Three excellent models are combined to get the best of each..

The result I am calling the "W" wing ............heart shape
The idea came about when I was designing a new night kite.. The W shape lends itself to cross bracing which makes for a rigid structure..
To fit in a my holiday suitcase the model needed to be folded into 3 layers of about 26" length by 13" width.. the middle panel which also lies flat will fold down to form the center of the W.. And when folded into the W shape CF cross bars at the top and bottom of the W will keep it rigid..

To test the model I first built a foam version, and made it using a KFm4 section
The big 26L version is all from 6mm depron.. The layers that make the steps are directly laminated with no spars.. being direct laminations it is the easier build of the two..
Specs are 26"x13" panel size.. AUW 18.5oz ..area 5.89 sqft .. loading 3.14ozsqft .. 150W bell motor ..1300 3 cell lipo .. 3x 12gm metal gear servos .. 20A ESC .. Hitec REC ..

EDIT Although this big'nflies very well it is too docile... the mid size version at 21" long is proving to be superb in all ways ..It has the good all round mix which makes it a lot of fun, whist still having a lot of stability..

Each of the original parents has added something.. The Capricorn inspired the W shape , The Nutball the super stability, The UFO the better roll.. All three are excellent in their own rights all great fun

Maiden of the KFm4 W wing Heart shape 26" long (5 min 31 sec)

KFm4 "W" wing 26" Heart shape maiden part2 (4 min 35 sec)

KFm4 "W" wing 26" heart shape easy flying (4 min 30 sec)

Because the Big'n was so very good , but large, I decided to go down a size and make another for the popular Blue Wonder type of motor..

This version was scaled to give 3.87 sqft and the panel size is 21"x10.5" .. Again its a KFm4 but this is all from 3mm depron

It has just been completed but is unflown at the moment.

Specs on this are AUW 10.75oz .. wing loading 2.77 ozsqft floaty.. BW type motor .. 3 cell 500 lipo .. 8x4GW prop.. 3x5gm servos .. 18A ESC .. Hitec REC..
There is more than enough thrust to go vertical

EDIT the power is upped by swapping out the Blue Wonder for an AXI..

This size and shape has turned out to be by far the best, and is the one to make..

..the big one is too docile , the 21" size is perfect.. the smaller one tried next was too light and got hit by the winds

Also note the 3mm build came in at 4oz less AUW than a similar 6mm build.. due to a combination of various factors all adding to the final weight..
Being lighter it flies solwer, and having been overpowered it is by far the most fun of all the builds....

Now for its build.. I will show the pics from the smaller build.

Depending on the size you want, you will make this in either 3mm or 6mm depron
For 6mm its best to cut out the three panels of the centre layer seperately, then after marking and cutting each panel they are rejoined to make the W..
For a 3mm build I found it easy to bend the main layer using a craft heat gun..

Either way the W is assembled and the angles measured and fixed using a cool melt glue gun. To this W layer the outer top and bottom front layers are laminated..
See the pics above


On laminating..

UHU por does the job, apply to both surfaces where it needs to be fixed , let it dry and then accurately and carefully get it in position without touching..then push together.. have each main panel section flat on a surface as you do this to avoid adding warps..

The outer layers are made from four parts, I started laminating at the center and worked outward.. Chamfer the edges of each part to get a fair fit, its better to have a small gap on the outside of each joint, because you then use hot glue in the joints to further fix and reinforce the angle
IMPORTANT You should be checking the joint angles as each section is laminated, and applying hot glue whist maintaining the angle.. When its set you can let go..

NOTE The outer layers will need to be cut in slightly different sizes in width only ...the outer layer/sections on the bottom will need to be trimmed down, they will stick out slightly..So these can be made to the same size as the main layer
The layers for the top skin need a slight enlargement to fit well.. on the two outer sections add 1/4" to the width, or you will be adding, as I had to do, a small outer fill strip

Tape
I always use 2" colored packing tape for decor and reinforcement.. On depron it adds stiffness and prevents tear damage..
On this model Ive taped over the outside of all the folds. Ive fully covered the elevons, fin and rudder, then used more tape to make the hinges, taping along the full hinge line top and bottom..


Spars and steps... KFm4 50% step location..
On both models the step is 6mm in depth.. This has always worked well for me, I haven't found I actually need the step any deeper for the models I build..
So the Big'n has all layers directly laminated, giving the 6mm step, and a nice stiff wing
The small model got 1/8 balsa spars at the step, this raised the depth to 6mm and also added extra stiffness to the wing..

