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Milbs Mobile Projects

Stay current on all Milbs Mobile Marine field work.

Project Detail: A Field Blog



Project Scope: This blog will cover the latest work being performed offsite.

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13) CD 27 - Tabbing Backstay Knees & Mast Wires Thru-hull

February 19, 2024

I began the day by water-washing the amine blush from the backstay knees, where previously I have glued them into position with epoxy thickened with high-strength 404 filler. Using a Scotch Brite pad and water, I scrubbed the surfaces to remove the amine blush - a waxy film - that forms over cured epoxy. The amine blush is a contaminate to additional epoxy work, so must be removed. Utilizing peel ply (as can be seen in the second picture of the backstay knees) eliminates the need to water-wash since the amine blush soaks through and forms on the peel ply surface, and after curing is easy torn from the surface of the work.
With the surfaces clean, I wiped them down with acetone and then prepared some epoxy to wet out the surfaces to be tabbed. I also took the time to thicken some epoxy to ease the transitions from knee to hull surfaces. I collected eight lengths of 1708 biaxial cloth, wet them out, and applied them as tabbing. I finished the area by applying peel ply to reduce the need for sanding.
The backing plates for the backstay and sidestays / shrouds were essentially now complete - only drilling them out and tapping them for new machine screws were left to do. I then turned my attention to the installation of a thru-hull fitting at the mast to serve as a way to get mast wires into the boat, and to keep water out. Borrowing a technique from a friend in Maine, I will be installing a 1.25" diameter rail fitting and a 1.25" diameter thru-hull, connected by a short piece of hose, clamped to seal out water ingress. Today, I got started on the thru-hull portion of the installation. I selected an area near the mast step for the installation, tapped of the deck and transferred the locking nut diameter onto the tape. Finishing center, I drilled a small pilot hole through the deck.
The installation process would be one of over-sizing the hole, filling with solid glass, and then drilling out the smaller diameter for the thru-hull itself so as to protect the surrounding balsa core. the process would isolate the balsa core from any water that may make its way into the boat.
Down below, I grabbed a hole saw larger than the diameter of the thru-hull and drilled through the bottom skin and balsa core, careful not to penetrate the top skin. I removed the bottom skin and balsa, and then generally cleaned up the area by removing chunks of balsa still adhered to the underside of the top skin. A final cleaning with acetone enabled me to begin to fill the freshly opened space. I used the same hole saw and removed a puck of solid fiberglass from a backing plate I had lying around the shop. I wet out the opening with epoxy, as well as the solid fiberglass puck, then thickened some epoxy to use as glue to set the puck into place. I finished the opening by pressing in thickened epoxy to match the surface of the underside of the adjacent bottom skin, and then applied a layer of peel ply. Drilling a hole for the thru-hull would come next.

Total Hrs: 4

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