Conference vmszoo::rc

Once you put something over the foam to seal it, you can use anything. The 
fiberglass over foam stuff in here is all epoxy resin. Polyester resin will 
destroy the foam as you've found out.

Most of the fiberglass stuff in here involving polyester resin is over sheeted
wood surfaces as a finishing step before painting.

The automotive resin works fine in non-foam applications and actually has less 
wax than the "hobby" brands.

    Epoxy resin is stronger, more expensive, and takes much longer to 
    cure than polyester resin.  I strongly recommend using epoxy resin
    such as West or Saf-T-Poxy for modelling applications.  
    
     
                                                     Regards,
    
                                                     Jim 

>    Epoxy resin is stronger, more expensive, and takes much longer to 
>    cure than polyester resin.  I strongly recommend using epoxy resin

I disagree with "Stronger".

Dodgson fuselages (and Steve Schommer fuselages for that matter) are
made of polyester resin.

Dodgson first made them from Polyester then switch to epoxy a few
years ago then switched back.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Ah, so the Lovesong must have been made during that "weak" epoxy
    period, which caused the fuse to break, eh kay??
    
    :-) :-) :-)
    
    jeff
    

    Yes but what do you put over the foam to seal it so that it wont be
    destroyed by the resin?.
    
    Jacques
    

    
    More detail to my question: I don't wnat to sheet it. Would Saran wrap
    do the trick
    
    Jacques
    

    Jacques,
    
           If I understand your question correctly, you want to cover
    foam with epoxy, but not use any sheeting material to stick to the
    wings/fuselage?  What exactly are you trying to do?  Make a mold?
    
                                                      Regards,
    
                                                      Jim
    
                                                 

    Not exactly, I'm would like to use the foam as the shaping material,
    but I don't want to use sheeting because of cost. I need a material
    that will not be affected by water or salt, that is thin enough so that
    it can follow intricate curves ( radius as small as 1/16" in some
    cases). I don't want something part foam for the big surfaces and part
    wood for the small intricate curve. What I want to do is develop a
    shape in foam and directly recover it with fiberglass for strenght.
    
    The reason behind this is to try to eliminate intermediate molding
    (meaning create a shape in foam and with it create a female mold and
    with this create the final part) I want to eliminate the need for a
    female mold altogether. I know that it is difficult to get a good
    smooth and straight finish by applying fiberglass directly on the foam
    but I had good success with the speed boat.  The other goal is cost,
    for now I will practice with small models but eventually I want to go to
    1/4 scale model and then to full scale, so the sheapest the better. You
    can see that sheeting a full scale car or boat with balsa would be
    rather expensive. I don't really care if the foam is trap in the
    fiberglass for now I can always disolve it after thru a small hole in
    the fiberglass.
    
    Jacques
    

So use 2 part epoxy - it won't hurt foam.
The most economical is the stuff they use for commercial floors at
Summerville Lumber.  It used to be called Safety Poxy (I think).
Anyway they have it in various sizes - that's what I use for bonding
my wing sheeting to my wing cores.

You must use it at the right temperature and mixed accurately.
Wait 24 hours.

Then wait another 24 hours.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

Since we're getting into the more serious techniques, I'll refer you to the 
August 92 issue of Model Airplane News. I don't know if it's available over 
there but page 107 has the article by Michael Lachowski on preparing hollow 
wings using Rohacell and epoxy over foam "molds". I can interoffice you a 
photocopy if you can't get the original.

This sounds like it's exactly what you want to think about. I personally don't
think that epoxy is less strong than polyester resin. I have molded with both 
and prefer the epoxy method due to the lack of fumes. Strength copmes from the
cloth you use and Spectra and Kevlar are replacing fiberglass in this area. I
believe (Jim Blum should be able to verify) that Frank Weston is using epoxy 
for his designs. The biggest problem is curing time. Epoxies are slower but 
this also allows them to soak in better. Epoxy is also more flexible than 
polyester resin and I think this is a benefit rather than a shortcoming.  

Really depends on the application.

Re: .9

Do they have Sommerville lumbers overseas 8^)

Actually the stuff I'm currently using is called EnviroTex-Lite and it's a 1:1 
epoxy that cures in 24 hours (above 20 degrees Celsius) and is used as a clear, 
thick bar top sealer. I buy it by the gallon set and it works great. A little 
heat and it flows like water. Slow curing allows it to soak into whatever your 
"wetting" with it.

Many people are wrapping their "projects" in old electric blankets to keep them 
at curing temperatures when necessary.

    Jacques,
    
           Since it sounds like you are into fabricating boat hulls,
    I would recommend you read the Gougeon Bros. book on boat con-
    struction.  They were the originators of the W.E.S.T.(wood epoxy
    saturation technique)system of construction and market a line of
    tools and epoxies to build with.  This method is commonly known
    as "cold molding" in boating circles and is reported to result in
    very light, strong, low maintenance hulls.  The philosophy being
    that wood(plywood) is an excellent material for boat hulls but
    required a lot of maintenance.  By saturation the wood with epoxy
    resin, the structure becomes stronger and waterproof.  Boats using
    WEST construction are reported to be lighter than similar boats
    built in fiberglass.  The youngest Gougeon built a trimaran sailboat
    that hit 60 mph!  The gougen also built windmill blades using the west
    system that outlasted ones built with TITANIUM by NASA.  It is really
    verfy interesting reading.
    
