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Paul's A-Frame Wofatish Idea

 
gardener
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Paul shared with me an idea of his for a really simple earth-sheltered structure.

The idea is it's a single post and single ridge beam, both made of BFL's (big fuckin' logs).  

It is intended to be a quick first build, in the spirit of the "Rob Roy 'first simple house'" from Mortgage Free. Possibly built in a single weekend if materials and tools are fully staged.

In describing it to me, Paul was adamant that this is not a wofati in the truest sense. For want of a better name, I'm currently calling this the A-Frame Wofatish. (I.e., it's a Wofati... ish).


The goal of this thread is to document, develop, and model the design. Likely discovering in the process some as yet hidden issues that need resolving.
IMG_20201028_122914.jpg
Composite sketch
Composite sketch
IMG_20201028_122905_1.jpg
Front elevation
Front elevation
 
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pollinator
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There must have been something in the air, because I doodled a similar A frame underground house last week after nostalgically watching a Mike Oehler video.

I was playing with the idea of setting up a BFL for posts and ridgebeam as well, then using slabwood as decking on the side poles. I was considering using straw for insulation like Tony Wrench's roundhouse build, then covering with epdm, building a alder tree lattice on the outside and then starting creepers at the base to act as the living roof.

I would think that it would be difficult to get the wofati like depth of material on the "roof" of the A frame for proper insulation. Or that the walls would be too steep to effectively keep soil in place.
 
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I think you'd definitely be playing with a "rocky forest mound" kind of alpine microclimate, where the soil is thin, because the only way you'd get it to stay is with sediment traps on-contour of your roof. You could have enough, I think, for some pasture, and plenty of alpine strawberries. The goats would be happy. The lamblords not so much.

-CK
 
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Cute - yes! But we need to run some numbers and ask some questions:

1. One of the reasons that A-frames have remained as fringe buildings is that taller people tend to be constantly bashing their heads. So with the size and slopes you're thinking of, what will be the floor area that corresponds to 6'6" height? Lower sections will still have lots of usefulness, but can 2 tall people pass each other without one needing to duck?

2. What kind of height are you thinking about - tall enough for a loft? That will solve some of the head room problem on the first floor and sleep's one of those things you don't need to do standing up!

3. What sort of ideas to you have already for keeping the dirt on the steep sides? I'm picturing a sort of "log box" idea covered with dirt. I'm wondering if the dirt under the "umbrellas" might need log boxes also so it doesn't slump or compact (I'm assuming too much compaction would reduce its insulating benefits?).

4. Ash Jackson wrote:

The idea is it's a single post and single ridge beam, both made of BFL's (big fuckin' logs).

That sounds to me as if the end of the single ridge beam will be resting on the ground at the back of the structure. Is that what you mean? Having the ridge beam sloped towards the back makes a lot of sense, but having it supported on a shorter BFL before ground level (maybe 4 or 6 feet up depending on how high the front one is) would seem to me to give you more usable space. If that's a "person" standing in the window in the drawing, that suggests to me that the single post is in the order of 12 feet tall.

Certainly if you've got BFL's around and you need a warm, dry place to store you and some stuff for winter, variations of this concept show up in survival and simple shelter books. If the alternative is freezing, who cares about head room! However, it seems like it would take work and effort to build, so if it were me, I'd try to build it to both last and be functional.
 
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I see it as a first shelter, without heavy machines.  Maybe a small tractor, maybe just rigging to move logs.  Cover with slash and sawdust to make a mound that will hold the tarp and maybe a little dirt to hold the tarp.  Enough to be shelter, not a big investment in time or materials.  Way easier to heat than a tuff shed, and just as fast.
 
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An equilateral triangle is one of the strongest shapes in the universe, so in that regards it does have merit.  If the front wall is plumb (vertically straight), then the leaning post (if J's thinking is correct that you meant a single beam going downward from the front post), then that beam and all the weight on it is going to work against your post and the vertical nature of your front wall.  If you have two posts, and a single beam, then the structure, supported by two equilateral triangles, has a lot more integrity to stay upright as built.  This all is necessitated by having the posts placed so that they can bear the weight of the beam.  

   
 
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I like the idea. There are many issues to work out. From my point of view I think a non living roof may work better. I think one could use vines on the steeper angles and build in access to the top of the roof.
 
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My ideas may unnecessarily make a simple build a lot more complicated, but potentially more "user friendly", over the long term?

