Hobby King Red Swan Balsa Glider Build Thread

[Joker 53150]

I took the day off and since the kids are at school and the wife is working I'm free to play! There is too much wind to fly, so time to make some balsa dust! I wanted to get some work done on the Red Swan, my Model Airplane News Contest plane, and another plane or two.

First up is starting on the Red Swan's wing center section. I had to refer to my previous build on this wing to make sure I had the order of the ribs correct. I'm glad I did that build thread, as it made setting up this wing quick and easy. I'm doing a few things differently on this build. The previous build had a block of 6 ribs right in the center. In this case I'm leaving four of them out and will instead use some balsa block carved to shape in a few key areas. The wing hold-down bolts will go through this blocking instead of the stack of ribs. In theory this should save a little bit of weight.



I'm also using only half of the spacers that go at the spar. There are enough pieces to install one in front and behind the spar, which I did on the previous build. Based on the strength of that previous wing I think it's just not necessary so I'm only putting them in front of the spar (as pictured). I may change that after the glue dries and I get a chance to see if there is too much flex, but I think this will work.

The leading edge will be carbon fiber as the previous build used. The kit includes a couple lengths of hard balsa stock that should be used, but in my opinion it just isn't as good an option as using a little CF.


One note to anybody building this plane, pay close attention to the pieces used for spacing the ribs! If you look closely you'll find a couple of them are cut with a very slight angle instead of a standard 90 degree cut. The pieces with the slight angle are used at the ends to make the outside ribs lean in just slightly to set the dihedral properly. These are easy to miss.

 

[Joker 53150]

Here's some more detail on the angle and splice between the inner out outer wing sections.

There are two light plywood pieces per side that help set the angle. You glue them together and they get inserted down the center of the wing spar. It isn't shown in the instructions so it took some detective work on the first plane. This time around I did it a little differently.

Pic 1 shows the plywood stuck into the end of the wing center section. After the ribs were installed on the bottom spar and the glue set I cut out the little area on the rib between the top and bottom spar. The ply was coated in glue and put in place before the top spar was installed. I also elected to use the rib spacers both front and rear around the ply just for some extra durability.




Pic 2 shows the outside ribs are slightly angled in at the top, as planned. It also shows the ply joiner angles up above the bottom spar. This bottom spar still needs to be cut off flush with the outside edge of the ribs, like the top spar. There has been minimal sanding on the ribs or components so far. I've got a long aluminum sanding bar that will take care of things once I'm far enough along. On other planes I've tidied it up before this point, but in this case I think it's best to wait if possible. I just don't trust the people who made it to be as accurate as some of the other kits I've built.




Pic 3 is the ply once the spars were trimmed as needed. When you join the wing sections you normally just glue the ribs and coat the ply with glue, stick 'em together and clamp them. I'll do both wing ends at the same time so I can measure them at the wing tips to get them the same height/angle.

I've also had a change in plans for the wing. I had planned on using one servo mounted in the center of the wing to control the ailerons, but now that I'm farther along I've found there just isn't enough room for me to do it the way I wanted to do it. I could probably make it happen, but it'll just be easier to do it like I did on the previous build with small servos mounted in the wings.

 

[Joker 53150]

Moving on to the wingtips, I'm starting on the right side. This is going MUCH faster than the last time since I know what to expect. The rear edge of the ribs that go in front of the aileron all have a small tab that fits into a slot. Surprisingly these all fit very well with minimal sanding. This sets the distance between the ribs which is a nice feature.




However, this spacing doesn't match the width of the spacers that go at the spar. The spacers are all about 1/16" to 3/32" too wide. If you try and use them all as-is the front end of the ribs will end up fanning out compared to the back end. To fix this I just trimmed the spacers to match the distance between ribs at the trailing edge. Not a big problem if you know it's coming.

