I have the opportunity to get a heap of eps sheets 90 mm x 1mtr x 4mtr . And I have looked at every board making site possible I have a good understanding of the difficulty & time involved .
I have the shed & tools & skill with tools and I feel confidante that i should be able to do a reasonable job . I will have to make a hot knife but that's no problem. What I don't have is an understanding of the finer aspects of board design .
So I'm making this appeal in the hope I could be directed to a book or website or tech course that could give me a better understanding of this or the diminsions of current boards .
Even if I don't end up making boards out of it & I just use it to line the shed with I would still like to know more about board design so I can understand what happens when subtle changes are made with the new models. I would like to start with a board about 120ltr & then do a board about 70ltr .I'm 70kg I thought about doing the 70ltr 1st but it just wouldnt get used that much in sydney so I would have a long wait to be able to use it & I think that the smaller board would be less forgiving if the design was wrong I could be wrong thats just my thoughts. So any help would be greatly apreciated .
Thank you
Max

there is a lot in your question. and to much too handle on a forum, i say just go for it.

check out as many surfboard design webites as you can for info on rails, rocker and terminology.

there is a free 3d software package i use called boardcad. you can download it off the net.

the other item is the foam you've listed is almost too thin. you will struggle to get your volume with a reasonable width unless you laminate 2 sheets to make a 200 thick block. not ideal but very possible.

are you using polyester or epoxy? what resin is suitable for the foam you have? vac bag construction requires jigs to prevent the rocker from deforming while bagging.

keep asking questions here as you go and don't be afraid to take your straight edge and tape to the beach and measure every board you find.

Gesty's right, 90m is a bit thin, most of my boards come out of 150mm blocks. eps will bend but that gets a bit complicated.

I've been shaping boards for over 25 years now and I'm still learning what tiny little changes do to a boards performance.
When starting out I read a quote by an awesome shaper Jimmy Lewis who said get hold of the best board you can and copy it!
My first few boards were pigs to look at, went ok but rail shapes were very lumpy.
swaylocks.com would be your best bet for info and help it is for surboards but similar principles.
This is really, really basic generalization and is an example of extremes at two opposite ends, a flat ish rocker (which is the bottom curve of the board from nose to tail), planes early,stiff to turn and is fast, whereas a very curvey rocker is slow to plane, can be slow as it is pushing water but super easy to turn. a good board finds the balance between these two extreme to suit the characteristics you want from a board.
The outline also affects turning and planing as does the width.
The bottom or the rails determine how easily water is released from them and the thickness how easy or hard they can be pushed into the water during a turn depending on the riders weight.
It gets a lot more complex.
Just copy a board and go for it!

He's got eps so it will have to be epoxy.

thanks people it will be epoxy i have some & probably 1mtr2 of carbon fiber already i also have klegi cell for fin box mast track foot straps . Don't mind about jigs I'm used to making jigs for jobs . I would glue the blocks together contact cement was a glue mentioned as it could still be cut with a hot knife & no have a hard spot for shaping. I was sort of wondering Is there a ratio between length of board & mast & fin & foot strap positions or is the track always set for the 1350mm mark . I like your suggestion gestalt I will start to measure boards . I might hire 1 just to measure when i get a bit closer to making it . I have a mike davis fiberglass tri fin that i feel is really close to the modern tri fin shape but the mast track is wrong position glass is pretty smashed & the foot straps are some cobre things i cant get so i might strip that & practice on that first . I will have to wait as work has been really slow so low in funds at the moment but it will come in time i just like to follow decartes theory throughly review the problem breaking it down into smaller pieces until the solution is clear & distince in my mind . I find the more i study the less problems I have. I did think that there might be a table of sizes of boards somewhere.

these are all approximates

rear of finbox - 100mm from tail
foot straps 500mm apart
strap plugs approx 150mm appart.
rear of mast track 1250mm from tail.

position of straps to finbox is dependant of rocker/fin/board type

important dimensions

wide point from tail
tail width at one foot off

aspects to focus on are rocker, 3d volume distribution, position/length of planing flat, rails.

edit,,,, i wanted add, when designing somehting from scratch, it's almost impossible to produce the perfect design first build. it takes a minimum of 2-3 protos to get close to the mark if you have a firm idea of what works and what doesn't. the best way forward is to design your board in 3d, do as many revisions as needed, then build your board and make tweaks to that model after sailing it so you are always moving in a forward direction and you have something to compare each change to on the water.

experienced shapers have templates they know work for particular conditions or design briefs and they make small tweaks from there to suit the individuals needs.

