Has anyone done anything similar? What should I be careful of when starting this project. ]]>

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New member, i have been into hammock camping for a few years now i own a henessey hammock, but have decided id like to try building my own hammock.

my question is does anyone know any places in australia that sell ripstop material same as what ripstop by the roll does ?

Thanks Paul ]]>

I got the opportunity to make some snake skins to fit a hammock set up and wanted to share how I did it in case anyone is interested in making their own. I got the initial dimensions from an older thread( from earlier this year), so thanks HF.

I used:

-4yds noseum mesh from Dutchware (0.9), They were out of 0.67 when I ordered which is what I would suggest for these.

-Shock cord

-mini cord locks also from Dutchware

-grosgrain ribbon(not sure of name) for the ends, this looks exactly like the material hammock gear uses for the channels on their under quilts. I find it works better to synch against than regular grossgrain.

I cut each of the 4 pieces 15" x 6' to work with 12' hammocks, then I rolled and hemmed each side.

You can definitely put a tapper in each of the halves to make the side pointing at the tree more narrow but I didn't do that this time.

After this I used the t shirt cuff thing on my walmart sewing machine and installed the grossgrain ribbon and shock cord. I finished each end off with a mini cord lock.

They turned out just like a giant set of tarp snake skins.

Just for reference in the picture I have a 40UQ and 20TQ full of downy goodness from hammock gear in the tube halves.

Hope you all are having a great holiday weekend and have your hammock set up somewhere nice.

Two Speed

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I have a SLD assym uqp and kinda like the fabric used (Argon 90 in my case) so I'm looking for something similar that I can get from extremtextil or another source in the EU. ]]>

I made two cords with the easiest knot I could think of to wrap fabric together and that could be easily loosened, which resulted in two long cords with hangmans knot in one end.

I then tried all kinds of items to make my gear sling from. They all worked just fine. Plain old plastic bag could easily hold the weight it needed to. I even made a sling out of my backpack and even that worked, it would roll over, but in a pinch it's better than nothing.

Easy, fast, free if you have cord laying around, can have multiple uses etc..

Weight of the cords: 10 grams

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Here is an idea you might try for a pretty good low-budget underquilt. My brother took an old Big Agnes Lost Dog sleeping bag and without any modification, turned it into a decent underquilt.

I am not sure about the newer Lost Dog design but this old one was made with straps on the bottom instead of a full pocket for a sleeping pad or air mattress. You can see he used these straps to attach the sleeping bag to his ridge line. He also added tie-outs to each end of the sleeping bag to be able to pull it up for the proper comfort level. Pretty ingenious I would say...

Is it a safe way to do it, I tried the 3 stitches way and the warbonnet style too but I never tried this method...

https://m.youtube.com/watch?v=AJlEQpcbM1I ]]>

This is a remake of an earlier thread, incorporating some important new information and feedback from the community. If you read the previous post, some of this information is repeated from there, but do stick around:

1. Basic Shape

Most baffles are designed and cut with a shape like this in mind:

badbaffle.png

That is, that they are rectangles capped with semicircles or arbitrary circular arcs, the exact shape of which left up to the designer. This shape ends up being pretty close to reality, depending on your goals, but it is not quite right. I'll explain the shape that is a closer fit in a moment, but in order to do so I must explain to you a very specific subset of baffle shapes, and that is the shapes that come about when the baffles are fully filled with down. Or, if you prefer, you can skip right to 1c.

1a. A Fully Filled Baffle

I know what you are thinking:

To be more specific, what happens is that the baffle expands until it encloses the largest volume possible for the amount of fabric provided. Once it reaches this shape, the baffle cannot move anymore, so the down starts compressing. That means that, in a very important sense, the shape the baffle reaches before the down starts compressing is the shape of a fully filled baffle — and any other shape is an

So what is this mysterious fully-filled baffle shape? It is what I like to call a truncated circle.

1b. The Truncated Circle

I'm sure we all remember from grade school that the shape that encloses the most area for a given perimeter is a circle. Baffles are a little more complicated, as they have a pair of straight walls on either end (provided the baffles are equally filled). Fortunately, getting from a circle to our baffle shape is pretty easy: just cut off the ends. If anyone is curious about the proof of this, ask in the comments below, but for the sake of expedience I'll just use the graphic below to explain what I mean:

bafflewh.png

Exactly how much of the end you cut off is up to you, and depends on a number of factors addressed in later sections. There are two benefits to this shape, that go hand in hand: the shape is completely dimensionally stable, meaning that your quilt is more likely to come out the size you designed; and the down is stable, meaning it won't shift at all unless you really try, and even then it will return to normal over time. Unfortunately, this shape comes with a serious disadvantage: weight. Nobody really wants a quilt with baffles thinner than they are deep. A quilt like this will typically use 3x more baffle wall material than a normal quilt! Nobody really wants that. So what is one to do? Well, there are two solutions here, the normal solution and the clever solution. But we'll get more into that in Section 2. Before we do, we need to talk about the broader category of baffle shapes:

1c. Truncated Ellipses (Normal Baffles)

Look, we don't need down shifting to be zero. We just want it to be low enough that performance isn't impacted. So, we want an underfilled baffle, just not

ellipsebaffle.PNG

Like the truncated circle, you just cut the ends off an ellipse — again, how much you cut off is up to you. Now, in the real world, it will never be precisely this shape; things like gravity will distort it since the underfilled down is not able to provide as much resistance. But it is as close as you can get. To be honest, this shape is pretty close to the "capped rectangle" shape people tend to use — usually it's within a few percent. But that few percent is part of the reason that quilts tend to come out with slightly different dimensions than the maker intended. Using this truncated ellipse should help with that (though we are all human, so it'll never be

Now, one thing there isn't much point in doing with these baffles is "overfilling" them. Since they are not completely filled to begin with, all overfill accomplishes is changing the shape so that it is more circular. Now, there is nothing wrong with changing the shape like that, and it will cut down on down shifting, as you intend. But if you are going to do that, use a different shape to begin with! Keep the perimeter of your baffle shape the same, but make it slightly taller and slightly less wide overall. That way it comes out the dimensions you expected, instead of the overfill throwing off your measurements.

2. Shapes and Performance

Before I get into designing baffles for quilts, I need to clear up some points on how heat works, and how baffle shape affects performance. There are some pretty major misconceptions here, and it is important to clear them up before continuing.

2a. Major Misconception

People tend to use the amount of of down in a baffle of a given width as a proxy for how warm the baffle is. For example, take two baffles: one is a circular baffle, in a sewn-through construction. Since this baffle is a perfect circle, the width and (center-of-baffle) height are equal. For our sake, lets say that they are both equal to two inches. Now, compare that to a perfectly rectangular baffle. We'll keep the width of our rectangle the same as the circle, so 2 inches. But we'll make the height 2π inches, so that both shapes hold the same amount of down. This also means that both shapes have the same average height. Now, since the edges of the circle are so thin, those will be cold spots on the quilt. But on the other hand, the center of the circle is taller than the rectangle, so it will be warmer in the middle. Sure, the circle baffle would be less comfortable, but both would allow the same overall amount of heat to escape, right? Wrong. Heat is lazy, and will escape though the easiest route. That means that the edges of the circle allow more heat through, and makes the rectangular baffle 19% warmer overall! Before I get too much into the maths, there are two key points I want to cover.

- The more rectangular the shape, the warmer the baffle is relative to a curved baffle containing an equal amount of down. The trade-off is that rectangular baffles experience the most down shifting.

-The relationship between warmth and how rectangular or curved the baffle is is not linear, but inverse. Moving from a sewn-through baffle to really short baffle walls — even as small as 1/8 of the center-of-baffle height — has a huge impact on performance. But as that baffle wall height gets closer to the center of baffle height, there are rapidly diminishing returns.

2b. The Maths

Things get pretty dense here. If you believe me and have no interest in how it works out, feel free to skip to the next section. Otherwise, stick around for some fun! This is also a complete copy/paste from my previous thread, so skip ahead if you already read that one as well.

For those that remain: you are such a nerd! Anyway, some background on how thermal performance is measured. As consumers of quilts, usually all a manufacturer tells us is the "temperature rating", which is somewhat arbitrary. Where I most commonly encounter actual units expressing thermal resistance is home insulation, for which R-values are typically provided. This is also typical in sleeping pads. Since they are what I am most familiar with, I will use R-values throughout this post. Here is the US, R-values are expressed in (h*°F*ft2)/BTU, and are often provided per inch of material depth. The numbers themselves don't have much intuitive meaning, but they are easy to compare. Something that is R8 blocks twice as much heat as something that is R4, and if you put two R4 rectangles on top of each other you get an R8 rectangle. Using the National Institute of Standards and Technology Heat Transmission Properties of Insulating and Building Materials Database, I was able to determine that duck down has an R-value of approximately 3.93 per inch of down (note: this seems a little low to me; if anyone has better numbers I'm happy to take them).

