How to Build Your First Surfboard
by Stephen Pirsch

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RESEARCH FROM SURFERSTEVE

BONDING
Cloth to foam bonding tests done on 3lb/cu. ft. Polyurethane (PU), 2lb/cu. ft. Expanded Polystyrene (EPS), and 2lb/cu. ft. Extruded Polystyrene (XPS), using 4.5oz., 6oz. 8.5oz., 18oz., and 19.5oz cloth all saturated with epoxy resin. 4.5oz and 19.5oz. are carbon fiber. All plain weave E except 8.5 E twill and 19.5 carbon twill. Laminations were done on 1/10 scale surfboard models. Foam on all models was roughed with #20 or #12 floor sandpaper (#20 if not mentioned) prior to lamination. Cloth sections were 2&1/2" x 8" all laminated with epoxy resin.

Test #1
PU, EPS, and XPS, each laminated with one layer 6oz plain weave cloth and epoxy resin.

PU - Easiest by far to pull 6oz. hardened cloth off foam. Once started, cloth pulls off easily, in one piece, with almost no foam stuck to cloth. Although the loser in this test, in the real world of heat, leakage, and pounding, PU is superior to XPS in it's ability to stay bonded, and closer to EPS than these tests indicate. Most builders do not increase the amount of cloth on 2lb. EPS boards compared to 3lb. PU boards - this tends to even them out.

XPS - Able to pull cloth off foam roughed with #20 sandpaper with difficulty, but cloth came off in one piece mostly covered with thin layer of foam which stuck to the cloth. On XPS roughed with #12 sandpaper cloth could not be removed without tearing cloth into sections. Thicker layer of foam attached to cloth than with #20 sandpaper model. #12 XPS sandpaper model was roughly equal to #20 EPS sandpaper model with lightweight spackling seal in bond strength.

EPS - Clear bonding winner. Barely able to pull cloth from foam sanded with #20 sandpaper. Cloth tore in sections and was so difficult to separate from foam that it broke the blank. Cloth was covered with foam beads sometimes more than two layers thick. This model had no spackling or epoxy with micro spheres - no sealer - See with sealer below.

Test #2
EPS roughed with #20 sandpaper, unsealed, sealed with lightweight spackling, and sealed with epoxy and micro spheres (hollow glass bubbles), all roughed with #20 sandpaper prior to sealing or lamination. Each model laminated with one layer 6oz plain weave cloth and epoxy resin.

Epoxy and micro sphere seal - Easiest to pull off of all EPS tests, but still excellent - about equal to #20 sanding on XPS. Cloth and sealer pulled off in one piece covered with thin, even layer of foam beads. Although the cloth to sealer/foam bond was weaker, the stiffness, and strength (except for bonding) of the laminate is greater with this method due to the extra resin.

Spackling seal, one thin layer - Able to remove cloth only in two sections. Thick layer of beads, mostly one layer, sometimes two layers thick, attached to cloth. Apparently, the resin went through the spackling into about two layers of beads. The laminate is clearly more flexible using this method than with micro spheres - slightly more flexible compared to no seal.

No seal - Clear bonding winner as mentioned in Test #1. No extra resin was used on the no seal model. It appears that more resin soaked into the blank using this method, but it seems probable that the increased amount of resin is not more than the amount used in the micro sphere and epoxy sealer. So...you will get a better bond with no sealer, but the micro sphere epoxy sealer will give you a stiffer laminate - everything else being equal.

Test #3
Four XPS models. All roughed with #20 sandpaper. All models laminated with epoxy resin.

#1. One layer of 8.5oz twill weave. Pulled off evenly, in one piece, with uneven, small amount of foam stuck to cloth. Cloth is about 95% clear of foam.

#2. Two layers of 8.5oz twill weave laminated at one time (not separately laminated). Pulled off more easily than single layer. Almost no foam attached to cloth. Cloth shows uneven saturation - not fully wetted out. Apparently, the density of this twill weave cloth and the thickness of epoxy are not compatible in more than one layer. Although not recommended in layers, 8.5oz twill is almost exactly the same thickness as 6oz plain, so, it requires the same amount of laminating resin but is stronger and requires slightly less hot coat resin to fill the weave - use only when weight is paramount. Twill weave is practical in two layers only if the layers are laminated separately

#3. One layer of 6oz plain weave. Pulled off evenly, in one piece, with a thin uneven layer of foam stuck to cloth.

#4. Two layers of 6oz plain weave. Pulled off evenly, in one piece, with a thin uneven layer of foam stuck to cloth - slightly less foam attached to cloth than with single layer. Slightly easier to pull off compared to single 6oz. Cloth shows even and complete saturation.

#5. One layer 18oz plain weave deck patch (6" x 2&1/2") with 1/4" overlap over 6oz. plain (2&1/2" x 2"). Clear bonding winner. Pulled off evenly, in one piece, with a thick even layer of foam attached to cloth. More difficult to remove compared to all other XPS models (except for #12 sanding model in test #1 above). Bending cloth to 90 degrees at overlap did not cause separation between 6oz and 18oz. Using single 18 oz. on the deck patch and overlapping slightly at cloth junction creates a better bond than using multiple layers completely over each other on the deck patch. Instead of double 8oz. use single 18oz.

