Heat Sealing Iron Modifications

The following iron modifications were originally posted in the forum by Bruce, who teaches boat building classes at the Folk School in Fairbanks, Alaska. I’ve reposted Bruce’s images here with edited text. All credit for this great idea goes to Bruce! – Matt

Model aircraft irons (designed for applying plastic covering film to radio-controlled airplanes) work very well for welding the DIY Packraft heat sealable fabrics. These irons generate lots of heat and maintain a consistent temperature – two things lacking from most other mini irons I’ve tried. There are several brands of these irons available, such as the Coverite Black Baron pictured below, and they can be bought at your local hobby shop or online for as little as $19.99 USD.

It’s not essential to modify your iron – you can build a packraft with one of these irons straight out of the box – but the shape and size of these irons isn’t optimized for building packrafts. The bottom is too flat, too wide, the sides have too steep a taper, and the tip is too round, so you’ll find your iron easier to use if you make the changes detailed below. You might wince at the idea of making such drastic changes to a brand new tool, but I think you’ll be glad you did. If you somehow mess it up beyond repair, you can always purchase a replacement shoe for about $7.99 USD.

To make these changes, use a metal file and then sand the surfaces smooth with 220 grit sandpaper. Polish with extra fine steel wool and wipe with a rag, then test the iron on a scrap of fabric to make sure all the aluminum dust is gone and it won’t leave grey marks on the fabric. If you have access to a bench grinder with an aluminum wheel, that will speed things up.


As purchased, the bottom is flat and you have to use all of it or nothing. The tip is too pointy, and the sides are so rounded as to be useless
Here is an unmodified Coverite Black Baron heat sealing iron. Note that the unmodified surfaces have a black non-stick coating applied over the solid aluminum. In the photos below, modified areas are bare aluminum and appear silver in color.


This picture shows the shape and size of the cavity within a Coverite Black Baron iron. There’s lots of aluminum to the front and sides of the cavity that can be safely removed. The iron is held together by a few screws, so it’s easy to take apart and put back together.


Rounding bottom of Top Flight
Flattening the tip of a Top Flight iron, which is held in a vice (unmodified areas of the Top Flite iron are painted light grey). Bruce recommends removing the heating elements before going at the iron with your file. Here you can see the cavity within the iron – as with the Black Baron, there’s lots of aluminum forward of the cavity that you can safely remove.


Round the front of bottom, beyond the internal hollow.
Mark on the iron’s bottom the location of the internal cavity where the electronics are housed (Top Flite iron pictured here). Don’t modify within this area or you might file all the way through the aluminum.


Flat side, and rounded bottom.
Here you can see one side of a Coverite Black Baron iron, filed flat at 90 degrees to the iron’s bottom. You can also see the front of the bottom has been rounded up slightly and the top of the front has been rounded down.


Flattened side working the edge of a zipper install.
Here the flattened side of the iron is being used to install an airtight zipper. Note again the rounded bottom and blunt tip. The blunt tip (about 10 mm wide) is great for sealing the ends of the seam tape!


Flattened tip working along a seam.
Here the flattened (slightly rounded) top of the iron’s tip is being used to seal a seam strip between two of a packraft’s tube sections. Notice how flipping the iron over like this makes it much easier to avoid touching the tube fabric with the iron.


Flat side is sealing the inside of a seam.
Here the flattened side is being used to seal the inside of a seam. Rounding the forward end of the iron allows one to use just the tip, without having the full width of the iron in contact.