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FINS

Removable fin systems are probably the best choice - fins and fin positions can be changed in relation to wave size and speed.  This will drastically change the way a surfboard maneuvers.  Also fin removal makes for better travel.  It is nearly impossible to take a board with un-removable fins on any plane or bus.  Note that many builders say fin installation is especially difficult.  Practice first. 

If you cannot decide on which fin setup to use, do the following:

1. For a longboard use the 8" standard molded fin with 10.5" box from www.surfsource.net.
2. For a thruster or twin use the future fins molded tri or twin fins and boxes from www.fiberglasssupply.com.  (Future Fin systems are usually installed before laminating - after shaping, using a different technique - See below).
3. For an alternative see - SMALL WAVE DESIGN .

The molded fins are about half the weight and less than half the cost of fiberglass fins and work great.  One big advantage of the molded fins are that they tend to break before the rear of the board becomes damaged - use breakaway fin plates (if possible).  It's generally not economical to make your own fins.  Note that a large molded fin (about eight dollars) can easily be cut and shaped to almost any shape. 

If not doing a gloss coat, do the fins before the hot coat.

Please check and recheck your measurements, and templates.  If you practice, it will be easier and less stressful.

The following instructions will be in five parts; PART 1 - SINGLE FINS, PART 2 - TRI AND TWIN FINS, PART 3 - FCS, PART 4 - GLASS ON FINS, and PART 5 - MAKE YOUR OWN FINS.  The stringer and no stringer methods are meant to be used with the five part instructions which follow them.  Please practice on scrap foam first - especially wood removal.

STRINGER METHOD (wood or glue joint removal at fin box hole)

This method requires using the drill as a router.  Do the following:

1. Obtain a router bit deep enough for your box depth (take box to store).  Put router bit in drill.
2. If drill has two handles and a depth rod, hold the box bottom even with the router bit end and adjust the depth rod to the top of the box (rod will slide on laminate or hot coat).  If thedrill has no depth rod, cut a scrap piece of foam about 1" x 1" x 4".  Tape the foam to the side of the drill at the depth needed (1" end of the foam will slide on the hot coat).  Try to router the hole so the box top will be flush with the laminate or hot coat.
3. Slowly cut the stringer material first.  Hold the drill tightly, being careful to control the hazard of the router bit grabbing and bouncing off the wood, causing a cut outside the lines.  Stay about 1/16" inside the fin box outline.  Finish hand sanding to a snug fit.  Note:  If you have no power tools the stringer material can be removed with a chisel or an old sharpened screwdriver, after first cutting the outline with a hack saw blade (as mentioned below).
   

NO STRINGER METHOD (foam removal only)

Note that a nice fin box hole can be made with no power tools.  Using a router or drill to make a box hole, is risky for first timers.  All that is needed is a hack saw blade and a piece of 20 or 50 grit sand paper.  Try the following steps:

1. Cut one end of the hack saw blade at a 45 degree angle, and the other end at a 90 degree angle with tin snips etc. If the hack saw blade can not be cut, simply break the ends with a pair of pliers (after breaking the blade ends, use the pliers to straighten the slight bend which the break will cause).
2. Wrap the hack saw blade with about 10 wraps of duct tape at the box depth (prevents blade from over cutting depth).
3. Using the sharp (45 degree) end of the hack saw blade, force the sharp tip into, and through the laminated cloth inside the box outline.  Cut about 1/16" inside the box outline.(any unevenness and smallness will be corrected by sanding).
4. Remove the cut cloth.
5. Cut lines across the foam within the box area, 1/8" apart to box depth lengthwise and, 1/2" apart crosswise).
6. Remove the cut foam with your fingertips, and scrape the bottom with square end of the hack saw blade.  The walls and bottom can be sanded with #20 or #50 folded over (about 4 folds) to a small, stiff rectangle (try to match sandpaper width to box width).  Only the top edge of the box hole will be visible (try to get a snug fit - any unevenness in the foam can be filled in with resin when installing the box).

   

   

PART 1 - SINGLE FINS   (practice on scrap foam first using the STRINGER METHOD or NO STRINGER METHOD above).  Install after laminating.

