Re: [hexayurt] An idea for a more permanent tape solution (spray adhesive and nylon)

[hal muskat]

Looks great Jacob. Want to see this on playa.

Note, zippers no good in dust! Dust not great for magnets. Cheap velcro fails in dust.

Where are you located?

Have fun, peace, Phoenix

On Mar 28, 2013, at 1:17 PM, Jacob Rodriguez wrote:

So, I'm going to be building a quarter sized nearodesic polyhedron ("quad") dome (1 rmax sheet  = 8 triangles) for BRC this year.

My foamcore and masking tape prototypes (1:12 and 1:5 scale) have been going well. I'm learning how to do the tape hinges, and how to miter the edges with a razor and angled metal guide. I'm thinking that the full size version will be relatively easy to prepare and construct. My end result is a 6' high, 12' diameter dome that folds down into a 4' x 4' x 15" high box. Minimal tape is required as all but one edge of each quad is hinged with fabric and adhesive. Only the top square, and 4 "corners" need to be fully taped together.

I'm seeing lots of people commenting on how the BFT (bi-filament tape) is not really UV resistant, so it flakes off eventually. Also, that it's barely a semi-permanent solution, even if you do tape hinges instead of one-time assembly. I've considered many different types of ways to join the triangles that would last more than one or two times:

- zippers (needed like 400 of them, really really expensive)
- button snaps and straps (would glue on the snaps to the boards, then use a strap to snap them together; this is not weather proof at all)
- velcro (again, pretty expensive if you use the really good velcro, which is likely the only way to guarantee structural integrity and 'weatherproof-ness')
- magnets (even using strong ones (N45), embedding them in the edges of the triangles, they could jsut fall out, and still not weather proof. also $$$)

..and a couple of other ideas. I've learned that putting metal hooks/rods/bolts (binder clips) through the boards will just rip through it with a strong enough tug. They could end up just getting loose and boring out big holes. Using plus-shaped ("+") hooks/rods to fasten some sort of fabric over the joints are slightly better because they resist being pulled like a wire cutter through the board, but you would have holes in the board and water could get in. Also, excessive force would also just make the holes looser and ruin the boards eventually. But the idea of using some sort of fabric seems to hold merit.

My main goal is to build something that can easily be packed away, and assembled multiple time. Realizing that the main principles of a good BM structure are to seal out rain, dust and light, I think I've come up with a possible solution, but I'm curious why I can't find anyone who has tried it. I'm hoping to get some cautionary tales or some encouragement on using sport nylon (as opposed to ripstop), and some Super 77 or 80 or 90 spray adhesive, instead of the traditional tape.

The cost might be a little more expensive up front (depending on some factors), but I'm thinking that the nylon will last much longer than just about any tape and is probably just as strong (if not stronger) than BFT. From what I've read, a lot of people end up using some 77 spray anyway because of the lubricating residue on the boards. I'm curious if it's more UV resistant (or at least the adhesive would be) and therefore survive the endless sun bathing better. Also, the concept of cutting fabric into strips and using spray adhesive as a backing gives the user many more options when it comes to materials (stronger fabric and/or stronger glue), rather than just limiting to such a rare find as 6" BFT. Though I'm sure that sport nylon "tape" is even more rare. You can also make the strips as wide as you want, so you are not limited there either.

I've built a prototype of a hinged triangle using foamcore, sport nylon and Super 77, which seems very, very strong. Stronger than masking tape anyway. I'm thinking that while it's not waterproof out of the box, I could always spray with some scotchguard, or tape over everything with the foil tape. Foil tape would also help any concerns on fire-hazard as the adhesive is quite flammable. I put a hairdrier on it for about 10 mins on high, to see if excessive heat made the glue loosen, but it did quite well. I'm thinking the higher temp ratings of 80 or 90 adhesive will help in that area. Maybe instead of foil tape. I can spray with some sort of coating that will protect against fire and water at the same time.

For cost comparison, my project would be using about 6 rolls of 60yd tape. That's about $20 a roll. Plus about 4 rolls of foil tape (for outside only) at another $20 a roll. I'm thinking that a can of adhesive will last quite a long time, so I may only need about 3 cans at about $20 a pop. The fabric is not that expensive (maybe 5 dollars a yard), so I think all in all, I might come out saving a little cash (if any at all), but ending up with a much more permanent/reusable solution.

Anyway, what do you all think? I'm going to be purchasing a piece of polyIso to test. I'm going to make a single "quad" using this nylon and adhesive, then leaving it up on my roof for a week or two to see how it handles the weather. It's Santa Monica CA weather so not quite the same, but should give a good indication as to whether it will survive at all.

Thanks for reading!

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[Vladimir Khodel]

Yeap, turns out contact cement (not water based version, do work outside and don't smoke anything while gluing :)) and cordura work great for hinges. Although beefy brass zippers can be found on clearance when buying in bulk, I think more cordura flaps and some velcro to keep things from unfolding would be sufficient:

http://www.appropedia.org/BFD_mod

Good luck and let me know if I can help in any way :)

Vladimir

[Jacob Rodriguez]

Ohh, cordura and contact cement. Perfect example of using adhesives and fabric as a reasonable means of joining the 'angles vs traditional filament tape.

My grandfather also recommended contact cement, as it's waterproof. Using a brush applicator would also make application a little more accurate.

Have you tested this combination in an outdoor (windy and/or wet) environment?

[Vladimir Khodel]

Brass #10 zippers did just fine last year. The idea is to minimize number of edges you want to zip and maximize number of folded ones, which maybe get tricky (see my foldout diagram for the stretch hexayurt case - this folding pattern does pack back into a flat stack of 7 foam sheets).

Good thing about velcro is that you don't have to run it continuously, one 2" square per foot of the edge may actually be fine if you fold cordura over the edge of your foam first.

