Swaylock’s™ Surfboard Design Forum

SURFBOARD BUILDING HINTS COLLECTED FROM SWAYLOCKS – VOL. 2

CONTENTS: Making wooden fins; More fin making hints; Types of wood to use for tailblocks and fins; How to make fiberglass fins; Colored fins; How to install fin boxes and Ofishl fin boxes; Gluing stringers; Sizes and types of wood for stringers; Buying balsa, How to make a tailblock; Using UV-cure resins (Suncure); Making fin panels; How to do resin pinlines; sanding gloss coats

HOW DO I MAKE WOODEN FINS ?
(Paul Jensen) My most recent fins are 1+1/8" at the base...1/8" glass core + 1/2" ply x 2 sides...I do remove wood at the part that goes in the box, and replace it with glass & epoxy... I used 4 layers of 6oz.cloth with tinted resin at the core. The plywood is 1/2" 9ply baltic birch...After foiling and fine sanding, I put 2 layers of 6 oz. on each outer side...Lay one layer of glass at a time...I brush resin on with a cheap bristle brush... lay on the glass... brush on more resin, smoothing and evening as I go...Lay on more glass...Etc...The glass is there to keep the wood protected, I'm not really looking at it for strength...After sanding again, one more layer of glass each side, sand, hot coat, final sand...Spray with Rustoleum/Krylon gloss clear...Drill for fin screw & slot pin ( I use a stainless steel screw cut off & epoxied )...
MORE WOOD FIN QUESTIONS AND ANSWERS FROM PAUL JENSEN:
What type of wood do you use for the core?

9 ply 1/2" baltic birch plywood or solid wood...Plywood for easy foiling...solid for aesthetic's...

What width do you start with and how many layers of glass is standard?

If it's a plywood fin, I'll put an 1/8" fiberglass core in between the 1/2" sides...After the glass sets up, cut out the fin template, rough sand the profile, foil with a 4" grinder with a 36 grit disc, hand sand to 100 grit...Glass each side with 2 layers of 6 oz....If the fin is thicker than 3/8" I put the pin at the rear edge of the fin...The tab that has the screw hole is solid glass roving that I extend into the base of the fin (the part that is inside the fin box)...That's a simplified description of how I make some of my fins...

If you are making a fin composed of several woods what process do you use to bind the woods together?

Elmers yellow glue...If the fin has curves wood panels use curved glue...(just kidding)...

Do you glue blocks of wood together and then bandsaw off many thin layers of the composite?

I'll cut tapered 3/4' thick redwood and Alaskan cedar wedges on my table saw, glue them together on a scrap piece of plwood (with paper on the plywood to prevent the fin panel being glued to the plywood)...After the panel is glued and dried, I'll scape the excess glue, the belt sand it flat...Then I cut the fin profile from the panel...To get the right thickness I cut the fin vertically on my table saw (THIS IS VERY DANGEROUS, IF YOU ARE NOT SURE WHAT YOU ARE DOING, DON'T !!!)If I'm making a "rising sun" fin, I like to put a disc of redwood at the "heart of the sun"...I'll use a hole saw to drill it from some scrap redwood, then carefully trace it on the fin, the cut it out with a scroll saw, then glue it...Foiling and glassing is similar to what I described above...

What size pin do you use to hold in the front of the fin in the box and where do you get the hardware to screw in the the backside of the fins?
I use 8/32 stainless steel screws for pins...Drill a tight pilot hole,screw in the screw, cut off the head, file away roughness...
How do you ensure that wood is centered on the middle core? Do you sandwich the core prior to the resin kicking or do you allow to kick, sand, apply etc...?
I cut out an oversize fin template from the glass panel and laminate to both pieces of wood with laminating resin (epoxy or urethane glue would probably work) - cut the wood to the fin template and align the edges as best you can - it's still pretty rough at this point anyway. I use a cinder block or something to weight it down as it cures. Recutting on a bandsaw or using a surform works pretty good for cleaning up the edges.
Is the wood and the core the same size (thus ensuring uniformity)? What thickness is the wood that you use, and what kind of wood have you found to give an aesthetically pleasing appearance?
I don't really use a formula - after foiling, the glass panel leaves a nice edge around the wood. Pigment can be added to the resin before you lay up the glass panel. I think a contrast between the wood and border looks nice. I try and avoid a perfectly vertical grain. I think it looks better angled back. Its also pretty easy to glue contrasting wood strips for stripes, etc. Thickness and wood types are really up to you. For a box fin with the screw and roll pin holes, wood is pretty vulnerable to moisture penetration. In that case, I just leave out wood from those areas and add extra cloth. Make sure you don't leave unsealed edges as they will surely suck water.
The stainless hardware can be found through Larry Block Enterprises- Chatsworth, CA. (805)583-0057.(3/4" stainless screw with 10/32" thread size and the backing plate). Others have suggested using a nylon screw which is a good idea, hopefully the softer plastic will shear off before the fin box fractures on severe impact. The lateral pin is called a stainless roll pin, easy to find at a marine hardware store, 1/8" or so. Take a sample with you.