Perhaps the addition of full length "dormers" on each side could solve the height issues. Essentially the dormers would be two additional triangles on each side, at loft height. One might consider the addition of windows that open for cross ventilation when temperatures rise.

Could terracing on the sides solve the steepness/soil slumping issues?

The dormers would provide significant light, headroom in the loft and a flatter surface up top (garden?). The terracing could essentially be a combination of swales and hugleculture beds leading up to the windows of the dormers.

Might be worth cladding in metal or tin to exclude rodents, etc.; and a potentially more waterproof barrier, that would add to structural integrity.
 
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Daniel Ray wrote:There must have been something in the air...



Definitely something in the air. I mentioned a spiral wofati to Josiah the other day (in the spirit of small, fast, a-frame design).

Ya Ash!
 
Nicole Alderman
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Jay Angler wrote:

2. What kind of height are you thinking about - tall enough for a loft? That will solve some of the head room problem on the first floor and sleep's one of those things you don't need to do standing up!



I know Paul generally doesn't like going below soil level for structures, for all sorts of reasons. But, I think the greenhouse has the standing floor about 3 feet below soil level. What if the wall extended straight down about 3 feet. If couches and counters lined the walls, you'd never be standing where the wall meets the floor amd bonking your head.

Doing it this way probably is a lot more complex than a simple A frame, though...

Below is my HORRENDOUS photoshopping, done with sleeping child in my lap, and with heavy use of the "clone" tool because I can't move much with said sleeping child in my lap!
worst-photoehop-a-frame-wofati2.jpg
[Thumbnail for worst-photoehop-a-frame-wofati2.jpg]
I also have flux on my computer, making everything orange and sleepy, and so I don't even know if the sky is blue, hahahaha!
 
Jay Angler
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Nicole Alderman wrote:

What if the wall extended straight down about 3 feet. If couches and counters lined the walls, you'd never be standing where the wall meets the floor amd bonking your head.

Doing it this way probably is a lot more complex than a simple A frame, though...  

Exactly! Essentially you're suggesting a below grade level "knee wall" which improves the issue of low height "dead space" which still needs to be cleaned and heated, but may defeat the "almost instant" housing bit.

I've met two "A" frame chicken coops in my time and they look like a great idea until you realize how hard it is to clean where the roof part of the "A" meets the floor and just how much of the coop has less that 2 ft of head room which a 6' guy is trying to clean out. I'm relatively short, and I wouldn't want to deal with them.

The best I can think of with an A-frame human-sized building is to do what was done in my Mom's house with a pair of attic bedrooms - the first part of the tight angle was boxed off and insulated. The next part of the angle was a series of cupboards with 3 doors that were about 5 feet high at the front and maybe 3 feet at the back. The opposite wall had the "full length dormer" as Lorinne Anderson suggested. A dormer tends to be associated with "window" but in fact Mom's dormer only has 2 spaced windows, but they are large enough for me to climb out of so they'd qualify as fire egress. The downside is that the dormer has essentially a flat roof which has caused problems in the past, but with modern sealable roofing membranes, it hasn't caused grief recently.

I'd do a light weight "mock-up" of the proposed A-frame with sticks and tarps and compare that to the 'berm shed' structures being built at the lab and consider the usable space under each balanced with the human energy it takes to build the two structures for real and add extra time to front in the berm shed and consider the pros and cons and go from there. We have to also consider that "cute" goes a long way to giving a person a sense of "home" that a square box may lack, despite how efficient it may be to build a square box.
 
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if i was playing with this idea- i would have that top section of A frame jutting upwards from the ground/berm.

so down a little, and a lot of earth berm ing and build up a hill, but the very top visible as a tiny A frame rising up .....

make this level all greenhouse like with big lofts for plants and lots of vertical growing...but have stairs that lead down to the bottom level, all underground, invisible from walking up to it.
 
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Chris Kott pointed out that maybe a built in sediment catch would be good for the living roof. I think it’s a good idea. My thoughts may not be in the true A-Frame spirit but what about an angled wood storage lean-to on both sides? It would be a nice place for the soil to bank up for healthy growth and take care of the dry firewood situation too!
BDA0819D-7A47-453B-9866-5D1B1CE60CDF.jpeg
Don’t forget the firewood!
Don’t forget the firewood!
 
