9' longboard out of XPS foam

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elegcorrea's picture
Joined: 08/19/2020

Hey everyone, 

I've tried searching for this topic on so many sites but haven't been able to find it. I want to make my own 9' to 9'3" ish blank and would like it to be out of XPS foam. The biggest this foam comes is 8' so I was wondering if anyone thinks its possible or smart to do this... 

Adding about a foot of extra foam to the 8' long board and gluing them together with a polyurethane glue? I was also thinking it might make it stronger if I could insert a small wooden beam into both ends of the 8' board and the extra foot of foam to make it stronger?

Let me know if this is too crazy to try or if you have any advice, thanks!

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stoneburner's picture
Joined: 12/30/2007

You could stagger pieces of 8' foam.

Adding a piece at the end will likely result in hinging.

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RDM's picture
RDM
Joined: 11/14/2004

If you aren't using multiple thicknesses of foam and are unable to stagger them, I would cut like shown below (top view), and glue with epoxy or polyurethane.

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jrandy's picture
Joined: 09/04/2012

I normally have to add 6" for 12'-6" SUP's made from 12' EPS. I do this to the tail. PU glue.

With  XPS I am not versed. The joint shown by RDM does look good to me.

Are you planning stringered or stringerless on the XPS?

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http://pushheretosavealife.com/ Be safe, have fun. -J

stoneburner's picture
Joined: 12/30/2007

I think RDM's solution would be the simplest for you, and should be strong enough with foam patch at nose.

The following is a 2' x 10', staggered foam piece blank made with 8" strips of foam (no longer than 8').

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gdaddy's picture
Joined: 10/31/2008

Before you go gluing anything up I'd do some experimenting with glues because XPS is notorious for being difficult to get adhesion.  

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stoneburner's picture
Joined: 12/30/2007

gdaddy wrote:

Before you go gluing anything up I'd do some experimenting with glues because XPS is notorious for being difficult to get adhesion.  

3M 78 works fine for XPS. Could be a bit of a challenge for gluing foam strips.  The trick for 3M 78 is allowing a 36-48 hour cure time for maximum bond strength.  It sands better if shaped right away though.

Pretty sure Sharkcountry and Oneula use polyurethane glue for their XPS builds.

The biggest challenge with foam mosaics is sanding glue lines.

EPS and XPS are both made from "polystyrene."  FTR the only reason EPS bonds better with epoxy is because it's porous.  The adhesion problems with XPS and epoxy are because it's 100% closed cell (not porous) -- reason why XPS doesn't absorb water when dinged.  XPS adhesion problems are also related to using low density XPS (1.3 pcf).

However, I agree.  Gluing up a few pieces of scrap XPS with polyurethane glue and 3M 78 is a good test/practice run.

.

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RDM's picture
RDM
Joined: 11/14/2004

Minimise the glue lines if you can. They do require extra attention at the end as they will all stand a little proud of the surrounding surface and you have to go around with some sandpaper and a small, hard block, and finish each of them back.

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sharkcountry's picture
Joined: 03/25/2006

I prefer staggering the foam the way the way Stoneburner shows compared to the way RDM has it. Done it both ways, and it's easier to glue straight lines versus the vee cut. I also have made many by cutting rocker strips to get more rocker than the foam I had would allow. A foaming polyurethane glue like Gorilla Glue works really good on XPS.
I'm backing off from XPS due to delaminations caused by heat. You can add pinholes on the board to help avoid heat delams. Last summer was pretty hot here in Hawaii and 2 of my XPS boards developed large delaminations. They were stored outside in a well ventilated shed.

XPS shapes easily compared to EPS. I make a lot of my boards stringerless and they've held up to the abuse.

Something that I noticed a few years ago, when I stripped and made a new board from an old XPS board I had... the glass peeled off very clean and very easily. This is probably why it delaminates so easily.

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gdaddy's picture
Joined: 10/31/2008

I like the way xps shapes and rides but they do require a higher level of care insofar as handling and transporting are concerned.  You can't let the board get any hotter than it takes to melt the wax on the deck.  In cool climates that's not a problem.   But leaving the board exposed on the beach on a hot day or leaving it in your truck on a hot day is a no-go.   

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unclegrumpy's picture
Joined: 09/16/2006

I wonder if that issue could be eliminated by perforating the foam in the fashion of a wallpaper perforator prior to glassing? A whole bunch of tiny holes to give the resin something to bind to....