WHAT TYPES OF WOOD MAKE GOOD FINS OR TAIL BLOCKS?
(Deeb): Whatever wood you use, the resin will make it appear slightly richer...or at least a little bit darker. To get an idea of what it will look like when laminated, just lick your finger and wipe it on the wood. There's no need to stain when you find a good wood. Just be sure you use a non-oily hardwood. One of my favorites is Walnut. When glued together with a lighter-colored hardwood, such as white or red Oak, it provides a great contrast, which in itself makes the natural colors appear richer. If you need help picking out wood, there's a great book to check out at Borders or Barnes & Noble, it's The Encyclopedia of Wood. It's got great pictures that show the color and texture of most woods around the world. Once you've got your wood choices narrowed down, go to a lumber yard and pick through their junk pile. You can also ask if they've seen any of your favorite wood laying around. You can find some great specimens for free! Also, since it is so strong a wood, they use Oak a lot for the braces on their pallets and usually don't mind getting rid of one.
HOW DO I MAKE FIBERGLASS FINS?
(Jim Phillips): You need a smooth flat surface to work on. If you can find a piece of used plate glass or a formica'd surface. You can used car wax to prep it with. apply one coat, buff with a rag then repeat. Have all of your cloth ready, don't fire off the batch too fast, because laying up a fin sheet takes a while and the resin will go off on you in the bucket sooner than on the table. Wet out the table and put down one layer, work the air out and rewet. Next put down two layers, squeegee those out well, looking for air and repeat the process until done. When the sheet has set, mix up a waxed hot coat and seal the exposed surface. When the sheet is thoroughly cured, start a wedge of wood or plastic under one corner and slowly free the glass sheet from the lay up table. You will feel the hairs stand up on your arms while doing this as it creates a static charge as the two separate. Using a scratch awl or tempered sheet rock screw you can etch the outline of your fin template onto the sheet. When cutting them out it is best to leave the extra scrap on the fin base, this gives you some room to clamp to while foiling. After the fin has been foiled, cut off the remaining part on the base. You now have your set of fins, for longboard center fins the process is the same, just use 30 layers of cloth. The fins are easy to make. I used to save all my trimmings and sort them to size. It takes about 14-16 layers, it doesn't matter what cloth you use. They can be cut out with a sabre-saw and foiled with any sander. The foiling is the itchy job though.
(Herb Spitzer): A couple layers at a time if this is new to you. Stick with white opaque it cleans up the best, and go to a hardware store and buy a good dust mask, nice fitting thin rubber gloves, and a paper paint suit with a hood. The gear I have described will help in the foiling phase(keep you from itching)+you can use it to lam with(keeps the resin off your skin/clothes).You need a respirator, and a pair of rubber boot wouldn't hurt either. p.s. make sure you get all the air out of the lam that you can!
(Jim Phillips): What Herb left out is, DON'T do this in the garage, patio, mom's living room or anywhere that PERMANENT reminders of the attempt will remain. You need a large piece of cardboard or tarpaper to work over. Resin has a way of finding the only uncovered piece of real estate. If you wear anything that is not already ruined, it will be.
(Tom): Cut the glass in big squares. If you can do it, make them about 24"x24". that way you can get more than 1 fin out of it for all the hassle!! As I believe Jim said, a couple layers at a time . This is so you can keep quality control as far as watching for air and stuff. Even though you're laying up a couple layers at a time, you want to do ALL the layers with the same batch of resin, this will negate any chance of layers not bonding together properly. Multi color fin layups are done with a multiple lamination process with a hot coat between the colors but that's a whole 'nother story! Anyway, yes you can make 1 fin at a time, just make the panel large enough so the entire fin will be the same thickness when you cut it out; sometimes the edges of the panel taper down because of squeegeing.
WHAT ABOUT COLORED FINS?
(Herb): Hotcoat between colors. The reason you hotcoat between color lams is so the colors remain even during & after foiling. You must sand the hot coat thoroughly before lamming the next color.
P.s. you can also use color hotcoats between lams too!
HOW DO I INSTALL FIN BOXES?
(Tom Sterne):
1. Trace the box where you want it, a bit oversize for resin and cloth to set it in place.
2. Measure the blank thickness at the back of the box tracing then measure it again! Going through to the deck can get ugly. You will use a router with a straight bit to cut the hole. Most people like to use a plunge router to make shorter work of cutting the stringer. I make do without and just use the straight bit edges to shave away at the stringer.
3. A template can be very helpful too. Easy to make, I'm sure there are some archived hints on Swaylock's to help you here. Wood, plastic or aluminum can be used.
4. Allow for the tail rocker when you are planning your depth of cut for the box and make room for the resin/chopped cloth or cloth strips you will use to bond it in the routed slot.
5. Best way to install is by laminating over the box either by installing before lamination of the board (this is how O'Fishl box goes in) or before hotcoat you set the Fins Unlimited box and cap with cloth patch then hotcoat. Cover the F/U slot well to keep out the resin.
HOW DO I INSTALL O’FISHL FIN BOXES ?
O’Fishl Boxes: I have used only O'fishl boxes as they are to be glassed in... better strength. With low volume, I haven't been compelled to use a router and template. I mark the box on the blank and tape around the mark. Then I cut the box open and install a fin in it. Then I tape all the parts where the glue shouldn't go. I use a Dremel tool and carefully freehand cut the box opening. I create little voids up and back on either side of the stringer for the glue to grab the stringer. For cutting the stringer, next time I plan to drill it with a bit as wide as the stringer. I'll put a tape mark on a bit to stop at 1" deep. I'll drill every 1/2" or so, then break out the remaining stringer pieces. Then I'll clean it up with the Dremel tool. For glue, I mix resin with Diatomaceous Earth (DE) from the pool store. DE is tiny glass shards. I coat box and hole with glue. I pour plenty of glue in the bottom of the hole, then set the box in it. I sight in the box to the stringer for direction straightness. I sight in the fin with the blank entry area for squareness. I check back periodically while the glue dries. For squareness, I believe the eye is more accurate than any tool I can use. Besides, if I can't see an error then there isn't one... Right? My method works, although I'm sure it's too labor intensive for production work.

