I have a Ziroli P61 Black Widow on the table and am getting close to applying color and details. Glassing, priming and painting add's a fair amount of weight and that would be a detrement to this model. I do however, want this to be a scale bird with as much detailing as possible. What other, lightweight finishing techniques are available to the modeller that still affords the modeller to add panel lines, rivets and stays where it should?

I suggest looking into applying the fiberglass using the water base polyurethane technique. While this only provides about 60% of the strength of a resin fiberglassing, it is about 1/2 of the weight of a resin job.

As for painting, I suggest using latex paint. You can get an EXACT color match for about $10 per quart. Latex does need to "cure" about 7 - 10 days, then it can be be clear coated with water base poly for fuel proofing.

Here is a link to using latex for painting.
http://www.modelairplanenews.com/how_to/latex1.asp

If you are interested in using the latex and/or glassing with water base polyurethane and need/want additional information, please feel free to contact me.

SoaringAce
Hi:
I'm sure there are many viewers in RCU land that are real experts that may respond to your post.
I'm not one of those yet however. There are a number on RCU threads that exist on this subject for you to research. Go for it.

I just finished a scale build project--Stafford 1/6 scale Piper Comanche. I too was very concerned with weight, but really wanted a smooth surface ready to accept paint. I had previously experimented with polyester type resins but read that they tended to be on the heavy side. I went looking for a light weight solution that would give me a smooth finish that I could paint, A finish that would accept panel lines, rivets, etc.
I settled on a thinned one coat epoxy resin and 3/4 oz glass; then 2-3 coats of water based poly urethane; automotive lacquer primer/filler as the surface ready for painting.
Here is what I found to work out wonderfully, I am extremely pleased with the end result.
I choose Aerospace Composite Products EZLAM resinsystem, and their 3/4 oz glass. This is an epoxy that can be 50% thinned with 91% isoprople alcohol
One coat brushed on and that was that. Then 2-3 coats of the MinWax poly urethane; spray on primer, sand off, and you have a super smooth finish ready to apply panel lines, etc. The weight issue: I think I added less then 8 oz to the basic dry weight plane with the glassing and finishing up to ready to paint. . It will be around 11 # painted.
I have heard also that many people like the West system, which is also an epoxy based glassing system.
As to ease of doing this glassing project, it was a breeze to do. Very little sanding, easy clean up, very little odder
Hope some of this helps.

BobM
nauticom

sir,
I hope you know that at about 40 lbs. you will have a very light model. It will fly very well at this weight ,but I have seen the weight up to the low 50lbs. and fly as if there was no difference. You must use the flaps on landing no matter what weight that you fly at so be aware of that fact. You don't have to fear useing the flaps either ie. pitch-up etc just carry some throttle till touch down. Some people think that they just want to keep it simple by not useing the flaps and wind up pranging their new bird from about 4 ft off the runway when it runs out of lift and belly flops.Ziroli builds good planes please follow what he recommends in the instructions and you won't be disappointed.
tom

Campy - would like to chat - sent you an e-mail.
Tom, thanks for the advise - I have spoken to several folks with differing opinions about flaps! 40lbs may not be achievable but I do not want to end up with a 55lb airfraft either. I am looking for the lightest solutions all round. Plans were followed accurately with recommended materials, so can't change that.
BobM, i have heard different opinions regarding epoxy vs. polyester resins. My local hobby store owner uses Polyester as he believes it is lighter than epoxy and easier to sand. Guess I need to experiment with samples of polyester, eposy, and polyurethane to see which is the lightest. The difficulty is going to be controlling the amount of each during application!
Tony E
SoaringAce

Another question - should the balsa be prep'ed (i.e. sealed) before application of glass and resin/polyurethane to minimize liquid penetration into the balsa (i.e., additional weight)? If so, what product is best and lightweight?

I HIGHLY recommend applying 1 thin - medium coat of a sanding sealer to the plane. When dry sand off the "fuzzies". This will not add very much weight, but it will keep the balsa from acting like a sponge and soaking up whatever material you decide to use to apply the glass with.

Balsa does not soak up epoxy like a sponge. If you do a test layup and pull the cured glass/epoxy laminate from the balsa you will just pull the surface balsa fibers off. I have done this test using different methods, don't ask how. Thinning Finish Epoxy does allow a very thin coat. Use a flexible plactic card to scrape off excess epoxy so that you can see the fiberglass weave but its still wet and transparent, if it looks smooth its to much epoxy. I find it produces a nice foundation. 3/4 or 1 ounce glass is not bad to work with.

Carl

Campy, can I call you to chat about this?

Of course. I will send you a PM incase you didn't get the email I sent.

I would agree with Carl's recommendations. I have used the same product and it does produce a nice light finish. I don't by into the sanding sealer approach. I have built LOTS of warbirds (very good ones too) and if you are judicious in your application of resin and primer you don't add that much weight. The best place to lose weight is before finishing begins. By that I mean using light weight balsa and composites and removing unnecessary wood i.e. fuse formers become pretty much useless after the fuse is built and glassed so you can remove most of them and save weight that way. I would also recommend using a roller to apply your resin, be it epoxy or polyester based. You will end up with an extremely even, thin coat. Lightly sand after wards and apply a second coat, sand again and prime. Sand most of the primer off and paint.