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Old Apr 06, 2015, 03:37 PM
nistrum21 is offline
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ok im sold. i was looking to build an A clone in the 40 odd inch region. and i wanted to make it out of depron. i can 3D print the nose maybe to make it a little more solid. ..
i was going to ask for the 48 inch kfstep version what kind of depron did you? and what is the purpose of the triangle bit at the nose? could i cut that out?
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Old Apr 06, 2015, 04:53 PM
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Originally Posted by nistrum21 View Post
ok im sold. i was looking to build an A clone in the 40 odd inch region. and i wanted to make it out of depron. i can 3D print the nose maybe to make it a little more solid. ..
i was going to ask for the 48 inch kfstep version what kind of depron did you? and what is the purpose of the triangle bit at the nose? could i cut that out?
I used DTF...dollar tree foam...or Adams foam by name brand sold by DT.

The triangular nose job added is my own design. Its use is to add lift and also to totally eliminate the weakest point in the Alula design, IMO, the neck junction at the wing shoulders. That's where it breaks first usually. So I came up with the blended fuse nose.

You can use that style or the original or anything in between , I suppose. I used it on another design that is flying very well with it and a PW51 airfoiled wing.

The DTF or whatever depron you decide in 4-5 mm is "maxxed out" using the KF foil at 48 inch WS. Better at 36-40, I think. It's too thin to layer up in 4 steps at 5mm. Maybe use 6 mm or go with 5-6 layers of steps if you follow me.

Good luck with your project and welcome to RCG!
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Old Apr 07, 2015, 04:59 PM
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Thanks Steve O.
that makes sense i see why you added it in there. ill have to think on what to do about that weak point. might kind of make a hybrid of yours and the original :P

alas i have the same problem as everyone else here in europe. no foamboard as light as DTFB :/ so i guess im stuck with the depron stuff.

funny you say that about the depth of the airfoil. was thinking of going for a fatter one. the depron only comes in loads of like 20 so ill have a tone to mess with.
i got a book about RC plane designs that waxes pretty lyrical about airfoils and their uses and it recommends a slightly thicker airfoil. 12% to be specific. but i probably wont be that drastic.
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Old Apr 07, 2015, 08:03 PM
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Nistrum, for 48-60" birds you can't beat 1" thick EPS with an RM1 or RMS airfoil . Just cut the shape, sand the edges, use afew strips of drywall tape and gorilla wood glue for a skin spar and chuck your gear in there.
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Old Apr 07, 2015, 09:01 PM
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Nistrum, for 48-60" birds you can't beat 1" thick EPS with an RM1 or RMS airfoil . Just cut the shape, sand the edges, use afew strips of drywall tape and gorilla wood glue for a skin spar and chuck your gear in there.
that's what I'm talking bout!!!


Good to hear from ya, Rusty.

The original Alula is somewhat thickish in the mid chord ... about an inch...and that's on a 35.5 inch WS.

Nistrum, you could always scavenge a power supply from an old PC tower and rig up a hot wire cutter lickety split and cut a PW51 or 1211 for more speed.

Or do all three and see which foil you prefer. Ya gotta try that RM foil though ....too easy, fast and flies well.
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Old Apr 08, 2015, 01:13 PM
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might just have to try the eps thing. what do you make the control surface out of?
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Old Apr 08, 2015, 02:02 PM
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might just have to try the eps thing. what do you make the control surface out of?
Flat foam, balsa, correx works but is heavy, scrounge around. Styrofoam meat trays. Then laminate it with tape or iron on laminate for stiffening.
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Old Apr 09, 2015, 12:49 AM
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might just have to try the eps thing. what do you make the control surface out of?
I do the surfaces from EPS as well, cut from the wing rather than added on.. Use tape weave hinges. That's my preferred method.
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Old Apr 15, 2015, 11:22 AM
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The RM1 chamfer cut is good for a glider airfoil.. I have several models using chamfer cuts, my favourite being a big V wing based design.. the model used a 4 ft x1.5ft x1" thick slab of foam.. gliders work better with thinner wings, this one was fine off the slope, so an A clone along the same lines should work just as well..
my RM1 builds are here http://www.rcgroups.com/forums/showt...2156325&page=2 see post 21 for the V wing design...
control surfaces were from 6mm depron all tape covered for stiffness.. they worked fine

building from depron... use more layers of 3mm or even 2mm for more steps.. multiple layers are stronger, more smaller steps work better than deeper steps... and keeping the wings thin improves the glide
my most efficient glider used 5 layers of foam.. a main 3mm layer with 4 step layers from 2mm .. it glides well..
http://www.rcgroups.com/forums/showt...1401748&page=4 ... post 54 onward

got me thinking now.. perhaps its time to revisit the A clone with a few mods.......
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Old Apr 19, 2015, 01:43 AM
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With a thicker wing build you need to remember to scale up if you want to keep the %age thickness down to the 7% which seems to be a good thickness for glider wings

the 5 layer wing above can be made at 38" span , but add another 2mm layer and you need to scale to a 44"

here is another layout.. this one has an extra step that is actually on the elevons, the hinge line being in front of the step..
that works fine.. even though it may seem odd..
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Old Apr 21, 2015, 12:37 AM
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With any of these multi layer wings, first choose the position of the thickest point on the wings chord... ie 30%.. or there about.. that determines the position of the top most and first step.. the remaining steps are spread equally across the chord in one of two ways..
Either excluding the elevons from the division of numbers as post 564.. or including the elevons in the numbers as in post 565..
What I try to avoid is a step just too close and just in front of the hinge line...
excluding the elevons from your calculations produces one solution, the one I most often use.... and having the step behind the hinge line produces another...

The total possible number of steps/layers is worked out from the size of the chord..
7% of the chord for gliders or less is the target thickness.... thinner wings work better on gliders..
How thick your foam is, determines the number of layers..
The more steps/layers the better.. the number of layers determines the KF section you can use..
For power its not important...9% up to 12% is fine as a guide , with even thicker wings still working ok..
And simple KF sections with less layers work well, so the KFm2/3 or KFm4 are the most used
For power models I try to emulate a wing section that suits the function of the model..
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