Joining EPS blocks to get a blank

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stoneburner's picture
Joined: 12/30/2007
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Swaylocks Surfboard Design Forum: thoughts & theories ... practical & theoretical

RAIL PROFILE http://bgboard.blogspot.com/2014/03/march-82014-afterr-seeing-recent.html

McDing's picture
Joined: 05/22/2004

Yes lots of info on this subject in the archives.   Glues, rockers, linear as opposed to glueing flat. Scarfing etc.   Do a little research in the archives it's all their.  But I will add that "Time is money".  When you consider the time and material cost., but especially the time;  A Marko Kiteboarding blank shipped UPS might be an alternative to consider.  Such a blank would be more suitable and easier to shape.  Construction grade foam and glue lines are dicey.  You could go to all that work and then knock a chunk out of your blank the size of a shoe while shaping.  PM Shark Country.  He has put a lot of blanks together.

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karolis's picture
Joined: 07/11/2022

Thank you for your answers. Eventually I managed to get a deal for half block of eps200 foam direct from the manufacturer and they agreed to slice it as needed. Feel free to delete this thread since apparently it was discussed before.

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McDing's picture
Joined: 05/22/2004

Would rather that you continued on and lets us know how it goes for you.  Progress etc.  Maybe a build thread.  Would really like to see how it goes for you and if you are able to use any info you pick up here on Swaylocks.

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karolis's picture
Joined: 07/11/2022

All right, I will post the progress here as soon as I have my first cut on the CNC. Right now it's just a pile of parts, too early to call it progress :)

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sharkcountry's picture
Joined: 03/25/2006

I haven't been building many boards lately, but I still make with boards from EPS coolers. I may be on the last one because the meds my wife gets shipped in coolers may stop coming because medicare won't allow that. I also used up all the larger block foam I had.

McDing is correct about the glue lines. They can tear out a chunk of foam. Sometimes I'll use a razor and carefully slice the glue out instead of trying to sand or use a planer. I get away with it because I cover the deck with thin balsa for extra strength against pressure dents. I think a CNC machine might be able to cut cleanly over a glue line, but I've never used a machine. The ones that have the big round blade instead of a router would be the best.

Here's the latest glue up I have. I only work on it when I'm in the right mood. Planning on a 7' egg, or a square tail. I need something that can paddle as well as a long board, but short enough to throw around like a short board.

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karolis's picture
Joined: 07/11/2022

Quite a few blocks there! Did you ever consider putting them together in a brick pattern (not sure about the right term for this in English) to get more strength?

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sharkcountry's picture
Joined: 03/25/2006

I glue up about 2 feet of the pieces then glue them to the center piece. I've found that having them this way is actually stronger because the glue lines are harder than foam. I cut outline a bit narrow then add a single perimeter piece to be able to make a clean rail. Lots of work to make a shaped blank, but I'm retired and we were getting these small coolers every 2 weeks. I take several months just to glue up the foam these days, and then wait until I get in the mood to shape. Then I have to be in the mood to glass and finish it. The last several have come out good and I'm happy with them. I only make boards for myself, so it doesn't matter what they are made from.

Here's what it should look like once it's shaped, and then finished with a balsa skin on the deck for extra strength.

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sharkcountry's picture
Joined: 03/25/2006

I did one with the foam running nose to tail, without the perimeter rail. It was a while ago and I can't remember exactly why, but I think I had issues along the rail where the pieces met and it found it easier to glue up the blocks the way I do now then shape the blank with the perimeter band. The wood inserts are to support the fin boxes.

I also had blocks of foam that were only 4' long and 11" wide, so I made a bunch of boards by joining rockered slices. I stagger the seams to added strength.

These are all just to have fun making strange boards. I have several slab cut stringered EPS blanks that are waiting. They'll be for the more traditional boards I have in mind.

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karolis's picture
Joined: 07/11/2022

So I promissed to post my first cut and here it is!

