blue cored sandwiches

anyone toy with slicing blue dow into 3/16"-1/8" thick panels to use as a sandwich core around soft EPS inplace of wood, dcell, corecel???

slicing and dicing our own wood strips and frames on a bandsaw out of solid wood boards leads us to believe we can use the same cheese slicer technique with a proper hotwire jig. Like a 2’+ wide stationary re-saw hotwire jig you could slide your blue dow panels under to slice off ultra thin 1/8" slices of blue foam that you would sandwich between layers of glass over the top of 1lb EPS like you would do with balsa skins.

there’s a risk for delam but with 1/8" thick blue how much gas can there be in there?

also the classic balsa wood water seepage discoloration delam problem would be eliminated.

and if you don’t put any bottom skin over the EPS you could end up with a cheap firewire knock off as you stiffen up the deck with the blue sandwich and wood rails and let the bottom flex with the EPS. you’re also transfering the weight out to the solid wood rails

there’s nothing lighter and more solid than blue dow

just as light if not lighter than balsa and totally water proof unlike an untreated balsa wood core.

just gassy and tempermental to stress I guess.

Okay

now please tell us we’re stupid… stupid

-homer bile

I think it’s a great idea, Airex, corecell etc are too pricey…

I had an idea a while ago about impregnating higher density EPS with epoxy or foaming PU glue, by sucking a measured amount of either into the EPS with vacuum.

Make your own higher density sanwich core, totally waterproof, and you can vary the weight/density perfectly by using a different weighed amount of resin or glue.

No bonding issues, delams, gassing… and so cheap it’s ridiculous.

Kit

what is the density of blue dow? near D-cell or corecel?

seems pretty dense

the corcell we got from fiberglass hawaii seemed alot coarser more open bubbles/gaps

you don’t see that with this blue

the texture seems almost solid creamy like

kind of what you’d expect from a blue creamcicle

maybe that’s why water doesn’t like it

cause there’s no gaps to penetrate

and probably why not too much stuff likes to stick to it.

also probably why they make good sound insulation panels for walls and roofs

Cheap is right

a 4’x8’ sheet of 1/2" thick corcell from Fiberglass Hawaii was almost $90

a 4’x8’ sheet of 2" thick blue dow XPS is around $40

we figure we can get 8-14 1/8" thin 4’x8’ sheets from one $40 blue dow panel with a proper ripping hot wire jig.

each 1’8" 4’x8’ sheet can make the top and bottom skins of a board and some rail bands as needed.

so that’s 8-14 complete board skin cores from a $40 plank

way cheaper than anything else other than free wood or just pure glass.

we’ll see

we got a couple panels to play around with

hopefully all the braniacs aren’t laughing too hard at us…

we’re only playing anyway

so what the heck…

we’ll keep you posted

yep…

test results were very promising in test panels …

finished boards ??

lets just say , they dont exist on my list of product possibilities …

the closest i got to something bordering on a workable solution was a 10mm sandwich …

issues …

density …

shear movement creating failure at the bond lines …

the right thickness to get a resonable strength was an awkward size to work with …

all the other usual XTR issues …

in the end , the work and effort for reward was not balanced …

but like many things written off , could be potential if some of the quirks are solved …

had a few things i worked with Josh aka speedneedle on , where we started covering ground i had covered in the past , then a few suggestions from him and all of a sudden , whole avenues of possibilities which had been completly written off , were now viable again , because of a different perspective on problem solving …

so maybe some of those comments will at least get you guys a little closer to the mark , and then a different approach may get past some of the issues i had …

regards

BERT

www.sunovasurfboards.com

I think STARBOARD is starting using DOW slices for their “new” hollow EVO sailboards.

Blue Dow buoncy billet foam doesn’t seem to have the compressive strength to make it a worthy substitute for ridgid pvc foam. The bandsaw slicing method sounds better than hotwire because the hotwire seems to leave a slick melted plastic surface that i’ve percieved needs to be sanded down to unmelted material for bonding.

oneula, i order loads of blue foam each year for the students to use in my workshop and it sounds like for cutting it into the strips your talking about you would find it easier on a bandsaw, the hotwire has a tendancy to wander and any slow down in your speed as you pass through will leave you with ridges.

at least with the bandsaw it cuts like butter and you wont get to much heat build up in the blade so you can adjust your feed speed whenever you want.