In general pictures would help this discussion a great deal. :)

Vladimir

On Thu, Mar 28, 2013 at 6:30 PM, Jacob Rodriguez <fracta...@gmail.com> wrote:

Thanks! Forgot about zipper lubrication vs. a dusty environment. Zippers were too expensive though. I would need like 600 feet of zippers in 2, 4 and 4.5 foot lengths. Not very cheap or useful for this application, apparently.

[Vinay Gupta (Hexayurt Shelter Project)]

Hm. (thinks)

Well, first up, have a roll of tape with you in case of problems. Hexayurt tape, correctly applied, will hold damn near anything together.

Second, remember the great breakthrough of the Wright Brothers wasn't inventing the aeroplane. Their real breakthrough was inventing the wind tunnel: after that, inventing the aeroplane was a pretty easy job, a ton of small models and no real safety problems!

Test the hell out of it with small portions. Boards are tough to get things to stick to some times. Glue is unpredictable in the heat (hairdryer?) Loads applied over time can cause glue to creep, like duct tape does. Are the adhesives stable?

I really think something like this can work, but I think it's going to require methodical testing on samples to get something sorted.

I've always wondered about lacing. Eyelets every three inches, and then just lash the hexayurt together.

Finally, watch for the metal skin just tearing right off. Happens with tape if the forces is at the wrong angle, for example. That's a big reason for pre-taping the panels, so that the fastening-tape is sticking to tape, rather than to the much more delicate metal surface.

Good luck, and please document everything!

Vinay

[Vladimir Khodel]

BM 2012 weather was pretty mild, but we did have some 90"F weather, one dust storm and a bit of rain...

Also my design features horizontal bands of tensioned 2" straps which really solidifies the structure to a point where I can single-handedly lift it up by the door :)

2" foam does very nicely under compression...

Cheers,

Vladimir

--

[Chad Cole]

I saw this a few weeks ago and wondered how it would work for
waterproofing seams: http://www.ultraeverdrystore.com/

Just a thought.

[Jacob Rodriguez]

Yea, I totally agree about doing the sampling. That's why I'm starting this early in the year. And I had also been wondering about the stability of the foil side. Having it rip right off is a reason I didn't think the button snaps would work well. What would be interesting would be to cover the entire surface with white nylon (to preserve reflectivity). Fabric coated triangles that are completely waterproof (possibly using the Ultra Ever Dry mentioned below) could be a bit more durable than just the standard backings provided by the manufacturer.

I had also thought about sandwiching the pieces between thin sheets of plexiglass to add extra strength to the board. Lots of ideas running around in my head. The problem is (as my wife is so kind to point out), they are all way more complicated than they need to be.

It would be awesome to create carbon-fibre triangles as they could actually be drilled and hinged. Making it dust and water proof would then become the issue.

I'll keep posting here (with pictures when I can) to keep track of my progress.

Thanks!

[Vladimir Khodel]

So, you should decide on the duty cycle for your structure :) Building something for year-around use and building something for "one week of severe weather per year and the rest of the time sitting in the garage" structure are two significantly different projects. In fact one-week-per-year use does allow you to update/improve/fix up your building before the next use, so even less than ideal materials still make sense.

For example, if some of your panels are damaged or backing does peel off, it is still possible to just cut new ones at a cost of $20-30 per year and reuse the hinges. If your zippers/velcro don't hold anymore you can glue on new ones right next to the old location (it has been my experience that glue-on velcro glue is insanely strong in this application and in fact I want to know what they use, since I was not able to find anything even remotely as strong to glue sew-on velcro on :)).

Main long-term storage concerns for polyiso panels are UV and water - foam does shrink under sunlight and water does cause mold, so make sure your yurt is safely stored.

And of course as Vinay says, a roll of bdf tape makes a great insurance policy (just don't try to apply it in higher humidity, like in the middle of the night in BRC, and don't count on it to last under UV or in storage).

Looking forward to the pictures,

Vladimir

[Phil Dirt]

I had my stretch hexayurt for two burns and so far no problem with the bifilament tape deteriorating.

I used 2" fender washers to attach nylon carry straps to both ends of my yurt. Burn a hole with a heated nail in a section of nylon strapping, common washer under the bolt head on outside, fender washer and nut on inside. Very handy if you have to move your yurt, which I had to do several times.

I put peel and stick foam insulation strips on the bottom edges of my yurt and around the doorway. Helps ensure a better seal.

Like the idea of spray on adhesive and fabric hinge. Make sure you remove all of the fiberglass foam dust after the miter cutting or the tape/adhesive will not stick properly. I wiped mine down with dry rags (change often) then went over them again with rags moistened in paint thinner. Tedious but important.

[Phil Dirt]

Also, if you want to attach hinges on the panels or door and are concerned about bolts tearing through the foam, I just picked up some metal flashing and cut pieces as large as needed, then drilled where I wanted to put the bolts. My door hinges are run through a "U" shaped length of flashing so the stress of the hinges on the bolts is distributed over the entire surface of the metal flashing.

[Chasomatic]

I've been very successful by covering the bi-filiment tape with an opaque metal foil tape. This gives the strength of the bi-filiment with the durability of the metal. I overtape the bi-filiment to ensure a good bond for each joint as I find the bi-filiment has a very poor adhesive. I also found (through bitter & wet experience) that to have a waterproof structure the tape must be pressed into every fold & crevasse of the panels. The panels are not really flat and every fold in the foil will channel water in a rainstorm. I think a spray sealer of some kind would be useful to help waterproof the yurt but I haven't tried it.

My last hexayurt was 6' tall at the sides and 10' tall in the middle. It also folded but not in as neat a box as you describe.

chasomatic

[Jacob Rodriguez]

I don't yet have pics, but I do have progress, and some stats so you all can get an idea of the project size.