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actiomax said...

I would glue the blocks together contact cement was a glue mentioned as it could still be cut with a hot knife & no have a hard spot for shaping.

contact will melt the foam

i dont believe everyone is encouraging actionmax to go ahead with this project it's like some gives you some windows and door's and you design a house because you got the stuff free
in my opinion the hole project is starting off on the wrong foot because the blank has to be joined, no matter what you call it that means extra weight, the whole idea is to keep the weight down not to mention how much stuff what ever your useing do you need to make sure you have a perfect bond, thats a lot of area to cover not to mention the glue line, no matter how hard you try your always going to get a high on the glue line,
i dont know what the answer is to the rest of your questions because i wouldnt even start the project

ok so one blank is 90 mm x 1mtr x 4mtr , what you do is make a high wind flat water speed board, get your blank and chop it too 90x500x4mt then you chop that to 250x4mts stand the blank on its edge and using some house bricks or anything you can get you bend the rocker into the blank
next step ......., mark out the thickness of speed board (tail to rocker) bet some 200gr uni carbon and make sure the grain is longitudinal using a wheel make the stringer
next step........ after that has set you have 250 blank with carbon stringer now get the other 250 stick it on the ground and put the bent blank on top and bend the bottom 1/2 to the same as the the top, get some resin and join the 2 blanks
next step now you have a blank with a carbon stringer and because the carbon grain is longitudinal the blank is incredibly stiff
next step.......all you need to do is sand down to your stringer remembering to keep every thing square
you will end up with a speed board that you dont want but its better than haveing a board that doomed for the tip
"edit" if you need a more thickness its easy to add it just where you need it but do it before do the stringer

honestly keef, that's shocking advice

boards aren't built that way.

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keef said...

ok so one blank is 90 mm x 1mtr x 4mtr , what you do is make a high wind flat water speed board, get your blank and chop it too 90x500x4mt then you chop that to 250x4mts stand the blank on its edge and using some house bricks or anything you can get you bend the rocker into the blank
next step ......., mark out the thickness of speed board (tail to rocker) bet some 200gr uni carbon and make sure the grain is longitudinal using a wheel make the stringer
next step........ after that has set you have 250 blank with carbon stringer now get the other 250 stick it on the ground and put the bent blank on top and bend the bottom 1/2 to the same as the the top, get some resin and join the 2 blanks
next step now you have a blank with a carbon stringer and because the carbon grain is longitudinal the blank is incredibly stiff
next step.......all you need to do is sand down to your stringer remembering to keep every thing square
you will end up with a speed board that you dont want but its better than haveing a board that doomed for the tip
"edit" if you need a more thickness its easy to add it just where you need it but do it before do the stringer

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Gestalt said...

honestly keef, that's shocking advice

boards aren't built that way.

keef said...

hehehehehehehhehe well how else do you put a rocker into a piece of 90mm flat piece of styrene or make a blank with rocker and still keep it 90mm thick i made this board in the 80's from a flat block of styrene 600x200x3mt 2 position adjustable daggar board how would you do it, if you can come up with a better way ill donate a speed strap too the fastest custom board at burrum and you can take back your red thumb

yeah in the 80's board were hand shaped from pre rockered blanks and finished in polyester.

now blanks are cut from foam blocks with hot wire and templates, rails, concaves are hand finished then the whole thing gets vacuum bagged on a jig.

this is one of the fallacies in windsurfing. that custom boards are not as accurate as production boards. when in fact they are all made the same way. to template or on 3d cutting machines. only difference being laminate makeup and resin amounts.

stringers are not really laid between 2 halves of a blank anymore either. wave boards still use them but most slalom/speed boards the stringer is a carbon strip laminated to the bottom or deck of the board.

i don't like stiff, i prefer veneer, the board feels nicer and is more forgiving.

so if actionmax wants to build a board. he would laminate 2 pieces of 90mm thick foam together giving him a 180x1000x4000 piece of foam and then use plywood stencils to hot wire the rocker and plan shapes. or 3 pieces and end up with 270mm

if the resin joint of the board is a problem then use a knife to trim it back. the only issue you get is the joint between the 2 blocks of foam can loose some of the foam during shaping. you can use some filler to make it true again.

other than that, he can do what some on this forum do. design the board and get a recognised shaper to build it.

think of the foam as permanent formwork. it has no real structural integrity.

edit, anyways, the foam is the cheap part. just buy another block if it's that much of an issue.

