[cicopo]

I'm closing in on having to cover the 72 inch Lancaster I've been building and looking for some advice. This is my first fully sheeted wing set & I'm going to be painting for the final finished colour. I've read lots about going the light fiberglass / finishing resin route BUT I don't see that adding much in strength but it will add weight. I have many years of restoring Corvettes & know just what it takes in materials to do a structural repair so light weight cloth seems pointless to me. I've been thinking about covering in Solortex (or Worldtex) followed by either finishing resin applied the messy way or Polycrylic sprayed using a conventional spray gun until the weave is filled, sanding, priming & painting. I could also skip that step & fill the weave with some of the many leftovers in auto paint but that may be heavier than the Polycrilic. Has anyone done something similar with good or bad results?

[PRS]

Might want to look at Sig Koverall. It is heat shrinkable and you can put it on with Minwax Polycrylic and also use the polycrylic as a sealer.
Some people like Ezekote but it looks a lot like the Minwax which sands pretty good and does do a good job of sealing.

[Mike Sebastien]

Fiberglassing with 1/2 oz cloth is definitely lighter and gives a great base for paint. Fiberglassing with that light of cloth was never intended to add strength to a fully sheeted structure but does give the balsa some ding resistance.

I have painted super coverite and it takes alot of primer to fill the weave and it is heavy.

[cicopo]

Although I haven't used Koverall I have looked at it & think it will be heavier by the time the weave is filled.
If the fiberglass isn't there to add strength why is it used? Leaving it out of the process must come with some penalty but other than helping to keep the resin from slowly running downhill I haven't come up with one.
Maybe I need to rethink this & go back to my early days (I've been in & out of the building hobby a few times) & re consider silk if I want to add a bit of strength, or tissue plus dope as the base for my paint. Tissue & dope will cover the grain in a lighter way than any other I've ever used.

[Trumpetman]

The light weight fiberglass skin is applied just to give a good base for final finishing and paint. It's not there to give any real strength to the structure but it does add a bit of ding resistance. Done properly, it adds very little weight. Dave Platt has some DVD's where he describes a method for applying the .5 oz. cloth with Z-Pozy finishing resin. Works fantastic. The water based Eze-kote also works really well. Some folks worry about the water based product warping balsa but I have not seen it.

[cicopo]

I think Solortex will supply similar ding resistance but could be wrong. I thought of another idea that I'll need to explore too so I may have to cover something & test away. I have on hand some epoxy primer that I use on frames & suspension parts after sandblasting. One light coat of it should fill the weave & add strength very similar to finishing resin once cured. I have 1/2 or 3/4 oz glass cloth on hand & it would be my choice for the engine nacelles & maybe the fuselage but I'd prefer the Solortex on the wings & stab but can go either way. I've done 3 planes in Solortex & like it for the easy application & added strength. From a simple test it looks like 2 light coats (by brush) of Polycrylic will fill the weave of the Solortex.

[michaely]

Larry,

I looked at the pictures and semi build thread of your 72"span Lancaster; nice.

If I was in your position, I wouldn't commit to a finishing regime until I did a weight and cg check with all the bits and pieces on board, just in case there are any nasty surprises that would point you to an uber light finish.

If no nasty surprise, I would go with what I was comfortable.

.75oz fiberglass and laminating resin can be as light as a heavier plastic film like Monokote and probably yields a harder furnish surface than anything else, in my personal opinion, as well as providing an excellent base for any paint.
But you need to limit the amount of resin you use and absorb as much as possible of the excess; I've read the weight ratio to shoot for is 40/60 resin and resin which takes a lot of restraint. It's cloth, not the resin that provides the strength. People applied small patches of fiberglass cloth with thin cya/instant glue.
Thunderbolt in sw Ontario can supply such fiberglass cloth; they have had sales in the past year.

In terms of structural strength, I think your framework and all sheeted surfaces do that so I would look to the covering supplying split and ding resistance (the "strength") and a base for any paint.
So, again, in my opinion, you could even use tissue. If silkspan, Easybuilt in the U.S. still sells what I suspect is a medium weight grade.

You are using electric power so you could go to a water based finish and the big box stores, I understand, can perfectly match any color sample... and latex paint is light. But I gather it does take longer for the latex to develop scratch resistance than other finishes.
I've had success with NOT warping sheeted balsa surfaces with initial coats of water based polyurethane by applying 3 or 4 'spit'/almost dry coats to seal the wood sufficiently before applying a "wet" coat. The spit coats dry sufficiently within an hours to so these spit coats can be done in one day.

We want to see pictures of the finished model!

[cicopo]

Good info & there will be lots of photos. I'll do a full build thread soon, without going into the covering / finishing side of things because there are so many ways people do that part of a build. The actual construction of all the components is just about done & I need to do a trial fit again to check that everything is square relative to the fuselage etc & check that the landing gear retracts / extends without binding in the wheelhouses. Once everything is verified I can weigh the bare components but so far I don't think I've added much weight vs the original build the plans link to as a magazine article. My power set up is well above that recommended & just barely heavier.

[RAMJET]

1/2 oz glass cloth /west system epoxy mixed down with 50% alcohol , apply the glass and epoxy but before letting it dry take a roll of paper towel and roll it over the wing to draw out the excess epoxy. as the paper towel gets wet keep removing outer sheets until you can no longer remove the excess epoxy. this will also pull the glass tightly to the wood giving a nice uniform finish

[cicopo]

Thank you. I've read about the idea to suck the excess off but not in such a tidy (& easy) way like that.