Do the following:

1. Mark the fin box location using the measurements from the model board (probably 4 - 5" from the tail end for a 10.5" box).
2. Router the hole using the STRINGER MEHOD or NO STRINGER METHOD
   
   
   
3. Rough the box with #50.
4. With the fin still in the box, tape very carefully around the fin so resin cannot get into the fin box (Figure 19).  Use chemical resistant tape or duct tape.  Note that some fin boxes come with the top sealed.  Sand the top seal off and installing the box with the fin, to insure straightness. Although there are photos below of taping around the box hole - this is not needed.  Simply wipe up the excess resin with paper towels.  This will eliminate the possible problem of resin hardening over the tape, making it very difficult to remove.  This also eliminates the problem of the tape being pulled too soon, causing fin misalignment.  Be double sure resin can not get into the fin box (always tape around the fin).
5. Cut 2 -4oz. strips of fiberglass cloth at least 1" wider and longer than your box hole on all four sides.  Test the fit by centering the dry strips over the hole and smashing the box all the way down.  Adjust as necessary for tight fit.  The box should be flush or barely sticking up.  Remove the box and the strips.
6. Make sure the board is level on the racks.  Use the torpedo level, angle finder or, anything that is ninety degrees  Note:  If the board is exactly centered below a light it will be much easier to see if the angles are accurate.  You might need to put a 6" x  6"  piece of cardboard near the side of the fin box.  This will create a level surface to put your ninety degree tool on. which will span the wet cloth. 
7. Make sure the following is available before you mix the resin:  wax paper, 1" masking tape, razor blade, gloves, angle finder etc.
8. Epoxy : Mix about 2oz resin and 1 oz hardener.  Polyester:  Mix about 3oz resin with 1cc cat. and 2cc wax (measure with syringe)  
9. Put the 2 - 4oz. strips on wax paper, and pour about half the resin on them.  Squeegee the resin evenly into the cloth.
10. Center the wet cloth over the hole and push the box all the way down.  Pour the resin mix around the box edges until it runs out.
    
    
    
    Note:  the tape shown on the board above often causes more problems than it is worth.  Skip the taping shown and simply wipe up any excess with a paper towel.  Always tape around the fin in the box, however.  Make double sure resin does not get into the box.  Use only duct tape or chemical resistant tape.
11. Set the angle of the fin/s using a fin angle template (see DESIGN) or angle finder tool.
12. Tape the fin by running 1" masking tape from the top of the fin to both edges of the board.  Trust your eyes.  If the light is even, and it looks crooked, it probably is crooked, even if it was perfect before it was taped.
    
           
    
13. When the resin is rubbery, pull the tape where the fin meets the box, and remove the fin.  Do not worry about the cloth sticking up - this is easily sanded down later.
14. If the box is sticking up put 3 layers of duct tape around it and sand it with #50 disk till the tape starts disintegrating.  Stop.  Remove the tape.  This tape will keep the cloth from being sanded into around the fin base.  The disintegrated tape can be removed with alcohol and a razor blade.  Note:  If you leave the box sticking up very slightly it is much easier and safer.
    
    

Single fins can be installed using the same method as tri and twin fins (below).  This is slightly easier and it is the way many pro shops do it now. However;  by using the method in this section it is less likely the cloth will be ripped around the box if you hit a rock etc., (this is rare if you use breakaway fin plates).

PART 2 - TRI AND TWIN FINS (usually installed directly after shaping, using the STRINGER METHOD or NO STRINGER METHOD- practice on scrap foam first)

Future Fins systems recommend routering the hole before you laminate (after shaping).  Future Fins also recommends buying their very expensive tools.  To the contrary;  Future Fins boxes can be installed using much the same technique as above.  Practice on scrap foam first.

Directly after shaping (before laminating).

F ollow the steps:

1. Mark out the box flange and the box (square part that fin fits into - ignore the ribs).  See GLASS ON FINS below for more location information.  Cut the box hole only (not the flange) with the hacksaw or drill/router using the STRINGER METHOD or NO STRINGER METHOD above.  It is critical that this be a tight fit.
2. With a lone hack saw blade (break or cut off a 1" piece of saw blade) scrape away the foam in the area the flange will sit on, until the top of the flange will be flush with the surrounding foam.
3. Push the box slowly into the hole testing for flush fit.
4. Reinsert the box in the hole and make sure the flange is flat (flush) on the surface of the board (if the box flange is flush, the side fins will be about four degrees, on Future Fins).
5. Pull the box out again, sand it with #50 and, wipe it with alcohol.  Tape plastic box hole with duct tape or chemical resistant tape.
6. Cut two 4 oz. layers of cloth in a football shape to cover each box (about 1" beyond box edges).
7. Mix about 3 oz. resin for each fin. Use epoxy if using a polystyrene blank.
8. Using your gloved fingertip, apply a thick layer of resin to the box (including the underside of the flange), box hole and, foam flange area.
9. Insert the box into the hole.
10. Put the football shaped layers over the box and saturate the cloth with resin.  Wipe up any excess resin before it gels.  Note that this fin system gets much of its strength from the laminate coat which will later cover most of it

PART 3 - FCS

FCS is the easiest to install and the easiest to damage.  FCS can be installed using the same method in the LEASH PLUG chapter (see conventional leash plug).