The dome uses 6.5 sheets of polyIso board.
It will be cut into 48 acute triangles (8 per sheet, 4x2x4.47), plus 4 right-angle triangles (4 per sheet) and a large 4x4 square.
To tape every edge, I'd need about 600' of tape. 600/3=200yd/60yd = 3.3 rolls of tape (or equivalent)

I'm not sure if I'll be taping every edge, or just using my replacement material to cover the edges as I make tape hinges between all the pieces.

If I use material, I have 112 joints/edges to cover. 96 of those edges need to be hinged (24 edges per quad, 4 quads (duh)). The other edges are the right-angle triangles, and the top square. Since the rolls of material that I've been testing are wider than 4.5 feet, I only need to multiply 112 by the width of my strips to get the length of the material that I'll have to use.

6" strips * 112 joins|edges = 672" of material = 56ft = 18.6 yds of material at 4.5' wide. Not too bad as long as the material isn't too expensive. 


I've found some 4 gauge clear vinyl that is working extremely well. It's cheap at $2.99 for a 4.5x1yd piece (2.99/yd), so even at 19yds, It'll be about the price of single expensive roll of 6"BFT. It's also much thicker, and made to widthstand hot/cold outdoor type environments. I cut the vinyl into 3" strips. (My test board is .75" so I may need to go to 4" strips during production, so that's 4*112 instead of 6).

I've been using contact cement to glue it to the boards. The glue I bought for testing purposes was about $4 for 3oz. and you use about .75-1oz per join. I have 112 of them, so.. yikes. I'm sure I could find it cheaper in bulk and a way to use less. Spray adhesive is probably just as strong, but it's messier, you waste a lot, and it's more expensive. Contact Cement is super duper strong, I'd say stronger than the foil facing is bonded to the paper facing. Probably about as strong as the paper facing is bonded to the foam itself, if not more. Sorry, I don't have pics yet, but when I get the chance, I'll put some up.

To miter the edges, I found an iron guide that's 3' long, and does a nice 60deg angle. It's an "L" shape that's about 1" on one side, and about .5" on the other, just like a capital "L". When you lay it so that the board is the hypotenuse, the short limb is a nice 60deg angle, that I just run a razor blade on. I found that the trick is to not try a single pass cut, but rather to take several passes, doing a little deeper each time. It comes out much smoother and it's easier to keep the razor pressed against the guide. It's one of those trapezoid razor blades, and I just use bare fingers. Seems like the best way, and the less the pressure the better the result. I now have an easy, cheap way to accurately miter the edges and make a more accurate build.

The vinyl should be pretty durable, even in the sun, and since it and the glue is waterproof, it will work really well in the rain. I've tried to pull two triangles apart that only had the vinyl applied to one side, and it was even the hinge side, so some of the vinyl is glued directly to the foam (which should make it less secure). It did not. I was unable to pull the boards apart with a good deal of my strength.

Pics soon I promise. I just wanted to tell you all about my progress thus far, in case it sparks any other ideas/projects.

Thanks!

[Vladimir Khodel]

This is very cool! Let us know how vinyl is holding up in the sun - I am sure it should be fine for a couple of weeks.

A couple of related shortcuts I found are:

1. Walmart sells contact cement by the quart :)

2. To cut foam, particularly thick 2" variety, my Fine Homebuilding magazine suggested taking a putty knife (I used 4" blade) and sharpening curved outside edge. This goes through polyiso like through butter, but making several passes is still a good idea to avoid tearing the foil.

3. For the edge guide I just ripped a 2x4 at 60 degrees - it gives over 2" of surface for the putty knife to slide on. You do want kiln dried 2x4 to avoid warping.

Can't wait to see the pics :)

Vladimir aka chaynik

[hal muskat]

How do you think the glue would work during assembly on the playa? Seems just a wiff of dust could make it less able to adhere?

Are you aware of any of that vinyl with tape peel backing?

Thanks, Phoenix

[Jacob Rodriguez]

Glad to hear walmart came in handy for something. The putty knife sounds good too. I had been looking for something that was sharp like a razor but long as well. A sharp kitchen knife might work well too. I thought about building a rig that would let me slide a blade through at a perfect 30deg angle, but that got way too complicated. I thought about the wood thing as well, but I don't have access to a saw, at least a table saw that could cut a long 2x4. I was lucky to find the guide, and it was only after hours of wandering through the local hardware store looking at everything from door frames to carpet edges to find that perfect angle.

Playa dust could pose a problem, but it would have to be really really dusty. This glue is pretty strong, and there would always be ways to do just a little at a time to be quicker. The idea of course would be to use vinyl for almost all the joints, and then use the regular tape or whatever to tape the pieces together, when in BRC. Tape would be easier to remove or cut at the end of the event, but strong enough for a single week's use. I have some tests planned for July where I take this out to Joshua Tree for a weekend to see how it holds up, and what I might be dealing with. Unfortunately, I don't know of any vinyl that has adhesive backing. At least not this kind of vinyl, and I'm not sure the adhesive would be that good anyway. You could maybe look at counter tops and that whole industry. Contact cement and some of the strongest glues are used for putting laminates on counter-tops; we are laminating after all.

I have some pictures for you all today!!

Here is a shot of the guide that I'm using, and my method of cutting. The cut is obviously made already, but you get the idea of how it works. It's like cutting the matte for a picture frame, but on a really big scale. I push against the guide with my pointer finger, and slide the blade downward into the board with my middle and ring fingers on each pass. Doing light passes and holding the guide down with my other hand makes it easy not to push the guide while cutting. Definitely requires some practice.

