Veneering a Transom

Fall 2022

By Bill Bauer

I’ve been restoring an MFG 15. The transom was made up of one very thin fiberglass hull transom sandwiched between two ¾” mahogany layers and bolted together. I chose to reinforce the fiberglass transom with 12 oz. fiberglass. I also laminated the backside of each mahogany layer piece with 6 oz. fiberglass, and the front (exposed) side with 4 oz. fiberglass.

After doing all this work, I decided the original transom wood was too marred so I added a layer of mahogany veneer. Since I don’t have a veneer-clamping table, I simply used another transom as the clamping table.

The original transom, glassed with 4 oz. and three coats of WEST SYSTEM 105 Resin®/207 Special Clear Hardener®.

The 105/207 coating was sanded with 40-grit in preparation of applying the veneer.

The sanded transom was then brushed clean and wiped down with alcohol and a paper towel.

The transom is roughly 9 sq. ft. To adhere the veneer, I chose 105/207 in case there was bleed-through onto the veneer. I mixed two batches of five pump strokes each, and five teaspoons of 403 Microfibers Adhesive Filler. This made a honey-like consistency. I spread this mixture on with a notched trowel.

The veneering stack: the transom to be veneered, epoxy thickened with 403 Microfibers, veneer, plastic sheet, cardboard, plastic sheet, and the other transom. The cardboard helped to distribute the pressure.

The veneer I used was 2-ply flat cut mahogany that’s a wood-on-wood construction. It’s backed with a non-mahogany wood rather than paper and is available from veneersupplies.com.

A heavy center weight and clamps around the edges completed the setup.

I let the transom stay clamped for several days and then lightly sanded the veneer with 120-grit.

The 4 oz. fiberglass was wet out with 105/207 using a squeegee to apply only enough epoxy to hold the cloth in place. Too much epoxy will cause the fiberglass to float on the epoxy, resulting in a wavy surface.

The 9 sq.ft. of 4 oz. fiberglass cloth took about eight pumps of 105/207 to apply. I used two batches of 4 pump strokes each.

After about four hours at room temperature, the epoxy had cured enough to support the second coat, and four hours after that, the third coat. Five pump strokes of epoxy were enough for each of the additional coats. I applied these with a foam roller. These coats were enough to fill the weave in the fiberglass.

After allowing the epoxy to cure for three days, I applied seven coats of 1015 Captains Varnish with a foam brush to both halves of the transom.

The purists will promote bristle brushes to apply varnish; I like Jen Poly-Brush® foam paint brushes because they do an adequate job and I don’t like to clean brushes. Three or four coats should be enough, but I apply seven coats to new wood to provide a good base and a deep finish.
The first two coats were lightly sanded with 120-grit. The next three coats were sanded with 220-grit, and the last two coats were rubbed with Scotch-Brite™ General Purpose Hand Pads. The transom was dusted off and wiped with a tack rag before each coat of varnish.

I applied the seventh coat using the “wiped on” method by soaking a lint-free, clean rag with a mixture of 50/50 varnish/mineral spirits and wiped it on the surface. This applied a thin coat that was free of runs and brush strokes.

It is important to lightly sand and apply a new coat of varnish every year to seal the varnish. Any small crack in year-old varnish will let moisture in, causing the underlying wood to darken and the varnish to lift and flake off.

Bill Bauer is a boat builder who helps maintain the local schooners Appledore IV and Appledore V. Visit his website at wrbauer.net