Quote:

Blue Dow buoncy billet foam doesn’t seem to have the compressive strength to make it a worthy substitute for ridgid pvc foam.

as a core or a shell over a hollow like Niera shows I can see the issues from our previous experiences with it.

but…

as a filler to build a composite sandwich skin i,e, thickening the glass layer over shaped EPS blank its seems to have some promise as the strength is being provided by the solid perimeter wood rails and the weight and type of layers of glass used to cover the EPS. After fooling around with different sandwich cores, it seems alot of them have issues with either water penetration like wood or resin weight due to over saturation of resin into foam sandwich core. The cure for it all being some type of sealing pre-treatment of the wood or PVC/Corecel etc… Blue seems super light and has a low absorbtion rate of just about anything which is its problem. If you can find a way to improve it’s mechanical bonding and load bearing capabilities like roughing up the surface and tapering the thickness, it seem like it has a potential as a core “filler” between sheets of glass. I think the key is not to use it for a hollow design but just as a thin filler layer that provide some for or waterproofing to the external skin

problem is there’s so many issues with blue especially shear stress (you know the Kabang! failure)

but there’s issues with everything we’ve tried

and it’s much more economical to play with this stuff than balsa or the other foams

the bamboo is looks good but it’s relatively expensive, stiff and heavy.

composite laminates I made of the woven bamboo around a 1" blue core is much lighter than a 1/4" version of the hollow same rib design made of cedar and about as a simlar rib in balsa only 4 times as thick as a structural support.

The key it seems is to find a way to take advantage of the waterproofness and lightweight of the bluefoam without having to rely on it for strength. A big challenge for sure and some really weird ideas have been popping up like this one…

make regular glassed EPS board with fin boxes extended out in wood “outserts??”, then… attach a 1" layer of blue to the bottom no glassing just glue it on. then you can keep changing the bottom features/rocker with some sandpaper until you can fine tune the shape. This was first proposed by Eric Arakawa back in the late 80’s early 90’s when he was fooling around with XPS.

Weird but what the heck…

but again we’re just playing here trying different stuff here trying to keep it fun…

We built a large canoe with the blue insulation foam. We used epoxy.

It lasted for one season, which was longer than we thought it would. It just has very poor peel strength. The bottom of the canoe delaminated first (where you would step into it). Also, we used a fairly stout lamination of 12 oz Biaxial cloth with even more biaxial tape on the joints.

With all the time and resin/glass you would put into your project, I dont see how its worth skimping on the core.

I concur on the delam based on what I heard of the blue but…

we’re planning on just placing a really thin layer between two sheets of glass as the covering for the core where the strength from the skin is from the glass/resin and the filler is to just thicken the skin. It’s the whole what is a sandwhich? question Paul posted in his thread.

Our cores are still regular EPS or PU shaped blanks with wood rails where the majority of the overall density, strength and stiffness should come from. I don’t believe it comes from the thin skin of the sandwich itself unless your build is skin based and you don’t need a core such as in a hollow design. The skin seems to be just a way to bind the core and the rail togethor as well as to transfer the loads to both as well. It’s the core and the perimeter stringer’s job to manage the load not the skin. At least that’s what everyone has been saying with their discussions on thickness and shape to performance.

I could be wrong as always but that’s what I reading between the lines…

Stress factors and material selection have to be addressed totally different if you are totally reliant on the skins to carry all the full load like a hollow. For that you need carbon/high density foam/honeycomb/or wood within the skin sandwich.

but it’s just for fun.

we don’t plan on making boards for anyone else we aren’t that concieted about our abilities or even to have these experiments take the place of the boards we buy from Griff or any other knowledgeable surfboard crafter we choose to support here locally.

Make-em to break-em should be new our motto

there’s alot of freedom in a crowded line-up when you able to think like that with your equipment…

that’s why the pro’s are so good

no matter what happens

the boards just keep coming their way

so they can push things right to the limit

getting better with every missed attempt

without fear of equipment loss

Oneula, Sounds like the blue foam you’re looking at is the “small cell styrofoam”, vs. the large cell buoncy billet material. Aircraft Spruce> composites> foam, differentiates the two with different desciptions, both 2# density, small cell gets a good write up for compression and water absorption. Soloman used the small cell material I’m pretty sure from trying to look closely at their foam thru the outer skin, the verdict must be in by now on how well Soloman foam held up?? I didn’t get your idea for the backside of the outer foam layer but I’d think a fabric bond onto the backside of the outer foam would be a lot better than not. I did some resin test panels on large cell blue without backside fabric, so breakable; with backside fabric, pretty touph.

dow links:

http://www.dow.com/styrofoam/na/story.htm

http://www.dow.com/styrofoam/na/corefoams/prod/index.htm

and

http://www.dow.com/styrofoam/na/pro-us/products/

on the last one, check out the square edge (most common) and the Highload series, the numbers correspond with compressive strength, I think the square edge is 25, and the hi-loads go up to 100. The core stuff looks interesting, but I can’t see how you could make it wrap at all, unless you used some kind of kerf-cut scheme…it’s stiff and snaps…!pop!

Also, isn’t spyder foam similar, but with a grain that enhances compressive strength?

