Making an Inflatable Floor

Note: This step can be done at any point during your packraft’s construction. It will be easiest if done before the tubes are completed, but can also be added to a completed packraft with a single-layer floor. If you are doing this step before your tubes are completed, remember to leave at least 5 cm unsealed around the perimeter of both floor pieces so you can attach the tube pieces!

If you have purchased the double-layer floor option with your DIY Packraft kit, you may want to make your floor inflatable to insulate your legs from cold water and to provide some extra padding.

There are two different methods for making the floor inflatable:

  1. Sealing the floor pieces directly together in strips
  2. Adding baffles between the floor pieces

Option 1: Sealing the top and bottom floor pieces together in strips

The quickest and easiest method is to follow the normal construction procedure, but instead of using a full-size clothes iron to laminate your floor pieces together, use your heat-sealing iron to seal the two floor pieces together in strips (following the pattern in the diagram above). Install a Small Valve on the upper floor piece so you will be able to inflate it. Between the heat-sealed strips (where the floor pieces are not heat-sealed together) will inflate when you add air through the valve. (Remember to leave gaps between the sealed strips to allow air to move between them!)

 

Option 2: Adding baffles between the top and bottom floor layers

Note: Fabric for making baffles is not included in the kits but can be purchased separately. Scraps will work fine, as the baffles do not have to be made from continuous pieces.

A more elegant (but also more time-consuming) method of making an inflatable floor is to install baffles in a similar pattern to that pictured below. (Baffles are strips of fabric that span the vertical gap between the bottom and top floor layers. High quality sleeping bags and camping air mattresses feature baffles because they provide a more consistent thickness and better insulation.)

The heat-sealing procedure for installing baffles is illustrated in the inflatable seat video and instructions, and it basically makes your floor into an inflatable mattress.

Example floor baffle layout – modify as desired.

I got pretty fancy with my baffles and had them tapered so the floor was 7 cm thick under my butt to 4 cm thick near my feet, and 3 cm thick near the front and rear of the floor. I also made the center baffles taller than the outer baffles, so the side-to-side cross-section of the floor looks like a squashed diamond. (This level of complexity is not required.)

I recommend making your baffles no more than 5 cm tall (excluding the parts that are sealed to the floor pieces) because as you inflate the floor it draws the sides of the packraft together somewhat, and the thicker your floor is, the more pronounced this effect will be. (Adding more baffles and making the outboard baffles shorter than the central baffles will also help to minimize this ballooning effect.) For this same reason, do not inflate your floor fully – it will pull the sides in less if it is only partially inflated. (If you stand on the floor, your feet should rest on hard ground, but when you sit on it, you should be elevated on a cushion of air.)

High strength and puncture-resistance is not required in the baffles, so they can be made from either 210D or 40D fabric.

Tip: When you bond the baffles to the first floor piece, orient them all with the TPU facing in the same direction – this will make it much easier to bond them to the second floor layer (see Make an Inflatable Packraft Seat for for details).

Tip: You can cut holes in your baffles to lighten them and improve air flow.

Making the floor airtight

Whichever way you choose to make your inflatable floor (with baffles or by sealing the floor pieces together in strips), you will need to heat-seal a perimeter 2-3 cm wide around the inflatable part of the floor so it will hold air (if you are making the inflatable floor before your tubes are finished, remember to leave at least 5 cm around the outer edges of the floor pieces unsealed so you can attach the tubes).

When sealing around the edges of your inflatable floor, be sure to keep the top and bottom floor pieces aligned, and avoid creating wrinkles or folds in the fabric, as air could escape through the fold if you seal it in place.

Tip: If you find that your floor is ballooning too much after you’ve sealed it up, you can still heat seal the top piece to the bottom piece in some extra spots or strips.

Questions? Please leave a comment below.

10 thoughts on “Making an Inflatable Floor

  1. Thanks Matt, I’m finally done with my tie downs and moving on to the next step which would be tubes, but it seems like I should do the inflatable floor first now? That seems like a lot of baffles compared to your seat and to other packraft inflatable floors with 4-6? What difference did it make from the first version or is that theory to make it more rigid fore-aft? Also you made the baffles shorter toward the edges, but do they taper at all bow to stern? Fattest point under my butt? And why not run them the full length (with holes in the baffles)? And do I seal around the perimeter of the floor leaving a 5cm flap? Or just attache the second floor layer to the baffles and then seal the perimeter after the tubes?

