stringerless blank ...

Two thoughts…

The stringered board/blank has been stripped, so it has lost foam from the deck and will be more likely to dent. Extra glass in the areas where the stress will be worst (knees, feet, etc) will be in order.

The stringerless is EPS (or XPS) insulation foam correct? you cannot poly-laminate direct on these foams (poly resin will eat the foam). Either epoxy lam, or, first paint with latex paint - two thin coats - then you can use polyester.

go get 'um.

Eric J

Hi Eric !

no, the stringerless is actually polyurethane. So, I can polyester it. I just thought if I made it thin [to flex], I'd be needing some sort of extra strong glass job... hence the thought of epoxy. 

But now I’ve got the thin stringered blank…maybe that will be epoxied ?

All the microballoon talk has confused me though, I have no idea what they are… I was hoping I could just laminate epoxy straight onto the blank ? And spraypaint the foam before glassing, like I do with the polyurethanes I’ve made ?

      okay, thanks ... 



         ben

After a few more sessions on my Home Depot / epoxy longboard ($14 blank thread) I’ve realized its flexing more & more. That foam really is super light & not very strong. Its a fine filler for a lot of glass, and it still surfs well, but it paddles poorly - loses energy to flexing (bouncing) instead of forward progress. (Ironically, I’m almost exactly the same dim.s as Oceans23, the other Home Depot/Elmers blank builder - 35, 6’2", 215). I’m thinking of adding a layer of carbon fiber or kevlar glass to the bottom to stiffen it up. Still don’t have (much of) a problem with heel dents, although my knee-paddle spots are clearly evident. The stringer is just two pieces of 1/8" door skin glued together with wood glue. With the foam I have left over, I’ve started a 7’11" double ender and I think I’m going to do a 2" thick balsa stringer a la Ole or Dewey Webber to try to stiffen it up a bit…and even then maybe use multiple layers of 10 oz Volan instead of the 7 oz I used last time…Yeah, I like my boards on the heavy side.

so , please tell me fellow ben man…

how does the flex FEEL …is it kind of mushy feeling say when you do a bottom turn ?

Noticeable when you are trimming or cutting back ? These are the sort of things I want to discover with the stringerless…I’m still undecided at the moment whether to make it another thick board and polyester it, or go thin and epoxy it.

Bluejuice, hicksy, bert …what / where do you recommend for epoxy, please ? [I’m in scarborough]

      thanks ! 



        ben

Its funny, I don’t really feel the flex when surfing. Of course, its a totally flat bottom and has hard rails in the back, so I’m planing pretty good. If it was egg-railed or veed, I’d bet it’d load up when I bury a rail and then flex out as I uncork it. It responds well to kick stalls - if I stomp my weight to the back foot I can actually feel the tail flexing down as the nose comes up - but trimming over the thick spot in the middle, it feels solid as can be. Its just the paddling that feels like riding a suspension mountain bike up hill - more bounce than I like. Remember, though, its a 10’1"…

Ben,

Microballons and spackle are for EPS blanks only - that is the beaded foam. Since the foam is beaded, and has some voids between the beads, you need to fill those voids to keep a lot of resin from being absorbed into the blank. The absorbed resin can makes the board unnecessarly heavy and does not really add to strength.

Poly and xps foam are not beaded. instead of tiny beads OF foam you have tiny-er bubbles IN foam. in these blanks shaping only breaks the bubbles, or cuts them in 1/2 but since the ‘walls’ between the spaces are solid, resin cannot be absorbed very much into the blank.

Not too clear an explanation I’m sure, but I hope that helps. however - it does not sound like you have the need to fill/spackle. Just laminate as normal with epoxy - if you go that way. I painted on my epoxy/xps board and it worked out fine. Just use water-based or acrylic paints… and/or test it first on some scrap foam. How much would it stink to have a nicely shaped blank and watch it dissolve with paint that’s incompatible.

Epoxy should be fine over the paint, but not too thick - thick paint will cause you problems, whatever you lam with.

