Wrapping foam wings ??

[slackdaddy]

I am upscaling a boosted glider, about ~48" wing span, a foam wing comes to mind. The lighter the better.

Could I use open cell styrofoam (white board) and "wrap"
it, or "skin it" with something, to give it strength ??

I never did R/C planes, so I am not up on "foam" wings.

Thanks for any input or "links" to "how to build a foam wing"

Slack

 

[vjp]

Just google a search on "foam wing sheeting" that should get you started. I have only ever done one sheeted wing, it wasn't that hard. It was a blue foam core set I bought from a guy on eBay, I sheeted it with 1/32" balsa, and polyurethane glue. Worked like a charm.

 

[gpoehlein]

I've been toying with this for a while (just haven't gotten around to it yet) - I was thinking about using one of those foam gliders as the base for my wings. Hobby Lobby has several (some have a pretty large wing span) and they are cheap. I figured a layer of monocote around them and they're good to go. I just haven't figured out what I want to make the rest of the RG look like yet!

Greg

 

[LFLekx]

Originally posted by slackdaddy
Could I use open cell styrofoam (white board) and "wrap"
it, or "skin it" with something, to give it strength ??

The air pockets in open-cell foam makes it unsuitable as a structural material... even fiberglassed, it will collapse under stress. (Especially the thin sheets that would comprise a wing.)

Closed-cell foam is the most commonly-used foam core for such parts. Look for solid-blue Styrofoam insulation at your local building store.

 

[Micromeister]

Styrofoam SM rigid insulation make great wings and rotors.
Here's a photo of on of my 4-D12 or F powered over sized Rose-A- Roc Demo model. the foam is reinforced with a 3/16" Carbon fibre tube "Kite Spar" and covered with adhesive backed Arlon Vinyls. which seems to add little to the stifness of these 4.5" x 56" rotors

 

[slackdaddy]

OK, I might as well fess up, I am making a 8' flying Jenny/RB.

I do not want this to be a "high dollar" build, FJ/RB never "last" more than a few flights.

What thickness foam would be best ?

Do I need to add a leading edge "half round spar" ?
(what material, wood ?)

What would be the best economical covering material to add strength ?

Foam for the rudders and struts ? or home made balsa plywood?

I know I will have to do much "trial and error" , but I am open to any and all sugestions.

Many thanks,
Slack

 

[SecretSquirrel]

Originally posted by slackdaddy
OK, I might as well fess up, I am making a 8' flying Jenny/RB.

Me too

I do not want this to be a "high dollar" build, FJ/RB never "last" more than a few flights.
What thickness foam would be best ?

3/4" blue foam works well

Do I need to add a leading edge "half round spar" ?
(what material, wood ?)

Wouldn't hurt, hard wood would be fine.

What would be the best economical covering material to add strength ?

Foam for the rudders and struts ? or home made balsa plywood?

Depends on what you call economical. I'm covering the leading edges of the wings with carbon fiber. Also, the wings will have a 6" carbon fiber strip running tip to tip, top and bottom to act as a spar. The center wings and rudders will have a similar set up. Then all the foam will be covered in fiberglass. The lower brace should be made from plywood. I'm embedding hard wood into the foam at all the joints. My Red Baron will have to be taken apart for travel to the field, so all the joints will be hardwood and fasteners.

 

[SecretSquirrel]

Originally posted by slackdaddy
FJ/RB never "last" more than a few flights.

By the way, I've been flying the same Red Baron for over 2 years now. I've lost count of the number of flights.

 

[slackdaddy]

Hey Don,
I thought You would chime in

Originally posted by SecretSquirrel
By the way, I've been flying the same Red Baron for over 2 years now. I've lost count of the number of flights.

I guess You follow the directions and don't use C6-3s ??

Mine dont last long due to:

1) gliding away (lost 2 this last week or so)
2) Smacking a fence post on landing
3) the estes 12ga ejection charge
4) a rare ground loop

I ordered some 1/64 balsa to make up some 3/64 balsa ply for the rudders (the only week point)

Anyhow I was going to grab a 4x8 sheet of blue board (1/2 or 3/4 ?) glue on a leading and trailing edge, and wrap it in Mono-Kote. not sure about the rudders though.

