Jetset

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A couple of question on plugs and molds.
I was thinking of making a plug from styrofoam. After getting the shape-or close to the shape-What is the material to finish it? I guess I should say cover it? Do you fibreglass it? Same goes for the mold.
What do the majority of plug and mold people use for fibreglassing? Is it just normal epoxy and fibre for ....lets say...the mold? How thick? Do you put the cloth on in layers or one thick layer?
Sorry for all the questions but I was thinking of giving this a try soon!
I want to try a few smaller parts first then work up to a fuselage.
Thanks for the help!
Myles

Ollie

I cover foam plugs with several layers of very light cloth in low viscosity epoxy. West Systems epoxy sands easily after full cure. I use light cloth (1.5 oz. per yard) for several reasons. It drapes easily around sharp compound curves. It is only 0.02 inches thick so the edges are easy to fair. The weave is tight enough that little if any filling is required. If the cloth is cut on the bias it has much less tendency to unravel. Depending on the plug size and pot life of the epoxy and hardner, I can put up to four plies of glass cloth on in one session. An extra layer of glass in epoxy can be smoothed by sanding and scraping so that no filler is required before waxing the plug.

Mike James

There's a lot of good (free) information on the web about this process.

Try some of the freely downloadable stuff at http://www.fibreglast.com and also at http://www.ac-composites.com

I also have a non-commercial web site, devoted to this stuff. (below)
Good luck! Warning... Molding is addictive!

paperairplanes

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im using pretty much the same sequence as ollie is. right now im making a plug for a f-100, 57 span for df. like Mike James said, this is addictive. check out mikes site, tons of info and ideas. He is who gave me lots of ideas for trying this out. Right now im using west systems epoxy with good results. Pretty much I just use 2 layers of 3/4 glass over the plug. As for the mold, I pile the glass on, usually up to 7 layers starting with thin glass working my way up to the thicker cloths. As for actually layers of glass used in the fuse, I am experimenting with this. I am also experimenting with some of the carbon kevlar cloths. One little tip I would like to add here when making your molds, cut out some plywood to fit the outer part of the fuse mold, and glass it to your mold, after it has cured. It makes a convenient stand when you flip your mold on its side to lay in your fiberglass fuse.

TiGuy

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There are as many ways to make a plug as there is to crash. I have been having good luck with blue foam. Its much more durable and firm than white foam, but is still easy to carve up. I cover with many layers of 3/4 oz cloth with EZ-Lam epoxy (which is easy to sand too)

The mold needs to be VERY strong, so many layers of cloth need to be used. The mold should be at least 1/8 thick. I like to add aluminium "L" beams to the outside for stiffness and as a stand like paperairplanes mentioned with plywood.

It really helps to find someone in your area to SEE what goes on in this process. There is a lot of great information out there, but it could also be considered too much when you start to look for advice.

Yes, the final product is the goal, but making the tools can be just as addictive if you ask me.

Jetset

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When making the plug, I guess I would have to consider the thickness of the glassing over top of the styrofoam 'eh? I mean if i molded the styrofoam plug exactly to the shape that I want THEN glass over top of it as the finish, it would throw out the dimensions of the plug right? OR......does the finish not have to be that thick but rather just thick enough to smooth out the foam?
Whew, I hope everyone can understand what I just said!

TiGuy

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We're probably talking about less than 1/32 of an inch total extra "width" of glass. I usually end up with 2 layers of 3/4 oz cloth ( with a few patches of an extra layer here and there) If that is a concern...then you will have to factor that in...but good luck!

Mike James's site - www.nextcraft.com is very good! Thanks for posting it all Mike!

Ollie

Three quarter ounce cloth is only about 0.001 inches thick and 1.5 ounce cloth is only about 0.002 inches thick. How many layers you use depends on how strong you want the plug to be. This depends on how difficult the shape will be to get out of the finished mold and whether you want to save the plug undamaged after removal. For first projects, I would recommend at least 6 layers of 1.5 ounce cloth on the plug. With experience this can be reduced a lot. You will probably have more trouble controlling the shape of the foam while it is being formed than allowing for skin thickness. As the internal stresses are relieved in the foam as it is cut, it tends to warp a bit. You should rely on external templates rather than reference lines on the foam while shaping. High precision can be achieved with practise.

Jetset

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I'm learning lots here! My plan was to use doorskin plywood for the cross sectional formers with white foam in between. Does this sound good so far? The reason I'm choosing the white foam is because I have access to all kinds but I guess it would a little more difficult to work with than the blue. Would spackling compound be good to use to fill in lareger holes for when I screw up before I glass? Or what's a better option for filling in the white foam.
Thanks again guys! :thumbup:
Myles

Mike James

I do two things a little differently...Just personal taste.

