DYI WBBB Hammock Thoughts (Plans)

[Snowball]

I see no change to get enlightened (!) and do not understand the math behind the WBBB footbox design. After severe reading of various old threads I have only a rough idea what the dimensions of the footbox should be and what structural ramifications I can expect if I alter the design. And my paper templates show me already what can happen if I do something wrong - even without a bug net the design is not easy. In order to get started I decided to sew a zipper and identical panels on both sides like JerryW did it with his roomy #5 hammock. That way it is a little easier to get the bug net finished and I can decide about a custom-made footbox/shelf later or realize some other options. Since I'm a side sleeper it could happen that I get lucky without a footbox too.



Think again. This is only one question I cannot answer. I'm sure there are a lot more. I would in no case cut into the hammock body. The right side is not only higher. It is shorter (because of the shorter hypotenuse of the footbox triangle) and has therefore a much higher tension than the other side. But the main question is, what this differences mean for the bug net. How can it be, that the bug net is (or should be) symmetric if you pitch all together?

BTW. You have to be careful with paper models. They will often cheat you because paper is stiffer than fabric.
I had some good ideas for some other designs and they worked fine as paper models but when I made them in fabric (models) it was a NoGo.

[xxl_hanger]

This foot box thing is complicated.

It is not only the foot box. Im sure it is all together.

I do understand the triangle (hypotenuse)a^2+b^2=c^2. What feels good or bad is a matter of preference not so much the design but I do like this design.

I like the design too and would like to unterstand it. Therefore I made quite a number of calculations with the Pythagorean theorem. At least it helps to measure almost all diagonal lines exactly and find the differences to the straight lines (like the hammock body line). Also on the shelf I found four different right triangles. But all my calculations didn't help. I could not imagine the 3rd dimension - the bug net. I tried this because warbonnetguy said in an old thread the footbox should be considered more like an hourglass than a triangle.

I found this statement here in this interesting thread:
https://www.hammockforums.net/forum/...less-blackbird

With a similar approach I got one of my best paper template solutions:
https://www.hammockforums.net/forum/...2&d=1261410991

Not because of the footbox size. My cut was because of an error similar like this:
https://www.hammockforums.net/forum/...0&d=1261518645

not like this:
https://www.hammockforums.net/forum/...1&d=1261518645

I used also this form for my tests (this are two right triangles, but they are rather skewed)
http://theultimatehang.com/wp-conten...rd-footbox.jpg

and with quite a number of pictures and nice videos, like this one:
https://www.youtube.com/watch?v=gzDrLDnMI9s

Even if I would know the exact footbox format it wouldn't help me further. Therefore I don't try it. The chance that I get a bad result on my first shot on a hammock looks to risky for me.

The bug net can be symmetrical because the total length of each sides are more or less the same when you include the perimeter of the shelf.

I think it is easier to make the hammock step by step. First the hammock without a footbox. Then you can add one with cheap fabric first and can see what happens with different dimensions, how your lay would be, were the footbox should be and so on. On this basis you have at least a chance to find out what the footbox does to your hammock. Next you can add the shelf and then you can modify your bugnet with the tie outs. I try it perhaps this way with a zipper. If I'm satisfied with the result I perhaps make a topcover with the same cut also. And if I get a nice DIY hammock without a footbox I will be pleased to have one.

[xxl_hanger]

BTW. You have to be careful with paper models. They will often cheat you because paper is stiffer than fabric.
I had some good ideas for some other designs and they worked fine as paper models but when I made them in fabric (models) it was a NoGo.

I just slept two nights and found a much better solution. Now I'm on the hunt for a WBBB clone again.

I think I will try to make something like a DL xlc clone with 1.9oz ripstop nylon. I will make all panels out of the same fabric than the inner layer body will be. The outer layer black and the inner layer and the panels in dark green. Exactly the same fabric quality. Only the colors are different. All panels and the zipper will not be included in the whipped hammock. I have to find a edge binding solution with grosgrain ribbon. I think this will be now my hardest part. I only know already where I can buy a toggle which looks almost the same than the one which Warbonnet uses for the BB xlc. Don't know yet whether I need a top-cover. But I would have already enough fabric to try it.

If the planning is done (with the trick I found out) I will first realize the hammock body and test it before I cut out the panels. I think I will do it step by step. First the footbox and then the shelf. I found already a paper model solution which looks like a real BB and that my clone will have not too much tension in the footbox area. And slowly but surely I understand also the design. I can see already that my bug net can be symmetric if I still improve the footbox a bit.

The trick of the blackbird is the inverted footbox and shelf panel (hourglass-shaped) design with this reinforcement part in the middle. If the cut is done properly the rest should be easy. If not the whole hammock will be skewed.

[mrcheviot]

After my failed project I have been thinking. Apparently some don’t like the high side by the shelf and I am one of them. So why not make a cat cut at the top end of the side? I think 6”-8” would be what I would go for. It will lower the side but I am not sure how it will work in a combination with the triangle/foot box. I think the linear edge is needed in the foot box area but I am not sure. The down side the side panel needs to be redesigned because the edge will be longer. Could be the panel could be corrected by adding the shape of the cat cut but it will be harder to line up or maybe just make it a bit longer?