< see ironGuide.jpg >


Here are the two types of "tape alternatives" that I'm experimenting with. ON THE RIGHT: is orange sport nylon and spray adhesive. This has been done and sitting around for a while, inside. You can see that there's some separation between the edges and the nylon. It's still holding fine on the laminated face, but I think the microscopic surface area of the foam is not holding that well to the Super 77 spray. Contact cement blows 777 out of the water in terms of strength and durability. Keep in mind, this combination is not waterproof, but looks pretty interesting, and was a good starting point for experimentation. I think if I use the nylon, I'll put it over the vinyl to cover the unsightly mess that the glue makes. ON THE LEFT: is my latest concoction of 4 gauge vinyl and contact cement. The vinyl is pretty clear so it's hard to make out, but the cat-pee colored contact cement is pretty obvious. It would look much better with strips of brightly colored nylon covering them. The vinyl is about 3-4 times thicker than the nylon, and I've tried to pull it apart again, and I can't, it's seriously not going to come apart. And I'm pulling it away from center, so if it was going to rip off the foil, it would. I could probably tear it, like a phone book, but I won't try that just yet. I'm thinking that all put together, this thing is going to be super solid in BRC weather. I'm still not sure if I'm going to pre-tape the edges with masking tape, because that will for sure ripple in the sun, which will undermine my gluing, and if any moisture gets on it, it'll start to come off; again, undermining my glue job. I'll try to cover those scenarios when I do my "worst case scenario" testing, before final build.

< see tapeAlternatives.jpg >


While the vinyl is definitely the front-runner, here is a problem that can occur if you're in a rush. Once this stuff touches the cement, it sticks and cannot be moved.

< see vinylRipples.jpg >

I've found that the following steps are the best way to put on one side of a join.

1) Roll a strip of vinyl in your desired width, into a tube. I highly recommend marking a dotted line down the center of the strip (length-wise) so that you can make sure it's constantly centered.
2) Put the two triangles together on the ground the way you want to glue them.
3) Glue the entire length of the faces near the edges. If you are using a 3" strip, put glue on the laminated face, from the edge til about 1.5 inches inward. When you finish doing this, the end you started on will be ready for gluing.
4) Apply a little glue to the first 3-4 inches of the vinyl strip (unroll a little if you need to). Wait a few minutes to let the glue set and get tacky.
5) Glue this first piece to the glue on the laminated surface. Make sure to use your dotted line to keep it straight during these first few inches.
6) Repeat steps 4 and 5 for every so many inches; probably about 4-6 at a time. Put glue on the vinyl, stick it to the board, repeat until you're done, centering all the way down.

When I did this, it took about 10 minutes. With two people, it could be done in under 5, easily.

If you are doing a side where you are gluing vinyl to foam. It's best to do the foam edges first, then make another pass doing the sides. There is some skill required to not get any ripples, so I suggest trying this out with foam-core and masking tape first. That will teach you how to press things together so you don't get any ripples. Mitered edges make things a little tricky.

You'll notice that sometimes the vinyl will bubble a bit after it's been glued to the board, even though it was put on straight and you didn't notice any immediate bubbles. I think this is some sort of chemical or physical reaction from the glue and vinyl, but it goes away when the glue is completely dry. It will also feel a bit soft, but don't mess with it or poke at it. Just leave it and it will go away. If it doesn't, it might be bubbles that you accidentally trapped without realizing, or you didn't center your strip jsut right and made a small change in direction. It's most likely just a chemical reaction, and no harm will come in any case. I also used less glue this time around, so I'd say it's about .5 to .75oz per join, per side. Still not bad.

Today I put out my best vinyl triangle (vinyl on both sides of the join) in the sun for the afternoon. The vinyl didn't even notice it was outside. I suspect that it's been cooler, the heat wasn't able to get to it in the right way. The sun didn't do shit to it, but I have yet to get it into the 90's. It's hard here in Santa Monica. I may leave it in the car in the sun to get it heated up. Or maybe just try the blow dryer and a thermometer to figure it out. I think this is going to be a really good solution. This kind of vinyl is used for all kinds of outdoor things so easily last through 2 or 3 burns I think. This is like the vinyl they use on tables at outside restaurants or on soft top convertible cars, or patio furniture. It's made to be used.

Anyway, I leave you with a pic of my various prototypes. On the bottom is my full size triangles (4'x2'x4.47') though not the full 1" thick yet. The 4 form-core/masking tape wedges and the other foam-core pieces show what the dome (or a 1:4.8 scale) will look like when it's disassembled for travel. Each wedge will be 4'x2'x4.47' @ 12" thick. The final packed 4'x4'x15" dimensions mentioned in my original post also include the 4 triangles and the top square (3 extra inches in height). The small dome is the final goal, and I used that one to test the difference in mitered edges. I had heard it was difficult, or required a dust system, but it doesn't really. I guess only if you use a saw, but a angled guide and a razor work just fine and almost no 'dust'.

< see prototypes.jpg >


Thanks!

[Jacob Rodriguez]

So leaving the vinyl in the car, under 'direct' sunlight has shown one strength, and one weakness in my implementation.

The good news is that the vinyl stays very stable, and so does the contact cement. No warping or pulling like duct tape does, and no loosening of the adhesive at all. Even where the vinyl is cemented directly to the foam, it has yet to show any signs of weakness. This is still at only about the high 70's Fahrenheit, so still not verified as playa-safe just yet.

The bad news is that 'edging' all the triangles with masking tape is not a good idea. The adhesive is not durable enough, and becomes loose in the heat. If most of your cemented area is on the masking tape, then you are undermining your construction. It is better to directly adhere the vinyl to the boards, including the exposed foam edges.

While the vinyl was nice and warm(soft), I was feeling confident and tried my "tear like a phonebook" test. It passed this easily. I was more worried I would snap the boards than tear the joins. This method is likely to leave the joins more stable than the actual polyIso itself, so if the boards can handle the wind, these joins should have no problem.

I highly recommend/encourage others to try this method out and let me know how their testing goes. This could be a viable solution to a more permanent structure.

