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"Bug" DLG

TexMechsRobot

Posted a thousand or more times
#81
I just found this thread not knowing that the Bug is a very common and well tested plane. I had intended to make mine an HLG but Craftydan has me thinking about the DLG version. I've built balsa before so I do know some stuff but I'm in the middle of this build and this would be my first DLG. What should I know?

I'm working with the original HLG plans that are hosted on Outerzone and just found the plans on page 3 of this threaad for the x-tail version. I've finished the fuselage and haven't put any glass or reinforcement on it at all. I also haven't placed any electronics although I do have them purchased.

My questions come down to reinforcement and how to build it so it can handle the lateral stresses of DLG launches. I'm planning to build the tail out of 3/32 balsa with .75 oz glass on both sides of all surfaces. I also plan to do a spring-pull setup for the control surfaces. How should I mount these so that the don't rip off on the first throw? Should I do something other than 3/32 glassed balsa?

How do I mount a blade or peg in the wing tip so that it doesn't rip out? Does it go at the end of the carbon spar? Should I modify the wing build to account for the launch stresses?

I think that's all of my questions to this point. Thanks for any help!
 

FAI-F1D

Free Flight Indoorist
#82
I just found this thread not knowing that the Bug is a very common and well tested plane. I had intended to make mine an HLG but Craftydan has me thinking about the DLG version. I've built balsa before so I do know some stuff but I'm in the middle of this build and this would be my first DLG. What should I know?
Make sure the boom is stiff enough (I used the front half of a Goodwinds boom that starts at 1/4" and tapers to something...smaller). I wouldn't go with a pultruded boom--been there, done that.

Also make sure the wing join is wrapped with glass cloth. A lot of strength for minimal material is available if you do that.

Also, you need to wander through these threads:
https://www.rcgroups.com/forums/showthread.php?1425492-Bringing-back-the-Bug-DLG
https://www.rcgroups.com/forums/showthread.php?840763-Free-drawing-mini-DLG-1-meter

I'm working with the original HLG plans that are hosted on Outerzone and just found the plans on page 3 of this threaad for the x-tail version. I've finished the fuselage and haven't put any glass or reinforcement on it at all. I also haven't placed any electronics although I do have them purchased.
Reinforce the fuselage by coating the entire exterior of the balsa with a layer of 1/2 oz glass cloth. Use epoxy for this, just as you would for the wing. Do not use too much epoxy--just enough to fully wet out the glass.

My questions come down to reinforcement and how to build it so it can handle the lateral stresses of DLG launches. I'm planning to build the tail out of 3/32 balsa with .75 oz glass on both sides of all surfaces. I also plan to do a spring-pull setup for the control surfaces. How should I mount these so that the don't rip off on the first throw? Should I do something other than 3/32 glassed balsa?
1/16" C grain balsa for the tail surfaces, as light as you can get it; no glass cloth needed on the tail unless you want a very small amount on the bottom of the vertical stab for scuff resistance. Hence the need to use a 1s 300-350 for your power supply. Keep the nose and the tail light. Slide the rx and battery around to set the CG, only adding weight if that doesn't get you there.


Look up pull-spring methods on rcgroups. I think there are a couple of examples in the MiMi thread. You don't need anything stronger than .015" wire on this model, especially if using 5 gram servos, which is what I used on mine. I could have gone lighter...

Remember that the control horn for the rudder goes on the opposite side from the throwing peg. Very important. Use a blade rather than a peg for throwing. A carbon strip .015-.020" thick and 1/2" wide cut to about 1 1/2" long makes a great throwing peg for starting out (round the corners off for extra comfort). If you use a carbon tube you'll quickly learn how uncomfortable they are. I used 1/64" plywood for the wingtip reinforcing for the peg. Worked great. My blade was actually only .010" thick and withstood full power launches without incident (I throw hard enough that I've broken wings and tailbooms of small DLG's).

As mentioned, I throw quite hard; the final Bug version I showed in this thread flew without incident once I switched to the tapered boom I mentioned. This model taught me the art of DLG and remained a satisfying flier until I sold it last year. I got a couple of additional offers high enough that I really should consider building and selling these.

