RE: Anyone know where I can get Windscreens?
If you're just replacing windscreens with different-colored (but same-shaped) versions, you can use the originals as molds to cast plaster positives, then vacuum form new ones over the plaster casts. That's way easier than carving and sanding your own molds. For your personal use, that's probably "fair use" and perfectly legal. (You already paid for the windscreens, and you're effectively just changing the colors.) Just don't sell your copies of somebody else's presumably copyrighted shapes.
Posted on: 12/1/2007 4:02 PM by Author "drcrash" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=6700262

RE: Using an ABS moulding as a mould for fibreglass lay-up?
It's pretty common to make molds by vacuum forming. (For chocolates, soaps, candles, decorative concrete, etc.) I've done it, because it's an easy, fast, cheap way to make molds if you have a vacuum former... but I haven't done it for fiberglass boats. It should work fine if vacuum forming gives you the detail you want and you don't lay up the FG too thick and get the plastic too hot. For a model, I wouldn't expect that to be an issue. I'd probably go with HIPS (high-impact polystyrene) for the mold. It's cheaper than ABS, a little easier to form (but ABS isn't hard to form) and doesn't require pre-drying. (ABS does absorb moisture from the air and may require pre-drying, so that the moisture doesn't turn to steam and cause bubbling and other weirdness when you heat it for vacuum forming.) How big a boat are you talking about, and how thick a layup? Does the shape have any sharp details---edges, etc.---and are they convex or concave? (Vacuum forming captures smaller positive details than negative ones... it's hard to suck the plastic down into little grooves, etc.)
Posted on: 11/5/2007 11:13 PM by Author "drcrash" in the forum "Speed - Electric"
http://www.rcuniverse.com/forum/fb.asp?m=6586607

RE: making your own bodies
[quote]ORIGINAL: Drift Noob Dude, after all the stressing... wouldn't it just be worth it to buy one? I know that there would be great satisfaction at the end of the process, but the journey? Eek... [/quote] If what you want is for sale, especially if you just want one, it's usually cheaper to just buy one than to make one. But if you want something custom, vacuum forming is usually one of the less stressful ways to make it. You put most of your effort into sculpting the shape, and then you don't directly use it---you make a copy and use that. If it breaks, you can make another one in a few minutes. I lost interest in in scratchbuilding and custom model stuff 20 years ago, after smashing too many things I'd put too many hours into. I got interested again when I found out how easy molding and casting and vacuum forming are. Putting a few hours into making a good vacuum former was a better investment of my time and money. That's not to say it's always easy, depending on what you're trying to make. But for me, it is all about "all the stressing," and it cuts the other way.
Posted on: 9/28/2007 9:35 AM by Author "drcrash" in the forum "RC Painting, Detailing & Bodies"
http://www.rcuniverse.com/forum/fb.asp?m=6424121

RE: Vaccum bagging pump.
If you're looking for a "real" vacuum pump, the surplus Thomas rocking piston pumps (4.5 CFM, 115V, around 27 in. Hg) pumps Doug Walsh is selling at www.build-stuff.com are the best deal I know of. (Like Gast, Thomas is a major and respected brand of pumps.) Under $100 shipped.
Posted on: 9/26/2007 7:13 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=6417880

RE: quick question can you add fiberglass to plastic without melting plastic?
[quote]ORIGINAL: BB Modss want a better bond to plastic's? scuff the crap out of it, take a epoxy brush and lightly brush a very thin coat of acetone onto the plastic part then lay your glass on and start wetting it in! [/quote] Is the acetone just to etch the plastic, and it's okay if it dries before you put on the epoxy? Or is it to make the plastic gooey on the surface so that the epoxy will fuse with it? (In that case I'd think the amount of acetone & the timing would be pretty delicate---just a little acetone so you don't just melt the part, and put the epoxy on right away before it dries. Tricky to do, especially for a big part.) I'm wondering if some kind of primer might be better---easy to use and give a great bond.
Posted on: 9/22/2007 1:58 PM by Author "drcrash" in the forum "Speed - Electric"
http://www.rcuniverse.com/forum/fb.asp?m=6400333

RE: quick question can you add fiberglass to plastic without melting plastic?
My understanding is that polyester resin (like cheap "fiberglass resin" from the hardware or auto store) will eat styrene plastic, at least if the plastic is thin. Epoxy won't, but doesn't make a chemical bond. That's why you need to scuff it well---you're relying on a mechanical bond. I'm wondering if it would adhere better with an appropriate primer, which makes a good bond to styrene, and lets the epoxy make a better bond to it. Maybe just "plastic primer" or that "Plastic Fusion" paint? (I don't know how well epoxy sticks to them.) I've seen somebody somewhere using polyester resin on thick ABS (not for lightweight models) because it DOES eat (dissolve) the plastic a bit, and fuse with the resin make a stronger bond. (Or so they said.) I think urethanes generally stick better to styrene plastics than epoxy does, but I don't know how well epoxy sticks to them.
Posted on: 9/22/2007 8:03 AM by Author "drcrash" in the forum "Speed - Electric"
http://www.rcuniverse.com/forum/fb.asp?m=6399464

