Shuttle Punt

The shuttle punt is many things. 

First, it is a clamshell bike trailer.  You tow it with your bike. 

Second, it unfolds and becomes a boat which will carry you and your bike. 

Third, it can be loaded up with camping gear, food and water for multi-day adventures that incorporate both bike trail time and river or lake time, all on the same trip.

You, your bike and your boat travel together. 

A solar panel and battery can be added to charge an electric bike or cell phone.

Specs:

Length: 12-13’ [365-396 cm]

Width: 27” [68cm]

Height unfolded: 8.375” [21.2cm]

Height folded: 16.75”

Capacity:

            12’ long: 350 pounds [160Kg]

            13’ long: 395 pounds [180Kg]

Draft: 2-3” [50-76mm]

Testing: 

I first tested the boat on a lake.  I was surprised by both its stability and speed. You can stand up in the punt quite easily, after all, it is more like a stand-up paddle board with side walls than a canoe or a kayak. OK, I grew up with a canoe.  We canoed on the Chattahoochee River almost every weekend in the summers. I can tell you that the punt shape is much better at tracking than a canoe and it is equally as stable as a 40” wide canoe because stability is determined by average width. Since the punt is full width front to back this gives it maximum stability for its width.  And the shape is much more efficient than I imagined. I easily got it up to 4.6 mph on a lake with no current using a 118cm kayak paddle (I recommend a longer paddle).

Size Options:

If you ever intend to outfit your shuttle punt with 2 seats, I recommend making the boat 13’ or 14’ long. The 12’ long version will barely hold 2 adults. Not everyone’s bike will be the same.  Some might have a folding bike, or an electric assist bike.  The heavier your bike is, the better it is to lay your bike flat in either the back or front half.  I chose the back because the boat tracks better with slightly more weight in the back half. If your bike is light you can mount it in a vertical orientation using a front fork bracket. If you lay your bike flat, you can secure it to the walls of the punt with eye bolts and a bungee cord stretching across.

Camping:

Because of the 2” thick EPS insulation, your shuttle punt could keep you very warm.  I recommend using the 2 side braces to keep the punt open to a comfortable height, maybe 36-38” of headroom while sitting up.  If you live in an area with lots of rain or mosquitos, you could use a rain fly or mosquito cover.  I imagine taking the rain fly off a 1-person dome tent might be perfect or, you could just sleep in a small tent next to the punt.

Stability & Tracking:

I spent several days contemplating how wide to make the punt. The widest recumbent bike tricycle that I found had an overall width of 36”. The wheels add about 6”, so that means the maximum the hull could be is 30”. However, I also wanted the boat to be fast, so I made the hull 27” wide. The illustration below shows that the stability of any boat hull is greatly effected by its average width. Since the punt is a rectangle, the average width is half its width, so the average width is 13.5”. I drew a canoe shaped body and kept adjusting its width till its center of mass was equal to the punt. It turns out that a 27” wide punt has the same stability as a 34” wide canoe, perhaps a bit more, because the punt has sharp chines.

It turns out that the punt shape has better tracking than a canoe. This is because the canoe generates more lift on the side of the boat that is slightly shaded from the on flowing fluid. This makes a canoe want to turn sideways. Most canoeists fix this issue by sitting in the back of the boat, which makes the stern sink creating a Keel behind the center of mass. With a punt shape the boat does not turn sideways as quickly because it is less efficient at generating sideways lift. So even though the canoe shape is slightly more slippery through the water, the punt requires less effort to keep it going straight. So what you loose in hull drag you make up for by paddling in a straighter line.

Speed Comparison

I paddled past a guy in a Pelican Catch 130. I helped him deploy is steering fin, which he had forgotten to deploy. He did not feel comfortable standing up on his boat even though the promotional material stated that you could stand up. Then we paddled along side each other for a bit and I noticed my boat was faster than his. Later I looked up the top speed of the Pelican Catch 130 and found out it was lower than my top speed 4.6 mph (catch 130 with hydrive) compared to 5.1mph (shuttle punt with canoe paddle). This is interesting because the boats are the same length, same width, and same weight. But I can stand up and walk around with confidence and get more speed out of my boat. The cruising speeds are the same. So you can build a shuttle punt for less than $500 and have better performance than a $1,700 fishing kayak with a peddle drive system. And the Pelican does not fold in half and is difficult to get onto the roof of a car. And the shuttle punt weighs 11 pounds less (5Kg)!