Bridge Hammocks & the OPTIMUM Spreader Bar Length??

I am making a replacement bridge hammock for a "portable hammock stand" that I purchased a few months back.

Hammock stand is AWESOME, but the bridge hammock that came with the stand had a net that wasn't incredibly comfortable... plus it started to tear, so I have to replace it.

I've got the hammock mostly measured out and my buddy is finishing up the hemming right now.

-- 80" length
-- 58" width at head/foot
-- 44" width at mid-point (7" from each side)

The original spreader bar on the original hammock was only 16" wide from end to end, but the spreader bar itself was curved to prevent hitting the 4 legs of the stand... so perhaps 17" of length.

I guess that the 80% rule of the triangle will still apply here???

Is this 80% rule the only thing to go buy in determining optimum spreader bar length??

If the imaginary legs of the triangle are 13 inches or so, then I should stick with a 16"-17" spreader bar??

My new spreader bar won't be curved, but will be a straight piece of PVC pipe. I guess I'll need to see if it taps the legs of the stand first. But definitely curious if the 80% rule is the only thing to go by...

Quote:

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Originally Posted by grndslm

I am making a replacement bridge hammock for a "portable hammock stand" that I purchased a few months back.

Hammock stand is AWESOME, but the bridge hammock that came with the stand had a net that wasn't incredibly comfortable... plus it started to tear, so I have to replace it.

I've got the hammock mostly measured out and my buddy is finishing up the hemming right now.

-- 80" length
-- 58" width at head/foot
-- 44" width at mid-point (7" from each side)

The original spreader bar on the original hammock was only 16" wide from end to end, but the spreader bar itself was curved to prevent hitting the 4 legs of the stand... so perhaps 17" of length.

I guess that the 80% rule of the triangle will still apply here???

Is this 80% rule the only thing to go buy in determining optimum spreader bar length??

If the imaginary legs of the triangle are 13 inches or so, then I should stick with a 16"-17" spreader bar??

My new spreader bar won't be curved, but will be a straight piece of PVC pipe. I guess I'll need to see if it taps the legs of the stand first. But definitely curious if the 80% rule is the only thing to go by...

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The JRB BMBH spreader bar is about 30". I typically use one that is 36", at least at the head. The spreader on the Eureka Chrysalis is something like 42", or maybe 44". You get the picture. 16" is remarkably short. I'm having a hard time imaging someone getting in and out of a hammock with the dimensions you cite, with a 16" spread. Well, getting in I can imagine, getting out, not so much. Wonder if you're looking at only one segment of a pair???

But yes, whatever the spreader bar length is, the 80% or so rule works as it is a rule of thumb w.r.t. compression forces, which depend on the angle of the spreader bar and triangle side, not the specific lengths involved.

16" is the way the original hammock was setup. It was actually pretty good -- laid pretty flat.

We had two 28." spreader bars already made, so we decided to test those out first.... but considering the the end points of the hammock stand only reach 96" or so apart, the triangle legs were virtually half of the spreader bar length. Indeed, the compression forces of a 50% ratio caused the 3/4" pvc pipe to bend an unworkable degree.

Cutting one 28.5" pvc pipe in half, we had 14.25" spreader bars. The adjustable whoopie slings we made for the suspension triangles were made a bit longer, but, at minimum, I can lie in the hammock without touching the ground. I think the 14" spreader bars are do-able, but the hammock doesn't seem to be laying as flat as I'd like.

Sooo... How to make it lay flatter?????

Tighten the suspension? Increase spreader bar length?

I'm guessing tighten suspension, because I don't see how increasing the spreader bar length will help the cause. . . . .

Thanks for the help, Grizzle. Fo shizzle!!

So now that I've looked at the hammock again, I can see how increasing spreader bar length to 30" or so would tighten the middle up, which is th whole point of the bridge hammock.

As long as the spreader bar can handle the compression of a suspension triangle with 50% length of the bar... then it should work.

