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Update on the Boston valve to pump adapter.
I’ve modified the original adapter design by @krafter to fit the 2025 Flextail Max Pump 3.
This pump offers 5KPa pressure. Flextail has a larger, 12KPa boat pump, but it’s only available second-hand as of October 2025.
Updated design. The mount for this pump consists of a tiny lip, necessitating a redesign for best airflow and for a snug fit. If you use my design, you will need to sand the lip a tiny bit for a perfect fit.
The file can be copied and printed here.
This adapter is a huge quality of life improvement. Without the adapter, these electric pumps couldn’t push through the Boston Valve rubber, requiring the boats to be filled via the deflation opening as shown below:
With the adapter, the nail heads slot through the plastic and push away the valve. I can finally fill the boats straight from the Valve opening.
I can inflate the packrafts up to something like 95% inflated. I like the packrafts firm I still manually temper them further, but they are very usable even without the additional effort.
For nails, I recommend using a small finishing nail and drill out the holes with a 1/16” bit to rough out the interior surface for JB weld epoxy. Use large cutters to cut the nails down.
Matt, I highly recommend adding pumps and Boston adapters to all of your kit menus. These things make a world of difference. I think a lot more people would adopt these boats if they had an easy inflation option.
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There’s a couple of these drybag designs floating about. This looks ideal for playboating, or adventure river crossings.
With the ubiquity of electric pumps these days, I’m not sure if the tradeoff of a rolltop that might be a bit more vulnerable deflation makes much sense.
Personally, I prefer just having one-do everything heavy-duty boat I can pump up to crazy pressures.
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Simple new project for today. Used 250GSM fabric to make a phone pouch for an Anfibio inflatable lifejacket. The pouches of these jackets are mesh panels that wouldn’t hold anything if you lean over, much less take a dunk in the water.
Sits inside the chest area, velcro closure with webbing pull handles.
Above is a new roll of that UHMWPE thread I like.
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Here is one of my modified spray skirts, as requested.
(Above) Side profile.
(Above) Front profile.
(Above) Rear profile.
I had an issue where my more forward seating position made the spray skirt too tight around the waist. To address this, the torso funnel was cut off and four additional 150GSM fabric panels were cut from the fill bags. Two of the panels are cut in a way to offer a lot of added material behind the seat.
The panels are welded wherever possible and sewn everywhere else. This has to be done in a way that bunches the fabric, otherwise it will not retain the cone shape. Seam grip is applied, as always.
It’s a bit Frankenstein, but this design allowed the reuse of existing fabric and has the give needed to handle heavy waves without detaching from the combing ring.
Funny enough, it seems MRS might have had a spray skirt design that did something similar at one point.
To see how it looks in action, refer to one of my previous posts where I’m sitting in a boat.
I’ve also added shoulder straps. Use a single tri-glide per strap if you want a skirt to be adjustable. I have one with adjustment and one without as I don’t need adjustable straps for my personal boat.
In the most ideal situation, rather than adding a ton of material in the rear of the skirt, the combing ring opening would be repositioned forward to account for the more aggressive seating position.
Lastly, I’ve added ten strips of velcro all around the skirt and pull tabs at both the front and rear. The velcro speeds up the process of attaching the skirt from 0:30 – 1:30 to under 20 seconds. The rear pull tab also allows me to get it over the rear area more easily and center it.
Perhaps a more ideal setup would use less velcro and instead offer double-strength elastic cables.
Mat’s kits are generally excellent. However, the current spray skirt is probably the one bit of kit that I feel needs a bit of work to be ready for more serious waters. Even assuming a user doesn’t adjust the seating position, and assuming they are using the new recommended combing ring, I still think the vanilla design is vulnerable to a wave pulling the skirt off the combing ring.
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New year, new improvements for the rafts.
Above, we see a portage carrying handle (bottom center), a 9-point adjustable seat back, and 4-point adjustable leg straps. These adjustable straps fit boaters 5’3″ (160cm) to 6′-4″ (193cm).
(Above) The adjustable leg strap attachment point. For the straps themselves, I used the same design for the 4-point strap as my previous boat. This attachment point allows for the two top attachment points around either side of your knee to move toward the bow or stern of the boat. The plastic strips weaved through the material are temporary and cut from a grocery store spinach container. These strips prevent the welding iron from welding those areas to the boat. These “slots” are used to feed the removable hook clip.
Two additional standard round attachment points with D rings are used. One in the bow area and one next to the seat. The 5/8″ strap uses a tri-glides at both ends to allow adjustment.
(Above) The leg straps are attached using aluminum G-Buckle Webbing Hooks (one right and one left variant) from Extremtextil. A lot of tedious welding is required, and you’ll still need to run something through each slot a couple times to ensure they are usable. In the image above, you can also see the tri-glides used to adjust the strap that runs through the bow area attachment point and another that runs to the seat area attachment point.
For the grip handle, use an I bar-shaped leftover piece of 450GSM fabric. Two pieces of 2.5″ polypropylene webbing were sewn together on both sides to serve as the handle. The bars are placed under the attachment point and welded from the underside of the pack raft tubing.