First, typical white foam is going to require a lot of filling, and so will the tiny gaps where the foam meets each of your bulkheads, unless you're very precise about it. I recommend a built-up structure, or at least some denser foam. You basically end up using epoxy as a filler, (because it "sucks in" everywhere) it can get expensive, messy, and hard to sand. The more uniform your surface texture and hardness is, the better you'll like the sanding phases.

Also, about the lamination of the plug. I like for my plugs to be tough, so I can keep them around for a while, and make more molds if I decide to. So...

I do a precision shaped, but not detailed (no panel lines, rivets, etc..) plug, then I first glass with 6 oz cloth, then 4 oz. cloth, then 2 oz. cloth. The other cloth you guys mention is pretty fragile. Any details like panel lines and rivets are added AFTER the glassing and re-sanding, insuring that the shape is correct.

Plugs made this way, especially if coated with a tough "tooling resin" at the end, will last a long time.

Bruce L Prater

REMEMBER...what the plug looks like and feels like is what the part will look and feel like when you pull one from the mold. If you plan on building more than one mold, your plug will need to be strong enough to last for this, if you are only wanting to make one mold then the plug doesn't need to be made so strong. You can make a mold too stiff, makes parts harder to get out. The mold only needs to be strong enough so that it won't warp easly. One thing to determine how strong to make your mold is, how many parts, and how often do you plan on pulling them. I've made production molds fairly thin and used them daily, they lasted for a long time. Most damage done to molds is from pulling parts, cutting into mold when triming or scrathing while trying to pry parts out. If you are only going to make one mold from a plug you can use bondo over foam, sand, paint, wax and pull your mold then throw the plug away. Like the others have suggested, go to the web pages for good info. Remember this, it is easier to sand and fix places on plug than it is in a mold. I make my molds slick enough that the don't need any sanding on them before use.

Goggles

My Feedback: (4)

Myles ,

Your idea of using the door skin would be a good one, but an easier thing to use is paneling. Not wood paneling, but the real cheap pressed paper paneling. One side looks like regular fake wood, but the other is very smooth. It's about $10-12 cdn for a 4x8 sheet. Home Hardware, Revy, so on stock them. I use this all the time for any templates of bulk heads or what every else I can think of.

For the plug I found pink foam much easier to work with than white foam. You've been to my one web site showing the progress on the B1B and you can see that the white foam sticks to EVERYthing . My poor daughter was helping me and we were a mess after cutting and triming. I then use drywall compound to fill any voids and shape. Careful what you use to fill with. Some fillers, like automotive body filler, will desolve the white/pink foam. Then 2-2 oz layers of FG cloth. Sand, prime, paint, wax and use PVA mold release. Like Bruce said, every flaw WILL show up in the mold (that's why I don't have anyting big for sale yet).

For the mold I use 1 thick layer of black tooling Gel-coat, 2 oz cloth, 2 layers of 1oz matte (very strong) and another of 6oz, letting dry slightly between each step. I use polyester resin for this step cause it's very much cheaper than epoxy. Caution, use plenty of ventilation.

For the glass parts, use epoxy. I've tried ploy and also epoxy....use epoxy. It's much more expensive ($28 for 750ml) but you don't need a gas mask to use it. I have found it also sands much easier. So far on some of my parts I've been using 1 layer 2oz and 2 layers of 6 oz, and that seems quite strong. More testing has to be done as to how strong but so far so good. On my wheel pants I also include a strip of 9oz military grade volan cloth. Very strong stuff.

I hope this has also helped you out, don't hesitate to ask more questions.

Thanks,

Kelvin.

LGEdge

Kelivn

Where do you get the black tooling gel-coat from. Iam making my first plug and mold to. How is this to spray can I use a cup gun.

Goggles

My Feedback: (4)

I get my fibreglass supplies from a place out here called Fiber-tek. I found them in the phone book. I don't think they are across Canada but try looking in your phone book. I think it's about $20 a L.

An ordinary spray gun will not shoot this stuff on. You need a special Gel spray gun, or what I use is a brush. It goes on real thick (1/16") and there are no brush strokes left behind. It makes for a very smooth and hard surface. Only draw back is it's smell. Again, plenty of ventilation, or just do it out side. There are a few tricks and mistakes that can happen so when your ready to do it, contact me and I'll try and help.