At that point, the OPTIMUM length of the spreader bar then comes down to the width of the ends and mid-point of the hammock. Or mainly just the mid-point?

I guess there's no other way to find the optimum than to try various lengths??? Starting at 30", give or take 6"??

Will have to put some iron rebar inside the 28" pvc pipe to prevent bending, then head to lowes for some steel tubing, perhaps.

Modify the stand to make it longer? Or use a spreader bar strong enough to resist whatever compression forces you subject it to? If you're only going to use the hammock with the stand, it doesn't matter much how heavy it is, right?

Pictures please

Here ya go....

Added the rebar inside the PVC pipe. It was working great, kept the pipe as straight as possible.

I tightened the suspension triangle whoopie sling as tight as possible. I got in and it felt great, but I still felt like there was more slack entering into the suspension that I couldn't account for. Finally, I noticed that the amsteel blue was cutting a line through at least 2 of the 4 corners... as seen in the next to last pic, below.

Will try to find a reasonable deal on 3/4" steel pipe when I get a chance. Is there something fairly common that is used for "extra strong" spreader bars??? Or are most all suggestions for minimalist weight?

If you want to use that PVC something simple like adding a coupler should stop the Amsteel from cutting into it. The coupler is thicker.
This technically isn't a bridge hammock with out the suspension ropes on the sides, its more of a spreader bar hammock. With this type of hammock all the forces are on your bars as you don't have any webbing or the like running the length. If you go to a goodwill or junk yard look for a clothing rack or old coffee table made of pipe. I used an old clothing rack for my first bridge spreader bars. The pipes were only 1/2 but the wall thickness was pretty stout. Look for free or dirt cheap options. Good luck to you.

That's what I told my friend! ... that a bridge hammock gets its name from the suspension going down the sides. But we both agreed it would be easier this way. I guess it was up until finding a strong enough bar. :laugh:

Excellent tips on some couplers for the ends of the PVC. And for the goodwill option!! My buddy was talking about going a couple days ago for clothes, so that could save me a trip *and* some money when we go today. GRACIAS!

I'm slow sometimes.

:rolleyes: ;)

Oh man no pokes at your hammock. You got to do your own thing, no need to go into making a bridge all you need is a spreader bar hammock. I was just commenting on the name of bridge. Calling this a bridge hammock will get you different suggestions than you might need for a spreader bar hammock. With a bridge the spreader bars are reacting different. All the force on bridge spreaders should be on the length of the spreader. this is why spreader bar length is a percentage of the suspension triangle.
On a spreader bar hammock the forces are in the entire spreader bar.

Jazilla is right. Some here have lots of experience building bridge hammocks. I do not know of many on HF who have experience making spreader bar hammocks. You are experimenting, and I am very interested in your results.

That makes me feel extra special then. :shades:

Here's what I've got now, which I'm pretty happy with....

The ends of the hammock were sewn snuggly for 3/4" PVC pipe. I got 1/2" wide iron pipe because it was cheaper. This slid in and out of the ends of the hammock easily, but it was almost too easy... because while someone was in it, the pipe would become vertical from all the fabric sliding to the top of the pipe. Wrapped two of the iron pipes in twine, then slept in it one night. Came to realize that, even tho I used a file to round out the inside of the iron pipe as smooth as possible, it was still cutting my amsteel whoopie sling triangle suspension.

Returned to Home Depot and got the "pipe man", who cut my 10 ft pipe into four equal 30" sections to add threaded ends onto the two sections that I didn't already twine. Then I searched for something that would fit to smooth out the threading, realized it wasn't threaded properly and got him to re-thread the ends a bit deeper the second time around. Then got some 1/2" bushing end cap thingys from the electrical section. Looks like the amsteel is still cutting into these bushing end caps, but luckily, they're only $0.25 a piece. I guess the only real solution is for me to really round out the inside edges of the pipe when I get some time.