Rotary Engine wrote:
> Solid composite in the curves and sandwich in the flat sections
> where you need it. Spray on gel coat. Lay up on glass so there is no > need for sanding. Low cost shipping. Say what you will about the rest > of the design but IMHO this is a major breakthrough in low cost > aircraft fuselage construction.
>
> With the right fasteners the same trick could be used for the wing.
> Here is my idea for that. You build the core of the wing with composite
> coated foam ribs one inch thick and the spar of course.
>
> You then layup the wing skins top and bottom on large  plate window > glass with foam cores where applicable on the flat parts. You then > bend them over the ribs temporarily. Drill the holes for the drywall > anchor screws. Temporarily install the screws. Remove the screws. > Remove the skins. Coat the ribs and spars with glue and screw down the > skins. I call it the drywall anchor technique or drywall anchor wing.
>
> Paul,

    I did some experiments along this line, some time ago, based on Alex
Strojnik's wing skin technique. As a result, I believe that forming a
"D" section leading edge over a male mold is a a preferable
approach. Using a sheet of float glass I laid up the fiberglass between
two thin plastic sheets and rolled out the excess epoxy with a weighted
    pipe. After a partial cure this "blanket" was draped and pulled
tight over the male mold to complete the cure. I've left out some
details but the result was a light weight accurate "D" section
that fit over the nose ribs from top to bottom of the main spar and
avoids the joint right on the leading edge.

    Fred O.


What sort of finish did you wind up with?

I am advocating about a technique where the cured
finished-on-the-outside composite is treated as you would treat thin
aluminum skin.

The trick is the low cost drywall anchor with its very course nylon
teeth biting into a composite covered foam rib.

A solid foam D section core could perhaps make it easier or
perhaps more accurate and certainly stronger as far as panel stiffness
is concerned. It could be precoated with wet composite before
the bendable sheet was applied to thicken it. The foam could
be hot wired cut and sanded. After curing the foam could
be removed with acetone to form a fuel tank.

Another way would be make just the first couple of inches
hot wire cut solid foam and sand and cover that with composites
after the finished sheets were applied using templates to insure
an accurate airfoil. There would be two joints top and bottom.

Come to think of it that is a good way of making the foam ribs.
Stack up a bunch of one inch thick foam blanks and cut them
all at the same time with a hot wire.

Another option would be make just the first couple of inches
with the sharp curve solid foam and sand and cover that with composites
using small templates to insure an accurate airfoil.

A third trick is laser cut the ribs using a NC laser or water cutter.
Cover the one inch thick foam sheet with composite on both
sides and let it cure before cutting. Perhaps that could be
speed ed up to knock out ribs in seconds.

Urethane spray can expanding foam might make a good adhesive
as it will fill any voids.

Here is another low cost trick used by sign makers to make ribs. Make male
and female rib molds using vacuumed formed plastic over plywood.
Reinforce the molds by using concrete. Make several sets. Wet out several
layers of cloth. Place it in the female molds and insert the male mold.
Let it cure. Saran wrap or other think conformal  plastic could be used as a separating film.

I am sure whatever one does it will take some experimenting.
There must be a quicker and cheaper way to make a composite airplane
than the current pre molded skin kit or the Ruttan method. I think the
drywall anchor could be the key as it distributes the fastener load into the softer composites over a wider area.

At the moment the pre punched and riveted Vans type aluminum airplane is one of the fastest and lowest  cost ways of building an airplane.

Paul

Just have Steve cut the ribs for you.  EUREKACNC.COM

   I'm not sure why you would want to get rid of the foam in a wing, it doesn't weigh that much and absorbs an awful lot of energy in the event of a crash. Not to mention Buoyancy.

Tony

You are probably right Tony. Just screw and bond down the glass smooth finished pre cured flex skin to the foam with drywall anchors and let it go at that. Good idea Tony. saves fooling around making all those ribs.
You can route out channels for wiring and hoses. Of course the pre curred spar
will be in there. I hate sanding and I am not good at it. My parts look like an ocean on a bad day :) One may have to stop near the leading edge and cover
with fiber glass and sand just that.

Paul Lamar