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Fiberglass tube
If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet
long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! |
Fiberglass tube
On Wed, 9 Jan 2008 20:32:49 -0500, "Garland Gray II"
wrote: If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! No personal experience. Here's an unqualified opinion: epoxy bonds to PVC. PVC pipe is a little wavy. Taken together, I think this means removing the glass from the plug would be tough. Saran wrap is one avenue to reliable release I hear - or maybe a good release agent - or aluminum foil I have heard suggested..... Brian Whatcott Altus OK |
Fiberglass tube
On Wed, 09 Jan 2008 20:15:15 -0600, Brian Whatcott
wrote: Saran wrap is one avenue to reliable release I hear - or maybe a good release agent - or aluminum foil I have heard suggested..... Johnson's paste wax will work. Ask the gunsmiths about that. In general, if there are the kind of pockets that would lock them together, fill them in with oil base modeling clay. This is no help with slight, just enough to cause trouble, waviness. As for pipe for a mold, there is no taper, which is the usual practice with molds in general. Sand castings are always tapered slightly. Casady |
Fiberglass tube
Right, I was concerned about the lack of taper. I hadn't looked real
closely at the surface of pvc pipe; I would sand it smooth if it looked irregular, and then wax. How do gunsmiths use pastewax, to protect and lube parts ? "Richard Casady" wrote in message ... On Wed, 09 Jan 2008 20:15:15 -0600, Brian Whatcott wrote: Saran wrap is one avenue to reliable release I hear - or maybe a good release agent - or aluminum foil I have heard suggested..... Johnson's paste wax will work. Ask the gunsmiths about that. In general, if there are the kind of pockets that would lock them together, fill them in with oil base modeling clay. This is no help with slight, just enough to cause trouble, waviness. As for pipe for a mold, there is no taper, which is the usual practice with molds in general. Sand castings are always tapered slightly. Casady |
Fiberglass tube
"Garland Gray II" wrote: .. If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? NO. Or would I need to first wrap the pipe with sheet plastic or similar ? Depends. Easiest solution is to glass pvc tube and leave it in place. It what I did to make a shaft tube. Next approach was using an 8" PVC pipe for a mold to fabricate a bow thruster tube.. First you slit the PVC pipe on one side using a table saw. Then you plug the ends of the slit tube with wooden plugs. Next, cover slit pipe completely with clear contact paper. Support tube on each end. Next, using light weight glass, say 17 OZ, double bias, wrap tube in a continuous wrap until yo get req'd layers. When cured, cut off plugs and break PVC pipe in pieces to remove. Doubtful you can do this on a small pipe such as 2-1/2". If you must remove PVC tube, the cover it with contact paper and wrap 2-3 layers of glass. When cured, slit both glass and PVC tube with a saw, the spring lamination open to remove PVC tube. Repair cut in glass, then use a mold to finish layup. I've done all of them. Have fun. Lew |
Fiberglass tube
"Garland Gray II" wrote in message ... If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! Interestingly I've done pretty much exactly this recently. I think the plastic sheet is essential and you need few wraps. One suggestion on another forum was to put several long thicker strips of plastic under the wrap ....protruding from the end so they could be pulled out and give a little room for the wrapped plastic to slide and twist as you remove the glass tube. Peter HK |
Fiberglass tube
"Garland Gray II" wrote in message
... If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! It will release but only with great difficulty. The GRP part will shrink as it cures and that will make the release VERY difficult even though the GRP is not stuck to the mould. What we normally do is engineer some flanges into the layup such that we have something to pull against because we will be exerting great amounts of force with clamps, presses, wedges, compressed air etc. The part needs to be able to witstand these forces and you need some way and place to apply these forces. The flanges or metal chains laid into the part can later be cut off. Likewise, you may need to engineer some sort of bearing piece in your PVC pipe. Or maybe use a 6' long theaded rod with nuts to apply force like a bearing puller. Still, the part needs to be strong enough to not buckle. Instead of wrapping with plastic sheet, we frequently use clear packing tape in 2" widths as a mould release. You tape up the part with clear tape, then wax then lay up. Do not use masking tape - sometimes the wax on the masking tape inhibits full cure of the poly resin. The easist way would be to buy polystyrene foam rods of the correct diameter from a craft store. Tape up and lay up. Melt out the foam with acetone or