RE: Vacuum Forming - plug material?
I'd use whatever's easiest for you to sculpt and smooth to the shape you want. That's the hard, time-consuming part. If it's not rigid enough (like light foam or modeling clay), you can either cover it with something more rigid and heat resistant, or mold and cast it to make the actual vacuum forming buck (male mold). Lots of people sculpt pink or blue (XPS) insulation foam and coat it with epoxy. I like modeling clay molded with alginate and cast in plaster of some sort. (Usually water putty or Ultracal-30.) Plaster is usually fine for canopy and cowling shapes, if you're not making a ton of copies. (It tends to chip after a few pulls if you have sharp protrusions, but canopies and cowls usually don't have those.) If you need vent holes in concavities, you can mold them right in. (Put greased wires or skewers in the plaster, and pull them out when it's firm but not set hard.) To smooth a shape at a small (sub-millimeter) scale, you can vacuum form craft foam over it, then mold and cast that. Paul
Posted on: 9/18/2007 12:53 PM by Author "drcrash" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=6383697

RE: making your own bodies
Ooops... forgot which forum this was in... About recasting car bodies specifically, it's reasonable to make a heavy, tough "practice body" copy of a shape you've bought, and/or an especially light "racing body"... but just making a bunch of copies and giving them to your friends is punishable by heavy fines and up to n years of imprisonment. (Where n is a number I can't remember.)
Posted on: 9/9/2007 9:07 PM by Author "drcrash" in the forum "RC Painting, Detailing & Bodies"
http://www.rcuniverse.com/forum/fb.asp?m=6347615

RE: making your own bodies
[quote]ORIGINAL: calvin33 Think this will work with existing bodies or will the plastic be too hot? [/quote] Are you talking about vacuum forming directly over the existing body? If so, I'd be worried that the plastic might warp. But if you don't support it (fill it with clay or something), it will definitely get crushed. Even a vacuum cleaner can apply about three hundred pounds of force per square foot of surface. (A vacuum pump can apply up to a ton of force per square foot.) The usual thing is to cast plaster INSIDE the original piece of vacuum-formed plastic, using it as a mold, and vacuum form over the plaster cast. (You need to support the original with clay, or maybe in a sand box, or something, to keep it from distorting under the weight of the wet plaster. Wet plaster is heavy.) If the original was formed over a male mold in the usual way, you actually get better detail that way---the side of the plastic against the mold captures the shape of the mold better. The other side is a bit more smoothed and rounded, by the thickness of the plastic (and usually a bit more). This is a good idea for making "backup copies" of cowlings and other things that tend to get broken in crashes. When that happens, you can just pull another one over the plaster positive you saved. (Tip: make the plaster cast BEFORE you trim the flash off the original. The extra plastic around the edge helps keep it rigid during casting.) Don't do this just to make a bunch of copies of somebody's commercial shape though. (That's not cool or legal.) But if you want to transform an original you own into (say) thicker or tougher plastic, it can be "fair use". (In my opinion, but maybe not their lawyer's. But if you're not selling them, or giving them away, they probably wouldn't care.) The best application of this "recasting" is when you can buy a shape that's *close* to what you want, cast it, and modifiy the cast to make it *exactly* what you want. (Like adding scale details, or making it into a different version of the same make of plane, etc.)
Posted on: 9/9/2007 9:03 PM by Author "drcrash" in the forum "RC Painting, Detailing & Bodies"
http://www.rcuniverse.com/forum/fb.asp?m=6347592

RE: Vacuum Forming
[quote]ORIGINAL: Chad Veich Best place to purchase sheet plastic is directly from a supplier such as Curbell or Laird Plastics. Your local Yellow Pages or Dexonline is a good place to start. [/quote] Yes, the yellow pages are a good place to start. There are sheet plastics suppliers all over, supplying local glazers, signmakers, and people who make packaging or line shower stalls... and you don't have to pay shipping charges. Among other things, they usually stock thin styrene in several thicknesses between .020 and .125, to sell to signmakers who print on it, and it's reasonably priced because they sell mostly to businesses. Some plastics they can special order, and they usually won't charge you extra for that. Within a day or three, you can go pick it up. They're likely to have acrylics (like plexiglas) and polycarbonates (like lexan) too. You should call around and see which ones have a minimum order, and if so, how much the minimum is and whether they'll waive it for "will call" orders. (That you pick up in person.) Some places have a $100 minimum to keep people like us out. Others have a $15 or $25 minimum and are happy to sell a sheet or two of anything to anybody. The best prices are usually on 4 x 8 foot sheets. (For high-impact styrene, about $13 for .030" or $24 for .060", or about 40 to 75 cents per square foot and pretty much proportional to the amount of actual plastic.) For thicknesses like that, you can have them roll it up, and take the roll home in your car, and cut it into smaller sheets by scoring and snapping. They'll cut it down for you, but it's likely to cost a few dollars a cut. (Maybe not, if you tell them you want a "nominal cut," i.e., not a precision cut.) Thin HIpS and PETG are easy to cut for yourself, though, so I wouldn't bother them for that for a small order.
Posted on: 9/9/2007 6:37 PM by Author "drcrash" in the forum "RC Scale Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=6346993

