The wing was installed when I got to the field, throws and programming checked again, and I started my timer figuring I'd go maybe 7 or 8 minutes depending on how it handled. The flight ended at 22 minutes. :)

With no lift and keeping it pretty close to me on it's first flight I used the motor more than I'd normally want to, taking it up a few hundred feet and then doing lazy laps around the field. The rudder has a lot of authority, and I can see how the original Bird of Time can work so well without ailerons. With a little more dihedral I think this one might handle life as a 3 channel as well. Aileron input worked well enough, although it's a bit slow in reacting. Flight was very predictable once I did some trimming of the controls and I expect this plane to do well on a good warm sunny day.

A couple problems, however. Orientation was pretty difficult for me because the top & bottom of the wing are the same red/white pattern. I'll add something to the bottom to help it stand out for me. Also, the plane had a strong tendency to climb under power so I figure my motor could be angled down a bit more. I don't know that I can do that easily now that the motor and firewall are mounted so I'll cheat and mix in a little down elevator with the throttle channel. I had this issue with the Red Swan as well. It isn't a huge deal since I want to climb with power and the power should usually be off anyway, but flat powered flight would be nice.

So other than mixing the elevator and throttle I'm not changing the programming and I'm not changing anything on the plane for a while. I think I've got the battery placement for a good CoG, but will determine that better once it warms up and I get some good glide time with it.

So success, and the plane gets hung back up to wait for another chance to fly.
 

xuzme720

Dedicated foam bender
Mentor
Good to know she flies well! I think Teach and I are in the same boat as far as getting one. Once the Christmas empty wallet syndrome has had some time to cure itself, I'll be looking to pick one up also.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
Cool! The wing is a small pain to build but nothing major. The fuselage and tail are a cake-walk. I'm really looking forward to trying it in weather with potential for thermal lift. It really floats well, so it should be plenty of fun.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
Time for an update on the Sun Bird... I've flown it a few times since the maiden flight, but was never really happy with it. It seemed to sink much to quickly and was blown around by the wind. That was during colder weather, and since today is so nice out I decided to take it out and see how it handled warmer weather and slow/steady winds.

I'm glad I took it out! Two batteries (both 3S 1000mAh packs) were put through it, each providing 30 minutes of flight. I couldn't find any thermal lift, so the flights were cycles of powering up to altitude and then cruising around the field. 20-30 seconds of power followed by 2 minutes or so of glide. I played with the CoG and like how it handles with balance right on the wing spar. It still climbs hard with power applied, so that still needs to be addressed either by adjusting the motor angle or by mixing in some down-elevator with the throttle.

Since it flies well, I hooked up the voltage sensor and replaced the standard 4 channel receiver with the FrSky telemetry 4 channel receiver. Now the voltage for the pack will display on my radio, allowing me to fly as long as possible if I can eventually find some thermals! I still think this plane has a lot of potential in the right weather conditions. It might still be a little heavy, but there is a lot of wing area to catch the lift. Maybe I'll need to build a second Sun Bird and focus on building it as light as possible... I did that with the second Red Swan and it's noticeably better at catching lift.
 

barrancobob

Junior Member
The replacement servo arrived today so I was able to finish up the build. Everything tests out fine, the CoG was checked, lock-tite on the screws, and a final check was made for air-worthiness.

And then I hung the plane up from the ceiling to wait for warmer weather. :(

I still need to swap out the Orange RX for a FrSky with telemetry, but otherwise it's ready for flight.

View attachment 16293

this is a great build blog,,, and very useful set of photo....i,v been concerned about my wing set-up for a while..and which way is best,so thanks a lot,,, so once again great work,
 

Joker 53150

Mmmmmmm, balsa.
Mentor
Thanks. I can't say the way I built it is the BEST way, but it worked and the plane flies nicely on calm days. It doesn't like the wind too much...!
 

Foam Addict

Squirrel member
I seem to have missed this log's completion!

Another great build, did the mix solve the vicious climb under power problem?
 

Joker 53150

Mmmmmmm, balsa.
Mentor
I still haven't done the mix yet, but it would certainly help. I can also say that the balance is critical with this plane. When you get it right it really glides nicely. I need to spend a little quality time to dial it in so I can mark the best CoG on the wings.