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Page 56 of Mike Oehler's '$50 and Up Underground House Book' shows an A frame design for a flat location. Depending on slope you can excavate as needed for soil to cover the roof. You can also excavate a slope out to daylight for drainage. The main issue with 1 big beam over 1 big post, similar in size to the Cooper Cabin main beam and posts for example, is safe handling of the weight. Minimizing cost with say a single day of heavy equipment rental to get the freshly cut trees into position, you'll have to rent something pretty large. Might be simpler to stick to smaller logs, with more than one post, and use much smaller equipment.
 
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I see less and less soil on this,  which is a good thing.
It lowers need for labor and  huge logs.
The way I figure it, the soil is there to protect the whatever moisture barrier is being used, specifically tarps, plastic sheeting or pond liner.

Now,  soil inside the envelop can be thermal mass.
That's what I would tuck into the otherwise hard to use corners.
Rather than digging down at all,  I think raising the grade would be a better way to create low walls.

Rising damp could be real issue.
Dig  a "moat", use the soil to create a raised earth foundation,  add a moisture barrier on top of that.

Going over the math,  I can find no compelling reason to choose two huge logs over more not huge ones.
To get the same amount of 6 foot high interior space you have to make the vertical leg higher and higher, and the leaning one as well.
 
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In spirit of novel A-frame-ish designs, my plan for the first serious build has been a green roofed A-frame ever since this video I saw last May



Well it's a flat topped A frame anyways.  

About the same frame as is filmed, except probably a bunch of on site milled siding instead of paneling, and the roof will be green.  

The only significant deviations from "traditional" lined green roofs I think, will be throwing down dollars for stainless steel flashing, sourcing quite a few loads of halfway rotten scrap dimensional lumber of 1.5" thickness to lay up and down the whole length of the roof, and then transplanting some of the horrible, the terrible, the awful, English Ivy along the sides of the house, where I will have made a fancy fertilized irrigated planting bed for them to make that whole thing a living surface in 4 or 5 years instead of 20.  

Once mature, the scrap dimensional lumber and English Ivy will have made a sturdy few inches of soil and vine, then the structure can officially be called Wofatish.   But it's not done, the next step is to begin working in some more soil into the ivy mat, and chucking all kinds of cool wet season growing seeds on it, and let grow what will.  

It seems that if the building is only that size, and it is also edged with a total darkness thicket of sword ferns, pruning that Ivy patch once a year would pretty much be a cinch.  

It'd be nice to have something sweet smelling or tasty or otherwise useful as a living surface right away, but English Ivy is the only A++ I know for the criteria of evergreen rain erosion control and vigorous climbing/root matting growth in marginal soil and water conditions.    

Hope to start on this before too many months go by, but Operation Paddy Terrace and the rest of life are going to have to happen first haha.
 
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Good ideal.
 
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Oh I watched that video not too long ago!  I love this idea, I've always had a fondness for a-frame buildings.  Solid earth berm houses don't allow for nearly as much light as I'd prefer, especially in the short winter days we get on in this region.  Would combine the best of both worlds!
 
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I had this idea in 1990 for a lot that was steeply sloped above the roadway.  To excavate parallel to the road and put the dirt above the excavation. Then build an A frame building along the excavation with an intersecting A frame in the center that would extend back into the hill and out toward the road. Where the A frames intersect makes a nice open space. I was thinking of adding solar collection to the wasted space at the peak of the A frames. Solar panels would pump water from tank in the section of  A frame extending back into the hill and fill the collector tubes in the glazed peaks.
Aframe.png
underground A frame cross
underground A frame cross
 
William Bronson
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The A frame does seem to lend itself to a transparent peak.
I wonder if that space could be treated as a low thermal  mass sun space:
https://www.builditsolar.com/Projects/Sunspace/LTMSSGuide/LTMSSGuide.htm#What%20Is
 
William Bronson
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I'm realizing just now that I'm not clear about some physical principles of buildings.

Is an A-frame structure better at resisting the weight of bermed earth than a vertical sided structure?
If so,  is it it due to the the slope of the soil supporting wall,due to the buttress provided by the opposite wall, both, or something else entirely?

 
Hans Quistorff
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The sunspace is exactly what I was talking about. As for the A frame verses vertical wall it has the advantage of the bottom of the wall not pushing in from the earth pressure therefore placed on a dry stack foundation instead of being berried. The inward pressure in the center would be greater but less than on a flat celling. A lower cross bar on the A puts the load into compression but reduces the height of walkable space.
 