RE: Vacuum form a clear canopy!
Anybody had any luck casting polyester (fiberglassing) resin and bondo? My understanding is that large solid casts of regular polyester resin can get VERY hot, and maybe even explode. It's not recommended for more than an eighth or a quarter of an inch thickness at a time... just mixing the stuff in large quantities is difficult, because you have to get it mixed before the heat from the exothermic reaction makes it all kick. Oops. I think a better way would be hollow casting the bondo/resin mix as thin shell, say 1/8", and filling in the middle with polyurethane foam. (2-part stuff, about 4-8 lbs/cu. ft. density. The spray can stuff is a pain and not any cheaper.) For the time being, though, I'll mostly stick to plaster... BTW, a good place to get plaster is a local ceramics supply place. You can get 50 lbs of #1 molding plaster (plaster of Paris, more or less) for about $18, and 50 lbs of Ultracal-30 (harder, good for casting) for about $23. Cheaper than at a home improvement store or craft store. For smallish stuff that you may want to work after molding, water putty from the hardware store is good. (But pricier per pound.) It doesn't set up hard and fast like Ultracal, and is stronger than plaster of Paris. You can work it a bit while it's still "green" (solid but not set hard), and after that you can sand and drill it, and spackle it with more water putty. (Fresh water putty sticks pretty well to old hard water putty.) You can also mix it 1:1 or 2:1 with plain plaster of Paris to get intermediate properties and price.
Posted on: 9/9/2007 1:38 PM by Author "drcrash" in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=6345985

RE: making your own cowl?
I'd vacuum form it. See Chad Veich's thread on "Basic Vacuum Forming" in the RC Scale Aircraft forum: http://www.rcuniverse.com/forum/m_81435/tm.htm and the "avoiding webbing" thread in the scratch building forum: http://www.rcuniverse.com/forum/m_5086453/tm.htm (A Corsair cowl sounds like a perfect candidate for the roll-of-masking-tape trick to avoid webbing on the steep sides.) My site shows how to make a really simple but good vacuum former in about an hour: www.VacuumFormerPlans.com To make the plug, I'd consider making a lathe-like setup with a block of foam on a spindle, so that it can rotate, and using a hot knife to cut the foam, or maybe a multispeed Dremel on low speed. (I made a hot knife out of a 100-watt pistol-style soldering iron, with a thin strip of stainless steel as a blade. You can shape the strip to get the profile you want, and rotate the foam on the pin to get a figure of revolution, and sand it smooth by rotating it by hand with a sanding block as the cutter. (If you have an orbital sander, that's easier... just rotate the plug slowly and let the sander do the work.) A regular hot wire cutter would probably work to get the cylindrical part, and then you could just sand the rounded front lathe-style. You'll want to surface the foam with epoxy or something, or maybe mold it in alginate and cast it in plaster. (Still easier than glassing, IMHO... see my web site for info on alginate & plaster casting.) Of course, if you can find something just the right size and shape, that's even easier. Just vacuum form over it, if it's strong enough, or make a plaster cast and use that.
Posted on: 9/9/2007 12:41 PM by Author "drcrash" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=6345790