[Herb].Here's a tip I learned from Mel,if you are putting in the boxes on top of the glass, rather than before lamination:sink the ofishl boxes down about 1/16"-1/8" below the surface of the glassjob,and put a patch over the box when glueing them in. Also make sure you fill them in with enough resin to top off the recessed box/hole back up to level. This way the fins will seat properly in the box when the board's finished,and you will have a strong bond.


HOW ARE STRINGERS GLUED?
(Jim Phillips): I glue at least 30 sets of stringers a month, with anything from bass, Sitka spruce, Redwood, old and new growth, western cedar, Port Ordford cedar, balsa and agave. Wood to wood, I use a good grade of carpenters glue or the polyurethane moisture activated glue. On wood to foam, I use polyester resin, epoxy or urethane glue. The polyesters I use have been let sit so that the majority of styrene is evaporated out. This makes them thicker and don't run out during clamping.
WHAT KIND OF STRINGER CONFIGURATIONS CAN BE USED?
2" Balsa
1" + 2x1/12" Cedar Balsa
2" + 2x1/12" Cedar Balsa T-Band
3/4" + 2x1/12" Cedar Balsa T-Band
1/2" Balsa T-Band
1/4" Bass
1/8" Bass
1/8" + 2x1/8" (Double) Bass
2x1/8" (1/2" Apart) Bass
2x3/16" (1/2" Apart) Bass
3/16" Bass
3/16" + 2x1/8" (Double) Bass
3/8" Bass
2x1/12" Bass T-Band
2x1/8" Bass T-Band
2x3/32" Bass T-Band
3x1/8" Bass T-Band
1/8" + 2x1/8" Cedar
2x1/8" Cedar
3/16" + 2x1/8" Cedar
3/16" Spruce
3/8" Spruce
HOW MUCH DOES IT COST TO BUY BALSA?
Clear # 1 balsa from Frost Hardwood Lumber is just under $4.00 ft.
All balsa wood is 3-1/4" in the direction of the natural rocker. The width varies anywhere from 1-1/2" to 8". Lengths are from 8' to 12'.
HOW CAN I MAKE WOOD TAIL BLOCKS?
(Jim Phillips): NO teak, No polyester resin. I use 5 minute epoxy, band saw the block to the shape of the tail or nose. Apply only a minimal amt. of epoxy, I hate the stuff oozing out all over the place. Tape in place. When set, remove tape and mask off with 3/4" tape leaving about an 1/8" gap between the block and the foam. I stagger 2 more layers of tape, this acts like a sanding shield. Put on an additional piece of 2" tape. This will give you about 4" to work on without marring the foam. I use my sander on low speed with #50 grit paper and work it aggressively. You can apply a great deal of pressure on the tape before the sandpaper will start to cut into it. After tuning it top and bottom with the sander I use a sanding block to finish, running with the grain only. On glass tail blocks this does not apply. Pull the tapes when satisfied and lightly sponge screen.
P.S I have seen some terrible tail blocks that looked great when the board was done.
(Lance): I don't know how the pro's do it, but I've had really beautiful results with the following methods. First of all I would advise against using teak as it is a very oily wood and resin will not adhere well. Avoid any resinous wood (I've seen micro-delaminations on brand new boards @ redwood blocks). Basswood, spruce and mahogany are good choices and contrast well. My method is to saw the shaped blank plumb and square with a backsaw (or a razor-saw)and adjust very slightly with a sanding block, if needed (it helps if you try to imagine you are creating the slightest concave from rail-to-rail). Mate up the block so that there is little or no gap between the block and the foam. Trace the circumference of the foam around the block, plus about 1/8". Sketch-in the plan shape of the tail-block plus about 1/8". Bandsaw or otherwise shape the block to the traced section and plan penciled lines. You should now have a rough shape of the intended tail-block. Bond the tail-block to the foam with laminating resin with a little cabosil mixed in, to the thickness of mayonnaise. Tape the block in place while the resin kicks. Get yourself a Stanley block-plane (Tail-block Plane?)and make the plane iron (blade)razor-sharp. If it will not shave hair off of your arm it's not sharp enough! Taking smooth