Assembling the CNC and the table took way longer than I thought but finally I have it (mostly) working. Yesterday I did the first test of cutting a block of foam - just a surfacing operation to calibrate the stock. The next step will be to try cutting a scaled smaller surfboard sample. If that works well, then try to go full scale.

One thing I am wondering is... what 3d software is the most popular for designing surfboards these days? I found shape3d and boardcad used to be quite popular, but when I searched the forums here, it seems that most of the discussions about these apps ended around 2017 or so... are they still relevant? I have some experience with Fusion360, but I'm not sure if Fusion would be the best/easiest choice for surfboard design.

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sharkcountry's picture
Joined: 03/25/2006

Update on the board I'm making. All the foam was glued up and perimeter bands were added. I hand shape the blank to get it squared up. This is the top before the rail bands were added. The shaping is done and I laminated the bottom, but I didn't take new photos. I will get more photos later.

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karolis's picture
Joined: 07/11/2022

@sharkcountry that looks very cool. Do you expect the board to be as strong as the one made from a single foam block?

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sharkcountry's picture
Joined: 03/25/2006

I usually add a balsa deck skin either 1/16" or 1/8" thick sheets of model airplane balsa. I also try to keep the laps going all the way around the rail. So far, I haven't had issues with the boards. The balsa decks are very strong against pressure dents.

I believe the glue joints add a lot of strength compared to a single piece of foam. They are spaced just under 2 inches apart. The foam is about 1lb density, when I get foam that is softer, I don't use it.

If anything, this process is much more complicated compared to a single block of foam. I do it because I had all these small EPS coolers coming to our house and gave away as many as I could. I believe this is the best way of recycling that foam. Sending it to a place that breaks it all up then fuses it back seems to require a lot of energy. I use a bit to cut up the coolers and a little more in the shaping.

If I was making boards for other people, I'd buy a good PU blank and do it right.

This is just something I can do with excess foam that would end up in the trash bin. I've made 5 now and 3 are used quite a bit.

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Honolulu's picture
Joined: 04/28/2004

karolis:  the best CAD software is probably the one that you're most familiar with, and the one that exports a toolpath your machine can use.  Unuseable toolpath = useless software.  And that's all I know about CAD/CAM.

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karolis's picture
Joined: 07/11/2022

OK so the CNC homing issues are fixed and machine is almost ready to cut. 

I also played with Board CAD, AKU shaper and a few other programs. From all the apps dedicated to surfboard design, AKU Shaper seemed like the most promissing one, but in order to use it with my CNC machine I would have to pay $45/month and still get an application with very limited features. Meh. I went back to good old Fusion 360 and after a few days of tracing the slices and outlines I have a virtual copy of my current board.

I still need to add fin box positions, cleanup the design a bit and buy a compressor to blow off the foam dust. The foam is going to be everywhere! Hopefully I can do some test cuts in the next few days.

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condition_red's picture
Joined: 11/06/2006

EPS gets everywhere.

I babysit with a shop (25 liter drum) vaccuum cleaner and suck foam bits up every few minutes.

Support your blank at the ends. The foam will bend away from the cutter.

I use Shape3D on Mach3, but there are Euro involved in the S3D CAM license.

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karolis's picture
Joined: 07/11/2022

First attempt to cut a scaled down version of a board. There are some small issues but in general the concept works fine. With the current settings it would take around 2.5 hours to cut a full size kite board. I think after some tuning I could bring the time down to around 1 hour.

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McDing's picture
Joined: 05/22/2004

It is amazing to me how nice those blanks turn out once you've shaped them.  Impressive.  The balsa deck is good insurance.  Ever do one in which you did both the deck and bottom.  You know; just to the cutlap?

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sharkcountry's picture
Joined: 03/25/2006

I used to put wood on both sides, but those were the compsand boards we did. Probably been 4 years or so since I did both sides. The balsa wood decks keep the pressures down.