RE: Vacuum Forming
[quote]ORIGINAL: BoiseBee You're getting fantastic suction to form over such a large mold. I noticed you have a "Shark". Powerful little bugger. I've been using a shop vac, but might try the shark. A lot easier to haul around. [/quote] My shark is a 1000-watt unit that they don't sell anymore, unfortunately. I think their highest now is 700 or 800 watts, but I don't know if that makes any difference. The "secret" about vacuum cleaners is that most good vacuum cleaners pull about equally hard. Some can pull air faster against very little resistance, but more powerful vacuum cleaners generally don't pull much harder when it counts. For example, if you look at the 9 Shop*Vac (TM) brand shop vacuums they sell at Lowe's, they all pull between 54 and 60 inches of water, sealed. (That is, they can all suck water five and a half to six feet up a hose if everything between the vacuum blower and the water is perfectly sealed.) That's the figure you want to know for vacuum forming. 60 inches of water is only 4.4 inches of mercury, or 2.1 PSI. That is not impressive, and there's not much difference between them---the weakest and cheapest only pulls 10 percent less hard than the strongest and most expensive, which is no better than the high-amp canister and hand vacuums I've gotten at Goodwill. You're just not going to notice that difference. (A factor of two makes a noticeable difference; 10 percent doesn't.) You're likely to see more difference by making sure the lid seals well to the bucket, caulking around the hose fittings, etc. The high-end Shop*Vac may pull 2x the air against no resistance that my Shark can, but it doesn't matter for anything that will fit in a kitchen oven---the plastic pulls down plenty fast, and any decent vacuum cleaner is perfectly fine in that respect. The horsepower ratings on shop vacuums are totally bogus and useless, as reflected in the vacuum level figures. (The "6.5 HP" Shop*Vac only pulls 10 percent harder than the "2.5 HP" one? Huh?) You can't really get 6.5 horsepower out of a 15-or 20-amp domestic circuit. A horsepower takes about 750 watts, and if you have more than 2 or 3 *real* horsepower, it's going to flip a circuit breaker every time you try to use it. (Thanks to Doug Walsh for pointing that out.) Household wiring can take a momentary surge of greater than 20 amps without flipping the breaker, but that does not happen with a vacuum cleaner when you need it for vacuum forming---when you really need a hard suck against high resistance, the impeller unloads because it's just not designed to maximize vacuum level; it's designed to maximize more-or-less open flow. (Lots of throw, but not much leverage.) If you could count on hose sizes being determined by engineering rather than marketing, vacuums with small hoses for their amp or watt ratings would be better---it would indicate that the machine was optimized for relatively high leverage and short throw, like a vacuum pump; unfortunately, I suspect it doesn't mean much at all. One thing that may make a difference is whether a vacuum cleaner is a canister or an upright, or one of those hand vacs that has a sweeper thing built in (for upholstery or whatever). My old 4-amp Dustbuster didn't suck very hard---it failed the craft foam test---and I suspect that was either because it was just wimpy or because the valve/louver thing that switches from the sweeper thing to the accessory hose mode didn't seal well. I also used to have an upright that was good for floors, but likewise didn't work that well through the hose, so I'd look for something that always sucks through the hose connection. (If that leaks, you can caulk around it with tacky putty or something.)
Posted on: 9/9/2007 11:53 AM by Author "drcrash" in the forum "RC Scale Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=6345628

RE: avoiding webbing (wrinkles) in vacuum forming
I came across a simple trick for forming rocket nosecones that should also apply to many difficult cowlings. (This is a simple version of what's called "plug assist" in industrial vacuum forming.) After stretching the plastic over the mold, with the vacuum OFF, use something with a round opening about the right size---such as a roll of masking tape, for a small cowling---to push the plastic straight down to the platen in a circle with the mold dead center. Then hit it with vacuum. That will create a steep-sided cone of plastic around the mold, so that it fits better, and is less likely to web when sucked in. It avoids the hassle of making a close-fitting frame, or figuring out how to hold a vignette in place while heating the plastic. A roll of masking tape may be all the extra equipment you need. (But you might need three or four hands---two to hold the frame down and one or two to lower the plug-assist thing as straight-down as you can.) Thanks to Doug Walsh for this one. (He's the author of Do It Yourself Vacuum Forming for the Hobbyist, but this one's not in the book.)
Posted on: 9/7/2007 10:07 AM by Author "drcrash" in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=6338354

RE: Vacuum Forming
I set up a new vacuum forming web site, www.VacuumFormerPlans.com Here's my recent "Instructable" (step-by-step how-to) on making a good cheap vacuum former: http://www.instructables.com/id/E8RW98YF3C4XLCQ/ Here's a video of it in operation with a kitchen oven & vacuum cleaner: http://www.youtube.com/watch?v=hGBRiYhxRTM My site has links to articles & threads on making a cheap standalone oven, avoiding webbing, making vacuum forming molds from sculpts by molding (with alginate) and casting (with plaster or water putty), etc.
Posted on: 9/6/2007 12:30 AM by Author "drcrash" in the forum "RC Scale Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=6332906

RE: making your own bodies
Here's a new Instructable on making a more capable vacuum former than the one in the earlier instructable: http://www.instructables.com/id/E8RW98YF3C4XLCQ/ It's cheap and very easy to make. Here's a movie of it in operation: http://www.youtube.com/watch?v=hGBRiYhxRTM Check out my new web site, www.VacuumFormerPlans.com, for more good stuff on vacuum forming. (And more to come.)
Posted on: 9/5/2007 9:16 PM by Author "drcrash" in the forum "RC Painting, Detailing & Bodies"
http://www.rcuniverse.com/forum/fb.asp?m=6332828

RE: Vaccum bagging pump.
A venturi vacuum generator will work if you have a compressor that can pump 4+ cubic feet per minute at 90 PSI. They only cost about US$15 at Harbor Freight. Unfortunately a lot of people have little compressors that can't do the duty. (The kind that can drive a brad nailer but not more air-intensive air tools.) They may be able to pump a few CFM, but not at 90 PSI. A venturi vacuum generator isn't an efficient way to use a compressor---you use a LOT of compression to get a much smaller volume of vacuum---but that's not much of an issue for most vacuum bagging. If you have a compressor that can pump enough air, it's a good cheap way to go. If not, you might consider converting your small compressor to a vacuum pump, which is much more efficient than driving a venturi.
Posted on: 8/8/2007 12:18 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=6212014

