In the CLC website instructions on using peel-ply they say that it cannot be used on curved surfaces. I think they are talking about compound curves here. It seems to me that it would work OK on a simple curve, e.g., the outboard bracket demonstration on the same website.
Anyone who has used this stuff, please let me know for sure before I order.
Thanks. I should have been more specific re the outboard bracket. John Harris demonstrates building one for the Pocketship.
Are you saying "nylon sport fabric" or rip-stop nylon is the same or will work the same as peel-ply?
Yes, those fabrics work the same and are almost the same as commercial peel ply. The stuff from the fabric store doesn't have a coating like some pp's, and the texture won't be as perfectly tuned as pp, but unless you're doing this for a living or needing critical secondary bonds without sanding, it won't matter.
But for that outboard bracket, I'd buy some clear mylar (art store for sheets, or McMaster-Carr for rolls) and use that for a much better surface finish, and a much more sure release. (or coat the mold in slightly overlapped layers of packing tape, and sand away the ridges during the paint process)
And while we're improving things...
Make the mold "male" instead of "female", out of 3/4" or thicker material, and round over any outside corners but don't bother to fillet any of the inside corners, and don't bother to coat the wood (or mdf or particle board or whatever is laying around and pretty smooth).
Make some cauls (flat slabs of wood) that fit the sides and top of the mold. The side cauls will have one corner radiused where it presses into the flange part of the bracket. None of these parts need to be coated, filleted, or waxed, so this goes together quickly and easily.
Lay a sheet of mylar over the male mold and trim it so it overhangs by an inch all around. Cut another to match, and then several sheets of glass to get the thickness you want (figure .0018 inches per oz of fiber for hand layup, and closer to .0014 if the part will be pressed, as here. So for 1/4" of glass, use 178 oz of fiber thickness (this is about the same as the 28 layers of 6 oz that the author recomended)).
But go buy a yard or two of DB1700 (17 oz biax) and save yourself the pain of all those little layers! Wet out the layers individually on a plastic sheet, using a squeegie to first wet and then remove excess resin, adding the first layer to the mylar (flat on the bench) and each layer on top of that, add the second sheet of mylar, then transfer the whole sandwich to the mold. Clamp the caul to the top (what will be the motor surface) with at least four c- or f-clamps, grab the outer layer of mylar and fold/bend the sandwich down around the mold, press the two side cauls against the outer sides, a little above their final location, lightly clamp them across the mold, then use some longer clamps to pull the cauls down toward the flanges which will stretch the mylar over the outside corners (which are fileted in the author's example), then increase pressure/add additional clamps across the cauls. You should see a fairly significant amount of resin starting to ooze out between the mold and the cauls, so anticiapting this you could wrap your clamps with tape and place some plastic under the work zone...
You can slip a wood chunk in the glass sandwich if you like, or just add an external piece that can be replaced as wear occurs.
You'll use probably 1/3 the resin the author did, your part will be very smooth on both sides (you still need to trim the edges to shape and sand those), and the part will weigh about 1/2 - 2/3's what the author's did. It'll also be stiffer for having used uncrimped glass (the biax, versus woven).
And you'll have some simple pressure-mold making experience that you can apply to a thousand other little boat projects!
I don't know about your outboard bracket shape, but:
Peel ply won't conform as well as thin glass, correct. For kayak hull type shapes, you might need to cut darts in the sides, or cut the pp into 18" stripes across the hull, with slight overlaps. It will go over the corners (chines) just fine if they're modestly rounded.
It's perfectly acceptable to piece the pp together, in whatever patchwork pattern makes sense to get things covered. Just avoid the factory edges on any of the inner layers where there are overlaps- they're lumpier than a cut edge.
For small projects, a local fabric store is a good source. Look for "nylon sport fabric", or ripstop nylon, prefereably white, and expect to pay $4-6/yd. For larger progects, a composites shop will charge $3-4/yd and the stuff will be rolled instead of creased/folded, but you'll pay for shipping.
Good luck.
That's a great plan! Thanks! Nemochad, can you advise on one point?
I need to make something of similar shape, so can follow your directions completely. However I do not believe it will need to be quite so stout, so was aiming for maybe 3/16 thick, and planned on using DB 1200.
The question is, will a 1/4 inch radius on the male plug be too tight for this cloth? I could increase the radius, but would rather not.
Again, thanks for the inspiration.
Would someone mind comparing peel ply to use of wax paper?
Others may elaborate, but peel ply is porus cloth through which the excess resin passes and is sopped up with rags or paper towels.
I've never used waxed paper, but have used sheet plastic (polyethelene?) With this, the excess resin needs to be squeezed out the edges of the plastic.
Obviously, peel ply is more expensive. But it does have more give, but still not much.
Now I am really confused: I thought peel-ply was the exact opposite. A tightly woven synthetic fabric that was impervious to resin. One just laid it over wetted cloth and it created a smooth surface where it rested on the wet epoxy. After cure it was able to be pulled off and reused since the epoxy had not penetrated the cloth and thus had not bonded to it. I never heard of anyone mopping or wiping up epoxy with rags......
