Swaylock’s™ Surfboard Design Forum

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BEST OF SWAYLOCK’S VOLUME 4

CONTENTS: How much catalyst to use for gloss coat; How much gloss resin to use; Tips for glassing concaves; Where and how to installing a longboard fin box; Fin placement for thrusters; Best colors for resin tints, Painting between lam and hot coat; What’s a displacement hull; Making your own blanks

I'M ABOUT TO GLOSS. HOW MUCH MEKP (CATALYST) SHOULD I USE IF I’M WORKING IN AN 80 DEGREE ROOM?

[Kokua] I add about 10 to 12 % styrene and now I add some surfacing agent (a good squirt), 25cc's of catalyst - this should kick in about 20 minutes. If the temperatures of the board and the room aren't close then you’ll get a texture and have to sand to smooth it out. After I wash the sanded board I let it set for 1/2 hr before I shoot the gloss. This stabilizes the temperature.
[Herb] at 80 degrees, I’d mix one cc of catalyst to every ounce of resin, plus 15cc of styrene, and 15cc of surfacing agent (in a 24 oz batch).
[Rob Brown] I'm no gloss master but I think you should avoid too hot of a room, so your resin won't be so warm and thin. In the islands our glossing room was kept at 72 degrees. We used an air conditioner to keep it at 72.. We had our best glosses when the boards and room were at the same temperature. Like Herb said, add a little surfacing agent, and I put a little laminating resin (249a) in as well. The little bit of laminating resin makes polishing easy. The gloss will sand better and you can remove the scratches better if you polish it green (like the next day).

FOR A 9 FOOT BOARD HOW MUCH GLOSS RESIN DO I NEED ??

[Rob Brown] Maybe 16 ounces for the bottom, 20 ounces for the deck.. that should leave only a little waste.. I hate not mixing enough when I gloss.
[Cleanlines] I like a cold room and a hot gloss, using Reichold Resin. I don’t measure in ounces, instead I fill a cone cup strainer 3/4 of the way for a 9 foot board. I like using a lot of resin to get a thick gloss. So, it takes about 3/4 strainer of resin, and 35 or 40cc hardener in a room at 70 or so degrees. My glosses jell at the tape within 20 minutes unless I use Silmar resin, which takes an hour.

HOW CAN I AVOID THE GLOSS COAT POOLING UP IN THE CONCAVES?

[Rob Brown] You’re leaving too much gloss on the bottom if it’s filling in your concaves...here’s the steps:
#1 cover the bottom with gloss making sure all the bottom is covered.
#2 make a few more passes to pull extra off..
#3 Cross stroke side to side across the bottom.
#4 now with a light touch from nose to tail do your final strokes to even out the cross strokes.
Doing this should remove any extra gloss that would pool in the concaves....
[Kokua] That's the way I do it too - I think some builders don't realize that when doing the last strokes it's important to apply the same amount of pressure to the brush strokes, especially the last time.
[Teddy] It's good to keep records of the amounts and conditions when glassing. it always comes in handy. Also, you need to pull the tape at the perfect time to get nice smooth tape lines. It saves you some sanding and time.

HOW AND WHERE DO I INSTALL A LONGBOARD FIN BOX?

[Dave] Router out the board just a little bigger than the box. End of the box should be around 6 inches from the tail. Use some cabosil to thicken the resin so the box will stay level and square with the bottom of the board. Also if you create a dam around the box notch the resin will not flow onto the deck. When the resin has set then you can sand down flush with the bottom of the board. Also tape the top of the fin box so resin doesn't flow into it when you do your topcoat.
[Kokua] Five inches up from the tail works good.
[John Mellor] I've installed many boxes with no power tools and it really didn't take that long. After tracing around the box, I taped a metal ruler just outside one edge of the trace as a guide. Using a sharp awl, I poked tiny holes in the corners and scored several times until through the glass - retaping the ruler outside another edge after finishing each side. After scoring, the glass piece peels out and a sharp chisel cuts out the foam. Glass in the box as usual. For a guy doing just a board or two on a budget, it works.

WHERE AND HOW DO I PUT THE FINS ON A THRUSTER?

[Surfhungry] Try 11" up from the tail, then put a pencil dot 1.25" from rail, then 3.5"further up put another dot 1/4" closer to the stringer than the rear dot (toe-in). As far as canting, buy/use a adjustable angle tool (adjust to approx 95 degrees) to use for equal angle-out on both sides. Use a glue gun bead on bottom of fin, hold the fin in place with angle tool until the glue hardens (2 minutes), stand back and look but don’t touch. Now glass them on gently...welcome to the world of garage glassing! You should measure 'toe-in' (1/8-1/4 inch max) from the stringer with carpenters 90 degree angle (very accurately).
[Bruce] Most trailer (center) fins on a thruster are between 3" - 3.5" forward from the tail. Toe-in can be set like in the John Carper video [Glassing 101], running a straight edge from the side fins rear edge measurement to the nose, or an inch or two past. This gives me a rough measurement that I then measure off the stringer. Only use that method when doing a totally new length or shape.
[Alaska] 1/4" inch toe-in will work on shorter boards but on a 7' or longer board it’s way too much. (It will put your toe-in angle on the opposite side of the stringer if you carry that line to the nose.) Use 1/8" toe-in for the longer boards, 1/4" for the shorter boards.
[Jim Phillips] Think of it this way: the more rocker a shape has, the straighter forward the fins can be placed. With a real flat tail rocker the more toe the fins will need. A flat board will ride on the bottom more than on the rail, so it needs more toe in. As far as caster, I personally like the tips tilted out quite a bit, it feels like the fin is more vertical when the board is in a hard turn.
What I use for my shapes is templates with the toe-in cut on them. I butted my square along the edge, finding half the intended width and marked both sides. I.e., 12" apart 6" on template. The template is long enough for shorties (5'6" with fins 9-10" apart) to long boards with fins 13-14" apart. Just slap it against the stringer and slide it along until you like what you see. I always hated using a square to set up the 4 dots that were needed. I have 3 different templates, ranging from more toe for rockery designs and less for flatter boards.
With too much toe-in a board will ride badly – it will bottom turn OK, but off the top, the tail will track along the lip with the nose in the trough (the outside rail fin steers the tail down the line). With the fins pointed straight ahead, no problem in turns. Rocker and fin placement are the KEYS to a good riding board.