#6. One layer 4.5 oz. plain weave carbon. Pulled off with great difficulty. Especially hard to start de - bonding, then once it is free side to side the length separated evenly with thin even layer of foam attached to cloth.

#7. Two layers 4.5oz plain weave carbon. Pulled off slightly easier than single layer above, with less foam stuck to cloth, although bonded much better than average of tests.

#8. One layer 19.5oz twill weave carbon. Very hard to start de - bonding - had to use chisel. Once started, pulled off cleanly and surprisingly easy. Thin even layer of foam attached to cloth.

#9. Two layers 19.5oz twill weave carbon (both layers laminated at same time). Hard to start de - bonding - used chisel. Once started, pulled off easier than single layer above. Very little foam attached to cloth - shows uneven saturation. Resin did not adequately penetrate both layers of cloth.
a. Two layers 19.5oz twill weave carbon - used de - bonded cloth from #9 above. Easily inserted screw driver between layers and once started the two layers de - bonded from each other easily, showing uneven resin saturation.

#10. One layer 19.5oz twill weave carbon laminated and hardened then a second layer of 19.5oz. twill weave carbon laminated over the first layer. Very hard to start de - bonding - used chisel. Once started pulled off cleanly and surprisingly easy (easier than #8). Thin layer of even foam attached to cloth. Inserted screw driver between layers with much difficulty, and found the layers almost impossible to separate (separated only by breaking off small sections). Test #9 and #10 strongly indicate twill weave should not be laminated in layers at same time, as test #2 also indicated.

Conclusions for bonding:

1. The rougher the surface, the better the bond.

2. Bonding. Polyurethane - Good, Extruded Polystyrene - Better (but actually inferior to PU in the real world), Expanded Polystyrene - Best

3. EPS bond and sealers. Epoxy and Micro spheres - Good, Lightweight Spackling - Better, No Seal - Best.

4. Do not laminate twill weave in multiple layers at same time.

5. Plain weave is preferred but avoid multiple layers when possible. On deck patch use single layer of 18oz. cloth in place of a double layer of 8oz.

 

COROPLAST
Tests of 4mm Coroplast - corrugated plastic sheet (standard sign sheet) versus 2lb./cu. in. XPS (25psi) foam. Includes bonding coroplast to: itself, XPS, E cloth, and carbon cloth. Also; includes weight differences per unit of area, and strength differences using 165lb. person. Coroplast is similar to card board in construction, but is made of plastic. In 2013 it is $18.25 for a 8'x 4' sheet. It comes in many colors. It is made 2,4,6,and 10mm thick. Available in small sign sizes at Lowe's in the sign section. Coroplast could be used as a surfboard/sailboard core or as a stringer.

#1. Bonding coroplast to itself edge to edge, and face to face using 5 minute epoxy. Twisted and flexed Corplast until it folded. Joint stronger than material. No bond failure. Material will tear away or break before joint fails (no sanding or preparation of coroplast done).

#2. Three mock stringers of coroplast each 2'x 1" x 4mm. Mock stringers placed 6" apart, edge up with a 2' square sheet of 1/4" plywood on top. Cement blocks braced the sides so it would not tip over. Supported 165 lb. person with no deformation of Corplast.
a. Same test as above done with 3 XPS pieces (2'x 1"x 1") placed 6" apart. Slight deformation of foam felt but foam showed no damage (felt spongy on first step) - compressed slightly but returned to original shape.

#3. Three mock stringers of coroplast each 3"x 1"x 4mm. Mock stringers placed 1" apart, edge up with a 3" square pre - laminated piece of 19.5oz carbon fiber on top, and bottom. Carbon glued (generously) to coroplast with 5 minute epoxy. Supported heel of 165lb. person with no deformation of coroplast. When rocking heel on 3" square test piece Coroplast slightly deformed on edges only if entire weight rocked to edge.

#4. Equal volume of Coroplast and 2lb./cu. ft. XPS. Coroplast three times heavier (used postal scale).

#5. 6" square section of Coroplast was epoxied to 3lb polyurethane foam (face down - flat), then 6oz. E cloth was epoxied over the coroplast. A baseball with entire 165lb persons weight was forced straight down upon the Coroplast. A slight cracking noise heard. Very slight softening evident at baseball pressure area.

#6. Corplast (with no covering) samples smashed face down with heel of hand til crushed flat. Corplast returned to near normal thickness, but permanent softness results, as the internal webs are slightly bent by being smashed.

Conclusions for Coroplast:

1. Excellent bond to itself, foam, or carbon cloth. Short sections can be epoxied together with no joint problem.

2. Coroplast will make an excellent stringer material (cheap, waterproof, light, and stiff long wise and edge to edge). Scale models indicate it can be used as a substitute for foam as a surfboard, sailboard, and SUP core when placed 1" apart, or about 5" apart if 2 - 19.5 oz. carbon is used on the deck of a hollow surfboard.

3. When substituting Coroplast for 2lb/cu. in. foam use 1 - 4mm thickness in place of the equivalent of 1"thickness of common surfboard foam - this is if the same amount of shell material is used.