One final though: I covered the wing with polyspan and heat shrunk it. This produced a fantastically rigid wing. It does provide a launch advantage over a plastic covered wing because of the extra rigidity. The end result is a model that is competitive against many of the lower end two channel composite DLG's in this size range.
 

TexMechsRobot

Posted a thousand or more times
#83
Thanks for the help.

I have no idea if the boom I bought is pultruded. The plans recommended 3/16" carbon fiber tube and I picked up a piece at my LHS.

Regarding using epoxy for the glass cloth: I picked up some 20 minute epoxy and Craftydan mentioned that I should thin it 50:50 with 100% alcohol so I plan to do this. Is any compression required when I glass the fuselage or can I just wrap it, soak it, squeegee, and let it dry?

Will using oil based minwax on the tail surfaces prevent warping? I can't seem to locate any c-grain balsa at my LHS so I need to make my a-grain rigid enough.

Do you put the 1/64" ply on top and bottom of the wingtip? Do you cover the whole wingtip or just the immediate area around the blade?
 

TexMechsRobot

Posted a thousand or more times
#84
I seem to be failing to take pictures lol. I have the right wing pretty much done but I didn't purchase a long enough carbon tube for the spars so I have to wait for it to arrive at my LHS (next Wednesday). I did get the nose cone built and shaped and I have laid the 0.75 oz glass with 20 minute epoxy thinned with 99% alcohol. It's drying now and taking it's sweet time. I also cut out the fin and stabilizer from 1/16" A-grain balsa and coated both side with a thin layer of oil based minwax. I'll probably glass the bottom leading edge of the fin as suggested to help with landing damage.

I'm also going to have to locate the .020" carbon strip for the blade and I think my LHS will come to the rescue again there. My plan is to use 1/64" ply to reinforce the tip top and bottom as suggested. I have some Solite that I plan to use to cover the wing. I've never used it before and I think this is a pretty good application to try it on. My goal is to have it flight ready by the 25th when I go visit my dad. He's get a kick out of it if the weather cooperates. He lives on a small hill that faces a bay and frequently has 10 mph winds directly into the hill. You can watch the seagulls and bald eagles hovering in place about 30-60' above the rise as the slope soar like experts. I'd like to see what this can do in that situation.

I'll post pictures at some point :)
 

TexMechsRobot

Posted a thousand or more times
#85
So here are some pictures.

Lemon Rx 6ch lite receiver and battery choice.
IMG_2164.JPG

I have no idea what this port is for. Any ideas?
IMG_2166.JPG

I decided to put a strip of .75 oz glass on each side of the hinges for the rudder and elevator. I had cut them before I made the decision to do this.
IMG_2168.JPG

A couple of shots of the fuselage.
IMG_2170.JPG

IMG_2172.JPG

I can't finish the wing until I get the .125 carbon tube and .020 carbon sheet for the blade. I won't get those until Wednesday at the soonest.
IMG_2174.JPG

IMG_2176.JPG
 
Last edited:

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#86
Hey Tex,

Beautiful work so far :)

The port on the RX is for connecting up a Satellite for diversity -- overkill on something like a Bug, but you can ignore it.

So I see you're glassing the hingelines . . . what's the plan for the hinge material?
 

TexMechsRobot

Posted a thousand or more times
#87
I was just going to use blenderm tape. I have enough wood to redo them and am already considering it. You recommended glassing over rip stop and it seems like that would be pretty strong. Thoughts?

Thanks. I'll ignore it.
 

FAI-F1D

Free Flight Indoorist
#88
You people that have a neat workspace make me sick. There's just something not right about that.

Nice plane by the way. The 3/16" tube for the boom should work well initially, and you'll be able to learn on it. Once you learn to throw good and hard you'll find yourself wanting to retrofit it with a stronger (and probably lighter) boom.
 

TexMechsRobot

Posted a thousand or more times
#90
The only carbon strips I could find were .019" thick by .118" wide. I cut cut two 1.5" lengths and then put them side by side to get the size I need. Would this work? What's the best way of fixing them to each other so they form flat blade? I could see epoxy and wrapping them in fiber glass may do the trick. Thoughts? Should I just buy a ready made blade?
 

