Down Hammock Underquilt - Ultralight, 20*F




Introduction: Down Hammock Underquilt - Ultralight, 20*F

This Instructable details how to make your own Down Hammock Underquilt for easy, efficient insulation in a hammock.

77" x 45" ("full" length)

18.2 oz with suspension.

20*F (or below) temperature rating (3+" loft)

Why an Underquilt?

In the camping and backpacking world, hammocks are becoming a popular alternative to tents. There are many potential advantages to hammocks, but one common complaint/disadvantage is the warmth of a hammock as temperatures drop. Because the hammock is suspended, airflow underneath the hammock removes heat through convection. Without proper insulation, sleeping in a hammock can be very chilly as temperatures drop below 60F. The traditional approach to hammock insulation is the same as ground insulation: an insulating pad underneath a sleeping bag. The pad is necessary because laying on bottom half of the sleeping bag flattens it. This eliminates its insulating loft. The pad+bag combo certainly works, but many have difficulty positioning, adjusting and staying on top of the insulating pad leading to cold spots throughout the night. It's also generally more difficult to get into and out of a zippered sleeping bag while in a hammock.

A much simpler, efficient and potentially warmer setup uses two separate pieces of insulation instead of the sleeping bag. First, an "underquilt" is attached underneath the hammock. This insulation doesn't have any weight on top of it, so it stays lofted and traps body heat below the hammock fabric. This eliminates the need for a pad underneath. Then, a top quilt, usually with some kind of sleeping bag style "footbox", is pulled over top to insulate above. Think of it as a sleeping bag in two halves with a hammock running through the middle.

This approach to hammock insulation is very simple to setup and use. It's also weight and pack efficient, eliminating a pad in favor of the two quilts whose weight and packed size can often be less than just a traditional sleeping bag itself.

Step 1: What You'll Need

To make an underquilt, you'll need to choose the fabric and insulation right for your application. For this project, I wanted the lightest weight possible and was targeting insulating down to ~20*F. Heavier, more durable fabrics would cost less and work just as well. You can use any breathable, calendared fabric that is listed as "downproof". I suggest browsing the selection at They can source everything you need for the whole project and had the best prices and selection I could find.


- Sewing Machine

- Sharp scissors

- Seam ripper

- Pins or binder clips

- Measuring tape


0.66 oz MEMBRANE 10 taffeta nylon - Burnt Orange - 3 yards

0.66 oz MEMBRANE 10 taffeta nylon - Moroccan Blue - 3 yards

Gutermann Mara 70 100% polyester thread - Burnt Orange - 1 spool

Gutermann Mara 70 100% polyester thread - Moroccan Blue - 1 spool

0.5 oz NS50 Noseeum mesh - 3 yards

3/8" grossgrain ribbon - 1 section (5 yards)

1/16" Shock cord - 1 section (25')

1/8" Shock cord - 1 section (25')

Mini cordlocks - 1 package (12)

800 fill power water resistant goose down - 12.2oz*

Painters tape (blue, 1") - 2 rolls

*The amount and fill power of the down you use will be very specific to your project. In the next steps, I'll go through how to decide how much you'll need. I purchased mine from by the pound since I needed enough for both an under and top quilt. There are plenty of sources by the ounce such as,, and others.

Step 2: Planning

Everyone's perfect underquilt is different. Length, width, weight and temperature rating are the basic considerations, but this involves more variables than you can shake a stick at. You'll need to decide on total length and width, suspension type, baffle style, baffle height, target loft, down fill power, overstuff, etc. To keep things simple, I've just described my exact project here, but there is a lot of information available on all options on the Internet. I strongly suggest reading through as there is an absolute wealth of information on all things hammock there. I was only able to do this project because of hammockforums.

