Good material for MYOG cuben tent prototype

I notice that the cheap blue tarps don't stretch much. I buy mine at dollar stores, Big Lots, etc. Don't know how they compare in price per square yard to tyvek.

mylar would be good if you can find any

"space blankets" are aluminized mylar which might work and might be cheaper

+1 to Jerry. I was going to suggest something like the Coleman emergency blanket. 82-1/2" x 53" so it's already close to the width you'd get from a roll of CF. Pretty cheap too, only a few bucks at big-box stores.

If they don't need to be too large, I could give you a couple of those mylar wraps they hand out after races.

Forgot to watch this thread, so I am just now seeing these responses. Whoops!

Good idea on the Mylar.

Sharon, thank you for the offer. One of my panels is going to require the full 54" width of cuben (panel is 53" finished), so I think I'll need fairly large pieces to mock it up.

Any clue where I could find mylar in larger quantities or by the roll?

Thanks again for the help. Here's a teaser of what my tent will (mostly, probably) look like:

A few design goals/ideas:
-overlapping/zipperless doors a la ZPacks
-Hybrid double wall (maybe)
-6 stake, 2 pole setup
-2 doors/vestibules
-No sewing

It's basically a combination of design features from TT Notch, SMD Haven, and ZPacks Duplex. It'll have plenty of room for a large wide inflatable mattress.

I've got pretty much everything planned out, but I want to build a prototype first to test a few things. It should weigh about 20oz using .74 cuben for the fly, 1.4 cuben for the floor, and nanoseeum walls/doors.

EDIT: added details

Most of the google hits were rolls of 48″ wide. Here’s one that’s 54″ wide by 25′, 2-mil thick:

https://www.hydroponics.net/i/133013

They also have a 1-mil roll for a few bucks less.

Erik,

That's an interesting sketch. What tool did you use to model the curved panels and (I assume) catenary seams? Is it a SketchUp plug-in?

Thanks

cp

I used SolidWorks 2013 to create the model in the image above. I can go into further detail on specifically how I made the curved panels if anyone wants it. The curves are just circular arcs, not true catenary curves.

At the moment, I cannot create flat patterns for panels with complex curves and curved edges. I can, however, create flat patterns for curved panels with straight edges. That's what I'm doing for my project, and I'll hand draw the curves onto the panels.

SolidWorks 2015 has a new feature that allows you to flatten some surfaces, so if I can get my hands on a 2015 license, I might be able to make patterns with the curved edges included. With SW2013, I have to treat the surfaces as sheet metal in order to flatten them, which is somewhat limiting. Unless you're printing full scale patterns though, you'll have to draw your own curves anyway, so the straight-edge patterns are still pretty useful.

Below are the basic dimensions and patterns for my shelter. Note that I was able to flatten the door panel, which is a curved panel but has no curved edges. I added 1/2" to all edges for seams.

That mylar looks like it might be a great material for prototypes, pretty inexpensive too! I was about to pull the trigger on 150' of Tyvek from Home Depot, thankfully I didn't yet. :)

BTW, If any BPL members want models or patterns made, I'd be happy to draw them up. I love playing around like this with SW. I can export files in many formats, just let me know what you want and I'll see what I can do.

EDIT: The image of the patterns is pretty small/unclear…Here's a link to a PDF file:

https://dl.dropboxusercontent.com/u/171498663/solo%20tent%20v2B%20-%20patterns.PDF

Hi Eric

> SolidWorks 2015 has a new feature that allows you to flatten (any) surface,
I don't think so – not 'any', just some.

Some curved surfaces can not be flattened, for any of several reasons.
Obviously, if the surface is curved in 2 dimensions, you can't flatten it.
Other surfaces require you to solve an elliptic function, which is currently an NP-hard problem – can't be done. FYI: elliptic functions are used in some good cryptography for this reason!

Mind you, how many will be designing tents with such curvature? :-)
(Mine do, and I had to use fairly sophisticated approximation techniques.)

Cheers

Roger,

I haven't played with SW2015 at all yet, so I haven't used the new feature. I'm sure you're right: Not *all* surfaces can be flattened (I'll edit my post above to correct that). Some of the demo videos look pretty impressive though. Have you used it?