FAI-F1D

Free Flight Indoorist
#91
I could see epoxy and wrapping them in fiber glass may do the trick. Thoughts? Should I just buy a ready made blade?
That's what I do. ;)

I can assure you that the .019 thickness is plenty; it's really strong.

When you want a comfy blade, buy either a Snipe blade or contact Eitan through rcgroups and by the comfort blade. Craftydan uses the latter is it's really, really nice.

I really wish you weren't on the opposite end of the country...I'd like to fly with you. Coming to Flite Fest this year?
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#92
one other idea . . .

you're building composites, take advantage of compositing materials ;)

Take a look at the manual for the Mountain Models DL-50. About 1/2 way through they step through building up a wingtip peg using a thin (1/16x1/2"?) rectangle of birch ply then wrap vertically with carbon tow.

Mine came out looking as ugly as homemade sin, but that's probably more to do with too little experience at the time and too much epoxy. IIRC, they did 6 T-shaped wraps under-up-and-over the wooden peg and wingtip. The DL-50 needs that much carbon, but it's overkill for the bug. I could see lining such a ply peg with half that . . . or even a 1/8"x1/2" balsa rectangle with the CF strips on both sides, then wrap in the middle and ends with tow or fishing line to keep it from fraying apart.

I also have some 1x10mm rod stock that I could lop off a piece and drop in an envelope for you, if you're interested -- not as DIY, but it's got enough meat you could grind in finger pads . . . just don't breathe the dust ;)
 
#93
Hello-
Watching this thread has renewed my "bug" for a DLG. Back when David was tossing his on the show, My son and I started a project to build 2 (MIMIs) in preparation for a vacation trip. Time got in the way and we abandoned mine and pushed his fuselage and a semi-built-up wing to completion. We struggled a bit keeping the pull-strings tight on the servo arms and the space was tight for the HT-500's and equipment (lots of tinkering). We had fun with but never achieved what I would call a "launch". Your flights are spectacular! The wing is still in good condition and I think that I have may of the challenges we had with the first effort resolved, and the second fuselage is nearly complete. I am wondering if there is a resource for preparing the "launch settings".
Any advise or direction is appreciated. Thanks-
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#94
I haven't built a Bug so I can't give specifics for her, but for trimming out a new DLG, I start with glide tests. LOTS of glide tests.

I want her trimmed perfectly before I give her a hard toss . . . that , and after spending sooooo much time building one out, it's satisfying to see one settle in to a long slow glide :)

Preferably over some thick grass, get your CG balance happy, and trim consistent over hard and medium chuck-glider tosses. Double check elevator and rudder authority -- a light touch should show a measured response. For a model with flaperons, I'd set those up and tune the trims and flap-elevator mixes, but you don't have to bother with that on a Bug.

Once I'm happy with the trim, I'll program to a momentary switch on the radio an elevator offset of up by a few mm. That should be enough that if it's kicked on mid-glide it will respond moderately -- we'll be hitting this at top speed, so it's response will be amplified . . . and you're ready to toss it :)

Give it a moderate launch, holding the switch during the windup and releasing it just a half step after it leaves your hand (timing takes practice). Don't go too weak in the throw -- some DLGs don't like that -- but full strength on an unproven airframe can get . . . interesting quick.

If the nose doesn't rise quickly enough on launch, but you feel you released the switch about the right time, program in a bit more "up" into your launch mix. If starts to loop on you, move the launch elevator down a bit, and think about your timing releasing that switch.

If it veers left or right, most of that is in your throw -- finger position on the blade right? Release timing in the throw good? Was your arm still straight when the plane left your hand? did you follow through? That's all about practice. If it consistently veers one way, and you can't seem to get the motion right to launch straight, you can add in a touch of rudder offset to the launch mix to bring it closer back to straight . . . but try to get as close as you can, as consistent as you can with practice before you add in this mix.
 

TexMechsRobot

Posted a thousand or more times
#95
I made a lot of progress on the build. I finished building the wing and built out the launching blade. More on that later. I covered the wing in Solite and plan to leave everything else as it is.