To find the mean R-value for some assemblage of material, one needs to take the mean of the R-values weighted by there areas. But not the geometric mean, which is the kind of mean that we are used to (and would make the previously mentioned rectangular and sewn-through baffles equivalent). Since R-values represent a rate, we need to take the harmonic mean weighted by the areas instead, which is the inverse of the sum of the inverse R-values.

While the harmonic mean works great for discrete shapes, our baffles are curved. That isn't a problem though, all we need to do is take sum up the R-values from arbitrarily small slivers from under the curve to find an approximate area... wait a second, that's the definition of the antiderivative! That's right baby, it's calculus time, and we're breaking out the integral! I bet this isn't where you were expecting this to go. Don't run away yet though: I know not everyone is as excited about math as I am, but the good news is that we get a pretty simple equation at the end.

Since we are dealing with circles, the maths are actually pretty easy. The equation for a semicircle in the plane centered at 0,0 is:

CodeCogsEqn.gif

For our baffles, we can determine the R-value by multiplying that equation by our R-value per inch value (3.93), doubling it (as we have a full circle instead of a semicircle), inverting it, taking the antiderivative over the length of our baffle, dividing by the length of the baffle, and then inverting again. Using our w and h values, we get the integral:

CodeCogsEqn(1).gif

Thankfully, that works out to be equivalent to the much simpler

CodeCogsEqn(3).gif

Now we can use this equation we can use to determine the performance of our baffles. Plugging in w=h=2 for our sewn through baffle, we get that the R value is almost exactly 5, compared to the rectangle which would have an R value of 3.93*π/2, or about 6.2. That's where we get the 19% difference in performance! Of course reality would never work out quite so precisely, as even the fabric has enough of an R-value to cut that percentage to 15% or so. Even considering that, that is enough of a difference that a blanket with smaller box baffles can match the performance using less fabric and down, and thus being lighter than the stitch-through baffle (still more time consuming though).

3. Designing Baffles

Now that we covered the basic shape of baffles, I can talk about how to design them for use in your quilt. I'll start with normal baffle design, before getting into my clever solution I'm sure you are all waiting for.

3a. Normal Baffles

We talked before about wanting to keep down shifting to reasonable levels, if not exactly zero. That means we don't want our shape to be

I'd like to say there is a right answer here, but there is not. We can measure the amount of down shifting by the percentage underfilled the shape is relative to the truncated circle with the same perimeter (there is a little trigonometry, but its not that hard). And we can measure how warm the baffle is. But exactly how warm it needs to be, how much down shifting is acceptable, and how light the quilt must be will vary by person. Most people should just follow the rules of thumb that people generally follow for baffle wall heights and baffle widths and whatnot, just with a slightly different shape. Now, if you use those rules of thumb you can fix some variables, and then you can do some very mathematical optimization if you want (see Part II), but you need to make those somewhat arbitrary choices first. This is not the case in my clever solution though.

And again, as a quick reminder, there is not much point in overfill when using these shapes.

3b. Clever Baffles

Alright, you stuck with the post so far, so here is the really game changing stuff. A quick reminder though: this is still just theory, and I hope to build a demonstration quilt using the baffle outlined here later this month.

Let us go back to our truncated circle shape. The problem with that shape is that the baffle walls weigh too much. But what if there was a way to reduce the baffle wall weight? A way that you cannot use on underfilled shapes? Lucky for us, there is. Let us look at the functions of a baffle wall. In general, it serves two functions:

-To hold the shell material in place, so that you... have baffles.

-To prevent the down from shifting between the baffles.

Here is the key insight:

First, the why. With a typical, underfilled baffle, down shifting is a fact of life. Since the shape isn't completely filled, the down offers no resistance. Imagine if you have two baffles, side by side, both about 80% full relative to a truncated circle. Also imagine that the baffle wall material, whatever it is, allows down to pass through it easily. Now, if you grab the baffle from the side and give it a shake, it is easy enough to make it so that one baffle that is 100% full, while the other is 60% full. With time and effort, you can shift the down back so that they are both approximately equal again, though without a scale you'll never get it exactly right. Even if the spread becomes 75% in one and 85% in the other, that is a pretty major difference in both shape and performance, and entirely likely to happen when in use. This tells us it is important that elliptical baffles need baffle walls that not allow down to pass through.

On the other hand, if both baffles are at 100%, they want to stay that way. It is possible to

One thing we can do is take our regular baffle material, like noseeum netting, and cut some pretty big holes in it. How big, and what kind of holes? The exact limits are anyone's guess, but I think it will be very easy to make them 4x lighter, or even more. Imagine taking the baffle wall material, and punching a bunch of circles in it, about as tall as the baffle wall itself is, like so:

perfbafflewall.PNG

This already reduces the material weight by about a factor of 4, and that is significant. Remember when I said that these truncated circle shapes use about 3x as much baffle wall material as traditional baffles?

