Further progress – Stem Knee, Chain Plate Reinforcements, Internal Skin Laminates

Mast-step Bearer

I am now busy with the Inner Skin which is laid up in sections between each bulkhead. My original plan was to  roll the boat to 45 degrees either side with the intention of making the internal laminating easier. After a trial doing one section with the boat inverted (bottom up), I found laminating overhead difficult, but almost manageable to my stubborn character, so I decided to continue in this way as there are some advantages. For one thing I stand on level ground, further, the rubbish all falls out of the boat, and as the boat is set up level, fitting up the internal panels is easier.

 

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The internal structure between Bulkheads 2 and 5 provides support to the significant rig loads, requiring much thought before the final installation and the taping of Bulkheads 3 and 4. Both bulkheads needed to be installed before the internal skin in this area could be started. This could only happen after I had sorted out the Mast-step Bearer.

 

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The original Eric structure is massive even by 1924 standards. The origins to the Norwegian working vessels from which the Colin Archer and subsequent Atkin designs where based are very evident.  Note the keel timber of 250 x 300mm and massive Stem and Stem knee!

The original Atkin design Stem Knee provides support to the highly loaded Mast-step but without much additional support of the metal (lead or iron) Ballast Keel, which is normally the case with Sloop or Cutter rigs. The Eric ketch rig has the mast base much further forward resulting in the mast-step being located right at the forward extreme of the Ballast Keel.

 

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My Eric CSP design is very much a hybrid of timber strip plank and composite sandwich construction. Elements of both construction methods sometimes providing a structural duplication, both belt and braces!

The composite hull is essentially a monocoque structure and does not rely on the massive timbers of the original traditional carvel planked and bolted together structure.

A mortised join provides a strong connection between the laminated timber Stem and the keel timber. This is further supported by the planking bonded to the structural members and the external and internal skins.

I have extended the bearer to incorporate the Stem-knee, all in laminated Tasmanian Oak.

 

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The previous profile view drawing can be a bit misleading. Looking down between Bulkheads 2 and 4 the Stem is fairly narrow with the keel plank increasing in width as it runs aft towards Bulkhead 4.

The photograph above shows a narrow section of the bilge has been skinned and Bulkhead 3 has not yet been fitted, to allow access to install the Mast-step Bearer. Due to a high likelihood of fresh rain water ingress from the mast, I have sealed all exposed timber in this area with epoxy resin and at least one layer of woven fabric.

 

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After a number of bending failures I eventually determined the correct steaming duration, and using a metal tension strap to prevent splinting on the outside of the bend, I formed the planks and then glued these together.

Tasmanian Oak (mountain ash) is well suited to the application as it is relatively hard with good cross grain compression strength and is suited to steam bending.

 

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Here the Mast-step Bearer is dry fitted, for the umpteenth time,  after incremental trimming to size and adjustment for the small amount of spring back after steam bending.

 

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Finally the bearer is bonded in place and taped to the Hull; the remaining bulkheads installed, and the internal skin completed, section by section.

 

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A view at Bulkhead 5, the forward end of the Cabin, and through the Heads compartment into the Forward Cabin. Bulkhead 3 has limber holes, although most bulkheads form sealed compartments and will have drain-plugs, not limber holes.

Chain-plates

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The soft western red cedar strip planking has been replaced with solid GRP laminate at the chain-plate locations to provide a hard bearing surface for the chain-plate bolts. The outer line at each location showing the extent of the taper.

 

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Prior to installation of the bulkheads an additional reinforcement patch was applied then  the planking was cut, tapered and a solid 14mm thick laminate at the chain-plate mounting locations was laid-up.

 

Internal Skin

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After a careful 40G orbital sanding, a seal coat was applied on a cooling temperature in the late afternoon to the section adjacent to the bulkhead.

 

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First step was the keel patch. Eventually my juggling wins and more of the patch stays put than falls off.  Then I can relax a bit and and consolidate the laminate.

 

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The first ply is the interface 200gsm plain weave cloth applied dry onto a resin coat and wet out in-situ.

 

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The double biased stitched fabric forming the bulk of the inner skin laminate is wet out on the bench, and then rolled on.

 

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Finally a further woven ply is applied and followed up with peel ply.

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And the first section of the cabin is completed, with approximately 50% of the internal skin now completed.

 


 

 

 

 

 

2 thoughts on “Further progress – Stem Knee, Chain Plate Reinforcements, Internal Skin Laminates”

  1. Loving your work, keep sending pics etc. I’ve been restoring my fibreglass (hull only) Ingrid Class ketch (William Atkin design of 1934), built Seattle 1970, for 20 years now (no rush) and you spur me on,
    Cheers
    Rob Porter 😃💪⛵️

    Like

    1. Hi Rob

      I just found your email whilst doing a tidy up of mu inbox. Sorry for the very late reply and thank you for your comments. I would be interested to hear how your restoration is coming along.

      Regards

      Mike

      Like

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