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Gestalt said...

yeah in the 80's board were hand shaped from pre rockered blanks and finished in polyester.



stringers are not really laid between 2 halves of a blank anymore either. wave boards still use them but most slalom/speed boards the stringer is a carbon strip laminated to the bottom or deck of the board.

i don't like stiff, i prefer veneer, the board feels nicer and is more forgiving.

so if actionmax wants to build a board. he would laminate 2 pieces of 90mm thick foam together giving him a 180x1000x4000 piece of foam and then use plywood stencils to hot wire the rocker and plan shapes. or 3 pieces and end up with 270mm

if the resin joint of the board is a problem then use a knife to trim it back. the only issue you get is the joint between the 2 blocks of foam can loose some of the foam during shaping. you can use some filler to make it true again.

other than that, he can do what some on this forum do. design the board and get a recognised shaper to build it.

think of the foam as permanent formwork. it has no real structural integrity.

edit, anyways, the foam is the cheap part. just buy another block if it's that much of an issue.

sounds like your haveing a bad day gesty whats the problem no wind up your way

lol, nope not a bloody drop.

plus i'm working currently to get stuff finished off.

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Gestalt said...




stringers are not really laid between 2 halves of a blank anymore either. wave boards still use them but most slalom/speed boards the stringer is a carbon strip laminated to the bottom or deck of the board.

so whats a strip of carbon going to do

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Gestalt said...


so if actionmax wants to build a board. he would laminate 2 pieces of 90mm thick foam together giving him a 180x1000x4000 piece of foam and then use plywood stencils to hot wire the rocker and plan shapes. or 3 pieces and end up with 270mm

i dont think so

gesty. my 95lt ca55 is 100 thick if actiomax does as i said and gets the two 1/2's perfectly square he has a blank with exactly the rocker he wants ( that's as long as he lets the stringer completely cure)all he needs to do is lightly v the bottom and top and roll the rails, the blank is still 90mm now add 8mm for divinicell you have 98mm
the carbon stringer would way buggar all for e,g the nose is 30mm,at 600 from the nose it is 70mm thick at 100 from the nose it is 90mm and the thickest is 100mm then gradually going down to the tail "thats the ca55's rocker"
what your saying it to join the 2 pieces or 3 for the hole width of the board and then hotwire it so are you expecting the hotwire to go through what ever you have glued it with i dont think sooooooooo
actiomax said he also wants to make a 70lt board well here's his opportunity
you there is an advantage of doing the blank with the stringer and that is less chance of the board's rocker changeing while in the vac bag
the way i see it as for giveing bad advise you should think about what your posting before hitting the send button

If you want to glue 2 pieces of eps together use water based contact adhesive. Not the most ideal way to do it but it will be okay. The hot wire will go through it no worries.
You can bend the rocker into an eps blank but it it will always be a whole lot easier and more accurate if you have enough foam to cut it exactly.
Get into it and have some fun doing it. Riding a board you have created your self is a cool thing to do.

As an exercise, it could be quite interesting to do, but i wouldn't hold out much hope of the board working well.

There are several grades of EPS. When I built a board from it I used a higher density fire-retardant grade because it was much better for sanding. The lightest grades tend to rip bits out of the surface when you sand and would retain a lot of resin during layup due to the coarse grain. I got them to tilt a block up and feed it horizontally past the hot wire to give me two wedge shaped blocks.

Epoxy needs about 20 to 25C and you need to have the core at that temperature for a while before layup otherwise air will expand out of the core under the layup if you put the heat on too late - like I did.

I've made a couple of boards with joins and have to agree with keef on this one gesty.

Unless there's a hot wire-able glue that doesn't melt eps!

Guess with a bit of inventiveness you could hot wire the bits separately then glue them together, but that doesn't seem all that easy.

And sanding across the join is always a pain. there's bound to be a difference in abrasive resistance.

I've also made boards by bending the foam, and the rocker hasn't come out quite as I wanted.
Keef's idea of a carbon stringer could be the answer.
I'd taper the front off first, that should make bending easier, as would getting some heat into it, boiling water probably the safest, (for the foam anyway).

A 120 litre board should be possible at 98mm thick, just needs to be wide and long enough.

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terminal said...

As an exercise, it could be quite interesting to do, but i wouldn't hold out much hope of the board working well.