4. Coroplast is probably not well suited to be a surface covering on a surfboard. Once even slightly deformed face to face it becomes permanently soft.

 

DENTING AND PUNCTURING
Tests denting and puncturing the following: 4oz. E, 4oz. S, 6oz E, 8oz E, 8.5oz E, 18.5oz. E, 4.5oz. carbon, 19.5oz carbon. 2lb.cu.ft. EPS foam was used for lamination of various cloth. A baseball was used to simulate heel damage, with 165lb. person instantly putting entire weight straight down on ball. Puncturing was done using a two foot long by 1" thick pointed steel rod, with a 165lb. person instantly forcing his entire weight straight down onto the rod.

 

DENTING AND PUNTURING
4oz. E - 1/4" ball depression. Rod went through laminate and entire 4" thick blank.
4oz. S - 1/8" ball depression. Rod went through laminate and entire blank.
6oz. E - 1/8" ball depression. Rod went through laminate and entire blank.
8oz. E - No depression. Rod went through laminate and entire blank.
8.5oz. E - No depression. Rod went through laminate and entire blank.
2 - 4oz S - No depression. Rod went through laminate and entire blank with strong resistance.
2 - 8oz E - No depression. Point of rod entered laminate 1/8" and stopped.
18.5oz. E - No depression. Point of rod entered laminate 1/16" and stopped.
4.5oz. carbon - No depression. Point of rod would only penetrate if placed exactly at hole in weave, and then only 1/16".
2 - 4,5oz. carbon - No depression. No entry no matter where rod point placed.
19.5oz. carbon - No depression. No entry.

Conclusion for denting and puncturing:

1. Use 8oz. E bottom with 8oz. E on 1/3 top at nose end, and 18oz E deck patch on 2/3 top at tail end. This lay up is simple, cheap, and damage proof to most common surfboard damage, especially the killer; deck delamination.

2. Carbon fiber is beginning to be financially practcal again, as suppliers such as uscomposites.com have discounted carbon fabrics usually listed now. Although most builders will take a glance at the price and think it unreasonable, consider the following. The width is often 50" or 60". This can be cut in half, which reduces the price by half. Since carbon is about twice as strong as E cloth, you only need half the weight, which may reduce the price by half again - this may bring it to under $10 per yard. Although most will continue to avoid the cost of carbon, it is a good option for a deck patch. For a light, strong deck consider using 2 yards of carbon (or one yard cut in half) on the deck patch as a stand alone layer (no other cloth over or under it).

 

LAMINATION, ESPECIALLY WRAPPING RAILS BY FIRST TIME BUILDERS
Do not's and do's of laminating based on over 50 years of personal trial and error, and viewing first time builders trying different methods. In every "do not" mentioned, something strongly negative occurred.

DO not's and Do's for first time builders - this is not meant to insult professional builders.

Do not laminate without practicing with scrap.
Do practice - nothing else mentioned here is as important.

Do not use expensive rubber type squeegees, rollers, bubble rollers, brushes, or pads.
Do use cheap plastic throw away squeegees

Do not...no matter how many times you have seen a professional on youtube do it... do not pour all your resin out of the container onto the cloth at one time. Especially, do not pour resin quickly down the rail letting it run down the cloth and run onto the floor. This is impossible for a first time builder to do without major problems, such as; not having enough resin, and stepping in wet and hardening resin.
Do pour either 3/4 of total resin in concentric circles saving 1/4 for rails, or, better, pour 3/8 on one half, 3/8 on the other half, and 1/4 on the rails.

Do not use the cut lap method (again; common on youtube). This wastes a huge amount of cloth, resin and tape. Cut lap is very hard for a first timer to do. Pouring resin down the rails and using cut laps causes builders to use close to 1/2 the total resin for the rails, as compared to 1/4 which is recommended here. This is the industry standard mostly because time is more valuable than material, and it tends to make the finished board look more perfect.
Do use the free lap method.

Do not wrap the rails with squeegee at 45 degree angle to the rail (again; common on youtube). First timers will bunch and fray the cloth.
Do wrap the rail at 90 degrees to the rail.

Do not try to copy a professional glasser - not meant as an insult.
Do wrap the rails using the method seen on the youtube video, How To Build Your First Surfboard, from the link on this site. This method uses a 2' x 4" piece of cardboard under the rail cloth, to hold the cloth horizontal while pouring resin on the lifted cloth. The cardboard method may be easier if the rails are wetted before the middle, putting the container on the dry cloth on middle top of the surfboard - this is because the container will need to be put down when using the squeegee, as the other hand is holding the cardboard. If you do not want to pour resin, or move the container, the squeegee can be dipped into the container and the resin on the squeegee can be applied directly to the cloth. Note; If doing the rails first, switch sides every two feet so the cloth will not be pulled out place by the weight of the resin on one side. This may sound complicated, but it is preferred by all first timers who have tried it, as wetting the rail cloth is very difficult for a first timer.
a. One more method recommended is to flip the hanging rail cloth up onto the up side of the blank, (just enough so it does not fall back down). Wet out one side of the rail cloth (1/2 the board) then very slowly, starting at one corner, separate the wet, flipped up rail cloth from the wet cloth it is on top of, pulling at about 45 degrees to the rail - leave one corner dry (starting point), or you will have a big problem trying to grasp the edge of the cloth. Flip the cloth so it again hangs over the rail. Repeat on other 1/2 of board - if you wet both halves at once the cloth will be harder to separate.

