DIY Retro Twin Fin, Part 3: Rails & Tail

Special care should be taken with the nose and tail. For the most part these sections are much thinner and will break with a heavy hand. I took about a ¼-inch of foam off the thickness at the middle of the board but more than an inch at the nose, leaving it only a ¼ inch thick at the very tip, so sanding took some time. I planed the stringer down first, taking care not to snap off the end, then sanded down the foam using uniform perpendicular strokes from rail to rail, leaving a nice smooth, lightly curved surface.


When it came to the tail, I cut a deep 6-inch swallow tail. I planed the tail down to about an inch thick, tapering down to a blunt point at the end, and hand-shaped the rails on the inside of the tail. I kept the rails pretty routine, rounding the top but leaving a pretty hard edge on the bottom. I carried the overall curvature of the tail from rail to rail, almost giving it a domed shape.

Working the rails.

Once I was at a comfortable spot on shaping, leaving still a bit to go, I cut the rails with the Fred Tool. The Fred Tool is essentially a block of wood with a 30-degree blade off one side. I determined how deep I wanted the rails to come—roughly an inch and a half on the top. Marking small pencil marks along the board every six-inches or so. I then took the Fred and ran it along the board, cutting to those points. I then flipped the board and marked about an inch in from the edge, tapering off about two-feet shy of the tail. I then ran the Fred, cutting to the pencil marks. Once the rails were cut, leaving a triangular/trapezoidal shape, I began rounding the rails by hand with some 120-grit sandpaper, tri-folded. Walking nose to tail with long continuous strokes, I gently shaped the rails, following the contour of the board, making sure to only round the top of the rail of the last two-feet, hardening and flattening the bottom.


Even with a light touch, there will be some wonky spots along the rails. To correct, a long block sander with flex is key. This will span the dips and smooth everything flush while following the general curve of the rail. The rails are one of the most difficult parts to shape, especially for first timers. A simple tip is to count out the strokes when sanding—sand ten times, flip, sand ten-times. It is not perfect, but it will help keep the rails symmetrical. And if one were so inclined, a simple sharpie line the length of the rail—dead in the middle—if done smoothly, can be quite helpful, showing the dips and imperfections. Smooth out and lightly sand away the line.

Finding imperfections under light.

When the board looks good to glass, it probably isn't. A good way to find the imperfections and hollow spots is place the board over some lights shining upward. Bring the board inside on a rack, then set some fluorescent lights below, just a few inches below the board, along the rails. Step back and get low, equal with the board and it is pretty easy to see all the imperfections. Mark them with pencil, flip and repeat. Sand and shape, throw back on the rack and flip the lights. Repeat as needed.


For some hollows, simply running a hand along the board is all it takes to find the spots. It helps to feel the board without looking, using just the sense of touch.

Sanding the channel.

Also, a second or third pair of eyes would not hurt either. It takes some time to notice the imperfections put into the board by your own hand, and it can be a bit of an ego blow when someone points something out immediately, but in the long run it is worth the minor embarrassment. So don't get defensive!


As I mentioned in an earlier post, I added a groove underneath to try and channel water for added propulsion and stability. I sanded on both sides of the stringer until I got to a decent depth, about a half an inch, and feathered it out toward the rails. I ran this channel about two-feet up, tapering to even (essentially like a half cone, flattened). I used the Surform Pocket Plane to bring down the stringer, and cleaned everything up with some 220-grit sandpaper.


Once the board has been shaped, run a level perpendicular with the stringer in places where it is intended to be flat. Smooth any dips found by lightly sanding with a block. In spots where more blending needs to be done, especially on the deck and the bottom, do so with a longer block sander that has some flex. When it comes to rails and tail, do so by hand with an extremely light touch—try to let the natural curve of the board works its way out. The tail was particularly difficult for me, taking off more on one side, then the next. I remedied this with the florescent light, then hand sanded until the tail was uniform, touching up with the large block sander.

Working the tail on the twin fin.

In the end, when it comes to shaping there is not much technique involved other than be conservative when eating into the foam and be mindful of the next step, it will help keep from whittling the board down to a tooth pick. And take your time. The smoother and cleaner the shape pre-glassing, the easier it will be to glass later, and the better it will ride in the surf. Remember, it's all about the ride, enjoy the Shore Life!

