highfly3D

I have seen some giant airplanes built with Foam ribs, since it is also light weight, the complete wing will be very light weight. since i need to know other than blue foam, can we use any other foam since blue foam is hard to find for me, i am attaching this pics that i got from the other site.

Highfly3D.

allen_d

Is this insulation foam?

SST

My Feedback: (2)

Pink would work just as well. I'd stay away from the white stuff for this particular application though. It's only half as dense as pink or blue.

BMatthews

The weight saving from using foam ribs is extremely minor if it's there at all. The weight is going to be determined far more by design and other material choices than from just using foam ribs.

At 2 lbs per cu ft for pink or blue foam a 1/2 inch thick foam rib is the same weight as the same rib made from a sheet of 8 lb/cu ft 1/8 balsa. 6 to 8 lb/cu ft balsa is what you get if you choose the lighter sheets of wood at the hobby shop.

This topic came up on another forum and the outcome seemed to be that the foam was used more as a cost cutting step rather than for weight savings.

SST

My Feedback: (2)

Definately the reason to use foam is cost...A 4 x 8 foot sheet of 1/2" pink costs about $8.00. I have a half completed 8 foot version of the old Hobby Shack Super Sport Trainer in the garage made mostly of 1/2" pink foam & Coroplast with some lumberyard wood that has perhaps $60 in the airframe itself, including the glue & fiberglass cloth.

highfly3D

Hi

I mean what is the real diffrence between the white foam and the blue foam dose any one know the real diffrence ? and what is blue foam is genrally used for?

Highfly.

DICKEYBIRD

The blue or pink stuff (Dupont Styrofoam or Dow Foamular - XPS) is extruded under heat and pressure, is denser (heavier) and has a more consistent texture. The white stuff (EPS) is made up of expanded beads fused with heat in a mold and consists mostly of air. http://www.everything2.com/index.pl?node_id=30708

The Bob Godfrey 1/3 scale Laser wing I had was constucted exactly like the one shown above except it had 1/2" thick white foam ribs with balsa capstrips. 1/2 the density but twice the thickness = same weight but the white stuff is cheaper.

highfly3D

Hi

So is it ok if i use a high density white foam for this application, will it do? i am thinking to use it for a 32% extra wing.

Highfly 3D

DICKEYBIRD

Yes, but there's no need for high density foam. The regular 1 lb/cu ft stuff is fine as long as you make your ribs about 1/2" thick with balsa D-tube sheeting and capstrips. The Laser had 3/32" balsa sheeting and cap strips with 1/4" sq spruce spars/full depth cross-grain 1/4" balsa shear webbing.

BMatthews

The pink and blue stuff is commonly used for insulating basement foundations on the outside under ground or on flat roofs. If you find a building supply outlet that has the white stuff in large sheets they should also have the pink or blue stuff as well. If they don't then the next place will. I can see why they may not have it in California since the need to insulate to this degree isn't that high but in Wyoming? It DOES snow there doesn't it?

My own preference for this sort of thing would be the pink or blue just because it's not so easily damaged by vibration thanks to being that little bit more solid. I've heard of the white stuff basically mashing itself to bits in higher vibration areas. But if the sheeting and cap strips are well bonded at the ends I suppose that would support it well.

SST

My Feedback: (2)

DB, the whole idea of the foam ribs is to cut building costs. With all that balsa you seem to need with the white foam, I don't see any real reason for the white foam ribs. A pink foam wing could be built with foam sheeting and shear webs, and the only wood I'd add is the spars.

dicknadine

back before Katrina, I built a 80" Flea, useing 1/4" white foam sheets completely for ribs and sheeting, yellow glue. yard sticks for wing spars. simple construction and strong, in fact the complete plane was foam sheeting. it was rigged to carry a small Flea on the wing release in flight. had 2 flights on it and Katrina liked it better than me-- never did find it and all of my planes, along with the house and 3 shops. now building 3 standard balsa stick versions of a 43" Fokker D7. std fighter pilot, 1919 2 pssenger in an enclosed cabin and a 2 cockpit version that Fokker biult to fly he and his girl friend out of Germany , before the Russians got there. just something to be different. all will be electric. no photos yet, as I havn't mastered the workings of my new HP 315 Photo Smart camera yet, more complicated than my old Sonny Floppy, that went for an unsucessful swin in Katrina. there are fotos of the 80" Flea in my old photo file someplace in the old RCU files. dick