How would you make this?

[Beau]

I see these style of saunas are catching on over here but unsure as to how they cope with all the expansion and shrinkage involved. Doing some quick estimations and the outside circumference could be expanding and shrinking by 60mm or so seasonally. Can a thin stainless band stop this or do you think it would only be tight when wet and have gaps and leak when the weather was dry?

Any thoughts on the subject as I have been asked to make one but dont want it blowing itself apart come the winter. Gut feeling is it's trouble but there are plenty of makers of them out there. https://www.britanniahottubs.co.uk/webs ... sauna-6x6/

 

[MikeG.]

Half-lap joint at each board edge. If you build it in summer, board it loosely. If you build it in winter, board it tightly.

 

[Sheffield Tony]

Just because there are plenty out there doesn't necessarily mean it's a good idea ...

You would think it would fall apart in summer or burst the bands in winter. Barrels aren't straight sided for a reason. But, perhaps in softwood there will be enough give for it to work. In hardwood, I share your doubts.

Now where do you buy really big jubilee clips ?

Edited to add - perhaps, as a sauna, it is expected to stay damp enough all year round ?

 

[Beau]

Exactly my thoughts Tony.

Just the question of whether cedar would be soft enough not to blow the bands apart. But then next time it shrinks would the cedar not have crush marks?

 

[dzj]

Perhaps if the "barrel hoops" were spring loaded in some way, you could avoid the expansion issues.

 

[Beau]

Now that's a very good idea. Could hide them away underneath and out of sight. Thanks

 

[Alex H]

Following your link, I read that it's made from "Ball-and-socket lumber" whatever that is :?

Google led me to this US makers web site SAUNA

"Rozycki says his True Bent Stave Barrel Saunas uses a traditional cooperage approach with stainless steel hoops, not screws or glue, to hold the structure together. "This type of traditional construction is an art-form and woodworking achievement within itself," he says.

The Bent Stave Barrel Sauna is made with "a ball and socket joint, creating a weather-tight seal," Rozycjki says. "This key feature will keep the staves properly aligned for years to come." Features include a door with a tempered glass window, full-length sauna benches, waterproofed stained exterior, and smooth finished interior."

Any clearer?

 

[Phil Pascoe]

Just because there are plenty out there doesn't necessarily mean it's a good idea ...
Barrels aren't straight sided for a reason.
Edited to add - perhaps, as a sauna, it is expected to stay damp enough all year round ?

No, but a sauna isn't built to contain a load. The inside of a sauna is far from damp.

 

[ED65]

Presumably the stainless bands are just there to help hold the thing to shape, given how skinny the strapping is I can't imagine it serves the same purpose as the substantial steel or iron bands around oak barrels, which anyway scale up and increase in number as the barrel diameter increases.

I can't make out any useful details from the tiny pic, and maybe there's something about cylindrical forms that doesn't directly translate from the flat, but surely there has to be something that allows for movement?

 

[Phil Pascoe]

I can't help with the shape, but I am probably one of the very few people here who've actually built a (15Kw :shock: ) commercial sauna. If you buy timber from a sauna specialist it will be kilned to death - it's almost like it never lived. I used it working on the first one but decided to go a different route with its replacement, which I designed and built alone - for this I used good quality redwood (there used to be a brilliant timber merchant nearby before bad debts put him through) and designed everything to be easily taken apart and repaired. The panelling on the walls dropped seven inches over the first few weeks - so I dread to think of the difficulties involved in something of that shape and design. Incidentally mine is still there after seventeen years.

 

[sunnybob]

you use a router table or spindle moulder to make what looks (end view) like a ball on a stick, and in the other side of the same plank you cut the reverse shape. Slide one plank into the next. T&G with side movement.
The ball stops the planks falling apart and allows massive movements while still holding together.
theres no structural weight on the wood apart from the wood itself, which is held in roughly circular shape by the steel bands.

the internal seats are solidly built to take the weight.

 

[Mr T]

The linked web site shows that the staves are edged with a concave curve on one edge mating with a convex on the other which allows them to be angled slightly. Doesn't account for how to keep them all together when they shrink which Sunnybob's solution does, but quite complicated!

Chris

 

[custard]

On the Felder web site there’s a projects section showing them, step by step, using their machinery to make various items. I think one of them is a hot tub and from memory it shows in detail them spindle moulding the “ball and socket” joints.

 

[Just4Fun]

you use a router table or spindle moulder to make what looks (end view) like a ball on a stick, and in the other side of the same plank you cut the reverse shape. Slide one plank into the next. T&G with side movement.

Having recently struggled with some sliding dovetails that were 400mm long I hate to think how any joint as long as that sauna would slide together, especially without any taper. I would have thought the joints would have to go together by moving the pieces at 90 degrees to their length, not along their length. Or am I misunderstanding something here? Is there enough play/movement in the female part of the joint for the male part to click into place sideways rather than being slid in lengthwise?

 

[Beau]

Yes sorry I should have said I am clear on the ball and socked (they all seem yo use this joint) as I have used this before in boat building. It's dealing with the expansion and shrinkage which is what concerns me. The metal band is what holds the strips together just I cant see how it will cope with the amount of movement you will get seasonally.

 

[Beau]

https://www.youtube.com/watch?v=02zfzFhMO14

So I found this and you can see that the band is pulling it together. They make allowances for movement of the dividing panel and have an expansion gap but nothing to allow the band to move with the cedar without crushing it, snapping or being slack when it's dry.

 

[Yojevol]

 

[novocaine]

5th or 6th picture down the list.
they are held with a stud, you tighten it in the summer and loosen it in the winter.
having said that though, if it's used all year round you'll be pumping moisture in to the wood all year anyway so it shouldn't see large seasonal variance.

 

[Beau]

5th or 6th picture down the list.
they are held with a stud, you tighten it in the summer and loosen it in the winter.
having said that though, if it's used all year round you'll be pumping moisture in to the wood all year anyway so it shouldn't see large seasonal variance.

Yes all is good if you have smart customers and it gets used all year round. But if you dont.............

It wont be cheap and I dont want to get moaning phone calls that it leaks or the band has snapped etc etc. Looking into the spring idea mentioned further back as it would solve the issue but it would need to be a tough old spring

 

[Beau]

Just watched the Felder video mention by Custard. Heavy duty bands on something that will stay wet so not much movement but some of the saunas have something closer to a Jubilee clip!