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William Bronson wrote: I'm realizing just now that I'm not clear about some physical principles of buildings.

Is an A-frame structure better at resisting the weight of bermed earth than a vertical sided structure?


Generally speaking, yes.


If so,  is it it due to the the slope of the soil supporting wall,due to the buttress provided by the opposite wall, both, or something else entirely?


Mostly because an Equilateral triangle is a better approximation of an arch than a square or rectangle.
 
William Bronson
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Mostly because an Equilateral triangle is a better approximation of an arch than a square or rectangle.



Would a gambrel roof be closer still?
I was thinking that using  two or three attic trusses placed directly on top of a stem wall or the foundation itself could make a great A frame building.
A gambrel roof is an obvious extension of this.

Obviously, these forms of construction are more complex than one post and one beam,  but I think you could also build the without heavy machinery.
A roundwood approximation of either seems doable.


Imagine a pitched  roof,  set on the ground,  gables facing east/west, the slopes facing north/south.
(Edit): pretty much what Hans describes above.
I like the idea of standard trusses on the endwalls with attic trusses in between.
The entrance could be on the south side,  built into a attic truss or gambrel dormer, again much like the idea Hans Quistroff presented.
You could use all standard trusses, for strength and simplicity, and cut man sized doorways where needed.
I'm not sure what the spacing for the tresses would need to be,  but there are tables that could be used for that calculation.

I like the idea of  metal roofing,  but I'm wondering if aluminum flashing would work.
 
William Bronson
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So here's a take on the bermed attic truss house:
6f88caf9e540839ad1ad7e9476186560.jpg
A rather twee garden shed
A rather twee garden shed
 
William Bronson
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Here's a much more robust version, DIY,  half buried,  with active solar heal collection in the form of an air to earth heat exchanger:
http://www.ecosnippets.com/gardening/swing-set-repurposed-into-underground-greenhouse/

swingset-into-greenhouse-5.jpg
Semi Undrground A Frame Greenhouse
Semi Undrground A Frame Greenhouse
 
Jay Angler
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William Bronson wrote:So here's a take on the bermed attic truss house:

That is totally adorable! However, judging by the height of the chair, it also demonstrates my point about head-room, despite having closed off and bermed the shortest part of the triangle.

It's a balance between having the slope gradual enough to berm effectively vs steep enough to be like the A-frame in the video above which had no head-room problems of note. To some degree, it's also what you plan on doing with it. If the goal is just to have a warm place to sit and sleep, built quickly out of what's at hand, less head-room may work.

The second picture William posted while I was typing has more headroom, but will need creative work to get dirt and plants to stay on the sides. I think it can be done with support or by simply going far enough out from the building, but that depends on one's overall site plan.
 
William Bronson
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Looking back at the original sketch,  Paul was envisioning something about 14 feet tall and maybe 18 foot wide at the base.
The length of the ridge beam is hard for me to judge.
This scale means more room to spare inside.
I still don't love the need for big logs and big machines but it should be roomy enough for a tiny house.
 
Creighton Samuels
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William Bronson wrote:


Mostly because an Equilateral triangle is a better approximation of an arch than a square or rectangle.



Would a gambrel roof be closer still?



Probably, but the details do matter. Particularly the equilateral part, as the image with the earth bermed shed looking thing is not an equilateral, as the angle of the roof is too wide.  The side of the triangle that is the floor is still a neccessary part of the shape.

An equilateral pentagon should do even better as an approximation of an arch, but this would mean that your low sided wing walls still wouldn't be straight, but instead slanted out; and the junctions where the walls meet the roof sides would need to be every bit as strong as the beam junction on an A frame.  This is where the advantages start breaking down, because this is not true with a traditional roof on top of a traditional plumb wall.  Even in the case of load bearing plumb walls, the junction between the wall and the roof is quite weak, as the junction typically only needs to be strong enough to keep the roof from shifting in a hard wind, and the structure depends upon the weight of the roof sitting directly on the plumb walls to keep the structure in compression.  This is not, and should not be expected, to be true with a bermed home of any shape.  Every juction must be very strong, and strong juctions are expensive, so the more that you design into it, the greater your costs will rise.