    I’d love to see a video or more pics when you get a chance. I’m still trying to get it in my head how to align everything properly before I have the tubes made up but I’ll start thinking about it in earnest tonight.

    1. Hi Stewart,

      I just sketched the baffle locations in that diagram, and erred on the side of more, rather than fewer. The only real benefit of having more baffles, as far as I can tell, is that you get less of that ballooning effect I wrote about, so the sides are pulled in less – but you can get the same effect by just not putting as much air in your floor. I ended up sealing the top to the bottom in a few places after the fact, because I hadn’t put in enough baffles near my feet (that’s where the air wants to go when you sit down because there’s less weight there).

      My hunch is that most people will naturally blow up their floors until they are firm, but that will pull the side tubes together so they wrinkle… I’m working on a redesigned floor that will account for this and eliminate the wrinkles when fully inflated, but it’s not ready yet.

      You can definitely run the baffles the full length – just note that the floor bends up at the front and back of the side tubes, so the baffles will kink a bit. That shouldn’t make much (if any) noticeable difference. In the diagram I added those short little baffles along the hinge lines, but I’m not sure if they actually make a difference. When I made mine, I added sideways baffles there, but I don’t recommend doing that because it’s difficult to seal the top floor piece on if you have baffles facing in different directions.

      I think I mentioned I made my baffles 7 cm under my butt tapering to 4 cm under my feet, and about 2-3 cm near the ends.

      I think you will find it easier to seal the perimeter before the tubes are completed and tape the 5 cm flaps back until you’re finished sealing the tubes to the floor. Once the tubes are in place, they tend to get in the way when you’re sealing the perimeter (it’s hard to position the top floor piece correctly and avoid touching the tubes with the iron), so if you can get the floor airtight first, you won’t have to work so hard at it.

      Thanks!

      Matt

  2. Still building my first raft so no experience yet with the issues of the inflatable floor. I can however, imagine what that most of the weight is on the back of the floor causing the air to push up the front. What do you think about dividing the floor in two? One section-about 30-40cm at the back and the front part of the boat comprising the second. This should stop any issues with lengthwise air movement but might make the floor less streamlined due to the transverse weld line.
    Also, has anyone made a seat back or is it even necessary? Can one lean up against the rear tube?

    1. I do think a seat back is a good idea, but I haven’t got around to making a post about it yet. One can certainly lean up against the rear tube, but adding a seat back will improve comfort and allow you to sit more forward in the boat, if desired.

      With adequate baffles or through-welds near the front of the floor a separate air chamber shouldn’t be required, but it wouldn’t hurt, and you would have the ability to adjust the air pressure independently (plus a third air chamber, if safety is a concern).

      Cheers!

  3. Regarding seat backs, SOTs (sit-on-top plastics) have metal (copper) anchor points/loops built into their frame to connect the seat to via carabiners. If is possible to build in such hooking points to a packraft during construction. I’m completely new to packrafts; haven’t seen one except in a picture; so apologies if this is a daft question.

    1. I’m looking at a Johnston Backband. Check out https://lucmehl.files.wordpress.com/2011/12/packraft-backrest.jpg
      Looking at the pimp my packraft site, I see them laying out the attachment patches and determining ring and loop layout by force vectors. They’re using all kinds of nasty glues and stuff but I’m thinking that it would be easy using Mats heat sealing techniques with d-rings in place of the loops.

    2. Yep, it’s definitely possible using the tie-down attachment methods shown on the How-To page and in the Forum. I would just be careful about placement, because a seat back can have a lot of force on it, and it may deform the shape of the packraft if it’s pulling too much in the wrong way. My hunch is that the best results will be from attaching the seat back to the floor or to the seat bottom.

  4. Is the top piece of the inflatable floor sealed to the bottom piece of the floor or to the tubes?

    1. I made mine by sealing it to the bottom layer of the floor of an already completed packraft that previously had a single-layer floor. If you’re adding an inflatable floor during construction, you can seal the top piece to the bottom layer of the floor to make an airtight chamber and then fold the excess fabric up around the edges and seal that to the tubes, as shown in the instruction step detailing how to install a double-layer floor.

      My new favoured method is to make a separate and removable inflatable insert that fits in the packraft (basically a full length seat), because it’s less complicated and doesn’t pull the side tubes towards each other when it’s inflated, as an integrated inflatable floor does.

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