I was planning on trying it out on my next project, but perhaps I have the wrong process in mind?
1/4" id is perfectly doable, IF you can pull the Mylar or pp covering tight over the od as you clamp the cauls.
pp is porous, and is not reusable. If clamping with vacuum or cauls, backing the pp with a layer of t-shirt cloth or thin polyester batting ("breather fabric" or "absorber cloth") is a great way to actively pull excess resin from your laminate stack.
Avoid waxed paper like the plague when working with glass and epoxy. It's just asking for trouble to introduce such a contaminant into your workflow. Mylar, or ordinary plastic sheeting works just as well as a release, without the risk of wax transfer.
For instance, here's a similar part on a simple male mold. The stack from the mold out is mylar (release), breather, pp, 1/8" or so of carbon, then mylar (for a gloss outer surface), then clamping cauls matched to the mold's shape.
There has been an insidious misuse of terminology rampant on the web. It's even worse than calling the process of bonding wood with epoxy "welding". The miscreant is "poor man's peel ply" and it is used to refer to polyethylene sheets, usually sold in DYI hardware stores for use as dropcloths.
There is absolutely nothing wrong with the stuff and I have used it quite successfully myself, but as Nemochad and Garland point out, it's the complete opposite of peel ply.
That term, poor man's peel ply, is probably where your confusion came from, Chester.
And Nemochad, all I get is a sign-in page, no mast bracket photo.
Laszlo
And another...
Finished part:
Oooooh! Pretty!
How'd you keep out the pet hairs? I notice a pet door there.
Laszlo
I would bet most of us are thinking of the use of PP not as a tool during a molding process, that is for the 1% of people that have that talent, I bet...wouldnt you agree that most people use PP as a smoothing agent to reduce sanding on flat surfaces on coats of wet epoxy, which can also be done (no doubt not as well) with 4 mil poly plastic ("visqueen") or wax paper...thus I understand the term "poor mans PP".
So with that clarification, can anyone compare the use of PP and plastic and wax paper as a product to smooth out on wet epoxy, reducing the time spent sanding?
For that purpose, pp will work better since it will stick to the epoxy better than plastic, leaving less voids. Again, I avoid wax paper (it also tears easily if you squeegee over it). Heavier plastic (say, heavier than 2mil) works fine on flat or non-compound surfaces, and can be squeegeed.
Adding pp to a fiberglass sheathing can save a bunch of weight, by eliminating the whole weave-fill process, and allowing/requiring modest squeegeeing to apply. Plastic can do the same, although you can't add resin through it to wet out drier spots, and plastic won't drape. I think pp is a very worthy addition to the workflow any weight conscious builder. It'll also save in resin more than it costs, if that is further incentive. It does add some time to the whole wet out process, so your resin green time needs to allow enough time. You can wet out say a third of the glass, add strips of pp almost to the dry edge, wet another third and catch up the pp, and so forth- I've done this alone when glassing larger hulls.
The cat door was for a stray, temporarily staying in my heated shop last winter. She (and the four kittens we later learned she was brewing) are now at the in-laws. Having a shop cat was fun, but required different work habits. No large panels of fresh epoxy left out to cure, sweeping up before leaving, and such.
Huh, the forum list says Diving Duck had the last post, instead of me, and I'm a "-"
Chad
- tried 4 mil plastic and found that where it was folded before being rolled for sale, the folds and even any small creases, it created a pretty good size lump in the epoxy even if I squeeged it out while wet.
With wax paper, being smoother with no creases, it doesnt leave any lumps and seems to work real well and in some pretty odd places like in the bulkhead slots in dory thwarts...tried plastic and it was too stiff to stay on.
The wax paper comes right off the next day, and I'm told it's OK to do another coat at that point with no sanding, but what is the point about wax paper being inheritly bad?
Thanks for any info, appreciate it!
Curt
Wax is the problem. If you gotta use wax paper, have a rigorous decontamination routine, some thing like acetone and alcohol before an abrasive scrubbing. (None of which can be done while the epoxy is green...)
Oh, OK...maybe the forum source of the info I was reading about wax paper was wrong, so you are saying if wax paper is used, to wait until it cures, and before applying another coat of epoxy to rub it down with alcohol and sand it? That sort of defeats one big benefit of using it to avoid sanding between coats and still have a real smooth finish.
The other use of wax paper I've heard about (and used) is to use it on the last coat of epoxy, and there naturally I would wait until it's cured and sand it
Well one more use is to go over cloth that has been wetted out...provided an amazingly flat surface and I was told it's OK to use wax paper in that application.
Any thoughts on those 3 uses?
Is my epoxy at risk where I used wax paper?
Fortunately the rest of my epoxy work can be rolled and tipped and thus I wouldnt see the need as much for wax paper, or plastic, either one eh?
Sanding a wax contaminated surface can just spread the wax around, and even drive it into the newly keyed surface. Always clean the surface first, then sand. Check the surface by wiping with water and making sure it doesn't bead.
Wax (paper) doesn't bother the coat under it, just every subsequent step. The next coat(s) of epoxy, paint, or varnish is likely to fisheye, bubble, or even lift.