As a side note....I often use balsa spars on KF wings under the steps because the multi layer build makes a stiffer wing.. step depths seem to work from 2mm to 15mm, for the sizes of power models I usually make, 6-12mm has always been good and I cant tell much if any difference between them.

Flying

Set the COG to 27.5% and have a few of degrees of + reflex on the elevons... this is a nose heavy setup.. This is what was set in the maiden videos up above and makes for a nice steady flight..

I will be adjusting my COG back when the weather gets better, this should further improve the axial roll and the inverted flight..

Comparisons vs my favorite...The Nutball
Unlike my Nutball, the multi dihedral on this one makes it happy and stable when inverted and it just needed a bit of a push to keep the nose from dropping when upside down..(offsetting the heavy nose and reflex set on the trim)

In flight.. Stable and maneuverable like my Nutball, but much improved inverted and in the roll...All my larger Nutballs have been a bit barrelly in the roll and have hated inverted flight..

Goldguy has his smaller Nutball versions rolling better, so I leave it to him to knock up a smaller indoor version of this, for comparrison..It should be easy to make a 3mm flat depron version, all you need is the folds done

Ive been Sketchuping... here is a variation and is a more accurate cross breed

It needs pontoons or skis and it would be a great float plane....

Hi Dave,

Great idea and seems to fly very stable.

I'm looking forward to see your foldable design for this one.

I need a plane for next year's holiday!


Already seems like this one is going to be a "must have" for me.


Greetz

It would be easy enough to add floats or wheels to the bottom of the W.. I usually fix the landing gear wire bends to a ply plate, then attach with velcro strips..
It just needs a new set of bends to allow for the dihedral..
You would also have to reposition all the gear on top of the wing for better waterproofing

removable UC systems here http://www.rcgroups.com/forums/showthread.php?t=937395

Last year I made a foldable Nutball holiday kite, which was OK but the main centre section had too much freedom to twist, so response wasnt sharp..And I built it too heavy, so it would glide like a brick, it always needed some power to fly.. My first nutball kite, non folding, is super in all ways.. but making it a folder it lost its rigidity..
A couple of years back I also made a Capricorn kite.. This had a nice rigid frame work (not foldable).. again it was OK flying, but I didnt like my elevon setup, and the original's elevons were too complicated to use on a kite
However I keep trying to get an improved model..
I also have built the UFO as a kite, this was one of the best flyers, however I used raked forward elevons, for increased area and faster roll, and I had a depron Fuz with rudder for the high alpha and super slow speed control..

Hence the rethink.. The W shape to give a rigid structure, The half round shape, with enlaged tip sections, and more dihedral to give better stabilty, The raked elevons (luckily) on the round shape give enough effect to easily overcome the stability and controll the roll.. The rudder does its usual job at ultra slow speed and high alpha, working well with the dihedral..

more info on all the kites is here http://www.rcgroups.com/forums/showthread.php?t=987191

Most Interesting !!!

Ive now maidened the smaller "W" wing Folder model designed for the blue wonder type of motor..
Truly superb... Chuck it about and it doesnt bite... Super stable but highly maneuverable..

what it wont do... roll using rudder only... spin...knife edge

what it does is everything else, and does it well

low rates video...
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KFm4 "W" wing 21" heart shape Blue Wonder size Maiden Low Rates (8 min 17 sec)

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high rates video..
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KFm4 "W" wing 21" heart shape Blue Wonder size Maiden High Rates (10 min 25 sec)

Dave , Love the design of the Cap-U-Nut !!!
Just one question ... Might one be able to heat bend the wing into the required shape ... ? Have done that on my Jerbear Corsair and Potato Chip (crisp) with most satisfactory results ... very strong , light ...

If you make one with a single layer rather than KF'ing it Heat bending could be a quick solution..

The 3mm depron KFm4 version had the center layer heat bent, but after that its easier to add the outer layers in small sections,and then hot glue between the joins in the sections
For 6mm I cant heat bend it well enough so I cut and rejoined..that worked ok..

Today after flying the smaller version I reflew the Big'n.. really chucking it about. It will do everything just the same but carries more momentum through its maneuvers..Both tends to fly more sedately, if thats what you like..

Unfortunately I had filled the camera card so Ive no video on that flight

Heat bending then gluing 3 layers will give problems in fitting the layers, and if you dont get it acurately lined up for laminating you will totaly mess up the model..
Even bending the layers will be a problem as the top layer has to be fractionaly larger and the bottom layer that fraction smaller to fit properly..
Its much easier to cut the outer layers into sections and fit as you go.