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The “Seam Grip +WP” is the same product that used to be called “Seam Grip” and you’re right – I just checked and “polyurethane” doesn’t appear anywhere on the new tube or packaging.
Most of the content on this site was written before they changed their product names and messed everything up, so I’m going back to add “+WP” everywhere Seam Grip is mentioned to (hopefully) make this clear to everyon, but some shops still have stock of plain old “Seam Grip,” so we’ll see if this causes even more confusion.
I looked at some Seam Grip+SIL reviews online and it seems like you’re not the first person to make this mistake… I think an email to Gear Aid expressing your displeasure would not be uncalled for.
I used to not apply anything at all to the inside of the seams, so don’t worry too much about it. In your situation I would apply some Seam Grip+WP to the outside of the tube-to-tube-to-floor joints (those are the most likely places to leak), and you can decide if you want to apply it to the outside of all of the seams or just wait and see if it’s needed. I typically apply it to the outside of the seam strips on the underside of the packraft to protect them from abrasion, and if you let it cure clear it actually looks pretty good, so in your situation I might just go ahead and coat all of the seams on the outside so you don’t have to worry about leaks developing in the future.
Hmm, yeah, that’s a problem. The “+SIL” stuff is “silicone tent sealant”, and will only stick to silicone coated fabrics, not polyurethane. It used to be called “SilNet,” but I guess they changed the name to “Seam Grip+SIL” for some reason. I will add a note to the instructions warning people not to confuse the two. Unfortunately I think you’ll have to try to remove it if you can.
Interesting… what brand is it? I haven’t seen this with Seam Grip before (or any of the other McNett/Gear Aid polyurethane products), but I have seen it with all the other seam sealants I’ve tried, which is why I recommend the Gear Aid stuff.
I used to only seal around the places where the seam strips intersect with the floor, but in spite of my best efforts I always ended up with at least one leak that I had to track down, and finally I decided that for me (and most people) it is worthwhile to apply seam sealer to the inside of all the seam strips.
Because you have a zipper, it won’t be a big deal if you want to try without seam sealer, although it will be more difficult to apply it inside if you do decide you want to later (but you can apply it to the outside, instead).
When figuring out the temperature and timing, I find it helps to hold the iron in one place and count out five seconds, then remove the iron and roll (or press) the spot as it cools. Then check underneath for melt-through before ripping the weld apart to see if it’s bonded fully. If five seconds isn’t right, try six (or four, etc.). If no amount of time consistently lands you in the sweet spot, you probably need to adjust the temperature.
Hi Blair, it sounds fine to me. If it is 1000D then you should be able to get a good weld without permanently altering the appearance of the fabric – just move a bit faster. It takes some practice to get the timing right.
Paradoxically, if you can’t get a good weld before the heat transfers through and changes the appearance of the fabric’s underside, you might need to increase the iron’s temperature a bit.
Cheers
I see them now – it looks like your iron might be a bit too hot, but it’s hard to tell in the pictures. I don’t normally see the woven fabric get shiny like that. (What I see doesn’t look like a problem though.) The fabric shouldn’t melt at all, just the TPU. Lowering the temperature a bit will also reduce the chance of it melting through to the bottom of the floor – just be sure to test some scraps whenever you change the temperature.
Hi – your pictures didn’t seem to work (I just see an “image not found” icon), but from what you’ve written it sounds like it’s probably fine. I designed the seams to be way more than wide enough, so even if they’re not perfectly sealed they will be strong enough, within reason. Cheers!
Thanks for the tips, and excellent idea to use the double D-rings!
I’ve gotten to the point where my new packrafts will hold air indefinitely, but I’ve built way more of them than you and my first couple of attempts leaked way worse than yours, so it sounds like you’ve done a great job. You could try to track down where the air is coming from using a 50/50 mix of soap and water painted on with a brush, but it may not be worth your time for such a slow leak. When you’re actually using it, the temperature will affect the air pressure much more quickly than a leak that slow.
Regarding the glue-brain thing – I definitely recommend applying Aquaseal/Seam Grip outside if the weather cooperates, and at least in a well ventilated room. I do it in my garage with the window open and then get the heck out of there. I also try not to do a whole bunch of seam sealing all at once – maybe one or two seams and then leave it overnight.
Cheers!
Hi – it doesn’t look too bad; I would probably just spread a bit of Aquaseal over that area, or seal a scrap of tube fabric over it if you don’t mind the look of a bit of yellow there (it’ll be on the bottom of the packraft, so not visible when in use).
It could be the temperature is too high, but it looks good elsewhere, so maybe just avoid lingering so long in one place. It’s tempting to heat a large area to work those pesky bubbles towards the edge of the fabric, but it’s easy to melt through the floor if you do it too long, so if the bubbles are small just leave them there (the seam is way wider than necessary for adequate strength), or use a needle to make a small hole in the tube fabric to release the air from the bubble (but don’t push the needle through both fabric layers or you’ll end up with an air leak).
Great job, and thanks for posting!
To answer your question about the potential benefit of sewing the seams, I have done lots of destructive testing on the tube-to-tube seams used in the DIY Packrafts and the fabric around the weld always fails before the weld does – in other words the ironed seams are stronger than the fabric tubes – so while sewing the seams before welding might make the seams even stronger, it wouldn’t add any strength to the finished boat.
Regarding the leaks, I’m curious about whether or not you coated the inside of all of the seams with Seam Grip – if not, I definitely need to make this clearer in the instructions. Cheers!
The short answer to your first question is “yes,” and the short answer to the second question is “no” – you could make a packraft with only flat seams, but that would be stretching the definition of “packraft”… something like the Klymit LiteWater Dinghy is about as close as you can get.
That Anfibio packraft you linked to has a flat seam around the outside, but the cockpit seams are not flat. I made a prototype like that a few years ago and when it was done I didn’t think it was worth pursuing any further.
I don’t see any major problems here – it sounds like you have a small hole that needs to be plugged with seam sealer. Try to remove any foreign objects that might prevent the sealant from filling the gap between the fabric layers (I’m not sure what that white stuff is) and then apply more Seam Grip/Aquaseal on the spot that is leaking and the surrounding area. Try to force it into the hole (with the Seam Grip brush bristles or something similar) for good measure. If it still leaks after one coat, simply apply more.
Thanks for your interest in a DIY Packraft kit 🙂
For your intended use, an Ultralight would suffice, but for more peace of mind the Skeena would be better (I think a Telkwa would just be extra weight and bulk).
I used the shortest (120 cm) Skeena on my recent 30-day trip and it was more than tough enough for use in the lakes, class 1-2 rivers, and barnacle-lined fjords I paddled. It never leaked in spite of scraping down shallow rivers and bushwhacking for dozens of kilometres through thick forests with the packraft unprotected on top of my pack. Tracking was not a problem and I was able to paddle more than 30 km (20 miles) in a day (not downstream) averaging between 4 and 5 km/h (2.5 to 3 mph). I do not have a zipper in that packraft – personally, I don’t need one, but they do make the final construction steps easier.
On that trip I ventured up to about 800 m (1/2 mile) away from land, and aside from the seat, back rest, and my PFD, I didn’t have any additional air chambers. I did wear a drysuit for one ocean section I was worried about, but it wasn’t really necessary. So often we choose gear based on our fears, and my recommendation would be to resist that impulse.
I wrote a post covering some of these topics a while ago: https://www.diypackraft.com/faq/choosing-a-packraft-not-just-diy/
Cheers 🙂