lacquer thinner when cured and pull out the clear tape. This is the most stress free way. Only problem is that the foam rod may deform (bend) during curing. Same as with PVC tubes. .... I just re-read that you will be using epoxy. In that case, with foam rods, don't even bother with a release agent or tape since epoxy resin will not dissolve your foam. And if you are using a low shrink epoxy, you will not get much deformation if at all. Or do what Peter hk said. That'll work. Here's a tip - we've all been taught to "wax on, wax off". I do it different - "wax on, wax on, wax on" let the wax harden up and do not wipe off. Layup over that. The part comes up with alot of wax transfer and swirls marks but those are easy to polish out. I do this even when making production molds because I refuse to risk a stuck plug and mold. Arnold sg |
Fiberglass tube
On Wed, 9 Jan 2008 22:17:23 -0500, "Garland Gray II"
wrote: How do gunsmiths use pastewax, to protect and lube parts ? That and release agent. They coat that part of the metal of a rifle that touches the wood with wax. Then when epoxy and glass powder are used for a perfect fit, you can get the action out of the stock after the epoxy sets up. This is called glass bedding the action. The perfect fit is good for accuracy, usually. It also seals the wood against changes in moisture content, and the attendant warping. This is, of course, in addition to ordinary, usual, use to protect both wood and metal from, for example, rain. Guys do hunt in the rain, nutty though that may sound Casady |
Fiberglass tube
Richard Casady wrote:
On Wed, 9 Jan 2008 22:17:23 -0500, "Garland Gray II" wrote: How do gunsmiths use pastewax, to protect and lube parts ? That and release agent. They coat that part of the metal of a rifle that touches the wood with wax. Then when epoxy and glass powder are used for a perfect fit, you can get the action out of the stock after the epoxy sets up. This is called glass bedding the action. The perfect fit is good for accuracy, usually. It also seals the wood against changes in moisture content, and the attendant warping. This is, of course, in addition to ordinary, usual, use to protect both wood and metal from, for example, rain. Guys do hunt in the rain, nutty though that may sound Casady Without the typical 7 degrees of draft (taper) you'll never get it off... I know because I've tried exactly that. Richard |
Fiberglass tube
You've had many good suggestions for dealing with the shrinkage of the
glass-epoxy laminate. Here's one more. With a tablesaw, cut one lengthwise slit in the pipe and cover the slit with packing tape. Wax the pipe thoroughly and do your layup. Bond a couple of blocks or other attachment points to one end the part. Twisting the pipe vs. the part should break the bond between the pipe and the part. Drill the other end of the pipe for some attachment and pull the part from the pipe with a come-along. "Garland Gray II" wrote in message ... If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! |
Fiberglass tube
Ok, Garland,
BTDT..... If you are going to do this, do not wrap anything around the pipe, without some other plan. The wrapping will ball up when you try to pull the two apart. I have not tried the PeterHK plan, but I'm not sure how well the 6' strips will pull out. I even tried a teflon family sheeting in one try and it was still tough. That one had a stainless mandrel because the mandrel would later be the rudder shank. Cut the mandrel pipe too long so you can hold it. Make the layup too long and fabricate some feature at the end to allow good purchase. Shrinkage is epoxy specific, talk you the manufacturer about both that and the best mold release. This is not going to be easy. If you can create a mandrel that can be unloaded, that will be a great advantage. I have never figured out how to do this without a surface artifact that leaves an internal longitudinal ridge in the layup. Good Luck Guy Matt Colie Garland Gray II wrote: If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! |
Fiberglass tube
On Thu, 10 Jan 2008 01:35:20 -0600, cavelamb himself
wrote: Richard Casady wrote: They coat that part of the metal of a rifle that touches the wood with wax. Then when epoxy and glass powder are used for a perfect fit, .... Casady Without the typical 7 degrees of draft (taper) you'll never get it off... I know because I've tried exactly that. Richard You perhaps tried a complete collar of glass. The usual forehand bedding is for the lower half of the barrel. This can be pulled free, as far as I know. Brian W |
Fiberglass tube
On Thu, 10 Jan 2008 10:59:46 -0500, "Conlin"
wrote: You've had many good suggestions for dealing with the shrinkage of the glass-epoxy laminate. Here's one more. With a tablesaw, cut one lengthwise slit in the pipe and cover the slit with ... tape. Make that a long straight diagonal (shallow taper) cut, and success is pretty certain, I'd think.... Brian Whatcott Altus OK |
Fiberglass tube
I can't see what benefit there would be to the slit being diagonal or