You are glassing the whole wing ? Do You know of a supplier for 1/2" or 3/4" carbon fiber leading edges ?

Many thanks,
Slack (Nick)

 

[SecretSquirrel]

Originally posted by slackdaddy

I guess You follow the directions and don't use C6-3s ??

I fly mostly on A8-3's and I trimmed it to circle.

Anyhow I was going to grab a 4x8 sheet of blue board (1/2 or 3/4 ?) glue on a leading and trailing edge, and wrap it in Mono-Kote. not sure about the rudders though.

You are glassing the whole wing ? Do You know of a supplier for 1/2" or 3/4" carbon fiber leading edges ?

I would go with 3/4" foam.

Yes, I'm glassiing the whole thing. I think you will find that with an 8 foot wing span, you will have to stiffen the foam to prevent flutter during boost. That's why I'm going with the carbon fiber/fiberglass covering.

What motors are you planning to use? I'll probably go with something in the J-K range.

 

[slackdaddy]

Don,

The 1st bui;d of this will be a quick/cheap build to check the concept.

I was looking at routing a concave into the leading and trailing edge,
glueing a 3/4" dia carbon fiber tube an the leading and trailing edge, then wrapping the whole thing in Mono-Kote.

Hopefully the leading and trailing edge tubes will act as spars,

Next I have to figure out the rudders and "middle" wings and there attachments. Any pointers ?

With the engine foward of the CG and CP, under powering it should not be dangerous or unstable ?? I will have to weight the final build and determine engine.
That said, I was looking for a low thrust long burn.

I believe it was Chuck Rudy I saw with a 15 sec burn mono rotor, I may have to hit him up for a special blend, when ever I get this built.

November/December I am locked with deer hunting, this may have to wait till lake winter.


Slack

 

[SecretSquirrel]

Originally posted by slackdaddy
I was looking at routing a concave into the leading and trailing edge,
glueing a 3/4" dia carbon fiber tube an the leading and trailing edge, then wrapping the whole thing in Mono-Kote.

Monokote may not stick to blue foam. The temperature setting for ironing on the monokote may be higher than the melting point of the foam. I would do a test piece first.

Hopefully the leading and trailing edge tubes will act as spars,

The spar should really be about 1/3 back from the leading edge of the wing.

Next I have to figure out the rudders and "middle" wings and there attachments. Any pointers ?

Hardwood strips embedded into the foam, then covered.

 

[LFLekx]

Originally posted by SecretSquirrel
Monokote may not stick to blue foam. The temperature setting for ironing on the monokote may be higher than the melting point of the foam. I would do a test piece first.

I've never tried applying MonoKote *directly* to foam... but I can tell you that the two don't mix. I once tried to apply film to my foam-core fins, and the heat that's required to activate the adhesive and shrink the film is enough to melt the foam. I spent an afternoon slitting open my fins and filling them with thickened epoxy, just to get their stiffness back.

If you want to do MonoKote - don't use foam. End-grain balsa is my core material of choice now.

 

[slackdaddy]

Ack, so Mono-Kote is a no go for foam, what do the R/C guys cover foam wings with ??

Thanks,
Slack

 

[aerospike]

There are low temp iron-on coverings for foam. Search the R/C forums on the web.

 

[LFLekx]

Originally posted by aerospike
There are low temp iron-on coverings for foam. Search the R/C forums on the web.

There are also versions of Trim MonoKote that don't need heat to activate the adhesive. They're only eight inches wide, though...

 

[stevem]

most r/c foam core wings are covered with balsa sheeting before applying monocote

 

[vjp]

Originally posted by stevem
most r/c foam core wings are covered with balsa sheeting before applying monocote

...or sometimes, thin ply. That's because the foam itself doesn't have the rigidity and must be skinned with something that will give it strength. I have a 2M EPP foam glider, which was skinned with monokote, but it has a long channel in the wing into which was epoxied spars for strength. Since slackdaddy is shooting for economy, balsa sheeting is probably going to cost too much on a 8' wingspan, but another material like posterboard, or brown kraft paper (they sell mongo big rolls of heavy kraft paper at Home Depot in the paint dept.) attached with probond or another polyurethane glue, ought to add lots of strength at minimal cost.