Decided to try shaping a different material for BB/Paipo builds – high density, cross-linked polyethylene foam. Should be lighter than wood and not too much heavier than stringerless foam with a heavy glassing schedule. No glassing required.
Eliminating glassing should speed up the build/prototyping process. Will try a simple, standard shape to figure out shaping first.
Only color available from supplier in this density.
This will be a slow build while I figure out how to shape it.
Is it waterproof and how strong is it ?
Are you thinking of using power tools or can you shape it with only hand tools ?
Hot nichrome wire?
Will coarse sandpaper (by hand) do anything without tearing it up? Or wood rasp or one of those microplane food graters ( originally a woodworking tool) ?
good luck, interesting material
doc…
At 6 pcf, it is lighter than balsa (8-14 pcf). The 6 pcf XLPE is fairly stiff with a little flex. As a closed-cell foam, it has low water absorption.
I think the 6 pcf density is probably too dense for a hotwire cutter.
The sample 6 pcf XLPE seemed to sand fairly well – a bit better than the 6 pcf microcell EVA. I plan to try shaping by hand with coarse sandpaper, wood rasp and surform and a hand saw for the first basic-shape board.
May have to move to power tools for adding a channel without CNC (bandsaw and Rockwell Versacut mini-circular saw).
I’m thinking a disk sander or belt sander could be used to shape too if you wanted to speed things up.
This is mostly for more rapid prototyping. If I can get the shaping dialed in, I may give the 6 pcf EVA a try – $50 more expensive per 3" x 24" x 48" slab.
So where do you find such a product?
Yeah, I think you’re right, plus (going back a ways) I once made replacement fins from HDPE cutting boards, thick industrial ones. It’s an interesting material.
I found that if I let the solid material get hot ( dull power tools or sanding discs) it tended to melt and re-freeze behind the tool.So a hot wire would maybe be the worst choice, silly of me to suggest one.
On the other hand, sharp steel blades or bits (not carbide) should work well, maybe get cute with a router with a spiral cutter and some jigs? Oddly, a good and very sharp low angle woodworking plane might work for you. Worth taking a cut or two to see.If it works, then that might be the trick for a channel.
Should be fun
doc…
A few years back I found a retail supplier of 2"-3" x 24" x 48" EPS foam sheet online (in Michigan). The EPS was listed under their “closed-cell” foam products.
I also noticed they had high density EVA and a few other foams. So when I got my current high density idea, I looked through all of the closed-cell foam products they sold and found the 6 pcf XLPE.
EDIT:
A couple of years ago, I bonded two, 6-pcf EVA swim kickboards together to get better floatation for pool laps using bodyboard swim fins.
A few weeks ago, I remembered that on-line foam supplier had 6-pcf EVA and XLPE. So I decided to give it a try for BB/Paipo builds. XLPE was/is cheaper for exoerimenting.
I had a meeting yesterday with a CNC shaper approx. 100 miles from my location.
This was just a test cut on the fly to see how well his machine could cut complex contours – using a piece of XPS I brought along and cutting files (jrandy) I already have.
I will use this cut for experimenting with cork skins under fiberglass.
Next we move to the 3” slabs of 6-pcf XLPE and see what happens. If this works, I can seriously accelerate prototyping.
It looks like they did a nice job converting the CAD data we worked on into a specific cutting file for their machine.
I also like that it looks like the Pink Panther is holding a blank…
He’s into it.
I believe you said you were going to eliminate glassing, but I was wondering if it is sensitive to Polyester Resin. I’m sure it could be glassed with Epoxy. I seem to remember discussing this with someone a few years back. Someone was distributing blanks made from a Polyethylene base out here on the West Coast. Can’t remember the name of the company, but they were manufactured somewhere on the East Coast. I was thinking they shrunk when glassed with Poly. I had two or three but sold them… Warvel Foam?? Maybe?
Uncle G and Jim,
Too bad I have to prep the XPS surface for epoxy. I’d be tempted to leave it as is and glass it clear – The Pink Panther special.
Jim,
The Owner/CNC machine programmer is very gifted. His second-in-command referred to him as a “savant.” After watching him work with your CAD files, there is no doubt in my mind that is true. In addition to cabinetry (etc.), they make electric guitars.
The 14-min. CNC shaping time is mind blowing!
Thanks McD. I’m always looking for alternate materials and tech.
The Pink Panther (XPS) was just a test cut to see what their machine could do. The test cut turned out good enough for me use it as a core for cork-skin experiments.
Regarding the charcoal gray Cross-Linked Polyethylene (XLPE), polyethylene has very low “surface energy.” That is, it doesn’t bond well with much of anything. (I store acetone in HIgh Density Polyethylene [HDPE] bottles.) I suspect epoxy would peel off after the first paddle out. PE resin would likely do the same.
Standard bodyboard construction uses polyethylene (XLPE) and polpropylene (PP) foam cores, but uses heat activated adhesives for bonding bottom (surlyn and PE) and deck (PE) skins.