PART 4 - GLASS ON FINS

If glassing-on (un removable fins) it saves a step to do it before the hot coat.
Please follow the steps:

1. Mark the fin(s) location according to your model board.  Please note that the measurements below will not give optimal results on all boards.  If you do not have a model board you are copying, keep the rear bottom fin edge (on the side fins) about 1" from the rail edge.  If you draw a straight line along the side of a side fin, it should end up about 2" ( varies) from the mid tip of the nose (on that fin side).
   
   Figure 20  Note:  The 51/2" below should be about 51/4"
   
   
   
   Make sure the board is level on the racks and light is centered overhead.  Use a fin angle template (see DESIGN) or angle finder if the fin lean angle is needed.  This angle is four to eight degrees (four is common). 
2. Hold the fins in place with 1" masking tape run from the fin(s) tip to both board edges.
3. Mix some resin/catalyst and drip it around the fin(s) base (just to hold them in place).  90 second or 5 minute epoxy works well for this.
   
   Figure 21 Note:  The fin lean angle below can be from 4degrees to 8degrees.
   
   
   
4. Cut fiberglass rope about 1/2" longer than fin base (both sides).
5. Cut 2 layers of 4oz. cloth to fit about 3" up fin height and  about 3" across the board for each side of each fin. 
6. Mix about 6oz. total resin and hardener for a single longboard fin - about 3oz. for each thruster fin.
7. Saturate the rope on wax paper (keep it straight).
8. Lay the rope at the fin base (one on each side).
9. Saturate the cloth and put 2 layers on each side of the fin. Smooth out the rope curve with a finger. 

Note:  The fin will break off cleanly, rather than possibly tearing a hole around the fin base, if the following is done:  Reduce the amount of rope to about 1/4 the original amount or just replace it with 4 - 4 oz. strips 1/2" -  1" wide on each side (narrower cloth to the center).  Please realize that the fins will break off easier this way but more cleanly.  Cut excess when gelled.  Remove tape. Prepare to hot coat.

PART 5 - MAKING YOUR OWN FIN (do this only if shipping is a problem)

Probably the easiest and cheapest way to make a fin is with wood.  Cedar fence wood works well.  A 6’x 5&1/2” x 1/2"” piece costs about $2.50 in 2008.  Cedar is light, rot resistant, beautiful, and shapes easily.

1. Make a fin template from cardboard etc.
2. Trace the template on cedar fence wood.
3. Cut the wood 1/4" outside the template outline, with a hand saw (consider cutting and making two wood cores - one for practice).  Use a hack saw etc.
4. Use a drill with #16 sanding disk to shape the wood core.  Put drill in vise or put weight on top of the drill to stabilize it (brick etc.).  Pay close attention to the foil.  The front edge should be rounded, with the 3/8" thickest point of the fin, about 1/3 of the distance from the front edge.  It should gradually become thinner from this point, to become almost sharp at the rear edge (similar to an airplane wing).  If you do not shape it this way it will likely vibrate and hum loudly.  See http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html. If you are making twin or tri fins, foiling the inside face of the fin is not needed (it can be flat), although it will work if you do foil it.  Always symmetrically foil both sides of center fins. Finish hand sanding with #50.
5. Mix 1 oz. total resin and hardener and coat wood core on all sides.  Leave about 1/4 of resin in the container, and recoat the fin before the resin hardens – the resin will sink into the wood on the first coat.
6. Place the fin bottom down on a sheet of wax paper (brace it with a brick etc.,).
7. Repeat # 5.
8. When hard, do not sand with power sander - you may sand into the wood.  Hand sand.  Start with #50. Sand bottom edge with sanding block.
9. Fine sand and buff as in GLASSING if desired.

Using cedar for a core will make a beautiful, light fin.  People will stop to look.  The fin will float on its own.  I am assuming you will be glassing on your fin if you make your own.  If you can get a box shipped, you can get a fin shipped.  It is not worth making your own fins unless shipping is a problem.  Note:  An entire surfboard could be made from cored (drilled to remove about 50% of wood) and glued cedar fence wood.  This would be similar in price to a foam board assuming cloth would not be used on the cedar.  The cored cedar board would be heavier and more work, but very beautiful.  Numerous surfers have built cored boards with other woods, but I know of no one who has used cedar.

Please install a fin box if possible, and please practice first.

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