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Decking – the icing on the cake

On March 27, 2015, in Designer Articles, by Glen L. Witt

Icing isn’t necessary on a cake, but it sure makes it look and taste even better. An attractive wooden deck on a boat is similar. It doesn’t change the basic boat, but does enhance the appearance; often many times over.

Now let’s understand that we have nothing against the fisherman, hunter, or workboat operator who prefers a practical usable deck that can be tromped on at will. However, the following is for the guy or gal who does like that beautiful hand crafted natural, bright finish deck.

Classic Mahogany Runabout

Biscayne 18 built by Ron Chatfield


The classic all mahogany runabouts of yesteryear probably pioneered the natural finished deck so admired today. Those decks were mostly of solid wood backed with battens at the seams.

Deck planks were seldom less than 3/8” and about 3” wide, although it was commonplace to use a 6” wide plank and cut a groove or grooves to simulate narrower planks (See Fig. 1). Decent plywood was unavailable at the time.


Fig. 1


Solid mahogany, or other attractive wood, is still preferable. It gives the depth and a general appearance that plywood veneers cannot provide. Solid wood edges can be rounded and sanded while plywood veneers are very thin and minimal sanding can be done.

However, a plywood deck is easier to apply than a solid wood type. The typical deck is a compound surface and sheet plywood possibly will need to be longitudinally pieced over battens or butt blocks to conform to the contour.

 An attractive deck style uses a perimeter, solid wood member called a “finishing” or “covering” board, frequently a darker color than the main deck. Often this solid wood member continues along the deck centerline and is then called a “king plank”.

The simulated grooved planks are solid stock or plywood. On any but the smaller boats, a plywood underlayment is desirable with the planks or plywood epoxied to it. With proper gluing practice, fastenings are not required although preferably used on the finishing board or king planks with the screw heads bunged.

Finishing boards and king planks have been traditionally solid wood. Finishing boards are preferably cut from stock as wide as possible to eliminate joints. They may be butted together and backed with a butt block, however, the junction shown in Fig. 2 is more attractive.

Fig. 2

Fig. 2

This joint can be hand cut and fitted however, a router used with hand made templates is an option for the perfectionist who demands the best. Finishing boards often extend across the transom as capping exposed edges of an inner plywood deck is a necessity.

A finishing board made from strips, usually about 3/4” wide, creates an attractive alternative. Strips can be glued and nailed to one another progressively and can be alternating wood colors, such as mahogany and spruce or other light colored wood. The entire deck can be made in this fashion ending in a herringbone pattern at the centerline as we did on our Lo Voltage design prototype.


Strip planked finishing board and deck of 5/8" thick x 3/4" (1" stock) joined on the centerline in a herringbone fashion

Strip planked finishing board and deck of 5/8″ thick x 3/4″ (1″ stock) joined on the centerline in a herringbone fashion

The grooves in planks and between them and the finishing board or king plank were usually about 1/8” wide or more and at least that depth. The originals were never fiberglass covered; the covering was unknown. Our personal opinion is that the mahogany deck be varnished or similar clear finish, NOT fiberglass covered. The classic boats used a filler stain to even out the mahogany color with the seams filled with a flexible putty-like product; today, epoxy with microspheres is often used to fill the seams. 

Seldom seen today, but popular for awhile on the classic runabout was the bleached mahogany deck (blond mahogany) or portions of it. A two- part or A/B bleach, usually sodium hydroxide and strong hydrogen peroxide is used to remove the natural red from the wood. Such a product is available in larger paint stores; several brand names are NU-TONE, DALYS, WOOD  KOTE and KWICK KLEEN.


glen-l boat plans

L Capitan test model. Deck was mahogany bleached with acid and a yellow tinted filler rubbed on. The late Don Ruffa is in the boat.

Application methods can vary, but basically after the bleach has been applied and is dry, sand lightly to knock down the grain and then apply a dark mustard colored pigment stain (like nutmeg or fruitwood) and wipe off the excess. This produces a light yellow-brown color so popular in the forties and early fifties. When used in combination with a rich dark stained mahogany finishing board, a very attractive deck is created. 

Glen-L boat plans for classic wooden boat

Barrelback built by Richard Salvatore with dark seams

The method of obtaining the mahogany bright finish deck used on these classic runabouts is still in use. After the deck is finished and sanded, no seam filler, the entire area is wet down with water. This causes the grain to raise; in fact mahogany can be made to swell slightly to eliminate minor dings. After drying and sanding, filler stain is applied. This evens out the wood color and fills the mahogany wood grain.

This is followed with numerous coats, usually ten or more, of varnish, sanded between coats. The seam filler was a flexible mastic applied after several coats of varnish had been applied. When epoxy is used to fill the seams, the deck is coated with a couple of coats of epoxy, the seams filled with microsphere thickened epoxy to a putty-like consistency, and then followed with a varnish or other clear UV protecting finish.

classic boat plans

Riviera built by Thomas Stock–he has taped off his deck planks in prep for the seam filler

Thomas Stock’s finished deck on the Riviera

The seam filler is radiused slightly below the deck surface; a Popsicle stick or a ball bearing welded to a short handle work well.

Seam fillers, epoxy or mastic, do have a tendency to yellow. Some prefer yellow seams and may use coloring to achieve it; others prefer white or dark colors. Some have used pin striping tape, available from automotive paint stores over a plywood deck to simulate grooves.

Glen-L boat plans

Kevin Brown used automotive striping tape to simulate a planked deck on this Squirt that he modified for jet power–“Fastidiots”

classic mahogany runabout

Bruce Dow’s Monaco with yellow stripes between deck planks. Many of our Canadian builders prefer this look.


Another interesting approach is to use very thin pieces of a light (or dark if you prefer) wood in the seams between planks. Check the “Deck Seams” link which is a PDF of comments on various methods used by builders of Glen-L designs taken from our Boatbuilder Forum.

Squirt runabout

Squirt built by Graham Knight–he used lighter wood strips between the darker mahogany for his deck.

So consider crowning your masterpiece with a bright finished natural wood deck. And, when used on a white, bright yellow, or natural mahogany topside hull it will truly put the icing on the cake.

classic mahogany runabout

Monaco built by Kevin Kluck


Your Thoughts?

One Response to Decking – the icing on the cake


    Nice summary.

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