Are kind souls allowed to carefully move this thread into appropedia? I can't do it for lack of time and subject-matter knowledge, but it looks like there could be a page or two for special materials, glues, tapes, etc. Not sure about company info etc so maybe not even a good idea. :-?
Maybe just link to this thread from a fresh page. Lucas El 19/06/2013 05:48, "Jacob Rodriguez" <[email protected]> escribió: > I love this post. Your comparisons of the different points of failure are > very helpful. > > I'm having lots of luck with contact cement and 4 gauge vinyl (like > restaurant table cloth covering stuff). It's probably only slightly more > expensive than BFT in the short term, but it will last much, much longer. > > So far this is proving to have excellent sheer strength, tensile strength, > resistance to direct flame (tested for 15-30sec of direct contact with no > ignition; i.e. no foil tape necessary), and other various environmental > factors. Some day soon, either myself or another kind soul will be adding > information to the appropedia site regarding the application methods and > other fun details. Using this in a semi-folding design means that you are > building a yurt that will for sure last many burns, and will only require > minimal setup on the playa. Also, these two materials not a rare commodity > during the summer before the burn. You can find these items on Amazon and > just about any fabric, hobby and/or hardware store. 6" 8959 is hard enough > to find as it is, much less when you need it. > > I recently tried to break my prototype triangle in half, and it would only > bend into a 90deg curve. I suspect the vinyl played a big part in this > since polyiso is quite easy to break in half normally. And this is only > with about 2 inches on the sides! The boards will not pull or tear apart. > You have to actually stand on one board and pull on the other with all your > strength to destroy the hinge; and even then, the point of failure is the > paper bonding to the foam itself, not the foil laminate or the contact > cement bonding. I was actually surprised to see the foil laminate did not > detract from the adhesion of the contact cement, given that if you peel any > kind of tape or glued fabric from the board the foil comes off easily. I > had even thought about maybe trying to find a way to strip the foil off the > paper, but that's a lot of effort and evidently not necessary. > > Is it as easy as pressing on some tape, not really; but it's cheap, long > lasting and available. > > I can't wait to hear what you come up with as well. I've been testing all > kinds of things from zippers, magnets, buttons, and other types of > adhesives and fabrics. This seems to provide the best weather resistance, > flame resistance, dust resistance and permanence of all the other options > that I've seen so far. > > Good luck!! > > > > > On Thursday, June 6, 2013 8:26:22 PM UTC-7, Charlie Staley wrote: >> >> I have been reading through the postings for a couple of things, one is >> regarding my own interest in tape. While researching the other non >> filament tapes that might be functional, I was thinking that things might >> be over-engineered. I suppose with the possible winds, over-engineering >> may not always be a bad thing. But tonight, I came across a comment from >> Vinay in 2011, mentioning that hexayurt failures are uncommon. Or almost >> unheard of. Is that still the case. The only attibutable cause, so far, >> has been poor construction practices. >> >> There are a few failure mechanisms I can think of. But sideways release >> of tape has not been one that comes to mind. >> Adhesion failure: Causes - contaminated surface, non compatible >> surfaces. Non-shear loads, or peeling. Most of these tapes have fairly >> significant peel strengths, but an adhesion failure from peeling would be >> a truly monumental achievement in poor construction techniques. Like >> hanging something from the ceiling, stuck to one end of a piece of tape, >> with the other stuck to the ceiling. >> >> But shear strength of adhesion would be like hanging same said object >> from the wall. The load is not trying to peel, it is trying to shear. >> Very different scenario. And the shear strength will come from both the >> tensile strength of the tape, and the shear strength of the bond. A good >> bond, under tensile load, also depends on a good length of anchor. >> Example: Make up a moving box and tape the bottom. You will see pros >> wrap 12 inches up the side. Amateurs will use 3 pieces of tape, with only >> 3 inches up the side on each side. Which is stronger? I have seen more >> than a few blowouts on the three piece method. There is only 3 inches of >> tensile / shear, and once the middle starts to fail, there go the sides. >> The 3M bi filament tape states a peel strength of 100 lbs per inch width >> to steel. >> >> Tensile failure. Breaking tape. I don't think any of these are going to >> break sideways. Maybe if the roof were connected only by a ring of tape >> and the wind was able to grab an edge. But I speculate that the adhesion >> would fail before tensile. So for that, some Longitudinal (top to bottom) >> straps connecting the two, or of course, the anchors. The monodirectional >> tapes, and the bidirectional tapes have around 150 psi tensile strength per >> inch width. Bi filament has it of course in both directions. But we're >> not really relying on tensile strength laterally. At least I don't believe >> so. And it's the wide bi filament tape that gets really expensive. >> >> I don't see any shear strength ratings, but