Another EPS technique?

Anyone try this yet?

My bro and I have been toying around with the EPS idea but realize that shaping 1"-2" one pound EPS will be very difficult because it’s so floppy. Also everyone has a different idea about how to set the rocker so we thought up this idea.

  1. cut out your stringer like normal (Probably need a thicker than normal)

  2. horizantally split the stringer 50-50 or even 30-70

  3. sandwich/glue a 1/16"-1/8" 2’by ## sheet of wood(door skins?) between the two stringer pieces horizontally

  4. now glue under vacuum 4 sheets of EPS to the left top and bottom and right top and bottom sandwiching the stringer in between like normal.

The flat thin wood sheet and EPS sheets could be outline cut before their respected glueups.

The variable splitting of the rocker allows you to put a 1" EPS sheet on the bottom and a 1.5"-2" EPS sheet on the top to hopefully keep the horizontal wood coming out to the rail and not the deck after shaping the rails.

We think this will:

  1. Automatically create the EPS rocker from the horizontal wood panel.

  2. Add enough stiffness to make shaping the foam easier.

  3. Set the thickness line(stringer) to cut the foam down with or without using a hot wire cutter.

  4. Provide some additional vertical stiffness with a triple horizontal sandwhich of glass-EPS-wood-EPS-glass while still providing for some vertical flex.

  5. Crank up the torsion stiffness with the (+) internal wood support between the foam.

Yea it’ll add weight but we could probably use thinner sheets of the EPS.

Anyway we’re getting setup to start this project with the first step being building one of those long rocker profile jigs so we can capture draw and cut out our stringers alot easier than trying to trace the side profile of an existing board.

We think it should make doing boards out of 1lb 1"-1.5 EPS alot easier and hopefull alot stronger…

Just doing a reality check here before we atrt though…

Are we offbase with our thinking here?

Bert?

Not saying your idea is good or bad…

But you can easily shape 3/4 lbs. EPS by laying the blank ON a rocker table, shape right from it the whole deck, then flip it over on a stand to shape the bottom.

You can even glass the deck patch on the deck before flipping the blank over. The single layer 4oz patch holds the rocker better than any stringer.

I know little of horizontal stringers. Maybe it won’t hold any rocker under any pressure. MAYBE…

thats a technique alright…

hotwiring foam is the way to go…put in a normal stringer and modify your shaping stands to better support your blank

Here’s another idea; 1. cut your vertical stringer out to finish shape but leave small tabs 12" from the nose, tail, and wide point about

1/4" oversized that you will sand off later . 2. lay the stringer down on the foam and some ply wood and use it as a template. 3. trace the stringer shape onto the foam and plywood and cut 1/4" oversized. 4. set it up for glue up on a flat surface that supports within reach of the tabs. stack some strips of wood, that lay perpendicular to the stringer and bond-lines, until they meet the tab height (your rocker) 5. put a thin coat of 3M Super 77(or urethane glue, i.e. gorilla) on both faces of the foam and glue it to the stringer. 6. clamp it all together using the plywood strips as clamping blocks. (do a dry clamp test run first) The tabs and oversized surface of the foam will register on the perpendicular strips of wood eliminating twist and warp. 7. let sit overnight and sand down to the stringer.

do it , i think youll be surprised how stiff it becomes , just use glass , itll add better compression and tensile properties to the whole structure …(wood will as well , but thats overkill , unless the wood resembles a horizontal stringer and doesnt show )

make the join between the top and bottom sheets so its sits right on the apex of your rails ,(youll be glad you did later at shaping time ) that means the bottom sheet will vary in thickness…

dont complicate things with a vertical stringer , your already on the right track , get the concept of a conventional surfboard out of your brain so it doesnt cloud your thinking …

sometimes when were exposed to new ways of thinking , the thing that stops our progress the most is our old way of thinking …

do what seems logical with the process and dont try and incorparate traditional methods , that will only complicate things …

elementry my dear watson …

oneula sleuth of the year…

regards

BERT

I think its a good idea. I’d even put the thinner 1" - or even 1/2" - EPS on the top of the flat wood and the thick one on the underside. Less foam = less compression = less mushy. If you use a sheet of 4 oz glass with epoxy to glue the flat wood to a thin top piece of EPS, once you glassed the deck you’d basically have a sandwich skin construction…

Okay we’ve decided to scrap the center stinger and instead cut two 2"x8"x8’ pine boards with the bottom profile then screw on a sheet of 2’x4’ 1/4" ply to build a bottom rocker table then lay down the EPS, 1/8 Lauan Mahogany door skin, EPS sandwhich glued with epoxy and “maybe” some glass. Using the other half of the rocker cut pine with 2’x4’ 1/4" plywood attached by screws as a top piece and clamp the top and bottom rocker halves togethor with the foam-wood-foam sandwhich in between. This is non-vac stuff at this point.

Remove the foam-wood-foam sandwhich hereby only known as FWFS and shave the top or bottom layer to the desired tapered thickness.

Cut the FWFS outline and finish rails and bottom contour.

Then lam the FWFS top and bottom wood OR…

Lam wood rails with top and bottom lam to the FWFS and shape the rails later

Glass and finish the rest as normal with a wood lam board.

Building a variable rocker table must be difficult as we’ve had a heck of a time with our rocker stick today. Somehow the vertical shafts have to move horizontal to support the changing curve and the locking upper bar or panel has to support this movement somehow. We figured the top and bottom bars must have integrated channels that allow the vertical bars the ability to rotate horizontally within the channel and still be able to be locked downed.

Should’ve just bought one from the Australian website with the amount of time we spent today making ours work…

I gotta admit, there’s a lot of creativity here…I’ve had similar thoughts in the last few months…BUT…I have a specific goal of making a strong and light board of less than 6lb…everytime I get a similar idea I whip out the scales…after some testing I scrap about 5 ideas for every one that I attempt to implement. If low weight is a primary objective, thin ply will be a challenge…for a shortie the ply alone weighs about 2lb+…I guess Im one of those who like to plan and test approaches, with a specific goal in mind, before building…call me kooky but I gotta manage my spare time. Oneula may not have ultra-lightweight goals…surfing in HI, I dont blame him at all for that…

PS - I own three scales one of them with a resolution of 0.1 gram…I weigh and extrapolate…saves a lot of time down the road…I’ve had a ton of similar ideas that I dont discuss…in the end I went with the hotwire…like Greg’s New Blank…Im still waiting for those blanks from Greg…maybe after he’s done with the website he can tackle that one…