OK, I’m back from the detour we took here last week with the arrival of our two new Havapoo puppies “Zoe” and “Razz”.  If you missed it you can read all about them HERE.  They continue to entertain and delight us non stop as well as grow non stop so all is well with them.

In the last post on the build progress back on Sept. 8th called “We’re Floored” I left off having completed the installation of all the foil backed PolyIso Foam boards or PIF insulation in the walls, ceiling and floor and covering them with sheets of 4mm ACM or Aluminium Composite Material as per this photo at that stage.
The floors were made of this Lance Club sandwich that starts on the bottom with the 4mm AL floor plates of the original Horton ambo box, then a 3mm layer of rubber matt, a 13mm/ .5 inch layer of AL foil faced PIF R3 insulation topped with a layer or 4mm ACM.
The floor was now ready for the next step in its evolution; embedding all the runs of PEX tubing through which a heat transferring liquid that will flow, turning this into a thermostatically controlled heated floor. 
For those unfamiliar with it, PEX tubing is a cross-linked polyethylene pipe manufactured using extrusion method that creates infinite lengths of extremely strong and flexible tubing.  It has been around for over 50 years and has largely replaced the use of copper and PVC pipes for plumbing in residential and commercial buildings.   It is readily available in coils up to 500 feet and sizes from about 6mm/ 1/4” up to 2” with 1/2, 3/4 and 1 inch being the most popular.
I have had great success using PEX for plumbing other projects over the years and it is pretty much the go to tubing for hydronic heated floors in any building.  We used this for the floors in our previous boat Mobiüs and once you’ve had heated floors you never want to be without them again and this was one of the givens when we started to design Lance.  I will also use PEX for all the plumbing of our hot and cold water systems in Lance so you’ll be seeing it quite often here as the build progresses.
Our hydronic heated floors simply have loops of PEX tubing embedded into the flooring through which a heated solution of glycol (anti-freeze) and water flows and transfers the heat from the liquid into the flooring.  This heat transfer fluid will be heated by the diesel fired boiler we have for our onboard Domestic Hot Water or DHW which makes it a very important bit of kit for our day to day living so you’ll also be seeing much more about this in coming update posts.
We’ve decided to use the Oasis Zephyr 33k BTU model from International Thermal Research or ITR as this is the same company that made the boiler in my first boat “Learnativity” that worked very well and yes, I’m a wee bit biased as this is a Canadian company based out of Richmond near Vancouver BC where I lived and taught for many years.
I had ordered three 100 foot long coils of  1/2 ınch ID PEX type A (more on that later) in Red and Blue for Hot and Cold water and White for the heated floor loops and I did some experimenting with different ways of embedding this tubing into the flooring I’d just installed in Lance. 
The PEX tubıng ıs 1/2 ID Insıde Dıameter and 5/8 ınch OD so I used a 5/8 ınch core box carbıde bıt ın my Bosch router and
one for my smaller cordless Mılwaukee router to get ınto smaller spaces.

These bits cut a just right groove into the test pieces of the floor sandwich.
I had also ordered a box of these special aluminium heated floor transfer plates that are typically used in plywood based radiant floors but I wasn’t satisfied with the way they fit.
Even after some judicial flattening with a hammer these plates just would not lay completely flat and created an air gap that would not have been as effective in transferring the heat from the PEX tubing into the surrounding AL flooring, and this would have also created a slightly non flat surface for the finished floors which was also not acceptable.
It would have worked OK to just press the PEX into the grooves but I wanted to maximize the heat transfer so I used some thick 5 mil aluminium ducting tape and carefully pressed this into the grooves.
….. and that gave me the Goldilocks just right fit I was seeking.

Planning for the heated floor began with laying it all out in the 3D model in Fusion 360 which I did several months ago starting with this sketch of the routing for the 1/2” PEX tubing.  3
Once again my 3D modelling for Lance paid off by allowing me to get the just right layout of the lengthwise running PEX tubes.
Once I had the spacing and layout all worked out I simply used the “Sweep” function in Fusion 360 to follow the sketch line and create the model of the tubing itself.  The minimum bend radius of this 1/2” PEX-A tubing is 6 times the 5/8” OD so 3.75” and I increased this to 4.5” for a bit of safety and that’s why there are those round abouts as each run of PEX makes the U-turn to go back the other direction as you see here.
With all that planning in hand I used some 1” wide blue masking tape to lay out the location of the 1” wide eXtruded Aluminium or XAL cabinet framing that will be bolted to the floor so that I could be sure that the PEX tubing would not interfere with this.  You can see that I traced out the center line of the PEX tubing with a felt pen to help me position the router.
I cut out this jig from some scrap 5mm ACM from the original build and used this to guide the base of the router to make this sweeping omega shape for the U-turns at each end.
To make sure that the open end of the Omega shaped jig was the proper distance I made this short piece to press fit between the two legs of the jig and then marked two lines where the actual PEX tube center lines of each leg should be.  This made accurately positioning the jig very quick and easy.
Once I had the jig precisely positioned to my felt pen marks, I secured it to the flooring with three short screws to hold it in position

Then with the outer edge of the base of the router pressed tightly against the inner edge of the jig I was able to guide the router bit along the just right track. 
I made three passes starting with a shallow first cut of about 5mm deep and

… worked up to the full depth of just over 5/8” which if you look closely you can see was just cutting into the thin bottom layer of AL on the ACM of the flooring.
Quick test fit using a short piece of the PEX tubing and I was ready to go.
Reposition the jig for the next cut ……
……..  rinse ……..
….. and repeat ……….
There were a few places where the base of the larger Bosch router were too big so I built a smaller jig and
……used my cordless Milwaukee router to cut those grooves.
Used the same jig and router to cut these grooves where the PEX tubing enters and exits into the external compartment where the diesel boiler will be.
And that completed all the router work and all was groovy.  (sorry, couldn’t resist)
Next I peeled off the protective layer of plastic with all the blue lines and arrows, from the ACM floor and started to press in the AL ducting tape to line each groove.
The AL ducting tape is eXtremely sticky on the back but I was able to fold each 3” wide length in half, peel off the paper backing ………..
…….. and carefully set it into the bottom of the groove.
Then I could use a combination of my index finger and ..
The end of one of my vacuum nozzles that conveniently had just the right radius to press the sticky AL ducting tape onto the sides of the grooves.
For the radiused U-turns I used the same technique to insert the folded tape lengths into the groove and then sliced the outer edge so I could bend the tape over and stick it tight against the ACM.
Putting my weight on the plastic roller worked well to get the tape very flat and well adhered to the ACM.
Ta Daaaa!  All done and ready for the PEX tubing to be pressed in place.
Where the PEX tubing enters and exits the mid Drivers Side external cabinet I needed to come up with a way of protecting the PEX from the edges of the AL holes I had drilled through. 
These plastic fittings are normally used for electrical conduit but they worked just perfect for both protecting the PEX and creating a watertight joint where they pass through.
With the help of my (headless) Beautiful Bride and my trusty sledge hammer we were able to feed the PEX back and forth into the grooves and then back
…..into the compartment where I could slide on the other parts of the fittings and tighten them snuggly in place.
Worked out very well.
Final step was to put AL ducting tape over the top of all the PEX tubes and the floor is now ready for the final layer of 4mm ACM to go on top and that is where I will pick up tomorrow morning to start another week working on Lance.
So that’s a wrap for this week and hope you found it a bit interesting and will join me here again next week to see the next phase of putting in our finish flooring.

Thanks for your time and endurance reading all through this and please leave any questions and comments in the “Join the Discussion” box below.

-Wayne