There are several grades of EPS. When I built a board from it I used a higher density fire-retardant grade because it was much better for sanding. The lightest grades tend to rip bits out of the surface when you sand and would retain a lot of resin during layup due to the coarse grain. I got them to tilt a block up and feed it horizontally past the hot wire to give me two wedge shaped blocks.

Epoxy needs about 20 to 25C and you need to have the core at that temperature for a while before layup otherwise air will expand out of the core under the layup if you put the heat on too late - like I did.

I disagree, the lightest grades do tend to shed there cells, with coarse grade sanding, but with careful fine sanding aren't so bad.

Resin retention isn't a problem if you wet out the cloth on the bench first. And low temperature isn't a problem in most of Australia. I've never had problems with epoxy going off in the middle of winter, with temps down to 10C. Just takes a bit longer, (about 8hrs) you have to be patient and have an on/off vacuum regulator with a bit of a reservoir, mine turns on for about 3s every couple of minutes.
The only thing that needs heating is the divinycell to bend it round the rails.

it's posibble to use a combination of hand saw and hotwire.
or use the glue that hoops recomended.

another question is what density is the eps? isn't 14kg/m2 what should be used.

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decrepit said...

I've made a couple of boards with joins and have to agree with keef on this one gesty.

Unless there's a hot wire-able glue that doesn't melt eps!

Guess with a bit of inventiveness you could hot wire the bits separately then glue them together, but that doesn't seem all that easy.

And sanding across the join is always a pain. there's bound to be a difference in abrasive resistance.

I've also made boards by bending the foam, and the rocker hasn't come out quite as I wanted.
Keef's idea of a carbon stringer could be the answer.
I'd taper the front off first, that should make bending easier, as would getting some heat into it, boiling water probably the safest, (for the foam anyway).

A 120 litre board should be possible at 98mm thick, just needs to be wide and long enough.

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decrepit said...

I've made a couple of boards with joins and have to agree with keef on this one gesty.
I've also made boards by bending the foam, and the rocker hasn't come out quite as I wanted.
Keef's idea of a carbon stringer could be the answer.
I'd taper the front off first, that should make bending easier, as would getting some heat into it, boiling water probably the safest, (for the foam anyway).

A 120 litre board should be possible at 98mm thick, just needs to be wide and long enough.

decrep bending isnt a problem i used to use 3 car tyres , one on the tail ,one on the other side where you want it and the other at the front same side as the tail and bend the front till the rocker is where you want it, 90mm shouldn't need much pressure,the uni carbon has to be horizontal and let it cure so the blank does not spring back when its cured, as long as you have the thickest part flat there's no reason you couldn't keep the blank at 90mm , doing it that way your going to get an extra blank incase you stuff the first one up
"edit" decrepit if you can come up with a better way to do it ill make you a speed strap for that new board your doing
.

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Gestalt said...

it's posibble to use a combination of hand saw and hotwire.
or use the glue that hoops recomended.

another question is what density is the eps? isn't 14kg/m2 what should be used.

yes that is possible to use a hotwire and hand saw, use the hotwire untill you get to the glue then turn the hotwire off,then use the hand saw and continue too the next glue joint gesty i respect hoop and congratulate him on his boards but i would question any glue, even useing the fattest guitar string you could find there would have to be a hesitation with the wire on the glue opps next blank
i use 11kgs/m2 its fine

keef, depending on how much rocker the board has you "may" be able to position the rocker template so that the join in the foam doesn't require cutting at all.

then you use a saw to cut out the outline.

with respect, it's certainly more accurate then using car tyres. at least if you are going to use car tyres use a jig to ensure your rocker is fair.

carbon strips in the horizontal plane work as stringers when under tension. like when landing a jump

Keef, it's just a personal thing with me, I don't like stringers and try to avoid them, even if my alternative doesn't seem as efficient.

Gestie, can't see how you could add extra foam thickness, without having to cut the rocker line through it.?

OK, I think I see, would have to be a line between bottom of tail and end of nose I guess, not very intuitive, bit of lateral thinking there mate.
I think you may have solved it!!!! But it is a big join, glue weight is going to be a factor.
My joins have just been through a small section of the nose.

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decrepit said...

Keep, it's just a personal thing with me, I don't like stringers and try to avoid them, even if my alternative doesn't seem as efficient.

Gestie, can't see how you could add extra foam thickness, without having to cut the rocker line through it.?