[Vladimir Khodel]

I also like the fact that vynil is in fact waterproof, unlike my cordura setup (which can be coated in water repellent of course, and is a tad stronger :)).

Question: I was using K-hinges, where 2 strips of cordura are placed on top of each other and sewn in the middle lengthwise to form a K and then top of the K is glued to one board and bottom to the other, wrapping the boards and covering the cuts. The sewn line of threads in the middle of the K become the hinge.

Are you saying that just attaching one strip of vynil on each side of the boards just as we do with bdf tape is sufficient to hold things tight?

That would simply things by a lot :)

I guess we need you to produce some close-up shots :)

Thank you!

Vladimir

[Jacob Rodriguez]

Wow, that K cut sounds crazy. Yeah, this is much simpler. Exactly like the tape hinges; or at least what I've been imaging tape hinges to be (full length).

Here's some close-ups of my best example thus far. If you look close, you can see the dots I used to keep the vinyl centered. I'll have to work on what to do about the pieces that hang off the edge. I've just wrapped them and glued them, but I'd like to do a cleaner job in production. I may do the joints first, then laminate the edges; not sure yet. This is the sample that I leave out in the car and put under the sun to see what will happen.

What I'm curious about, and hoping someone can help, is the angles of the mitering. On my 1:4.8 scale model, I used my iron guide to angle the hypotenuse edges of each triangle. Each triangles hypotenuse was mitered @ what I'm guessing is 30deg. I say "guess" because I'm not sure of my math. The iron "L" guide is 1" x 5/8"x3' long. However, this produced a bit of a gap on the inside. Maybe doing both of them is too much, and maybe only one per every other triangle is enough.

This is tough to explain. I included a shot of the specs I've been working with, at the bottom shows which edges I'm considering mitering, and which edges will be hinged.

The triangles in this photo only have one mitered edge, and they seem to produce the correct corner angle, but I won't know until I build a full size hex/quad piece.

[Jacob Rodriguez]

You know, after re-reading that, I think I get what you mean by "K". The idea here is sort of a mix of the two concepts. You get a K, by doing it the BFT way.

For terminology, let's refer to a single strip of material adhered to the space between two triangles, on one side, will be referred to as a "join". If you were to put another strip of vinyl on the opposite side of this join, you would create a "hinge". 1 sided = join, 2 sided = hinge. Where you have vinyl glued to the foam edge, you have a "gutter". Where the vinyl is only glued to the board, you have a "flat".

It folds like an accordion. From the outside, you would see a gutter, then a flat, then a gutter, then a flat...... This is important when trying to consider which way water will flow. Where will your gutters go and how will you make sure water doesn't follow them directly into your dome? I'm thinking of putting gutters on the top corners, with some overhang (like a spout). For every 'gutter', the opposite join will be flat. For every flat join, the opposite side will be a gutter. The great thing here is that instead of having to sew the vinyl together length wise, the fact that the boards won't sit exactly next together when you join them, there will be about 5mm gap. When you create a hinge with vinyl on the opposite side, the center of this strip will just become glued to the vinyl on the opposite side.

This is with a double miter:
  _______     _______
         \   /
  ________\_/________

This is with a single miter:
  _______    _______
         \  |
  ________\_|________

That flat bit there in the middle will be where your vinyl will end up glued together. The top part is the 'gutter' join, and the bottom is the 'flat' join. These alternate to make it fold up. Ideally, you'll end up with just one "flat" join to do when you get to the playa (plus the quads to eachother, then to the equilateral triangles, and the top square), and that can be done with BFT or whatever since you'll end up having to cut it in order to fold it all back up again. This would be where a zipper and flap would be another more permanent solution.

Hell, the vinyl and cement is so strong. I've thought about putting a small pipe in certain places to make a "pull this" type of setup. You pull a thin nylon rope and it unfolds the entire dome. Maybe next year ;-p

[Vladimir Khodel]

Yeap, K-hinge name comes from MikeP (http://rotordesign.com/bm/category/yurt/page/4/) and does involve some sewing machine time ;) but of course glue serves the same purpose with vinyl.

Your 5/8" x 1" guide gives 32 degree angle, which should be close enough to 30 :)

Question is what sides are you mitering? That neargeodesic thing looks really scary and I would not be surprised if not a lot of those angles were similar or even nice integers...

In fact the original paper by Harris seems to confirm that:

http://www.tilings.org.uk/Hexayurt_Family.pdf

That looks like some messy math :)

You could label all the miter sizes on your foldout - it helped me a lot when doing the actual cutting for my yurt:

http://www.appropedia.org/File:Foldout.jpg

but yours is a lot more involved...

Awesome stuff!

Vladimir

[Jacob Rodriguez]

Yes, this is awesome stuff... as my wife would say "great craic altogether!!"

I like the foldout.jpg you sent me. I think I will make something like that instead of my crappy ascii art.

I did see that pdf you sent as well somewhere before, but lost it; thanks for the reunion! This time I really looked at the angles. So far, I've been using the approach of using my 32deg (thanks for that too!) guide on every angle, but it seems that might be the ticket for every other angle. For each flat face:

 do NOT       ^
 miter this  /|\
  side  ->  / | \ <- miter this side @ 30deg for 150deg angle
           /  |  \
          /   | <-\--- do NOT miter the center hinge
         /____|____\

  do not miter the outer edges
  miter the top square (and equilaterals) @30deg instead.

Because all the angles between boards need to be about 150, my ~30deg guide should do the trick. That answers my question too, because I should only be doing mitering one side of each join. I'll have a bit if inaccuracy here and there, but I'm sure my mitering is going to blur that .5 to 5deg margin of error pretty quickly.

That explains why my 1:4.8 scale proto has too much space on the inner gutters of the quads; both hypotenuse angles are mitered. Interestingly enough, I did not miter the outer edges of the quads but I did miter my top square. That is a near perfect fit. That should have clued me in.

