Construction of the Boat BW: April 2015

Construction of the Bottom and Continuous Deck

The BW's bottom will be a modified V with 8° deadrise at the transom and 12° deadrise at midship.

Scarphing Plywood

The construction starts with ripping 4-foot x 8-foot x 12mm and 6mm meranti into 30-inch x 8-foot panels. The ends of the panels are cut for scarf joining using the John Henry scarphing jig mounted on a Makita 4-3/8 power planer.

John Henry scarphing jig on a Makita 4-3/8 power planer

Scarph cuts in 3/4 select pine boards

Scarph cuts in ½ CDX plywood

Scarph cut in 6mm meranti

Gluing Plywood Panels Together

The 30-inch x 8-foot meranti plywood panels with scarph cuts are glued, using marine epoxy, into 30-inch x 24-foot panels.

Dry fit-up of panels before gluing

Pre-wetting of 12 mm faces with un-thickened epoxy

Mating of panels after applying thickened epoxy to faces

Clamping of panels for epoxy curing

Hanging one glued panel from the ceiling so it is out of the way.
Notice that the near panel is 6mm thick This is the front of the bottom.
The far panels are 12mm thick. They are the middle and rear of the bottom.
Another layer of 6mm will be laminated to this 6mm after the
bottom is bent into shape and glued.

Cut the Panels

After gluing the sheets together into 30-inch x 24-foot panels, they are cut to the dimensions in the boat plan.

Bottom panel plan

Flopping one panel on top of the other, in mirror image,
so that both panels can be cut at once

Use nails to mark the locations specified on the plan

Using a supple batten to fit a curve to the nails

Cutting the curves with a saber saw

'Glassing the Bottom Panels

I chose to apply fiberglass set in epoxy to the inside of the bottom panels, at this point rather than later when the inside will be cluttered with bulkheads.

Applying fiberglass using the dry method

Only the inside face is glassed at this point.
The outside face will be glassed later.

Stitching the Bottom Panels

Before stitching the bottom panels, I used a router to create ¼-inch radius on the inside edge of the keel. This will accommodate the two bottom panels mating at angles when stitched.

Routing a ¼-inch radius on the inside edge of the keel

Holes are drilled for the stitches while the two bottom panels lie on top of each other so that both panels are drilled in the same location.

16 gauge steel wires pre-coated with Johnson Paste wax
so epoxy won't stick to them and they can be removed
after the epoxy cures.

Completed stitching of the keel

Hanging the stitched bottom panels from the ceiling so
that they are out of the way. Again, notice that the near panel
is 6mm thick This is the front of the bottom. The far panels are
12mm thick. They are the middle and rear of the bottom.
Another layer of 6mm will be laminated to this 6mm after the
bottom is bent into shape and glued.

Preparing the Deck Pieces

While I have a nice big working surface, I will prepare the pieces of 12mm meranti plywood that will make up the continuous deck.

Since the deck will be just shy of 6 feet wide, I cut five 4x8 sheets of 12 mm into 4x6 sheets. Then I cut scarphs along the all of the 6-foot edges. The 5 pieces will be scarphed together when installed on the bottom. To provide moisture resistance and eliminate checking, I coated the underside of each 4x6 sheet with 4 ounce fiberglass set in epoxy.

Cutting scarphs in 4x6x12mm

Three sheets ready for coating

Vacuum after hand sanding is adequate surface preparation
for 4 oz. fiberglass as demonstrated in my Prep School post.

Lay out 4 oz fiberglass

Fiberglass saturated with epoxy. The weave was not filled
since these undersides of the deck will not be seen.

Deck pieces set aside for later installation

Unfolding the Bottom

Before I can lower the bottom from the ceiling and unfold it, I need to get rid of my work surface and bring in some saw horses.

Dismantling the work surface

Empty shop

Saw horses ready

After hanging from the ceiling for a month and a half, I can lower the bottom panels onto the saw horses and open them up. This is the first glance at the full size version.

Bottom panels on sawhorses

Similar view of scale model

Bottom panel unfolded

Similar view of scale model

Bottom panel unfolded

The coated meranti is quite beautiful. Too bad this will never be seen after the deck is installed

Filleting and Taping the Keel

The next steps are to get the panel pieces aligned, tighten the stitches, apply thickened epoxy fillet and biaxial fiberglass tape.

I pulled some string lines which revealed that the aft portion of the bottom, which should be straight, had a slight sag to it. So I installed a fourth saw horse to provide support and straighten the aft portion of the bottom.

