Jun 25, 2019, 07:29 PM
Foamy and Glider fanatic
Discussion

Building a motor glider from wing, elevator, & rudder from a bungee launch glider

So I'm minding my own business flying at my soon-to-be-new RC club's field when one of the members pulls up and starts unloading all these planes with crazy good price tags on them. He wants to unload some of his old RC planes because he's getting ready to move.

Hearing how crazy I am about gliders, he basically gives me a bungee launch glider who fuse is cracked. The wings, elevator and rudder are balsa and monocoat. Later at home I determine that the fuse is too far gone to repair and I ditch it. But the rest is great!

So I get to thinking,.....how about I use these excellent parts to make a "small" 3 channel motor glider?

Each wing measure 31.25" [707mm] long with a 7" [177mm] chord. They each weigh about 74gr. Together the wings measure 60.5" [1537mm] and weigh 148gr. If my math is correct the dihedral angle is about 18 deg (4.375" rise over 13.75")

The elevator measures 15 1/4" [387mm] long x 4 3/4" [121mm] wide. The rudder measures 4 3/4" [121mm] tall x 5" [127mm] at the base

My thought was to make a fuse out of MPF reinforced with some carefully placed CF rods. I chose this over a CF arrow shaft because I wanted to make it easy on myself to attach the wings, elev, & rudder to the fuse. Plus I don't want to spend an eternity fabricating saddles to make mounting all the components to a CF arrow shaft possible.

Now for my questions

Is there somewhere online where I can get an idea how long to make the fuse and where to mount the wings?

Images

Jun 26, 2019, 03:52 AM
An itch?. Scratch build.
Just a suggestion, but a 'pod and boom' fuselage is quite easy to construct.

The pod could be balsa or foam, the boom can be from section of a cheap fishing rod, they don't have to be carbon.

Here's a post that includes pictures of mine --- https://www.rcgroups.com/forums/show...49&postcount=2

If you want the best of both worlds, a pure glider for tow line/bungee, or an add-on for electric powered, see pictures below.

.

Images

 Jun 26, 2019, 04:44 AM Foamy and Glider fanatic Thread OP Thanks for the input. I've got a bunch of CF arrow shafts. So if I was to go this route I'd probably use one of them. I guess I'm having a hard time picturing how to make something that will allow me to attach the elevator and rudder to the CF rod. I guess you box in the end of the shaft with some balsa and epoxy that in place? That way you get a flat spot to anchor your components. Hmmmm, why couldn't I just drill the appropriate sized hole in a thick enough piece of balsa and epoxy it in place. ...
 Jun 26, 2019, 05:59 AM treefinder Your aspect ratio is a bit smaller, but span is same as the OSG, so you could look at it's templates to get an idea for fuse length. Wider fuse than OSG though as it is easier to get fingers and servos in, and the original glider was sized to fit the readiboard. While pod and boom looks cool, and probably is lower drag, overall, as you are pondering, it seems more of an engineering exercise than box section foam. Depends on what you want, quick and dirty, or elegant!
 Jun 26, 2019, 08:52 AM Foamy and Glider fanatic Thread OP Thanks for the info about the OSG Glider. That'll help me out a lot. I'm going to look into making a foam fuse. If it turns out too bulky I can work on a pod and CF boom version. But hell, that may change mid way through the design! I've had that happen before...... I'll keep you all posted.
 Jun 26, 2019, 09:01 AM treefinder Ain't that the fun of it all? I feel sad for those guys who feel they have to follow some other guy's plans exactly! Making it all work is the best fun.
 Jun 26, 2019, 11:23 AM Space Coast USA
 Jun 26, 2019, 02:45 PM Foamy and Glider fanatic Thread OP Hoppy, thanks for the link! I totally forgot about Ed's tutorial on this subject. This is EXACTLY what I needed to get going. I'll try to make a layout tonight in CAD using the dims from the OSG and Ed's joining plate technique
Jun 26, 2019, 09:02 PM
Sokol

