I've been thinking about some custom mods. I've never worked with Glass so I have been reading / watching ever post I can.

For my Projects I'm planning on using Styrofoam to make my 'Plug" and I read about using the following to seal it. Alum Foil, Drywall Mud, Wax paper Etc. I have a lot of left over Window Shrink wrap; you know the stuff you use for winterizing your windows. I'm thinking I can make my Plug Then Shrink Wrap it, and then wax the Shrink wrapped Plug. Will this work?

You can test how good it will work by putting some fiberglass on some of it. You might need a release agent to keep the fiberglass from sticking to the plastic sheet. You could try some Pam cooking spray as a release agent. Try to find the one with silicone in it.

quote Originally posted by avengador1: You can test how good it will work by putting some fiberglass on some of it. You might need a release agent to keep the fiberglass from sticking to the plastic sheet. You could try some Pam cooking spray as a release agent. Try to find the one with silicone in it.

Thanks Will keep that in mind. Now if it will just warm up so I can get to work

I agree. It would be easy to try a small test layup on a table top using exactly the same plastic film and resin you plan to use for the real piece. For what it's worth, I've used ordinary kitchen plastic film (like Saran Wrap) as a release film for small layups using epoxy resin. Conversely, epoxy resin does not work well with wax paper ... it tends to bleed through the wax layer and bond to the paper. I haven't tried this with polyester or vinylester resin, so I don't know how they would perform. It's always best to do a small test layup with your own materials before committing to the final part.

If you use epoxy resin and don't mind destroying the plug, you can do your layup directly on the Styrofoam. You can't do this with polyester resin, however, since it will dissolve Styrofoam. If you are using polyester or vinylester resin, you can use urethane foam (which will not dissolve in those resins) for your plug instead of Styrofoam.

Three final considerations: 1) Your plug will need to be everywhere convex for shrink wrap to fully conform to the surface. 2) You need to be careful ... the heat needed to shrink the plastic film may also melt the foam underneath. 3) The tension developed in the plastic film as it shrinks may locally crush the foam and thus slightly alter the size and/or shape of the finished part. There's no substitute for your own experience.

[This message has been edited by Marvin McInnis (edited 12-12-2005).]

quote Originally posted by Marvin McInnis: I agree. It would be easy to try a small test layup on a table top using exactly the same plastic film and resin you plan to use for the real piece. For what it's worth, I've used ordinary kitchen plastic film (like Saran Wrap) as a release film for small layups using epoxy resin. Conversely, epoxy resin does not work well with wax paper ... it tends to bleed through the wax layer and bond to the paper. I haven't tried this with polyester or vinylester resin, so I don't know how they would perform. It's always best to do a small test layup with your own materials before committing to the final part. If you use epoxy resin and don't mind destroying the plug, you can do your layup directly on the Styrofoam. You can't do this with polyester resin, however, since it will dissolve Styrofoam. If you are using polyester or vinylester resin, you can use urethane foam (which will not dissolve in those resins) for your plug instead of Styrofoam. Three final considerations: 1) Your plug will need to be everywhere convex for shrink wrap to fully conform to the surface. 2) You need to be careful ... the heat needed to shrink the plastic film may also melt the foam underneath. 3) The tension developed in the plastic film as it shrinks may locally crush the foam and thus slightly alter the size and/or shape of the finished part. There's no substitute for your own experience.

Great info

quote Originally posted by linenoise: Now if it will just warm up so I can get to work

It might hit 30 at the end of the week. Warm enough? BTW, still interested in the parts car?

resin will eat through thin plastic, i'd definately give it a try before i went for the real deal.

when it's colder you can just add more hardener and throw a heat lamp in front of it. i've done glass work outside in -15C before and had it set in about 3hrs. wouldn't recommend it, but if it NEEDS to be done it's possible. anything above freezing would be ok i'd say, but read the instructions on the resin to be sure.

if i were you, once i finished the styrofoam plug, i would apply some body filler over top. that way you can sand it smooth to the perfect shape, and the glass won't eat away at it. you will need to use some release agent if you won't to seperate them easily afterwards though.