String line showing sag at side of bottom

String line showing sag of keel

After straightening the bottom, I tightened the stitches then used a wood block and hammer to knock the arc out of the stitches.

I prefer to apply fillet and tape in one session with no curing so that I get a primary (chemical) bond between the fillet and tape. Plus, this negates the need for a perfect fillet. I use my hands to smooth the fillet and biaxial tape together, molding them into the desired shape.

5-inch biaxial tape over thickened epoxy fillet

Completed taping of the keel

I cut my biaxial tape about 18 inches too long and since the extra was already saturated with epoxy, rather than discard it, I installed it in the upper front of the keel.

Double layer of tape in forward 18 inches of keel.

After the keel fillet and tape have cured, it is time to pull the stitches. Diagonal cut pliers cut one side of each stitch then vise grip pliers clamp and pull the stitches. The stitches come out, but not easy. The vise grips need to pry the stitches out. I place a piece of scrap plywood between the vice grips and the hull so the prying does not dent the hull.

Strung Out

There will be one stringer in the BW. It will be a 2x that runs the length of the keel. I want the top of the stringer to follow the contour of the top edge of the bottom panels. This way, the continuous deck will contact the top edge of the port bottom panel, the top edge of the stringer and the top edge of the starboard bottom panel. So, first I have to plane the top edge of the bottom panels to provide a nice flat gluing surface.

Power planing the top edge of the bottom panel

Guide board to keep planer level
with the top edge of opposite side panel.

Planed edge of top panel

Then I put a glob of epoxy in the stem of the bottom to create a flat surface for the stringer. I added wood flour and wood chips to thicken the glob of epoxy. I rarely use wood chips as thickener. They weaken the epoxy and result in a non-homogenous fill with a nasty rough surface. However, in a non-structural, compressive filler application like this, I will use wood chips.

Bottom stem filler

I also had to install the sub-transom...the transom portion below the continuous deck. The sub-transom is a 2x board, glued in place. Then a thickened epoxy fillet is laid. The fillet is covered with biaxial fiberglass tape set in epoxy.

Subtransom

Now I have reference levels all around that I can use to determine the dimensions of the stringer. I pulled a string line down the center of the bottom, from the top of the sub transom to the top of the bottom stem. I marked the string with stations every 12 inches. At each station I measured the height to the top of the planed top edge of the bottom panel and the inside of the keel.

String line installed and marked at 12-inch stations

Measuring top panel and keel height from string

I used the dimensions and AutoCad to draw the stringer, determine what size 2x's it will take and develop a drawing with stations and offets for laying out the stringer.

Stringer lay out in AutoCad

2x8s, 2x10 and 2x6 for the stringer

Stations and offsets

I cut dados in the 2x's and glued them together with thickened epoxy.

Dados cut in 2x

2x's glued and clamped

After the epoxy cured I layed out the stations and offsets, marked the curves with a supple batten and cut the stringer. After cutting, I sanded the faces. I also routed the bottom edges quarter round so the stringer will set in the keel where the inside keel surface is not flat.

Marking stations and offest

Draw curves with a supple batten as a guide

Cutting

Sanding and routing the bottom edges.
It gets dark early in mid-December at
latitude N60°

Can't wait to see if it fits!

Looking aft towards the sub-transom

View of the stem.

It mates with the keel and stem within 1/8 inch.

I cut the top edge of the stringer a little low so that it would be lower than the top edge of the bottom panels. This is because, for gluing, I can clamp the continuous deck down to the stringer using screws. But I cannot clamp the continuous deck down to the bottom panels using screws because the bottom panels are to thin to hold a screw with much force. A quick check with the straight edge shows that the top edge of the stringer is about 1/8 inch below the top edge of the bottom panels.

The 2x12 used to build the stringer was a bit checked and split on one side so I decided to put a heavier-than-usual coat of fiberglass set in epoxy on both sides.

Stringer coated with 4 oz. and 10 oz. fiberglass on each side.

I temporarily installed the stringer by centering it then running screws up through the keel.

Clamp boards to center stringer

With the stringer temporarily in place, I measured and cut bulkheads. All bulkheads are 2x fir with fiberglass/epoxy coating.

Fiberglass coating of bulkheads

I installed temporary guide boards on the stringer to ensure that the bulkheads were perpindicular to the top of the stringer at each bulkhead location. Then I glued the bulkheads in place with epoxy, thickened with silica powder, glass fibers and wood flour. During installation, the excess epoxy that oozed out from beneath the bulkheads was smoothed into a fillet and 4-inch fiberglass tape covered the fillet.