                                                       Regards,
    
                                                       Jim
    
     

    re: -2
    
    I have used Enviro-Tex quite a few times myself.  On a number of
    occasions it failed to fully cure.  I do my "glassing" in my 
    cellar which is quite humid and maybe it was too cold or something.
    
    To be safe do not epoxy large surfaces below about 70 degrees and
    preferably on low humidity days.  The winter is the best time for
    me because the furnace keeps the cellar warm and dry.
    
    I have noticed that the laminating resins are much more prine to
    this non-curing, probably owing to the long set time.  Enviro-Tex
    does generally work well, is readily available and priced right.
    
              
                                                      Regards,
    
                                                      Jim

I have the opposite problem. My basement is unheated and becomes humid in the 
warmer months. I run a dehumidifier all summer and in the winter I do my bagging 
inside a wood drying kiln that I built and can keep at 80 degrees. It does seem 
to be ratio sensitive and you need to mix it quite well but having done all 
these things, I've had cured wings in 24 hours and fully strength in a week. 
I've been bagging a panel every other night for the past two weeks in order to 
get caught up. I hadn't done any in the last 6 months and had developed a 
mental block. Finding the tape method of preparing the sheeting helped there.

Re: saran wrap on core.

This will probably work but I would use something heavier like 4 mil plastic 
as a barrier. Test what ever you use with the resin to make sure it doesn't 
desolve like the foam. I use wax paper when I'm bagging as a barrier (but that's 
epoxy)

    I have been using Enviro-tex for several years and I've had great luck
    with it.  You need minimum 70 degrees for a good 24 hour cure though. 
    It will cure much faster if you warm things up over 80 degrees.  I just
    finished sheeting the foam wings for my pattern ship with it and they
    came out great.  You need to mix accutately!  I thin with alcohol
    before applying to the wing.  I have used it for sheeting and glassing
    and I would never use Polyester for either.  Epoxy smells less and I
    think it's easier to work with.
    
    Charlie
    

I guess this is the right place, though I was tempted to put it in one of the
other glassing topics.

I've never done any off this stuff, the closest is using glass or Goldberg
Nylon tape at wing halves.

I have the SureFlight ALL FOAM P-39 plane kit that has been sitting around about
1 1/2 years, and I thought I'd finish it this Winter.  They say you don't have 
to but that you can glass it.  I would like to put a thin glass finish on it
and then paint it with epoxy paints (like lemon yellow and electric blue and
black :-). This will have NO sheeting on it.  

What methods do I want to use for this?

Thanks
Chad

More update to .16:

Ok, the goal is 

* to try out glassing on an expendable plane
* to provide the foam some protection and the plane some extra strength
* to have a nice finish
* do this cheaply
* try something besides iron-on films


non-goals

* get the perfect finish  -- this will be handbrushed, not sprayed (no spray
 stuff and the finish does not have to be perfect)
* spend tons of time onthe glassing
* go broke on equipment and supplies

I didn't have a chance yesterday to comment back on this. One thing I think 
you might try would be to apply .6 oz cloth with clear epoxy paint. I did 
this on a wood model and it worked out quite well. The epoxy paint won't 
attack the foam and it is thin enough to brush on and will capture the cloth. 
The down side of what you are doing is that you are adding weight to a foam 
plane which probably already has a high wing loading (most foam ARFs do) so 
you might be creating something that can only hang from the ceiling. You are 
also removing some of the "flex" in the foam surfaces which may cause them 
to break rather then bend in a crash.

If you decide to glass the ship I recommend iropning the glass cloth on a low 
temp setting to take out the folds since the epoxy paint will dry a little 
slow and the folds will probably have enough force to create bubbles. I 
usually iron my cloth between a couple of dish towels on a very low setting. 
I raise the temp until I can press out the folds and then cut/use the cloth. 
I wish manufacturers would roll the cloth instead of folding it into 
packages...

Thanks Jim

I read about your method a little (mainly comments on it) in the part of
"Let us Spray" that I read.  It sounds the easiest.  I'll read up. The plane is a
Styrofoam thing and it recommends glassing for experts, otherwise some
low-heat iron on.  Styrofoam is not that bendable/"flex"able (as opposed
to flexible) anyway.


Well, I figure that I am not an expert but it would be a good
thing to try it on (better than any masterpiece I have not yet built).

Regards
Chad

    Can one of yu guys direct me to the note number which explains how to
    use a mold and make a fiberglass cowl and front end?
    
    I am building a Ford Tri-motor and the front end which covers the
    engine mount (sort of a box) and round engine cowl.  I have made this
    part out of balsa and feel it will not hold up under use and want to
    build it out of fiberglass.
    
    I have use the "Dir/Title= *fiberglass*" command and read the notes and
    do not find any insturctions on this subject.
    
    Thanks for any help you can provide.
    
    Ollie
                                            

Topic  Author               Date         Repl  Title
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  871  SA1794::TENEROWICZT   3-FEB-1989    15  Fiberglass Components