RE: Vacuum forming questions
[quote]ORIGINAL: Campy I am going to try my hand at vacuum forming. I have built a 10" x 12" x 3" box and a 750 watt hot plate in a reflective foil lined box for a heater and I have a 10 gallon shop vac for the suction (bag and filter removed for this). [/quote] I'm guessing that your "hot plate" is a single round burner thing. You may need to position a reflector over it to block the direct infrared to the plastic directly above it, and bounce the IR around to the sides and corners. Otherwise you're likely to have a serious hot spot in the middle. (And the ends of your rectangular plastic may not get hot enough before the middle gets too hot.) That's pretty much what I did for my two-burner-hot-plate-and-disposable-aluminum-pans oven: http://www.rcgroups.com/forums/showthread.php?t=621858 Also, a shop vac isn't especially appropriate for vacuum forming. (But it will probably work fine for canopies.) It's a myth that shop vacs pull harder than household vacs. (The strongest-pulling vacuum cleaners are canister vacuums with two-stage blowers.) Any high-amp (or high-wattage) vacuum cleaner is probably fine for thin plastic, including a $5 canister vacuum from Goodwill. (At any rate, the "gallons" aren't relevant. That's just the size of the bucket that the air gets sucked through, not the strength of the motor. Some wimpy shop vacs have big buckets, and some powerful ones have small buckets.)
Posted on: 7/23/2007 10:01 AM by Author "drcrash" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=6145196

RE: Vaccum bagging pump.
Doug Walsh has a great deal on unused surplus Thomas Wob-L (oilless rocking piston) pumps at www.build-stuff.com right now. Under $100 for a pump that would retail for three or four times that. I have two and they're great. (A bit overkill for most vacuum bagging, but for under $100, who cares?) They have high enough flow to work well for vacuum forming, and they can be used as compressors for airbrushing as well. If you can't go $100, you might consider the really low-ball approach of using a converted bike pump. You can buy an old-fashioned bike pump and a few parts for about $18 total, and convert it easily in about 20 minutes. Check it out: http://www.instructables.com/id/EA58LR1F35J1I9N/ Don't laugh at the idea of a manual vacuum pump for bagging. My bike pump can pull over 20-24 inches of Mercury, and can pump a gallon jug vacuum reservoir down to 20+ inches in less than a minute. (There's a popular kit from Roarockit for vacuum pressing skateboards and small woodworking stuff, using just a wine-bottle vacuum pump that's much slower.) You can also convert a 12V electric tire inflator-type air compressor to a light-duty vacuum pump. (Light duty, but plenty high vacuum.) I made one for a few dollars using an inflator I got from a Goodwill Outlet Store. http://www.instructables.com/id/E791HNXF23Z39P6/ A FoodSaver kitchen vacuum sealer can also make a good light duty vacuum pump. They generally pull 23+ inches of mercury. I used to use one for a small vacuum forming setup, before my wife confiscated it and started bagging food with it. A "nebulizer" pump should also work. They don't pull as high a vacuum (about 17 inches of mercury), but that's enough for most bagging of foam wings and stuff. You can get them cheap on eBay and even cheaper at Goodwill sometimes. (I've gotten three for $2 each at the Goodwill Outlet.) For these little electric pumps, you'll want to have a vacuum switch, and a pretty well-sealed bag. They'll likely burn out if you run them continuously for more than a few minutes.
Posted on: 7/23/2007 9:30 AM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=6145115

RE: Vacuum Form Materials
[quote]ORIGINAL: RCKen Hmmmmm, now that gets me thinking. What do you use to heat your material before putting it on the vacuum form???? Thanks in advance [/quote] I designed and built a bottom-heating oven using a two-burner hot plate and some disposable aluminum pans. http://www.rcgroups.com/forums/showthread.php?t=621858 It cost less than $30, took less than an hour to build, and works very well for thin plastics. (For thick plastics, it's nice to have a way to turn the heat down a little; the stove-type heat controls don't work very well.) A standalone oven is very convenient for a small vacuum former. You can put it behind the platen, and just lift the plastic up off it, pull it toward you, and bring it straight down over the platen.
Posted on: 6/20/2007 2:32 PM by Author "drcrash" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=6012346

RE: Vacuum Form Materials
The cheapest place to get sheet plastic is usually a local plastics supplier that has no minimum order, or one that will waive the minimum if you pick the plastic up in person. Call around. Some plastics suppliers have $100 minimums to keep riffraff like us away. Others have no minimums, or a $25 minimum, and are happy to sell you a sheet or two. (Unfortunately, you generally have to call and ask about minimums; it's not usually in their yellow pages listing or on their website.) A 4 x 8 sheet of thin plastic is generally cheap, say $15-25, because plastics suppliers price things mostly by the actual amount of plastic, and for a thin sheet, it's just not very much plastic. You can roll a thin sheet up and take it home, and cut it into the size(s) you want by scoring and snapping. Anywhere else, you're likely to be paying much more per sheet (of whatever size) than you're actually paying for plastic.
Posted on: 6/20/2007 2:11 PM by Author "drcrash" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=6012259

