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Scratch Designed/Built Sailplane Fuselage

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Old 12-01-2012, 08:36 PM
  #76
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Default RE: Scratch Designed/Built Sailplane Fuselage

Yeah there's light at the end of the tunnel *smile*

Picking right up were we left off yesterday, setting up the dowel leading edge...



More progress...



Here's some pieces that'll makeup the root area. Going to layer balsa - light ply - balsa...



Root area built up & reinforced...



When I did my balance test the other day it took 4 oz on the tail-boom to make her sit level. It looks like we're well within limits so far...



Added some fancy tips...



Seeing what she looks like...



This tail feels sooo much stronger than the original, loving those diagonal ribs.
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Old 12-02-2012, 09:45 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

More overly engineered fun...
I've been thinking about how much abuse my sub-fin is likely to take during landing, especially if I catch a wing-tip & the tail hits sideways...



I've decided to build in a little insurance, a sub-fin that'll bend instead of brake...



As you can see its made from two pieces of ply. Holding them together will be some coat-hanger wire. It's soft enough to bend if she hits hard, hopefully absorbing the impact instead of just snapping off...



I layered carbon-fiber either side then drilled holes...



Some Kevlar thread & plenty of epoxy holds the wire in place...



Added light balsa on the sides to hide the uglies...



That takes care of that, next is the lower fin part...



More carbon-fiber, mostly to keep the wire in place but also for ding protection...



Sanded the other piece to a nice smooth shape...



More progress on the sub-fin...



Test fit. Note I added a slight bevel where the two pieces join. Like a rudder's hinge, this should allow the fin to bend if need be...



Well that was fun...

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Old 12-03-2012, 05:48 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

That ought to work.
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Old 12-06-2012, 06:03 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

I hope so.

Time for another balance test
All this stuff needs to fit in there...



Yes! It fits...



Slung the tail over the boom & stuck her up on the balance stand. It looks like we're a tad nose heavy...



I'm okay with nose heavy at this point. The tail still needs to be glued on there & covered, push-rods & other hardware added, that'll all add weight to the tail.

110°
Happy with the balance I set up a jig & started gluing the V-tail in place...



Lots of measuring, eye-balling & more measuring...



Added a strip of heavy glass cloth...



I'll let this setup over-night, should be able to get the sub-fin on there tomorrow & finish up the glass reinforcements...

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Old 12-07-2012, 10:23 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Time to turn this V-tail into a Y-tail...



Added some feather-light 3/4oz glass...



Yeap that's one odd looking tail alright...



I need to mount up the ruddervators still but we have a tail... yay!

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Old 12-08-2012, 12:29 PM
  #81
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Default RE: Scratch Designed/Built Sailplane Fuselage

Airframe complete!
Time to stand back & take a look...











There's still plenty to do so back to the workshop...
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Old 12-08-2012, 03:04 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Sad they don't make a transparent white covering. That would look sweet.
Great work Nodd. Plane is looking sharp.
Have you got colors picked out yet?
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Old 12-08-2012, 03:10 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Ultracote comes in both clear & white transparent covering. I'm leaning towards using transparent film on the open structure areas, playing around in Photoshop right now with some design ideas. I'll post those once I'm done experimenting.
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Old 12-09-2012, 03:45 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Hi Nodd. Been following this all along including previous prototype. This is a beautiful plane you created Nodd and can't wait 'til the maiden.
Thanks for entertaining us with your projects. Great job!
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Old 12-09-2012, 04:29 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Nodd,

are you going to offer plans or laser cut parts for this ? very sweet looking.

S.
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Old 12-09-2012, 05:29 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Quote:
ORIGINAL: PatternPilot

Nodd,

are you going to offer plans or laser cut parts for this ? very sweet looking.

S.
I'm a little reluctant to make any promises about plans just yet. I said I'd make plans available for the first version & then the wing broke in half on the 5th flight. While I'm confident those design flaws have been addressed in this version, it's a tad too early to be talking plans & short kits. If this design proves to be successful however, yes I'd like to distribute plans & whatnot.