Also, builders should note that the spacers also taper towards the wingtip. You can see in the pictures that I've numbered them from 1-8, narrowest to widest so I didn't screw up the order. As with the center section of the wing I'm only going with one spacer between each rib instead of two. I did that on the previous Red Swan build and have had zero problems.




Also, the quality of the wood for the top & bottom spars is very inconsistent hardness. A few pieces were hard and a few were soft. Typical. I made sure to set aside a good mix so that the wing is as consistent as possible across the entire length. To do this I had to splice a couple pieces, but I'll brace it a little to be safe.

This will be about as much as I do on it today, I've got other planes to work on...!

 

[Johan]

Last winter I started and completed a balsa glider kit from Hobby King, the "Red Swan". .....
This is what Hobby King shows on their website:
View attachment 12843
And this is what I finished with (before the motor and decals were applied)
View attachment 12844

Well, one thing for sure: you made it much more appealing

And.. I've got a Balsa build going right now, but my skills have not had any exercise for the past two decades, so close-ups like you've shown: I would not dare (you work way cleaner than I do )

 

[Joker 53150]

It is hard NOT to improve the crappy pics on the HK site! I don't know why they don't do a little better job at marketing it, but maybe there just isn't enough demand and profit in it.

I clean up the bench between builds. Lately I'm working on so many different planes in various state of repair or build it is constantly being cleaned, which I like.

 

[xuzme720]

Since the GeeBee is done and flown (I'm 2 for 4 on bringing it home in one piece), I'll be starting mine soon. I might post a few pics as I go but probably won't do another build thread on it since you already have this fine one here! Already giving me ideas for mine!

 

[Joker 53150]

So I finished the first outer wing section last night and tried test-fitting it. To slide it onto the plywood connector you need to cut out the balsa between the upper and lower spars. This effectively puts a gap between the front and rear of the rib, so you lose a lot of strength temporarily. I'll go back later and add some gussets for strength.

So back to test-fitting, I ran into a small problem I didn't have on the first build. The kit comes with 4 light plywood pieces, two for each wing. I assume they are supposed to be glued together as they fit perfectly between the top/bottom spars and the front/rear spacer blocks. On the first build I didn't know they'd fit so I only used one per wing. It's held up fine, so strength hasn't been an issue (yet). But by using only one of them it allowed the piece to move around, avoiding the problem I had this time.

The first picture shows the center section held over the outer section. The spars don't line up as the outer wing spar angles back slightly. I could re-design a number of parts and make the spar go straight instead, but it's far easier to just make some room for the ply.




The second picture shows the rough cut-out I made in the outer wing section's spacer block. The ply pokes through allowing the spar to angle back slightly as it should. The dihedral of the ply also brings the wing sections together perfectly now, so I'm able to glue them together. I still haven't installed the carbon fiber leading edge on the outer section. As said, a little extra bracing is still needed in a few spots just to get back a little strength.

 

[Joker 53150]

Since the GeeBee is done and flown (I'm 2 for 4 on bringing it home in one piece), I'll be starting mine soon.

Hey, that's almost 50%, that ain't too bad!

 

[Joker 53150]

A small update, but a little progress either way. As said dozens of times over this build-thread I've been trying to keep the weight down whenever I can. Every gram counts! The wing hasn't given me as many chances as the fuselage to shave weight so I'm picking little bits here and there where I can.

The trailing edge of the wing has a little extra material so I thought about just drilling some holes into it. I also considered scalloping the trailing edge similar to what you'd see on the old WWI fighters, but this wouldn't look quite right on this bird. Instead I just did the scallops on the inside where it'll be hidden by covering. This won't add up to much overall, but it'll offset a little bit of the extra bracing or glue used elsewhere.

I'm about 2/3 finished with the remaining wingtip, so the full wing will be assembled soon and I can get the final details worked up.

 

[Joker 53150]

Even the wingtips have a little extra meat on the bone that can be sacrificed! I could probably take more without any problem, but this little bit should be good enough for now.




If you squint and rub your eyes really hard it almost looks like an airplane!