RE: Reservoir tank for Vacuum Pump?
[quote]ORIGINAL: Toomanyplanes I use a reservior system for all my bagging and I think its really the way to go if you can make one. I found a TORR portable vacuum pump at a local pawn shop here and snapped it up for $250. This pump new costs about $3000 from Torr. I found out when I got it home the pump had 2 bad bearings and seized after about 5 minutes so I pulled it off and disassembled the pump and removed both bearings. Replaced them for about $20 and viola! runs like a top. I even added a SECOND reservior (the portable air tank type) for about 30 gallons of volume. When I bag, the pump maybe runs once or twice in three hours for about 30 seconds. The only way to go. [/quote] If that's the only way to go, I suspect most of us will never get there. [X(] If your pump is only running for 30 seconds every hour or two, you've got an order of magnitude or two more suckage than you really need. (On the other hand, when you start bagging 1:1 scale planes, you'll be all set, and it sounds like you got a real deal.) For most modeling purposes, a very small pump and a small reservoir made from PVC pipe are fine. (The $20 7-gallon air carry tank from Wal-Mart is overkill, but hey, it's premade and cheap.) For a small intermittent-duty pump (like a converted tire inflator) you don't want a big tank, because a little one does the job nicely and you may overheat your pump just drawing the big one down. (The reservoir is supposed to let the pump run intermittently.) BTW, Doug Walsh has some surplus 4.5 CFM Thomas oilless piston pumps for sale over at www.build-stuff.com for under $100, shipped. Overkill for most model bagging, but at that price, worth considering. (And great for vacuum forming.)
Posted on: 6/15/2007 6:11 AM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=5990258

RE: converting a 12V tire inflator air compressor to a vacuum pump
[quote]ORIGINAL: soarrich Have you used this for any amount of time?[/quote] Not really. I've evacuated my 1-cubic foot (7 gallon) vacuum forming tank a number of times, but that's all so far. (I do know that some other people have used tire inflators this way and felt like they got their money's worth, but I don't have details on life expectancy.) [quote]20 years ago I had a leaky tire that I pumped up once a day, the pump gave out after about 2 months. [/quote] That doesn't really surprise me. These are cheap little pumps, and getting 60 uses out of a $20 pump doesn't actually seem that bad. My expectation would be that they'd be good for a comparable number of vac-baggings of RC wings or fuses, and not a bad deal at the price. (Especially if you find one for a few dollars as I did, and assuming you use a reservoir and don't run the pump continuously.) Somebody expecting to vacuum bag a project now and then at the hobbyist level might do well to convert one, especially if they're leery of investing in Real Gear until they've tried it, but somebody expecting to do hundreds of baggings should look for a "real" vacuum pump. (Or at least a heavier-duty compressor to convert.) Another option is a nebulizer pump. They only pull about 17 inches of mercury (or 8 PSI), but they are heavier-duty and better-made, quieter pumps, and you can find them in thrift stores sometimes for a small fraction of their original price. (I suspect you can also run them continuously without them simply burning up, but I haven't tried it yet and wouldn't want to wear them out uselessly.) Still another option is a Food Saver, either used roughly like it was designed to be, bagging and sealing a wing in a FoodSaver bag (like Jim Young does), or just using it as a cheap vacuum pump (as I do). (The good ones pull 23 inches of mercury, and they're not very loud.)
Posted on: 6/3/2007 8:12 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=5940278

RE: MODEL AS FORM for fiberglass!
If you want to copy a shape, one of the least dangerous ways to do it is with an aginate mold with a plaster mother mold. Alginate is usually used by dentists and lifecasters, because it's safe to put on skin, and releases easily. (Or even in people's mouths.) If your model can stand having something damp against it for 20 minutes, you can use alginate---usually with no release agent to mess up the detail. You must use the alginate mold right way, because it's water-based and starts to shrink as it dries. You can usually make 2 or 3 copies of something, no more, before it distorts. I usually cast water putty (from the hardware store) in it, to get a "plaster" cast that's harder and tougher than Plaster of Paris after it dries. (But kind of soft and workable for a while when it's fresh.) From that you can make a negative mold in rubber or resin, without risking damage to your original.
Posted on: 6/3/2007 3:16 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=5938985

converting a 12V tire inflator air compressor to a vacuum pump
I posted an "instructable" over on instructables.com, showing how to convert an inexpensive 12 volt tire inflator into a vacuum pump. Thought it might be useful for vac bagging small composites. I got my inflator for $2 at the Goodwill Blue Hanger store, and the parts and glue to convert it cost a very few dollars. http://www.instructables.com/id/E791HNXF23Z39P6/ The basic trick is just to open up the case, find the air intake on top of the the pump cylinder, and glue a hose barb over it with J.B. Weld. For my pump, that's the four little holes in the top of the pump cylinder here: [IMG]http://i136.photobucket.com/albums/q176/drcrashpix/miscvacuumforming/tireinflator2vacuumpump/ti2vp010.jpg[/IMG] And here's the "after" picture: [IMG]http://i136.photobucket.com/albums/q176/drcrashpix/miscvacuumforming/tireinflator2vacuumpump/ti2vp018.jpg[/IMG] Then you put a hose over the barb, cut a hole in the case to route it out, and put it all back together: [IMG]http://i136.photobucket.com/albums/q176/drcrashpix/miscvacuumforming/tireinflator2vacuumpump/ti2vp024.jpg[/IMG] Comments & questions very welcome. (Here, or over at instructables.)
Posted on: 6/3/2007 3:07 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=5938965

