seams for joining insulated panels for insulated shorts?

[Sarah W]

I am planning out how to sew a pair of rip-away insulated shorts.  Sorry this post is long, the main question about seams for joining insulated panels is towards the end.

Insulated shorts you say?? I think of warm shorts as being the equivalent of a vest but for your pelvis. My bottom layers are not easily changeable, so there is always a compromise. These shorts would be light/packable and be something that I could put on over whatever I am wearing. I also think they would add a good bit of warmth for sleeping.

Anyway on to the basic design-
I have drafted a pattern and have made a few test pairs out of old sheets. The shorts are going to overlap on the outer side seams of each leg and have snaps down the side for the closure, hence the “rip-away”. The waist is a curved yoga waistband made of spandex with nylon panels on the sides, where the snaps go.  The insulation will be 2.5 oz apex I think (I have samples coming).

An additional design component is that I do not want insulation between my legs, so rather than having 4 panels as most pants are made (front and back for both the left and right), they are made of 6 panels.  The additional 2 panels of fabric are between my legs, similar to a gusseted crotch, but they go all the way to the bottom hem of the shorts.

It is these additional panels that are causing the most difficulty.  I know that the simplest way to make insulated pants is to make an inner and outer pant, and join the inner/outer at the waist and hem. The left and right are then each joined with a simple seam, and the raw edges are inside. This would be the most straightforward way to construct the shorts, but it is not necessary to have a double layer of fabric in the inner leg.  I plan to use some softshell fabric for the inner leg panels, and doubling the thickness would add an additional 1/2 ounce, so I would rather leave it as a single panel.

So, given that I want a single layer of fabric in the inner thigh, the next obvious way is to construct the left and right legs separately, and then join them together with the crotch seam.   So this crotch seam would go down from the waist with the L/R insulated panels, through the crotch with the single layer softshell panels, and up the backside with the L/R insulated panels again.  I intend to have the raw edge of the softshell panel encased between the shell/lining layers as well. The topology and order of construction is kind of complicated to think about, but it is this seam that I don’t know how to sew.  It should be flat and not bulky and enclose the raw edges of the left and right halves.

A french seam in the crotch seems like it would leave too much of a ridge.  Would a flat felled or mock flat felled seam work to join the two insulated panels without being too bulky? I think the flat felled seam would result in 4 layers of insulation, 4 layers of shell, and 4 layers of lining.  Is there some other way to construct the shorts that I am not thinking of, while keeping my requirements?

Perhaps I am overthinking this, but these are going to be haute couture insulated shorts!  I can’t have unprofessional raw edges exposed :)

Thank you!

[Bonzo]

I can’t help you with the seams, but you had my complete attention at the first mention of “insulated shorts.” That’s literally a perfect garment for me; I’m looking forward to seeing what you come up with.

[Michael B]

Have you thought about just a simple binding over the raw edge with a piece of the material you plan to use in the crotch area? You could do that, and the then the waistband would cover over the ends (I assume the waistband is going on last, right?). That is probably what I would do. Interesting project, looking forward to seeing it.

[Steven Paris]

Portland used to have a Montbell store (sadly, gone) and I remember their insulated skirts (both synthetic & down). Would a MYOG-skirt like their Thermawrap Skirt make more sense to give you waist-to-knee insulation with no crotch seams, no insulation between the legs and what seems like to me (with zero sewing skills or knowledge!) an easier sew job?

Please ignore this if you are attached to the idea of shorts!

[SIMULACRA]

Ortovox has the Swisswool Piz Boe short. Was looking at the mens version of this just recently. Here’s some pics of the womens version. Might spark some ideas. I like how they’re fully zipped. When you said you are making yours rip-aways it reminded me of these. At first I thought that meant you were using velcro for the side panels though. Could work that way too

[Jerry Adams]

In a normal (faux) flat felled seam, you’d have 1 inch of fabric for all layers.  You sew the first row of stitches, then fold all layers over twice for a 1/2 inch flat felled seam

If  you sew all the layers with the first row of stitches, then cut all layers except the outer one to 1/2 inch, then fold over just the outer layer once, then fold all layers a second time, there’d be half as much material in the seam so it would be half as thick.

I think this is the standard way to do a flat felled seam, this is probably obvious

With thin fabric, I never bother cutting off any inside layers, I just fold it over twice.  The fabric is so thin it doesn’t matter.  I leave all layers at 1 inch.  Actually, I do 1/4 inch seam.

I just do all my crotches with a french seam, that inside flap doesn’t make any difference

[Sarah W]

Great, thanks for the ideas!  I had not come across the Ortovox shorts.  I think insulated shorts are popular with the skimo racing crowd, so it makes sense that the  Euro brands have them.  I had originally encountered a pair made my Millet, but they didn’t fit well, and then the wheels started turning… Alpine touring is actually my main winter sport.  I did consider a skirt, but when I tried one on it just rode up and ended up like a doughnut around my waist.

I think binding the seam would work and be similar to a french seam probably.  It might be true that the ridge/flap wouldn’t be bothersome at all, especially since it is a meant to be an over-layer. I had not thought of using binding there.

I also think I understand what Jerry is saying to do with the flat felled seam, to trim all but one layer to reduce the bulk.

I will try these construction options out with my test shorts!  It will be a few weeks until I get my materials, so I have time to practice.

 

 

[Link .]

Not exactly the same but there are also the HOUDINI MOONWALK SHORTIES .

[Edward John M]

The Femoral artery and crutch area is one of very high heat loss for many if not most people so why do you not want insulation there?
That weight of APEX and UL fabrics is not going to be bulky at all when sewn. Do you have an overlocker [ serger] ?

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