The style I chose is very popular and very similar to purchasable products on the market. This style has vertical, differential cut baffles. To make a quilt like mine, you can start by making a copy of this spreadsheet and entering your own numbers: CatSplat's Underquilt Calculator

My quilt dimensions in the calculator are:
Length: 77

Width: 45

Baffle height: 2.25"

Chamber height: 2.75"

Baffles: 9

Down fill power: 800

Overstuff: 5%

I added 2.5" seam allowance on the inner shell and .5" on the outer shell. Details of why will be later in the instructions.

Step 3: Measuring / Cutting

Once you have your material dimensions calculated (including seam allowances):

- Lay out the inner shell fabric on a flat surface (This was the orange in my case).

- With calendared fabric, one side is shinier than the other where it was rolled flat. This shiny side needs to face the down insulation. Lay the shiny side up when taping out your pattern.

- Use painters tape to mark the outer borders of the shell. Be sure to account for your seam allowances here.

- Use painters tape to mark your baffles as well. The tape only serves as a guide and will peel off easily after sewing the baffles in place. In these images, you'll see I used clear scotch tape, but this is only because I ran out of painters tape. The painters tape works much better. It's much more visible, easier to lay down and easier to peel off after sewing (even if you sew through it accidentally).

- Once all your tape is down, measure all your sides and baffle spacings again to be sure everything is correct.

- Cut the pattern out by sliding a sharp pair of scissors along the painters tape border.

- Repeat these steps for the outer shell (blue for my project).

Notice in the pattern calculator that the *outer* shell has larger baffle spacing and is overall wider than the inner shell. Also, the two baffles on each side are larger by the size of one of the baffle walls. This is because of the rounded shape of each down chamber. You want the inner shell to lay flat against the hammock and outer shell to puff up and provide the loft. If you don't use this "differential" cut, the chambers will compress when pulled against the hammock reducing loft and insulation.

Step 4: Hem the Shells

- For both the inner and outer shells, fold the unfinished edge over about .25" (onto the same side with your baffle tape - the shiny side) and sew a simple folded hem.

- On only the inner shell (orange in my case), fold down the corners another inch and sew them in place. This will give nice finished edges to the shockcord channels you'll create on all four sides later.

Step 5: Cut the Baffles

Credit to Joe Brewer for this ingenious method of cutting the baffle material.

- Measure the length your inner shell as is to determine the length of your baffles. Add a couple inches for margin. You can cut off the excess later.

- Lay out the noseeum mesh fabric and measure to the length you need. I measured and cut off a length of about about 82" (by about 62" - the stock width of the fabric).

- Carefully roll up this material along the length (the 82")

- You should be left with a tube of noseeum ~62" wide (the stock width of the fabric).

- Lay the tube on a hard surface and hold it in place with books or other heavy, flat objects.

- Cut off the uneven end of the tube so that you have a nice straight edge on one end.

- Measure from the straight edge and mark the tube at your desired baffle material size. This is baffle height + 2x your seam allowance. I wanted a 2.25" inch finished baffle and used .5" seam allowance so: [2.25" + (2 * .5") = 3.25"]

- Cut the tube at your mark.

- Unroll the cut material and you should have an 82" x 3.25" baffle. Repeat for as many baffles as you need. I needed 8 to create 9 chambers.

Step 6: Sew Baffles to the Inner Shell

- Sew the mesh baffle material onto the inner shell along your tape lines.

- Fold the mesh over .25" and sew through two layers for added strength.

- Keep the shell material taut, but do not stretch the mesh. This takes some practice, but if you stretch the baffle, it will tend to draw up the shell material after sewing (shortening the quilt on that baffle line).

- A piece of painters tape placed (baffle height + seam allowance) away from your needle makes a simple guide to keep your baffle height exact as you sew.

- I sewed each baffle about 3" at a time. It was time consuming but was the easiest way to ensure both shell and baffle stayed exactly where I wanted them.

- The mesh had a natural tendency to roll in one direction. Do yourself a favor and fold your seam the same way or you'll be fighting the material all the way down the baffle. It doesn't matter if you fold this seam under or over.