Quote:
ORIGINAL: thepamster

Hi Nodd. Been following this all along including previous prototype. This is a beautiful plane you created Nodd and can't wait 'til the maiden.
Thanks for entertaining us with your projects. Great job!
Glad you've been enjoying my workshop adventures. Its always nice to hear folks are following along.
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Old 12-09-2012, 09:14 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

I still cant quite figure out what the little wingtip rudder things actually do.
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Old 12-09-2012, 11:47 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

If you feel like giving yourself a headache here's an excellent article on the science behind winglet design.

I did lots of research into winglets & although I now have a fair understanding of what they do, I've accepted that it's beyond me to create a truly beneficial set of wingtip fins. The math & testing required is way over my head. In a nutshell, if designed correctly they help reduce drag by better directing the cross flow of air moving around the tip. Every airframe is different however so one winglet design doesn't fit all. Unless the winglet is "tuned" specifically for its wing, its presence will only serve to increase drag & lessen performance. The dinky little winglets on my plane were scaled down so as to not cause much of an effect either way. They're essentially wing-tip ornaments. I just like the way they look.
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Old 12-10-2012, 03:05 AM
  #89
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Default RE: Scratch Designed/Built Sailplane Fuselage

I couldn't agree more about wingtips! How about silk for the finish? Mine is glassed with 3/4 oz and painted with clear monokote paint, idea courtesy of Mr Paul K. Johnson, owner of airfieldmodels.com. But with the open bays forget glass. Still, I think the plain silk and dope would look fantastic, like transparent white
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Old 12-10-2012, 10:31 AM
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Default RE: Scratch Designed/Built Sailplane Fuselage

I think its pretty common, at this point in a balsa build, to become fixated on the bare-bones structure. There's something innately appealing about wooden framework. Most RC sailplane wings these days are either composite or foam so there's definitely something special about an old school rib-n-spar setup. I should just move on & cover up the airframe but like you I'm currently leaning towards transparent covering so I can show off the structure.

I like what you did with your wing, that finish really highlights the wood's grain. You're right though, that's not ideal for an open structure like mine. I have actually come up with a plan for the covering & interestingly it does involve areas of transparent white (Ultracote). I guess great minds think alike *grin*.

On a similar topic, I plan to add black covering to the wing's sheeted underside to help improve visibility at altitude. That'll help when she's specked out.
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Old 12-11-2012, 03:46 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

I know, transparent yellow, blue, and solid red.
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Old 12-16-2012, 12:59 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Must be snowing in CT.

Great time to cover a model.
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Old 12-16-2012, 05:36 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

It almost snowed here yeah, a couple of degrees colder & it would have. I usually fly on Sundays but the crappy weather kept me grounded. On the upside that gave me more time to work on the sailplane. I even had a squirrel come check out my work...



And then I carved a bloody great gash in the side
Apparently I spaced on the need to actually control my fancy Y-tail. Some push-rods would have been nice. Oh well, too late now. Time for some minor surgery...



Glued the push-rods in place...



Replaced the fiber-glass...



And then I cut bloody great holes in the side too
Yeap more carnage. She needs to breath so I added some cooling holes...



External push-rods
Again if I'd planned ahead a little better I could have run the push-rods down inside the tail-boom but space-case here was only thinking three or four steps ahead instead of 10. The push-rods will run externally, oh well...



I used cotton thread every few inches to secure the push-rods then added a little glue to lock it in place...



Paint

A few coats of glossy Krylon & she's looking good...



Wonky servos
You'll notice my servo tray here looks a little odd...



The V-tail servos are mounted diagonally to allow the control arms to be centered away from the narrow fuselage's sides...



I also managed to squeeze the motor, ESC, SBEC & receiver in there too...



Feels good to have the radio installed. Now I need to figure out how to squeeze a LiPo in there too.
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Old 12-21-2012, 07:52 PM
  #94
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Default RE: Scratch Designed/Built Sailplane Fuselage

Covering Time
My Ultracote finally arrived so time to start covering these bare-bones...



