|Apr 02, 2006, 04:33 PM|
Covering a foam plane? Glass it, iron-on, homebrew, silk??
I'm resurrecting my A-10 warthog ( http://www.rcgroups.com/forums/showthread.php?t=499873 ) with brushless and retracts. Even with CF rods and ribbon for reinforcement, I still want a stronger feel to it and better looks.
I wanted to cover the plane in CoverLite because it is strong and light. but the Coverite glue you apply to the balsa before applying the covering, eats foam like it's going out of style. So much for that idea.
So I was going to just use my tried and true method of 1 part Acrylic primer, 1 part white glue, 1 part water and 1 part Microbeads to fill the imperfections and leave me a nice smooth finish to paint. But this isn't going to add any strength.
I'm real hung up on some sort of covering. I've heard a few people mention covering a foam plane in tissue paper with 50/50 white glue/water as a sort of "Poor man's fiberglass".
Does anyone have a method of doing this? Does it add considerable strength for the amount of weight it adds?
Any other ideas?
I've used monokote on large balsa planes but I would imagine the high temperatures and shrinkage would wreck the plane. Is there other "foam safe" iron-on coverings that don't shrink as much and are lower heat?
|Apr 02, 2006, 05:58 PM|
Joined Mar 2005
try "silkspan" with your Acrylic primer formula. Silkspan is the tissue used for the old tissue and dopw finished Control line models. It comes in 3 weights, and possibly the light, more likely the medium would be what you want. I'm sure heavy would be too much.
Silkspan adds a lot of strength when doped onto balsa. It should do well for your purpose.
I have used silk cloth for a similar project, but it came out heavy. Might want to use it in high stress areas (or double layer the silkspan)
Silk plus yellow glue makes a lighter dihedral joint reinforcement than 2 oz fiberglass and epoxy. Silk is appx 10 times as strong as steel oz for oz. Fiberglass is not quite as strong as silk.
Epoxy doesn't really add as much strength as some people think... its ability to make up for less than perfect joints is where it shines. Just about any glue is stronger than the foam, balsa, spruce or plywood used in the models.
For a .40 size white styro wing I have used grocery bag paper and a mix of yellow glue and water then "primed with water based poly paint... stiff as if I'd used 2 oz fiberglass and epoxy but lighter. (probably not as strong as fiberglassing, but more than adequate for the airplane)
There's also "Towerkote" and Econokote... relatively light and low temp versions of Monokote. But I've never tried to apply them to GWS's foam. I tend to think the GWS foam wouldn't take as much heat as the white styro I've used them on. The temp for good shrinkage of these is getting close to the temp that causes white (beer cooler) styro to deform.
|Apr 02, 2006, 09:11 PM|
If you want to reinforce and strengthen GWS foam, I would highly recommend going the fibreglass route. This thread:
http://www.rcgroups.com/forums/showt...hreadid=189838 or http://www.rcgroups.com/forums/showt...x&pagenumber=1
is a good place to start.
I would suggest 0.75oz glass cloth, sealed with water based polyurethane, (not epoxy) for the A-10. A number of coats of the polyurethane would give a very strong surface.
Given the amount of work you will be doing on the A-10, using “real” fiberglass would not be out of line.
|Apr 02, 2006, 09:32 PM|
I'm just finishing up my F-106 projuect and glassed it with 0.75 oz cloth and WBPU. Added 1oz to the total weight of the model. Now if I can only figure out how to airbrush again after 20 years I should come out with an airplane weighing in at around 23 oz.
Look up the finishing techniques by J Morgan, John goes into great detail on how to finish a foam model, an execlent thread.
|Dec 21, 2006, 04:37 PM|
silk and glue plus gesso for foam covering
I have just covered a Formosa II with light silk- one yard from fabric store does 2 F-II's; used aliphatic glue (furniture, Elmers, etc.) thinned with water.
Silk is much lighter than firerglass, some say stronger. Enough silk for plane weighed less than 1/2 oz. Silk can conform around 3-D shapes.After sanding and spackling, Hold silk against foam, brush on thinned glue. Takes a little fussing to keep the silk down until dry. Heat gun helps a lot. Overlap pieces of silk. After covering, spackle any rough places. Then brush on artists acrylic gesso- from art/craft store- dries fast, sands well. First coat fills, second coat covers. Gesso is pure white. After getting a good surface on gesso, add trim paint, camo, etc. Then spray model with clear acrylic spray can, matte or gloss.
Silk and glue makes foam parts amazingly stiff and strong- no carbon fibre is needed to stiffen wing, etc.! Weight added is minimal- few ounces. Plane can look as good as moulded fiberglass, depending on how much work you are willing to do.
|Dec 22, 2006, 09:16 AM|
Joined Jul 2005
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