I have vague recollections of a Warvel discussion. I don’t know anything about that product.
The idea behind using the XLPE is to build a single-material BB that can go straight from shaping to testing without further processing (e.g. glassing). Being closed-cell foam it has very low water absorption. At 3" thick, the 6-pcf XLPE foam is fairly stiff and could work well as a BB. All of this would allow me to go straight from shaping and into the water for testing.
At best I’m a mediocre glasser. Glassing, for me, is very time consuming and messy. To top it all off, my work-space has become highly limited (son and granddaughter have moved in due to CoVid.
I have 2 lengths, 3 rail configurations, 3 channel sizes, 2 tail shapes and 2 bottom styles that I would like like to test. So bottom line, XLPE foam and CNC shaping could radically accelerate prototyping.
Best of all, the CNC machine shaped the Pink Panther test cut in 14 minutes. In theory, with Jim’s (jrandy) CAD skills and the semi-local CNC shaper, I could have all of my prototypes shaped and ready for water in one 8-hr day. Only the XLPE test cut will tell…
do you have a comparison table between XPS and XLPE? I can’t find datasheets that used same method to test the materials. I built a lot of XPS boards in the last 14 years, if XLPE is better I would love to test it even if it’s not so common actually… do you have an idea about compressive strenght of the lighter version compared to same weight XPS?
nemoz,
First, it is difficult to make comparisons between XPS and XLPE. For XPS, min. comp. strength gives you a good idea about how easily it crushes (no rebound). XLPE has a high degree of elasticity and rebound.
As density decreases in XLPE foam the flex increased significantly in the foam from the supplier I used. The 3-pcf XLPE had high flex and was much softer than 6-pcf. “Shore Hardness” values would probably be more useful data for comparing XLPE. I haven’t found a lot of data for XLPE foam products. The 6-pcf closed cell XLPE had the most information on the suppliers website.
I based my decisions on the 6-pcf EVA swim kickboards I bonded together and the foam samples I got from the supplier. To get enough stiffness, I needed 3" thick 6-pcf XLPE.
Both thickness and length affect flex. With the 3" thick, 6-pcf XLPE, I probably wouldn’t go much past 48" long.
If you are wanting to make surfboards out of XLPE, it will not glass and you will need greater thickness than 3". You will likely need good Shore Hardness for lower densities.
Link to discussion of Shore Hardness and Shore Scale below.
The attached PDF is the data I found For XLPE foam on the suppliers website.
McDing,
Was the foam you were thinking of called Arcel (70% polystyrene and 30% polyethylene)?
Marko has a closed-cell foam product called I-Foam. I need to check that out.
Got three blanks back from the CNC shaper this past week — 2, XLPE and 1, EVA. The CNC cut the bottom channel and planshape as well as it did the pink XPS. Lots of hand trimming and cleanup sanding remain. The EVA is too soft and has too much flex — will be a good surf toy for the grandkids to play with.
Deck rails and nose still require hand shaping. Started playing with that.
While it requires a bit of muscle, the surform cuts the XLPE fairly quick. A wood rasp worked well too. I followed that with 40, 50 and 60 grit sandpaper. Have to be careful not to shave off too much foam too fast. Need to leave enough “fuzzy foam” to allow for smoothing down to the desired final shape with 100 and 150 grit. Thinking finishing grit should be 400-600.
Seems like a small belt sander with a 40 grit belt might cut the XLPE a bit like a planer. May need to develop a “fine touch” to avoid cutting too much foam to quickly. A stiff brush might help to clean the foam bits out of the grit on the belt. Harbor Freight has a cheap $39 belt sander I might experiment with.
Still waiting on one more 48” basic blank to be CNC cut — planshape and nose rocker only, with flat bottom. This is the blank I had originally planned to post the build for. I want to play with hand-shaping some old tail and rail designs I have. Never built the tail design because glassing it would be a royal pain. This XLPE eliminates the need for glassing.
TBC
I missed this a few months back. Marko primarily uses I-foam for stringers. They told me it is a “construction grade” foam. A few EPS cuts I had them do for me had it as a stringer. Kind of a desert OD color. No report on strength. The Poly foam I referred to was Warvel… Some of the guys around Swaylocks will remember our friend out Pomona way who had a CNC machine and brought in those Warvel Polyethelene blanks. I think they were from the East Coast. I bought a few, but just resold them to a few backyarders up here(NW). I did not attempt to shape one. Just didn’t like the look of them. One of my local guys brought one by the shop that he shaped and glassed. Looked OK, but nothing super special. The foam reminded it me of that canned spray foam that you get at Home Depot. The guy in Pomona sold out and somebody in OC had his inventory. Used to see those blanks for sale on Craigs. Of course this was a few years back. L
I have used a small belt sander on some foam I acquired during the gap after Clark’s closing. The foam was hard and would tear a bit with my Skil. I did not have a “Grit” barrel at the time. The trick with a belt sander is of course the angle of approach. I could run it up and down the blank without catching the belt if I held it at about the same angle I held my planer.
