Can I build a surfboard with little nose rocker so that the side on profile of the board fits within 100mm or 125mm or 150 mm (these being dimensions of foam sheets in Australia/Melbourne if I can make a hot wire cutter)
The 125mm and 150mm ( 5 and 6 inches) should work provided your templates for rocker/sled cutting fit inside ‘the box’. Our first two boards were cut from 6 inch if I recall correctly. The density of the EPS was pretty light (.88 PCF/14 kg/m^3) , after those I got a big block of 1.5 PFC/24 kg/m^3 and been pretty happy with that ever since.
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What program or app is that image from.
@ Chris4 It is the default ‘funboard’ rocker from BoardCAD, output as DXF and opened in QCAD (free 2D version) to show how it lays into the foam. It takes a slight rotation to get it to fit within 150mm.
How do you do the rotation in QCAD. And change the y-axis.
Are you in Melb/Vic/Australia.
Did you get your EPS from ‘thefoamcompany’
Regards
I am not understanding your ? about changing the y-axis.
To rotate, highlight the objects needed and go >Modify>Rotate
(edit) You will be asked for a focus point/center of rotation and then you can specify angle, copies, etc.
I am in the US, the cold northern middle part. Foam shop was Poly Foam now called Plasti-Fab.
if I can make a hot wire cutter…
I’ve been shaping boards for a few years and have made a variety of hot wire cutters. You only need three things:
Nichrome wire - buy it on Amazon, 24 gauge, 100’ for about US$12. You can salvage nichrome wire from old toasters - don’t do it. New 24 gauge wire is cleaner, stronger and provides a superior cut.
Power source - Longwei DC Power Supply Variable,30V 10A 4 Digital LED Display Adjustable Regulated Switching Power Supply Digital with Leads Power Cord (30V 10A Black) - about $US60 on Amazon. I experimented with batteries and chargers for a power source, the proper power source makes life much easier.
Scrap lumber - use it to hold a span of wire. You’ll need some kind of spring or bungee to tension the wire as the wire stretches and sags as soon as you heat it.
Check out this video https://www.youtube.com/watch?v=eGRgev05Hyg&t=1179s
Disregard that the topic is how to build a downwind board. At about the 1:55 minute mark he shows how he uses a hot wire cutter. You’ll see the Longwei power supply and you’ll see his homemade wire cutter(s).
You’ll also see how to achieve a thicker blank by gluing two thinner sheets together.
Good luck and have fun with your build.
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@Graeme1 thanks for the video and information.
Point of clarification, he glues the EPS for length and not thickness, and he was careful not to put PU glue in the path of the hot wire. This would be difficult to manage if gluing for thickness. The glue makes a hard spot for shaping/sanding and releases isocyanates as cut by the hot wire.
The whole masonite-less rocker procedure was brilliant. I had forgotten about the tape trick. The only downside to his methods is having to sand more to get back to the lines rather than cutting closer to them.
https://jacobs-online.biz/ is a great site for wire and information.
You’re welcome, and thanks for the link.
I’ve watched a few videos about gluing foam, I forgot that MatG glued for length.
I glued for thickness on a recent board. Keeping PU glue out of the hot wire area is good technique. I’ve also had success with 3M spray adhesive to glue foam together, it does not seem to impact hot wire cutting.
I’m not sure you get as good a bond with spray adhesive but I don’t think the bond is as critical when gluing for thickness. The glue holds the foam together until it is glassed then the foam acts more as a core and the glass provides the strength.
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I appreciate all the input everyone, there is much information here.
My attention now turns to sourcing foam: Where I am in the world, Victoria, Australia, I have found (extensive phone calls and emails) that it is probably only 25%, if that, more expensive to buy a PU blank than a Polyurethane sheet (or two depending on thickness).
EPS blanks are less available where I am and EPS sheets are more readily available, but the density to make it economical and worthwhile would be a ‘medium density EPS at around 19 kg/m3’.
Not sure about the rest of the world.
Hey Chris,
Have you tried The Foam Company, a mate who used to live in Aus used them. I think they are in Victoria and do high density?
Hi Railwaysurfer
I have about a 20 email chain with the Foam Company over the last fortnight.
They have two options:
-
Rigid PU foam (35 kg/m) that is only economical if you buy it in a block that would make about 12 boards: 2400 X 1200 (which I would cut in 120mm thickness) X 600 which is $AUD 2,100.
The price for smaller means it is only about 25% dearer to get a real blank (Martini Fibreglass for me in Geelong/ -
EPS sheets.
Medium density is 19 kg/m3
High density is 24 kg/m3
This is about half the price of a PU blank and is worth considering.
The Foam Company weren’t sure if it could be glassed. It sounds like it can. I think I would use the shapers or another brank foam sealer over the EPS before glassing.
Their $400 minimum order doesn’t help. I will have to buy about $450 of the medium grade which could be made into 4 boards. Basically.
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Oh well that’s annoying. We have a few companies over here (NZ) that do the 24kg or higher but I can buy 1 sheet if I want! They have a minimum freight charge which means you can get up to 4 sheets. Pretty sure all EPS can be glassed?
Yes, EPS can be shaped nicely by hot wire and glassed with epoxy resin.
PU is better shaped by other methods and can be glassed with PE (polyester) or epoxy resin.
I would not recommend low VOC PE or any other ‘home remedies’ to coat the foam to attempt to use PE resin on EPS. I did a couple boards early on with a low VOC PE resin designed for EPS that had a brown tint when cured and were later discovered to have flawed fin box installs from the resin eating the foam. If possible stick with ‘surfboard’ grade resins and cloth. The lower cost options seem attractive but usually come with a quality or work-ability penalty.
Why not try this:
- Make a stringer out of plywood, shape it to the exact rocker you want
- Cut your blank in half length-wise
- Glue both parts to the stringer, EPS will easily bind to the stringer’s curves and will retain this rocker when glue has cured.
We used to do that in 1968 in France when foam blanks were not available yet. A company building isothermic trucks would sell us 100 mm thick rectangular sheets of PU foam and we would put some rocker in them by using this method.
Actualy been thinking about doing that, now the salvaged EPS i got measures.
I have 3 pieces of 70cms x 100cms x 15 cms
2 questions?
1- best way to cut the pieces of foam on order to glue them to get a 250 cms pieces.
Many horizontal pieces? Vertical pieces?
Lenght of pieces to cut etc…
2- what glue to use? For foam on foam and foam on wood?
Cheers and good waves?
250 x ??? x ??? Seems like there is only one way to go:
Picture is similar to how MatG did in video except 3 pieces instead of 2.
Try to plan that you are not hot wire cutting through lots of glue.
I have used foaming PU (Gorilla Glue) and epoxy for EPS to wood. I cut the stringers and rocker ‘sled’ into the EPS first (no bending)
Edit: It can get messy adding a stringer at home, might want to oversize and ‘skin’ rather than hope it all turns out perfect.
Edit 2: I don’t think I have ever hot wired through an epoxy foam-to-foam joint, only foaming PU glue.
Ok.
What software did you use to make such a nice drawing?
Please take a look at my sketch, because on my head the way i was going to do it made much more sense.
So the problem is that by doing it this way i will run into much more glue?
Cheers and good waves
@arlosilva
The software is Rhino3D.
What size of block are you trying to make from (3) pieces 70 x100 x 15cm?
Maybe I have misunderstood your ?
The more glue lines the more trouble cutting and sanding later on.