A good knot for tensegrity structures?

[matw]

I plan to build hobby tensegrity structures [1,2,3], and I am searching for a knot, like a buntline hitch [4], but can be dressed to an accurate length while under a fair bit of tension. The buntline hitch is hard to tie under tension, so, for taught lines, I normally anchor one end with a bunt line and then use a versatackle [5] for tensioning on the other. The versatackle works fine for tarps, but not for tensegrity structures, where I want small and secure knots at both ends of the tendon (rope). Small is for looks, and secure is for keeping the structures taught for extended periods of time [6].

The best candidate I've found is the load releasing configuration of the buntline hitch [3], where I might add extra wraps for the first loop around the "spar" for additional friction (like a sailing winch) to unload the rest of the hitch while dressing the knot. I realize I might have to retie the knot several time to get its length just right, but I can be patient.  The unloading part is important because I don't have enough hand strength, speed, or coordination to tie a simple hitch (of almost any kind) under tension.

Is my thinking sound? Might there be a better knot I should consider? If so a link to it would be greatly appreciated.

[1] A practicle Guide to Tensegrity Design, https://bobwb.tripod.com/tenseg/book/cover.html
[2] Tensegrity Prism, https://bobwb.tripod.com/tenseg/book/chap2_2.xml
[3] Shperical assembly, https://bobwb.tripod.com/prospect/prospect.htm#Oct6vnet
[4] slipped buntline hitch, https://notableknotindex.webs.com/slippedbuntline.html
[5] versatacle https://notableknotindex.webs.com/Versatackle.html
[6] Years? Would be nice. Depends on the tendon material. Marine lines might last months. Cables should last for years, but introduce a whole new can of worms for the attachments (without turnbuckles).

[agent_smith]

You could experiment with a #206 Crossing hitch (rock climbers know this as a Munter hitch or Italian hitch).
This hitch can be tensioned under load - and then tied off to secure it (to stop it from slipping/loosening).

Note: The Crossing hitch capsizes when load is reversed - and this is a normal property of the hitch.
The crossing hitch works best when paired with a carabiner (a 'HMS' carabiner).

[Dan_Lehman]

I'm having trouble picturing the task you're doing.
(And complete trouble --404 Error-- trying to view
your 1st reference (to a book).)  --really neat things,
though!

"marine lines might last months" ::  I've some piece
of black laid 1/4" PP that has been outside for decades.
Not sure of your thickness, but I'd think marine lines
would be in years vs. months.

--dl*
====

[matw]

Ok. I fixed the URL in my first reference and inserted a link to the book itself (it's great).

Thanks @agent_smith for  mentioning the Crossing Hitch #206! I didn't quite get it until I looked at #205 (the same knot but showing how it's finished). It's similar to the "Load Releasing" part of Roo's Buntline Hitch page [4], but differs by a 3/4 wrap around the standing line. I appreciate #206 being its own # in ABOK because it shows off how one can tie it under tension. I can imagine mixing and matching ideas here, and experimenting will reveal which works best. Fun!

@Dan_Lehman, That's encouraging to hear about your long term experience with marine line. Some line I use camping (e.g. Marlow Excel Pro) has no apparent creep over several days, but I have no idea how it holds up long term.  I think I'll dedicate one of my early projects to a high tension test over time. Maybe a couple to test different knot forms.
 
[4] slipped buntline hitch, https://notableknotindex.webs.com/slippedbuntline.html

[roo]

I plan to build hobby tensegrity structures [1,2,3], and I am searching for a knot, like a buntline hitch [4], but can be dressed to an accurate length while under a fair bit of tension. The buntline hitch is hard to tie under tension, so, for taught lines, I normally anchor one end with a bunt line and then use a versatackle [5] for tensioning on the other. The versatackle works fine for tarps, but not for tensegrity structures, where I want small and secure knots at both ends of the tendon (rope). Small is for looks, and secure is for keeping the structures taught for extended periods of time [6].

The best candidate I've found is the load releasing configuration of the buntline hitch [3], where I might add extra wraps for the first loop around the "spar" for additional friction (like a sailing winch) to unload the rest of the hitch while dressing the knot. I realize I might have to retie the knot several time to get its length just right, but I can be patient.  The unloading part is important because I don't have enough hand strength, speed, or coordination to tie a simple hitch (of almost any kind) under tension.

Is my thinking sound? Might there be a better knot I should consider? If so a link to it would be greatly appreciated.

[1] A practicle Guide to Tensegrity Design, https://bobwb.tripod.com/tenseg/book/cover.html
[2] Tensegrity Prism, https://bobwb.tripod.com/tenseg/book/chap2_2.xml
[3] Shperical assembly, https://bobwb.tripod.com/prospect/prospect.htm#Oct6vnet
[4] slipped buntline hitch, https://notableknotindex.webs.com/slippedbuntline.html
[5] versatacle https://notableknotindex.webs.com/Versatackle.html
[6] Years? Would be nice. Depends on the tendon material. Marine lines might last months. Cables should last for years, but introduce a whole new can of worms for the attachments (without turnbuckles).