The bulkheads were held in place by temporary screws installed up through the bottom panel. After the epoxy cured, I removed the screws.

Installation of bulkhead with excess epoxy oozing out

Bulkhead fillet and tape

After the bulkheads installation epoxy cured, I removed the temporary guide boards from the stringer. I installed the stringer permanently using the bulkheads as a guide. The stringer was held in place by temporary screws installed up through the keel. After the epoxy cured, I removed the screws. I glued the stringer in place with epoxy, thickened with silica powder, glass fibers and wood flour. During installation, the excess epoxy that oozed out from beneath the stringer was smoothed into a fillet and 4-inch fiberglass tape covered the fillet.

Stringer installed, filleted and taped

The bulkheads were then secured to the stringer with fillets and biaxial tape.

Bulkhead/stringer fillets and biaxial tape

Sub Strung Out

Since the continuous deck will be 12mm meranti plywood, the 30-inch± span between the stringer and the edge of the bottom panels seems a bit long. I installed 1x substringers about midspan so the deck only spans about 16 inches.

However, the substringers at the transom were 2x's placed about 12-inches from the boat centerline to coincide with the location of the future transom knees and outboard motors. Also, the foremost pair of substringers were installed about 10-inches from the boat centerline due to the limited bottom width.

All substringers were coated with fiberglass set in epoxy. Drains or vent spaces were provided where each substringer connects to each bulkhead so that the substringers did not create additional bulkhead chambers. Each substringer was glued to the bottom with epoxy, thickened with silica powder, glass fibers and wood flour. During installation, the excess epoxy that oozed out from beneath the stringer was smoothed into a fillet.

Fiberglass coating of 1x substringers

2x substringers at the transom. Note the space between the
transom and substringers.

Dry fitting of 1x substringers

The aft six substringers are in the portion of the bottom where the bottom is straight and the cut is simple. However, the forward four substringers are in the portion of the bottom where the bottom is curved and is a complex cut. For these forward stringers, I made templates from cardboard.

Making a cardboard template for the first pair of the
foward four substringers

First pair of the foward four substringers installed and filleted

Drain hole (AKA limber) at the substringer

Second pair of the foward four substringers installed and filleted

Stinger, bulkheads and substringers complete

Before flipping the bottom, I took some measurements and drafted an as-built drawing of the bottom, stringer, bulkheads and substringers. I will need these dimensions for future construction above the continuous deck.

As-built drawing of the bottom, stringer, bulkheads and substringers.

Flip Out

It is time to flip the bottom and do some work on the outside of the bottom. I used a series of overhead pulley and ropes to flip the bottom. The weight was pushing the limits for the ropes and pulleys so I made sure I was out of harms way at all times. But, then, as usual, my dog walked into the shop and laid right where the boat would land if it fell. After chasing the dog away I was able to finish flipping the bottom.

Hook up ropes and pulleys

Lift to get the saw horses out of the way

Set one edge on the floor

Flip over onto saw horses

Q.E.D.

Laminating in Shape

It is time to laminate the second layer of 6mm meranti plywood over the first layer. The first layer is already part of the bottom and is bent to its final shape as shown above.

Laminating in shape is not common but not a rarity either. It is used occasionally. I used it as directed in the CLC plans for the Chesapeakes and as directed in the V-20 plans for LadyC over 20 years ago.

CLC Chesapeake deck beam layers

CLC Chesapeake deck beam layers in jig

Completed CLC Chesapeake deck beam

CLC Chesapeake coaming layers

CLC Chesapeake coaming layers on deck

Laminating final layer
in V entry of V-20 LadyC

For the BW, the full 32x96-inch piece of 6mm is dry fit on the hull, scribed, removed, cut 1-inch proud, pre-coated with un-thickened epoxy and laminated in-place with thickened epoxy.

Dry fitting of port side 32x96 6mm

Pre-coating of cut 6mm

Pre-coating of 6mm bottom

Pre-coated 6mm bottom

Laminating second layer of 6mm to first layer

Second layer left an inch proud

After sanding the port side flush, the starboard
side is installed. Note the screw holes filled
on the port side panel.

Glassing the Bottom

After sanding out a few rough spots and rounding the sharp vee in the keel, the entire bottom is sheathed with 10 ounce fiberglass and the keel receives a layer of 24 ounce biaxial fiberglass tape.

