"Bug" DLG

[FAI-F1D]

After encountering a few issues with my Filip V that are going to require some time to work out, I decided to do the smart thing and go build something. I've seen a lot about the "Bug" over the years, but had no idea until recently that it was designed by my old flying buddy Carl Dowdy. Carl is a master craftsman at models, both FF and R/C. I've watched him clean out his entire stock of beautiful FF gliders in a single contest. Once, he required three gliders just to get in three official flights. All three went OOS. Then he showed up with a FF DLG, a "Spin Up" that he looked on with strong doubt and didn't install a DT timer. It flew perfectly from the start, and on the third or fourth test flight, wandered off into oblivion.

I've never flown an RC DLG, but have built my share of FF ones. My last one was based on Stan Buddenbohm's "Dino Mite", but with tweaks so that it could be built on the cheap. It was my first good DLG, and wandered away during trimming for the indoor nats (indoor gliders are trimmed outdoors because there are no girders to hit when you do dumb things).

Anyway, after some careful planning, I printed out the plans for the X-tail Bug tonight and started building. Here's where we are after the first building session:


It's coming out nice and light. Should be around 3 Oz or less. I don't expect to need too much nose weight since that's good 6 lb C-grain on the tail surfaces. I had doubts about the pod, but it seems pretty strong now.

Stay tuned for the next installment.

 

[FAI-F1D]

And now we have a complete fuselage that literally only needs a coat of minwax and a nut for the wing hold down.

Rudder pushrod is .016 guitar wire, elevator is .013 since it won't take as much of a load. I had concerns about the Coverlite hinges being too stiff in compression, so the pushrods are made to be in tension for that direction of movement. Pushrods go through the tailboom of course.

The Turnigy 3.7 g servos are screwed into place for a variety of reasons. I'm still using a 72 MHz receiver, so that long antenna wire will go away once a 2.4 Ghz system gets installed.

 

[Joker 53150]

I'm finding this VERY interesting! Too bad I've got so many other balsa builds already on the schedule, although something like this could sneak into line pretty easily.

 

[Foam Addict]

MUST RESIST!
Oh that looks gorgeous!:applause:

I'm duct taping myself to my chair so I don't run for my balsa box...

 

[Epitaph]

During christmas I made a V-tail version, and I must say it's an excellent little flier!

Looking great!

 

[FAI-F1D]

Good to see there's another Bug owner on here!

To the rest of you, try it. I've only got about 4 hours in this one so far. The wing surely isn't going to take that long, so for less than 8 hours of building time, you get a small-field DLG. Built carefully, it should come out light enough to hold onto the lightest of thermals.

So far this is a dead simple build...I did make a few changes. The bulkheads are 1/32" ply cores with medium balsa for some extra bending resistance. I couldn't justify using 1/8" ply on something like this. The tailboom is tapered fiberglass and weighed 6.7 g ready to go, which isn't bad considering that I extended it somewhat from what was shown on the plans (16" vs 14.6") because of concerns that it might be shorter than optimal. That said, this boom is much stronger and stiffer than what's needed, so I could save some weight there, allowing even lighter methods up front. Needless to say, I'll probably be working out a redesigned fuselage in the near future in hopes of getting a sub-70 g Bug.

The wing is going to take some decision making. I'm probably going with a laminated balsa leading edge because I don't have enough 1/8" dowel to do the job and because it messes with my sensibilities. Stay tuned for the possibilities of a bunch of little riblets as well because the prospect of covering sag is getting to me.

 

[pgerts]

Another bug

 

[FAI-F1D]

Another bug

Looks nice...What size is the CF rod leading edge, and how does it work for you?

 

[FAI-F1D]

Wing!

Decided to make a wing tonight...

So...all the parts including center section skins:


I started by attaching the center skins to the wing trailing edge (which has been notched for the ribs, by the way)


Set the dihedral on the root rib and assemble the wingtip:


Now thread the ribs onto the spar and find out that the person who drew up those ribs (not Carl, I assure you...this plan came from elsewhere) drew the spar holes in the wrong place and made a bungle of the root rib:


With all the ribs fixed and in place, the first layer of the leading edge lamination (1/16x1/8) is put in place:


And now for the other side...


The wings are now lifted from the plans and separated, and the root rib junk is finally fixed, just in time for the upper skin to go in place. But before the upper skins, that second leading edge layer is added. Muuuch better...


Everything is roughed into shape prior to joining the wings.


And with the wings joined, lookitthat!


This is the point where I find out that my only sandpaper is 200 miles away. Tomorrow will include a trip to the hardware store before I get to cover it and actually make an airplane.

 

[FAI-F1D]

So I hit into hyper build mode this evening...Sanded the wing, added the trailing edge bolt hardpoint, and glassed the dihedral joint. next added the wingtip hardpoint for a throwing blade. Next the whole wing was given a thorough coat of Balsarite, and I pulled out a roll of Polyspan, the choice in material for freeflighters building big things. Trouble is, I've never used it before. Went well enough, but it really does not like compound curves (fortunately I was prepared for that). After a nice coat of Krylon clear coat, I ironed out as many of the wrinkles as possible, getting a passable, but not perfect result.

Having done that, I tossed in a throwing blade, and installed the leading edge pin and hold down bolt. Nut being installed into the fuselage, we find a pretty sweet result, if a little bland:


Oh, I sealed the exposed wood surfaces with minwax for some water resistance. Not bad for my first R/C scratchbuild...


So what's a guy to do with a plane that already balances at a safe point (45% of root chord)? Off to field!


After a few tosses, I got the controls figured out (it's EASY to overcontrol this plane). It flies almost hands off, but is very nose heavy, and requires more nose up trim than is remotely appropriate. It also turns tighter than anything I've ever worked with. You can really crank it around without risk of stalling because the stall speed is sooo slooowww. I can't wait to put it in a thermal. Can't wait to get a 150 mah lipo, too, but that's another story.

I need to put some color on those flying surfaces, but for now, here's some video!

 

[Foam Addict]

That is poetry in motion. Beautiful!

Great job, and great flying too!

 

[510thousandths]

Okay.. i think I need 1 (at least).

 

[jhitesma]

Love it! Wish I could build that fast!

I do have a pile of balsa sitting here waiting for me to decide what to do with it. If only I had (or could find an affordable local source for) some carbon shafts....

 

[FAI-F1D]

Foam Addict, nah, poetry in motion would look a bit more like this:

Which reminds me that I need to build another freeflight DLG. It's been too long since I lost mine.
Here's another great video to whet your appetite:

510thousandths, yeah, I'm convinced now that everyone needs at least one. Some people understand this better than others:


jhitesma, you don't want arrow shafts for a model this small. My advice would be to use a 1/8" CF tube (called for on the original plans, actually). Doesn't have to be a particularly high quality one. If you can find a 3/16" thin wall, that's even better, and actually lighter than what I used. Most hobby shops carry the 1/8" tubes for about 6 bucks, and that's long enough to make two booms and have a little left over. You use the same size for the wing spars. If you want to get really fancy, of course, there are some really nice booms out there, and some only cost $10-12. If you really want to plunk down money, Stan Buddenbohm sells FF DLG fuselages that with a little modification, could be great for a sub-1m RC glider. Some of the ones out there are already wide enough to fit HS-55 servos, so a little orangerx 4 channel receiver would fit right in the slot for the DT timer, and you'd just need to hollow out a little extra for the second servo. Personally, I think that for personal use, those are a lot better of a setup that what's seen on most RC DLG's, being much slimmer in profile (a function of the F3K nose radius rules, I believe).

 

[jhitesma]

Oh, wait those are only 1/8" Looked bigger for some reason, hard for me to judge scale in some of these build photos sometimes

I may actually have some 1/8" carbon tubes laying around from my kites...may have to dig out the kite parts bag and see what's hiding in there this evening....

Sadly my local hobby shop options are extremely limited. When I first moved here I was into RC cars and the local hobby shop wasn't - at least not the kind I was into and few of the bits/pieces they carried transferred over. They did have quite a bit of balsa plane stuff but at the time I couldn't afford to get into planes. Either way the "shop" was really just a corner of the "owners" parents gift shop for their other enterprise and since he had gone off to college it was very neglected. They'd order bits if you wanted but the prices and times were no better than just going mail order. (and this being when the internet was just starting to take off on-line ordering wasn't very effective...though I did order a Kyosho HOR bike from overseas around that time and got my first taste of multiple month long shipping!) But that shop closed down completely a few years later and until about a year and a half ago we had no local source for hobby supplies other than Michaels and their very limited supply of Revel balsa and a few xacto blades.