A small HFP Slippery 8 Loop may have the function you desire without being too large:

https://notableknotindex.webs.com/slippery8.html

It is not intended to be tied under tension, but can be adjusted under some tension.  I find myself using it far more than I would have though possible.

[KC]

Buckminster Fuller's 60's Floating Compression/Tensegrity/Tension Integrity is a very important concept to me have reflected on for decades against standard technique support, and look to make sure purposefully that is not what am not trying to diagnose at the time.
We work all in tension with ropes, in Hitches and Bends as a pulling or holding framework must have at least that vertical high rigidity as work, and usually (99.9..%) the rigidity must be continuous , save this exception. In study of rope where the total rise can be shown as rigid parts but their support in turn  between is not always rigid parts as normally see.
.

i have a kinda standard Lego Tensegrity(above, gift from engineering son from our talks), there are also more advanced lego styles:

also i made a popsicle stick triangles style too.  Have studied when shown over the years etc.
i was actually looking at playing with this in square shape in pvc next, then drill out corner holes to fill with expanding foam for more rigidity thru members.  Am looking at actually cable/to not stretch that would change math on the center main tension, then was thinking a ProGrip in loop, at each corner from base to float(corners).
.

.
As long as have the main holding, while limiting the Degrees of Freedom thru the other points to essentially maintain structure balance to the solo main you can get the 'float'. 
Looking at trying in 3/4" as best co$t ratio.  If evolve to 1"-2"pvc costs would look at putting old broom stick parts thru the vertical straights, as first bending moment that failure cascades out from in the Lego model.  Still give internal foam finish with the broomstick in place.  Also looking at slanting the 3ways(2) 45degrees, then finish with 45degrees back to vertical instead of the 90's to the center main.  i think can also pitch the whole top 'yaw' 90degrees to not be the opposing mirrored left to right, but perhaps cross axis mirroing of left to rear matchings.
.
There are some fancies too, this is in the $1600 range(Etsy), similar is shown on youtube as a diy.

.
The fewer parts models i look at don't favor rope elasticity, but rather metal, Lego model is plastic chain links, but still not rope that would elongate over time and be a variable at start.
Was also looking to eye bolts to give an adjustment range at each point, once dialed in a few factor responses in rope friction hitches.
.
As study structures Frank Lloyd Wright comes up many times, and there is much around me actually. 
Buckminster Fuller was another astonishing architect in his own right and theories.
Please let us know what you come up with!

[matw]

A small HFP Slippery 8 Loop may have the function you desire without being too large:

https://notableknotindex.webs.com/slippery8.html

It is not intended to be tied under tension, but can be adjusted under some tension.  I find myself using it far more than I would have though possible.

Thanks! When I saw the the Slippry 8, I figured it would be a pain to tie under tension, but it's an interesting knot that I want to try out sometime. For this application, stress (tension) on the lines can be high depending on the geometry, which is why I thought of the Versatackle right away.

I like the idea of ABOK #206 with the addition of extra friction wraps to unload the final tie off (half hitch or buntline hitch probably). It doesn't have the mechanical advantage of the Versatackle, but I think it'll work well enough. We'll see when I get around to experimenting.

@TC there's so much I'd like to say about your comment, but I'll instead keep it simple and say I too have been inspired by these structures for decades. Also, everything gives a little bit (glass, steel, rock, ...) under stress. That's a good property in terms of absorbing shocks, but it goes bad when the tendons plasticly deform and don't spring back. I think modern marine lines might have what it takes to survive.

[KC]

i always look for radial dispersed vs. linear focused in all things, especially force.
In these 'simpler' nonRadial force Tensegrities i see a single main support, that must be the most nonDeforming/cable-like and strong;
The stabilizing tendons that keep the float aligned over the main, are loaded less; more likely to be rope friendly points.
Rectangular coffee table etc. dual the idea at opposing/competing side forces at ends of the expanse.
.
ANY other use of hanging with tension needs a continuous rigid compression at least as high as the floated base for 'integrity' to stand.
EVERYTHING  was looked at as had to have compression integrity to stand; Buckminster Fuller changed the game, or at least the view of the game.
Tension Integrity of this linear sort allows that the rigid rise can have the rope as part of the rise
>>but demands that the rigidities at either end of rope seam would be in overlapping positions, just connected 'seam' of overlap by nonRigid/flexible of cable/chain/perhaps static enough line.
.
In holistic sense, there is bio-tensegrity showing a theory of how humans and others internal systems use the principle with bones as the floating spacers to the load sharing tension integrities internally in many ways.
.
There are small toy builds of  Earth Magnet support with no connection at the main seam between the overlaps; one of my ideas was to use magnets with microthin rope thru center of magnets; and not mention magnets to enhance illusion of magic.  Has to be real close rigidities at connected seam for the magnetic tension use, but in structures seems that not too long at this point is best anyway to limit play to the sides from the main.  The thin line would give a limiter to distance and mis-alignment of the magnetic distance.