OK, I think I see, would have to be a line between bottom of tail and end of nose I guess, not very intuitive, bit of lateral thinking there mate.
I think you may have solved it!!!! But it is a big join, glue weight is going to be a factor.

ok so now we are getting away from laminateing two flat pieces together and working on bending a piece of foam say 250x800x90ml how about we bend the blank on its edge remembering this is only thin foam and will bend easy, we use a piece of 10mm divinycell say 30 or 40 cm long using a router on the stress or bend
and rout down 5cm, no jam the piece of divi in to the cavity and mark it with a text now cut the uni carbon and wet it out and wedge the carbon in so the strands are horizontal and let it cure
the trick is to use a wheel and when wetting out mainly go down the strands if you go across you will spreed the fibers and make the laminator and also you need to just keep working it until the resin goes white, i'm not sure why it goes white but i think its either moisture or something they while making it , alway remember to keep your carbon covered or it will go stiff and that means moisture

I didn't think that gluing the blocks together would be such a massive problem after all I have just seen a board widened on this forum & I imagined that it was glued in some way . Starting to look to hard for me now Ill wait until I get the eps & then see how I feel . I've got blocks of the fire retardant stuff I've used that to line the walls of the shed & its heaps heavier . When they metal skin the eps for roofing they use contact cement well that's what it looks like . And just a small note if i was building a house & someone gave me the windows I would design around that as glass is much more expensive than brick. I will strip & do the glass board I've got & see how that goes first . If it totally sucks well that will be the end of my board building . Thank you for the advice everybody

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keef said...

>>>>>

ok so now we are getting away from laminateing two flat pieces together >>>>>

Hang on Keef, I think gestie's method may have merit, granted it's a very big join, the extra weight would have to be calculated and taken into account.
And there would be a join all the way round the rails making shaping them harder.
Probably a test piece to work out extra weight and shaping difficulties, would indicate if this is a practical method.




Actionmax, think it was hoop who said there's a water based contact cement that's OK.
I wouldn't give up just yet, as above gestie's idea of making the join on a line from the nose tip to bottom of the tail, doesn't involve hot wiring the glue line.
Try making a small model to test weight of glue and shaping ability. It's the final smoothing phase that causes the most trouble. The glue line doesn't abrade as fast and leaves a raised line along the join. The trick is to use a blade of some sort to cut this off, but eps can shed cells when cut with a blade.

The board that was widened was probably joined with epoxy, and wouldn't have been hot wired afterwards.

The "glass" board (I hate that description, it's almost meaningless, there's not many boards around that haven't got glass in them, I prefer the more accurate description polyurethane/polyester), having polyurethane foam construction will have different shaping characteristics to your eps.

I've joined EPS with the thinnest layer of epoxy and qcell (vac bagged)I made i very very thick mix.
Just held my breath when the hot wire cut through it, as the epoxy stinks and is probably toxic at that heat.
That fire retardant styrofoam is probably about 45kg/m whereas the eps is usually 12 to 15kg/m I've used a contact cement designed for the fire retardant foam.

Rider, how did you apply the epoxy/qcell?
Every time I've tried a thin stiff mix, it's dragged the cells out of the foam.

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actiomax said...

I didn't think that gluing the blocks together would be such a massive problem after all I have just seen a board widened on this forum & I imagined that it was glued in some way . Starting to look to hard for me now Ill wait until I get the eps & then see how I feel . I've got blocks of the fire retardant stuff I've used that to line the walls of the shed & its heaps heavier . When they metal skin the eps for roofing they use contact cement well that's what it looks like . And just a small note if i was building a house & someone gave me the windows I would design around that as glass is much more expensive than brick. I will strip & do the glass board I've got & see how that goes first . If it totally sucks well that will be the end of my board building . Thank you for the advice everybody

I used two-part urethane foam to form the extra width. It also sticks to styrofoam like the proverbial, but as its an expanding foam, you would need to pour it on, scrape most of it off, and then lay the next block of styrofoam on top if you were trying to stick two blocks together without creating a gap.

I am not sure if a hotwire would cut it, but its not very dense, so I think it might work.

In my board widening I spaced the board bits apart using timber, used some flat plastic on the bottom, and then added the pour foam. The excess that rose above the board was then cut off with a hand saw.

I am not sure if its been mentioned, but can you just bond the block together in the middle only, where you don't need to cut into the glue-line? I.e. glue a space narrower and shorter than the final boards dimensions? (edit: I see it has been mentioned)

(Normal) Contact cement will melt polystyrene. The water based stuff won't but in my experience won't go off unless it is in a very thin layer.

Another dodgy way to glue small bits of polystyrene together is hot melt glue, just don't use too much or it melts the foam...