# Thread: Cirrus, DIY bridge #3, (picture heavy)

1. Ber,
It split at the female part of the ferrel and split the entire length.

It was my own stupidity that caused it with a way too short suspension triangle. I think it would have lasted otherwise.

I believe a good way of estimating the center width is to (((header - footer)/2) + footer). Then you have to subtract the depth for the cat curve cuts.
42" - 30" = 36" minus cat curve depth
39" - 30" = 34.5" minus cat curve depth
36" - 36" = 36" minus cat curve depth

I have a narrow tarp so I was trying to keep the spreader bar width down, but I may think about doing a 42".

I wonder what happens if you make one without a cat curve cut on the sides? If you notice the entire length of the hammock (whoopie, triangles and hammock) form a cat curve when you are in it. I think the sides exagerate the cat curve when you in the hammock, so if you didn't cut a cat curve on the sides wouldn't you still get a cat curve due to your weight pulling in the edges. Hmmm something to think about a bit more.

2. Originally Posted by egrant5329
I wonder what happens if you make one without a cat curve cut on the sides? If you notice the entire length of the hammock (whoopie, triangles and hammock) form a cat curve when you are in it. I think the sides exagerate the cat curve when you in the hammock, so if you didn't cut a cat curve on the sides wouldn't you still get a cat curve due to your weight pulling in the edges. Hmmm something to think about a bit more.
I think you would lose some of the flatness, but I think Grizz or TeeDee or others more experienced than me would know better.

3. Originally Posted by egrant5329
Ber,
I believe a good way of estimating the center width is to (((header - footer)/2) + footer). Then you have to subtract the depth for the cat curve cuts.
42" - 30" = 36" minus cat curve depth
39" - 30" = 34.5" minus cat curve depth
36" - 36" = 36" minus cat curve depth
I always use (header+footer)/2. Works out to be the same. Comes from
thinking of the width as a linear function of the fraction of the length
of the hammock

where lambda=1 means you're at the head, lambda=0 means you're at
the foot, and lambda= 1/2 means you're half-way inbetween.

I wonder what happens if you make one without a cat curve cut on the sides? If you notice the entire length of the hammock (whoopie, triangles and hammock) form a cat curve when you are in it. I think the sides exagerate the cat curve when you in the hammock, so if you didn't cut a cat curve on the sides wouldn't you still get a cat curve due to your weight pulling in the edges. Hmmm something to think about a bit more.
what happens is that your middle part sags lower than the rest of the hammock. In a hammock with side suspension and a curved side, the middle part is held up creating flatness because there is less fabric there. With the hammock with suspension and flat sides you'll have the sides dip in the center, but because the hammock is the same width there, the center is lower. The sides dip because the hammock is sort of folding in the middle. Anyway, won't be flat.

4. Figures Grizz would throw lambda in there to make it all clear.

5. ## Thanks

Ber - I would like to thank for your timely posting on the carbon fiber spreaders. TiredFeet brought your work to my attention and it is quite timely. I had made a Bridge Hammock for a friend, but he didn't want to use his hiking poles for the spreaders. I had been searching around for light weight material for spreader bars and decided to use your research in finding a vendor and the right size bar.

The head spreader on my Bridges is 34.375" long and the foot spreader is 24.375". The fabric on both ends is 44" wide. I use webbing pockets to contain the ends of the spreaders. This is done for a couple of reasons.

My approach is slightly different in that my friend did not want to carry a spreader bar that is 34.375" long on his pack and carrying on his hiking pole would also be problematic because of the length.

So I had to make the head spreader bar 2 piece. I accomplished this using a slip joint like that used for tent poles. The head spreader is made up of a 24.375" long piece and a 10" long piece. This places the slip joint off-center. My analysis indicated that the radial forces on the slip joint would be reduced significantly by placing the slip joint off-center in this manner. I used some AL tubing I had left over from a previous project, 0.500" x 0.028" x 6" for the slip joint insert. Used super glue to bond the AL to one end of the 10" carbon fiber tube (been using it for years in my carbon fiber arrows and cross bow bolts and has worked very well).

One problem using the webbing pockets instead of the captured end spike like you use (that method can also be used on my Bridges by sliding the webbing pocket out of the way, but the pocket is used most of the time) is that the radial compression forces of the suspension and pocket will crush hollow tubing spreaders. I learned this quickly with bamboo spreaders. The ends were crushed flat and I had to use plugs in the ends. To overcome this problem with the carbon fiber tubes, I used AL tubing 0.500" x 0.035" x 1.5". These were slipped into the ends. They are not bonded, but rely simply on the friction fit to keep the AL in place. I didn't know if the carbon fiber would be strong enough radially to withstand the radial crushing forces, but was very sure the AL was. So I used the AL tubing to reinforce the ends of the carbon fiber spreaders that get inserted into the webbing pockets.

So far the carbon fiber spreaders have been working very well. They have been used with people from slightly under 150 lbs (myself) to those over 180 lbs. The carbon fiber spreaders exhibit no tendency to flex.

My friend is now very happy. I devised a method to attach the 3 pieces (2 header end pieces and the single foot spreader) to his hiking pole that keeps them secure. Since the weight of all 3 pieces is only 3.45 oz, he says that he doesn't even notice the extra weight on the hiking pole.

Again I would like to thank you for timely research and posting on the carbon fiber tubes as spreader bars - they work very well and are very light.

6. Can you post pictures of your carbon fiber poles and size/source info. I posted mine under cerbon fiber poles, apparently I can't spell.

My poles were sectioned 3 piece for the header and 2 piece for the footer.
Unfortunately while playing around I used a very short triangle and had pole failure. My aluminum pole worked fine in the same setup, but the CF pole couldn't take the strain.
Thanks,
Ed

7. I too would like to see your setup TeeDee!

8. That thing is Purdy for sure , heck I'd buy one.

9. You need the cat cut to get the flat lay. For sure.

10. A small update on the carbon fiber spreader bars.

They are still working great.

But I was getting a little nervous about butting the two sections of carbon fiber at the slip joint. Not too sure that butting the carbon fiber against carbon fiber under pressure would last long term.

So I took out a little insurance: Got an O-ring that fit tightly on the Al part of the slip joint and slid it up tight against the carbon fiber tube.

That places the small O-ring between the two carbon fiber tubes of the slip joint. Hopefully this will reduce or eliminate the wear of the two carbon fiber tubes against each other under pressure.

Time will tell.