concept, bridge, new design?

[XJ35S]

I have been reviewing bridge hammocks and the changes they have gone through. I was thinking extra wide and more flat and this thought popped into my head.

Picture this. An 11' x 5' rectangle of material. 3 feet in from each end and parallel to the end we sew in a piece of webbing with multiple burned in holes for adjustment of the spreader bar. Down both long edges is your support webbing. That's it.

Here is a 1/10th scale of this concept. My thought is a wide no shoulder squeeze lay. I'm 5'11" and scaled the spreaders to be 6' apart. The sun screen tube is a scale of 400lb person, all I had to fit...


This seemed to work fine except the suspension lines have to be perfectly centered or the hammock will lean. I think this is a way to adjust for different size and shape people, by moving the head or foot end bars up or down the webbing for comfort.


I know I'm crazy but let's roll with this...






It even has a becket on the Braided Mason line.



Pretty flat. and room at the sides.

[BananaHammock]

Check out Townsend Outdoors / Just Bills Big Guy Bridge or his Luxury Bridge. I think it is similar to this with a few modifications more.

[XJ35S]

Yeah but the spreaders are at the top and they too, are narrow. I'm hoping this concept will make a more cot like sleep platform.

[BananaHammock]

Ah, I couldn’t really see how they were at the bottom. Interesting. Do you think raised feet would cause you to slide into the bar?

[Just Bill]

Not trying to discourage you overmuch... but sharing information and some feedback.

Technically that is not a bridge hammock; it's a spreader bar hammock.

A spreader bar hammock works by spreading the fabric so that it doesn't collapse when you lay in it. https://www.hayneedle.com/product/be...yABEgL3PfD_BwE

What makes it a bridge (short for suspension bridge) is that the spreader bars act as the 'towers' which support the "deck" (fabric or bed area. The deck is suspended with a curved suspension cable and supported to create a flat or even slightly inverted surface. This video shows the structure of a bridge hammock. While it is one of mine (a recessed bar bridge) the principal is the same for an End Bar bridge (RR or BMBH).
The poles are the towers, the amsteel is the suspension cable, and the piece of webbing is a section of the deck. This video allows you to see the literal lines of force. My weight is introduced- carried along the webbing to various points on the suspension line; then transferred out to each end of the suspension along a clean path. All the poles are doing is acting as towers under compression. Because the rest of the suspension is allowed to move or flow with various loads... it always arrives at the pole itself cleanly and in balance with it's opposing side.


In your design:

The suspension is the edges of the piece of fabric. Rather than gathering the ends though you're basically hanging a hunk of fabric, then jambing in a spreader bar into the bed area to prevent collapse.
If you wanted to pursue the idea... you would need to dramatically reinforce the ends or more practically; simply cut down the blank rectangle to roughly 6'6" (you don't want it to be your exact height).

Force always flows from point to point. So even with the webbing you have shown backing the bars... that weight needs to then get transferred out to the ends in some way. Bare minimum you'd need to roll webbing into the edges of the fabric or you'd like tear out.

The bigger concern however is the spreader bars. If weight is no issue- some heavy pipe or oak dowels could be used. But the flatter you push the hammock- the more force you place on the bars. By dropping the bars lower, you introduce more 'layers' of force. It's a bit like drawing a bow in multiple directions. Your goal (if keeping weight down) is to reduce the forces as closely as possible to a single compression force inline with the pole. In a suspension bridge... the tower(pole) is a column... taking load in a single direction. In this case; you are introducing loads you are not anticipating. Broken spreader bars can be extremely dangerous.

With the bar dropped as shown- you'd find exit and entry would be difficult. When loaded... you'd find that the hammock would form a pear shape- with you and the bar forming the larger bulge at the bottom and the top narrowing back down to a bottleneck.
To correct that... you'd basically trim the excess fabric until you were closer to a spreader bar hammock.

If you're saying to yourself... what's with this dude? Part of the reason you're not seeing these issues in your model; is that you don't have it loaded at 1/10th scale. At a few ounces worth of lotion (rather than 18-20lbs) you're not seeing the lines of force that would develop I'm describing. Bridges are tough because it's hard to get something sufficiently dense to model it so you have to visualize ALOT.

Grizz designed a 'convertable bridge' at one point to resolve the issues with your basic idea. It was a gathered end (to transfer load properly from the suspension points (trees) to the bar) that was also a bridge hammock in that you could put spreader bars into it. To make an overly generous sized version you'd have to keep scaling up from there. For a 6' bedspace and 4' bars you'd need a roughly 5'x15' blank.

You can do a dropped bar; but I did not pursue that idea as the spreader bar materials I prefer(acceptable for backpacking) would not take the loads unless I engineered a shape like a re-curve bow that would react to 'load'. Somewhat like a cambered beam basically that is curved against the anticipated load.
However- you'd want the bar outside the bridge, not inside. And the bar would need to be roughly 125% as wide as the bedspace you were trying to get. But this bar is taking compression and axial loads and must bend without breaking much like a bow that was strung backwards.

