Why shock cord for rails on the sides of an UQ?

**DemostiX** · 10-30-2011, 21:34

Where is shock cord needed on an under-quilt (UQ)?

The ends of a gathered-end hammock vary in width between set up and use and during use, so the role of the elastic to have the width of the UQ ends track that width is clear enough, I guess for sealing against intrusion of air.

An elastic suspension stretches the UQ out and up to rest loosely against the hammock bottom.

But , what is the purpose of the 4 yards of elastic within the two channels of a full length UQ, when there would seem to be plenty of static and dynamic adjustibility from the rest of the shock cord running up and out to hammock ends?

I'm pleased with the fore-and-aft sliding on rails with the side channels. But, I'm not understanding the role of the elastic as the rail.

WV · 10-30-2011, 22:29

Originally Posted by DemostiX

Where is shock cord needed on an under-quilt (UQ)?

The ends of a gathered-end hammock vary in width between set up and use and during use, so the role of the elastic to have the width of the UQ ends track that width is clear enough, I guess for sealing against intrusion of air.

An elastic suspension stretches the UQ out and up to rest loosely against the hammock bottom.

But , what is the purpose of the 4 yards of elastic within the two channels of a full length UQ, when there would seem to be plenty of static and dynamic adjustibility from the rest of the shock cord running up and out to hammock ends?

I'm pleased with the fore-and-aft sliding on rails with the side channels. But, I'm not understanding the role of the elastic as the rail.

A couple of guesses:

(1) Just as the width varies in use as the occupant moves around, the effective length can change, too - though perhaps not as much.

(2) Desperation

**Knotty** · 10-30-2011, 22:41

Also so the UQ suspension length doesn't have to be so precise. With no stretch you'd need the suspension length to be spot on. Too short and the UQ wil be carrying your weight. Too long and you've got gaps.

I don't see the need for the full length being bungee. At home, for my Brazilian, I use bungee only at the two ends.

**DemostiX** · 10-30-2011, 23:27

Originally Posted by Knotty

Also so the UQ suspension length doesn't have to be so precise. With no stretch you'd need the suspension length to be spot on. Too short and the UQ wil be carrying your weight. Too long and you've got gaps.

I don't see the need for the full length being bungee. At home, for my Brazilian, I use bungee only at the two ends.

My question is only about what you exclude in your second paragraph, the part that is acting as rails. I can understand that only makers for gram-counters, a Z-packs, would swap out the length of shock cord in the channel for a length of something lighter, but that is exactly what I am driving at, if an ounce can be saved and nothing at all lost. (I might even bury the shock cord in a nice continous splice.)

I'm much taken with your observation-- with others -- of the sealing problem of UQ's. I'm trying to appreciate just what shock cord is supposed to do, as obliquely as the forces of the UQ suspension are applied. Before butchering a fine continuous stretch of shock cord on a full length UQ, I wondered what functionality I'd be giving up.

RAB closes the stuff sack for the Quantum top-bag with shock cord, including a very nice (or over-engineered) stress-stopper and then a keeper for that stress-stopper. Wow, no expense spared. Then, of the shock cord, I wondered: "Why? What need does this meet? In my limited experience, I haven't noticed shock cord on a stuff sack closure before. What did I miss out on? "

**FLRider** · 10-31-2011, 05:13

I can not speak with personal experience here, as I don't have an underquilt with shock cord as the runner through the side channels. However, I can speak obliquely to it, from the other direction.

With my PLUQ--which is, admittedly, a 2/3 quilt--the side channels can be somewhat uncomfortable to push against if I am on an extreme asym angle (for example, when I'm reading in the hammock with my head pressed against the edge of the quilt). I can only think that shock cord would help with this, as it would give more than the mason's line I'm using right now. It isn't uncomfortable enough for me to go through the process of disassembling and reassembling the quilt, though.

**GrizzlyAdams** · 10-31-2011, 06:50

I recently went through this same question with a DIY underquilt I made for a bridge hammock.

Aiming for the minimum weight, I put shock cord at the corners, and nothing in a side-channel, thinking (hoping) that that would tension up the side edges of the UQ and keep them closed in on the hammock.

Nope. What seemed to be needed in the middle was some lifting, that was not being accomplished just by tensioning the corners.