Lots of misinformation there! Sorry, but I have to say it.

quote Originally posted by fierce_gt: resin will eat through thin plastic ....

Caution: What kind resin will "eat through" what kind of thin plastic? You need to be more specific.

quote Originally posted by fierce_gt: when it's colder you can just add more hardener and throw a heat lamp in front of it. i've done glass work outside in -15C before and had it set in about 3hrs. wouldn't recommend it, but if it NEEDS to be done it's possible. anything above freezing would be ok i'd say ....

Warning: Again, the question is, "what kind of resin?" You might (or might not) be able to get by with this with polyester or vinylester resin, but it definitely won't work with epoxies!

quote Originally posted by fierce_gt: if i were you, once i finished the styrofoam plug, i would apply some body filler over top. that way you can sand it smooth to the perfect shape, and the glass won't eat away at it....

Warning : Polyester-based body fillers (like Bondo) will dissolve Styrofoam.

[This message has been edited by Marvin McInnis (edited 12-13-2005).]

Some types of styrofoam will not be affected by resins. Ive used it and covered it with a thin layer of ordinary body filler. sanded it smooth, primered and painted with gloss paint. Then used a release agent like Pam or several good coats of paste wax.

quote Originally posted by rogergarrison: Some types of styrofoam will not be affected by resins. Ive used it and covered it with a thin layer of ordinary body filler. sanded it smooth, primered and painted with gloss paint. Then used a release agent like Pam or several good coats of paste wax.

NO you just got a good seal
polyester will eat styrofoam [closed cell] looks like bubbles
anyway the proper urothane foam is eazyer to shape [open cell] looks like a sponge

------------------
Question wonder and be wierd
are you kind?

quote Originally posted by Marvin McInnis: Lots of misinformation there! Sorry, but I have to say it. Warning : Polyester-based body fillers (like Bondo) will dissolve Styrofoam.

that's all fair enough, and i'm glad you posted. although misinformation is not true, everything i posted is 100% accurate(as per my experience of course), it's just far to vague, and i left out way too many details. Good call on that!

i should have included that everything i submitted was from PERSONAL EXPERIENCE and should be used as a guideline at best.
my procedure is to used kitty hair on top of expandable foam. and it has worked with what i use. to be absolutely sure it would work for you, you'd have to use the exact same stuff i do.

i think a lot of misunderstanding is coming from styrofoam compared to expanding foam. i was talking about expanding foam(slipped up at the end and said styrofoam), which most definately will not dissolve when bondo is applied to it.

as for the plastic, think "party cups". the resin i use will turn one into a small puddle within the hour. a coke bottle however seems to work no problems.

i guess the moral of the story is that you HAVE to try it out before you can count on it. the corrections simply emphasize that. using a different resin could greatly affect what will and won't work. so please, whatever you decide, try it out, cause the last thing you want to is to make a mould of a melted piece of styrofoam

[This message has been edited by fierce_gt (edited 12-14-2005).]

quote Originally posted by fierce_gt: that's all fair enough, and i'm glad you posted ... i should have included that everything i submitted was from PERSONAL EXPERIENCE and should be used as a guideline at best.

Thanks for a thoughtful post. I should have been more diplomatic with mine. I just want to be sure that people have accurate information available.

There are three general families of plastic foams widely available and commonly used for fiberglass work: polystyrene (trade name Styrofoam), urethane, and polyvinyl chloride (PVC). These plastics have very different chemical properties from each other, and are all available in many grades with different mechanical properties. Polystyrene foam can safely be hot-wire cut, but urethane and PVC emit deadly cyanide gases at hot-wire temperatures. Urethane is the most resistant to solvents, while polystyrene is the least resistant. PVC is generally the strongest but the most difficult to shape. All three foams are available in sheets and blocks, but most common expandable (expand in place) foams are urethanes.

Similarly, there are three general families of plastic resins widely available and commonly used for fiberglass work: polyester, vinylester, and epoxy. These three resin types have very different chemical and mechanical properties. Polyester resins have been used for a long time in boatbuilding, are the most widely available and the least expensive, and are pretty easy to work with, but have the poorest mechanical properties when cured. Vinylester resins combine most of the desirable properties of the polyesters with significantly improved mechanical properties, but they are more expensive, more difficult to work with, and less widely available. Epoxies are the most expensive and most difficult to work with, but generally offer the best mechanical properties when cured.

