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-   -   My Bridge Hammock System - Part 2 (https://www.hammockforums.net/forum/showthread.php?t=2538)

 TeeDee 12-08-2007 15:30

My Bridge Hammock System - Part 2

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At a length of approximately 100", tie the other end of the ridge line to another 1/2" ID steel ring and secure to the loop at the other end of the hammock with another larks head.

After you have hung your new Bridge Hammock, you can vary the length of the ridge line to find the length most suitable for you.

Note that I have detailed a method using 1/2" ID steel rings. You could also use a single quick link on each end:

http://www.hammockforums.net/gallery...2/6/100180.jpg

Secure each end of the ridge line to a quick link with a round turn and 2 half hitches. The quick link may then be hooked into the loops and the link closed.

I choose to use the 1/2" ID steel rings for two reasons:
1. All of the quick links at the local Lowes had some sharp edges

which I decided it was better not to expose to my Bridge Hammock. The 1/2" ID steel rings have no sharp edges whatsoever.
2. The smallest quick links in stock at the time I was looking for

them are 1/8" and rated at 220 lbs Working load limit, which is plenty for the ridge line. They weigh 0.85 oz for 3 or an average of 0.28 oz each for an average weight of 0.56 oz for the 2 needed for the ridge line.
3. The 1/2" ID steel rings weigh 0.65 oz for 11 or an average of 0.06

oz each for an average weight of 0.25 oz for the 4 needed for the ridge end. Less than half the weight of the 1/8" quick links. The 1/2" steel rings from McMaster-Carr do not have a strength rating, so you have been warned and use at your own risk, but I have not had any problems with the rings when used in the ridge line.

Some last notes on ridge line.

I have found for myself and my wife, that a ridge line length that gives a distance from a head end accessory ring to a foot end accessory ring on the same side when the hammock is occupied, equal to or nearly equal to the length of the hammock fabric down the middle line, gives the most comfortable lie. Most comfortable for us means that our shoulders, hips and feet are nearly on a straight line when lying on our backs. That also means the distance from accessory ring to accessory ring on our hammocks is very close to 80". I didn't know this until one day I measured the distance.

After thinking about it for a little while it makes sense to me - that means that the middle line down the bottom of the hammock, when I'm in the hammock, is stretched out flat. Any other accessory ring to accessory ring distance means that the fabric bottom is curved to a greater or lesser degree since the arc will be lower or higher in the middle.

The curve can be with the middle lower, banana style, or higher, inverted banana style depending on the ring distance.

Banana style if the ring distance is shorter than the fabric length, since this lowers the webbing and the middle of the arc.

Inverted banana style if the ring distance is longer than the fabric length, since this pulls the arc out flatter, raising the middle of the arc.

I have installed a little plastic bubble line level on my ridge line. I can check the bubble when hanging to ensure that the ridge line is level. I find that I am more comfortable when the ridge line is level. Since my foot end spreader bar is shorter than the head end spreader bar, this means that my feet are lower than my head when compared to a level line, e.g., the ridge line. However, I have not noticed any tendency to slide toward the foot end of the hammock because of this.

The next item to make for the Bridge Hammock are the spreader bars.

for testing & car camping

For spreader bars you can use poplar dowels from Lowes. Get 2 48" x 7/8" dowels. The dowels will be used as spreader bars when you hang the hammock at home or when car camping. They are easy to use as spreader bars, are plenty strong enough and fairly light. The head end poplar dowel, with 1/2" poplar dowel inserts weighs 8.7 oz. I wouldn't use it backpacking, but for car camping, canoe/kayak camping and maybe bike touring, it is okay.

For backpacking, you can use your hiking poles, if you use hiking poles. If you don't use hiking poles or use a kind very different from mine, then you will have to work with Grizz to see if his method can be used with your poles.

Te get started quickly and for investigating the length of spreader bars that are suitable for you, the poplar dowels are excellent.

length and stability

If you are going to test various spreader bar lengths with the dowels, hopefully you installed the 1.25" ID stainless steel rings previously. Also, you will need the 3/4" CPVC "T" fitting that fits on the end of the 7/8" diameter poplar dowel. The fitting is available at Lowes or Home Depot in the plumbing dept. Or most plumbing supply stores should have them in stock. You will need 2.

You will also need 1 48" x 1/2" poplar dowel. This dowel may also be used for modifying your hiking poles for spreader bars as I will detail later.