I made a board out of the blue stuff a few years ago, ditto on the poor peel-strength…my backyard solution was to score the blank lightly with xacto blades, about 3/16" deep 1/4"apart, runnuing tip to tail, and squeegee in epoxy prior to glassing, gave it a nice oxford pinstripe look :slight_smile: I still had delam problems…all under my back foot and knee-place, and one side duck diving spot. That was of course in the pre-vacuum days…

I also made a rocker bed out of it, and also observed that hotwiring with precision is problematic, I kept getting melted gobs and stringers off the wire that would settle into the bottom piece…I just did it so that my offcut was down, kept the top piece smooth…

Just messing around with the stuff gives me the sense (from a very unqualified point of view, mind you) that it would be a better match to carbon than glass, it seems to have that stiff, unyielding quality, and next to it, a glass lam feels too flexible…

Quote:
anyone toy with slicing blue dow into 3/16"-1/8" thick panels to use as a sandwich core around soft EPS inplace of wood, dcell, corecel???

I did one once but I used 1/4" XPS skins with a 1 lb. EPS core. I didn’t do sandwich skins, I just glued the XPS skins directly to the EPS with Gorilla glue. I used XPS for the rails also. I glassed it normally.

The great thing is I was getting the board ready for a trip and I was still finishing it the morning I had to leave. I was rushing and ended up with several sand-thrus. I didn’t have time to fix them, but since XPS is waterproof, I didn’t have any problems. I continued to ride the board for about 6 months until I broke the nose off, but I never fixed the sand-thrus. The board went good and had a lively flex. I didn’t have any of the common outgassing problems with the XPS.

I think that’s how I’d approach it too. I’d almost guess that a layer of glass cloth in between the foams would help them peel apart if they ever got started. Not to mention that any gas from the XP would have no choice but to bubble a layer of glass.

I think Oneula mentioned blue rails on a white board a year or more ago, and at that time my rec. was to put them on with foaming PU glue. That way, if there was any trapped gas in the XPS, it could migrate into the porous EPS and not bubble/delam the glass. No reason that’s not true for a whole shell.

I’d bet that 1/4" XPS skins & 1/2" XPS rails on an EPS core, glassed with double 4 bottom, double 6 top would make a great board.

And, to agree with Silly, it wouldn’t be a “sandwich” :slight_smile:

It would be good to hear from Drewtang on this thread, he made a bunch of boards with bluefoam, some as a core some just on the rail. They looked great but I don’t remember if he ever put up an update on how they worked or if he had the dreaded delam problems. I would be really interested in how they work out if you do this Oneula, I’ve been thinking about the same type of construction lately but can’t really afford any epoxy right now.

cheers

well someone’s figured something out cause when I was at the Chuck Dent shop they had racks of solid blue dow foam board new and used and I didn’t see any with any signs of delams although the used ones has normal pressures that I would’ve concluded should’ve led to out-gassing if you believe everyone on this forum.

They don’t use Javier XTR pinholing technique either so I was really curious thinking it was all a gimic. But the shaper said you just have to know how to glass the stuff properly to compensate for its properties and they aren’t any different than any other EPS board… He did admit it involved a different glassing technique.

So I’m puzzled whom to believe regarding the blue…

Guys making tons of them for sale or guys making a couple here and there for personal use.

you just never know about anything anymore.

For us it’s just significantly cheaper than getting balsa wood strips out here in hawaii and way more waterproof and lighter than anything in wood with a similar waterproofness…

how’s that saying go…

now don’t you try this at home…

that’s out disclaimer…

Quote:

well someone’s figured something out cause when I was at the Chuck Dent shop they had racks of solid blue dow foam board new and used and I didn’t see any with any signs of delams although the used ones has normal pressures that I would’ve concluded should’ve led to out-gassing if you believe everyone on this forum.

They don’t use Javier XTR pinholing technique either so I was really curious thinking it was all a gimic. But the shaper said you just have to know how to glass the stuff properly to compensate for its properties and they aren’t any different than any other EPS board… He did admit it involved a different glassing technique.

I’m curious about how one would glass it “different.” Hold your tongue just right??? I heard back when people were first using XPS and having delam problems, that the trick was to sand it to about 50 grit as the finish shape. This is supposed to give the epoxy something to hold on to. I don’t know if it helped or not, but that’s what I heard. Obviously, it wouldn’t control outgassing…

Allow me to re ask a question. Soloman used the blue foam, we must have durability knowlege by now from that commercial use? What was their glassing method? The Board Lady might have some insight on Soloman blue core durability?

Alright. I did have some delam problems, the usuals. It was the groms at the beach all day. Anyway, I’m riding it just not selling 'em. Using it plenty on rails as a dual density. No problems with those. I think it’s more that there’s so much cloth on the rails. There’s ways to do it for sure. I STILL haven’t tried pre-gassing yet, somebody should try that. It helps to scuff with 50 grit or something like said above. I swear though, it’s the best RIDING foam there is. I’ve got a few billets left and will def. re-up it when it’s getting lower. I just can’t risk selling something that even has a REMOTE chance of coming back in the factory for a freebie re-make. I had to re-make 15 boards last year with PVC stringers too. THAT SUCKED!!! I threw 50+ stringers in the dumpster. Point is the Dow rides unreal, build yourself one just be careful taking somebody’s hard earned money for it. I just wish there was another way around poking vent holes in it. Here, I’ll be “that guy” and post a pic of me playin the violin on mine:

and another teamer on his: