Some emails cause our hearts to skip a few beats.

Checking in from our cross-country road trip. We stopped by a lake in Colorado a couple of days ago to take the PT11 out for a sail and noticed something very alarming... The back seat buoyancy tanks have bowed - like the air in the tanks expanded. They have returned to the normal shape again, but the fiberglass strips on the tank joints probably couldn't handle the pressure and have cracked - see pictures attached.

Mirte-tanks-blogThis boat was built at sea level in NYC and the tanks were expanded at roughly 10,000ft. The good news is that they did not explode nor do they appear structurally compromised, thanks to wood/epoxy as a construction method.

Most of our clients have used their boats near where they built them but others have taken their boats from sea level proximity to higher altitude lakes. (These two videos are thanks to Randy and Kim Kerr)

https://www.youtube.com/watch?v=jdLN_QaQrv4. Ross Lake (1,519 ft)

https://www.youtube.com/watch?v=LJV8MJJv6pU&t. Chilko Lake (3,845ft)

Randy replied to my inquiry about his lake trips: "We've never really taken our PT11 higher than 4000' and didn't notice any bulging in the buoyancy tanks personally.  I could imaging customers that span 10K feet in altitude difference could easily see bulging or compressing."

basic air pressure illustration
basic air pressure illustration

Because Russell and I initially imagined our boat builders using their PT 11 dinghies primarily for ocean cruising, the influence of high altitude on the air buoyancy tanks simply did not come up but once in 15 years. That customer installed a relief valve but we never heard exactly what type or how well it worked. We imagined that as a one-off but we are also under the constraints of the USCG rules that prohibit access ports or any compromise of a sealed air tank if it is to be counted as buoyancy. Hence we moved on.

Times are changing however, and it appears that more PT 11s are on road trips and out lake sailing so, it seems prudent to address the air pressure question for anyone planning altitude differentials of more than 4-5000ft with their PT 11 or SPEAR dinghies.

There is an argument for drilling a 1/4" hole on the vertical face of each of the three air buoyancy tanks and filling them with thickened epoxy. (This keeps moisture from reaching raw wood.) If you then notice any expansion at altitude, you have a safe spot to drill a very tiny hole to relieve pressure. The hole could then be taped over until the boat was back at its normal altitude when the new hole could be filled. You would have to choose a time and place with a stable temperature to fill these holes.  In an emergency, go ahead and drill tiny holes to keep damage from occurring. Just know that refilling those holes in a way that keeps the wood dry will be important.

One builder currently working on his PT 11 is planning to use it almost exclusively on mountain lakes and had already researched the pressure valve question before I reached out to ask about it. Have you heard of Gortex Dots? He has generously shared his in depth research and conclusions in this PDF article. An Idea for the Vented Volume Dilemma

The standard rule should still be noted for air buoyancy tanks: no access ports or compromise of the seal unless you plan to fill the voids with flotation foam. These dedicated air tanks (forward of the mast step and the aft seat boxes) are not intended as storage and using them as such could present a serious safety risk if you flood the boat. If you truly need to modify the design to fit your intended use, how you manage that is your responsibility, so be informed, do your own research,  and think 'safety first'.

 

 

THE SPEAR is identical in hull shape to the PT 11, but the interior geometry and construction are quite different and deserve explanation.  The PT 11 has a full width foredeck so that water drains into the aft compartment, otherwise there would be three areas that would need bailing of rain and spray. The Spear can have scuppers through the main bulkhead (the nesting PT 11 can’t) and therefore can have what I call a “trunk” seat.
When rowing with three, the trunk seat allows more comfortable seating for the person sitting in the bow. The areas to the sides of the seat are good for holding oars and other things in the boat.
The trunk seat also keeps the hull from twisting under sailing loads. It’s like a torsion box. (Shown below are the PT11, left, and the beta prototype of the Spear)
ptwatercraft.com

Below photo taken in March 2013 of the prototype being built to figure out the process and to write the manual.

ptwatercraft.comTwo of the watertight hatch kits that we offer as options fit really well in this boat, making the boat versatile for carrying (and keeping dry) groceries, camping gear, cameras, safety gear, etc.
The aft hatch is easier to access when sailing and is great for things like cameras, jackets, and food, but because of the baffles under the back seat (more on that next), the volume of area under the forward hatch is much greater.
While the hatches are work to install, the cost of the kits is very small compared to the utility and safety they offer. They also provide access and visibility to the daggerboard trunk, mast socket, and rudder hardware, not to mention a good place to hide valuables left in the dinghy. Coast Guard regulations play a large role in the interior geometry of the PT 11 and the Spear. This may sound like big brother getting in the way of art, but it’s quite the opposite. The regulations are to protect us, the kit provider and especially you, the end user.
Buoyancy built into the right parts of the boat is necessary for safety. Sealed air voids (compartments) have the same value as flotation foam, but access ports or hatches are not allowed in sealed air voids. If the builder insists on inspection ports, it is then necessary to fill these voids completely with foam flotation in order to comply with safety standards. The Below Photo shows the boat before the deck and back seat lid are installed. ptwatercraft.comptwatercraft.comThe bow area (forward of the mast step bulkhead) is a sealed air void in the PT 11 and the Spear. The PT 11 has built in buoyancy tanks in the back of the boat on either side (outboard) that are equal to the volume in the bow. This is what the Coast Guard wants, and it makes sense.
The Spear has a large back seat area, but because it has a hatch, we have to install baffles to form sealed air voids outboard of the hatch where they would do the most good in an emergency. Though the baffles under the back seat decrease the usable volume for storage, they make us legal and make you safer, and they make for a well supported back seat. ptwatercraft.comBelow; Rowing the Spear with 2

ptwatercraft.comThe finished boat pictured was a beta prototype built summer 2012. Due to less specialty hardware required, the Spear base kit will cost several hundred dollars less that the nesting version. The boat will be lighter by 3 - 5 pounds. The various options, including sailing rig, offered for the PT11 nesting dinghy will be the same for the Spear. As of April 2013, we are taking orders for the "SPEAR" kit.

See our website for full information. PTW:)