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Scratch-building a new flying wing.

Old 06-23-2015, 11:39 PM
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mclarkson
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Default Scratch-building a new flying wing.

I love my P115 flying wing (cut by RCGroup's 'Papo') and have been wanting to create a similar wing for some time.


I built the little P1 wing to test out the idea of building a hollow foam wing with ribs.



That turned out pretty well, so I decided to try it on a bigger scale.

I recently realized that my P115 does not follow the 'official' plans. The wings are longer, and swept further back.


For this build, I decided to try to replicate my actual wing, rather than the paper drawings (which the P1 is based on.)

I started by picking an airfoil - again, based on my P115 wing - and cut out a number of wing ribs. I left the paper on for added strength and notched them in front to accommodate a balsa wood leading edge spar to be added later.


Gluing the ribs on the cut out bottom section of the starboard wing. I used Beacons 3-in-1. The wing also has its paper removed.


Next, I glued a section of 3/8" balsa to the leading edge. The balsa is rotated to present a corner, rather than a flat side, to the front.




I sanded this balsa leading edge to a smooth, round shape once everything was glued in place.

Last edited by mclarkson; 06-25-2015 at 06:38 AM.
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Old 06-23-2015, 11:47 PM
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I wanted to add lights for night flying. Rather than place them outside the wing, I attached them to the ribs inside the wing.


There are four sets of six LEDs inside each wing.




The same thing inside the port wing.


Rather than try and measure things exactly beforehand, I cut a piece of foam larger than needed. (I'll trim it to fit, later.) I stripped the paper off and glued it to the balsa wood spar at the front.


Once the glue had set, I wrapped a length of white duct tape around the leading edge. Then I glued the top down onto the ribs.


The finished port wing.


The lights shining from inside the port wing.


Finally getting an idea of the size and shape of the finished product. (The addition of ailerons will make the whole thing a couple of inches longer.


Testing the lights on both sides. You can clearly see that all my LEDs are not equal. I wish I could remember where I’d purchased which lights, ‘cuz that one section is WAY brighter than the others.
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Old 06-24-2015, 08:48 AM
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solentlife
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Just thinking that the brighter section will help orientation ?

I built a wing with rib / sheet similar but never got it of ground ... got to about 80% completed and something felt wrong about it .... so I put it aside ... I may drag it out and give it a once over again .... you've spiked my interest!

Cheers
Nigel
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Old 06-24-2015, 09:38 AM
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JetPlaneFlyer
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Did the original use a flat bottom airfoil section? It's very unusual to use a conventional flat bottom airfoil on a tailess design.
It will work if you have loads of reflex on the elevons and/or LOTS of washout twist in the wings, but there are many airfoils that would work a lot better for the application.
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Old 06-24-2015, 01:12 PM
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solentlife
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I started a thread on it here ... and yes I was going for flat bottom. It wasn't that which stopped my finishing it ...

It just didn't feel right .. I'm a great believer in the "looks right - most likely is right" camp .. and this was just a little strange to the eye.

Nigel
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Old 06-25-2015, 06:17 AM
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Back at it, this afternoon. I'd like to point out that I'd probably do things differently, or in a different order, if I went into these projects with the faintest hint of a plan. Which I don't.

I glued in a 'floor' of 3/32" basswood, to give me a sturdy place to mount the batter and other components, lend some overall stiffness, and tie the two wings together.


Next, I decided I should have made provisions for some kind of strut to give the wings a little stiffness. Since I hadn't, I settle for epoxying a CF strip to the bottom.


The motor mount is one of those cheap plastic stick mounts. It's glued to the floor and also held down with a couple of zip ties.
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Old 06-25-2015, 06:21 AM
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There's no room for the propeller, so I started hacking at the foam.


Next I filled in the resulting gaps with small bits of foam.


You'll notice that, at some point, I've fitted the elevons which are made of 3/32" balsa, covered in packing tape. I decided it's time to "paint" the wing with colored packing tape before proceeding.


It looks pretty cool with the lights on.
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Old 06-25-2015, 07:34 PM
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The lights look great. Be ready with lots of up elevator on the maiden, i think you will need it due to the airfoil.
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Old 06-25-2015, 09:16 PM
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I try to be ready for anything on the maiden. It's been 100 degrees with 25MPH winds all week, so I'm not sure when I'll get the chance.

The bottom looks a bit like a Mondrian painting.


Adding some winglets, made of Dollar Tree foam with the paper removed, covered with packing tape.
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Old 06-26-2015, 02:47 AM
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Ready for maiden. I’m going to wait to complete the hatch cover until I’ve got everything settled inside.




And ... up in the air.
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Old 06-26-2015, 07:42 AM
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CHELLIE
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Very Nice Wing Builds Mark
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Old 06-26-2015, 07:47 AM
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Thanks, Chellie. Nice to see you around!

It's even now undergoing surgery on my worktable. I was obsessive about putting everything as far forward as possible to avoid tail-heaviness. Funnily enough, it's now a bit nose-heavy. So I'm moving the servos back from their original, problematic, location and may re-position the motor a bit farther back as well.

But it does fly.
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Old 06-26-2015, 07:58 AM
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Originally Posted by mclarkson View Post
Thanks, Chellie. Nice to see you around!

It's even now undergoing surgery on my worktable. I was obsessive about putting everything as far forward as possible to avoid tail-heaviness. Funnily enough, it's now a bit nose-heavy. So I'm moving the servos back from their original, problematic, location and may re-position the motor a bit farther back as well.