That led to the logical next step, to put something lighter than shock cord through the channel I'd put along the side and that might have worked except the channel is a touch too narrow to admit whatever means I used to attach the lighter weight cord (a cotton shoe string) and the shock cord. Another concern for me on this UQ was abrasion due to that knot, the UQ and channel being made of cuben.

I probably could work something out with the cotton shoestring with shock cord corners, but the time/interest ratio thing passed the inflection point where I'm happy enough with shock cord in the channels.

**Knotty** · 10-31-2011, 20:39

Originally Posted by DemostiX

My question is only about what you exclude in your second paragraph, the part that is acting as rails. I can understand that only makers for gram-counters, a Z-packs, would swap out the length of shock cord in the channel for a length of something lighter, but that is exactly what I am driving at, if an ounce can be saved and nothing at all lost. (I might even bury the shock cord in a nice continous splice.)

I'm much taken with your observation-- with others -- of the sealing problem of UQ's. I'm trying to appreciate just what shock cord is supposed to do, as obliquely as the forces of the UQ suspension are applied. Before butchering a fine continuous stretch of shock cord on a full length UQ, I wondered what functionality I'd be giving up.

RAB closes the stuff sack for the Quantum top-bag with shock cord, including a very nice (or over-engineered) stress-stopper and then a keeper for that stress-stopper. Wow, no expense spared. Then, of the shock cord, I wondered: "Why? What need does this meet? In my limited experience, I haven't noticed shock cord on a stuff sack closure before. What did I miss out on? "

My reasons for a hybrid bungee/rope suspension were twofold. First, I didn't have enough bungee for the mammoth sized Brazilian. Second, the longer the bungee the "softer" the spring, which can result in sag. Amsteel runs thru the UQ channels, selected to avoid abrasion of the fabric. My thinking is that as long as part of the UQ suspension has stretch it should provide the same result as an all bungee system.

For the end channels I have some UQs with bungees and others without. In theory and according to the Jacks you shouldn't need stretch in the end channels because the suspension bungees provide the needed movement. In practice I find that having bungees in there just works better. But still not good enough, which is why I've been suggesting the need for draft tubes.

**Danalex** · 10-31-2011, 08:05

I added full length shock cord to my JRB MW3 UQ, first for use in a BB as my left shoulder was always being exposed as the UQ would move around a bit as I moved. This made it stay up and over my shoulder without any slipping, also worked the same way for my feet. I just tucked them under and the quilt wouldn't slip off. I guess it's a situation of a rectangle quilt attached to an asym hammock.

Now I use it with my bridge and even though the shoulder exposure isn't a problem I am happy with the way it works there also.

**Shug** · 10-31-2011, 08:07

It just works for me....and holds it up to where I need it. Less fiddle as well for my needs.
Shug

**BillyBob58** · 10-31-2011, 11:47

Originally Posted by Danalex

I added full length shock cord to my JRB MW3 UQ, first for use in a BB as my left shoulder was always being exposed as the UQ would move around a bit as I moved. This made it stay up and over my shoulder without any slipping, also worked the same way for my feet. I just tucked them under and the quilt wouldn't slip off. I guess it's a situation of a rectangle quilt attached to an asym hammock.

Now I use it with my bridge and even though the shoulder exposure isn't a problem I am happy with the way it works there also.

Please check something for me while I also do some checking to see if my memory on this is correct.

With your bridge hammock, do the top edges of the UQ snug up against the side of the bridge (BMBH?) hammock, or is there a small gap? If it is snug, can you remember if it was snug on the(sides of) bridge BEFORE you added the full length shock cord?

Here is my memory which I will try to verify today: With my full length MW4 on my BMBH, there is always a small gap on the sides between the top side of the quilt and the hammock. I have actually added a GripClip and thin shock cord to pull that gap closed. What I have never been sure of is if that effects function in any way, as I have never been cold in this quilt.

However, if mem serves, when I have placed my synthetic full length shock cord "Yeti" ( torso size, not full length), the quilts top edges are nice and snug up against the hammock sides. It never occurred to me before this thread that it might be the full length shock cord accounting for this. I'll try and check to see if this is indeed a difference.

As for the exact subject of the OP, "why" bother with full length cord on a full length quilt, would the continuous adjustment capabilities allow for better venting?