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Author Topic: Cruck Frame No 2
Ken Hume
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Posts: 430
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Post Cruck Frame No 2
on: January 5, 2017, 20:09
Quote

Layout and preparation of the centre (2nd) cruck frame was started on a bright cold sunny January day when 2 cruck blades were selected from the storage stack and pulled up onto the sill frame using the Land Rover to tow same into position.

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The 1st cruck blade is quite substantial and required profiling at the base and top ready to lay up with the 2nd cruck blade.

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After undertaking some localised bulk removal of wood at the base and top the 1st cruck blade this was planed to a regular shape to ease scribing and fitting into the long sill cogged joint at the base and apex lap joint

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The 2nd (centre) cruck will be laid out in series with the 1st cruck.

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The centre crucks are a little more substantial when compared with the two end wall crucks being 7.5 - 8" thick and so it was decided to hew a similarly dimensioned collar to fit the cruck blades

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Ken Hume OWG

Ken Hume
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Posts: 430
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Post Re: Cruck Frame No 2
on: January 17, 2017, 18:06
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The first sidewall post for cruck number 2 was hewed to produce a good boxed heart timber.

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The centre crucks overhang the end cross sill and so a simple extension to the framing floor was made using a pallet and plywood with a string centre line and nail over which the crucks were aligned.

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After scribing and cutting the apex lap joints the crucks were fitted together and clamped to hold them in place.

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Now that the cruck blades were positioned in the same plane the cruck mantle (tie beam) was laid on top ready for scribing.

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M Griffin cut the cruck blade and mantle lap joints -

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- and then fitted the mantle to the cruck blades.

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Upon closer examination the cruck mantle (although fitted perfectly) showed signs of potential weakness in the smaller end which began to give rise to concerns that this might fail once the sidewall post and principal rafters mortices were made and so the decision was made to change out the larch mantle for a larger section Douglas Fir mantle.

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Ken Hume

Ken Hume
Administrator
Posts: 430
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Post Re: Cruck Frame No 2
on: February 19, 2017, 09:53
Quote

Work proceeded to fit the cruck collar prior to replacing the cruck mantle.

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The cruck blades were scribed and cut to form lap seats upon which the collar was set and scribed -

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- ready for cutting the mating lap joints in same.

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Work then proceeded to replace the European larch mantle with a better quality Douglas Fir mantle.

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This was laid up on top of the old mantle and positioned ready for reducing the length of same from 19ft to 17ft

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The cross section of the Douglas fir mantle is much more substantial (9" x 9") at the butt end of same and will require a similarly sized sidewall post.

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The cruck blade lap seats were recut to accomodate the replacement cruck mantle -

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- and then the mantle was scribed and cut -

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to fit the cruck blades.

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Ken Hume
Administrator
Posts: 430
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Post Re: Cruck Frame No 2
on: February 19, 2017, 10:03
Quote

A 2" mortice with sloping shoulder was scribed and cut on the mantle centre line -

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- to accept the tenon at the foot of the first principal rafter.

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In cold and sometimes snowy weather the first principal rafter was laid up -

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- and scribed to fit cruck frame no 2.

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The principal rafter was then laid up on top of the mantle, collar and apex to match mark the collar / principal rafter mortice and tenon.

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The top of the principal rafter was then adjusted to fit the apex by making a series of kerfing cuts until a perfect fit was achieved.

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Ken Hume OWG

Ken Hume
Administrator
Posts: 430
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Post Re: Cruck Frame No 2
on: February 19, 2017, 10:15
Quote

The first sidewall post was matched to the large end of the cruck mantle and some reduction by hewing was undertaken together with hand planing all round to produce a nicely finished post.

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The post top tenon is a heavy duty 2.5" wide and this was formed by saw cutting rather than progressive kerfing and chopping away waste wood.

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The sidewall post was laid on top of the mantle and bottom of the cruck blade and match marked ready for cutting the cruck lap seat housing and tapered profile to match the curve of the cruck blade.

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The rough slope at the bottom of the post was then cross cut saw kerfed, pared and planed to produce a "half tabled scarf" type joint.

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The post was then offered up to fit into the mantle mortice as far as possible recognising that there would be slight misalignment -

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- until a step lap seat is cut into the outside face of the cruck blade as marked to accomodate the step lap at the bottom of the sidewall post.

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The centre cruck frame is now beginning to take shape.

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Ken Hume OWG

Ken Hume
Administrator
Posts: 430
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Post Re: Cruck Frame No 2
on: February 21, 2017, 19:10
Quote

The step lap seat in the lower outside face of the cruck balde was scribed and cut out by :-

- kerfing
- removal of waste by mortice chisel
- flatening the face using a Wetterlings hewing axe
- finishing the face with a plane and paring chisel.

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The misalignment of the sidewall post top mortice & tenon has been eliminated following the sidewall post being pulled into the step lap seat in the cruck blade.

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Ken Hume OWG

Ken Hume
Administrator
Posts: 430
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Post Re: Cruck Frame No 2
on: February 26, 2017, 09:17
Quote

The European larch centre cruck mantle that was rejected and replaced with an uprated Douglas fir version (see above) was cut down to form the 2nd sidewall post and a good size match between the sidewall post / cruck blade & mantle was achieved.

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The step lap seat between the cruck blade and 2nd sidewall post was scribed and then cut to the "spring lines" to ensure a good tight fit between the sidewall post / mantle and blade.

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A few days later when the spring sun decided to shine the tarpaulin was stripped off the framing floor to reveal complete cruck frames Nos 1 & 2

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The centre cruck frame is now complete !

Ken Hume OWG

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