Step 7: Sew in Grossgrain Loops for Suspension

This quilt has a "secondary suspension". This just means there are loops at each corner for a small piece of shockcord to attach to the long primary suspension. This lets you adjust exactly where the quilt will sit on the primary suspension. Without it, the quilt tends to slide and shift toward the middle of the hammock potentially reducing coverage or creating air gaps.

1. Cut 4 lengths of grossgrain ribbon about 7" long.

2. Fold the ribbon in half to create a loop on one end.

3. Position the loop so that it protrudes about 1" from the end of the quilt.

4. Position the loop about 1" from the long edge of the quilt as well. When you fold this over to create the shockcord channel, the loop will be at the top edge of the channel. This just keeps cord management a little tidier.

5. Sew in place with double box stitches for strength.

Step 8: Connect the Shells Together

Start by sewing one shock cord channel along one long side of the quilt. Which side you choose doesn't really matter now.

1. Place the outer shell (blue in my case) on top of the inner shell (orange) about 1" inside the edge. (Baffles on the inner shell and baffle tape on the outer shell should be facing each other on the inside).

2. Fold the orange edge over the blue to create a 1" channel along the edge. Pin or clip in place as needed.

3. Sew the inner and outer shell together along the length of the quilt.

Step 9: Sew the Outer Shell to the Baffles

1. To make the material easier to manage, roll up the outer shell and clip it in place. Leave one baffle tape line exposed at a time.

2. Pick up the next baffle on the inner shell and move it over to the exposed baffle line.

3. Fold the edge of the baffle material about .25" so you will sew through two layers for strength.

4. Check your total baffle height with a ruler as you go. Mine was 2.25".

6. Sew the baffle down the length of the quilt. Try not to sew on the tape line. This will make it easier to remove.

7. Remove the baffle tape line.

8. Unclip and unroll the outer shell to expose the next baffle line.

9. Repeat for all baffles.

Don't sew the other long edge of the quilt together yet.

Step 10: Sew on Your Label (optional)

For a little added touch, I decided to order some printed fabric labels from the Internet with a logo on them. You obviously don't have to do this, but if you do, now is a good time to sew it in place.

1. On the unattached, long edge of the outer shell, find a spot for your label. I chose about 1 foot in from the head end.

2. Tape the label in place.

3. Sew all four edges.

You might want to practice with scrap shell material and extra labels. The tension and stitch length may need to be changed. Remember to change it back when you're done.

Step 11: Sew the Final Side and Bottom Closed

1. Sew the other long side closed making the same 1" channel as before.

2. For the bottom, you will need to pleat the outer shell (blue in my case) as you go. This is because the outer shell chambers are wider than the inner shell (the "differential cut" from earlier).

3. Match up and pin each baffle seam so they don't move.

4. Fold the excess outer shell material into a pleat on each chamber.

5. Fold the inner shell over to form the 1" channel like all the other sides. Pin at the pleats if needed.

6. Sew the channel in place, with pleats, along the bottom of the quilt.

Step 12: Stuff the Down

Now, for the fun part! I used "The Shopvac Method". This certainly works and is *fairly* clean, but is definitely time consuming. You can search for other methods on as well.

1. Hang the quilt with the open end up (you can use your grossgrain loops!)

2. Take the extension tube off a shopvac hose.

3. Cover the end of the tube where the hose connects with noseeum mesh and rubber band it in place.

4. Connect the tube back onto the end of the hose. Now you can vacuum down into this and it will be trapped in the tube.

5. Start vacuuming down into the tube.

6. As soon as any down is in the tube, it will lose quite a bit of suction. For efficiency, don't stop at that point. Use your hand to help stuff down into the tube. It will continue to be sucked down the tube slowly.