Overall:
A spreader bar design is a fairly flat lay hammock. Though it can be extremely tippy (why people think true bridges are tippy). However the mechanics of a spreader bar design require fairly heavy materials to get it to work as desired. Keep in mind... all fabric deflects under body weight. So you not only need a stout bar, but a stiff/heavy fabric to support you without excess stress. It might be possible to design a decent spreader bar hammock with a 2.4 ounce ripstop and 3/4" aluminum poles; but in my opinion the finished weight would disqualify it. But for a backyard hammock you can probably build a tank... but at some point if weight is no object you might as well simply build a portaledge and be done with it. https://www.rei.com/product/100519/b...SABEgKjxPD_BwE

A spreader bar design does solve the side to side collapse issue- but it relies on tension and/or heavy materials to 'pick up' the middle. Without a very shallow hang angle on your suspension or very stiff fabric; you'd find the spreader bar hammock to lay much like a gathered end 'banana'. You wouldn't have any calf ridge or shoulder squeeze, but you wouldn't be very flat from head to toe.

The advantage to a true bridge is in the suspension itself. By introducing all the curves you can 'shape' the deck (bedspace) with the least amount of materials.
Unlike a suspension bridge with a rigid deck, we are still limited by the fact we are using fabric that deflects under load. However if done carefully that actually stabilizes the bridge and eliminates the tippy factor. The deeper you make the bridge, the more stable it is. Also- by allowing some deflection- you maintain that 'weightless/memory foam' quality in the bedspace itself that makes people fall in love with hammocks.

The greatest advantage though is the 'pick me up' in the center. By introducing the curves in the fabric you are essentially building a cambered deck, which is pre-loaded against center collapse. In many ways, the bridges I build are very much like a recurve bow in that regard. In fact if you ask the few customers of mine who missloaded the poles they would describe them very much like a bow and arrow when the pole punched through the fabric under load. https://thisgearsforyou.com/big-boy-bridge/

The original bridge designs of Tee-Dee and those who followed roughly follow that arc of ideas: spreader bar type look, with introduction of suspension bridge principals to solve issues.
https://www.hammockforums.net/forum/...ign-Principles

The problem though is the more 'flat' you go, the more force you introduce. My 'Big Guy' style bridges are very labor intensive to build as a result. Grizz and I were following a parallel path; but technically his Ariel was publicly shared before my stuff. And regardless of timing... I give huge credit to Grizz for pushing things so far and pushing me along with him.

It doesn't need to be that complicated though. I can build a more traditional end bar bridge in 1/4 the time, while I'm not ready to share it... I recently created a new method of end bar construction that seems to be going well that I've been testing over the last few weeks. These can also be lighter too. I may have even broken my current record for the lightest bridge in the world! At 230lbs I've been sleeping in the heavier model which comes in at 12 ounces (poles included, no suspension). The lighter version is 10 ounces. With my trekking pole conversion kit though (to match Grizz's original) then the one I'm sleeping in comes in at eight ounces... which I believe I could take tree to tree for 10 ounces all in, the lighter version would come in around 8 ounces. Always something fun to do with bridges!

Putting everything in balance is the hard part.
But I would not even begin to suggest that there is no room for innovation or ideas when it comes to clever ways to combine fabric with spreaders... so do a bit more head scratching and research perhaps... but at some point go for it! My first bridge was built from tyvek of all things. It exploded the second I sat in it. I've probably built more junk than I've built successes. But I like to think I got one or two good ones along the way.

[Intimidator]

I can build a more traditional end bar bridge in 1/4 the time, while I'm not ready to share it... I recently created a new method of end bar construction that seems to be going well that I've been testing over the last few weeks. These can also be lighter too. I may have even broken my current record for the lightest bridge in the world! At 230lbs I've been sleeping in the heavier model which comes in at 12 ounces (poles included, no suspension).

When you are ready to share... Send me an email or something. I'd be in to buy a tester.

[gmcttr]

...Pretty flat. and room at the sides...

It has to lay flat with the rigid "human" model. Try it with a flexible model like a washcloth rolled up or one sock stuffed inside another.

[Just Bill]

When you are ready to share... Send me an email or something. I'd be in to buy a tester.

I just put a few weeks on two different designs... mainly based on my medium sized bridges.

By far... the Luxury, Big Guy, and Happy Medium are the best bridges I can make. I'm still shooting for the Mountain Hanger Prototype soon (120% bigger).
But the biggest complaint or reservation is that not everyone needs or can afford them. For those Big Guys or Luxury users... they are priceless. But a $400 hammock is not an easy pickup.