RE: Reservoir tank for Vacuum Pump?
[quote]ORIGINAL: rxAxilleas i read the thread but didn t understand where you will use this kind of compressor item. can anyone explain? [/quote] For the two-stage vacuum setup for vacuum forming, I can plug it in as the "high vacuum pump" instead of the FoodSaver. (My wife decided she wanted one for, of all things, vacuum-sealing food. Go figure.) Here's the basic, simplified plumbing for a one-stage vacuum system. This would work fine with a small vacuum pump, small tank, and small vacuum former: [code] + - - - - - - - - - - + | platen | +--------+ +---------+ | | | | +-------------+ | | +-------+ | | | +--------+ ball +----------------------+ vacuum | +-----------+ valve +---+ +----------------+ tank | +-------+ | | | | | | | | | | | | | | | | | | | | | | | | +--+ +--+ | | | high | | | | vac | | | | pump | | | +--+ +--+ +-------------+ | | exhaust [/code] You close the ball valve and turn the pump on to evacuate the tank. Then when you're ready to form, you pull the plastic down over a mold on the platen and open the ball valve. Air rushes from around the mold, through the platen hole(s), and through the pipe into the tank. The reason for the tank is that a little cheap low-volume (but high-vacuum) pump can't pull the air out fast enough by itself. You want to pull the air out from under the plastic within about a second, before it cools much. Using a tank lets you store up a bunch of vacuum and use it all in a hurry, just by opening a pipe into the tank. The tank can pull air about 100 times faster than the pump alone, but only until the tank fills up. This works well for vacuum forming, because it generally takes you a few minutes between pulls anyway. (Clamping & heating the plastic, removing it afterwards, etc.) The pump can be pulling air out of the tank while you're doing that stuff, and then you can use the vacuum it's built up in a few seconds during forming. The same basic scheme works for vacuum bagging, with a vacuum bag instead of a platen. (And usually with an even smaller tank, usually called a "reservoir," with a capacity of roughly a gallon.) The function of the tank there is also to store up vacuum---not because you'll be using a whole lot of it in a big hurry, but so that you don't have to run the pump continuously to keep up with small leakage and outgassing from your resin. The tank acts like a flywheel for vacuum, by making the space that the pump is pulling from much larger. A little leakage or outgassing into that much larger space will only slowly degrade the vacuum. If the vacuum drops too low, you can turn the pump back on again to pull most of the leaked air & fumes out of the tank, then shut the pump off again. In between, the reservoir sucks up most of the gases. (You can do that automatically with a vacuum switch, or by hand.) You need that intermittent pump operation if you use a tire inflator as a vacuum pump, because they're not meant to run continuously for long periods of time. They may overheat and seize up, or strip their heat-softened nylon gears, if you run them for more than 10-30 minutes. (Depending on the pump. Some of the incredibly cheap tiny ones can only run for a few minutes at a time, but bigger and better ones can run for up to an hour or more.) Some vacuum pumps can run continuously, so you can simplify the setup, but they won't last as long as if you run them intermittently.
Posted on: 6/3/2007 2:16 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=5938653

RE: Scratch Building Question regarding Canopies / Windshields
[quote]ORIGINAL: shotgun06 Where can you find alginate? [/quote] You can find it lots of places online---any number of molding & casting or special effects supply places. My wife and I use Algiform Slow-Set from Pink House (www.pinkhouse.com). I don't know if it's any better or worse than the other brands (Alja-Safe, Mold-Gel, etc.); it's reasonably priced and has worked well for us, so we've stuck with it. Here's an example (non-RC, and maybe cute overload, sorry, but you can see my sliced pink foam in one of the pictures :) ): http://www.tk560.com/phpBB2/viewtopic.php?t=635 That's an overview of my wife making masks for a friend, using alginate first for lifecasting, then for casting a buck (male mold) from a clay sculpt. (The clay sculpt being built up on the plaster life cast.) She vacuum formed 2mm & 3mm EVA foam (craft foam) over that. Several basic techniques are demonstrated there, including: (1) using alginate with a plaster mother mold, and gauze as a binder layer between them, (2) casting a buck with molded-in vent holes using greased skewers ([i]much[/i] easier than drilling them later), (3) working the "green" (not very hard) water putty buck a little after casting it, and (4) vacuum forming foam on a simple cheap setup with a one-hole platen (with windowscreen under the buck). You can also see the smoothing effect of vacuum forming thick stuff over a mold, which can be useful as an intermediate step to make a smoother mold. It takes a few dollars worth of alginate to do something the size of a face, which costs a bit less than the water putty we usually cast in it. (You can mix water putty with plain Plaster of Paris to get intermediate price and performance.)
Posted on: 6/1/2007 1:03 PM by Author "drcrash" in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=5930576