 

[xuzme720]

Can you tell a weight difference yet or are you waiting to compare the all-up weights?

 

[Joker 53150]

I can't really tell right now as the first Red Swan is covered, has electronics, etc. Assuming the balsa is comparable from one kit to the other it HAS to be lighter, but that is a big assumption knowing the "quality control" of Chinese manufacturers.

But I do know that I'm using better and lighter building techniques on this build which will also help in the long run. Less epoxy, less Tite Bond II, and fewer glue joints should benefit in the long run. I don't know that it will ever be as light as I originally hoped for, but I'll still keep pushing to do it light.

 

[Joker 53150]

Both wing tips are installed and the leading edge carbon fiber is all in place, so I'm now focusing on the center section sheeting and how I'm going to fasten the wing to the fuselage.

The top and bottom center section is normally fully sheeted, which is what I did on RS #1. For #2 I decided to skip the full top sheeting and instead use various size rib caps to give it a little more interesting look. Any wing bolts will require some additional support inside, but that will be added when I get that far. The bottom center is fully sheeted as shown as that rests against the fuselage. I'll sheet the top in front of the spar as well.




Moving on to how I'll hold the wing in place....

The kit includes a couple pieces of plywood which are to be used for wing bolts. I think that's what they are for, the instructions don't given you any detail on how to use 'em so it's all a guess. On the previous build I started with rubber bands over carbon fiber rods which worked well. However, I don't like using/trusting rubber bands so I'm in the process of changing it over to a bolt-on wing. The bolts will go through the big block of ribs in the center of the wing. Red Swan #2 doesn't have that big block of ribs as I'm trying to save weight and generally do things better than the plans call for.

So the original plan was to simply just bolt the wing on, which should work fairly well. But it's not as clean and elegant as I'd like. Here's where taking my time has paid off for me, as I didn't rush into just adding the captured nuts for the bolts. I was looking at my Mountain Models Lucky ACE last night and it dawned on me that the method for that plane might work great on the Red Swan. It uses a dowel on the front of the wing that fits into a hole in the fuselage. This locks the front of the wing in place without any visible bolts. Then the back is simply held in place by a pair of small nylon bolts. This (in theory) should work great for the Red Swan so I cut the pieces to test it out. I still need to cut and install the remainder of the sheeting, and will probably use the front half of two ribs to sandwich the carbon fiber.

More to come!

 

[xuzme720]

The dowel trick is pretty slick! I may have to steal that one on mine!

I was a little concerned with you removing the cross grain sheeting on the top of the root section since that portion of the wing will see a lot of compression loading in flight and the sheeting helps distribute that load across the center section. But with the CF leading edge and lightening you've done, it probably wont be an issue. Before you cover, I would assemble the whole plane and pick it up by the wingtips and give a few little bounces to be sure you don't have a weak point there in the root section...

 

[Joker 53150]

The dowel trick is pretty slick! I may have to steal that one on mine!

I was a little concerned with you removing the cross grain sheeting on the top of the root section since that portion of the wing will see a lot of compression loading in flight and the sheeting helps distribute that load across the center section. But with the CF leading edge and lightening you've done, it probably wont be an issue. Before you cover, I would assemble the whole plane and pick it up by the wingtips and give a few little bounces to be sure you don't have a weak point there in the root section...

I'd like to take credit for the idea, but I stole it from Mountain Models and they probably got it from somebody else...!

Good point on the concern with compression and the lack of sheeting.

To gain back some of that strength I cut a channel for a 3mm thick-walled CF tube, the same material I used for the leading edge of the wing. It has been epoxied in place and will hopefully give me back some of the strength I took out. I may also put a piece in at the trailing edge. I don't know if an additional piece is necessary, but if I do it carefully the weight penalty should be minimal.

