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Author Topic: Cruck Timber Conversion
Ken Hume
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Post Cruck Timber Conversion
on: May 7, 2013, 08:20
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Work commenced (17 Apr 2013) on the felling and conversion of trees to be used in the cruck frame building project at Oxford University's Arboretum at Nuneham Courtney, South Oxon. The trees being used are ones identified as posing an unacceptable level of risk to the visiting and passing public and have not been specifically selected for the purpose of cruck building.

The trees are being converted by Matt Melton of the South Downs Greenwood Centre using a powerful Stihl chainsaw fitted with Alaskan sawmill attatchments.

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The Stihl 088 (now model number 880) is the most powerful in the Stihl chainsaw range and is quite heavy hence when resting on the Alaskan ladder used to make a reference cut it has a tendancy to rotate and lift requiring that a second operator is present on the opposite end to help ensure that the mill follows the ladder and creates a good flat cut.

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The saw is fitted with a 48" ripping chain & bar which produces a much finer sawdust and not the more regular chips produced when crosscutting using a chainsaw.

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After the 1st trial slab cut had been taken it was decided to level the tree trunk surface ready to take a 2nd slab cut by making a thin planking cut.

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The surface produced was checked for line and level and some further adjustments made with a chainsaw to smooth out small steps in the reference surface.

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The Alaskan sawmill assembly then proceeded to cut a 2nd slab about 6" thick

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When the levelling plank cut was made this unfortunately revealed a bark inclusion pocket and though at first disappointing it was quickly realised that the 2nd slab could be rip resawn to produce a good useable slab from which two cambered tie beams could be made.

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The resawn 2nd cut slab will fairly closly match the 1st cut slab.

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Some of the felled material was examined to determine what components could be made from same.

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This included cruck blades, braces & beams made from slab cut timber.

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Some of the material felled and cut up will have lower prospects of producing satisfactory quality components due to spiral grain, reaction wood, dead knots and included materials.

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The use of an Alaskan mill has demonstrated that even though this is quite a slow process it can and does produce useable scantlings from second rate material without the need to pay to transport a felled tree to a (local) sawmill. Where intermittant or non continuous production is likely then the Alaskan sawmill can provide a good low capital cost and effective way to convert timbers for use on sites especially where extraction of felled trees might proove difficult or damaging to the site.

Following on from the conversion of the cruck blades using an Alaskan sawmill the balance of timbers needed to make a cruck frame were converted by Phil Drew of Nuneham Courtney using a Forestor "Tom Sawyer" horizontal band mill.

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These timbers were then carried to the framing ground ready for the start of work.

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10 different timber species will be employed to make the frame including oak, ash, sweet chestnut, sycamore, cherry, grand fir, cypruss, etc. These have been laid out in easy access piles beside the framing ground.

Pile 1

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Pile 2

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Oak Crucks

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Brace Stock

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Cribbing: These blocks will be used to build layup piles for scribbing joint locations on timbers.
Some of the special terminolgy beginning to be employed in this thread will be explained and illustrated in more detail following the posting of more pictures.

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Log 1 has been resawn along its length using a chainsaw to create two similarly curved tie beams.

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The cruck framed barn will be fitted with windbraces made from Hawthorn and Whitebeam trees.

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After a week in the open quite a bit of movement is visible on the ash stock destined to form wall studs & rafters.

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The cruck building commenced on site on Monday 06th May 2013 and the first course will focus on cutting 2 cross frames including a cruck and box cross frame by Friday 10th May.

My next visit to Harcourt is due to be made on Friday 10th May following the kind invitation received form Barbara Czoch of The Carpenters Fellowship and Ben Jones - Curator of Harcourt Arboretum.

Ken Hume - Executive Trustee - Oxfordshire Woodland Group
trustees@oxfordshirewoodlandgroup.co.uk

Now check out Cruck Timber Frame Front Long Wall Layout, Cutting & Assembly

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