RE: Scratch Building Question regarding Canopies / Windshields
[quote]ORIGINAL: shotgun06 Just my little bit of advice. I did a custom canopy for my Heinkel He-162. [/quote] Nice work. [quote] The plug ( you can see it on the bottom right hand of the picture ) was made of insulation pink foam covered with bondo and finished with auto primer, nothing fancy yet...My vacuum box is the shoebox with a lot of masking tape you can see under the plane ( not getting fancier...), I used the house built-in vacuum system and I have been using the toaster oven you can see in the background to heat the plastic. My point is, if you intend like me to do it once for fun, there is easy ways to do it at almost no cost to you and it is good learning experience. [/quote] Yes, a VERY simple and VERY cheap vacuum former can work just fine for most common RC purposes. (Small objects made of fairly thin plastic, without extremely fine detail.) You don't even need a box---a board with one big hole in it to connect the vacuum works just as well, and maybe better, if you're only making one thing at a time. (Many industrial vacuum formers have one-hole platens.) You don't even need a gasket around the edge, if you're only using one size of plastic. You can pull the plastic down around the edge of the board so that it seals directly to the edge, and that works better than the frame against a gasket. (The edge should be slightly rounded and very smooth.) Heating things in a kitchen oven works fine, too. (Or if your oven doesn't heat evenly, you can fix it.) You don't need a shop vac. A good household vac or even a high-amp hand vac works just as well. (Shop vacs can pull a lot of air in a hurry, against low resistance, but for smallish stuff it doesn't matter. What matters is how hard a final vacuum you can pull. My Shark hand vac outpulls my 5.5 HP shop vac, and works great for my 12" x 20" former; it cost me about $5 at Goodwill.) If you want to get fancy, you can make a good standalone vacuum forming oven for $30 in less than an hour, and a high-vacuum pump for another $30 in 20 minutes. (I've used those to form 1/4" thick hard plastic, to make (non-flying) parts I can stand on without breaking them, and to form 3/8" EVA foam.) So... you can make a plenty good vacuum former for $30 in an hour, and a rocking vacuum former for $100 in a very few hours... but the $100 one is way overkill for typical canopies and cowlings. (It'd be nice for polycarbonate car bodies, though.) But about fiberglass over foam for plugs... one gotcha. If you use Bondo (polyester resin body filler) or polyester resin fiberglass over foam, you need to seal the foam first, with something like epoxy. Uncured polyester eats foam. You can also make plugs out of water putty, which is a kind of plaster that's tougher than Plaster of Paris. (Available at your local hardware store, for repair purposes.) It works fine if you're not making a whole lot of parts and don't need the durability of fiberglass or Bondo. If you have a delicate sculpted plug, you can make a sturdy enough copy of it for short-run vacuum forming by making an alginate mold and casting water putty in it. That lets you sculpt your plug out of anything you want, such as modeling clay. Alginate picks up incredible detail, like silicone moldmaking rubber, but much cheaper. (The downside is that you have to use it right away, because it's water based and starts shrinking as it dries. You can cast one or two copies in it, or maybe three if you work fast, and that's about it.) Alginate is mostly used by life casters, because it's safe to put on people's skin, but it's very handy stuff for one- or two-off moldmaking. It doesn't stick to anything, not even itself, and it's safe to put on just about anything that can handle being damp for a little while. That makes it very good for making backup copies of shapes, or intermediate casts for modifying and combining shapes.
Posted on: 5/31/2007 10:13 PM by Author "drcrash" in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=5928457

RE: Reservoir tank for Vacuum Pump?
[quote]ORIGINAL: TeamSeacats [quote]ORIGINAL: drcrash Another thing you could try would be to put a container INSIDE the vacuum bag with the wing, maybe a mason jar or heavy glass jug with a hole in the lid, and something porous over the hole so it can't get blocked. When you evacuate the bag, you'll evacuate the jar or jug as well. This will greatly increase the volume of vacuum
Posted on: 5/29/2007 10:51 PM by Author "drcrash" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=5919155

RE: VACUUM FORMING IDEAS
[quote]ORIGINAL: OzMo JB weld works well as a coating over wood and solid for smaller parts. sets smooth and is very sandable and shapeable before it completely cures. i have used this in commercial production of vacuum formed polystyrene and it holds up to multiple production runs well. [/quote] Interesting. I'd thought about that, but never tried it. J.B. Weld is a metal-filled high-temperature epoxy---pretty much the same thing professional tool and die guys often make short-run "tools" (molds) from. (Where a "short" run is usually hundreds or maybe thousands of parts.) I wasn't sure about the consistency and workability of J.B. Weld, but now I'll have to try it. Thanks for the tip.
Posted on: 5/29/2007 10:23 AM by Author "drcrash" in the forum "Tips & Techniques"
http://www.rcuniverse.com/forum/fb.asp?m=5916045