I know that German guy who came up with the Hydroflex glassing technique does something along those lines. At Boardroom a couple years ago he had taken one of his boards and sliced it into quarter inch slices. You could not pull the glass off them.   

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No; It's not an ironing board.

sharkcountry's picture
Joined: 03/25/2006

Javier at XTR adds tiny holes after the lam to allow air to escape to help avoid delams. XTR had a really good white XPS foam. I don't know if they still have that foam, but I liked it.
That board I showed was sanded with a block and 60 grit media. It is really course compared to a finished PU or EPS blank. The foam is blue Dow XPS.

I thought the hydroflex boards used EPS foam, but I don't know for sure.

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sharkcountry's picture
Joined: 03/25/2006

Javier at XTR adds tiny holes after the lam to allow air to escape to help avoid delams. XTR had a really good white XPS foam. I don't know if they still have that foam, but I liked it.
That board I showed was sanded with a block and 60 grit media. It is really course compared to a finished PU or EPS blank. The foam is blue Dow XPS.

I thought the hydroflex boards used EPS foam, but I don't know for sure.

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stoneburner's picture
Joined: 12/30/2007

unclegrumpy wrote:

I wonder if that issue could be eliminated by perforating the foam in the fashion of a wallpaper perforator prior to glassing? A whole bunch of tiny holes to give the resin something to bind to....

UncleG,

I shape the XPS with a surform and 60 grit.  I final sand to 100 grit.  I then vacuum foam dust off surface.  Then I use a modified TopFlite Woodpecker Tool (doubled the number of tynes).  I perforate the shaped foam with the WP tool.  I pre-seal with a thin layer of epoxy.  Then sand to 150 grit. I laminate using epoxy with opaque white pigment (to reflect solar heat).  I don't use less than 1.55 pcf XPS.  Saving my higher density XPS for when I have my new designs well dialed in.

The perforations the WP tool makes are linear.  So I have started playing with the orientation of the slits relative to the long axis of the board.

Next board, I will pre-seal using epoxy with opaque white pigment and vac bag the pre-seal into the perforations.  Tried 45 degree orientation last.  Will try 90 degree next (should help minimize parallel surface movements of the glass skins).  Will also laminate using epoxy with opaque white pigment.

Pretty sure I have it mostly dialed in now.  But XPS does get soft in high heat.  

I still have a few tweaks I can try to further imrove bonding/prevent heat delams (one would be using white EVA foam on the deck).

But the number one of advantage of XPS is it does not soak up water -- 100% closed cell (does not breath).

Top tool in picture below has 8 rows of tynes (modified).  Bottom tool only has 4 rows of tynes (stock).

Bill

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McDing's picture
Joined: 05/22/2004

Stoney--  That is all good info and makes perfect sense for the foam.  A good system and methods.  Lowel

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parthenonsurfer's picture
Joined: 02/19/2010

Your lucky to have that WP tool. It's no longer made. I've been searching for a tool similar to that to perforate the painters plastic I wrap around board during layup (as a peel ply) before vacuum bagging my lams. Ebay currently has one but the bids are up to $67 (that's way to rich for my blood).

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lemat's picture
Joined: 04/17/2010

When we started make airplane RC wings by vacuum bag fiber and resin we used xps. No problems. At that time i made surfboards with Clark foam and sometimes epd/epoxy. Tried xps surfboards but every times delams under foot even with punch holes foam. Bufo (hydroflex) were first pu foam with punch holes then went to xps punch holes then to eps... Salomon bleu were a thin layer of xps, surftech tufflight use some xps for sandwich foam when they move from pvc foam to wood. Each time i repair some i must take care to not Peel off too much skin...

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stoneburner's picture
Joined: 12/30/2007

There are multiple variables affecting delam and bonding.

Polystyrene surface energy.

Appropriate adhesives.

XPS minimum Compressive strength (correct foam density).

Lack of XPS porosity -- "small" closed cells.

Perforation number, size, shape, orientation, surface area (internal & board surface distribution).  Large (relative) circular perforations have low surface area to volume ratios -- you want high surface area to volume perforations.

Glassing schedule.

Load and impact dispersion (deck skins:  EVA, Cork, etc).