And this is also why the A frame is such a popular form of traditional cabin; the strong junctions are minimumal, with only the roof beam and the ground anchors being necessarily strong.
 
Jay Angler
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Creighton Samuels wrote:

Even in the case of load bearing plumb walls, the junction between the wall and the roof is quite weak, as the junction typically only needs to be strong enough to keep the roof from shifting in a hard wind, and the structure depends upon the weight of the roof sitting directly on the plumb walls to keep the structure in compression.

There are places where the "weight" of the house was all that was used to keep the house on the foundations! This can be a *really* bad idea in areas with tornadoes, hurricanes and earthquakes. Most modern building codes have rules about fastening walls to foundations and roofs to walls and I've learned that I'm often further ahead to build "better than code" due to some of the "gusty, energetic" storms we get. I've got a "temporary" processing shed which is a modified portable car shelter with large spikes holding it down and a guy line at one front corner as there isn't a good place to put a second guy for the other corner. We had an atypical wind direction with big gusts the other night and the spikes are several inches out of the ground. Since "temporary" is clearly going to be another year at least, I've *got* to find a way to fasten that second front corner. (Both back corners are guyed, but they're also sheltered from this sort of wind event - so it's interesting how Mother Nature will find the one weak link!)
 
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Check out this Swedish "eco-lodge".  Scroll through page and see mini- a-frame cabins.

https://www.wildsweden.com/kolarbyn-ecolodge



 
Hans Quistorff
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jack vegas wrote:Check out this Swedish "eco-lodge".  Scroll through page and see mini- a-frame cabins.

https://www.wildsweden.com/kolarbyn-ecolodge


 
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side view
quick-a-frame.png
[Thumbnail for quick-a-frame.png]
 
paul wheaton
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3 BFLs.   And then a bunch of logs for the sides.  And then the membranes.
 
leila hamaya
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i played around a bit with the idea i was having earlier in this thread.

actually i've drawn a few quick sketches of a few versions...but didnt get too far with any of them.
anywho this is a bit off the side of the original idea, much more intensive ...and this is way too big too, needs scaling down, but...for anyones food for thought...

i drew some of my ideas out.... the AH FRAME , i will call it...with an H underneath the A to hold it up high.
an AX FRAME would also work, although not as good sounding =)

AHframe.jpg
[Thumbnail for AHframe.jpg]
 
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There are lots of cool and interesting ideas here, but many of them get away from the original concept of fast and easy/simple to build. If you are going to use it primarily for a place to shelter and live while building a final house, you don't need to spend time and energy on a big structure with amenities. (I am of course thinking about a single person or a couple, not a large family.)

Along the lines of easy and cheap to build, I think bfl's are problematic. Maneuvering them, even if near the building site, is dangerous and strenuous without skill and/or machinery. Renting an earthmoving/log-placing machine will probably take a good chunk of change up front. Making a diminishing series of medium-sized log triangles say 2' to 4' apart going back into the earth, and then laying a single log on top as a ridge, is doable with no equipment and in easy steps. Then small logs ("junkpoles") can be easily laid horizontally across the A-frames, and waterproofing and insulating layers in succession. Not as cool as bfl structure, but much more accessible to the ordinary person without a backhoe on hand. Also, if secondary logs are to be laid up against the bfl main frame, the height of those secondary logs will be such that, to hold up any amount of earth cover, they would have to be strong enough to hold up the ridge beam all by themselves. So no need for bfl's in the completed structure.

If there is any slope, placing triangles heading uphill from the opening, and then digging out the usable part of the slope between them (so that there is a minimum 5 or 6' of headroom), would give the best bang for the buck. It gets the earth you need for cover and simultaneously reduces the amount of structure to be covered. Then digging a swale well outside the structure line and using that for more cover helps with drainage.
 
Glenn Herbert
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A crude sketch (first time I have used Paint 3d and don't know if there is a way to make straight lines yet) of my concept.
aframewofatish01.png
A-frame wofatish with easy-to-handle logs
A-frame wofatish with easy-to-handle logs
 
paul wheaton
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I feel like the post and the ridge log will both need to be BFLs.
 
leila hamaya
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yeah those are good point, and good idea, that would make it simpler and more stable. so bigger roof, a less steep angle, and that roof is much wider than the underground part, with the row of roof trusses being supported by the undisturbed ground level soil, or top of the subsoil, and the underground part only being a small area underneath the squished A
 
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