DIY Hot tub of wood
Wood is a material that inspires time and again today, we are confronting a special challenge. We combine wood with the most original of all elements, water. Our carpenter, Helli, is building a heatable hot tub, also known as Hotpod or Hottub. He will show you every step of this project in this Felder Do-it-yourself video. Join us in its development and, together with us, build this highlight of fun, joy and above all, relaxation. We use the Felder combination machine CF 741 SP the all-rounder for modern woodworking – for this project. A perfect combination of 5 stand-alone machines with only square metres of space required. Planing, moulding, cutting and drilling a top quality workshop in one machine. As always, we provide you with the construction plan, along with the necessary software for download.
The Siberian larch, a very hard and extremely weather-resistant wood due to its high resin content, serves as starting material for our hot tub perfect for our project! When working with four metre long boards, a height-adjustable work-table such as the Felder FAT300 is a real relief. We cut the boards to measure. Next is the trimming. We set up our machines quickly and easily for this. The crosscut fence can be disassembled in no time. Assemble the edging shoe and all done! The table extension at the end of the table is very helpful when edging. And one more tip: the saw blade of the Silent-Power rip saw blades are ideal for longitudinal sections. With the smooth running “X-Roll” format sliding table and its linear guiding system, trimming the boards is a walk in the park. For the next task, the surface planing, we only need to set the parallel cutting fence on the planer table and open the cutterblock protection.
The traditional planing of the floorboards guarantees absolutely perfect results, but can become strenuous over time with long and heavy workpieces. We therefore opt for the more comfortable version with feed. This makes the planing much easier for us. We then plane the joint with a manual feed. Once again, the table extensions prove to be of great help. Master carpenter Helli uses the patented “Silent-POWER(r)” spiral cutterblock from Felder which guarantees uniquely perfect planing results. For the first thickness planing, we adjust the thicknesser table to a median size of the boards.
The feed speed can be set between 6 and 12 meters per minute. The floorboards must now be provided with a tongue and groove profile, and we use the Felder Universal profile cutter for 40 and 50 mm cutters. The top of the moulder should just “scratch” the piece of wood for this purpose. We set this position as a zero value and adjust the milling height to the centre of the workpiece. The feed once again guarantees safe, convenient and fast working. The workpiece is pressed perfectly against the machine table and the spindle moulder fence by the three spring-loaded rubber rollers thereby supports the repeatability. Step 1 is completed, the “groove” is moulded on all boards.
Step 2 is the moulding of the “tongue”. Only the cutting blades on the universal profile cutter head are replaced for this purpose. All settings on the moulder can remain unchanged. The test shows: it fits perfectly! The floorboards are now almost finished, we proceed with the cutting of the “staves”. We start with the cutting to “basic size” again. The height-adjustable Felder FAT 300 working table in turn provides optimal support when cutting the four meter long boards. Machine equipment trolley, stacking trolley or stable work space, this height-adjustable Felder FAT 300 work table is versatile and always offers maximum stability and easy mobility. We plane the 90-degree joint on the boards right after trueing this time. Our professional tip: with the CF 741, similar boards can planed to thickness even at the same time. In this way, we achieve 100% time savings and speed up this task enormously. The maximum depth of cut / chip thickness during thickness planing is 4 mm. we choose a mean between the thickest and thinnest board again. This way, we can leave the thicknessing height unchanged. With 6 metres of feed per minute, we achieve the best possible planing result. We proceed with cutting our staves. For this purpose, we use a Silent-Power steep-tooth saw blade, perfect choice for cross cuts.
The swing-away crosscut fence stop guarantees additional operating comfort and highest precision essential for the additional processing steps. In order to bring our staves into the right shape, the moulding of the groove and the corresponding curve now follows. We start with the rounding profile and align it to the middle of the stave in height. It is particularly important in this step that the profile is moulded absolutely evenly! Our feed is extremely helpful again here. A sample piece may be used for the fine adjustment of the groove. With the help of a calliper, master carpenter Helli checks the cutting height and also whether the staves can be turned in far enough to achieve the exact radius of the hot tub. In the Power-Drive control, the grooving tool is already stored, we only have to conveniently adjust the height by means of a digital indicator. For the connection of the staves with the barrel bottom, we mould its thickness into the staves. By means of the side cutter of the moulder, we adjust the moulder precisely to the base dimension.
We mould the groove in two steps and use the cutting and parallel cutting fence for this. We can perform all cuts with the same setting this way. The test shows it fits perfectly! The fit should not be too loose but also not too tight. We can now get the axial dimension at the fully moulded stave. Together with the number of staves, it determines the diameter of the hot tub. When assembling the floorboards, we make sure to use the broadest possible boards at the edge.
Tongue and groove fit perfectly, just as we expected. We now measure the centre point then use a circular board to mark the outer diameter as well as inward diameters offset by 10 and 20 mm, respectively. With a tensioning belt, we fix the floorboards for the installation of the under-floorboards. These are installed at the same distance, and the innermost diameter is marked after that. We use our circular board again for this.
We use a Felder FB 510 bandsaw with a 20 mm blade, an X-Life ceramic bandsaw blade guide and a laser cutting display for the cutting. We use about 4 centimetre wide boards that we have already cut to the right length for the under-beams. Using a multi-function marking gauge, we mark a centreline, pre-drill the holes and screw the boards together. Our master carpenter Helli recommends robust stainless steel screws for this use. When screwing the under-beams to the base plate, we ensure that there is one screw arranged in cross-wise manner for each floorboard. We can then already cut out the curve of the base plate. For this, we use our height-adjustable Felder work table and our bandsaw again. We quickly remove protrusions with a planer. Now we can install the staves. We already assemble the whole construction into finished position so that we don’t have to turn the heavy hot tub over later. For this, we transferthe 10 mm lines to the upper surface using our multi-function marking gauge.
This line then serves as a depth-marking for the staves. Our hot tub is slowly starting to take shape now. When installing the last stave, we turn the second to last one slightly outwards. Thus, the whole construction then slips into its final form. For the installation of the hoops, we pre-tension the staves with two tensioning straps, check the depth on our 10 mm line and re-adjust the staves as needed. Our hot tub is almost completed now. The only thing missing now is installing the accessories. The most important element is the heater. We opted for an aluminium model. We position the heater so that the mounting holes are as centrally as possible in the staves. It is important to tightly screw the heater to the tub. We recommend M8 stainless steel lock screws. As a final step, the interior construction follows. We cut the material to size, plane the boards and mould the profile with a joining cutter head.
The joining function of the moulder eliminates the need for prior joining work. For the construction of the bench, we determine the centre point by way of three measurements. Then we draw a parallel to the heat protection. We use an angle measurement tool with a clock here. We now mark out the corners from the centre line and then mark the bench boards. Having measured the bench boards, we can adjust all the measured dimensions directly on the crosscut fence thanks to the precision mitre guide on our CF 741.
The length compensation then takes care of the rest. And our hot tub is already completed!.
As found on Youtube