GLASSING SNAFU
 

Howdy, as usual [with F/G work] I came up with a 99% good result. Too bad that isn't good enough. [&o]
This plane is going to be a "fun scale" .074 powered Blackbird, so keeping the weight down to minimum is important.
I brushed on a primer coat of finishing resin on the foam and gave it a few days to cure, then sanded off the fuzz. The build up looked good enough to go for the next layer to be with 1.5- 2 oz cloth. I guess I was wrong. The cloth laid down real nice as I was working it, but the following day the results I have with all the little air sacks of loose cloth leave me shaking my head.
How should I fix this mess?

RE: GLASSING SNAFU
 

if you're trying to get it light you should sheet it with 1/16" balsa and use covering. you could also use 3/4oz glass over the sheeting and then paint but the iron on covering is by far the lightest choice. the sheeting and monokote would weight less then the finish resin that soaked into the foam on your 'Primer' coat.

RE: GLASSING SNAFU
 

CP
How about cutting around two thirds of the bubbles, and use some more epoxy to stick it down. It does not look all that bad and should not be a lot of added weight. As far as Monokote, despite popular opinion it is not all that light a finish from the tables Darock posted in the kit build forum.

Is this build inspired by funkworks?


Edit to add:
I wonder if you had some dust or oil on the primer coat that keep it from sticking down in the first place, kinda weird it did that. I like to wet my glass while it is on a piece of plastic film, cover it with resin then put it on what I am glassing. Then pull the plastic off and scrape as much resin off as possible to make sure it is going to lay down good. And invariably I end with bubbles still so don't feel bad about it.
I think the only way you can insure an optimal bond is to use the bagging system, and it still would screw up on me...

RE: GLASSING SNAFU
 

Thanks IE, that sounds like a workable solution here. Yes, FWs' plane got me going on this one.....but this one is so far from scale that is where the comparison ends. Being a belly lander, I want to keep the nose of this one from tearing off, but good landing technique with a light plane is the best strategy instead of building a heavy lawn dart. I was torn between the traditional foam/balsa sandwich and just plain F/G over foam, then paint. The jury is still out, all this painstaking touch up work on the glass will take at least an hour, then there will be primer/sanding sessions to fill the weave. It still isn't too late to cut the foam fuselage out and chunk it up into bulkhead stations and build a traditional "boat style" fuselage out of balsa.

RE: GLASSING SNAFU
 

Looks like resin outgassing.Maybe try resin injection in the air pockets with hyperdermic needle. Easier than sanding and filling.

RE: GLASSING SNAFU
 

CP
A hour is not all that bad to get it back to a level that you would like is not all that bad. It has taken me longer to sand out the tail feathers for my SE build, although I haven't been working on it that much this week.

It looks like a nice build you have got going there go for it!

I'd try the foam method you are using it should be fairly light.
With your building skills you might be able to shave off a bit with a traditional balsa build but I be willing to bet it be a lot more work.
Two .074s this baby should honk!

Post a picture when you get her done!

Best wishes
Paul

RE: GLASSING SNAFU
 

Paul, sure will. Might even buy a camcorder :eek:? I'm never after museum quality, but it has to look a little bit better than a severe case of acne ;).

RE: GLASSING SNAFU
 

I don't like them to lumpy myself.:D
But then there is what I end up with... That is why I am trying the carbon fiber and dope thing my CL buddy uses on the SSE I am building, sanding dope is not all that bad. All the coats, well that is a pain, not to mention heating the outside to vent the fumes[sm=spinnyeyes.gif]
But to be honest it does not look all that bad, but I hear you.:eek:

RE: GLASSING SNAFU
 

c cat, I've never heard of the out gassing. I did see some air bubbles form and stick at the surface.

RE: GLASSING SNAFU
 

It occors ocasionally when resin begins to kick, the heat generated will draw air into or against the laminate from the substrate (in this case foam). Best bet for prevention would be to sand foam with finer grit paper to close up porosity. Just my 2cents.

RE: GLASSING SNAFU
 

Thanks, Ccat. I didn't have the foam prepped as good as I could have after the primer coat of resin.

RE: GLASSING SNAFU
 

Magic Wand for air bubbles found at http://www.shopmaninc.com/fgrollers.html

http://www.shopmaninc.com/Images/fgr2.gif

Given your scenario, sounds like the bubbles were due to something other than an application SNAFU. I would recommend one of these notched rollers (I use them in every layup I do to eliminate air bubbles) but check the project periodically during the cure. If you catch these kind of bubbles in the gel phase, you should still be able to work them out with very little chance of them returning.

Besides the air pockets, that's a gorgeous layup.

RE: GLASSING SNAFU
 

but if you already had a thin coat of resin on the foam, then there should not have been much foam for the next coat to interact with. The heat from such a thin layup would be very, very minimal and I would expect that the ingress of air was due to a temperature change in the area you were working in rather than the exothermic reaction of the resin.

RE: GLASSING SNAFU
 

Thanks for all the input. I've seen other guys use the same basic steps and materials and get very neat results. I know that all the master modeling books stress doing a dry run with the techniques you plan on using off to the side for practice.
I've found that drawing a single edge razor over the surface does a nice job of scraping the bumps off. I've epoxied the major bubbles down after peeling the loose cloth back.
Thankfully the finish will be flat black on this model ;)!