YAY!! I have my answer. I will begin production in mid-June, after a bit of a "wedding season". I will add my full documents here too, just in case anyone else wants to have a nosey.

Thanks!!!

[Vladimir Khodel]

I think you got it :)

Now that you have all these things worked out, you might want to start a wiki page at appropedia.org, it's a nice format for editing things and linking in diagrams and pictures. I hope it's ok with Vinay! :)

Also think about the door ;) (e.g. http://www.appropedia.org/BFD_mod) and where to run rope/straps to attach this thing to the playa, it could be tricky...

Can't wait to see your project on the Playa!

Vladimir

[Vladimir Khodel]

Cordura/contact cement combo definitely works and allows hinges, zippers and loops for the straps to be sewn on (see pictures at http://www.appropedia.org/BFD_mod).

Depending on what your source is it could be a lot more expensive that vinyl though, so YMMV :)

Ground tarps come in many materials and the glue for polyethylene based stuff is really expensive (3M spray) as it turns out :) Of course if you get your hands on the vinyl coated variety  (used to be sold by Costco but not anymore) contact cement should do the trick. I am not sure if the tarp is strong enough to last many years, but it should work fine for a week.

Let us know what you picked!

Cheers,

Vladimir

On Tue, May 28, 2013 at 10:02 PM, Darin McEvoy <mcevoy...@gmail.com> wrote:

My brother and I are building a yurt for this year's burn. We stumbled across your thread and are very interested in your idea. We were thinking about other fabrics to use that would be durable, waterproof, UV resistant, and cheap. What about using a cut up ground tarp with the edges of the strips sealed to prevent fraying. Thoughts? Anyone tried this?

Darin Mc

On Thursday, March 28, 2013 1:17:41 PM UTC-7, Jacob Rodriguez wrote:

So, I'm going to be building a quarter sized nearodesic polyhedron ("quad") dome (1 rmax sheet  = 8 triangles) for BRC this year.

My foamcore and masking tape prototypes (1:12 and 1:5 scale) have been going well. I'm learning how to do the tape hinges, and how to miter the edges with a razor and angled metal guide. I'm thinking that the full size version will be relatively easy to prepare and construct. My end result is a 6' high, 12' diameter dome that folds down into a 4' x 4' x 15" high box. Minimal tape is required as all but one edge of each quad is hinged with fabric and adhesive. Only the top square, and 4 "corners" need to be fully taped together.

I'm seeing lots of people commenting on how the BFT (bi-filament tape) is not really UV resistant, so it flakes off eventually. Also, that it's barely a semi-permanent solution, even if you do tape hinges instead of one-time assembly. I've considered many different types of ways to join the triangles that would last more than one or two times:

- zippers (needed like 400 of them, really really expensive)
- button snaps and straps (would glue on the snaps to the boards, then use a strap to snap them together; this is not weather proof at all)
- velcro (again, pretty expensive if you use the really good velcro, which is likely the only way to guarantee structural integrity and 'weatherproof-ness')
- magnets (even using strong ones (N45), embedding them in the edges of the triangles, they could jsut fall out, and still not weather proof. also $$$)

..and a couple of other ideas. I've learned that putting metal hooks/rods/bolts (binder clips) through the boards will just rip through it with a strong enough tug. They could end up just getting loose and boring out big holes. Using plus-shaped ("+") hooks/rods to fasten some sort of fabric over the joints are slightly better because they resist being pulled like a wire cutter through the board, but you would have holes in the board and water could get in. Also, excessive force would also just make the holes looser and ruin the boards eventually. But the idea of using some sort of fabric seems to hold merit.

My main goal is to build something that can easily be packed away, and assembled multiple time. Realizing that the main principles of a good BM structure are to seal out rain, dust and light, I think I've come up with a possible solution, but I'm curious why I can't find anyone who has tried it. I'm hoping to get some cautionary tales or some encouragement on using sport nylon (as opposed to ripstop), and some Super 77 or 80 or 90 spray adhesive, instead of the traditional tape.

The cost might be a little more expensive up front (depending on some factors), but I'm thinking that the nylon will last much longer than just about any tape and is probably just as strong (if not stronger) than BFT. From what I've read, a lot of people end up using some 77 spray anyway because of the lubricating residue on the boards. I'm curious if it's more UV resistant (or at least the adhesive would be) and therefore survive the endless sun bathing better. Also, the concept of cutting fabric into strips and using spray adhesive as a backing gives the user many more options when it comes to materials (stronger fabric and/or stronger glue), rather than just limiting to such a rare find as 6" BFT. Though I'm sure that sport nylon "tape" is even more rare. You can also make the strips as wide as you want, so you are not limited there either.

I've built a prototype of a hinged triangle using foamcore, sport nylon and Super 77, which seems very, very strong. Stronger than masking tape anyway. I'm thinking that while it's not waterproof out of the box, I could always spray with some scotchguard, or tape over everything with the foil tape. Foil tape would also help any concerns on fire-hazard as the adhesive is quite flammable. I put a hairdrier on it for about 10 mins on high, to see if excessive heat made the glue loosen, but it did quite well. I'm thinking the higher temp ratings of 80 or 90 adhesive will help in that area. Maybe instead of foil tape. I can spray with some sort of coating that will protect against fire and water at the same time.

For cost comparison, my project would be using about 6 rolls of 60yd tape. That's about $20 a roll. Plus about 4 rolls of foil tape (for outside only) at another $20 a roll. I'm thinking that a can of adhesive will last quite a long time, so I may only need about 3 cans at about $20 a pop. The fabric is not that expensive (maybe 5 dollars a yard), so I think all in all, I might come out saving a little cash (if any at all), but ending up with a much more permanent/reusable solution.