I also seam-seal every fabric edge to avoid fraying. This sealing process includes carefully sealing the edges of attachment point slots. The plastic can be removed when this is done.
You might be wondering why the backrest is using a nine – yes nine – point attachment system. Well, I’ve found that comfort for long-term tripping is immensely improved by having the firmest backrest possible. This is a huge quality-of-life upgrade to a packraft, akin to adding a skeg, probably more so. The blue raft uses a custom bag and a five-point attachment system that I’ve detailed in the past. While I like this system, it was a pain to seal and I wanted to see if a strap alternative for the yellow boat could be found. A nine-point system was the result of these efforts. When fully inflated, the seat won’t move in any direction, even with 100 pounds (45KGs) of force applied via persons or weight plates. The backrest can be removed.
If I had any recommendations for Matt’s future designs, it would be to shift the sitting position a bit forward and provide instructions to set up a firm, upright backrest. Ideally, this includes adjusting the spray deck opening forward a bit. I can’t emphasize enough how this change improves comfort, tracking, and paddling efficiency; it’s like having a different boat.
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Above are two sets of 5-piece paddles. I’ve further refined the water cups from the previous year by shortening the cup fabric and painting it inside and out with Seam Grip. Doing this adds a ton of abrasion resistance and rigidity. Both paddles use custom carbon fibre tubing. The tubing is available via Aliexpress. The seller Best Carbon Fiber Products is great. Email him directly and he can get a custom order set up on the site with the exact amount and lengths you need.
To match traditional paddle sizing in a 5-piece paddle, you’ll want the following order:
29x25x400mm, 3 pcs (these are the three sections of the paddle shaft)
25x21x130mm, 4 pcs (these are the four internal fittings slotted inside the paddle shaft).
Note that you may need to drill/dremel your paddle blades and or purchase an additional two internal fitting sections depending on the construction of your paddle. The first Werner paddle is all fibreglass and doesn’t need any additional sections. I just slotted a 25x21x130mm tube and applied JB weld. The cheap Canada Tire thermoplastic paddle needed extensive drilling and 1/2″ (12.7mm) additional fittings. I suggest you cut your paddles apart before ordering to see what you need.
To complete the paddles, you’ll need to sand the inner fitting tubes until they fit halfway inside the shaft tubes. Next, soften all exterior facing tube ends with a rotary tool like a Dremel. Glue one side of the inner tubing with JB weld.
Next, you’ll need to drill holes and install 9mm single-pin spring clips. These can be bought from Aliexpress or Amazon. Make sure you get the ones that are both hollow and stainless. Important: don’t trust sellers. Put the clips into a glass of water overnight and dry them for a second day in a plastic bag to ensure they are stainless. It took two orders to get actual stainless steel.
Second, you’ll need to clip off about 3cms of the spring clip tail. If you don’t do this they’ll never work correctly. When drilling the holes for the clips, make sure the tubes are already inserted for perfect alignment. Start from a small drill bit, and work up from there. If you make a mistake, you’ll end up with a wobbly paddle and it will feel terrible. You’ll need to use a Dremel and smooth out the hole inside and outside a fair bit. Resist the urge to simply drill a bigger hole. The holes must be exactly 9mm or there will be wobble. If the button depresses and doesn’t pop back up, use the Dremel along with constant pushes of your thumb until the spring clip operates smoothly. This process will take some time but it will work well 100% reliably with some effort.
When you are done, you’ll have a backpacking/airline-ready paddle setup!
Not sure if I covered this one before, but I’ve also upgraded the spray skirt. The original skirt isn’t configured for this more upright/forward-sitting setup, and it just doesn’t have enough fabric give at the base for the kind of pressures and movements you’ll experience in whitewater. I cut the skirt apart and added four additional 150gsm panels and ironed/sewed and seam sealed them around the waist area. This is a huge improvement and allows for a full range of twisting without worry that the fabric will become too taunt and pull off. Honestly, I see no downside to this addition and feel the skirt should offer more fabric by default around the base.
A couple of final points. First, Matt’s combing ring tube upgrade recommendation is a must for a proper whitewater setup. This solved a lot of water ingress and combing ring strength issues. I had originally replaced the blue tubing with another black Nylon one, but it also proved to be too weak. This new 1/2 Pex tube is great.
Lastly, I can’t recommend the gear from Anfibio enough. In the picture above, I’m using their inflatable lifejacket and their customizable packraft drysuit. Amazing gear for backpacking. The only issue is shipping. If you live in Canada or the US, you’ll need to work through a parcel forwarding service. This is a major pain, but zero shipping options for North America seems to be common for German companies. I recommend the service ShipGerman and selecting the post-service option to keep your costs down.
(Above) one final upgrade: I’ve replaced the rather wonky value on the Thermarest XTherm with one of Matt’s values. This allows for a FlexTailGear pump I use for the rafts to inflate the pad in a few seconds. The black fabric is leftovers used to seal the original value opening.