You can also see in this picture that a couple extra "B3" ribs were cut in half. These were 2 of the 4 ribs I didn't install as a "mega rib" in the center of the wing. Once the epoxy holding the wing locator is dried I'll put these in on either side of it to give it a little strength and to keep it from shifting, kind of like a carbon fiber rod sandwich. I'm still planning to add some small blocking on the bottom of the wing to help keep the wing from shifting to the side like I did on the previous build. I also want to add a little extra light ply around the hole for the wing dowel.

 

[xuzme720]

That should be plenty...

I'm still up in the air over whether or not I'm putting CF on the leading edge or just sticking with the stock material. I'll be using CA on my build which should be lighter to begin with than aliphatic resin glues. Drawback is less bond strength but I haven't had any issues with it yet...

 

[Johan]

Hi Joker:

Really enjoy the build log, you're doing fine!

I clean up the bench between builds.

I actually alway HAVE to, I don't have a designated 'building bench' my bench is actually my desktop.
So during working hours it houses my monitors, mouse(s) and keyboard(s) and in hobby time it is cluttered (and I mean CLUTTERED) with:

Balsa ~21" wingspan Hawker Tempest skeleton, Batbone tricopter, hot glue gun, CA, balsa glue, lots of USB cables, tiny TFT, Boscam 5.8GHz gear, GoPro 3, 3DR radios, 9-in one simulator box, Turnigy 9x, two LiPo's, APM 2.5 + GPS, some paper build plans, oh, and some (at least 20 years old) Ski glasses now fitted with a fresnel lens (today's project), to go with the mini TFT (my "lame shark" project)

Note: this is actually me looking around my desk. Man, I have to clear this all up before tomorrow morning.
Note to self: need some extra crates to store stuff without damaging

 

[Joker 53150]

I'm still up in the air over whether or not I'm putting CF on the leading edge or just sticking with the stock material.

After doing it twice there is no way I'd ever go back to use the stock leading edge material they provided. In the first kit it was brittle and never would have sanded to shape without constant repairs. In this kit the stock was much better, but the material is nowhere near as strong as CF so this is one area I'd take the weight penalty any day. Plus the CF doesn't want to bend so you end up with a very straight leading edge. Just my $.02.

 

[Joker 53150]

Hi Joker:

Really enjoy the build log, you're doing fine!



I actually alway HAVE to, I don't have a designated 'building bench' my bench is actually my desktop.
So during working hours it houses my monitors, mouse(s) and keyboard(s) and in hobby time it is cluttered (and I mean CLUTTERED) with:

Balsa ~21" wingspan Hawker Tempest skeleton, Batbone tricopter, hot glue gun, CA, balsa glue, lots of USB cables, tiny TFT, Boscam 5.8GHz gear, GoPro 3, 3DR radios, 9-in one simulator box, Turnigy 9x, two LiPo's, APM 2.5 + GPS, some paper build plans, oh, and some (at least 20 years old) Ski glasses now fitted with a fresnel lens (today's project), to go with the mini TFT (my "lame shark" project)

Note: this is actually me looking around my desk. Man, I have to clear this all up before tomorrow morning.
Note to self: need some extra crates to store stuff without damaging

Thanks. I'm lucky that I have plenty of room to work, an entire unfinished basement, although it is cluttered with boxes and other misc stuff. I was able to move enough stuff around to give me room. I actually have two work tables. One is a door laid flat on stands which acts as my "overflow" bench. There are currently four shelving systems to hold planes, parts, tools, etc. Last is my main workbench which was our dining room table when I was growing up. With the two extension leaves in it there is a lot of room to work. it is nice being able to work on the larger planes without knocking everything off the table...!

 

[xuzme720]

After doing it twice there is no way I'd ever go back to use the stock leading edge material they provided. In the first kit it was brittle and never would have sanded to shape without constant repairs. In this kit the stock was much better, but the material is nowhere near as strong as CF so this is one area I'd take the weight penalty any day. Plus the CF doesn't want to bend so you end up with a very straight leading edge. Just my $.02.

Your probably right. I'll just have to look through my stock and see if I have any or if I need to order some.