I’ll stop now. hope you build these boards, I want to see them done, and hear how they go now.

Best

Eric J

Eric J, and oceans and bert,

thanks very much for all your input . Eric, if you want, I could send you a 'pm' with a photo or two as I [hopefully!] 'progress' in this... 

My shaping and glassing skills are sad, to say the least. [But, without the practice, how would / will they ever improve ??]

I guess it’s the flex [or not], and the epoxy resin process[es] that I want to try out this time around. I’m not sure 5’9 x 18 x 2 3/8 were the dimensions I really wanted to start with, but that’s what I ended up with now the tail and fin snapped, stripping the ol’ single ! I really need to work from a new blank…maybe NEXT time !

Now, to the epoxy resin…

On say, a 70-80 degree day, how long am I looking at for it to "go off " enough to allow me to flip the board , baste the laps [if needed], and glass the other side ? Fortunately, Perth does not get really humid this time of year [our spring].

Question 2 : -

How much less noticeable/ obnoxious is the smell than polyester ? I’m laminating in a block of flats [‘apartments’], so wouldn’t want a bad smell lingering longer than the polyester does !

Thanks for your help everyone who has contributed! 



        ben 

ps - the stringered blank I’m working on [slowly… very very slowly…] at the moment has a 13 1/2" nose and a 12 1/2 "tail, it’s a rounded pin. I wanted to leave those parts fairly wide to help with a bit of float, hopefully.

I’m used to a 7’ x 20 x 2 7/8" single fin, and a 5’11 x 20 x 2 1/2 fish - the 2 boards I ride the most from the quiver.

[Probably why I was thinking of the ‘mid-range’ / averaged size of the 6’4 x 20 x 2 1/2 [Cooper photo ] template for the stringerless polyurethane blank , I guess. My next project…]

Ben,

I can only answer your questions here if you use RR epoxy. Otherwise you need to see what you get.

RR epoxy - with the fast hardener - I give about 1 hour till time to flip. In optimum conditions.

The Smell of this epoxy is almost non-existent. I forget to put on the mask when using it and I doubt, if you have some ventilation, that it is really necessary. BUT other epoxy’s are very different and some have a good deal of odor. Check first. That said - I don’t find any epoxy’s as smelly as poly.

MrJ made boards in his apartment with epoxy. it’s possible to do so without offending the neighbors.

Eric J

i can have barrels of epoxy going off all day and no one knows …

mix up one little batch of polyester for a ding repair or to make some fins , and the enviromental officer is at my door …

regards

BERT

i think kirkside in osborne park might be easiest for you to deal with …

bluejuice might know someone else closer …

i mainly deal with fibreglass and resin sales in welshpool …

thanks eric and bert,

Bert , what do I ask for? is it called ‘surfboard making epoxy’ , or general purpose , or what ?

[I don’t think we have Greg Loehr’s resin research epoxy here, DO we ?? [pity, it SURE sounds like the good stuff !]

I ask, because friendly as the old guy at Kirkside is, and he always tries to help, I don’t think he has made too many epoxy surfboards [or, should I say, glassed polyurethane blanks with epoxy] . So , I wouldn’t want to get the wrong stuff - or, IS there one general purpose epoxy for all ?

How much should I expect to pay for say 2 litres at a time … do you use more quantity of resin [or less, or the same?] than when using polyester , and … final question…

the same ‘stuff’ for laminating and filler coating , and glossing ?

okay, thanks !

  ben
Quote:

Stringerless blanks… well, shoot, I gotta tell ya that the first blank I ever shaped (after reshaping a couple longboards) was mail ordered from Dave Sweet, he advertised in Surfer magazine. This was in '69 or so, I lived in Hilo.

The blank came in a box… stringerless (surprise) and utterly devoid of rocker (surprise). It was just a rectangular parallelopiped (now that I’m older I can write these things).

I made a 6’6" very light board. The blank acquired a twist in it, which I never completely removed. It was very responsive, and for the day, very light. It also collapsed under my back foot pretty quick, despite double 7.5 ounce glassing. Weak foam.

