I have several boards that have pressure dents in the bottom and of course a few dings and they just need to a little resurfacing or a few layers of glass with the surrounding surface area faired and blended nicely.
I find that sanding the areas with 120 very thoroughly and applying a coat of Resin Research epoxy with Additive “F” is invariably resulting in a full on fish-eyed mess. So my next process is to wipe the sanded area down with denatured alcohol and sand it a second time. It could be that my problem is caused by handling the board because I’m working with an old pair of well worn deer-skin leather gloves, No oil on them mind you. I know that touching board anywhere with my bare hands will result in that spot with fish-eyes. Anyway I’ll switch to rubber gloves but sanding and handling the board with the leather gives such good feel and control during the sanding process.
One other note worth point. I have glass several polyeurathane boards with R.R. epoxy and find that they are very sensitive to heat. By this I mean that even when they are post cured for a couple hours at 120 degrees over at Stretch’s factory, (R.R. is what he uses for all of his composite construction) I find that if the board is left in direct sun and allowed to heat up the foam will shrink and the epoxy will move with it and hold the shape that the foam has shrunken to; a most unfortunate circumstance I’m sure you’ll agree. As a result I’m very careful these days about transporting and storage of these sticks.
Finally I am stacking more and epoxy fin panels and using 6oz. E glass, 5.7oz, carbon fiber, bamboo and paulownia veneer in different combinations for fin panel composites with a very attractive variety in flex patters and memory speeds. Polyester is cheap and pretty but it won’t perform at the same level as epoxy will.
Foil patterns continue to be more refined as I learn the art.
I have several boards that have pressure dents in the bottom and of course a few dings and they just need to a little resurfacing or a few layers of glass with the surrounding surface area faired and blended nicely.
I find that sanding the areas with 120 very thoroughly and applying a coat of Resin Research epoxy with Additive “F” is invariably resulting in a full on fish-eyed mess. So my next process is to wipe the sanded area down with denatured alcohol and sand it a second time. It could be that my problem is caused by handling the board because I’m working with an old pair of well worn deer-skin leather gloves, No oil on them mind you. I know that touching board anywhere with my bare hands will result in that spot with fish-eyes. Anyway I’ll switch to rubber gloves but sanding and handling the board with the leather gives such good feel and control during the sanding process.
It’s always contamination that causes fish eyes no matter what resin you use.
One other note worth point. I have glass several polyeurathane boards with R.R. epoxy and find that they are very sensitive to heat. By this I mean that even when they are post cured for a couple hours at 120 degrees over at Stretch’s factory, (R.R. is what he uses for all of his composite construction) I find that if the board is left in direct sun and allowed to heat up the foam will shrink and the epoxy will move with it and hold the shape that the foam has shrunken to; a most unfortunate circumstance I’m sure you’ll agree. As a result I’m very careful these days about transporting and storage of these sticks.
Urethane foam doesn’t handle UV well at all. In fact most will deteriorate very rapidly and the shrinkage your seeing is from UV not heat. I’ve suggested for years that a UV absorber be used in the resin when using it on urethane and we have stocked that for over 20 years. No one ever bought it and anyone who used RR on urethane had similar results because of that omission. Our new product, Research CE resin, is urethane specific, contains UV absorber and optical brightners and gives all epoxy’s attributes on urethane foam. The biggest of these advantages is a 33% weight advantage over polyester laminates. What this means is a 6 oz laminate weighs the same as a 4 oz with poly. So let me know when your ready for a new board and you can try this sttuff out.
Finally I am stacking more and epoxy fin panels and using 6oz. E glass, 5.7oz, carbon fiber, bamboo and paulownia veneer in different combinations for fin panel composites with a very attractive variety in flex patters and memory speeds. Polyester is cheap and pretty but it won’t perform at the same level as epoxy will.
Don’t know if this is a help but I went through my own version of fish eye hell 2 years ago. Turned out that my oil-less compressor that I was using to blow the dust off with had silicone in the air. I used it for years without any problems and then the nightmare began.
You have to filter your air and watch your rags. Rags for board work need to be clean and used for nothing but boards. Car wax, WD-40, automotive work are a big no no around surfboards. Too many sources of contamination. Even a door knob can be touched after being contaminated with a bare hand that was dirty with a silicone spray.
My best fish eye story was getting anitperspirant falling out of my underarms and contaminating a board surface to be sprayed with 2-pac paint. Now no antiperspirant when working on boards. Better to be stinky then pissed off.
I’m just not seeing the fish eye problem others are. I use pretty much only the slow set. (I’m in Florida). My shop can not be that much cleaner than all ya’lls. My last couple of boards were fine on the hot coat. (I’m wearing deordorant, but not blowing off the dust. I use a big fat brush and go over it a couple of times.)
Stretch is using optical brightner now as are many others. UV absorber isn’t a nessesity with EPS. Took a long time to get that tested. With urethane you shopuld use absorber. I think with XPS as well.
Contamination for me was always brushes. We always use new brushes and never had a problem. Cleaned brushes always gave us inconsistant results.
Rich, email me after the hollidays and remind me and I’ll get you some additive.
Epoxy soaks into fabric better and more thouroughly because of surface energy which is the more important aspect of a resin and rather than viscosity. This provides for better and more thorough wetting. Epoxy has far greater surface energy which explains not only it’s better wetting charateristics but it’s better adhesion as well. This explains epoxy’s superoir charateristics in composites.