7. After a few handfuls, remove the tube from the shopvac (make sure the mesh stays on).

8. Place the tube on your scale and zero it.

9. Put the open end of the tube into a chamber of your quilt.

10. Blow through the mesh end to deposit the down into the chamber.

11. Put the emptied tube back on the scale. The negative weight shown is the amount of down you just added to the quilt. Record this number every time.

12. Repeat until you reach the desired amount of down in the chamber (from your spreadsheet).

13. Shake the down into the bottom of each chamber as you go. This will help keep the down from floating back out of the quilt and also lets you visually check that each chamber has roughly the same amount of down.

14. Clip the top of each chamber closed when filled.

13. Repeat for all chambers.

Step 13: Sew the Top Closed

1. Make sure all the down is shaken to the bottom of the quilt and each chamber is clipped closed.

2. Take the quilt back to your sewing machine and sew the head end, 1" channel in place closing the top.

3. Remember to pleat the outer shell just like the bottom as you go.

4. Fluff up the quilt to distribute the down throughout each channel evenly.

5. Measure that fluffy goodness to estimate your temperature rating. Mine has about 3" of loft throughout.

Step 14: Add the Suspension

1. You need something long, narrow and stiff to fish the shockcord through the channels. I used a straightened coat hanger with a bend in the end.

2. Carefully push the rod through one channel, scrunching the material as you go until it protrudes from the other end.

3. Tie your 1/8th inch shockcord to the end of the rod.

4. Carefully pull the rod back through the quilt to thread the shockcord through.

5. Repeat for all the other channels.

6. For the shorter, end channels, insert a cord lock on each end so it can be cinched around the hammock ends.

7. Tie the ends of the long channels' shockcord together at each end. This will attach to your hammock suspension to hold it under the hammock.

8. If desired, tie a short loop of shockcord from each corner tie out to the main suspension line using a prussik knot. Adjust along the length of the suspension to hold the quilt in place.

Hang your hammock and new underquilt and admire all your hard work!!

Instructions for a matching top quilt coming soon.

2 People Made This Project!


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Question 1 year ago on Step 2

I'm looking at the Catsplat calculator.

I have an existing quilt with about 12.6oz of 900fp down. I believe the baffles are roughly 2 and loft is 2.5" it is rated to 20 F. With these settings i have to set overstuff to 23% to get to the 12.6oz i have. Your temp rating is a bit liberal.

I want to add down of 800fp quality. was thinking 4 oz so if i change the FP to say 875 FP average i have to plug the overstuff to 63% to get to the 16.6 oz of down i will have. so add an additional 40% of overstuff.

THis gives a rating of -6 F

If i lower the FP to 800 FP i have to plug the overstuff to only 48% to get to 16.6 oz and that has a rating of 1F. so add only additional 25%

Is there not something wrong with this calculation? Should i not need less additional overstuff of 875FP to get to 16.6oz?

As well, is there an allowance for if you get to a point where you have too much down for the size of loft/baffles?

I'm basically trying to figure out how much down i can add without comprimising the size of loft/baffles and what kind of improvement in temps that would give me.


Answer 1 year ago

First, let me say this post is ancient and I'm glad it's still finding use out there for folks.

I'm not sure what you mean about my temp rating, but I can tell you the actual rating of the quilts I built (I paired this under with a similarly built top) is closer to 10-15F. I still use the same quilts today and they are toasty warm at 17F. I haven't tested lower, but they definitely have some room.

The calculator is not mine; it came from "catsplat" and was the popular choice for calculating this stuff back then. I can't speak to any errors within or if there are newer/better versions available now.

That said, to your question on fill power, the higher the fill power, the lower volume per weight (because it lofts more with less down). So with 875 fill power, you will have to provide more volume to get to the 16.6oz which will create more stuff (but significantly lower temp rating because of all that high-fill-power down). I would say you should instead target temperature rating and weight and back into the fill power you need.

I don't think adding down is as easy as you're making it sound though (I'm imagining removing all the existing down, mixing it with new, lower FP down and then replacing it. Maybe that's your plan. Even if you get a good mix, I don't know if blending different FPs would result in those averaged fill power numbers in any reliable way. I agree there's logic to that, but I don't know the accurate calculation.