For the purposes of planning out patterns for a tent, I think my method will be close enough :) I expect the finished dimensions to vary slightly from my design, but not enough to affect function. Now that I've done it a few times, I can generate patterns pretty quickly. Will a lot of people be designing tents with such curvature? Probably not, but I will!

What does NP stand for? Nobel Prize? That is cool to know about elliptical functions in cryptography.

Nice design. The only place where you might need some sewing is at the peaks where the poles meet the fly. Between the poles and the top guy outs, there will be a good amount of stress pulling on your ridgeline & panel seams. I think you can design around it though.

Ryan

Thanks, Ryan.

I'm confident that I can avoid any sewing. The area you mentioned will be highly reinforced. Plus, I can't sew to save my life! :)

Thanks Erik.

I googled for SketchUp add-ins for 'fabric modelling', and there do seem to be some. There's a nice demo of a 'soap bubble' surface generator in YouTube. Actually, there are lots of nice SketchUp demos in Youtube…

I'll add it to the list of rounduits…

Even if you use a tool like this, and can unwrap the curved surface, the panel shape will still be imperfect due to the fact that the fabric will have anisotropic stretch (little in warp and weft directions, quite a lot in bias directions). And then there's the difficulty of finding the shape of bent poles when loaded by a tensioned flysheet… About twenty years ago, I pondered using finite element and simulated annealing methods to try to determine the complex shapes, using a mesh-of-springs model for the fabric (four, very high constant springs (or inextensible beams) for the warp and weft directions (two shared with adjacent mesh grids), and two softer springs diagonally across the corners to mimic the bias), all springs free to pivot at their ends. But got no further than pondering…

P/NP problems:

http://en.wikipedia.org/wiki/P_versus_NP_problem

Just want to say I love the level of gear-geekery on this site…using CAD, FEA, etc for MYOG tarps and tents. Excellent. :)

What tape should I use for my prototype? I'm going to use 3M 9482pc or 9460pc for the actual shelter – should I just use that for the prototype as well? Any preference between the two?

Thanks again for the tips and advice. Can't wait to get going on this! It's been awhile since my last MYOG foray…

I like 9460pc over 9482pc solely because it has less initial tack. If you make a small mistake sometimes you can pull on the cuben to make it peel off and try again. The 9482pc will occasionally cause the mylar to delaminate in that situation. They are both strong enough once set.

Ryan

Nice design. That basic design is tough to improve on for a basic, 2 straight pole shelter.

I'm also into parametric modeling ( doing it for about 20 years)and have created a few different tent models. I use Catia V5. I'm just trying to decide which to build first. I REALLY love how the models can be modified by a dimension or 2 and easily updated, provided they were designed correctly of course. :)

Good luck!
Rob

Thanks, Rob. Very true about this design. Mine differs only slightly from some of the shelters available from various manufacturers.

For one reason or another, none of the offerings checked all the boxes for me, so I set out to design something that cobbles together all the features I like about those other shelters.

I do the same thing with my models (make them easy to modify), and I too have quite a few designs I've been playing with. :)

Well, I'm moving slowly along on this project. I'm going for the "hybrid double wall" design where the roof portion is single walled.

I still have one thing I can't figure out: How should I attach the top edge of bug netting to the fly? I can't think of a way to bond that seam such that it will be in shear. I'm not sure it's possible to avoid a bond that is in peel, which is making me lean toward a full double wall shelter.

I'd really rather go the hybrid double wall route, but I can't figure out a solution for that joint. Would the joint be strong enough even though it is in peel? Any ideas for how to make this attachment? Should I just go for a full double wall?

This detail, and the apparent cost of this project, is making me second guess whether I should buy a shelter instead. It's looking like it will cost me upwards of $600 to make this the way I want to, and for that price I could buy just about any solo shelter on the market. I love making my own gear, but I need to be realistic about my abilities and expectations. Somebody help me decide!! :)

Hi Erik

Sorry – lost track of this thread.

No, I haven't tried SW2015. Lack of time …

> What does NP stand for?
Non-Polynomial. Means that we do not have any theroretical solutions, and computed solutions will take an exhorbitant amount of time. Search on 'travelling salesman problem' for a well-known example.

Cheers