> > 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
> --
It's true that the solid foam in the wings doesn't add much weight.
Still, if the foam is there. the fuel can't be there, and keeping the
majority of the fuel out of the fuselage has some safety advantages.
Also, keeping a heavy item like fuel in the wings (where the "lifties"
are) makes a lot of sense.  Finally, keeping the fuel right on the CG
minimizes trim issues in flight and eliminates one possible
CG-out-of-limits problem on each trip.  Based on a close call he had
when flying a design built with foam that dissolves in fuel, Steve did
not want to make any structural components out of it if it might come in
contact with fuel.  That pretty much eliminated any hot-wire formed wing
components if fuel would be carried in the wings.

Every design decision is a trade-off, and the factors above may not
apply to every aircraft.  There are lots of factors.  Ribs and separate
skins result in more work than a hot-wired foam ting, but there are
benefits.

I very much agree with Paul's distaste for sanding and filling and
sanding and filling.  Vacuum bagging the components is really not that
hard, and using a smooth "tool" (glass, sheet metal, or the very popular
FRP material used for inexpensive shower enclosures--smooth, cheap,
bendable in 2D, and available at every Home Depot) is very attractive.
Zeke Smith's books do a good job of explaining how to do it.  I think
there's a way to modify the Foldaplane method to significantly reduce
the time spent in building the wing, we just need to think it over a bit
and try some approaches.

Mark Waldron