Still, it is interesting to think of doing it again, though I don’t think taking out the stringer is a winning idea. I think most of the strength of a board is in the glassing; I think snapped boards fail first on the compression side of the stressed board, when the glassing releases from the underlying blank. This compression failure is followed by the stringer failing, and the tension side snapping. More detail if you want it. Can’t help myself of interjecting on this old post…the above paragraph has got it backwards. Nearly all boards break because the bottom stretches, the deck buckles the stringer fails. See te thread on stringerless longboards talking about the 9.6 lb EPS longboards I made recently for double and triple overhead…DS

IF I got a rockerless chunk of EPS, XTR or whatever, I’d probably put a stringer in it for shaping purposes. It would probably flex too much to shape accurately otherwise. HOWEVER, after rough shaping I’d think of just going stringerless with (miltiple) glue lines.

Ben, I am in the process of finishing up a stringerless 1 lb EPS 5’8", 20" wide, swallow tail.

It’s the board I posted about in a thread called ‘offcuts’.

Camera isn’t working, I’ll try to borrow my daughter’s camera when she gets home from school.

I won’t be able to give a ride report til I get it in the water, which might be a while, with the holidays

taking up so much of my time.

I used 3x4oz cloth on the deck and 1 layer of 6 on the bottom. Actually lapped all 4 layers around the rail,

from lack of knowlege not to. I’m kinda glad I did, it feels plenty stiff.

Right behind it I have a 2lb EPS templated for a 5’10" fish. I’m gonna go thin on this one. Really thin,

like 1 7/8". Figure it’ll work as I’m only 150 lbs, soaking wet.

Reviews will take a while because I work pretty slow and stay busy with my job.

I will try to look this thread up when I have ridden them.

I’ll post pics of your Hempys on my board if I can borrow that camera.

hey chip!

Here’s an idea to glass it if no one else has mentioned it. Glass it like normal 4x4 top 4 bottom, add a 6x4 top if you want more strength, but instead of adding extra layers to the entire bottom or top, just add 2 extra layers or glass only on the rail laps. Pretty much cheap man’s perimeter stringer of some kind. You can taper off the glass around the tail / fin area if you are looking for more twang off the tail or something. I would think 2 strips of 4 oz would be enough to add a significant amount of snapping strength to it without stiffening the board too much. If the board is too flexy, could just add another layer on the rails after some sanding or sand down the rails if it becomes too stiff. This leaves quite a bit for exploration I would think.

hope that helps

Quote:

Ben, I am in the process of finishing up a stringerless 1 lb EPS 5’8", 20" wide, swallow tail.

It’s the board I posted about in a thread called ‘offcuts’.

Camera isn’t working, I’ll try to borrow my daughter’s camera when she gets home from school.

I won’t be able to give a ride report til I get it in the water, which might be a while, with the holidays

taking up so much of my time.

I used 3x4oz cloth on the deck and 1 layer of 6 on the bottom. Actually lapped all 4 layers around the rail,

from lack of knowlege not to. I’m kinda glad I did, it feels plenty stiff.

Right behind it I have a 2lb EPS templated for a 5’10" fish. I’m gonna go thin on this one. Really thin,

like 1 7/8". Figure it’ll work as I’m only 150 lbs, soaking wet.

Reviews will take a while because I work pretty slow and stay busy with my job.

I will try to look this thread up when I have ridden them.