PHOTON Motorglider , ExperimentalAirlines

look at the photon glider for ideas

 PHOTON Motorglider - Intro Video (13 min 0 sec)

fuselage building video
 PHOTON - Fuselage part 1: Nose Taper (17 min 56 sec)

 PHOTON - Fuselage part 2: Joining and Wing Mounts (16 min 25 sec)

 FOAMBOARD FUSELAGE TUBES (18 min 33 sec)
Last edited by JureZ; Jun 26, 2019 at 10:00 PM.
Jul 03, 2019, 06:59 AM
Foamy and Glider fanatic

Designed the "pod"

Just wanted to update the group on my progress. I tend to start a project, then it languishes while I hash out the details. I'm sure NOTHING like that happens with you guys,....

Using the dimensions of the OSG I was able to determine that the overall "fuse" length should be 26" and the wing mounted 5" back from the motor mount.

As you can see in my layout below, the pod will be about 14" long. I may shorten that a bit in order to reduce the length. Looking at the layout makes me think I made it too long/big. I need to watch Ed's video again and get the proper orientation for the boom "mounting plate". The overall shape will be reminiscent of the OSG but be constructed using Ed's "fuse tube" method.

I made the inside of the fuse cavity 2" wide in order to give me room for the electronics and allow me to use 2" thk foam at the nose for a monoblock. But like everything else, this is subject to modification. I may make it slimmer so I can use 1 1/2" thk foam. I plan on using Jack's dowel trick on the motor 1/8" plywood mounting plate to give it a nice strong bond to the foam.

I plan on using a blue wonder style motor (can't remember the Kv right now) , 20a esc, and 6" (8"?) folding prop that were meant to go on a similarly sized OSG. In order to cut down on the weight I plan on using a 450mAh 2S

Once this fleshes out more I can get an estimate on the weight. I may turn out that I need to go with a bigger motor. But I won't know until I start getting the design finalized.

Well, what do you think?
 Jul 05, 2019, 01:15 PM Foamy and Glider fanatic Thread OP For some reason the original layout I made didn't get attached to the last reply I made. No big deal. I revised it and made an updated version in SolidWorks. It's much easier for me to see how things go together in 3D rather than in 2D. I'll post a screen shot once I get the model completed
Aug 24, 2019, 08:25 PM
Foamy and Glider fanatic

All finished and videos of a successful maiden flight!

I finished the build on this a while ago but didn't get a chance to maiden it until after I got back from vacation. The fuse is a mix of the OSG with bits and pieces of stuff from Experimental Airlines (EA). I used MPF for the fuse and covered it in vinyl packing tape. The adapter plate was made from 1/16" plywood and the boom was from a CF arrow shaft. Rather than use the existing tail feathers, I made a new set out of MPF and was able to take advantage of the EA technique that uses foam tape and 3/4" x 3/4" corner guard. I also used the servo mounting technique from EA and that worked out great.

The motor is a an Emax 2822 1200KV and I threw a 20A Turnigy Plush ESC with SBEC in as well. I built this to fly off a 450mah 3S Lipo but I forgot to bring my JST to XT30 adapters with me. So I had to fly with a 1200 mAh 2S Lipo

 Franken Glider 08 24 2019 (1 min 48 sec)

I am VERY pleased with the way this came out and was equally glad that the gent who gave me these parts got to see what I made out of his old broken glider. This baby just FLOATS and because t is very light, will ride a thermal all day.

Images

 Aug 24, 2019, 09:52 PM Sokol nice ! , just stay clear of the fence during landing ...
Aug 25, 2019, 06:19 AM
Foamy and Glider fanatic
Quote:
 Originally Posted by JureZ nice ! , just stay clear of the fence during landing ...
I was actually about 6 feet away from the fence when it landed. Never even came in contact with it.
Aug 25, 2019, 07:58 AM
Sokol
Quote:
 Originally Posted by Blacky's Boy I was actually about 6 feet away from the fence when it landed. Never even came in contact with it.
both you and your plane did great , congrats !