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Mar 20, 2014, 11:34 AM
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miniphase's Avatar
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2 metre...no, make that a 4 metre motor glider!!


I started a new wing last week. The main role for this design will be for calm evening flying from my back garden. Too many still days have gone to waste, and from now on they will be enjoyed with an airbourne wing!...or at least they will be when I finish it!

I cut the cores from pink foam, inserted a 1/32nd ply shear web, and laid carbon fillets in. The spar is complete overkill as this wing will be bagged in glass, and the section is pretty thick so will lack top speed, but better to be safe than sorry.

I'll build it with elevons to start with, but may add flaps once I've flown it.

I doubt there'll be anything ground breaking design or construction wise, but doing a thread will keep me motivated to 'get 'er done' (I hope!)
Last edited by miniphase; Feb 17, 2015 at 02:37 PM.
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Mar 20, 2014, 07:50 PM
Herk
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Mar 21, 2014, 06:36 AM
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My 2 metre wing. Very similar design. Profile PW75. Weight about 1800gramm

Flyingwing 2000мм (2 min 38 sec)
Mar 21, 2014, 12:34 PM
You know nothing....
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Mar 24, 2014, 02:48 PM
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Knoll53's Avatar
Quote:
Originally Posted by miniphase
I cut the cores from pink foam, inserted a 1/32nd ply shear web, and laid carbon fillets in. The spar is complete overkill as this wing will be bagged in glass, and the section is pretty thick so will lack top speed, but better to be safe than sorry.
A "motor" glider ......who knew ! That should give you a few more options. Your pink foam looks different than mine.

I like your method of slicing up the cores to drop a spar in first. Looks quick. Have you ever tried attaching bias glass with 3M77 per the sketch, roll on some epoxy, lay on the CF tow, then smashing it all together? Might be quicker and could be stepped down to lighter construction towards the tips.

Since you have a spar, you have the option to go very light on the skins if you want.......it's a good thing.
Mar 25, 2014, 04:24 AM
KNS
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Mar 26, 2014, 04:55 PM
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Drinkes- that looks like a lovely wing, I don't want to go for vertical performance so cruising around at a similar speed to yours would be fine. Any idea how many watts / lb you're running at there?

Kent- yup, I was thinking of fairly light weight skins, maybe with a double layer of cloth in the D box area.

The pink foam I use is different to the stuff over in the US. The impression I get is that it's somewhere between your pink and blue foams in terms of density. I like the stiffness the ply shear web gives, but need to work on the slot cutting for the tows as I've had to fill over the top. I need to spend an evening or two making a sanding tool that gives a guaranteed depth, and then do some trial runs with wetted out tows to get the correct fill. I'd also thought about something similar to your sketch, but running glass or carbon all the way around.

Anyway, back to the build. I've had a few days delay as my thumb had an argument with a saw at the weekend, but I have melted out the slots for the joiner tubes. These will have a carbon tube set in them, back filled with Gorilla glue.....
Mar 28, 2014, 07:19 AM
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Quote:
I don't want to go for vertical performance so cruising around at a similar speed to yours would be fine. Any idea how many watts / lb you're running at there?
Around 100 watt / lb. RimFire 1200 3536 11x7 3S.
Mar 31, 2014, 05:53 AM
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Thanks Drinkles, I had 100w/lb in mind too.

Next stage- I laid the carbon joiner tubes into the oversize holes, made sure all was square and then tacked them in with Gorilla glue. Once this had set, I stood the wing on end and filled the rest of the void with same. I didn't use any moisture, as I wanted as dense a foaming from the glue as possible.
Mar 31, 2014, 09:52 AM
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Knoll53's Avatar
It's amazing how little moisture it takes to set off PU glue.

Will there be a separate joiner rod that fits inside of the joiner sleeve already installed or will this be a one piece wing?

Also, do you have any sketches of the intended structure to be added around joiner? Would like to see them.

Kent
Mar 31, 2014, 10:48 AM
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The wing will be two piece Kent, the joiner set up shouldn't need to be too beefy as this will be quite a slow flying, lightly loaded model.

The joiner tubes just about sit in a opening in the shear web, then there'll be a ply root rib that the other end will be set in. There will also be some localised carbon reinforcement in the bagging layup....
Mar 31, 2014, 12:04 PM
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Knoll53's Avatar
Just a thought......... even with light loads.

With the aft placement of the alignment pin, the root ribs are an important part of the transfer of torsion loads. Do you see an advantage in some sort of connection at the main spars with less need for strong root ribs?

It's a different way to do the same thing......I know.

Kent
Mar 31, 2014, 02:58 PM
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Yes that might help Kent....I'm designing 'on the hoof' and need to plan the pod to house the lipo etc. I want to keep it as low profile as possible, so I may need to hollow out some of the area in front of the spar or joiner to house various bits and bobs. I can see how the forward alignment pin would offer a better transfer of loads....I'm hoping there may still be room to do this even if I cut into the wing for 'payload'.
Mar 31, 2014, 03:40 PM
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Knoll53's Avatar
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Originally Posted by miniphase
....I'm hoping there may still be room to do this even if I cut into the wing for 'payload'.
The rear alignment pin is all that is needed to handle torsion loads, as long as you can "get to it" structurally. With a mighty patch of FRP, you could connect all together AND provide a nice shell in front to hollow out for those bits and bobs.
Apr 02, 2014, 07:55 AM
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miniphase's Avatar
Great minds think alike Kent! I may still need a bit of a pod / bulge underneath to hide the guts. At this stage I'm thinking of lost foam and carbon cloth as the best way to get it done...


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