and even strokes, shape the block to the final configuration. support the block with your free hand while planing and always try to plane "downhill" to avoid tearing the grain. You may want to protect the foam with masking tape if you're scared of dings or scratches, but I find it's not really necessary. Shape it 90% with the plane (sound familiar?)and touch-up with sandpaper. Blow the dust out of the foam with compressed air and stand back and admire your beautiful artwork. I glass the block just like a normal tail. If you think the wood may have oil or resin, wipe it down with acetone prior to glassing so that the resin will bond. This may also prevent minute bubbles that form as wood oils get hot as the resin kicks. I find the shaping of tail blocks to be really pleasurable (about an hour)and they really set-off a board's looks.
TELL ME ABOUT ULTRAVIOLET (UV) CURE RESIN [SUNCURE]
(Tom Sterne): I've only been using it just short of a year now. Clear lams seem to stay whiter longer, no structural tradeoffs that I can see. For the homebuilt board I can't find any fault with it. Fewer fumes, much less concern over temperature ranges and less waste. You can do tints but not opaques, use it for lams, hotcoat and even gloss. I don't know why you couldn't use it on Volan cloth just as easily, maybe better given all the time you need to work with the lamination. I've only mixed my own from SunCure powder mixed with Silmar resin, so no comment on premixed or other systems.
(Kokua Fiberglass): I've also used sun cure resin for about a year and I love it. Make sure there is no sun light getting into the shop area because it doesn't need direct sun to kick off. We get quite a bit of rain here on Kauai and there are times I've put a fresh lammed board under a canopy to kick, it takes a while longer to kick but it works, UV rays are bouncing all over the atmosphere . I use the premix from Fiberglass Hawaii, Costs about $15.00 more for 5 gals but you're not buying catalyst and what you don't use can be put back in the container to be used later. You can even use it with catalyst like conventional resin if you like.If you use it for hot coats you have to double the amount of surfacing agent and let the board sit( so the wax can come to the surface)for about 10 minutes before putting it in the sun. I personally use it with catalyst for hot coats, after it goes off I then put it in the sun to get a quick cure.
http://www.suncure.com/UVC2000usersguide.htm
CAN I MAKE FIN PANELS WITH SUNCURE RESIN?
(Tom Sterne): I use a 3/4" piece of plywood as a work surface, cover it with wax paper, pieced together with masking tape works fine. Decide on your dimensions, I use 15" x 24" , it works with 30" cloth well. Cut your cloth up and stack it in sheets of 5 layers. I made my last ones for FCS boxes so your layer count will vary with the boxes you are using. I believe 30 layers of 6 oz. cloth works out to proper fit for Fins Unlimited type long box. FCS- 25 layers, and I used every bit of 56 oz. of suncure UV catalyzed resin which I tinted blue. Layup 5 layers at a time, working ALL the air out and really concentrate on wetting all the cloth out. Five more and so on until you finish. No reason to hurry if you have your lighting setup right. I walked it out into the sun (last one was a 40 degree day, try that with catalyst!) Within minutes it was curing to the point I could lift the panel up to cool it some. I was cutting fins within a couple of hours. I use straight lam resin, no wax solution and do the cutout and foiling like this. You can finish them with a brush job using a hotcoat mix also with UV if you want. Really check on the actual thickness you need for the box you are working with, regarding cloth layers. Oversize is better than undersize, it's easy to thin them down for a close fit in whatever box you are using them in. I believe Jim Phillips posted some good numbers in the archives now about Bahne's specs for layup of box fins. Hope that helps.