Foam temp (internal gas volume) at time of glassing -- core and surface layer -- affecting post glassing expansion and contraction.  XPS does not out gas (closed cell foam cannot).  Which is more likely to cause delamination, expansion or contraction?

Hand oils on the surface of non-porous foam, from handling during shaping and glassing.  Wear clean or new dish washing gloves.

Board color -- white to reflect solar radiation.

Design and construction must consider these variables.

There are many generalized assumptions when discussing XPS for surfcraft.  I am not trying to convince anybody to use XPS.  Just offering input to those who do want to try it...

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lemat's picture
Joined: 04/17/2010

Except adhésion problem xps is best foam for boards for me. Xtr delam around holes even if their foam is better than standard one's. Broke lib tech skin show easy delam even with multiple punch holes grip and stiff skin. On other hand many guys build their one ez rutan plane by laminate fiberglass on spider foam ( dense xps) and they flight with so...

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stoneburner's picture
Joined: 12/30/2007

As with any foam, XPS has its limitations.  But all of the variables must be properly controlled first.

I had not seen LibTech products.  They claim "impact resistant" and "dent inhibiting."

I think the deck skin property needed is impact "absorbing," possibly used over FG.  I suspect cork would work well, probably better than EVA.  Maybe EVA over cork.  But the correct thickness and density of a PE or PP foam deck skin would likely work too.

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sharkcountry's picture
Joined: 03/25/2006

My board building was always experimental and always for my personal use. I'm probably at about 70-80 boards made now. The foam I use/used and the processes were never done under the best practices, they were done with costs in mind. I have access to the best surfboard materials if I want to go that route, but the EPS and XPS foams I used were always extremely inexpensive, even free. You won't get the best results when you work the way I do, so when they have issues, they may be due to improper construction methods. I know many failures are due to my bad decisions, or lack of thinking things out better. Failure is a big part of learning, so I don't mind some of it. What really sucks is when you make a good board and really enjoy using it, then it delams bad. 

It will take making more than few boards before you figure out all the nuances of board design, not even mentioning the glassing half which is way more work and where a lot of the costs are. When I started making boards again, I had a good job and a lot of "play" money, so the resin and the other parts of making boards didn't matter. I've been retired and living on much less for 4 years now, so the costs matter now. I've made boards with PU, EPS, XPS, hollow wood, and wood veneered. I've made boards with a mix of EPS and XPS too.

If I were to rate the foams I use, I'd put EPS above XPS even though EPS will suck water like a sponge. Main reason is I live in a warm environment, the temps never get too cold, but it does get hot at times. I have way too many boards to keep them cooler than the air outside, and we're seeing temps get higher every year. If you leave an XPS board in the sun it will blister. Other than the heat problem, I like XPS foam. The hollow boards are at the bottom of my list because the places I surf are far from shore and any failure of the hull would be a big problem.

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McDing's picture
Joined: 05/22/2004

Very true Shark.  What I like about your posts is that you are always experimenting with different materials and methods, but do so in a very practical way.  You, Stoneburner and Lemat are real thinkers when it comes to the cutting edge of surfboard construction.  But you my bradda put it into a practical context.  I always point my ears and listen carefully and re-read multiple times to be sure I understand as I am a dull country boy.  The three of you are the best and though I may not necessarily put your methods into use, I have learned a great deal form the three of you.  Lowel

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sharkcountry's picture
Joined: 03/25/2006

Thanks Lowell. I really appreciate the comment.

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stoneburner's picture
Joined: 12/30/2007

parthenonsurfer wrote:

Your lucky to have that WP tool. It's no longer made. I've been searching for a tool similar to that to perforate the painters plastic I wrap around board during layup (as a peel ply) before vacuum bagging my lams. Ebay currently has one but the bids are up to $67 (that's way to rich for my blood).

Wow.  Just checked.  Couldn't find one anywhere online.  I moved mine to a safer storage spot this evening so I won't lose it.

It is not too complex.  Just some 1-1/4" washers on a 3/16" shaft with thin metal tyne wheels between the washers.  Because it is just under 1" wide,  I have considered making something similar that it is 2"-3" wide.  The hardest part would be cutting 1-1/4" diameter, thin tyne wheels -- have considered using canned food tops/bottoms for tyne wheels.  (Larger diameter washers, tyne wheels and shaft could be used.)