Do not laminate without practicing with scrap.
Do practice - please.

 

EPS WATER ABSORPTION
2 - 1/10 scale EPS/Epoxy models with 2 - 1/4" diameter holes drilled halfway through model. Model weighed dry with postal scale. Model submerged 1/2" under water for 24 hours and weighed. Model weighed as it dried.

#1 Foam - 6 grams.
Finished, sealed model - 25 grams.
Model after 24 hours in water - 27 grams.
Model after 48 hours in water - 30 grams.
Water absorption after 48 hours - 5 grams.

#2 Foam - 9.5 grams.
Finished, sealed model - 41 grams.
Model after 24 hours in water - 47 grams.
Model after 48 hours in water - 52 grams.
Water absorption after 48 hours - 11 grams.

Conclusions: 2lb.cu.ft. EPS foam generally can absorb it's weight in water. Most EPS surfboards are made with 2lb./cu. ft. foam. The average of all surfboards now sold is about 2.5 cu. ft. of foam per surfboard. So... if the average EPS surfboard is allowed to leak long enough, it will absorb about 5 pounds of water - this is probably rare, as most people surf irregularly, and there is time for the foam to dry in between surfing.

EPS natural dry time tests to come.

 

GLUE TESTS
Glues tested:

1. Epoxy (Uscomposites Kleer Kote and Devcon 5 minute epoxy)
2. Epoxy with 50% (by volume) micro spheres added.
3. Gorilla glue.
4. Great Stuff spray foam (red can).

Note 1: Glues tested on three foams. EPS, XPS, PU.
Note 2: Test panels 3"x 3"x 1" glued edge to edge (1"edges). Panels allowed to dry for 24 hours before attempting to separate glue bond. Breakage was done by hand.
Note 3: Water tests done on duplicate test panels, which were allowed to dry for 24 hours then totally submerged in water for another 24 hours before attempting to separate the glue bond.

Results:

1. All four glues are excellent for gluing common surfboard foams.
2. All four test panels broke at the foam, not the joint interface.
3. Best adhesion is in the following order: Epoxy, Epoxy with micro spheres, Gorilla glue, Spray foam.
a. Epoxy and Epoxy with micro spheres was impossible to break at or across the glue joint.
b. Gorilla glue and Spray foam allowed breakage across the glue joint, but not at the joint interface - only where very precise pressure was applied.
4. All four glues are very water resistant (seem to be water proof), and bond strength was the same after water immersion for 24 hours.

Recommendations:

Epoxy and micro spheres are nearly clear, and clearly the best. This combination allows for relatively thick mixture which resists moving out of the area it was applied to. If you are building with polystyrene foam, you already have epoxy, so why buy more adhesive, when epoxy is the best? Gorilla glue is good, but it is ugly brown, and much more expensive than epoxy or spray foam. Spray foam has one big advantage - it shapes almost exactly as 2 lb. polystyrene foam shapes, so...you can apply it without worrying about it being in the area to be shaped. Spray foam has a few draw backs - it expands too much, sets up too quickly, is ugly brown, clogs the can, and is more prone to delamination at the joint than is epoxy. Conclusion: epoxy and micro spheres

 

WHITE PIGMENT AND EPOXY
Tests of white epoxy pigment in Uscomposites Kleer Kote Epoxy at ratio of 40:1, at a ratio of 20:1, with Nu Finish car polish, and without any covering. Three samples exposed to about 10 hours of full sunlight every day for over a year. Samples checked against other samples not exposed to direct or indirect sunlight (in box). Also; results of white pigmented epoxy and polyester boards exposed regularly to sunlight over 10 or more years.

Results

40:1 (2.5%) - Sample changed from bright glossy white to flat antique white in one year.

20:1 (5%) - Sample changed form bright glossy white to flat antique white in one year.

Nu Finish car polish - Sample remained bright white and glossy for 6 months. After 6 months the sample color began to change towards antique white. After one year with no recoat, sample is slightly whiter than 40:1 and 20:1 samples. Apparently the Nu Finish washed off in the rain.

Two pigmented epoxy surfboards exposed to full sunlight about 6 hours a week for over 10 years with no extra ultra violet protection (epoxy used has u.v. stabilizer in it) - boards are now antique flat white but less discolored than samples above.

Two epoxy surfboards with a Silmar 249 polyester hotcoat and a Silmar 249 polyester gloss coat, exposed to full sunlight about 4 hours per month for over 10 years - boards are still bright white and glossy.

Two epoxy surfboards with pigmented hotcoat at 10:1 (10%) with Nu Finish applied each six months exposed to full sunlight about 6 hours per week for over a year. Bright white, non textured, Ethylene Vinyl Acetate (EVA traction surface) applied to top and rails. Result: Bottom surface which is coated with Nu Finish is still bright white, and glossy. The EVA is still bright white.