This is a long post! The next projects for 2024 are an inflatable flatwater sail and an inflatable helmet. The goal is to make an international backcountry whitewater kit that requires only a single backpack for everything. A couple of European startups are working on inflatable helmets, so I’ll try whichever model comes to market first.
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New project to show off.
A lot of hardshell boats offer sturdy foot rests to brace your feet against. This is something I miss from packrafts.
Matt was kind enough to send some extra 250GSM fabric in my latest order. After some trial and error, I came up with a relatively simple footrest design.
This drybag is designed to be wedged into the bow foot space of your boat.
The original plan was to make this an inflated dry bag to rest your feet on.
(Above) The larger, initial design. Someone asked me if I was making a pursue!
After making this, I quickly discovered that an inflation bag is a terrible idea. It was the equivalent of pressing your feet against a balloon. It provided zero support for your feet. It was also too big, as Matt suggested in an email.
I cut it down significantly:
The drybag aspect remains as putting items inside it what gives it structure. This design is large enough to comfortably fit a Dan Durston X-Mid 1 tent and a Thermarest XTherm Max Wide (25″ wide) sleeping air mattress.
The webbing straps are 3/4″ polypropylene. Avoid Nylon for all boat stuff as it absorbs water. These straps are sewed in by hand on each side of the opening using UHMWPE thread. Some may know this material as Spectra or Dyneema. It is far tougher than nylon thread. You can pick this up as 65Ib UHMWPE fishing line on Amazon.
The valve allows for the air to be pushed out of the bag. With the air removed, the bag offers a really firm surface for your feet.
The foot rest friction fits very snugly into the leg area of the Telkwa.
The roll top allows for size adjustment. Roll it more and fill it less for more legroom.
Lastly, don’t forget to brush Seam Grip over any fabric edges or fraying will occur.
Something interesting I’ve learned from this project is that an airtight drybag is entirely possible. For example, a 22″ opening reinforced with 3/4″ webbing can be made airtight with twelve fabric folds. No additional hardware is required. However, I tested it with seven folds and it will loosen at high pressures and deflate.
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Hey Krafter, have you seen the screw-on adapter shown here? Merging your design with the Boston Valve screw-on on threads would allow hands-free operation.
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Krafter, have you made any of these adapters and tested them? I want this!
To answer Matt’s question: For my version which is the max pump, no. The pump is not powerful enough to push air through the check valve.
An attachment like this would be a huge godsend. Krafter, If you’ve printed out any of these, I’d happily pay for one as I don’t have a 3-d printer. If you’re interested, can you send me your contact details?
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I think the solution might have been staring us in the face.
Why not maintain your original design, but add an adapter designed to slot over your existing one? We could then cut out an adapter attachment similar to what the Boston valve uses.
If designed with a lip, you’d just need to epoxy one ring to each adapter.
This would have the added benefit of shielding the pins.
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Yes, I’ve tried the smaller design just inflated. It was Alpacka’s offering that made me confident an inflated footrest would work. I filled the bag as full as possible without using a mechanical pump. The issue is that your feet don’t apply even pressure on the footrest when paddling. It only felt solid once you added an object and pushed out all the air.
Maybe it’s possible to get it firmer. There may also be a solution by dividing the internal area into two separate compartments. You could probably use an internal wall to limit compression to a single direction. For me, retaining foot space storage is a must, so these experiments were never tried.
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Yes, the valve used for the seat.
It would be interesting if your design could be modified in a way that would be workable for both the Boston Valve and these seat valves.
Carrying multiple adapters isn’t practical when using these boats for something like portage backpacking. Too easy to lose small accessories.
I bet a similar design without the air windows and maybe a slight modification to the nozzle tip would do the trick. What do you think?
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The pictures were helpful. Yes, I’ll look into that.
Question. Have you tried to see if this adapter works with the smaller inflation valves Matt sells? Currently, I have one of the white adapters that came with the Flextail pump epoxy’d on permanently. It fits loosely over the valve’s head but is sufficient to get these smaller objects filled quickly while still fitting snuggly into the Boston Valve so long as the top is completely removed.
It would be nice if this adapter could be configured as a one-size-fits-all setup.
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Hello Matt.
Okay. I’ll post something on the skirts when I have time.
Nice! A four-point leg strap system would be a great option for builders.
On the issue of flex, I don’t notice anything unless I’m facing directly into the wind with light choppy waves. The bow tends to bounce on these. I don’t recall this feeling any different from my early tests with the backrest sitting against the stern. However, I’m extremely light.
After using the FlextailGear pump I tend to blow until I physically can’t force air into it any further. I find these boats are best inflated as firmly as possible.
FlextailGear recently released a high-pressure battery pump specifically intended for inflatable boats. It even has an adapter for Boston Valves. I might get this pump sometime this year and see how it compares. With their original pump, I have to unscrew the one-way valve and awkwardly screw the cap on quickly as the pump lacks the pressure needed to fill through the one-way valve.
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