I’ll post pics of your Hempys on my board if I can borrow that camera.

cheers mate

i eagerly await a ride report and photos

hi tonybanger !

my stringerless has been consigned to landfill about a year ago from memory …

sorry to the environmentalists here …

[…what ? YOU have ‘never’ thrown a board away ? heh heh]

ben

I tried shaping a Core Fusion blank. Nice foam, just felt I was trying to shape a soppy sponge. I’m about to try some Bondor polystyrene, VH grade stuff. Feels quite stiff so shaping it as stringerless shouldn’t be too hard. Hopefully.

just thinking … [i do that once or twice a week]

i reckon it’s kinda interesting that this thread resurrected , after so many years [i was trying to forget my abomination that causes desolation board …it had some kinda weird bonzer bottom gone wrong …“those aren’t channels , they’re CANYONS” was , i believe , what shipman’s comment was …he was RIGHT , too , of course !]

of course , now this thread has revived , it has done the [always dangerous] thing of making me think about “having another go” . I mainly did it in the first place because [you guessed it!]…

the stringerless blanks [known here as “packing blanks” , are …yes…free.

they ARE polyurethane , too, thankfully , so can be glassed with polyester resin , and resin swirled etc …

cheers for throwing up an old thread i had forgotten about [if you saw my " benzer bottom" [what i called the …erm…“board”… you’d probably throw up too !!

cheers

ben
Quote:
just thinking .... [i do that once or twice a week]

I try to avoid that sort of thing if I can possibly help it.

Quote:

Still, it is interesting to think of doing it again, though I don’t think taking out the stringer is a winning idea. I think most of the strength of a board is in the glassing; I think snapped boards fail first on the compression side of the stressed board, when the glassing releases from the underlying blank. This compression failure is followed by the stringer failing, and the tension side snapping. More detail if you want it.

My board proofed that It first fails on compression. Because it is broken without breaking of the stringer.

But I think it is not completely correct because the stringer stiffens your board and takes up a part of the load which helps against delamination and failure in compression.

I also noticed that the rails play an important role! Actually my board broke first on the rails (and I had a double overlap on it, 4*4oz), but I kept surfing it :stuck_out_tongue: (it was my second shape and my first good one but It was on for replacement). The rail took a lot of the load because that’s the stiffest part, the deck glass has always a bit of freedom to move, while the rails do not have. So first the rails failed, than the deck-lam in a sort of delamination and the stringer is still intact.

So a stringer will alway help.

I think that the optimal stringer is an horizontal stringer (~3inch in width) routed in the deck with unidirectional fibres under it. (sort of decksandwich)

This will take the compression very well. But you’ll need a vacuum pump to do it, so you can make a compsand with little more work :D.

Hans: I think you, I, and DeadShaper are all pretty much in agreement. We read these posts quickly and miss some of the intended meaning. DeadShaper posted his annotation to my comment in bold red print above, easy to find.

I’ll try say it again, hopefully a little more clearly: when the board is stressed, it flexes in response to the load. If the force comes from above, the deck is in compression, the bottom in tension. The stringer is stressed also.

Now stress and flex are natural and don’t hurt anything, up to a point. As stress increases, though, something has to go. My contention is that the initial failure is the shear bond between the glass skin on the compression side, and the underlying foam. When that bond is broken, the glass skin buckles outward and you’ve lost much of the flexural strength. Unless the stress is immediately released (and this does happen, some boards buckle without snapping) failure of the bottom skin and foam follow almost instantaneously.

Given the above failure mechanism, I think it is a rare circumstance that rail glass will break without first there being a shear failure between the deck or bottom glass and underlying foam. I suspect you have such a failure on your board, but it “relaxed” back to flat and you can’t/haven’t found it yet.

I believe the ability of the stringer to prevent shear failure is small because… one, the bond between glass skin and stringer is quite narrow and the contribution against shear failure is therefore small; two because I don’t think the bond between glass skin and stringer is as good as between glass skin and foam (no penetration by resin means very thin bond surface and very high stress riser).

But enough. Anyone wanting a stronger board knows how to get there: first, blank thickness which is easily manipulated and second, skin-to-foam bond which I don’t presently know how to effectively improve.

Allow me to jump in here to back up Honolulu. We had a thread on improving break strength a while ago

where I posted almost the same description of the mode of failure for most boards. Rails don’t go first unless

there’s a ding or something to focus the load. When you get off into monocoques and compsands the failure

modes are different, but for hand-lammed single skin on foam Honolulu’s got it right.

Mike