Anyway, what do you all think? I'm going to be purchasing a piece of polyIso to test. I'm going to make a single "quad" using this nylon and adhesive, then leaving it up on my roof for a week or two to see how it handles the weather. It's Santa Monica CA weather so not quite the same, but should give a good indication as to whether it will survive at all.

Thanks for reading!

[Jacob Rodriguez]

Yeah, haven't tried using tarp material, but I'm starting to think that just about anything that is plastic-like will work pretty well. I haven't seen cordura, so Vladimir is the expert in that material. My concern when reading about it on wikipedia was that it might not be entirely waterproof, but I'm probably incorrect here. On a door it might be ok, but on your roof, hmmm.

[Steve Upstill (Swifty)]

I LOVE this discussion of hinging technology and I'm sold on replacing my "permanent" tape hinges with the vinyl/contact cement combo--at least for purposes of experimentation. Could someone with experience provide a quick buying guide for the stuff? Vinyl is a many-varied beast and it would be nice to know exactly what to head for. Is Tap Plastics my friend in this department? Anybody have any data about 4" vs. 6" strips? ...and so forth...

Many Thanks,

Steve Upstill

[Jacob Rodriguez]

Sorry, not sure about "tap plastics". The stuff I'm buying is used for covering furniture, or used as storm windows or whatever. Marine vinyl is really good. I used to think it was 4 gauge vinyl, but it's actually 12 gauge. Probably best to make sure it's UV treated, but mine doesn't say specifically and is proving itself quite well outside for the past month or so. No cracking or getting hard or anything. Anything that is sold to be used outdoors is what you're looking for.

Here's a link to Amazon to give you an idea of what you want: http://www.amazon.com/No-Manufacturer-Gauge-Clear-Vinyl/dp/B003ZFA4LM/ref=sr_1_1?ie=UTF8&qid=1373261515&sr=8-1&keywords=12+gauge+vinyl

I've also just updated a document that explains a lot of stuff here. One thing I just learned is not to use the "eco friendly" contact cement that cleans up with water. Use the hardcore stuff. I'm all for saving the environment, but the 'Woodweld' in a green can is not what you want (takes too long to get tacky and dry). Find the "original" stuff in the red can if you can.

Using 4 vs 6 inches is up to you. I'm personally going with 4 inches for my tight hinges (giving me 2 inches of contact on either board) and then 7 inch strips on my loose hinges (3 inches will be taken up by my board thickness (1.5"), and then 2" on each surface). In my experience, that seems to be plenty strong. See my tests (labeled "Test") on various things. Those prototypes only have 1.5 inches on each board, and some of that is over masking tape, reducing their adhesion; they hold up pretty well. Though it never hurts to overbuild, and if you're doing a regular hexayurt, you won't use too much, so why not? On my quad dome, I have something like 136 joins/edges that need to be done, so I will require about 31 yds of the stuff. Something like that anyway.

Have fun!

[Steve Upstill]

Thank you, Jacob! This is most useful. (…and I hope I'm not intruding too much on group bandwidth by thanking in public.)

Steve Upstill

[Steve Upstill]

Just one more question: is there a socially-sanctioned solvent for cleaning up the residue left behind by old yucky tape? (I assume that cleaning it up is a good idea before bonding with contact cement, yes?) I'm thinking acetone, but others with more experience may have better ideas…

Thanks,

Steve

[Bill Wiltschko]

Kerosene also works.  It's cheap, less volatile, and less dangerous than acetone.
 

Bill Wiltschko

bi...@wiltschko.org

 

 

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[Cody Firestone]

GOOGONE has also worked for me in the past on sticky stuff.

[jeff harrison]

you might try this  http://bit.ly/10EHH1l

not sure if you can find it locally or not

[Steve Upstill]

Thanks for that, Jeff. That would be equivalent to Goo-Gone, right?

Cheers,

Steve

[Bruiser Smith]

Hi Jacob - 

I've read your posts on here, the guide and videos on your Google Drive, as well as your posts on Eplaya. First off - thank you for putting together such a comprehensive guide! I am looking to apply this to my pentayurt (H10) this year, and have a couple questions which would greatly help me out:

1. What are your thoughts following the method of foil taping the edges rather than using masking tape or contact cement? I already have a large roll of 3" foil.
   
2. For the 'loose' hinges, did you use both 7 inch on the inside as well as the outside?
   
3. Thoughts on using vinyl/cc hinges for doors & windows?
   
4. For my structure, which needs longer lengths of vinyl, can't I just buy a few yards of vinyl and cut them length-wise?
   
5. Thoughts on using a hand roller to minimize bubbles? http://www.istscientific.com/user/products/large/quickseal-hand-roller.jpg

Again I can't thank you enough for putting together all of the resources that you have!!!!

[Dan March]

Watch out for contact cement losing it in high heat!  I used it (the original non-water-based - because DAP recommended it over the water version) to attach vinyl fabric in my interior build-out of my Sprinter here in LA (where we see Burning Man temps).  It started off looking great, seemed to have an excellent bond to metal, wood, etc.  When it started letting go a year or so later, I asked around and sure enough, it's not that uncommon.

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[Hunter]

Was that a total year outdoors or just 10 days?

[Bruiser Smith]

Did you use the DAP Weldwood HHR Contact Cement specifically? 

http://www.yourautotrim.com/noname37.html 

It seems like it's highly recommended for vinyl applications for car interiors as it's rated for 250F.

[Dan March]

Interesting-looking product.  Commercial grade?  Don't know about you, but I'm in California - where it can't be shipped... or sold?  I talked with the DAP factory rep who assured me that the Original Contact Cement was the best I could buy.  The can says "High heat resistance."

If the material your link talks about is available, I'd love to know how to get some.

[Bruiser Smith]

From what I've read in this thread http://www.hotrodders.com/forum/what-adhesive-do-i-use-vinyl-228613.html maybe check with a local automotive upholstery shop. Read through there but they say that 3M Top & Trim adhesive is also good. Or, if you can't get either due to California law, check with the upholsterer to see their recommendations.

