2X3 Wood Hammock stand

[DiscoveryDiver]

Taking inspiration from:
Headchange4u, TrailH4x and SinisterMinister

...I decided to see if 2X3 would hold the weight. I'm still a few days at least from trying it out, but I tried some other new assembly ideas I wanted to share in case it all works.

For the next handful of days, I only have an hour or two a day to devote, and I'm feeling my way around, so the slow pace.

Some pictures so far...

Details...
It's all 2X3
The base is usual design.

I have a new twist on the attachment of the support strut. I wanted to avoid detachable hardware, and avoid making any large holes on the flat side of the upright 2x3 (that will support the hammock weight).

I used some dowel inserts. They hold quite well, actually. Once loaded, the dowels will be taking some shear force, so I used two, 10mm walnut dowels.

Right now, I don't need anything to keep it all together since the dowels fit nice and snug, but that will change someday, so I looked for a way to keep it all together when the stand is unloaded.

I looked at a few options, simple types of door/gate locks, window locks and then I decided on these buckles(?). Simple and effective, they only need to keep the upright from falling to the ground when the hammock is unloaded, so they really don't need to be beefy at all.

The future...
This thing is really light right now (sorry I don't have a scale). I'm not going to put any wheels, since it's very easy to carry. I'm going to devise a system to allow the two base pieces (once I make them) that will allow them to be detached from spread position and reattached somewhere else on the frame so it all goes together compactly for carry/storage.

I'll post more pictures next week...

[OneEye]

Let us know how it turns out.

The engineer in me wants to calculate whether or not this will work, so I made some assumptions about your dimensions, and plugged them in to some standard wood design equations. Looks to me like this is going to be past even the normal factors of safety, so it will be relying on better than average performance from some of the components (fewer knots, better grain straightness, etc.). The 2x3 only has 1/2 the bending capacity of a 2x4 in its strong axis, but the failure mode on these things is probably lateral-torsional (sort of a twisting/buckling failure) so the strength is maybe a little closer. I'd love to see your actual dimensions to see what the equations say.

Of course I've calculated entire roof systems that are supposed to be on the floor, and mostly they were still overhead; although the one that was the most overstressed kept breaking in places. We just had an open-ended contract with the building owner to keep designing repairs for them.

Good luck.

[DiscoveryDiver]

Thanks, OE
From eye to eye up top, it's about 360 cm (about 12 feet) across. The tops of the poles are about 155 cm from the ground. The base was about the same as the plans posted in the others threads, somewhere like 5 1/2 - 6 feet long.

I guess I'd better wear my helmet and motorcycle crash suit when I test this out.

I did purchase two 2X4s to use as the uprights in case the 2X3s didn't work out...

[SinisterMinister]

DD - I love the craftsmanship. Yours makes mine look like it was made by the Little Rascals. I really like the dowels and buckle system you used.

I'm not an engineer, so take what I say as opinion. I think OneEeye is dead on the money regarding the twisting factor. I see major twisting/torque on the uprights in my 2x4 version. I would be fairly nervous about 2x3's snapping like twigs under the stress of my 190lbs. Of all the areas to make shortcuts to save weight, the uprights are probably not the best place to do it.

Also, something I've noticed in most of the builds I've seen that others have done is we all seem to forget about the support lines for the uprights shown in TrailH4x's original design. (Guilty) The support lines are attached to the uprights near the O-Bolts and then staked out to either side. These help with the twisting effect...by how much, I can't say...again, not an engineer.

Good luck and always wear a cup.

[OneEye]

Definitely some very nice craftsmanship in your assembly. I also like your take-down buckles.

Well, the overall dimensions are fairly close to what I was using. Do you know the angles, and where the bracing from brace to upright comes in? The angles make a difference in how much of the hammock forces are being carried in compression, and how much is being carried in bending. Do you have a link to the diagram you started from?

The twisting failure will actually be less of a problem the closer to square the member is, so what I was trying to say before was the 2x4's will really be crippled by wanting to twist away, where the weaker 2x3 is not as dramatically affected, so the final strengths might be slightly closer than my initial statement of 1/2 the strength. Lateral support at the top of the uprights will really help matters, it changes the primary failure mode by making the twist failure load much higher.

You probably just need a bouldering crash pad for underneath. The 2x3's will be so light you will hardly notice when they land on you. I'm not trying to tell you "it won't work", because the equations are built to help prevent failure of pieces outside the standard deviation from average. With wood that standard deviation is pretty wide (especially compared to steel).

[JohnSawyer]

I built my PHS from 2x3's with 2x4 uprights. That lever arm will put some extreme loads on the 2x3. When hanging your hammock, the lower you can get the suspension, the better, as more of the forces will be along the length of the upright, and less pulling it inward.

On my 2 PHS's, the 2x4's bend and twist enough to make me nervous, but I am 220lbs (100kg)...



I'd be concerned with the shear-strength of the dowel pins... That said, it looks great! Nice design!

[DiscoveryDiver]

Sinister, OneEye and JS - Many thanks for the continued input.

I do have 2X4s as backup. I'll do some destruction testing on the design and see what weight it fails at. I suppose I should have done that before making my dowel/buckle setup.

But in any case, I'll need to know what it can support. I weight 83 kg...

I'll be making the base and give it some testing next weekend, I'd suppose...

[OneEye]

Just for the record, I'm not trying to say "Won't work, nyaaah nyaaah". Just, sounds like you are pushing the envelope. Design calculations for Civil Engineering are extremely conservative. Mechanical Engineers try to bring a lot more precision to the effort, but also tend to use materials with less variability.

I'd love to see ongoing progress reports and a test hang.

[DiscoveryDiver]

Just for the record, I'm not trying to say "Won't work, nyaaah nyaaah". Just, sounds like you are pushing the envelope. Design calculations for Civil Engineering are extremely conservative. Mechanical Engineers try to bring a lot more precision to the effort, but also tend to use materials with less variability.

I'd love to see ongoing progress reports and a test hang.

I hope to get the base outriggers in place this week. I probably won't get to test hang until a week or so away.

Given all the feedback I've received here, i really might do some destruction testing to the point of failure...