Numerous clear 100% epoxy surfboards (no other resin or covering added) used randomly (a few for over two thousand hours in the water) - The foam used was baby blue, so the new clear boards were baby blue. The resins yellowed. In two years the boards appeared blue green. In four years, yellow green. In ten years, yellow green beige. Resins used: RR2000, SS2000, and Klear Kote - no significant difference in u.v. resistance between the three epoxies.

Conclusion

White color is the best way to reduce heat damage in surfboards.
There is little advantage in a 20:1 pigment ratio over a 40:1 pigment ratio in epoxy. Both will degrade in color and neither is dense enough to allow one coat coverage. Please use 20:1 ratio pure epoxy pigment in epoxy resin, and use two coats. For one coat coverage on a hot coat use 10:1 pure epoxy pigment in epoxy resin. This will give reasonably solid color if Uscomposites Kleer Kote resin is used (very thick) - other popular surfboard epoxies will not give solid cover in one coat.

Polyester resin (Silmar 249) has excellent u.v. resistance (much better than any epoxy, despite what you may have read on the Internet). Add polyester pigment at no more than 3% ratio (33:1). A 3% ratio will not give one coat coverage, and it will cause the resin to not level properly. Please use 2% ratio, and use 2 coats. Nu Finish is excellent as a u.v. blocker over epoxy, and creates a deep gloss finish It is cheap, and easy to apply.
Although Uscomposites Klear Kote is technically not meant to be used as a laminating resin, it works well if you are not making a light production type surfboard. Although it can be fairly argued that other resins are better suited to surfboard building, a number of factors make it worth considering: 1. It is about half the cost of most popular surfboard epoxies. 2. It is 100% solids (no solvent, or cheap additives). 3. It is very clear, and glossy, with good u.v. stability. 4. It levels great, and seems to never fish eye, or do anything else strange, no matter what temperature or what humidity. 5. It seems similar in strength to the more expensive epoxies (this may be because we are using slightly thicker coats).

Test your pigment in your resin on scrap foam with rails similar to your surfboard. Make sure to observe how it thins on the rails - a coat which is solid color on the flats will often need recoatng because the resin thins as it runs off the rails.
White color is the best way to reduce heat damage in surfboards, and it covers mistakes.

Questions And Answers:

1. Question: Why not paint the blank, as production shops do?
Answer: Because this weakens the bond between the cloth and the foam.
2. Question: Why only white?
Answer: On a 90 degree day a white board will be 90 degrees, a blue board will be about 120 degrees, a black board will be about 140 degrees (so hot you can not touch it).
3. Question; Why not pigment the laminating resin and leave the hot coat and gloss coat clear.
Answer: Pigment weakens the lamination and weakens the bond. Pigment also weakens the hot coat and gloss coat, but most of a boards strength is in the laminated cloth. Also; the pigment helps reduce u.v. yellowing.
4. Question: Why use white 2mm EVA?
Answer: EVA creates a a slip resistant, comfortable, safe, and very damage resistant surfboard. 2mm EVA comes in white (10 colors), from Canalrubber.com For $20. plus shipping the entire top and rails of a longboard can be covered. A board made as recommended on this site and covered with EVA on the rails can be dropped from head high on to concrete, on to the rails, with no apparent damage.

 

BUILDING INSTRUCTIONS FOR SURFBOARD/PADDLEBOARD WITH WHITE EVA ON TOP AND RAILS, AND SOLID WHITE PIGMENT ON BOTTOM.

