MLD Supermid user error?

Having a hard time picturing it. Is the pole that snapped angled out along the door line?  I have an MLD XL with a half inner and the pole is vertical. I haven’t encountered high winds with it.

The pole is vertical. By tying off the top of the tent, it secured the top of the pole. I think normally, the top has a little give and will sway with the wind. The wind rolls off. Something has to give. With the top and bottom of the tent and pole secure, it trapped the wind in the middle section. The pole bent in the middle and snapped.

Prevailing winds on my end of the plains are from the south or west, best to have the door facing north or east. Not sure why but the solid sides have less deformity than the door/zipper side, less stress on the pole too.  I’ll use all of the tie outs, winds here have been up to 74 mph. Gotta love National Grasslands.

I had a second door added. There are no tie outs on the door sides. I’m considering adding some.  Maybe doubling up the lines in the corners at 90*.  I do believe tying from the top trapped the air.

Edited to say that once the pole started bending, the top lines and the windforce may have kept it from going back to straight with a final gust of wind taking it out.

The winds here are predominantly north / south with some coming through the mountain passes to the west.

In a pyramid shelter, the fabric is supposed to behave like a tensioned membrane, and the center pole is supposed to remain a mostly axial compression member. Once unsupported panels deflect inward and go concave in wind, those panels stop transferring load efficiently to the perimeter stakes and redirect load into the pole. That changes the pole’s job from straight compression to eccentric compression with bending, which is exactly where a light carbon pole becomes much more vulnerable.

Large unsupported panels are often the weak link (I talk about this in detail in this course) in a storm pitch, especially when they sit between well-secured top and bottom anchors. The top can be locked in by apex guylines, the base can be locked in by corner and lower edge tie-outs, and the fabric span in between becomes the zone that “oilcans” inward (I wonder if younger people still know what this means?!). When that happens repeatedly in high winds, the pole is subject to dynamic side loading instead of stable axial load (dynamic loads can slowly break little bits of fiber in the carbon pole – death by a thousand papercuts – until one big gust sends it to its grave). That’s not to say that dynamic is what happened here (one catastrophic gust can do it as well), just that it’s one of the failure mechanisms we are trying to eliminate when engineering a tent.

Even though the pole is the part that broke, the root cause was probably panel instability, which created a lateral load path into the pole. (Note: peak guylines will help reduce apex wandering a little, but they won’t stop a big side panel from collapsing inward and levering the pole sideways.)

As suggested, the most effective fix is to improve support at the location where the deformation actually occurred. In this case, that likely means adding or using tie-outs that restrain the middle of the door panels, especially on the windward face, so that wind loads can be carried back to the ground rather than into the pole.

I would treat upper (apex, vent, etc) and lower edge guylines as secondary tuning tools. They may improve overall stability, but if the doors are the panels going concave, then better mid-panel support is probably the real fix.

Thank you Ryan. That clarifies it a lot. A pretty good description of what happened, except the ferrule appeared to take the brunt of the damage.

My original thought was reinforcing the middle. I was hesitant wondering why tie outs were left off of the doors. I guess normally they’re not used on doors. I’ll add one, maybe two on both sides of the zipper.

I’ll keep the apex lines. Maybe try doubling them so I’ll have four to even out the tension.

I was able the field “repair” the pole using the broken ferrule. Ron is sending me another section, but it’s working. Bundled it with a shorter pole for better stability. Redid the lines on the corners.  Apex lines are for when doors are open.

Verisitle.

I’m liking this tarp.  A couple ties across the zipper maybe to cut down on stress.

MLD Acquisition

wow. makes me want to grab a custom burn while I can