I think the main strength is in the glass because most of the boards I do are stringerless. I do double lams on the bottom, one before fin boxes and one after the deck is done and the boxes are set. Comes out a little heavier, but not as heavy as a strong PU/PE build. I'm just about done with this one, I really hope this one does all I expect for a 7' board.

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McDing's picture
Joined: 05/22/2004

Yes sir!  As I said; "I am impressed".

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sharkcountry's picture
Joined: 03/25/2006

Finished board with balsa deck and wax grip from Viskus. Rode it yesterday, and It's doing what I hoped it would. Going to play with a variety of fins for a couple of sessions.

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Honolulu's picture
Joined: 04/28/2004

I'm pondering and EPA build, maybe....  I want a nice blue or green tint (not a pigment) but I know well that the blank has to be really clean for a good result.  Long ago I helped a kid do his first epoxy lam on his first EPS blank, seemed that clear board could be expected to come out nicely.

Was your blank skimcoated (spackle or whatever) then sanded smooth before glassing?

Is the apparent blotchiness of the bottom the best that can be expected from EPS?

Thanks

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sharkcountry's picture
Joined: 03/25/2006

I use a lightweight spackle to fill in the beads and any tear outs, then sand until I see foam.

The bottom lam would be a ittle nicer if I sanded it better and buffed it. It has a rattle can clear coat and it's not a good job. Because this blank is made from so many pieces, a tint doesn't look good.  

I have other boards with a light pigment, looks like a tint, that are OK. One thing that becomes an issue with tints is having the footballs under the boxes. Those always come out darker.

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McDing's picture
Joined: 05/22/2004

I'm sure I have mentioned this before;  On Maui Kenny Tilton use to pick his blanks up after the bottom had been lammed.    He would take them home and vacum bag a veneer onto the deck.  Then back to the glasser for the deck lam.  The glasser at the time (Moonshine??) wasn't set up to vacuum bag.  Especially veneer.  If you do a clean lap, whether free-lap or cut on a clear it's no sweat. Doesn't matter where the lap is because the veneer covers it.  Even on a pigmented bottom, a good paper backed veneer cannot be seen through.

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McDing's picture
Joined: 05/22/2004

Most tints and even opaques tend to come out splotchy in Epoxy.  Partially the spackled foam, but often because of the pigments used when combined with Epoxy Resin.

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Honolulu's picture
Joined: 04/28/2004

McDing wrote:

Most tints and even opaques tend to come out splotchy in Epoxy.  Partially the spackled foam, but often because of the pigments used when combined with Epoxy Resin.

It's obious that the "beady" nature of EPS, even after spackling and sanding, will leave areas which are more open-cell than others, so a tint will produce poor results compared to a foam with an even surface texture and porosity.

1. Long ago I was listening to Ted Wilson (Fiberglass Hawaii owner) state that tints and opaques had the same base or vehicle (a glycol of some sort, I'm no chemist) and were somehow thus compatible with both polyester resin and epoxy (at least he implied they were compatible with the products he sold).  It's also known and confirmed by Ted that the more effective (and hazardous)  components that were once used, are no longer in the formulation, so pigments especially lack the color saturation they once had.  This is particularly tellling in the darker pigments like red and blue, less so in yellow.  McDing are you suggesting that the vehicle in pigments is/are not completely compatible with epoxy?

2. Further on potentially incompatible vehicle, is it suggested that dry powder pigments (which would lack a vehicle) would have better results?

3. Avoiding tint or pigment, would the best solution for a colored EPS board then be a spray, using a vehicle that overcomes the hydrophobic nature of EPS?  Maybe an alcohol or a similar compatible solvent or wetting agent that doesn't dissolve EPS?

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karolis's picture
Joined: 07/11/2022

Here's a pic of my first cut. It was taken before I did the last contour pass, so the edges are not very pretty, but overall I'm happy with how everything worked out. Need to fix the design a bit and cut another.