IMG_2181.JPG

IMG_2183.JPG

I built the blade with two 1.75" x .019" x .118" strips of carbon fiber glued side by side with CA. Then I wrapped it with a thin strand of kevlar thread and CA'd the whole thing again with thin CA. It seems strong but I really have no idea. I reinforced the top side with 1/32" basswood and the basswood grain is perpendicular to the balsa grain for more strength. I didn't put anything on the bottom because I was concerned about weight but I'm now wondering if I should have. Time will tell on that.

IMG_2185.JPG

IMG_2187.JPG

I wasn't sure how to accurately cut a notch in the carbon fiber boom to mount the tail in the traditional fashion so I chose the method you see below. It did add a considerable amount of weight at the tail and I think I have a slightly tail heavy glider at the moment.
IMG_2189.JPG

The battery and receiver are fully forward and I have room for ballast but I'd rather not use such methods if I don't have to. I don't have the servos yet (they're coming from China and are set to arrive some time in March) so there isn't really much I can do until I have those.
IMG_2192.JPG

I'm pretty happy so far but I think I'm about a month away from actually getting to launch it.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#96
Um . . . Tex . . .

Your rudder hinge is going the wrong way.

The control horn that pulls against the spring should be opposite the throwing peg, so unloaded, the surface should swing toward the peg.

You can probably reverse the direction of the spring (make the spring pull the hinge closed instead of swinging it open).


Otherwise . . . you've got a beauty in the making :)

While you're waiting you can tape the surfaces neutral and add on some ballast for the servos and you've got a fancy free-flight glider ;)
 

TexMechsRobot

Posted a thousand or more times
#97
I was going to pull towards the camera, down the port side since this is the side I mounted the tube on. I noticed that the plans called for it to pull to the starboard side but figured it wouldn't matter. Does it?
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#98
It does matter, but more on where the peg is than the "plans"

It's an odd effect, but I've seen it at work -- I put two pegs on my DL-50. Launch with the opposite peg it launches straight as an arrow. launch with adjacent peg and it nearly rolls inverted on launch . . . and that one is pushrod. It's worse on pull-spring (can't push a rope).

It's a feedback affect from the flex of the boom in launch as you release. There's a tremendous snap-back flex in the tail as the centripetal force releases the flex ever-so-slightly expands and shortens the linkages, moving the surfaces. Horn opposite the peg (on the outside of the spin) dampens the snap-back, adjacent to the peg (inside of the spin) amplifies it.
 

TexMechsRobot

Posted a thousand or more times
#99
Got it....

Then I'll have to find a way to modify it. Shouldn't be too hard. I can have the string exit the rod before it gets to the stab and I should be able to reverse the hinge. Even if I have to build a new control surface on the rudder, it's only a little balsa attached with blenderm tape.

Thanks for the "why" behind the placement. That really makes sense!
 

TexMechsRobot

Posted a thousand or more times
The spring I was using (.015" piano wire) coupled with my hinge method (blenderm tape) and the tail surfaces (1/16" minwaxed balsa with .75 oz glass on the hinge lines) proved a little finicky. The control surfaces were warping along the length under the strain of the spring and the tape wanted to shift forward causing the control surfaces to be offset just a little. I've since switched to just using a .015" piano wire as the pushrods for a traditional setup instead of the pull-spring method. The only thing I'm really waiting on are the servos.

I think I'm going to wind up with a tail heavy situation even after installing the servos forward of the CoG and the battery/rx all the way forward. I'll also be pushing 110g AUW once I get it balanced out. That's a little heavier than I was hoping for (shooting for 90g) but it just means it won't glide as well. I'm really building this to be a sloper anyway so a bit more weight could help the penetration. I'm not great at building light :-(

Regarding the servos, I ordered these knowing that they were coming from China and the delivery date was given as "Mar 7 - Mar 23". Yesterday, I decided to see if I could source them from somewhere else a little faster and found these .

I face palmed and then ordered them. I'll wind up with a couple of spares but I should be able to finish this project up a little faster now :)