The aPEX of the Floor? –Lance the XRV weekly update 29 Sept. 2024
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
Barney as many of you might know gets all the credit for putting Christine and I together in the first place and if you have not heard THAT story already, you can read all about it 
One of this little Black & White girl, 
No surprise that it was literally love at first sight as you can likely see in this first photo I took of Christine holding our new “babies” with their strawberry blonde Havapoo Mommy in front and all black toy poodle Daddy on the left. 
The intersection points were just too much as learned that Mom’s name was Ruby (not making this up!) and Dad “Tegga” was her spitting image as you can see here. 
They had all spent their life so far in this fabulous grassy backyard and we spent the rest of the afternoon playing with them and getting answers to our unending questions from the owner. 
They had never been in a vehicle before so their breakfast didn’t last too long but otherwise the nine hour drive back to Klamath Falls went very well as you can see. 
We stopped at many rest stops along the super scenic drive on another sunny day. 
Including over an hour exploring the park along the river in beautiful Bend, Oregon.
and were soon walking them into their new home before dinner Tuesday night. 
We had picked up a foldable pen at the pet store in Wenatchee along with a new dog bed and set that up with what we had always called “the Barney Blanket” and they settled right in. Our first night together went eXtremely well as they slept through the night snuggled on the bed with us and never stirred until 7:30 the next morning. 
We have decided to call this little guy “Razzcal” or “Raz” for short and he has definitely been living up to that choice with all his antics. Already overdue for a haircut as you can see and he share’s a LOT of traits with Barney including his short little legs. 
His slightly bigger sister is “Zoe” and as you can see she is very stressed in her new home.
First time on a leash, along with a loooooong list of firsts for these two, but they are filling our hears with joy already. 
The XAL comes in a large variety of sizes and profiles such as this one which I’ll be using to create rounded corners on some of the cabinets. 
I will mostly be using what is called 10 Series XAL which is all based on 1” square modules with these dimensions. This version with slots on all four sides is the most common that I’ll be using. 
And
Or you can start to have multiples of 10 Series such as this 1×3 extrusion that I’ll be using for the perimeter of the lifting bed frame for the extra stiffness this needs. 
Then there is an even larger number options for fastening two or more pieces of XAL to each other. The simplest and most common use one of these different types of T-nuts which slide in the T-slots and have internal threads you can bolt into. 
Such
As you may recall from the blog post back on July 15th 
You can now start to see why I spent the time to create a very accurate 3D model of the framing of the Horton box that I am now turning into Lance’s “Happytat” as I now chose to spell the more common term of an ambulance’s habitat. 
I
I
3D modeling in Fusion is very straightforward, I simply chose one of the Master XAL profiles such as this rounded corner one, place that in the model and use the “Extrude” command to stretch this out to whatever length I need. 
And just like that, I’ve got the first corner of what will be the framing for the cabinet with the 2 burner induction cooktop at the Front Passenger Side (PS) by the entry door steps. 
Repeat the same process for each of the other lengths of XAL to build this cabinet using the profile needed for each one. You can see that I assigned different colours to each profile to make it easier to know which was which as the framing grew. 
Continue with a lot of “rinse & repeat” and the interior framing starts to take shape. 
The devil is indeed in the details and so it took several weeks worth of very long days to work out the correct profiles and how every intersection needed to work but it has been paying me good dividends ever since and well worth the effort. 
Total cost seemed pretty reasonable to me at $2179 plus $614 for shipping and $20 for double cardboard wrapping to prevent damage so the total cost of all the XAL delivered to me came to $2814. Total weight of the shipment was 650 pounds. 
Going back to the beginning a bit, this is where we left off last week having installed all the PIF (PolyIso Foamboard) insulation and the ACM panels on the walks and ceiling. 
And going back ALL the way to January when we went and picked up Lance in Illinois, here is what the original floor and interior looked like. 
Prep work on the floor began with removing the vinyl diamond plate flooring and then the eXtremely recalcitrant aluminium track you see running down the center of the floor in the photo above. This track is what the collapsible Stryker ambulance stretcher rides on and locks it in place. For safety and security this 25mm/1” thick AL track is through bolted into the floor framing below with large high strength steel bolts. 
The floor material you see here is 13mm / 1/2” thick ACM that will make a great substrate to embed the 1/2” PEX tubing into the floor later to circulate the hot floor heating liquid through so I wanted to be able to reuse this huge continuous sheet. To do so I carefully cut through the ACM floor lengthwise along one side of the track’s slot using my cordless circular saw and a long straightedge to get a very straight edge that will later become a butt joint of the two halves in the new floor. 
You can see how clean and square an edge the carbide blade in the circular saw leaves on the ACM and will make for a smooth seamless transition between the two halves when I reinstall them later. 
The ACM flooring was through bolted to the 2” x 3” AL floor frames below but not glued in place so once I had all those bolts removed I could pry the ACM up to remove it.
I was then able to flip each half of the ACM floor up as you see here. 
Several of the bolts fastening the ACM to the AL floor frames had sheered off when I was removing them so I brought out some of these Weapons of Mass Deconstruction to remove them. 