Another neat fact about this baffle: unlike the elliptical baffle, which has a few "rule of thumb" aspects, this baffle is easy to optimize! The only factor you need to choose is the center-of-baffle height, and the rest follows from your material choices! For more information, see Part II

Of course, theory is one thing. Reality is another. Like I said, I'll be constructing a quilt using this theory later this month. I'll let you all know how it goes.

4. Conclusion

Thanks for reading my thoughts on baffle shape. I hope you all view it as as significant improvement on my first attempt. Again, see Part II for more on baffle optimization. And before you ask about differential baffles, that will be the subject of Part III, which will be posted in a week or so. Here is a quick teaser on shape:

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In case this is important: it's an underquilt, so it is important that the layers are somewhat even. Otherwise there will be cold spots. ]]>

I was after something cheap and cheerful and easy to make.

Then I had a thought. What an underquilt basically is is a fluffy hammock so I set about making just that.

My starting point was a 6ft by 4ft fleece blanket that I picked up in Aldi for about £5 ($7?)

It only needs to support its own weight so only basic whipped ends are needed, with 24" bungee loops also inside the whipping to make it the same length as my hammock.

Attach the bungee loops to the same carabiners as the hammock and job done. Less than 30 minutes work and I'm relaxing in it right now. It's changed my hammock from being slightly chilly to pleasantly warm.

Sent from my SM-J320FN using Tapatalk ]]>

I’ve been trying to find a LARGE tarp with doors That can house my motorcycle and gear while I travel internationally, but I’m rapidly realizing I don’t think one exists that meets my needs. The Cill Gorilla Fortress seems to be the closest thing I’ve found, but would like it a tiny bit bigger.

I’ve bought a Hennessy Deep Jungle XXL zip, and like it, but their tarp is way too small.

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I’m a product designer and I’ve got a sewing machine, but I thought I’d ask if anything else is out there? And if not, where can I buy, and what is the right fabric to use?

Thanks!

Overall, optimization is a simple process to understand. We need to pick a parameter and find even the minimum or the maximum for a given range of inputs. In our case, we are looking for the

The one limit I recommend on shapes is that they you limit yourselves to a "truncated" version of some shape. That is, instead of using a baffle shape of a rectangle with half an ellipse or oval on the top and bottom, you use a longer ellipse or oval with the ends cut off. This is a more accurate way to think of baffle shapes, and should provide you with better, more interesting results -- though it might take you a bit to get a feel for the shape. Of course, the capped rectangle shape is easy enough to optimize as well, should you so desire. My guide also assumes the shapes are centered at 0,0 on the Cartesian plane.

But first, a

Although the utility of the optimization process is pretty low, going through the process was pretty useful, and taught me a fair amount. After all, its not as if anyone knew beforehand exactly how much there was to be gained or lost before I started deriving this stuff (at least, not that I could find). Just determining that made this undertaking useful.

1. Parameters

Before we craft our equations, it is necessary to settle on what parameters we will be using for our equations. This will vary based on your choice of shape and personal preference. For our truncated circle shape, we will need only the radius (

2. Equations

To sort this out, we are going to need a pretty intimidating-looking equation. But when you break it down into smaller pieces, it is actually pretty straightforward. The pieces are as follows:

2a. Equation for Box Baffle Shell Weight

For this, we need to find the perimeter of our shape (excluding the baffle walls) and multiply it by the fabric weight. For the truncated circle, this is easy. The perimeter is calculated using the equation for arc length. I'll jump straight to the good stuff.

Note that we divide the shell weight by 1296 to put it in oz/in

2b. Equation for Box Baffle Wall Weight

For this, you only need the equation for your shape. Plug in length plugged in for x, and you'll have the amount of material, and from there you only need to multiply by the fabric weight. For our circle, it is:

We multiply by two in order to capture the half of the baffle wall below the x axis. We only need to account for one wall per baffle, because a baffle shares its walls with its neighbors.

2c. Equation for Fill Weight

For this, we need to determine the area of our shape, and divide by the fill power. This is where calculus starts to come into play. You'll need to determine the definite integral of your shape from -x to x — again, not forgetting any parts that fall beneath the x-axis. For a circle, we wind up with the final equation:

2d. Equation for R value

I explained how to derive this in my last post, so I won't rehash it here. It involves calculus and harmonic means.