If you just want to decrease the temp rating of the existing quilt, why not stick to the 900FP already in the quilt and add just enough to reach the temps you want? This is the easiest math, easiest process (open each baffle and just "top off") and results in the lightest quilt. It would also avoid your concern of too much stuffed into each baffle "capping" the ability for the down to loft.


Reply 1 year ago

Thanks for the reply


Question 4 years ago on Introduction

I do a lot of backpacking, how small is this quilt able to pack down too?


Question 4 years ago on Step 12

how much down did you use per chamber/ whole quilt?


5 years ago

Very nice. I wanted to buy one but making one looks like much more fun. Favorited for future reference


5 years ago

Have you made any instructions for a matching top quilt? I'm really interested in making these two components together like you did. This is definitely the best set of instructions I've seen!


6 years ago

Why did you use 9 baffle chambers? In the original sheet it has 12 baffle chambers and I was just wondering the change. Does it have any change in the temperature of the underquilt, or shifting of the down? Understand that it makes the quilt weigh less and less trouble with not having to sew as many baffles in place.


Reply 6 years ago

Hi zantendogg28,

I chose 9 baffles to get in the range of a 5-6" baffle width, but this is mostly personal preference. My primary consideration for number of baffles was aesthetic and, to a lesser degree, weight related as you mentioned. This has no effect on the warmth of the quilt since you're still calculating how much down to stuff in each channel to achieve the desired baffle loft (and hence temp rating). The sewing really isn't that big a deal, but stuffing extra chambers will add time to the build depending on your method. That said, 12 chambers with my quilt dimensions would give you exactly 1.0 oz of down per chamber. If you did that and paid more for down that is packaged in 1 oz. baggies (vs. bulk like mine), stuffing could be simpler. With your dimensions, you could adjust baffles to do something similar.

Down shifting is not an issue, practically speaking. Regardless of the number of chambers, you could shake the quilt and pack the down toward one end or create gaps, etc. Every time you use it, you want to fluff the down and spread it evenly to get good, functional loft throughout. For me, that's a couple of quick shakes when I pull it from the compression sack.

pie popper
pie popper

6 years ago

This looks fantastic! Recently bought a hammock and tarp that fits over it... this is what I need next! Do you know how much it cost you in total? Love your work, looks very professional.


Reply 6 years ago

The UQ was a little over 150 completed, but that also was a tad lower because I bought the down for both the UQ and TQ together.


6 years ago

I have got a para sail or surfer sail kite parachute . Thar would work great for something like that . I live in west central fl and was going to list it on Offer up and let go , As well as the Tampa area craigslist .I thought I could use it as a canopy also . When I got it the bladder had a leak apparently they put gas in the bladder to make it lighter .


6 years ago





6 years ago

Any suffocation risk??


Reply 6 years ago

Just establish a safe word beforehand. Mines Oklahoma. I yell that at the underquilt when its getting too rough.


Reply 6 years ago

It depends. If you hang your hammock underwater there could be a problem, otherwise I suspect the answer is no.


6 years ago

Awesome idea. Camping in the winter can be miserable. A few years ago I got the bright idea of getting a double person hammock to share body heat with someone else. My best buds Ben and Frank were acting kinda weird when i proposed them doing this with I posted an ad in the totally platonic section of craigslist for a camping companion. I tell you what, I have yet to meet someone from there who respects the "totally platonic" idea...and in the dark of winter I've done some things I'm not exactly proud of. The past is the past though...I'm going to try this underquilt idea going forward. Thanks davemayo2000.


Reply 6 years ago

What happens in the hammock stays in the hammock.


Reply 6 years ago

Woah Dave!!!! TMI!!


Reply 6 years ago

Jack, I thought we agreed to keep what happened in that hammock to ourselves?