Just a thought

Attachment 102819

I am actually planning on doing this for a netless SL hammock w/ footbox (a la woodsman X). I think in your diagram the start of the cat cut needs to be shifted to the right a bit to accommodate the longer edge of the triangle. I would introduce 3/8" grosgrain into the rolled hem from just to the left of the rightmost triangle end point to perhaps 6" past the start of the curve (so maybe 16" total), this will be the point where the most stress in the side will occur. For the curve itself, a normal rolled hem will work fine but I would double stitch it - this is how Jared from SLD does the Streamliner and it's plenty strong.

My only concern with this is that too great a curve would tighten up the head end to the point where it would cause additional shoulder squeeze or more likely upward pressure on your right shoulder. I think it's important to figure out the curve after the footbox long edge has been accounted for, so you're only removing the (semi) floppy fabric at the shoulder and no more. My estimates had the curve depth at around 3-4". A deeper curve may require lengthening the top side at the head end to avoid excessive tension and actually give yourself some floppy fabric to remove, but of course this needs to be considered in the context of your end whipping or channel plans.

One of the main reasons I'm considering this (and keeping the curve shallow) is less to remove excess fabric and more to allow for a long WBRR style saddle bag pocket in lieu of the shelf (since it's netless). If I put a non-load bearing line at the beginning & end of the curve, it will support the back side of the pocket, while the front (hammock side) of the pocket will be stitched into and follow the curve hem, so it'll be easy to reach in and out of it.

[Snowball]

I did not make the cut so I don’t know if it would work or not. The hammock was used for another project.

[RE8ELD0G]

Posted this on a old dead thread and someone pointed me over to this one.

Sorry but there is so much to this thread and the others about this type of hammock and now im completely confuddled.
I have made a 11' hammock.
It has a ridgeline of 106" but is adjustable by about 5" each way.
what size triangle do i need to make the footbox???
I cant wrap my head around the engineering maths..........lol

Thanks

[xxl_hanger]

It depends how tall you are! I said this already in this other thread.

You can see the plans of TheXringHunt. On the 9' plans he started with 24" and then used a 90° angle. You can see the height of the fb which is 19,6875". No you can figure the center of the fb which is sqrt(24^2 - 19,6875^2) = 13,726".

Now check this. The length of the hammock-body (without the whipping) is around 130". Let's assume your are 70" tall. 130-70 = 60/2 = 30. Check that out. I assume that the lower corner of your fb should be shifted more to the center of the hammock by at least 10".

With the above information and a little trig you can calculate further.

The angle TheXringHunt used at the fb-end is:
sine (alpha) = 19,6875/24 = 0,8203
arc-sine(0,8203) = 55,11°.

Now you know the other angle too.
180° - 90° - 55,11° = 34,89°

How long is the long side (hypotenuse)?
cosine(55,11) = 24/H -> H = 24/cosine(55,11) = 24/0,572 = 41,957"

How long is the opposite side?
tangent(55,11) = OS/24 -> OS = tangent(55,11)*24 = 34.416"

Though you know the whole triangle. The long side is ~42" and the other sides are 24" and ~34,5". The form is a right triangle. This is btw. the same size Blackgoat used there.

I think you should try out the form you can see on the website of Derek Hansen. The picture there shows a fb triangle which has a 33°, 43° and 104° angle at the lower corner. Let's assume you take the same height than TheXringHunt which is 19,6875". Then you can determine the triangle as follows.

length of the triangle at the hammock end (footbox-end)?
sine(33) = 19,6875/H -> H = 19,6875/sin(33) = 36,14"

length of the triangle at the center side?
sine(43) = 19,6875/H -> H = 19,6875/sin(43) = 28,867"

length of the long-side?
28,867/sine(33) = h/sine(104)
h = 28,867 * 0.9702 /0.5446= 51,42"

Depending how tall you are, I would guess you should make the length of the fb triangle at the foot-end of the hammock something between 36" and 24". If you follow my instructions I have given you in this other thread you should get an almost perfect custom-made BB clone for your body size .

[RE8ELD0G]

Thanks again but

I have no idea what you just wrote, it may as well have been in ancient greek.

Im 5'9" tall and the hammock without whipping is 11' long and 62" wide.

I guess its going to be a very long time before this gets done as i have nowhere near me to hang.
Will need to go out.....Hang and take measurements......drive home and sew foot box.....go out and test.
Then repeat until correct.

Wish i had paid more attention at school but math and reading plans seem to be weak points with me.

[xxl_hanger]

I recaped my trig shool knowledge a bit because I found a number of triangles also on tarps. There are some nice videos on YouTube which are very helpfull.

With 5'9" I would realize the 8' plans of TheXringHunt without major adjustment. This should fit you pretty well, saves weight and a lot of additional considerations. Also your tarp could be a bit shorter then. According to my view the 8' plans are better conceived. I'm 9" longer and have some problems with the 9' plans but I think the 8' model would be too short for me.

[Algonquin_bound]

That looks mostly right, but did you factor in the effects of the earth's rotation, keeping in mind the moons gravitational pull when the ocean is at low tide?