In one end of each 7/8" diameter dowel drill a 1/2" diameter hole along the dowel axis. You needn't be concerned about being ultra accurate. Drill the hole approximately 1" deep. Now cut 2 2" pieces of the 1/2 dowel and insert into the holes.

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After hanging the Bridge Hammock, insert the protruding 1/2" dowel into the 3/4" ID ring. The opposite end of the 7/8" dowel slides through the 1.25" ID ring on the opposite corner of the same end of the hammock. Push the 3/4" "T" fitting on the end of the dowel after sliding through the 1.25" ID ring. Thread the "extra" length of the suspension triangle rope through the top of the "T" and tie back to the 1.25" ID ring using a round turn and 2 half hitches. The length of the spread bar can now be easily varied simply by varying the length of rope looping through the "T" fitting.

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In my experiments with spreader bar lengths, I found that for my hammock, a shorter spreader bar gave a more stable hammock and conversely, longer spreader bars yielded a less stable hammock.

By stable, I mean side to side stability. When you sit up in the hammock, you raise the center of gravity. If the center of gravity gets close to or above the level of the spreader bars, then the hammock is unstable and you have a balancing act keeping upright. The hammock tends to be tipsy side to side. The higher the center of gravity is, the harder the balancing act. Get the center of gravity really high and above the spreader bars and you will find that you will be having great difficulty keeping from tipping to one side or the other and will likely find yourself on the ground. I would not recommend trying to stand up in a Bridge Hammock.

An analogy (remember no analogy is really good): tie a rope between two vertical supports so that the rope is somewhat tight. Now take a broom stick or something similar and a short length of cord. Attach the broom stick to the rope using the cord. With the broom stick completely below the rope, it is very stable. If moved it will return to the same position below the rope. Now move the broom stick so that 50% of the stick is above the rope and 50% below the rope. This is called a neutrally stable position. Move the broom stick and it will remain in that position. Move the broom stick again so that more than 50% is above the rope. This is an unstable position. The larger portion of the broom stick will swing down below the rope. As you move more and more of the broom stick above the rope, the more unstable it is above the rope.

Laying down in the Bridge Hammock, you are like that broom stick hung below the rope. Very stable.

Sit up bringing the center of gravity closer to the spreader bars or even above the spreader bars, you are again like that broom stick above the rope. Not as unstable as the broom stick, but you have to keep slightly shifting your weight to keep things balanced.

Note that the only time you will have a stability problem is when you sit up with your legs in front of you. Getting into or out of the hammock is no problem. Also, you can sit crosswise in the Bridge Hammock with no problem.

With a longer spreader bar, especially on the head end, you raise the bottom of the hammock fabric, decreasing the distance to the spreader bar and hence increasing the height of the center of gravity bringing it closer to or above the spreader bar when you sit up.

So for spreader bar length you have conflicting problems:
1. longer spreader bar at head end to reduce or eliminate shoulder

squeeze, but decreasing stability, and
2. shorter spreader bar length to increase stability, but increasing

shoulder squeeze.

For my hammock a length greater than about 42" leads to more instability of the hammock than I was comfortable with when sitting up. Also, I found that by keeping the foot end spreader bar shorter, on the order of 80 cm, approximately 32", helped the stability. Since wider is not needed for the feet, I would recommend keeping the foot end spreader bar as short as is comfortable and shorter than the head end spreader bar.

I would not recommend exceeding 107 cm, approximately 42", for the head end spreader bar.

I did not arrive at this in a real scientific manner. It is just my observation from experience with both my wife's and my Bridge Hammocks.

After you have decided on the length of spreader bar at the head and foot end of the hammock, you can cut the 7/8" dowel to the desired length, drill another 1/2" hole on the newly cut end and insert another 2" length of 1/2" poplar dowel. Then replace the 1.25" ID ring with a 3/4" ID ring.

compression forces

I have included a derivation of the compression forces on the spreader bars at the end of this article for those interested in the details. Also, I have included an "Awk Programming Language" computer program for computing the compression forces. The program also, computes the parabola needed for the end panel of the draft stoppers and the bug netting. Those who desire to do so, may change the dimensions specified to match their own Bridge Hammock and compute both the compression forces and the needed parabola.

I will describe here the use of my hiking poles for spreader bars. This section may be skipped until later when you may need to use your hiking poles as spreader bars.