DIY Retro Twin Fin Surfboard, Part 2: Tools & Shaping

Once the design of the board has been decided, it is time to shape. When researching how to make a board the majority of the stuff I read said use a template, then conveniently posted a place to buy said template.

Tracing out the retro twin fin.

Well, I saved a few bones and went free hand, marking measurements off the stringer every six inches the entire length of the board, both sides, to give the design some symmetry. The shape, as I mentioned in a previous post, is retro twin fin, with a quasi longboard nose (rounded with a bit of a point), tapers in the tail, with a channel running along the bottom. Lightly drawing by hand with a pencil, I ran a line along one side of the board to a predetermined point measured from the stringer. Once the line was correct, I measured every six-inches and mapped them out on the other side. Then I took a Staedtler 24-inch Flexible Curve ruler and bent it to match the drawn line. Using the curve of the ruler, I traced it out along the other side with the mapped out measurements, finishing the nose. I repeated this the length of the board, making it as symmetrical as possible before cutting the board. Once the board is traced out, look at it, envision it cut, shaped and ready to ride. If its off, tweak until it is perfect. But remember, this foam is incredibly soft and easy to take off more than expected. So for the first time board maker, I suggest giving an extra inch to the overall width (half inch all the way around), there will be an inevitable mistake or two, so that extra foam will help when shaving down the blank to make it uniform.

Cutting out the retro twin fi

Using a jigsaw, I cut out the board. When cutting the blank, maintain a 90-degree angle with the blade in relation to the blank, this will help maintain the dimensions originally traced out. The rest of the shaping process was all through hand-tools and good old elbow grease.
There are two trains of thought on shaping: electric and hand-powered. Most pros go power because, well, they are pros. Using power planes, power sanders and routers is great, but most people do not have these tools. And for a first foray into building a board, I would shy away from the power tools; the power planer will eat through the foam in the blink of an eye, and a random orbital sander will put 'smiles' throughout the blank, requiring hand sanding to even everything out while reducing overall foam volume (i.e. floatation). The board will be ruined well before it is glassed.


Surf stands are a key part when making a custom board. I would suggest making a set before undertaking the project. For this first board, I had some padded stands used for boats, but for next project, a set of stands will be the first on the 'to do' list.


Going sans electric (minus the jigsaw and a few steps down the line), I used the whole portfolio of Stanley Surform hand tools, a 6 ½-inch block plane, a Fred Tool for the rails, block sander (hand sized and a flexible custom 22”x3 ½” closed-cell foam ditty I put together), and sandpaper [80, 120 and 220 grit].

Hand tools of the trade.

Shaping is tedious but essential to the overall performance of the board, so take ample time and maintain a close eye to detail; and remember, symmetry is key to a smooth riding board! I started with planing down the stringer, then sanding my way to the rails. I suggest a lengthier block sander, the smaller ones will put dips all over the foam, while the longer ones tend to follow the line and give a smoother, cleaner finish. Sand with complete tail to nose strokes, parallel to the stringer but stop sanding at the nose curve (about 4 ½ feet up from the tail on my board)! It is very easy to gouge into the nose curve, causing a rather unsightly gash and weakening the overall strength of the board. So once the curve has been reached, begin sanding perpendicular to the stringer, gently following the natural curve of the deck of the board. Smooth by hand if needed, but a block should be all that is needed.


Remember, do not to concentrate solely on the deck. Though these preformed blanks come pretty clean, the bottom still need to be fixed up and shaped. Don't take too much off the deck, or it will leave very little room for improvement below.


The bottom is much easier to shape, essentially following the curvature already in place. Take a large block sander and follow the curve smoothly and evenly, with long continuous strokes. When hitting a dip, continue easy strokes and fare it out versus small scrubs, this will only accentuate the problem.

 

 

Shaping the twin fin. Enjoy the Shore Life!

DIY Retro Twin Fin Surf Board, Part 1: Design

As I have taken to surfing one thing has remained the same, prices on boards never seem to drop. A showroom stick can set you back upwards of a grand now, and they seem be more and more temperamental, with pressure dings and fractures happening appearing under the slightest touch. So I decided to get in touch with my inner 1950s Hawaiian and make my own board.

