Thread: Router vs circular saw vs Concrete Chaser - log cabin build

Originally Posted by lambertod

Hi all,

Does anyone have any advise?

I'm looking to cut 12mm to 15mm wide by 25mm deep by 2500mm long (see drawing attached) into two faces of 150 hardwood logs. What would be the best tool to use router (likely three passes), circular saw ( 4 to 5 passes), a concrete chaser or other?

table saw with dado blade with the logs carried past the blade using a jig

I will insert plywood tongues to make each log tongue and groove. What plywood (marine, structural, etc) would be best to use or does anyone have a better product?

can I suggest waterproof / outdoor ply

Originally Posted by ian

table saw with dado blade with the logs carried past the blade using a jig

can I suggest waterproof / outdoor ply

Thanks Ian,

Another one to think about. I originally discounted using the table saw, as I am working alone most of the time. Even with two people lifting the logs could be arduous and dangerous.

I will also look at using a chainsaw mill and jig. I believe these aren't too expensive on ebay.


Olly

Interesting....

My way would be a router in a jig. The jig would be basically a two sided box with wheels/skids on the bottom and the router on the top; it use it would straddle the log and run along a flat surface (either concrete or piece of ply). Inside the box I'd put some spring loaded guides to keep the log central but allowing for varying log widths.

As for the ply question I would go marine. It's the strongest you will come across and doesn't mind the odd deluge now and again. As it contains many more layers then structural ply it resists warping so much better too.

is it normal in this type of construction to run a spline the length of the log? i say this because the log cabins i have seen usually just have a flattened top and bottom and are butted up...the join is then packed with a filler (mud, in the examples i have seen). I would say it would be quite a challenge to cut those dados top and bottom accurately, to line up (but not imposs).....would require the mother of all jigs. I would think a chainsaw would be the best bet as running rails for router or circ saw to slide along that length, i think, would require a thickness of material that would adversely affect your depth of cut....assuming either tool could plunge deep enough

I saw a few log built structures in Austria last year and I didn't see any splines used at all. I also know of a couple of small places which were built with perma pine logs in South Australia, where the logs were simply dropped into upright C channels and a piece of foam weather stripping was used between the round logs.

Here's a detail of "Rosegger's House" showing how an internal wall faced into an external. The external corners were done in much the same way. In this case they have squared off the timbers but they didn't always do that, some they just flattened the tops and bottoms. This particular house is over 150 years old. Here,s how they did the gutters too. Some other pix from other buildings attached.

Also there is an "open air" museum (freilichtmuseum) in a place called Stubing (or Stuebing) which is actually a collection of old buildings the Austrians have relocated to be all together. A google search on that should turn up a wealth of info.

Regards
SWK

We do the splines in flat gal sheet metal. The groove is a single saw cut and can be done with a hand held circular saw or, for mass production, the Lucas mill. For the mill, we lay the logs side by side to the max the mill can handle, cut the groove in each log, turn the logs and run the grooves on the opposite side. This is a quick and easy process.

I've found this company good to deal with Log Moulder TF230 | Saw Units | Sawmills | LOGOSOL

Good Morning Ollie

I watched a couple of guys building log cabins for a motel in New Zealand two years ago. They used dovetailed corners but round exposed logs. Amazing how quick they worked. Wood was radiata thinnings, about 200 - 250 mm diameter, after debarking.

They used tongue and groove, rather than loose tongues, and said that the bottom trench with loose tongues would retain water and rot out very quickly. Also said that you had to be careful about the taper in the logs otherwise they would not sit horizontal. They said that they first cut a face off the log with a horizontal band saw mill, then cut the groove into that face on a spindle molder; the tongue was then cut with two passes under an overhead spindle molder. This automatically got rid of the taper. I did not see this step as they had a truck load of T&G logs.