The first thing to remember about spreader bars is that you want to align the compression forces along the axis of the spreader bar as much as possible. This is true for any spreader bar, not just hiking pole spreader bars. Any off-axis component of the compression force will force the spreader bar to bend. The more off-axis the force, the more bending will be experienced. This will cause you to compensate by using stronger and heavier spreader bars than necessary. Also, you may have to forego using your hiking poles if the compression force is too much off-axis or risk damaging your pole(s).

To this end I worked very hard to keep the compression force as close to the axis of the spreader bar as possible. Following my K.I.S.S. principle, I found that the use of the rings for securing the spreader bar to be the simplest and the most effective method I could devise.

The rings are so successful in aligning the compression force along the axis, that I can detect no bending of my hiking poles whatsoever no matter how much I bounce around in my Bridge Hammock.

pole tip and top

I use the Stoney Point Explorer hiking poles. One with the V-yolk top and one with the binocular rest top. The tops can be unscrewed revealing a 1/4" x 20 camera mount stud.

With the 3/4" ID rings installed for securing the spreader bars/hiking poles, two simple devices are needed to use the rings:
1. a simple AL cylinder, solid, 4 cm long. The end of the cylinder

is drilled along the axis on one end and tapped for a 1/4" x 20 screw approximately 1/2" long. Super accuracy in aligning the hole with the cylinder axis is not necessary. 2 are needed. The AL cylinder is screwed onto the 1/4" x 20 camera mount screw on the top of the hiking pole and inserted into a corner 3/4" bar ring. This secures the top of the hiking pole to a spreader bar ring. A hole is drilled across the diameter of the AL cylinder, a short piece of guy line cord is threaded through the hole and looped over the line connecting the two corner rings and tied. The AL cylinder is thus secured to the appropriate corner of the hammock, cannot be lost and is always immediately available to use with the hiking pole as spreader bar.

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2. A cap for the carbide tip of the hiking pole. The cap is made

with an electrical wire nut of the appropriate size to fit over the carbide tip of the hiking pole. I tried several covers for the carbide tip and was never satisfied with any of them. Then one day, I made a special purpose trip to Lowes with a hiking pole. Searched the store and was about to leave, when I decided to try the electrical dept. Spotted the electrical wire nuts and the light bulb went on. I wondered why I hadn't tried them before since I have several boxes of various sizes in my garage. A fender washer is then fit over the end of the wire nut so that the end of the wire nut protrudes past the fender washer and the fender washer rests on the "wings" of the wire nut. The end of the wire nut is then inserted into the other spreader bar ring. As was done for the AL cylinder, a hole is drilled through the top of the wire nut, a short length of guy line cord is threaded through the hole and the wire nut and fender washer are secured to the hammock. The guy line cord also serves to secure the fender washer to the wire nut. Simple and very, very light.

http://www.hammockforums.net/gallery...2/6/100230.jpg

A simple and very effective means for using the hiking poles as spreader bars.

limiting hiking pole collapse

One additional modification is necessary for the hiking poles. The locking mechanism may not hold the spreader bar length you want or you may just desire to relieve the strain on the locking mechanism when using the poles as spreader bars.

This modification is simple and consists of inserting poplar dowels of the proper diameter inside the hiking pole sections. The dowels act as stoppers keeping the poles from collapsing any further.

I used one 7 7/8" length of 5/8" diameter poplar dowel in the top section of the hiking pole used for my foot end spreader. It added 0.65 oz to the weight of the hiking pole.

For the pole used as my head end spreader bar, I used a 13.5" length of 5/8" diameter poplar dowel in the top section of my other hiking pole and a 3.25" length of 1/2" diameter poplar dowel in the middle section. Both dowels sections added 1.35 oz to the weight of the hiking pole. In using the poles for walking, I cannot tell any difference in weight.

With the dowel sections added to the poles, both poles, fully collapsed against the dowel stops, are still shorter than I use them for walking.

To use for my Bridge Hammock, I simply loosen and fully collapse against the dowels stops and re-tighten slightly. To use for walking the next morning, I simply extend to my normal walking length for each. It takes about 2 seconds to collapse the poles and about 10 seconds to extend to my desired length.

A picture of my hiking poles extended for use in walking:

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The poplar dowels have the added benefit of strengthening the hiking poles not only for use as spreader bars, but for their use as hiking poles.

Since the only force on the dowels as stoppers in the poles is compressive, poplar is more than strong enough and stronger, denser hardwoods are not necessary. Stronger, denser hardwoods would only be heavier.

Late Addition for the UL and SUL person

Since part 1 is already uploaded for the moderators to review, I am adding this here - in part 2.

Today, 12-08-2007, I have found another way that may work for some instead of the bar rings and accessory rings used above.