1. Build board, shaping and laminating according to instructions on this site, then follow the numbers below.
2. Sand the lamination especially thoroughly, especially the lap lines.
3. Turn board top up and lay two, 2mm EVA sheets over the entire surface. These sheets are 6'x 3'x 1/16". Cut the EVA the same way you cut the fiberglass cloth, except with slightly more overhang (at least 1" overhang). This can be sloppy, as it will be cut again. Tape the EVA with masking tape strips about every 6", (more at nose and tail) stretching the EVA slightly, and making it conform to the curve of the rails.
4. Make a lap line marking tool. Cut a 5"x 2"x 1" piece of foam. Cut a 10"x 2"x 1" piece of foam. Tape the foam pieces together with the 2" sides together, and the tops even. Tape a pencil so the lead protrudes past the bottom edge of the short foam piece. Tape a level with the horizontal bubble near foam tops (opposite pencil).
5. Flip board bottom up.
6.. With lap line marker, mark pencil line around entire circumference of partially taped EVA, keeping the level bubble between the lines.
7. Remove tape and cut along pencil line with scissors - you may need to connect the gaps where the tape was, with a pencil line before cutting.
8. With board bottom up mark pencil line with lap line marker around entire circumference of bottom laminate (where EVA will line up).
9. Flip board top up.
10. Place cut EVA so it is lined up perfectly with #8 pencil lines. Pencil mark center of EVA to line up with center of board, at forward side and rearward side of each piece of EVA (four marks). The two EVA pieces will now have marks that line up.
11. Cut V's - one at nose tip, two at middle of nose curve, and probably two at tail corners - start small and enlarge it to close exactly when taped in place.
12. Hotcoat as in instructions on this site, except do not tape at mid rail. Do not use any tape until the EVA is applied over the hotcoat resin. Apply the resin all the way to the pencil line on the board bottom (where EVA will line up).
13. Lay EVA pieces to line up at board center with pencil marks.
14. Using a plastic squeegee, force EVA to adhere to the hotcoat and work out any entrapped air under the EVA. Make sure it is perfectly lined up with pencil marks when done.
15. Put 3 or more bricks spaced evenly along the center of the EVA.
16. Use 2.83" (3") masking tape, 1.88" (2") masking tape, and 1" masking tape to tape EVA overhang to underside of rail. Use mostly 3" tape. Tear about 20 pieces of tape about 6" long and tape EVA edge to board at about 6" intervals, all around the circumference. Alternate sides every few pieces of tape, or you will pull the EVA off center. Tape the 6" gap areas with 3" tape. Make sure the EVA conforms exactly as possible to the rails and curves of the nose and tail. In places this can only be accomplished by stretching the EVA, and taping it numerous times to hold the stretch. You may have to untape and tape again to get the wrinkles out.
17. When resin is as hard rubber, remove the tape. Some tape may not come off - you can sand it off (off the hard laminate).
18. With #50 sandpaper sand the edge of the EVA. Do not sand it flush with the hard laminate - you will not get it even, and it is likely to tear this way if anything catches on the thin edge. Sand about half the thickness down, so at least 1/32 of EVA is left at the edge.
19. Carefully, by hand, with #20 and #50 sandpaper, sand the hardened resin which has squeezed out along the EVA line, and lightly sand the entire exposed laminate.
20. Tape along the sanded edge of EVA, all around the circumference - with tape on EVA side.
21. Level racks and board.
22. Pour bottom hotcoat resin and hardener in container and add 10% pure epoxy white pigment. Add about 25% more total resin than on normal hotcoat as this should result in one coat coverage.
23. Mix and apply bottom hotcoat, being careful not to smear resin on the EVA. Brush the resin carefully around the tape line. The resin should be thick against the EVA (resin should be touching the EVA) - this will even the edge, and ensure it will not tear away.
24. After hardened, pull tape, apply Nu Finish, and hand buff.

 

ADDITIVES

Test of the following additives to epoxy resin:  3M bubbles (microspheres), milled fibers, Cabosil (fumed silica), added to Us composites Kleer Kote Epoxy at  2 to 1 ratio by volume (2 epoxy/1 additive).  White, pure epoxy pigment added at 10% ratio (10 epoxy/1 pigment) prior to adding other additives.  Pigmented epoxy was brushed on the flats and the rails with and without additives.  Plain weave and twill weave cloth tested with all additives.

Results:

1. Epoxy and pigment alone.   Pigmented epoxy with no other additives was not sufficient for one coat (hot coat only) coverage on laminated plain weave cloth.  Pin holes noted. Uneven color noted on the rails.  Twill weave cloth gave very even, one coat coverage on the flats, with no pin holes, and less resin was needed, but the rails were still uneven.

2.  Pigmented epoxy with 3M bubbles, milled fibers, or cabosil showed even, glossy, one coat coverage on flats.

3.  Pigmented epoxy with 3M bubbles, or milled fibers showed slightly uneven coverage on rails with many drips and runs.  cabosil showed even coverage on rails with no drips or runs.

Conclusion:  For white, one coat (hot coat only) coverage over laminated plain weave, or twill weave use 10% pure epoxy pigment plus 50% cabosil (2 epoxy/1cabosil by volume).

Note:  Although not mentioned in the glue section above, cabosil gave the best adhesion when compared to 3M bubbles, milled fibers, Gorilla Glue, spray foam, and plain epoxy - it is almost impossible to remove excess epoxy/cabosil from a mixing container, while the others can usually be pried out.  cabosil will darken white pigmented epoxy slightly, so it should be used in the entire coat (top and bottom), not just in spots.  Cabosil is surprisingly resistant to sanding (more than twice as hard to sand), and should be avoided for applications such as foam bonding where it might squeeze out at the joint and need to be sanded - 3M bubbles are better for this.  If you do not want to use cabosil, but want a lightweight, mostly one coat, white coverage, do this:  mix about 5 oz. epoxy and hardener with 10% epoxy pigment.  Brush lightly (thin coat) on the rails, and just beyond the rails, a few inches, towards the flats.  After the rail coat has hardened, and been sanded, finish as with a normal pigmented hot coat. 

 

EXPERIMENT WITH HOLLOW CARBON FIBER SURFBOARD.

The purpose of this experiment was to invent a practical, method for a home builder to make a hollow surfboard molded from an existing, finished surfboard.  The advantage is the elimination of foam shaping, and the likelihood of a lighter board.  The project was a comedy of errors, with new techniques needed for almost every step (some of it was filmed, and will be uploaded later). Below are the steps, with emphasis on new techniques:


1.  A finished, existing surfboard was covered in Vaseline (water wash off mold release agents were tried, but did not release properly on models). 
2.  The vaselined board was laminated as if it was a foam blank, with 20oz carbon fiber cloth top and bottom, and a 20oz carbon deck patch all saturated with epoxy resin.  When wrapping the rail cloth, it was found the cloth would simply sag off the Vaseline.  It was necessary to wait til the resin was gelled to a soft rubber consistency (1st side only - 2nd side is wrapped over new carbon).  Wax paper was pulled the length of the rail, and the rail was wrapped by bare hands sliding around the wax paper - the semi-hardened cloth then held its curved shape against the  Vaseline.
3. Using a razor blade knife when the cloth was gelled, the cloth was cut down the stringer line on both sides.  When hard, a chisel was run down both sides of the cut line and an aluminum T square was worked from cut line towards the rail, tapping lightly with a hammer til the suction on the rails was released, and the the molded pieces came loose - this was a wonderful moment, as a nearly perfect copy of the original was made, and it seemed we had created a worthwhile technique.
4.  Vaseline was removed using first mineral spirits, followed by Dawn dishwashing detergent.
5.  The fin box hole (where the fin base protruded through the shell) was routed, and fin box shaped to fit interior curve of shell (same for both halves).  Fin boxes (twin fin setup) glued to interior of shells using a very thick coat of epoxy and 1/4" cut fiberglass fibers (about 1 to 1 ratio by volume).
6.  One of the shell halves was laid, open edge down, on 3/4" thick, 60 psi XPS foam.  The outline of the shell half was marked on the foam sheet.  This marked foam was cut to make a center stringer, and two more, slightly shorter stringers were made using the same method. Cut the stringers in half (lengthwise), otherwise they are too difficult to fit - these halves are epoxied together on the final fiting.
7. After some shaping adjustments, the two extra stringers were epoxied 4" from the center stringer, and the center stringer was epoxied with one half of its width (3/8") protruding from one shell half.  After the stringer epoxy hardened, the protruding stringer was epoxied, and the two halves were slid together, (a chisel helps) and checked for bi-lateral level.
8.  The center line of the now one piece board was sanded, and a 1" wide, 20oz carbon fiber strip was laminated over the center line (top and bottom).
9.  The leash plug, a Gore Tex vent plug (center top), and a drain plug (rear end) were routed, and installed.
10.  The entire board was rough sanded.
11.  1/8" undulations in shell, thick lap line, and other unevenness filled with epoxy, cabosil, (2 epoxy/1 cabosil) and 10% pure epoxy pigment.
12.  Sand.
13.  Repeat #10 - 11. 
14.  Thick hot coat using 2 epoxy/1 cabosil mix, with 10% epoxy pigment.



WHAT WE WOULD DO DIFFERENTLY IF BUILDING ANOTHER HOLLOW CARBON FIBER SURFBOARD


1.  Only clean Vaseline about 4" from center line.
2.  Use 1" - 1&1/2" thick foam (standard 2lb/cu.ft. polystyrene type) for stringers.
3.  Use 10oz carbon in place of the 20oz. 
4.  Fill unevenness one time with epoxy and cabosil as above, but finish with thick hot coat, and thick gloss coat
5.  Glass on fins.



TWO EXPERIMENTS WITH HOLLOW CARBON FIBER SURFBOARD FILLED WITH EXPANDING LIQUID POLYURETHANE FOAM


1. One shell half, as mentioned above, was filled with enough foam mix (must use mixing paddle on drill, and have helper) to fill about 1/4 of shell - the idea was to harden the rails, which were very rigid, and this would hold the shape on further pours.  The first batch of hardened foam looked perfect (no lumps in shell).  After the second and third pours, an unacceptable amount of unevenness was noted at each pour interface (where the different pours met) - 1/4" lumps.
2.  Shell half above cleaned of hardened foam, and re - filled with enough pour foam to fill entire shell.  A 3/4" foam stringer was taped to the center line, and removed as the foam approached the stringer.  At this point the shell was 9/10 full, and not noticeably distorted.  When the stringer was removed the shell started to bulge unacceptably.  The wet foam was quickly removed.



WHAT WE WOULD DO DIFFERENTLY IF BUILDING ANOTHER POUR FOAM IN SHELL SURFBOARD


1.  Fill entire shell half with one pour, with at least one foam stringer epoxied within each shell half.  This foam stringer would have more than half of its volume removed by drilling or cutting.  The stringer, will stabilize the shell, to keep it from bulging, and the holes will allow the expanding foam to escape.
2.  There would be no need to use expensive carbon cloth with 2lb pour foam.  The shell could be made with the same method as the carbon shell above, but with cheap E cloth, as in most surfboards.


Note:  The hollow carbon board is finished and has been ridden many times, by two people.  It is 5lbs lighter than the original.  It is stronger than it needs to be, and could be lighter.  Being lighter it is more maneuverable, but the maneuverability is beyond what we would have expected.  Since the front end is hollow, and has only one layer of cloth, it has a swing weight that is much less compared to the foam core original.  Also;  increased spring is noticed.  These characteristics make the board a joy to ride, and makes all the trouble we experienced worthwhile.

 

1LB. EPS CARBON

1 LB.  STRINGER - LESS EPS covered in  100% CARBON, EPOXY, AND EVA.
Emphasis will be on describing alternative building techniques not mentioned previously in book, or on the youtube video titled, How To Build Your First Surfboard - Alternative Building Methods.