As needed, they put a jig over the end of each log, chalked in the cutting lines and cut the dovetails with a chainsaw. NB; the dovetails are tapered in two dimensions - this is visibble in SWK's photos if you look carefully. A vertical tongue or groove was then chainsawed into the other end of the log. Lots of brown sikaflex, and the groove in the log was dropped over the tongue of the previous log. They worked at about the same speed that I typed this!

It looked easy but I guess there was a lot of experience and skill on show.




Fair Winds

Graeme

Originally Posted by ian

table saw with dado blade with the logs carried past the blade using a jig

Originally Posted by lambertod

Another one to think about. I originally discounted using the table saw, as I am working alone most of the time. Even with two people lifting the logs could be arduous and dangerous.

I will also look at using a chainsaw mill and jig. I believe these aren't too expensive on ebay.

Olly

If you go the table saw and dado blade route, I suggest you build an infeed / outfeed "table" about 6m long with the table saw say 500mm towards the outfeed side of the "table"
a suitable table could be made with framing timber using a number of rollers as the "surface"
the log holding jig would run between two long rails and carry the log past the blade keeping your hands and fingers well away from the blade
loading and unloading the jig should occur only on the infeed side (which is why the infeed side should about 3m long)

Process would be
lift log onto table
secure log in jig -- I suggest you use pinch dogs
run past blade
pull back
rotate log 180°
make second run
reverse
unload log

Originally Posted by O2zi3

"is it normal in this type of construction to run a spline the length of the log?" i say this because the log cabins i have seen usually just have a flattened top and bottom and are butted up...the join is then packed with a filler (mud, in the examples i have seen). I would say it would be quite a challenge to cut those dados top and bottom accurately, to line up (but not imposs).....would require the mother of all jigs. I would think a chainsaw would be the best bet as running rails for router or circ saw to slide along that length, i think, would require a thickness of material that would adversely affect your depth of cut....assuming either tool could plunge deep enough

I guess not, but when researching log cabins prior to designing, I came across this design for post and beam framing log cabin design.

I chose post and beam design as I wanted to use my own timber and did not have long poles. It also allows me to have much bigger windows and door opening.

Olly

Thanks all,

Lots to think about and consider.

I am also looking at using my bandsaw and making a carriage to attach a chainsaw.

IMG_1543.jpg

Originally Posted by rustynail

We do the splines in flat gal sheet metal. The groove is a single saw cut and can be done with a hand held circular saw or, for mass production, the Lucas mill. For the mill, we lay the logs side by side to the max the mill can handle, cut the groove in each log, turn the logs and run the grooves on the opposite side. This is a quick and easy process.

I like the flat gal sheet metal splines. Where do you get these from? What are the sizes?

Have you got any links/photos on the Net?

Olly

Olly, There's nothing scientific about the splines. I get them cut by our local sheet metal fabricator. They are simply guillotined from a sheet of gal and then we just dock them to length required on site.
The construction method you are intending to use is known as drop log. This lends well to short logs. Another method would be vertical slab. Again, a good method for short material with the added bonus of overcoming vertical shrinkage as timber doesn't shrink much in its length. If your logs are seasoned, shrinkage is not a major issue. Likewise for post and beam, though you need to make arrangements for the gap that will form between your top beam and top log. Shrinkage in hardwood is considerable. It could be as much as 200mm over a 2.4m wall height. An inner and outer fascia board, of sufficient width, fixed only to the beam, will overcome the problem. If you go to the method of end nailing your logs to the posts you will decrease the amount of shrinkage drop as the logs will remain in position and only shrink away from each other. This method then must be chinked and in the case of hardwood, regularly as there shrinkage is much greater than fir or pine. Personally, I prefer to allow the logs to move down the posts as they decrease in diameter, as this means a lot less maintenance.

Sorry, you did ask for sizes.. The splines are cut to approx 100mm. This width allows them to reach through the sap wood of the logs and into the true wood. This is important as, with time, the sap wood will degrade and compromise the seal. If your logs have more than 25mm of sap wood, increase your spline width to allow 25mm penetration into true wood.