About two years ago though the RC car thing hit town again and someone started up a mobile hobby shop that showed up at the local track - but they only had car parts. After 6-9 months though they opened a retail shop and expanded from just cars. They pretty much only carried Horizon and some GreatPlanes/Dubro stuff though at crazy markups. Then a year ago they moved into a newer bigger building and expanded again. They've got more plane stuff but it's still very limited - their focus is still mostly cars/trucks, and I've yet to spot any carbon tubes. I'm sure they could order some...but it wouldn't really give any benefit over ordering online. I may have to go check it out though to see if they've got any since they do seem to be increasing their aeronautical stuff slowly but surely. We do have a large active aeromodelers club with a really nice facility (paved runway, shade structures, port-a-pots, gated but 24/7 access for members.) But like most things in this town it's mainly active in the winter and dominated by retired snow birds who are resistant to newer stuff. Their membership is also a bit out of my current price range ($100 initiation fee, AMA membership required and another $60 or so annually for the club. Not unreasonable for what they have...but more than I can really spend right now especially since there's so much open desert where I can fly at zero cost.) On the other hand with the Yuma Proving Ground here starting to do more and more UAV testing for the military we're seeing more and more local interest in FPV. We actually have one of the military's top drone pilot trainers in town and the found him because of the large scale 3D flying he does with the club. One of these years I'll probably end up joining...

I kind of got off track there....

Yeah...where's that bag of kite bits.....

 

[xuzme720]

Wow, 1/8" for the boom! That is tiny, and weirdly I have some on hand, for the same reason as jhitesma...
Well, kites and my packrat habit. I tend to buy stuff that I might be able to use even when I don't have a use for it...I usually manage to find a use though! You can always use CF!

 

[FAI-F1D]

Well, just be glad you don't build free flight...literally 95% of what I need is not available in hobby shops. I was fortunate to obtain a near lifetime supply of indoor-grade balsa for next to nothing recently, so that helped, but for the average person, there are only three people on the planet who can supply you with that type of wood. Covering for the ultralights is available from a single source (we'll be in a pickle when he runs out of it, too), and rubber is available through select online sources. Winders? Ha! Only one person in the world is making indoor winders right now (I was privileged to help in the development process), then there are the hand made rubber strippers, balsa strippers, etc. Props are scarce, timers just got much harder to get thanks to a2z corp closing down (read that as a "take that you slobs" jab from the owner who engineered a real supply shortage for the FF world when we told him that his employees weren't sending us what we ordered).

Moving on...people who are satisfied with RC models are fortunate. Us purist, research obsessed free flighters have a cheap, but difficult to supply hobby. It's worth it though...

Oh, did I mention that one hard jolt was enough to kill one of the servos in my Bug? Yeah that frosted me over but good. Replaced it with a 6 g Cirrus that definitely acts like a higher quality product. We'll find out this afternoon. Hopefully I get me some smaller batteries at the same time.

 

[FAI-F1D]

Well no photos, but I had a few nice thermaling flights this afternoon, though nothing spectacular. The Bug flies quite nicely, and everyone who has seen in fly seems impressed. Unfortunately I got that one-last-flight-itis disease, and the battery chose that moment to disconnect on launch. I presume something else kicked in, but I found myself with a downward arcing plane and no elevator control. Needless to say my wife literally dug the nose assembly out of the ground, and there were splinters everywhere. No damage to the electronics, though, and the damage was limited to a loose stabilizer and shattered pod, which has been mostly pieced back together. It should be flying again tomorrow, but now I have a nice crash story to go along with my first R/C scratchbuilt.

 

[Joker 53150]

Are the Bug plans only available for purchase or are they available free? It appears that RCM is/was the only source for them, but there are hundreds of posts regarding people not receiving their orders. I don't know if they've taken care of that and are shipping again or not, but don't want to throw away money.

 

[FAI-F1D]

Are the Bug plans only available for purchase or are they available free?

Here's the skinny on the plans: you have a lot of options. The original plans are supposedly still available, but are now outdated. There are three versions out there now that are adapted for discus launch. All are available from the BugHLG group on Yahoo. I could be wrong, but I think you don't even have to join to download the plans. What's of note: There is an X-tail Bug, a revised X-tail bug for the newer electronics, and a 34" LightningBug. I made the mistake of building from a set of European plans for the V-tail Bug that had a lot of errors in the rib templates. The fuselage templates worked fine.

I'm going to send you to the yahoo group rather than post the plans here, even though they appear to be public domain, simply because I saw another person posting stuff of that nature on another forum only to get absolutely flamed by several people.

There is a .pdf in the files section of the yahoo group which includes not only the build article, but also a bunch of data on bug modifications. I highly recommend reading through that.

To add a little bit more, there's another design out there, the MiMi, which is a bit larger and designed to be built up or entirely sheet balsa, and it's supposed to be a real performer, and just as easy to make as the Bug. One of the F3K guys out West has won at least one contest with it, so it's not just a beginner's airplane.

Final note: my Bug has been repaired and is ready for more abuse this evening.