But Wait! If I glass over the keel, I will lose reference to the centerline of the boat and future placement of the lifting strakes will require a guesstimate of the centerline location. So, before glassing, I measured and struck chalk lines to mark the future locations of the lifting strakes.

Chalk lines of future lifting strakes centerlines

Let the glassing begin!

Pre-coat before applying 10 oz

Apply 10 oz with overlap in forward part of
keel for a total of 20 oz.

10 oz fiberglass over the entire bottom, including spanning
the rounded vee of the keel. If you look close enough, you
can see the chalk lines for the lifting strakes.

Installing 24 oz biaxial fiberglass tape to the keel

24 oz biaxial fiberglass tape on the keel

So now the keel has both 10 ounce woven and 24 ounce biaxial fiberglass spanning the joint. I guess you could call that 34 ounce fiberglass. In the area of the stem (the front portion of the keel) there is an extra layer of 10 ounce woven fiberglass spanning the joint since I lapped the keel twice with 10 ounce. I'll call that 44 ounce fiberglass.

When wetting out for the biaxial fiberglass tape, I filled the weave in the underlying 10 ounce beyond the limits of the biaxial tape so that the surface would be smooth for future fairing. After the biaxial fiberglass epoxy cured, I sanded the outer edges smooth. I faired the edge of the biaxial, which is about 3/16 inches thick, with epoxy thickened with silica powder and microballoons. When fairing, my putty knife had two smooth surfaces to ride on - the filled weave of the 10 ounce and the sanded edge of the biaxial - resulting in a fairing requiring very little sanding.

Faired biaxial tape

Need a Lift?

Installing the lifting strakes turned out to be more work than I expected. Boat building is my hobby and I want to work only an hour or two each day. Any longer and it becomes a toil instead of a hobby. Installing the lifting strakes required

Mark the temporary clamping screw hole locations on the bottom, every 6 to 9 inches along the strake centerline mark, avoiding the bulkheads.
Drill the holes from the top.
Install guides to set the lifting strake in the correct location and keep it straight.
Dry fit the lifting strake and clamp it in place.
From underneath, re-drill the previously drilled holes so that they continue into the lifting strake without penetrating the full depth of the strake.
Remove the strake.
From underneath, install temporary clamping screws through the bottom plywood panel. Overturn the screws so that they strip the thread in the plywood. That way they will suck the strake down tight to the plywood without the threads hanging up on the plywood. Leave the screws sticking up out of the bottom panel as high as possible
Vacuum the mating surfaces.
Pre-wet the mating surfaces with unthickened epoxy.
Mix a batch of epoxy thickened with silica powder, glass microfibers and wood flower. The thickened epoxy should be just a bit thinner than peanut butter but it won't taste as good.
Layout a healthy bead of thickened epoxy on the bottom panel (i.e. butter the bottom panel) along the strake centerline mark. This bead should use up the entire batch of thickened epoxy and extend about 4 to 6 feet along the strake centerline mark.
Position the strake in the guides so that the holes in the strake line up with the temporary clamping screws.
Screw-clamp about 3 feet of strake, squeezing out lots of excess epoxy.
Blade the excess squeezed-out epoxy off and use it to butter another 3 or 4 feet of bottom panel.
Screw-clamp another 3 or so feet of strake, again squeezing out lots of excess epoxy.
Blade the excess squeezed-out epoxy off and use it to butter another 3 or 4 feet of bottom panel, so on and so forth until the strake is completely installed.
Use the left over thickened epoxy to create a fillet at the edge of the strake for a nice smooth transition to the bottom panel.
After at least a day, remove the clamping screws.
Do it again three more times.

I found that installing one strake took about 3 hours and was a bit more work than this hobbiest is interested in undertaking. Being lazy, I stopped after step 7 and called it a day. The next day I continued with step 8. This resulted in a pair of pleasant 1½-hour sessions rather than a single grueling 3 hour session for each strake. Hey! It's a hobby, not a job!

Guides, clamps and lifting strake dry fit for drilling

Strake removed. Guides and clamping screws
in place.

Completed, faired strake

All four lifting strakes installed. Stern view.

All four lifting strakes installed. Bow view.

It is time to fill the weave in the 10-ounce fiberglass. A consistent one-color layer will show flaws better than the current multi-colored layer so I filled the weave with pigmented epoxy. Since the bottom of the boat will be painted, the pigmented epoxy will not be seen. White pigment was available locally. Any flaws could be filled with fairing compound. I tried not to obsess over perfecting the bottom since when the BW is not on the trailer, half it's time is spent dry on a rocky beach.