SHAPING

1lb. EPS block foam used.  Hot wire used to cut rocker, outline, and rail curvature.  Even if a hot wire is commonly used for rocker only, we recommend using it for the outline and rail curvature.  More than 95% of people who cut their outline use a hand saw, after marking the outline on the blank from a template.  Notice:  neither the saw or the cut is ever checked for 90 degree accuracy, and to make up for errors the outline is always cut some distance outside the template line.  With a hot wire cutter made specifically to cut outlines, the cut is always exactly 90 degrees, and the cut is made exactly on the template.  This,  in conjunction with cutting the rail curve with a hot wire cutter,  creates a shape that is more accurate, and requires less labor and time.  See youtube video.
1 lb. EPS foam is shaped using techniques mentioned in book with the following exceptions.  It should not be necessary to do much shaping on the rocker, and outline, as these can be cut very close to the finished shape with the hot wire cutter.  We find a planer to be of no use when building with this method, in fact, a friend uses a modified hot wire cutter to cut rail bands, as would be done with a planer.   Most of the shaping will be on the nose rail and tail rail where the hot wire cutter did not totally cut the curvature.  Because you are using a foam with half the density of the foams mentioned in the shaping chapter, you will need about half the pressure you would use on the denser 2lb or 3lb foams.  I recommend using the same grits listed in SHAPING, and simply use less pressure, instead of using a higher grit number. Practice on scrap first.  Careful on the nose and tail tips (100 grit here) - you can break off a piece very easily.
I recommend finishing your blank very rough, #20 grit on flats, and 50 grit on rails (please read RESEARCH - bonding tests).  It is not necessary to spackle the blank, and evidence from my tests and at least one other builder indicate spackling causes an increase in delaminations when used on 1 lb. EPS.  The rough grit finish and lack of spackling greatly increase the bond.  We have had no delaminations using the rough grit no spackle method.

GLASSING

The blank, which is stringer less, and needs twice the support needed for a 2 lb foam blank, should have support every two feet, and have the thinner parts near the nose and tail ends supported every 6 inches.  Two racks will not suffice.   If you hot wire cut your blank, you should have  the nose rocker, and tail rocker cut into whatever foam you used to make your blank - use these sections, supported above a rack to support your nose and tail curves perfectly.  Do not skip this step, as the blank will be very flexible, and the cloth will ripple slightly as you apply pressure when laminating.  This rippling will cause problems later, when trying to get a flat, even finish - you will have small waves in your finish, which can only be removed by adding a lot of heavy resin.  If you did not hot wire cut,  build support under the last two feet of the nose and tail sections.

GLASSING BOTTOM

5.7 oz. twill carbon fiber is used for the bottom layer.  Use free lap method as in book.  Carbon is stiff, and, you may find the cloth will tend to straighten on the rail curve ( may separate from the foam).  If this happens, simply wait until the resin is rubbery (very sticky), then re-wrap it.  Re-wrap it using wax paper over the unwrapped section, and force it to wrap with your gloved hand on the waxed paper.  Use new waxed paper on each new area.  After doing this a few times, I have learned to wait until the resin is gelled before I wrap 20 oz. carbon rails.  The 5.7 oz. usually stays wrapped, but the 20oz on the top sometimes unwraps, and needs the wax paper treatment.

SANDING TOP LAP

Carbon is more than twice as hard to sand compared to E cloth.  I recommend covering the foam near the lap line with duct tape and use 50 grit on an oscillating sander if possible.  Do not hand sand carbon, as it will seem as if nothing is happening.  The fiber bundles in carbon twill are comparatively large and twill tends to fray more at the lap line - this causes more work to sand it smooth.   However;   twill requires less resin, and gives a better finish with a hot coat only finish.

GLASSING TOP

The 19.7 oz. carbon twill deck patch is stand alone - there is no cloth under it or over it, except where the 5.7oz under-laps for 1/2".  Many builders will think this is too much cloth, and others will not want to try an unfamiliar layup.   A friend has already tried double 5.7oz . and found it too flexible on the deck patch area (it dented immediately).  If you are determined to lay out the deck patch and cover it completely with 5.7oz., please use at least 16oz of carbon total on the deck patch area.    Remember:  the 19.7oz. may start to unwrap - use method above.

SANDING TOP

If you used the recommended stand alone 19.7oz deck patch, you will notice a ridge where the 5.7oz is under the 19.7oz.  Sand this with a disk sander (about 40 grit) until most of the lump (ridge) is gone (until the two cloth layers blend into each other - you will be sanding into the 19.7 oz. cloth, making it partially disappear where it overlays the 5.7oz. - do not sand the 5.7oz.   There will always be a slight height difference, but this is barely noticeable after the hot coat and EVA - you will likely be the only one who can tell it is there.   If you are skeptical of this alternative layup, please see RESEARCH.

SANDING BOTTOM LAP

Repeat of SANDING TOP LAP, except duct tape is on carbon cloth instead of foam.
SEE EVA IN RESEARCH CHAPTER - or do a very thick (use uscomposites kleer kote epoxy, and 20% more resin) hot coat with 10% pure epoxy, white pigment added.  You and your friends will love the stealthy black look, but do not leave a carbon board black if it will be used in over 90 degree temperatures -  it will become so hot it will be ruined.  I recommend white 2mm EVA over the entire top and rails, and white epoxy over the bottom, finished with NuFinish car polish.

 

 

 

 

 

 

 

 

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