I would imagine that it could >> be higher than the tensile strength, given that peel strength is 66% (for >> the 8959 tape). >> >> So that would mean that width is your friend. And even if you do get >> lateral loading, that would be across great lengths, so regardless of the >> tape, the strength is significant. >> There are other tapes that I have found. High molecular weight >> (expensive), and some high strength polyethylene tapes. I would hazard a >> guess that some of the "ultra clear" premium packaging tapes would work, >> though 6 inch width woudl be a minimum. >> >> That being said, am I going to bank my shelter on it. Nope. But, it >> might be a worthwhile experiment. >> >> Another failure mechanism is structural. To some degree, I think the >> tape lends rigidity to the structure, and the structural mechanics take >> over. I put together my foamcore model today. Flip flopping around, >> falling over, shifting around. Then, with a few very small pieces of tape, >> I got the roof on. You can bear down on that sucker, and the load holds >> very well. Where would it be weak? Where ever it could buckle. And that >> depends on the model, and the roof. >> I think that the resulting equilateral triangle sections would be better >> served with an inside tight tape bonding. That is a large segmented flat >> surface. The inside tape prevents the hinge from opening. If you were to >> use a weaker tape, I would further augment that joint with some cross >> lengths, perpindicular to the seam, going a couple of feet to either side. >> Over engineering, maybe. But if you saved money on the tape, it would be >> well spent tossing some of it into over engineering. I'm all for over >> building: if things remain aesthetic, functional, and economical. >> >> I planning on an H13, with a full door. Lots of discussion in 2011 on >> questions, breaking the tape ring. I don't see much from 2012. Though I >> do think that the plywood panels on either side of the doorway addresse >> that issue. I like one comment about bringing the tape ring over the >> plywood and wrapping around to the inside (bonding length). I think by >> leaving a couple of inches of intact plywood at the bottom, and many inches >> at the top, then keeping the door around 30 inches or less in the 48 inch >> panel, and you have a good amount of integrity both for the tape ring, and >> for that huge flat surface and seam that get compromised by cutting into >> it. >> >> If you were to forgo the plywood, I would think that some metal L channel >> might be good in the doorway, on either side, straddling the seams. And >> maybe a plate of plywood or metal to either side of the door to shore up >> that joint. You want to prevent buckling at that wall, and those would >> help to support the weak spot. For that matter, you may want to put plates >> on the adjacent high wall, as that is still a large surface that could be >> taking tangential load. While the roof has large surfaces, the wind >> loading is not direct, and the loads are transferred to the walls. >> Tangential to the wall, some will want to go the adjacent walls, but that >> is a long horizontal seam directly in the load path. >> >> I'm just throwing some of my thoughts out there. If someone does have >> any knowledge of, or stories about failures, I would be very interested. >> But the failure mode is important. Stronger glue using the same crappy >> materials won't help anything. I think that some of the experiments with >> fabric hinges, etc., stand a greater chance of failure than tapes that are >> less strong than bi filament tape. While you a square inch of fabric >> versus a square inch of tape film, the fabric does not have a uniform flat >> surface, so your effective bonding area is very likely far lower than an >> inch. Plus, the outer parts of the fabric are not homogeneous with the >> inner parts. You could have a lint deposit on the adhesive, post bonding >> failure. It would be interesting to hear about some peel tests for that >> type of joint. I'm simply speculating on possible sources of failure. If >> it were to have a peel strength in excess of the bi filament tape, then you >> are probably good to go. If you have a consistent application method. >> >> Anyway, if you do go that path, run some experiments with your fabric. >> Glue it down, how you intend to and leave a strip hanging. The try to >> pull it off, pulling tangentially to the surface. If the foil comes off, >> you're probably good. If the foil adhesion is failing, it don't matter >> what tape, material or adhesive you are using. Also try the test under >> shear. If you get some filament tape (regular filament will be fine), you >> can compare it to that, but use identical widths. >> >> People are spending tons of money on tape, and the tape of choice >> deteriorates rapidly. I think we are surrounded by solutions if we were to >> look and share. It's not worth it to save a few percent of cost on your >> structure, only to have it be marginal. But removing the old bi filament >> is more work. Adding aluminum tape over it is more cost. I think we can >> still build with a comfortable load margin, yet save some time and money. >> > -- > You received this message because you are subscribed to the Google Groups > "hexayurt" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/hexayurt. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- You received this message because you are subscribed to the Google Groups "hexayurt" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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