The top of the V-tail is gray. For the ruddervators I'm using transparent white...



Before you all start worrying that gray & transparent white will make her hard to see at altitude, I'll be covering the underside with black...



The black contrasts well with both blue & white sky...



I'm liking the transparent white, looks great back lit. It shows off the structure nicely without being overly see-through...



The wings will follow the same gray & white, black on the bottom format. Sounds a bit dull? Fear not, I have some colored accent graphics in mind that'll spice things up a little. I'm hoping to get the wing covered this weekend.
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Old 12-22-2012, 03:33 AM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Quote:
ORIGINAL: Nodd

Before you all start worrying that gray & transparent white will make her hard to see at altitude, I'll be covering the underside with black...

The black contrasts well with both blue & white sky...



That's an interesting pair of pictures. Did you take them with a camera, or create them with software?

I was flying my all white glider a few days ago. When it gets about half way up (as shown in your example pictures), it looks more like the right half of your example. Glider guys have been specking out for a very long time. I specked out in a similar sky the other day. It was a sort of 2 black specks for awhile as it went up until it was a single black dot. Even my transparent wings go black at altitude. If all of them didn't go black, then we couldn't have been specking out everything we flew since a long time ago.

They obviously don't change color with distance. They certainly don't go black. But our eyes think they do. The cones in our eyes lose sight of the suckers and the rods are left to paint what they can see on our brains. And rods only have black paint to paint with. That's the theory anyway. Good thing is that it works that way in practice too. Otherwise, nobody would ever be able to speck out all those non-black gliders.

BTW, sorry to spin off, because the thread is awesome. It ought to teach a lot of lessons to a lot of people.

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Old 12-22-2012, 10:21 AM
  #96
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Default RE: Scratch Designed/Built Sailplane Fuselage

Yeah most of the glider folks I fly with all swear that dark colors or black on the underside of the wing is the way to go on a sailplane. You're correct, the eye has two sets of light collectors, low resolution cones that see color & high resolution rods that see in black-n-white. So once your plane starts to get way up there, colors start to fade as your eye's color-blind rods take over. I have one sailplane with bright orange on the wing's underside. It's really easy to see at close range but it blends with the sky at altitude. At extreme range its all about contrast, not color. Dark colors silhouette better against a bright sky Vs light colors. I made up this chart of Ultracote samples that illustrates how some colors appear darker at range...



The interesting thing about this is bright colors that are easy to see at close range are actually worse at long range.
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Old 12-22-2012, 07:20 PM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Control Surfaces
I picked up a set of control horns today & got down to hooking up the V-tail...



I've tried all sorts of hinging techniques, not sure if I'm just getting lazy but to be honest, good old tape rules for simplicity & functionality. Zero friction, zero hinge gap, zero fuss...



Soldering the clevises to my push-rods. What's with the towel you ask?..



Here's why we need the towel. I've had solder burn right through my covering one too many times...



A big nine foot wingspan & yet I need to make tiny fiddly little stuff like this that I can barley even see...



These small hardwood spacers keep the push-rods from flapping around, important for slop free linkages...



Yay we have a functional tail!..



Programming the V-tail mix...



I'll probably add some differential to the tail but for now I'm starting out with everything even.

And with that the tail is done...

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Old 12-23-2012, 08:35 PM
  #98
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Default RE: Scratch Designed/Built Sailplane Fuselage

Looks good, cant wait to see the maiden.
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Old 12-25-2012, 06:28 AM
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Default RE: Scratch Designed/Built Sailplane Fuselage

To make the build faster if your going to sell plans etc. It would be great to have the fuse pod as fiberglass..... Might be able to help you with that

Merry Christmas to all....

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Old 12-25-2012, 08:42 AM
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Default RE: Scratch Designed/Built Sailplane Fuselage

Happy Holidays  to you and your family Nodd and thank you for this awesome thread.
The plane is looking great. Can't wait to see the wings covered.
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