Bottom partially coated with white pigmented
epoxy.

The pigment does not thicken the epoxy and the epoxy applied to the steep portions of the bottom near the bow would run like Forrest Gump without thickening. So I thickened the epoxy with silica powder to fill the weave in the steep portion of the bottom near the bow.

Bow area weave filled with silica-thickened
epoxy.

Don't Flip Out on Me Again!!!

It is time to flip the boat again. I think this build will require 4 flips and this is the second flip. Before flipping, I built a wheeled cradle. The hull will sit on the cradle so I can wheel the hull outside for future cutting, sanding and flipping.

Wheeled cradle on boat bottom

Flipped and happy on the cradle

The second layer of 6mm meranti laminated in the bow area was installed about an inch proud. It is time to cut and sand the excess.

Sanding the excess 6mm

The Continuous Deck

Then there was a knock at the door. There has never been a knock at the shop door before!

Oh, it's Peter. Met him at an on-line forum. He heard about my continuous deck and stopped by to see the support underneath before the supports are covered by the deck.

Which is the next step. The continuous deck is five sheets of 12mm meranti (underside previously coated with 4oz, fiberglass) joined by scarph joints and glued to the supports. The bulkheads were positioned so that they would be beneath the deck's scarph joints. This way the bulkheads provide anchors for the screws that will clamp the scarph joints.

Here is a pictorial...

First sheet

First sheet at the transom

Second sheet

Third sheet being lowered

Third sheet in-place

Fifth sheet

The last little segment of deck is made up of two triangles of 12mm meranti

Pre-coating underside of triangles with 4oz.

Final deck pieces at the bow

TaDa!!!

It looks kinda boxey. After the last scarph joint cures, I'll cut the deck to its final dimensions.

Layout the plan stations and offsets and connect the dots with a supple batten.

The inspector arrived to check on my work

Free-hand cutting of the curves

Cutting the straights with a guide

Ahhh! It looks like a boat again

After removing the temporary clamping screws,
I plugged the holes with thickened epoxy and
faired the scarph joints

Let the plugs and fairing cure, sand them flush and pre-coat
with un-thickened epoxy prior to applying 10oz. fiberglass

After the 10oz. layup cured, fill the weave

If not for the plugs and shitty scarphs, it is
not a bad looking deck.

Too bad it will be covered with a non-slip surface and fish guts

Since the scarphs in the deck would be covered, I was not meticulous about making a pretty joint. But, I learned a lesson. The 12mm meranti sheets were stored outside for weeks. I cut the scarphs then brought the sheets into the shop to warm up and dry out. After several weeks in the shop, I glued the deck sheets to the bottom, gluing the scarph joints at that time. While warming and drying in the shop, the thin feathered edges of the scarph cuts curled, splintered and some pieces broke off. A pretty joint could not be obtained without re-cutting the scarphs. No need for re-cutting since the scarphs will not be seen after applying the non-slip surface, spilling several beers and gutting halibut.

Scarph joint in deck

Lesson learned: glue scarph joints immediately after cutting the scarphs. Luckily I did this with the side panels where the scarph joints will be seen.

Taping the Chine

After two months of attaching the side panels to the continuous deck and working on the hull, we flipped the boat upside down so I could finish the bottom.

Fillet and tape the chine with 24oz biaxial fiberglass tape

Lightly sand the tape in the areas where the
fairing blade will travel. Otherwise the fairing
blade follows the rough contour of the
tape and results in a lousy faring.

Fair the edges of the tape and fill the weave with
thickened epoxy

Finishing the Bottom

After the bottom and chines are faired, the bottom can be finished with top coat.

First of two coats of graphite-thickened epoxy

Completed graphite-thickened epoxy (two coats).

A fly in the ointment! In my UV the Captain blog I concluded that I will omit UV protection from the BW. However, I have been approach by a friend who is very interested in buying the completed BW. I am willing to omit UV protection from my own boat but I am not willing to omit UV protection from somebody else's boat. So, with the possibility that the boat will be sold upon completion I have changed my mind and will apply UV protection.

Since the BW is a day-sailer (lives on a trailer, not in a slip in the water) the bottom paint does not need to be anti-fouling. For bottom paint, I have decided to use Rust-Oleum Topside paint.

"For bottom paint...use Rust-Oleum Topside paint." Is that an oxymoron?