ANY TIPS FOR DOING RESIN PINLINES?
[R. Brucker] Resin pinlines..easy to do ...hard to explain. In a nutshell I would say try to use Reichold Resin. Silmar is too slow to jell. Shoot ‘em hot (ten minute gel). Use more pigment(common mistake).I actually thin the resin with styrene sometimes. The main thing to remember is to lay it on thick...and go around twice. In other words mix the batch ,paint on a layer count to 10 and go over it again, walk the brush strokes out just like a gloss. Pull the tape immediately after cleaning your brush (its not going to run).You can also pull the tape when it kicks and the wax has risen but that is
another deal......Important stuff: Use a round artists brush, mine has a long 8 inch handle, natural white bristles around 1/2" diameter. Flat brushes don't hold enough resin. Use good pigments, that stuff from the boat places in the little squeeze tubes are watered down. My pigments are about like peanut butter in thickness and you get them from the Board Suppliers (Fiberglass Florida etc.)
[Herb] I use sanding resin that I let sit around for a few days to let the styrene evaporate. I never had much luck with thinning my pinline resin, even though most do it that way. I like to use a special stash of boat lam, mixed with lots of surfacing agent (when you think there's too much, add more). Then let it sit around for a few, before using, especially on larger wishbones. [A wishbone is a really flared-tipped pinline.i.e; it's where the line is wider at the top point, then tapers down to a normal pinline thickness. E.g. thickest point is 4"(top) to thinnest point is 1/8"(bottom).]

ANY TRICKS FOR SANDING HOT/GLOSS COATS?

[Shine:] Generally, grits of 100 to 220 are run at about 5,000 rpms (hot coat). Be sure and get a "Power Pad - soft" --- its the best, accept no substitutions. 320 grits and higher (often used on gloss coats) are run at 2500 or less. High rpms with fine sandpaper generate a lot of heat -- keep it moving or you will get "burns" -- tan spots -- or worse. Use Silicone Carbide paper.
As for gloss coats: I sand them out with 320 grit and the power pad -- then, I move to 600 on a pad called a "Disket" which is stiffer and flatter and use it at real slow speed with some water on the board. Then go to 1000 wetsand and a hand sand -- polish with polishing compound (keep it out of the sun) polish off dry compound with wool bonnet. The look is totally liquid when done right. Practice on an old board or something else before taking your act live.