Don't forget to buy lots of Acetone for the clean up

Jetset

My Feedback: (2)

For fun I took some some fibreglass cloth that I bought at Candian Tire in the boat repair section. I wrapped it around a carboard tube covered with wax paper and used 30min epoxy. What I was trying to accomplish is a fan housing for one of my jets.
Now, when you say use epoxy, are you talking like the stuff you buy at the hobby store ie.-Hangar9, or something different? Cause my fibreglass tube that I made seems rather flexible and the epoxy has cured all the way. the cloth was kind of thick as well although I'm not sure of the weight but it looks as thick as or maybe thicker than the fuselage on my Sport Shark.
What do you think guys?
What am I doing wrong?
Be gentle, for I am a fibreglassing virgin!
Thax!
Myles

Goggles

My Feedback: (4)

When I started making my wheel pants, I experimented with a few different adhesives to use on the joining tape. I tried 5 min, 30 min epoxy, thin CA glue, Zpoxy finishing resin and then what i use for making the parts, Fiber Craft Aqua-set epoxy resin.
The 5 and 30 min are to thick and CA simply doesn't work well. Zpoxy finishing resin works well. What you need is a epoxy resin.

Now when you made the tube, did you put on 1 layer or multiple? Multiple is better. I think I seen the glass you have and it's probably a 6oz or higher thickness. That should work.

I also am very new to glassing and there is lots to learn, but this is what I have learned by trial and error so far. I hope others can reply with their experiances so we both can lean.

Ollie

West Systems epoxy is probably the most versitile. There are four different hardeners with pot life from 15 minutes to 60 minutes. There are about 6 or 7 additives to control strength, density, viscosity, etc. It sands well when fully cured. It does not respond to post curing. It is available in marine supply stores and from Aerospace Composite Products.

MGS and ProSet epoxies are harder than West Systems and make stronger laminates. They can be post cured for even greater strength. They are available from Composite Structures Technology.

LGEdge

I tried some Aeropoxy from Aircraft Spruce to cover a plug out of foam. It seems to be staying a tacky form on the sureface. Is this normal or is this not good. They say they use this on full scale aircraft.

Mike James

I've used lots of brands of polyester resin, but don't have much to say about it... Some were consistent, and some weren't. I never made anything large using polyester resin, because the heat buildup can be a little tricky.

When it comes to epoxy, I've used only two company's products for my plugs and molds. (NEVER "hobby-type" brands for laminating something like a fuselage plug) The first ones, when I was living on the east coast, came from FibreGlast, Inc., in Dayton, Ohio. ( http://www.fibreglast.com) I had consistently good results with all their epoxy-related products, their cloth, fillers, and service. I also used their "Akemi" product, which is a VERY hard tooling resin, for the surface of my plugs. It was way too much work to sand, but certainly created a bullet-proof plug. (My first molded "sport prop jet" from around 1992, is still shown on one of their pages, along with Mark Frankel's "Skyray" and others.)

When I moved to Alaska, I started using the West Systems epoxy, (available everywhere) and have been equally satisfied. I'm looking for a good tooling resin...something not quite as hard as "Akemi", but tough enough for protection under normal standards.

That's not to say that other brands aren't equal or better for some applications, but I can tell you that the two brands above offer no surprises. (and that's a good thing)

I recently watched a videotape of a real craftsman, (Fred McClung, making wing molds and parts for the "Fred-A-Plane") and it made me realize that if we just pay a little more attention to details, we can produce precision models using relatively simple tools and materials. (and a little more effort)

"Brands" and "Products" would be a good topic on this forum, as long as it doesn't get off on any negative tangents. Maybe if we all specifically state what we use, for what purpose, it will take a lot of the mystery out of it. I'm always looking for anything that improves the quality of my "stuff".

Good input, everybody!

Goggles

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hmmm....I like your idea about the brands/products reviews or applications Mike.

Jetset

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I'm learning lots here guys! Thanks for the info!
My fan housing is only one layer. I think I will try another layer over top and see what happens! What should I clean the housing with before I try this? Alcohol?
Thanks!
Myles

k_sonn

My Feedback: (32)

I see a lot of information if one was using foam to make a plug and mold. What if I wanted to make a fiberglass fuselage of say a top flite corsair? How would I go about accomplishing this task? The fuse is built and sheeted at this time.

Mike James

It doesn't really matter what you make your plugs out of, as long as the shape is right. I prefer a built up structure, because it's more precise than foam at the outset, and a lot easier to glass. (less filling and sanding)

Just make sure that your "draft angle" is 90 degrees or less, everywhere. In other words, make sure that there's nothing about your plug's shape that will cause it to be "locked" into the mold. If you make a left and right mold half, with the centerline running down the length of the model, your idea will work fine.

Check out some of the sites mentioned earlier in this thread.

k_sonn

My Feedback: (32)

Thanks Mike.

Craig-RCU

To make your balsa sheeted fuse into a plug for a fiberglass mold, you prepare the surface the same as you would a foam plug (i.e. a layer of fiberglass or monokote depending on how perfect you want your finished mold to be) and then make your two part mold from that same as with a foam plug.