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parthenonsurfer's picture
Joined: 02/19/2010

Thanks for getting back to  me. The closest tool I could find  to it was a wallpaper perforating tool made by Warner. It was over $40 as well. Problem is no one stocks it on the Central Coast here & I would really like to see how sharp the needles are before buying it.

I previously bought something on Amazon called a Micro Derma Roller (apparently the beauty industry uses these to punch a bunch of holes in the face for treatment-Weird?), but the needles were too fine and wouldnt put holes in the plastic. Also, it was only about an inch wide as well.

Maybe making one is the solution.The sewing & needlecraft hobbies have a"pattern making" tool which is just one metal tyne wheel. I don't know how sharp the tynes are though. I'll have to look into whether replacement wheels are available.

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stoneburner's picture
Joined: 12/30/2007

The exact tool you are looking for is a "porcupine rolller."  It is pricey.

https://www.aircraftspruce.com/catalog/cmpages/vb9060porcupineroller.php...

Another version is made for carpet backing.  Pricey also.

https://www.tools4flooring.com/gundlach-pr2-porcupine-roller-p-1253.html...

Also there is a tire perforating tool.  Very pricey.

https://troyerracecars.com/products/216/tire-perforator-tool/?q=vendor%3...

Below is a photo of the basic components of my Woodpecker Tool.  The tyne wheel is about 0.02" thick.  For me, the linear (vs. circular) shaped perforations are important/preferred.

(BTW I noticed there is another WP tool listed on eBay -- for the moment, current bid is less than $67.)

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sharkcountry's picture
Joined: 03/25/2006
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stoneburner's picture
Joined: 12/30/2007

Harry,

That "WARTENBERG Medical Diagnostic PINWHEEL 7 ROWS"  looks like it might have good potential for Parthenon's perforating needs.

Only unknown is the 7-wheel head width.

Nice find.

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sharkcountry's picture
Joined: 03/25/2006

I just did a google search and found those. I may try using one of those if I make another XPS board. I have enough foam for another short board. I like the idea of gluing wood veneer directly to the foam with foaming PU glue, then I can glass over that. I think that would solve delams, and I still have quite a bit of thin balsa.

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parthenonsurfer's picture
Joined: 02/19/2010

Thanks for finding those Wartenburg devices. The 7pin version is exactly what I was looking for. I talked with Stoneburner (thru pm's) and we both decided to each order (2) of them. They aren't very expensive to "experiment" with and will I keep everybody posted on how they work when I start my next build next week.

Cheers,

Chris

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sk8ment's picture
Joined: 08/22/2013

On the sunshine coast here, there are quite a fey guys using XPS as a core for glass less boards with layers of 2 mm Paulownia veneers, over the deck and bottom combined with cork strips on the rails. 

Combining the EPS with foaming PU glues and vaccum bagging you can get a really strong board with limited delam issue.

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@reclaim_surf formerly Skatement

(Adam) Sunshine Coast Queensland Australia

sharkcountry's picture
Joined: 03/25/2006

Foaming PU glue is the best for XPS and EPS. In my experience you have to make sure the glue covers the whole board. Air gaps are where a delam occurs. It also helps to keep the foam slightly rougher like 100 grit or 60 grit media.

When I was a kid we used styrofoam boards that were not glassed or sealed. They didn't last long, but it is possible to ride them without glass. We could also get the styrofoam boards with wood stringers. They'd always break right where the wood starts or ends. We learned what "rash" was riding those things.

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GoodDays's picture
Joined: 05/05/2020

Adam,

You referring to Steve at etc? https://www.etcsurfboards.com.au/board-types

I'd be keen to hear how his boards ride. Have come across him in a few different ways and seems like a thoughtful shaper. Let me know if you've riden one of his shapes, interesting fella!

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stoneburner's picture
Joined: 12/30/2007

Got my  WARTENBERG (7-Row) PINWHEEL Tools today.  Tested them on some Foamular 250 XPS. Worked well.  They look like micro-perforating tool jewels.  Nice stainless steel handles and wheels (got some foam dust on the bottom tool handle).

If I didn't have my TopFlite WP tool, they would be my go to XPS perforator.  Should work great for Parthenon's application.  Will use the WP on top and bottom surfaces and Wartenberg tool for the rails.

Combine the pinwheels from 2, Wartenberg 7-Wheel tools and you have a very affordable "Porcupine Tool."  (Paid $14.52 on eBay for 2, delivered.)

Great find Harry.

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