MYOG "ultamidish" pyramid tent

[Milan H]

Hi,

Warning, long post. First of all, I would like to thank Jerry and all others for great information provided here. It is my first bigger project and without experience shared here, I would not start with MYOG.

I wanted to post the outcome due to several modifications to basic design I made and would like to share my impressions. Mostly to help others in the same situation, thankful for all the info as I was.

Basic information:

• Size: 275 x 220 x 160 cm (108 x 86 x 65 inch), “ultamidish” design
• Materials: fly – 40D silnylon from Extremtextil, Inner tent: 20D mosquito netting, 20D inner tent fabric, 70D PU coated nylon
• Weight: fly – 750g (26,4 oz), inner tent – 450g (15,9 oz), additional lines + stuff sack – 50g (1,7 oz), comprehensive set of stakes, trekking pole connector + stuff sack – 170 g (6 oz)

Modifications to basic design:

• Non-square dimensions: The goal was to decrease footprint size. It brought a bit more complexity to the design by 2 different sizes of basic triangles. I made a paper model with numbers of basic triangles. That helped with orientation. I also made full scale model (pattern) of each triangle from old drawings at work, taped together. I used these to ensure all sides to be sewn together would match lengthwise. It required some extra work at pattern making (1/2 hour each I guess). But I found cutting silnylon to appropriate dimensions in such sizes quite hard and this way led to good results – no disproportion at either long seam.
• Large vent: It added a lot of work compared to vent-less sides. I found that it does not terminate condensation issues, but helps. I noticed much more moisture buildup inside the vent than inside the tent, most likely caused by up flow of warm air at night and condensation there. It also added some weight.
• Flat felled seams: after some research, I decided to try to make flat felled seams instead of “faux felled seams” with one row od stiches trough 2 layers of fabric only. The only way to do that was to pre-fold Silnylon into wanted structure and pin a lot. The result is not perfect. Silnylon slips a lot and in a lot of places I can see that stitches are trough 3 instead of 4 layers. It was also a lot of work, probably increased time spent on the project by 25-30%. I would not recommend this. Next time, I will go with “faux felled seam” with 3^rd row of stitching.
• 3^rd line of stitches: As suggested by Roger to enhance strength. I believe it does as advertised and does not take much time. I will use it again.
• Non-right angle basic panels: I wanted to prevent raised centers of the sides, therefore I added 5 cm (2 inch) of length at side center seams, creating non-right angle basic triangles. It only increased the time in pattern making stage and I believe it does what was intended. The difference in gap at corners and side centers is much less apparent. I am quite happy with the result. On the other hand, it may lead to more slack pitch of some side, especially on uneven ground.
• Cat cut deflection 5 cm (2 inch): You can see the results from the photos. I researched thoroughly and found differences in recommendation (2-3,5 inch). If I would be to replicate this mid design, I would probably use a bit more (2,5-3 inch). The outcome is OK for me, but I prefer more taught pitch and possibly quieter shelter in higher winds over more interior room. My feeling is that it also depends on particular silnylon and its stretch.
• Zipper storm flap: I know, most of you say not needed. I was a bit skeptical so decided for it. It adds a little bit of weight and complexity. But I like the looks and have more confidence in the shelter.
• Tie downs at centers of each side (ground level): I included those despite Jerry stating he got rid of his eventually. So far I see them good if you need to batter down when it is windy.
• Tie downs at side panels and corners: I included tie down at each side at 1/3^rd of each seam length and at the same distance in corners. I have tested my shelter a bit in windy conditions and my observation is that for corners, it is rather low. Since then, I added one more tie down at ½ of the corner seam. This seems to reinforce the corner much better and I would use this location on next mid project. Now I use both (2 points connected with line and then anchored).
• Laminated reinforcements: at the corners tie downs, at tie down location in front panel and at mid peak, I reinforced the places with second layer of silnylon, laminated by standard undiluted silicon. The places seem robust. It nevertheless has certain weight penalty.

I understand that for many of you, this project is far from UL. True. The reason for higher weight are additional features, more heavy duty fabrics (40D fly and 70D PU coated floor of inner tent) and the inner tent which I made due to my signifficant other (not willing to sleep in open shelter).