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karolis's picture
Joined: 07/11/2022

A few others

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sharkcountry's picture
Joined: 03/25/2006

Amazing that you built the machine yourself. I wouldn't worry about having a perfectly finished shape. Most shaping machines leave a bit to finish by hand, especially the rails. If you get the rocker and profile dialed in, you are set.

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karolis's picture
Joined: 07/11/2022

sharkcountry wrote:

Amazing that you built the machine yourself. I wouldn't worry about having a perfectly finished shape. Most shaping machines leave a bit to finish by hand, especially the rails. If you get the rocker and profile dialed in, you are set.

Well, it was quite a journey, I started around July I think. A lot of things didn't work as I planned. On the other hand a lot of things did and now the machine works. It is not an industrial CNC, but I think I can cut one board in less than 2 hours. With some upgrades I will probably fit into 1:15 or so. For personal use, it's not bad. Plus the CNC was cheaper than the board I was copying hehe )

Now I will need to learn how to laminate it : /

The profile and the rocker I copied from a board that I bought some years ago. It was a really nice shape and I loved how it felt on the water, but it delaminated too quickly, so I decided to do my own :)

I still haven't decided what to do about the stringer. Usually kite surfboards don't have them, or have it made from foam wrapped in carbon fiber. I have to build a few different boards and see how they feel.

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karolis's picture
Joined: 07/11/2022

I have a question about the bottom edge. In the 3D model I have the entire bottom edge sharp ATM. I will probably need to round the front part and keep the tail sharp. The question is: how much should be left sharp? Only the fin area? 25-30% of the board? What happens if I leave like half of the board sharp?

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Honolulu's picture
Joined: 04/28/2004

Not a kiteboarder myself so take it with a grain of salt.  I've watched a lot of kites ripping up my local at Diamond Head, Kahala, and so on, Robbie Naish in his day, waves double to almost triple overhead.  Impressive stuff but a real pain in the arse when three kites get a rotation going and no surfer gets any waves after that.

Think of the water flowing off the board... at first glance you'd want clean release from the wide point of the board to the back.  There are those in the surfboard community that hold differently and it's almost a religious contention, but in kiteboarding you probably never have a lack of power, so wasted energy is assumed an issue.

Going farther, turning a kiteboard is a wholly different than turning a surfboard for any number of reasons.  One, your driving energy comes from the sail, transmitted strongly dowward to the board through the soles of your feet, rather than gravity and/or the different accelerations of water vs board angle of attack in different parts of the wave. Next, a kiteboard has one rail nearly completely immersed (a simplification) when going in a straight line, while a surfboard has more equal (left/right) immersion.  This might suggest that the sharp/dull rail question is not relevant at all.  Three, surfboards have a much shorter turning radius and body language than a kiteboard, so (for turning anyway) the considerations for one may be completely irrelevant for the other.  You can briefly use a kiteboard as you would a surfboard, but you'll very quickly miss the driving energy and grab the sail pretty soon... you'll have to, slack lines to the kite mean no drive and no control, and you'll bog.  Four, and again a result of all the available drive, kiteboards can be shorter and still work well.   They (almost) don't even have to float, so volume is a non-issue... it's a lot about surface area (again, minimized because of the drive available).

The more I think of it, the kiteboard vs surfboard comparisons grow farther and farther apart.  All together, a kiteboard has such a surplus of driving energy, why would it matter at all? 

Blend it and call it good:  leave the front half blunt-edged, the back half sharp, and blend between the two as you see fit.  Sharper rails ding more easily.

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lemat's picture
Joined: 04/17/2010

Wind toys, windsurf and kite, have always tuck under (sharp) rails all the way. They need first water release for planing. For flat water, they have 0 (race) to minimal (slalom) entry of bottom rail. Those boards need first to plane straight fast with reduce agility/control in speed turns. For waves they have more entry of bottom rails but sharp like Maurice Cole or Greg Griffin surfboards rails. 

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