Polyesters and vinylesters are cured by addition of a very small amount of catalyst that causes the molecules of liquid resin to link up into a rigid tangle of very long molecules, and the cure rate is more or less proportional to both temperature and the amount of catalyst added. Conversely, epoxies are two-part resin systems, and epoxy cure is initiated by mixing the two components together in precise proportions; the molecules of the two parts then cross-link (link up to each other) into a tangled lattice structure. You cannot accelerate the cure of epoxies by altering the mixing ratio of the two components, but the cure rate is strongly affected by temperature.

Polyester resins will dissolve polystyrene foam, while epoxies will not. Conversely, all three resins can generally be used on urethane foam without problems.

One caution about working at low temperatures: At low temperatures, epoxy resins can partially cure to a "green" or "glassy" state and then stop curing. If this happens, the resin may never fully cure (even when subsequently heated to normal temperatures or above), may remain soft and gummy, and may never develop full strength. At sufficiently low temperatures this can happen with polyesters and vinylesters as well, no matter how much catalyst you use. Your best bet is to always observe the temperature limits specified by the resin manufacturer.

Incidentally, all of the information presented here is based on both research and many years personal experience building automobile, boat, and aircraft parts. I have extensive experience working with epoxy resins, somewhat less with polyester, and I have only recently begun working with vinylesters. Whatever resin system you use, it's important to understand the characteristics of the materials you're using and to follow the manufacturers' guidelines carefully for your first few layups. Only after you have accumulated some experience with a specific material should you begin to experiment "outside the box."

There is a wealth of information on fiberglass materials and techniques available in the homebuilt/experimental aircraft community. Some good resources are the Experimental Aircraft Association, Aircraft Spruce & Specialty, Wicks Aircraft Supply, and West System.

[This message has been edited by Marvin McInnis (edited 12-15-2005).]

Well said, all around.

For the original question in this thread, your best off to purchase the right type foam. It will be easier to shape and will work with your layups. It's worth the $ to just order a small kit, ship it, and use it.

What kills me is how someone wanting to dabble in fiberglass will try a whole bunch of shortcuts from the start. That's great, but often it will cause something to go wrong with the project, and the creative process gets killed.

Best advice, use all the proper materials all the way thru a few times, then start looking for shortcuts.

[This message has been edited by opm2000 (edited 12-14-2005).]

Great info Marvin. as a simple hobbyist i never really thought that much into different materials. i just stuck with the off the shelf polyester resin for my projects.
anyway thanks for the great replies and understanding!

quote Originally posted by fierce_gt: as a hobbyist i never really thought that much into different materials

Building structural aircraft parts from fiberglass composites necessarily requires a different approach. Reminding yourself that "Someday you're butt is going to be 2 miles above the ground in this airplane and your life is going to depend on the strength and quality of this part" can do wonders to focus your attention!

[This message has been edited by Marvin McInnis (edited 12-15-2005).]

i just finished adding air sccops to the lbottom of a lamborghini kit bumper. i used sheet urethane
cut to the contour i wanted. i bonded the form to the bumper bottom. i covered it with fiberglass mat with
polyester resin. this was followed by reinforced bondo. a lot of work, believe me.

quote Originally posted by pprbart@cs.com: i used sheet urethane

Really... got a source link?

quote Originally posted by ryan.hess: Really... got a source link?

As I posted earlier:

Aircraft Spruce & Specialty
Wicks Aircraft Supply

home depot sells it by the sheet. it has a skin backing but for my design i cut it into 2" by 24"
strips and glued it together with hot glue gun. the contours were already cut before gluing.

Sorry, thought we were talking about actual "sheet" urethane, not foam...

Take a look at this.

http://technicalvideorental.com/rental_6.html

quote Originally posted by texasfiero: Take a look at this. http://technicalvideorental.com/rental_6.html

Has anyone tried this service?