But it does fly.
Great to hear that they fly well I had to take a break from RC, I have a Pinched Sciatic Nerve in my back, thats affecting my right leg, a lot of the muscles in my right leg are Knotted, I spend a few hours a day massaging the knots out of my Muscles, I am seeing a Chiropractor for the problem, the problem does not let me do anything, Dang pain is a issue, I am getting better now, but it sure is taking its sweet time to Heal, been like this for over 2 months now, I guess I am just getting OLD My 60 year old body is having a hard time keeping up with my 18 year old brain Take care, Chellie
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Old 06-26-2015, 09:15 AM
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Hope the Sciatica gets better soon Chellie. I had an attack last year so I know how painfull it can be. Stretching excercises to de-compress the disks in the back can be effective but at the end of the day it takes time.

mclarkson,
Yes she looks to be flying nicely. I'm curious to know what position you had to put the elevons in to get her to fly level, they dont look to be excessivly 'up' in the photo?
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Old 06-26-2015, 05:03 PM
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Originally Posted by JetPlaneFlyer View Post
Hope the Sciatica gets better soon Chellie. I had an attack last year so I know how painfull it can be. Stretching excercises to de-compress the disks in the back can be effective but at the end of the day it takes time.

mclarkson,
Yes she looks to be flying nicely. I'm curious to know what position you had to put the elevons in to get her to fly level, they dont look to be excessivly 'up' in the photo?
Thank You JPF Yes it takes time and the pain is Horrible, I am getting better, It just does not let me do anything, what is scary, is that my right leg sometimes wants to give out when i am walking, I have to be ready for it, I almost fell a few times, going to see the Chiropractor again today for an alignment and tune up LOL, I love my New Chiropractor, they do a full Back massage along with the electronic muscle stimulation and heat pads before the adjustment, I feel like I am walking on a cloud when I leave the DR I told them I feel I am able to do some Extreme Mountain Climbing now after a treatment Yea Right huh Take care and have fun, Chellie
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Old 06-26-2015, 08:08 PM
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That sucks, Chellie. Getting old is the worst ... except for the alternative.

JetPlaneFlyer - I had them pretty danged far up. My first few flights went straight into the dirt as I barely had enough elevator left to keep her level. I kept cranking the reflex up up up up and it finally flew pretty well.
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Old 06-26-2015, 08:43 PM
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Originally Posted by mclarkson View Post
JetPlaneFlyer - I had them pretty danged far up. My first few flights went straight into the dirt as I barely had enough elevator left to keep her level. I kept cranking the reflex up up up up and it finally flew pretty well.
It's quite reassuring that it did that. The theory says if using a flat bottom airfoil without lots of reflex it would try to tuck under, so it's kinda good when practice bears out theory. I'm sure it will fly fine if you have lots of reflex cranked in, it's just a bit draggy and inefficient, hence my original comment about airfoil choice.

The only problem with higher performance specialist tailless airfoils is that they don't have a flat bottom so are harder to build.
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Old 06-26-2015, 08:56 PM
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Originally Posted by JetPlaneFlyer View Post
The only problem with higher performance specialist tailless airfoils is that they don't have a flat bottom so are harder to build.
Not only that but elevon reflex is tunable in flight even, much easier than reworking exact wing twist or washout.
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Old 06-26-2015, 10:32 PM
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Originally Posted by mclarkson View Post
Ready for maiden. Iím going to wait to complete the hatch cover until Iíve got everything settled inside.




And ... up in the air.
Looking Good there Mark!
Nice Pic too!
Crash
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Old 06-26-2015, 10:37 PM
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Originally Posted by CHELLIE View Post
Great to hear that they fly well I had to take a break from RC, I have a Pinched Sciatic Nerve in my back, thats affecting my right leg, a lot of the muscles in my right leg are Knotted, I spend a few hours a day massaging the knots out of my Muscles, I am seeing a Chiropractor for the problem, the problem does not let me do anything, Dang pain is a issue, I am getting better now, but it sure is taking its sweet time to Heal, been like this for over 2 months now, I guess I am just getting OLD My 60 year old body is having a hard time keeping up with my 18 year old brain Take care, Chellie

Sorry to hear of your health problems Chellie and hope you get better in a
hurry. No fun being in pain, I know.
Crash
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Old 06-26-2015, 10:46 PM
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Originally Posted by Rockin Robbins View Post
Not only that but elevon reflex is tunable in flight even, much easier than reworking exact wing twist or washout.
You still have elevons for fine tuning... It's not 'one or the other'
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Old 06-26-2015, 11:39 PM
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Now that I've had a successful maiden flight, it's time to finish up all the little details.

I had slavishly put everything as far forward as possible – flying wings tend to build tail-heavy if you’re not careful – but the resulting plane was actually a bit nose-heavy. This was fine, as the old location of the servos was problematic. The pushrods were long and tended to drag against the top of the airfoil. So I moved them back significantly. Since the wing is hollow, I had to locate them against – and in line with – one of the internal ribs, to give them something to hold onto.


Next, to build a battery hatch. I drilled 2 holes in this thin plywood – originally glued here to help hold the two wing halves together – and epoxied some little rare earth magnets in there. There’s a tall stack of them in this photo because that’s how I register them against the hatch. I make a stack on one surface, then push the other surface down into it. I use the resulting indentations to figure out where the matching magnets go.


Here’s the actual hatch, again, made from paperless Dollar Tree foam. If you look closely near the top you can see the two impressions from my stack of magnets. The hatch is glue onto a couple of hinge pins that I’ve had forever and never used.


I wrestled the wires into more manageable form and closed off the holes at the rear. Here’s the more-or-less final bird.
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Old 06-27-2015, 06:59 PM
  #23  
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Great looking plane.
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Old 06-27-2015, 11:29 PM
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I uploaded a video of my sketchy first flights, for anyone who's interested.

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Old 06-28-2015, 11:10 AM
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Originally Posted by mclarkson View Post
I uploaded a video of my sketchy first flights, for anyone who's interested.

Awesome Mark!
Crash
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