After reading former Surfer magazine editor Matt Warsaw's magnum opus, The History of Surfing [Chronicle Books], which covered the sport from its humble Polynesian beginnings to the current mass market/sub-culture line it tightropes now, the urge to make my own board set like a hook. It is a practice every surfer should experience at least once. After taking a blank and shaping it into rocket to sling under the arm and sprint down the beach toward the tideline, there is a sense of accomplishment, especially when dropping in on that first wave and pulling it toward the lip; it will be one of the most memorable rides of your life. But first things first, design.

Design

Perhaps the most important step in the entire process, design will dictate what the board is suited for. So there are a few things to take into account: what you surf the most (and have readily available in the quiver—don't want to double up too much); what is your home break like; and what do you think you'll want to surf in the future? Design comes down to the individual, this is, after all, a custom surfboard, so some foresight and time is needed before tracing out the board's shape.

US Blank 6'8" P - Soon to be Retro Twin Fin Surf Board

If you do not take your time on this, no matter how much time and effort you expend on the construction, if the design is off, does not suit your break, or is contrary to your personal surf style and/or physical requirements (too big/small, too much/little foam—too much/not enough buoyancy),all that work is for naught; it doesn’t matter if it is pretty, this is about function.

Living in South Florida, in the shadow of the Bahamas, where a decent swell comes in the dead of our too short winter or with a hurricane, I am mostly surfing small, wind chopped, chunky close-outs. So something that can power through the chop without slowing down is a must, which means when tinkering with design there is only one way to go: only short shorts and floral shirts need apply, I tapped into my inner Magnum P.I. and went with a Retro Twin Fin Fish.

The fish is the perfect design for South Florida. Small and responsive with enough buoyancy to keep the nose above the chop, and quick enough to drop in before the wave closes out leaving you with nothing but class four rapids. Using an US Blanks (made in the USA baby!) measuring at 6'8”P, 21 1/2” wide, I chopped the board down to (preglass measurements) 6'1” tall, the width running 14 3/4” (one foot from nose)—20” (at widest)—14 1/8” (one foot up from tail), with a deep 6” swallow tail. Cutting a solid 6” off the nose, the rocker was reduced to 3 3/8” at the nose, with the tail kicking at 2 3/16”. The thickness, after all was planed and shaped, wound up being 2 1/2”—down from 2 3/4”.

For this board I wanted to experiment with a few design features. I am taking some design cues from surf legend Tom Wegener's Seaglass Project with the bottom of the board. The Seaglass is a revival of the Alaia, Hawaii's original surfboards, with some tweeks: they have no skegs (like the Alaia), but the rails are squared and the bottom has a concave groove running through the tail making them incredible riding boards for small waves. With no fins, the board is a little loose, but the concave groove gives the board some stability while the rails suck water under, propelling it like a rocket. You have to get low on the board, and position a lot of weight on the back, but the speed and surprising control are unique and the ride is like nothing else.

Tracing out the retro Twin Fin with deep swallow tail.

For the fish, I am sticking with fins (I am no Tom Wegener), but adding the concave tail, starting a third of the way down, though not as deep as the Seaglass (only about 3/4” deep—I am loosing buoyancy but the speed will make up for it), and I am hardening the rails at the tail, giving them a sharper, more squared shape. I want to see if I can gain some speed while keeping the classic feel, shape and rideability of the fish. I am also running the fins parallel to each other, versus the slight angle of fins found on boards today. The theory is that the concave shape will add to control, the reduced drag of the parallel twins will help with speed, and the deep swallow tail will keep it loose for agility.
 

For glass, I am going with 4oz. S-glass; single layer on the bottom and doubling it up on top. I am also going with Epoxy resin, adding strength and durability to the overall board, while reducing weight from the standard polyester resin of DIY projects. To help with the glassing and epoxy/composite work, I am calling on veteran Catamaran Designer and Master Boat Builder Michael Bell of Offshore Catamarans to help with ratios, technique and any sage advice he might have to offer on hydrodynamics, buoyancy and the chemistry behind the process .

We'll see how the design tweaks work; they may be a bust, but nonetheless, it should be a fun project and I'll keep you folks updated as I move along with the Retro Twin Fin Fish. Keep it classy and enjoy the Shore Life!