This shot as I’m removing one half of the floor gives you an idea just how large the original ACM flooring was. A single sheet about 4.25m / 14’ long by almost 2.4m x 8’ wide! 
So I spent several hours scraping off the tar matt in that rear DS corner to clean that all up. 
Final preparation for the new flooring began with trimming up the two halves of 1/2” ACM I had removed previously. In order to get a continuous straight tight joint down the middle I turned one half of the floor ACM end for end and resawed this edge to be perfectly straight. 
I dry fitted each half in place to get all the cut outs around the external storage compartments along each side and then slid the ACM halves back out and was finally ready to start installing the new flooring. 
First layer of the new flooring is this 1/2” thick PIF (PolyIso Foamboard) that is faced on both sides with AL foil. 
As you saw me do with the ACM above, I cut and fitted the PIF around all the compartment cut outs and soon had the first layer of the new flooring all in place. 
Next layer was the 1/2” ACM so I carefully laid that in place on top and used some lengths of 2×2” square AL tubing for straight edges to compress the ACM to the PIF and make the floor flat and seamless. 
That center joint between the two halves of ACM worked out very well as you can see here up at the front wall. 
I cut new pieces of 1/2” ACM for areas I had cut out the original external compartments and glued them in place. This new ACM is the same as the original, just has AL faces that are white. 
If
The final layer before I can route the grooves for the 1/2” PEX tubing for the heated floors is a layer of new 4mm ACM. Pretty straightforward; 4×8’ sheets are trimmed to fit around all edges and then the protective plastic is peeled off the bottom surface. 
The same DAP/Weldwood Landau HHR contact adhesive you saw being used last week on the walls and ceiling is poured into the electric HVLP spray gun. 
Top and bottom AL surfaces are covered with a thin film of this contact adhesive. 
…… and with Christine’s help, carefully lined up and lowered the gooey panels into their final resting place as you only get one shot with contact adhesive that grips for good immediately. 
Which takes us back to the end were I began this week’s update so I’m going to leave off here for this week and pick up next.
Instead the longest single piece of foam board I could fit into one of the open areas between the reinforcing plates plates was about 50cm/20” long. 
The 2” gap was a bit too perfect of a fit for the 2” thick PIF boards and so they needed some force to get them to slide across. The foam is very fragile of course so I made up this “persuader” from a length of 2” square AL tube which just fit into the cavity and covered the full thickness of the end of the foam and I could tap them through the opening. 
Other reinforcements in the form of these 45 degree corner braces that were welded into many places on both the walls and ceiling and this made the whole cut and fit process a bit more finicky and time consuming. 
Another Goldilocks factor in choosing to use these Sika PIF boards was that they cut very cleanly with a carbide saw blade and so I was able to get very clean square edges using a combination of my table saw and cut off saw. 
I wanted to get a good press fit everywhere the foam fit into these bays and of course each bay was just a bit different width so I had to measure and cut each one individually and cut the 45 degree corners where needed so it took me several days to complete the whole process but well worth the time to get close fits throughout with no need for any adhesive or spray in foam filler. 
Here
Whew! Ceiling all done, now onto the walls. 
I started with the walls in the DS Drivers Side front corner and worked my way out from there. 
There was still a good bit of fitting required as the length and width of each piece of PIF was different but it all went well. The blank space here is for the windows you saw me install in the previous post. 
Rinse and Repeat as they say and I worked my way around all four walls. 
It
Now on to the second layer of 1” PIF insulation I added on top of the first layer of 2” foam boards. This went MUCH faster of course as I could now put up large sheets starting with this first full 4 ft by 8 ft sheet in the DS front corner. My adjustable support poles and lengths of extruded aluminium bars came in very handy to glue each panel to the ceiling. 
More rinse and repeat cycles and it didn’t take long to finish gluing this 1” PIF to the whole ceiling.
As per this illustration, ACM is two outer layers of thin aluminium with a layer of polyethylene sandwiched between. It comes in pretty much any colour you want but we stuck with the most common white. 
Both
Before I started to install the 1 inch thick 2nd layer of PIF on the walls, I started installing the ACM panels on the ceiling because I wanted to foam on the walls to butt up against this. 
Peeled off the protective plastic layer from one side and …. 
…..
Also available in these aerosol spray cans for smaller jobs but I just used a cheap $77 electric HVLP spray gun from Harbor Freight which worked very well. 
Same basic technique that you saw above for the 1” PIF panels, I used lengths of extruded AL and my adjustable support poles to clamp each panel in place. 
Goes very quickly when you are working with these larger panels. 
Ceiling and front wall fully clad in ACM, now on to the walls. 
Same as with the ceiling, I glued on the second layer of 1 inch thick PIF board to all the walls and sealed all their seams with AL tape. 
Then I could cut all the ACM panels for the walls, spray both wall and ACM panel surfaces with the special DAP Landau Top & Trim HHR adhesive…
….
Last surfaces were the external access storage areas and these were first covered with 1 or 2” PIF and their seams taped and ready to be covered in the final layer of ACM. 
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