I have spent about 15-20 nights in the shelter so far (Fagaras Range in Romnia; Altaj Range in Russia, Siberia). Some of which in quite demanding conditions. Some nights the wind gusts were pushing the limits of this shelter in my perspective.The tent survived. Trekking pole connector I made from unknown piece of aluminum not. Severe wind gusts snapped it in half. The forces a center pole has to endure in such situation, especially with wind gusts coming from different directions, are incredible. I emergency repaired it and used 2 more trekking poles to reinforce the center pole + had to stay in more sheltered spots. I use much stronger pole connector since. Only strapping 2 poles together for such conditions would be a joke.

Overall, I expected there to be deflection of sides in winds, which there is. I gained some confidence in the shelter, but can see its limits. It can cope with harsher conditions, but is not ideal for above tree line use when high winds can be expected. For exposed terrain, I have already started to build another  more sturdy tent and plan on updating this one with perimeter netting and using it in less demanding conditions.

A couple of pictures: first pitch + some from the field

Milan

 

[Jerry Adams]

That looks really nice

I don’t see a reason not to do Faux flat felled seam.  The first row of stitches is more just to align the two pieces of fabric, easier than using pins.  Then do 2 more rows of stitches to make sure it’s strong enough.  Especially for amateur sewer (like me) sometimes some stitches are screwed up a bit so the other row will back it up.

My current mid has a bunch of tie-outs at mid panel that I experimented with but don’t use.  I think that having tie-outs on each corner and 3 on each side in between at the bottom is the best.  Normally I only use 1 of the 3, but if it’s really windy I’ll use all of them.  Then, there is even pressure on the side of the tent.  If there’s a tie-out mid panel, then it’s sort of slack underneath.  But I think most people don’t agree : )

 

[Matthew / BPL]

Wow! That looks great! I don’t MYOG but it is very interesting to hear about the process. Thanks for sharing.

[Ken Thompson]

Really nice!

Where do you source your fabrics?

[Milan H]

@Jerry: Now I understand, but I had to learn the hard way. It was really pain in the neck to do it the way I did. No more. Having 3 tie outs at center panels is an interesting idea and I see how it can even the panel stress in high winds. Even the one at 1/3  and one at the bottom reinforce the structure significantly. In the corners, 1/3 of the corner length does not reinforce optimally. In higher winds, the corner bulges too much in my opinion. Having the one at 1/2 of the seam seems better (or use both, when the conditions are worse). I wonder whether a more pronounced cat curve (3 inch) would change the corner behavior I see in my tent.

@Ken.T: I am from the Czech Republic, so I sourced materials from Extremtextil (DE). For my new project , I bit the bullet and sourced key fabrics from Rip-stop by the Roll. They are on its way. I really like their Silpoly and Extremtextil does not have any alternative to that.

[Jerry Adams]

I got some silpoly from RSBTR but haven’t made it yet, that seems like great material

[Opogobalus]

Looks great! Have you used a mid from another manufacturer before? Curious to know how effective the larger vents are.

 

What’s the next project? :)

[Jerry Adams]

Just one person’s opinion – I’ve tried vents and they didn’t seem to do much

If it’s not rainy and wind blowing from the wrong direction, I leave a door open.  That’s much bigger than any vent.  That helps some.

[Milan H]

@ Jonathan: No, this is my first Mid, so no comparison. Jerry is correct, not even quite large vent like I used is sufficient. But it helps in my opinion. Open door and/or sufficient gap at the bottom help more.

With bottom raised 8-10 cm and closed door it outperformed dome tent (with only little vents) you can see in one of the photos above by a league. Only a little/or almost no condensation most nights compared to dripping/inner tent wetting heaps of water.

Next project: tent supported by 4 trekking poles, similar to new Tarptent Saddle 2.

https://www.tarptent.com/saddle2.html

But the ends will be closed by solid triangle. That will simplify pitching and also make the tent much more wind worthy. Also the construction of the sides will be different. I want to make sturdiest trekking pole supported tent I can. Then I see whether it is sufficient for my needs, or I have to make a Caffin tent :-)

Milan

[Jerry Adams]

you are addicted : )

[Milan H]

Most likely..Making gear just adds another dimension. I work as an engineer in a big corporate, these small projects give me the possibility to do it MY WAY :-)

[Jerry Adams]

same here, that is I used to

frustrating to be told how to do something in a way that will never work, then they complain that it doesn’t work

Actually, most of the time working was great, I just like to complain about when it was screwy

[Craig B]

Haha!  Yeah, I’m also an engineer.  I guess it’s not surprising this hobby attracts us science/engineering types, especially the MYOG aspect.

[Author]

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