Instead of using the bar rings, you may save the weight of the 4 bar rings, replacing them with the 2.8 mm Spyderline. The Spyderline will weigh slightly under 0.3 oz as opposed to the 1.70 oz of the bar rings, saving a little over 1.40 oz.

For this method, connect the Spyderline suspension lines to the accessory rings in the same manner as described previously for the bar rings. Extend the length of each side of the suspension triangle approximately 13 mm, 1/2", to compensate for the absence of the bar rings.

Then use an 11" length of the 2.8 mm Spyderline. Tie this piece to the suspension at an accessory ring using a round turn and 2 half hitches. Pull very tight. Then tie the other end to the suspension line right next to the first knot, again using a round turn and 2 half hitches. This forms a small loop on the suspension line. Adjust the size of the loop such that the 1/2" AL cylinder on the hiking pole, or the 1/2" dowel or the electrical wire nut fits tightly into the loop. Pull the second knot tight.

Repeat on the other 3 accessory rings.

The dowel spreader bars or hiking poles may now be used with the loops instead of the bar rings.

The 2.8 mm Spydrline still carries the full load of the hammock and occupant and since it has not been cut or a knot tied in it for the spreader bars, it's strength has not been reduced.

This method saves some weight for those who are very consciously attempting to do so.

It has one disadvantage when compared to the rings: If spreader bars have to be scrounged locally from tree branches, it will be harder to keep the ends of the branch spreader bars from slipping though the loops. Maybe not impossible, but much harder. The steel rings hold the tapered ends of branch spreader bars much more securely.

Also, the branch spreaders will abrade the Spyderline loops, introducing a possible failure point.

The accessory rings could also be replaced by simple bowline loops. The bowline loops will be harder to work with than the steel rings, but not impossibly so. To use the bowline knots you will still bar tack loops on the webbing ends, just without the steel rings.

The use of the bowline knots will also introduce a problem that I used the steel rings to alleviate. The steel rings transmit the forces from the webbing to the suspension rope without the abrasion of the small diameter suspension on the webbing. This abrasion can and will wear through the webbing and cause an eventual failure. I do not at this time know how long it would take for the suspension line to abrade through the webbing, but if the reports I have seen of a suspension line cutting through tree huggers are any indication, it may be a matter of only a few days.

So if you do replace the steel rings with bowline knots, inspect the webbing loops very carefully before each time you hang your Bridge Hammock.

By replacing the bar rings and the accessory rings, you could reduce the weight by approximately 3.20 oz. This weight savings may be important for some or maybe not.

hanging the Bridge Hammock

Part 8 of this article now details my current method for hanging and storing my Bridge Hammock System.

getting into the Bridge Hammock

I originally included this section just to be complete, but have decided that the section is really not necessary.

You get into the Bridge Hammock like any top loading hammock. Sit down in the hammock at the middle. As you lay down, rotate and swing your legs into the hammock.

determine desired ridge line length

If you would like to test various ridge line lengths, do so at this time. Simply loosen the hammock suspension enough that a ridge line end can be separated from the end loop. Un-tie the knot, shorten or lengthen the ridge line as desired, retie the knot, re-attach to the end loop and tighten the suspension.

You may want to experiment with various ridge line lengths to determine the length most comfortable for you.

If you have installed the 1.25" ID bar rings and "T" fittings, you may want to test various spreader bar lengths at this time to determine the lengths most comfortable for you. After determining the desired lengths, change the 1.25" ID bar rings for the 3/4" ID bar rings.

Taking down the Bridge Hammock

Part 8 of this article details the new and current method for hanging, taking down and storing my Bridge Hammock System. The new method eliminates the tangling of the suspension and ridge lines so that is no longer a problem. Also, the new method is simpler and quicker, eliminating the necessity for securing the bundled suspension and ridge lines. The new method eliminates the two section snake skin, replacing it with a single, constant diameter tube that is even easier to make and use.

I have left this section in the article for archival purposes and for those who decide that the old method better suits their style.

One of the problems I have experienced with the Bridge Hammock is tangling of the suspension triangle lines and the ridge line when the hammock is not hung. I have developed a method for avoiding this problem which incorporates Prussic loops with micro-carabiners on the ridge line and the "extra" length of suspension line left on two of the bar rings.

The method is illustrated as well as I could in the following pictures.

Before describing the method for securing the suspension triangle and ridge lines, I will describe the Bridge Hammock snake skins I use since they are a part of the system I use.