Read this:
Surface Energy (Surface Wetting Capability)
As previously mentioned, one of the important characterististics of a liquid penetrant material is its ability to freely wet the surface of the object being inspected. At the liquid-solid surface interface, if the molecules of the liquid have a stronger attraction to the molecules of the solid surface than to each other (the adhesive forces are stronger than the cohesive forces), wetting of the surface occurs. Alternately, if the liquid molecules are more strongly attracted to each other than the molecules of the solid surface (the cohesive forces are stronger than the adhesive forces), the liquid beads-up and does not wet the surface of the part.
One way to quantify a liquid’s surface wetting characteristics is to measure the contact angle of a drop of liquid placed on the surface of an object. The contact angle is the angle formed by the solid/liquid interface and the liquid/vapor interface measured from the side of the liquid. (See the figure below.) Liquids wet surfaces when the contact angle is less than 90 degrees. For a penetrant material to be effective, the contact angle should be as small as possible. In fact, the contact angle for most liquid penetrants is very close to zero degrees.
Wetting ability of a liquid is a function of the surface energies of the solid-gas interface, the liquid-gas interface, and the solid-liquid interface. The surface energy across an interface or the surface tension at the interface is a measure of the energy required to form a unit area of new surface at the interface. The intermolecular bonds or cohesive forces between the molecules of a liquid cause surface tension. When the liquid encounters another substance, there is usually an attraction between the two materials. The adhesive forces between the liquid and the second substance will compete against the cohesive forces of the liquid. Liquids with weak cohesive bonds and a strong attraction to another material (or the desire to create adhesive bonds) will tend to spread over the material. Liquids with strong cohesive bonds and weaker adhesive forces will tend to bead-up or form a droplet when in contact with another material.
it’s the exact reverse of how i want to try and have my bottom of the surfboard - hygrofobic
Have a question… or two…
check out the picture of this droplet on a lotus leave, i hope to create a flat to the touch surface, with microballoons and graphite powder mix to obtain something that should resemble this surface…
Did you ever try this stuff Greg? i am sure you did, what is the easiest way? just lengthwise sanding the bottom?
wrt to surface and form friction, Bert burger once replied to a post with a board with holes from top to bottom, and i am wondering what fins to put on. any ideas?
Lotus effect:
And the powder:
423 Graphite Powder
423 Graphite Powder is a fine black powder that can be mixed with WEST SYSTEM epoxy to produce a low-friction exterior coating with increased scuff resistance and durability. Epoxy/graphite is commonly used as a bearing surface, and as a coating on rudders and centerboards, or on the bottoms of racing craft that are dry sailed. It does not provide antifouling qualities. The epoxy/graphite mixture can also be used in teak deck construction to simulate the look of traditional seams and to protect the epoxy from sunlight. Cures to a black color. Add to mixed resin/hardener at the rate of up to 10% by volume (approximately 5.7 oz. per B group).
I don’t think the resin continues it’s adhesive role once hardened, do you? Also there has never been proof that graphite powder in the resin added any anti-friction role. If it did, every race boat made would be black.
Here’s another description of high energy surface versus low energy surface, along with a link to the source.
“Adhesion is the result of the molecular attraction between unlike materials, similar to a magnetic force. The strength of attraction is determined by the surface energy of the material. The higher the surface energy, the greater the molecular attraction. The lower the surface energy, the weaker the attractive forces. Greater molecular attraction results in increased interfacial contact between the adhesive and the substrate. In other words, on a high surface energy material (substrate) the adhesive can flow or “wet out” to assure a stronger bond.”
I don’t think the resin continues it’s adhesive role once hardened, do you? Also there has never been proof that graphite powder in the resin added any anti-friction role. If it did, every race boat made would be black.
Hi Greg, Spindler too!
No i dont think so either, that is why i thought of hollow micro balloons and this graphite powder.
How do you get your high speed finish on you own boards, just a directional finish sanding?
At issue is the interface between water and board…
Things you want are laminar flow, thin boundary layer, and no boundary layer separation. Finish sanding in the direction of flow helps in all three areas.
The short reason is a sanded surface creates a high energy surface, which makes your board hydrophilic. Meaning it likes water. The water flows out evenly over the surface which makes for a higher contact angle, (90degree bad closer to 180degree is good) which decreases the chance of developing turbulent flow, while simultaneously improving laminar flow characteristics. Furthermore, this results in both a thinner boundary layer and less chance of boundary layer separation (water flow separating from board surface). The link below gives you the basic science.
Well I decided to break one of Greg’s rules and incorporate acetone in the the prep schedule for a R.R. finish coat.
I shaped an 8’1" x 21" six shooter a couple of years ago out of Clark foam and the board shrunk a little around the stringer. I wanted to bring the bottom back to it’s original contour so. I did a little glass work along the stringer. The thing looked all patchy so I figured a resin swirl hot coat would be the ticket. First try resulted in enough fish eyes that it was cosmetically unacceptable but it did fair out some sanding imperfections. I only need 3 oz of resin with additve “F” to do the whole board so a second shot was on. I sanded it with 100 to get the little highs and lows out and did a finish sand with 150. I touched the rails with 220 to facilitate a clean tape line. After I blew all the dust off. I broke the rules and did an acetone wipe with a saturated paper towel. I followed immediately with a denatured alcohol wipe. I then shot the finish coat. I just pulled the tape. WALA! No fish eyes! The deck is still yellow. Now the bottom is deep blue/green resin swirl. I’m look forward to the polishing process.