At my size (men's XL shirt- 24"wide tricep to tricep- and 230lbs) they are a hair tight for a back sleeper... but I have fallen asleep on my back in them. Wouldn't call it squeeze... but it is noticable. Since I mainly sleep semi-side or full side though it's not an issue for me. That's something I hear often from folks regarding the RR... so I guess this one is similar in size. That said I'm going to try to dial up the pop in the center to see if I can get this thing closer to my Happy Medium. The happy medium is coming in right about 16 ounces with poles (200-225lbs limit), or 12 ounces for the SUL version (160lb or so weight limit).

Point being- I'd think you'd notice the same issue.

That said... I'm thinking I might just be able to pull off 'big' version too that is based upon the poles I use for the bigger models. As an end bar... it would fall in between my Luxury/BG size and the medium. But hopefully come in around half the cost. I have a working 36" bar model (pairs with the trekking poles too)... but shooting for the larger head bar model too.

I started with End Bar designs, but never liked them. However new materials and five years of recessed bars and I've learned a few new tricks. I'm not looking to do a Ridgerunner knock off, but I think I have something unique in combining my geometry and both new materials and assembly that would make it an end bar worthy of doing. As I joked to someone recently... I have a Porsche, now I need a volkswagen.

I built five or so thus far... and I need to spend some time sorting out what webbing/suspension/fabric combos to use.
Hybrid Robic 1.2 (no go for me, held my 120lb wife).

hybrid Robic 1.7- used two versions thus far for two weeks each. I built a Hex 70 version too... maybe I'll just kick that to you to check out.

But I just got a box from dutch, and got a box from you coming shortly. Various webbings from Kevlar to UHMWPE to nylon and poly. The 2.2 UHMPE is holding okay without too much roll up... but the 2.2 Kevlar or 1.5 spider was too light. I'm hoping to find something in that range (3.3 kevlar or 3.25 pack webbing) that will balance it out better.
Got some Hexon 2.4 and 1.6 to add to the mix as well to try. End bars behave differently and these fabrics may work better than the hybrid for this application.

Not sure I'll get it this weekend or not... but I plan to rip off a dozen or so variants and will be looking for testers on those for sure. Proof of concept is there... now it's a question of durability and ratings.

I may simply go with a 'cheap bomber' as economy is one goal. A simple webbing and 2.4 I know will hold up...

But building the lightest bridge in the world is how this all started for me... so I just can't help myself
I'm going to try to get the Hybrid 1.2 to hold me... if I pull that off it would mean a 6 ounce medium bridge.
Pair that with 2.25 ounces (trekking pole kit) and 2 ounce or less huggers and whoopies and that's about there for a mass market version you aren't too scared to fart in.
CF poles and suspension would still put it around 13 ounces including the poles tree to tree.
But... worst case I bump the fabric and we're only talking 1.5 ounces more... still pretty exciting.

[Intimidator]

I get so excited reading your posts. We can chat via email or something when you get time (I know you already work like 79 hours per day), because I can probably provide some resources for you for prototypes. Unique geometry gets me warm and fuzzy inside.

I think the pack style venom webbing might do the trick. I have edged backpack straps/pockets and a tarp with it and was pleased with the results.

[Just Bill]

I get so excited reading your posts. We can chat via email or something when you get time (I know you already work like 79 hours per day), because I can probably provide some resources for you for prototypes. Unique geometry gets me warm and fuzzy inside.

I think the pack style venom webbing might do the trick. I have edged backpack straps/pockets and a tarp with it and was pleased with the results.

One of the big tricks with bridges with extreme geometry like mine... is matching the tension created in the suspension parts to the stretch in the fabric.
If you go too rigid... the fabric (stitching) bears all the load and you get stitch elongation and eventually tearout. Over the years I believe I've resolved the end tearout issue, but the middle remains a problem.
If you go too soft... it will all stretch together but the bridge gets too saggy.

So it's a tough balance.

I can build with half inch grosgrain actually. The original micro bridges don't use webbing at all, just good solid tricks and construction methods to make it all work. As far as I know... it's still the only bridge that can hold 200lbs with .490 poles, though I wouldn't call it stout by any means, lol.

The Hybrid 1.2 experiment this round is with nylon grosgrain but suffers from too much stretch. (Though it resulted in a 4.5 ounce bridge!)
I'll be trying another with some other structure to see if I can maintain the shape without overstressing the fabric... though I suspect that will have to remain a 175lb or so rating... no reason to withhold those from those who can use them. I noticed with my 1.2 happy medium's that I was actually damaging them from testing them at my weight, but the testers who tried the 1.2 were okay with it since they didn't overload it to start.

Overall... I've found chasing the bottom end to be more useful. It's harder in the short term in regard to piles of busted prototypes... but in the long term once you can establish the edge of the cliff it's much easier to stand on the edge or walk back a step than to build safe and try to inch forward. The ONLY reason I can walk around in the Luxury bridge is because I had to resolve all the issues on the micro.