tapered and it'd be a tricky cut to make. The important thing is that the pipe be able to contract a bit after the laminate has cured. A couple of other possibilities: Coat the pipe with a thin (maybe .020") coating of paraffin wax and melt the paraffin out after the laminate's cured. If using a core of styrofoam (with packing tape finish), the core can be mechanically destroyed after the cure. "Brian Whatcott" wrote in message ... On Thu, 10 Jan 2008 10:59:46 -0500, "Conlin" wrote: You've had many good suggestions for dealing with the shrinkage of the glass-epoxy laminate. Here's one more. With a tablesaw, cut one lengthwise slit in the pipe and cover the slit with ... tape. Make that a long straight diagonal (shallow taper) cut, and success is pretty certain, I'd think.... Brian Whatcott Altus OK |
Fiberglass tube
I want to thank everyone who has given me all this good advice. I suspected
it might be a problem, so I thought I'd ask. You have saved me a lot of frustration. Thanks again. |
Fiberglass tube
On Jan 10, 7:50 pm, "Garland Gray II" wrote:
I want to thank everyone who has given me all this good advice. I suspected it might be a problem, so I thought I'd ask. You have saved me a lot of frustration. Thanks again. OK, I HAVE done this. I took some newspaper and wrapped it round a 2" piece of pipe roughly 2' long. Next wrap that with wax paper which is your release layer, apply the epoxied glass. It came off with no problem, in fact, I did it twice. I used this method to make the mast step insert for my MiniCup sailboats. |
Fiberglass tube
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Fiberglass tube
On Wed, 9 Jan 2008 20:32:49 -0500, "Garland Gray II"
wrote: If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! I don;t believe that you could get the glass off the PVC. I have made fiberglass tubing by molding two halves inside PVC pipe split lengthwise and using several coats of mold release it still took significant prying to get the halves out of the molds. Bruce-in-Bangkok (Note:remove underscores from address for reply) |
Fiberglass tube
On Jan 11, 3:24 am, Bruce in Bangkok wrote:
On Wed, 9 Jan 2008 20:32:49 -0500, "Garland Gray II" wrote: If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! I don;t believe that you could get the glass off the PVC. I have made fiberglass tubing by molding two halves inside PVC pipe split lengthwise and using several coats of mold release it still took significant prying to get the halves out of the molds. Bruce-in-Bangkok (Note:remove underscores from address for reply) Wrap several layers of waxed paper instead of the newspaper. It never occurred to me that it might NOT work. Shrug. |
Fiberglass tube
On Jan 9, 9:32 pm, "Garland Gray II" wrote:
If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! After the goo sets up, running a source of heat inside the pvc could soften it enough to pull out, or even to melt it out. Epoxy wouldn't be bothered by the heat required, I suspect. Alternatively, perhaps a plug of wax wrapped in a seperator would more easily be melted out. It's called the "lost wax" process. Or, a spiral coiled cardboard tube could be pulled out after set up. When I relined my rudder tube, I used epoxy with graphite shaped with a pvc pipe pulled out before setup and sanded inside after set up using a balloon and sand paper. I was worried that I might need to cut a tooth in the rudder post and use it as a tool to bore out the hole, or to use a hole saw and guide setup. I am told the "proper" way was to install top and bottom rudder bearings, but that would have cost quite a bit. Seems to have worked out, no more jamming or juddering under moderate loads. Terry K |
Fiberglass tube
One solution that I have tried on a smaller scale. Slit the PVC pipe down
one side on a table saw. The pipe should close up a little so the kerf will be a little less than 1/8". Cut a strip of 3/16 or maybe 1/4" polyethylene sheet maybe 1/2" wide and fit it in the kerf so that the edge is flush with the pipe's outer diameter. That will expand the pipe over it's normal diameter. Wax everything and spray on a couple of coats of PVA mold release. Mist coat first then a fill coat. Wrap your glass. If it is uni-directional, diagonally in both directions then straight once or twice then a top ply of woven on the bias. If you are vacuum bagging you have to pull all the diagonal and bias plies TIGHT and tape them well or the fiber will bunch up as the bag pulls it down. Once it is set up, knock out the poly strip out of the kerf and whack the outside of the tube lightly to break the release agent and let some air in. The pipe will spring back to its original diameter and drop out. If it still sticks soak it in water to dissolve the PVA. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Garland Gray II" wrote in message ... If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! |
Fiberglass tube
One other hint for wrapping a tube with uni-directional on an angle.
