Was digging through some old pix and came across these.  This was an attempt to buid a foam wing with substantially less foam than in a normal cored wing.  I'm showing it here just to show even crazy ideas have a place.

The first attempt was to build a wing with normal ribs only made of foam.  My friend Mark Bambrick framed one up with 1/2" foam ribs, a foam LE and TE and foam flpas.  Got it all cut and it was not too bad.  It was certainly light, but even the 1/2" ribs got pretty snaky to work with.  Of course, after it was sheeted it was fine.

Shown here is the third attempt, attempt #2 was actually used in the Eclipse Mk 2 that I campaigned from 1981-1983.  The approach used here was to build an eggcrate of 1/4" foam ribs, then add foam then wood LE and TE plus foam flaps.  Egg crate spacing was about 2.5" so even at 1/4" thick the foam did not snake around too much.  This is not a true geodesic wing but by angling the crate diagonally I got good support for the sheeting and some nice structural stiffness.

Pix 1 shows assmbly of the basic eggcrate.  These pieces slipped together and glued with a drop of titebond just at the intersection.

Pix 2 shows the foam LE, TE & flaps installed, then the whole thing was cut like a normal foam wing.  Then the rib joints were all re-glued at all the intersections using a thin nosed glue gun and Titebond.  The wing core is interstion at this pint.  It weighs scarcely 1 oz ut cannot support its own weight in bending.  However it is EXTREMELY stiff in torsion due to the diagonal rib orientation.

Pix 3 shows the core to which have been added wood edges and the landing gear platform.  I really liked installing these triangluar LG platforms as they were well braced to the sheeting and LE. The core is shown resting on the Eclipse 2 which had the same style wing structure.

Pix 4 shows the all-up weight for the wing ready for sheeting with all its wood edges, LG platform & wire installed at just under 3 oz.  Of this the foam was barely 1 oz, and the rest of the weight was wood and wire.

Unfortunately the wing in the pix met its demise at the next step - sheeting.  On Eclipse 2 I used epoxy on the ribs to attach the sheeting.  It was durable, strong and stable, but I thought I could do lighter!

For the wing in the pix I prepared the sheeting in the regular way, but then I covered one side of the sheeting with "OO" silkspan attached with thin cA.  After sanding out the covered side, I flipped that over and sanded the inner balsa surface away so the skin with covering was .060.  It was thus thin with a hard shell finish readdy for a sealing coat and filler.  Then the mistake: I tried saving some weight using titebond to attach the sheeting to the ribs.  Unfortunately the the silkspan & CA covering had formed a vapor barrier and there was no where for the water from the titebond to cure out. As a result the sheeting buckled badly...

If I was ever to try this again I think I would forego the sheeting.  I would add a spar top/bottom and capstrip the rib strips using foam safe CA.  Would make for an interesting look and should still be light and strong...

Mark,
I was writing for MAN - I was the last of the CL columnists in the early 1980's.  I published these pix (or some like them!) back then in one of my columns in 1982 or so, could be were the seed was planted...?  No matter what, I think it is BEEZAAAR tha we both had similar experiments going on!

I was at Toledo some time later and saw where somone was making a big pattern plane (EU-1?) using wings that were cut normally then cored vertically (top to bottom) outbaord of the LG installation.  On a wing that size you can remove a LOT of foam!  THe cores were beautiful but EXTREMELY labor intensive!

I love fully sheeted wings, but getting harder to find decent balsa.  I might want to dust-off some of the old foamies too...

 

Dennis,
Not sure I can say one way or the other, I just remember going through it. It was amazing how light and I perceived them to be stonger,, (probably my imagination but strength to weight was surely better) Labor intensive, oh yeah, you could say that. Cool factor was through the roof though. Sure wish my buddy Dave was still around, he would have loved yoru pictures, alas Cancer took him away a couple years back. Not sure if I were pursuing light foam wings if this is the same way I would go or not. There is a guy I know a little ways away from here, he works at a place that "carves" foam with a CNC machine to create forms for pouring concrete. you would be AMAZED at what they can do. Now that intrigues me. Right now making a spinner is more on my forefront of projects to tackle that probably aint worth the time!

One of my "lessons learned" was that while it was POSSIBLE to build a wing this way, leaving out foam was not the best way to save weight.  Other things we can do with balsa edging, landing gear installation and ESPECIALLY sheeting have far bigger impacts on finished weight.  Also popcorn foam really isn't very stable when cut into sheets.

If I try it again I might use "homogenized" foam (i.e. pink foam) it is heavier than popcorn but cut into thin sheets it would be OK.  It should cut cleaner too.  Then I think I would cap-spar and cap-strip it.  WOuld really look cool with the egg crate yielding a faceted surface... STEALTH!

Just my two cents worth to spur some thought, but the last five stunters I've built, all piped ships for 65 or 75, I have used "meat tray" foam that I always save (when they are of any size) for the formers.  They are typically thick enough for good glue joints but lighter than wood after I remove a large portion.  The smooth finish on them seems to ad stiffness, but that could be my imagination?
You guys with the egg-crate look have a work of art there!  Those are awesome, Dennis.
Blessings,
Will

You're more than welcome, Dennis,
It was great meeting you at our FCM weekend last summer - that way I can finally put a face to the only member of the A clan I hadn't met!  Now, next summer we have to threaten Todd & Amy with someting really dire sounding to make them come and the reunion will be complete!
Blessings,
Will

A number of the RC ARF manufacturers were, a few years ago, using Randy's method for pattern wings.  Usually they cut the wing panel, then inserted it in a jig which consisted of two plywood plates with matching holes cut in them.  Then melt a hole  through the wing, insert a hand-held hot wire and cut the hole out.  The end result was a foam wing core with a honeycomb pattern of cutouts in it.  For sheeting, the same pattern was applied to the sheeting so the glue could be applied just where it needed to be.

Either method, cutting and fitting sheets or honeycombing is a lot of work.  Doing the honeycomb method eliminates a lot of potential places for excess glue to accumulate.