As a side note, I suspect that the R-value I have for down is on the low side. Anyone have more accurate R, U, or k values for down?

2e. Final Equation

In order to determine the the R-Value per unit of weight, we need to combine all our previous equations together. Too keep things clean, I'll use the names of the equations instead of their actual values. The process is to divide the R-value for the baffle by the sum of the different weights. In order to make comparisons between baffles easier, we will also divide the baffle weights by the length, to get the weight per length. When you simplify, you wind up with this equation:

3. Optimizing

Alright, so now we can calculate the warmth-to-weight ratio of a given baffle. How do we go about determining the minimum possible value over a range of inputs? There are two ways to determine this. The first way is to do some calculus to determine local minimums and maximums. Now, I love math, but that is a bit much even for me. The second way is to make a computer do it for you, and, dear reader, this is what I did. I used Mathematica, since I know it well. You can use the cloud based version for free if you follow this link. Simply copy and paste the code below, then hit ctrl-enter:

Code:

`BoxBaffleShellWt[ShellWt_,r_,x_] := (4*ArcSin[x/r]*r)*(ShellWt/1296)`

BoxBaffleWallWt[BaffleWt_,r_,x_]:=(2*Sqrt[r^2-x^2])*(BaffleWt/1296)

BoxBaffleFillWt[FillPower_,r_,x_]:=(2*(Sqrt[r^2 - x^2]*x + r^2*ArcSin[x/r]))/FillPower

BoxBaffleR[r_,x_]:=(2*x*3.93)/(ArcSin[x/r])

BoxBaffleRatio[ShellWt_,BaffleWt_,FillPower_,r_,x_] := BoxBaffleR[r,x]/((BoxBaffleShellWt[ShellWt,r,x]+BoxBaffleWallWt[BaffleWt,r,x]+BoxBaffleFillWt[FillPower,r,x])/(2*x))

You can then plug the values into your R-value function to get the R-value of the baffle. Again, in our example, it would be BoxBaffleR[1.5,1.02918]. This is a little less elegant than inputting a target R-value and solving for baffle height, but unfortunately it would be difficult to set it up that way. Temperature rating is a pretty imprecise system, so there is not much point in converting R-values directly into temperature ratings. Center-of-baffle height (2*

4. Ellipses

Maybe I haven't sold people on circular baffles yet. You want oval shaped baffles, and I will oblige you. The equations you need are as follows:

Code:

`BoxBaffleShellWt[ShellWt_,A_,B_,x_] :=4*A*EllipticE[ArcSin[x/A],(A^2-B^2)/A^2]*(ShellWt/1296)`

BoxBaffleWallWt[BaffleWt_,A_,B_,x_]:=2*B*Sqrt[A^2-x^2]/A*(BaffleWt/1296)

BoxBaffleFillWt[FillPower_,A_,B_,x_]:=2*NIntegrate[B*Sqrt[A^2-y^2]/A,{y,-x,x}]/FillPower

BoxBaffleR[A_,B_,x_]:=(3.93*2*x)/NIntegrate[A/(B*Sqrt[A^2-y^2]),{y,-x,x}]

BoxBaffleRatio[ShellWt_,BaffleWt_,FillPower_,A_,B_,x_] := BoxBaffleR[A,B,x]/((BoxBaffleShellWt[ShellWt,A,B,x]+BoxBaffleWallWt[BaffleWt,A,B,x]+BoxBaffleFillWt[FillPower,A,B,x])/(2*x))

FindOptimumBaffle[ShellWt_,BaffleWt_,FillPower_,A_,B_] := NMaximize[BoxBaffleRatio[ShellWt,BaffleWt,FillPower,A,B,x],{x}∈Interval[{0,A}]]

A useful way for envisioning some of the tradoffs of increasingly long ovular baffles comes from looking at the problem another way: choosing a fixed baffle width (

Code:

`Plot[BoxBaffleRatio[0.885, 0.67, 750, A, 0.75,1.5],{A,1.5,6}, PlotRange->Full]`

And that finishes Part II of the series. Part III will be on differential baffles and underquilts, and I hope to put it out in the next week or two. Before that, I might post a revision of Part I, since my (continuing) research and input from the community has left me with a better understanding of the topic, and I believe I will be able to better relay the information in a form that people will be able to use in their own projects.

The roll is 500d waterproof cordura and ties on behind her saddle just like the traditional cowboy saddle roll. Velcro closure in the main part of the bag holding the hammock rig with another exterior compartment for the tarp with suspension packed in a snake skin.

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