Multiply the OD of the tube by 3.14 to get the circumference and then by the sign of the angle you want. For example for your 2.5" tube, the circumference is 7.85". The sign of 45 degrees is .707 so cut strips of uni about 5.5" wide. If you keep the edge of each turn next to the previous one you will have a 45 degree angle. Again, pull it very tight if you are vacuum bagging. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Glenn Ashmore" wrote in message ... One solution that I have tried on a smaller scale. Slit the PVC pipe down one side on a table saw. The pipe should close up a little so the kerf will be a little less than 1/8". Cut a strip of 3/16 or maybe 1/4" polyethylene sheet maybe 1/2" wide and fit it in the kerf so that the edge is flush with the pipe's outer diameter. That will expand the pipe over it's normal diameter. Wax everything and spray on a couple of coats of PVA mold release. Mist coat first then a fill coat. Wrap your glass. If it is uni-directional, diagonally in both directions then straight once or twice then a top ply of woven on the bias. If you are vacuum bagging you have to pull all the diagonal and bias plies TIGHT and tape them well or the fiber will bunch up as the bag pulls it down. Once it is set up, knock out the poly strip out of the kerf and whack the outside of the tube lightly to break the release agent and let some air in. The pipe will spring back to its original diameter and drop out. If it still sticks soak it in water to dissolve the PVA. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Garland Gray II" wrote in message ... If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6 feet long, and then lay up several layers of fiberglass and epoxy, would the resulting tube slide off the pvc easily enough after curing ? Or would I need to first wrap the pipe with sheet plastic or similar ? Thanks ! |
Fiberglass tube
"Terry K" wrote in message ... SNIP and sanded inside after set up using a balloon and sand paper. Terry K That's a great idea! They are gonna laugh me out of the shop! Arnold |
Fiberglass tube
Alex wrote:
What about making the core out of Styrofoam plastic, wrapped in release or heavily waxed, and after the expoxy sets up dissolving the Styrofoam with gasoline, acetone, MEK or some other solvent that attacks the foam but won't hurt the epoxy? A possible advantage of this approach is that it allows the production of shaped epoxy parts that are more complex than a simple tube, should that be needed. Epoxy is fairly resistant to gasoline and many other common solvents, but it certainly would make sense to "insulate" it from the solvent with the release sheeting, heavy wax, etc., and then to thoroughly clean it after the core is removed. I've done this one several times. It works quirw well. Downside - the inside surface is goinf to be pretty rough - resin seeping into the crevices in the foam. If that is not a problem (and in this case it's probably not) this is probably a reasonable approach. But if I had to make this part? I'd use a paper tube for the core mold. Just make sure it's not waxed paper... Richard |
Fiberglass tube
There was an article in Good Old Boat where the guy built a water lift
muffler. To do what you are asking, the guy wrapped one layer of glass and epoxy around a well-waxed pipe. After it cured, he slit the glass and removed it from the pipe. A little epoxy and he glued it back together again and continued with the lay-up. Article 3367 May/June 2007. Pages 33 - 36. |
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