Transom Bevel

Installment XV in the chronicles of a Mako classic restoration
We returned the next morning eager to see how this old boat accepted her new core. The Penske core sandwich buttered with epoxy cured nicely, the clamps securely held everything in position. We removed the C-clamps and exterior 2x4 board handily. The bond between the new core and the old outside laminate skin was rock solid. Unavoidably, some epoxy ran through the bolt holes of our 2x4 clamping setup. Excess epoxy also drizzled down from the top. Thus our temporary clamp was also accidentally bonded rock solid to the inside in a few spots. It needed persuasion from the multimaster with an ecut blade to cut through the bond and free it up. We resisted the urge to tear the board free as the penske material is only a dense foam. The E-cut made a surgeon like incision which solved this problem perfectly.


This evening involved prep work in advance of the next stage, laying-up cloth inside the transom. We will lay 1708 biaxial cloth over top to the inside of the transom. To assure optimal bonding between old and new, a taper of 5:1 surface area to laminate thickness is recommended. We used a rotex orbital sander with coarse grit discs to grind the bonding area. [Beveled area pictured above, the tan area along the top of transom.] We rounded the top edges slightly and will add some thickened epoxy. Our goal is to fair any sharp edges to a smooth transition- this makes better bonding surface for the cloth.

Traces of epoxy oozed over night leaving a slight hollowing under the core bottom edge. Some epoxy thickened with high density 404 filler and cabosil remedied the voids under the core edge. With this same mix, we laid a fillet joint bead along the entire transom to hull edge. The back of a spoon or a gloved fingertip is all that's needed to create the concave fillet. The fillet shape forms a nice easy curve for cloth to adhere, which is our next step.

Gravity brought low some epoxy from up on high. Epoxy run is an inherent problem to both bonding and hand-layup of vertical surfaces. We filled the voids along the top corners with the same blend of epoxy thickened with high density filler. The remaining thickened epoxy we spread across the top transom edge to complete a nice smooth transition- like icing on a cake.



The complex form of the top corners will prove challenging to rebuild. We have ground out taper here and still have a bit more grinding to get the correct ratio for a proper bond. Our first layup in this area will focus purely on encapsulating the transom core. We will address the gap in the gunnel in a later step. Bridging that gap will require placing some temporary mold to lay wet-out cloth over.



The final consideration before the glass layup is assuring the surface is clean from contaminants. We will cover this in the next post.