I made special snake skins for our Bridge Hammocks. I experimented with a Black Bishop bag since so many people like those. I have gone back to the snake skins. Since I do not store top or under quilts in the stuff sack with the hammock, the BB sack had no advantages for me and the skins had the advantage that the hammock is fully enclosed while I take it down and put it up. If anything gets dirty from ground contact, it is then the silnyl snake skins which is no problem. I do store the draft stoppers and bug netting or overcover in the skins since if those happen to get wet, like the hammock itself, they dry very quickly. Just shake and the water is gone.

For those who want to use stuff sacks instead of snake skins, keep reading. At the end of this section, I describe a new method I have developed as of 12/06/2007 that enables one to use stuff sacks instead of snake skins.

The Bridge Hammock snake skins have two parts:
1. a small diameter part for covering the suspension triangle line

and which keeps the suspension and ridge line from getting tangled.
2. A large diameter part for the hammock body. Since the Bridge
hammock doesn't taper from narrow ends to wider in the middle, a normal tapered snake skin doesn't work. A simple constant diameter tube works better. Actually, with draft stoppers, the ends of the Bridge Hammock are bulkier than the middle.

Since the diameter is constant, the Bridge Hammock snake skins are actually easier to make than regular snake skins. The two parts are made in one skin using the following pattern:

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The dimensions specified are those used for our Bridge Hammocks. A 1" seam allowance has been added on the sides. Thus, the final tubes will have a 10" circumference for the larger tube, narrowing down to a 3" circumference. The 2 skins needed for each hammock are simply cut from a full width 1.1 oz silnyl fabric and the reduced diameter is then cut on one end. Super simple and easy.

I borrowed an idea from somebody on the forums and simply used 1" polyester webbing for the open ends. Easier than cable ties, but slightly heavier.

The skins are then threaded over the suspension lines and butted up against the outside of the suspension rings. The narrow tube on the skins slides easily over the 3/4" ID rings. This is necessary since the skins rest outside of the suspension rings when the hammock is hung. It is not practical to keep the skins on the inside of the rings due to the spread of the triangular suspension lines.

The method is illustrated in the following pictures:
1. You start by removing the spreader bars and sliding the Prussic
for any overcover or bug netting slightly towards the center of the hammock. Alternatively, you could unclip from the Prussic and let any overcover or bug netting drop into the hammock proper.
2. Then clip the suspension triangle lines into a micro-carabiner on

a Prussic loop on the end of the ridge line.

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3. Now thread the "extra" suspension line hanging from one bar ring

through the opposite bar ring next to it.

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4. Then thread the line up through the suspension ring and back

through both bar rings.

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5. Now pull the line so that the suspension lines are pulled against

the micro-carabiner and position the micro-carabiner to that the bar rings are next to the ridge line.

http://www.hammockforums.net/gallery...2/6/100320.jpg
6. Tie a temporary half hitch to hold things in place and repeat on

the other end of the hammock.
7. Adjust both ends so that approximately the same amount of distance
separates the suspension ring and the micro-carabiner on both ends. With practice you will soon learn the approximate distance to use.

When you have the distances approximately equalized, pull each end tight so that the suspension lines are pulled up tight against the ridge line and the hammock webbing is pulled up tight against the ridge line.

Secure each end with 2 half hitches.

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Now pull the Bridge Hammock snake skins to cover both the suspension triangle and ridge lines and the hammock proper.

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Repeat on the other end.

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The suspension and ridge lines and hammock are now secured.

I have found that this method for securing the lines and storing the hammock takes about the same amount of time it takes to roll the HH ULBA and pull the skins. Since the Bridge Hammock has far less material and doesn't have to be rolled on the bias as the HH ULBA does and doesn't trap air like the HH ULBA when rolled, rolling and pulling the skins is far faster for the Bridge. When combined with securing the lines, the total time is about equal.

Once the hammock is secured in the snake skins, I take it down, fold into a small bundle and wrap the suspension lines around the bundle to secure. This gives me a bundle approximately 10"x5"x4". It is considerably smaller than my HH ULBA in skins and bundled in the same manner.

I have found another method for securing the suspension lines to the ridge line and preventing tangles when taking the Bridge Hammock down. This method will work for those who like stuff sacks better than snake skins. You will need "curly Laces". I picked up a pair at WalMart last year. Thought they would be good for something and here it is.

After you have secured the suspension lines to the ridge line as described above, wrap the curly laces around the lines:

Part 3

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