WHAT ARE THE EASIEST COLORS TO USE FOR TINTING RESIN?

Yellow is the most forgiving. It will even hide small imperfections, like screen marks, scratches, etc. Some of the lighter tints in orange, green, and blue are good to go. Just stay away from dark tints, especially, red, and purples.

CAN I PAINT BETWEEN THE LAMINATING RESIN AND THE HOTCOAT?

Posca pens work.
[Herb] First: make sure your paint is compatible, Second: spraying on the lam will show weave and drips and drools in your finished product. Third: go light on the paint ,if you overly spray the lam with paint your hotcoat WILL pop off or delaminate.

WHAT SHOULD I USE FOR SANDING/GRINDING LAPS?

[Greg Loehr] We use a variable speed Hitachi sander with an 8" hard soft pad and 80 grit production paper, and use low speeds.

WHAT IS A DISPLACEMENT HULL?

[Tom] It's a fairly complicated bottom design that works well on waves that are lined up, with some power. Basically a displacement hull is a bottom with varying degrees of convex curve that allows the board to roll onto the rail easily from a more forward position on the board. This is combined with a deep, high aspect single fin placed up pretty far up on the board. The roll in the bottom toward the nose causes drag which in turn pulls the board up into the pocket. The reverse V bottom which we are currently riding in powerful waves is the modern interpretation of the displacement hull. The dislacement hull lends itself to a forward riding position, so a lot of old school single fin guys enjoy riding them.

WHAT’S A GOOD BLANK FOR A LONGBOARD?

What you need is the 9'8"S, the same thickness profile as the 9'7"B, a true 9'8 1/2" long and glues to many different rockers without distorting. Has a bit thinner nose than 9'7". I use it and like it. I also use the 9'10" when I need it.

IS IT POSSIBLE TO MAKE MY OWN BLANK?

[Greg Loehr] The making of urethane foam is very toxic, expensive and difficult to do. It takes a large capital outlay for molds, chemicals, safety gear, etc. Conversely it is quite easy to make a polystyrene blank. You can generally get blocks of foam locally from insulation foam suppliers. The rocker templates are made from 1/8 inch masonite. They are attached to the block with nails and you then slice the foam with a harp, strung with a piece of nicrome wire, that is powered by a variac. A variac is a voltage regulator. For the foam, look in the yellow pages under insulation and look for a supplier of foam. Almost every major city has at least one. For the variac, they are available from Wicks aircraft. They have a nice voltage regulator for hot wiring for about $100. I think they also have wire. They have an online catalogue at www.wicks.com. The harp is just a piece of plywood cut in a U with the wire strung across the open end. It has to be wide enough to fit across the foam your cutting and deep enough to cut the thickness of the blank. Give yourself lots of room on that one. You attach the voltage regulator to each side of your harp (we use alligator clips), turn the regulator up to about 25 volts and your ready to cut. Set the wire on the templates that are attached on either side of the foam block and push the wire slowly through the foam. When you finish the deck, hook the wire under the templates and pull it through the bottom. It helps to have a fan blowing down the block of foam to cool the exposed wire that's outside the block otherwise that portion of wire super heats and you break a lot of wires. After you've cut your blank, set it on a shaping rack bottom up. Get a piece of hot wire long enough to reach the length of the blank and about 2 feet extra. Attach a piece of wood (these are handles) to each end of this wire. Now attach the voltage regulator to each end of the wire. Now you need to find the middle of the blank and mark it on each end. You need a friend to hold one end of the wire while you hold the other. Set the voltage at about 70. Stretch the wire from end to end on the marked center of the bottom of the blank and turn on the variac and slowly pull the wire from the bottom of the blank to the deck. You now have the blank cut for the stringer. You need five bar clamps to glue up with. For a stringer you can use 1/8 or 1/4 inch Luan plywood which is available at Home Depot. This stuff doesn't shape great but its easy to find and works. You can also use 3 mil PVC which comes in 4x8 sheets and is available from sign supply companies. Comes in colors and looks great. For gluing Luan you can use good old Elmer's glue. For PVC there is a glue called Roo Glue that works well. You can probably find that on the web. When you glue up, you wet both sides of the stringer and both sides of the blank line up the parts and then bar clamp it together. And that's about it.