[Dan March]

Thanks... did that... also boat builders... nada but special equipment-needed manufacturing grade special-stuff.

[Vinay Gupta (Hexayurt Shelter Project)]

I love this mailing list. I love it. Very glad to have smart people making sure the technical details are right. Much appreciated, chaps.

V>

-- 

Vinay Gupta    hexa...@gmail.com   http://re.silience.com

Free Science and Engineering in the Global Public Interest

UK Cell : +44 (0)7500 895568 Twitter/Skype/Gtalk: hexayurt

"In the midst of winter,  I finally learned that there was 

        in me an invincible summer" - Albert Camus

[Jacob Rodriguez]

Hey Brusier! I'd be glad to help!

1. Yeah, I don't see why not. If it's the kind of foil tape that I'm used to, it has that sticky paper backing, yeah? My only concern would be that the foil *could* maybe, might, potentially come loose-ish; whereas masking tape or similar is a single layer. But that's a small concern, and a really big IF. Since the point of pre-taping is to avoid having to apply cement directly to the foam; as long as you have a higher vinyl-to-rmax contact than you do vinyl-to-tape, then you should be good. I suspect the foil on the tape is probably as good as the foil on the rmax, and that holds just fine. We even swapped out the masking tape at one point for all-weather duct tape and that also did the job.

2. I wanted to have at least 2 inches of contact on each side of the gap so I used 4" wide strips for the tight hinges and 7" wide strips for the loose hinges. My boards were 1.5" thick, so that's where the extra 3" went. After pre-taping, I had about 1.75" of direct vinyl-to-rmax contact and sometimes even closer 2" because of the mitered edge being nearly as wide as my tape.

3. If you can do it, I would do it. Even though the application is more involved, you are essentially making a strong thick "tape". Wherever you would have thought of using tape, VCC will be a good, more permanent solution. The doors on my dome were hinged with vinyl and they worked really well. The great thing about vinyl is that you can choose different thicknesses to suit your needs, and many are nearly crystal clear, perfect for windows.

4. Definitely buy a few yards and cut it really long. That's what I would do if I were you. While it's not entirely frowned upon to use two pieces end to end, you'll need to note that when you pull off any BFT that you do end up using, it will be tricky to not pull up the second strip of vinyl a little. Contact cement can be stronger than the adhesive of BFT, but not always, especially if it was tape that didn't have a lot of exposure.

5. Yeah, a hand roller would be brilliant! I'd still recommend to brush on the contact cement, wait a couple mins, then unroll a strip of vinyl onto it, but we did spend a lot of time using our finger nails or glass bottles to press down the vinyl. A little 2-3" hand roller just might be my next bit of gear in my dome maintenance kit. Thanks for the reminder! You'll almost never get all the bubbles out because the glue will be very very tacky. Slowly unrolling the vinyl onto a tacky glue surface is your best chance at fighting lots of bubbles. Any that do form will likely go away as the cement cures.

As for the contact cement coming loose, YMMV. Mine hasn't yet and it's just about to be 1 year old, having only ever seen 8 days of sun last year. The contact cement now has a "tan" and is a bit more "Pacific Islander" than "cat pee yellow", but feels just as strong as the day I put it on. The dome only needs small maintenance (due to careless tape cutting/removal) but has no issues otherwise.

[Bruiser Smith]

Thank you everyone for the discussion - especially you Jacob! And a note from Vinay <blush> to boot! I am planning on doing this over the next week of a modified H10 semi-folding yurt with vinyl. I found an automotive upholstery place by me which will sell me the DAP Weldwood Landau Top & Trim HHR for $13/qt, but I have to provide my own quart can. I plan on picking this up from Home Depot for $3. The cheapest I have seen it is about $47 shipped per gallon, and although I may need more than 1 qt the shop is right by me and I figure I can always buy a second qt to cut down on extra waste.

I then also have a roll of 60yds BFT to tape the roof cone, tape ring, tarp ring, and then still have extra to boot for anyone who needs it. I will definitely be taking a lot of photographs and can send them to you Jacob to add to your Google Drive for those wishing to do a hybrid approach. 

Again - can't thank you enough for putting together such a great guide!!! I'm looking forward to how this all turns out!

[Bruiser Smith]

I can gladly report back on a couple of things after getting some work done. Keep in mind that the numbers below are for an H10 pentayurt.

First, I *highly* recommend using foil tape on the edges. It made the process of gluing things together a dream. I used 3" tape that I had until I ran out, and then bought replacement 2" at ~$8 per 60 yard roll. I used 2.25 rolls to do everything and now have some to take out with me for repairs.

I also used a specialized form of DAP contact cement - DAP Weldwood HHR Landau. It worked AWESOME! Super quick to tack, and produces an immediately strong bond between the RMAX and the vinyl. I was able to find a local auto interior shop to sell it to me for $15/qt. I'm not done with all the seams I need to do but overall it has worked beyond my expectations. 

The important thing to note about this is that it is designed specifically to bond vinyl to anything and have high heat resistance. So, there wasn't any heat/disfiguring of the vinyl for me using this. I attached the vinyl basically in the same way shown in the video wiki for this. 

I ended up not using a hand roller - the vinyl seemed to go on pretty flat and although the adhesive isn't super pretty, the bond seems to be even throughout the vinyl.

[Jacob Rodriguez]

Wow, haven't been here in a while. I'm glad to hear another person trying out the tek. I'm curious how it turned out.

Oh man!! I didn't think about using foil tape for the edges!! That sounds like a perfect idea. Using FSK tape would be almost exactly like the rest of the laminate!! Awesome suggestion. I'll have to put that in the docs.

I may use that idea when I have to build another. Thanks Shawn!