Good luck, should be interesting, watch your vacuum level, you don’t want to flatten your eps blank!
Hi Mark,
Should not flatten the blank as the whole board goes in a complete bag and thus atmospheric pressure is squeezing on all surfaces equally.
Don’t go over 0.2 bars or else the surface will start to collapse. That’s low pressure infusion, keep us posted on your experiments.
Hi Rikds,
Can’t wait to see your project, sounds like a great idea. I was wondering how you were going prevent the foam from sucking the resin. Are you just going to RTM the outside of the board? Anyways, good luck man. It should be fun.
Cheers,
Rio
Believe me mate, if you put an eps blank in a bag (even #2) and pull more than 7"hg, you will destroy it!, at that low level of vac, you had better have some low viscosity infusion resin to use (with uv blocker?)
Good luck
I wanted to add that you should watch out for your vacuum fittings, spiral wrap tube, etc… being smashed into the foam. Make sure your bag doesn’t leak. At all. Also, make sure you have a resin trap inline before your pump. -Carl
I pulled 15"hg on my last board, 1lb eps, turned out fine, no crushing. This was after totally crushing my first attempt with 22"hg. 
I wonder, did I just get lucky or is my gauge off? Shouldn’t be the gauge, its brand new… I’ve also heard eps from different producers can have differing characteristics. Maybe my supplier’s eps is denser than most?
why dont you just pull it to what is recomended and tested?
ie. around 7 hg
thats all you need to attach the skins
then you dont have to worry about it
I’ll take full responsibility for the 15lbs…
When my brother and I were showing Satori, Uncle D, Manoa and Mike Casey how we put balsa skins on foam I told him that we usually go between 10-15 lbs on our setup. We’re using lowes .75lb foam and haven’t crushed anything yet and maybe that why we don’t need valves …
I don’t know…
Anyway if it was wrong advice that was given it came out of my mouth to Satori so I’ll take the blame…
Sorry Joe,
All we can do is show guys what we’re doing and we’re the first to admit we’re not pros at what we do we’re just playing around having fun making weird sh*t that no respectable board builder in their right mind would consider… Too bad they’re gonna last forever…
I usually use about 7"hg on the bottom skin and 12"hg on the deck, ie no exposed eps when the deck goes on , and the pressure is spread more evenly through the deck skin.
I have crushed eps through having too high a vacuum on it, so anyone vaccing or infusing the skin on a non sandwich board would be well advised to be very careful with vac level and temperature.
Hey All,
I vac’d my bottom skin on ~15 Hg accidentally and it didn’t crush but it bent the off cut. So, it increased my rockers on both ends about an inch. The springback of the skin sort of put the rockers back into place. When I vac the deck, hopefully it’ll all go back to original specs (fingers crossed)
Cheers,
Rio
hey Bernie
ive pulled higher hg’s no worries
but it does compress the foam somewhat
it pulled nice wee bottom concave
and I notice the rocker table was smoother
i think any higher and the whole board would have crushed
at the moment my pump will cycle between about 6 and 9 hg
if i had an accurate switch id keep it at 7
7 hg is huge clamping pressure
Quote:
All we can do is show guys what we’re doing and we’re the first to admit we’re not pros at what we do we’re just playing around having fun making weird sh*t that no respectable board builder in their right mind would consider… Too bad they’re gonna last forever…
im the first to admit
im a begginer
please dont take my advice as fact
im only 10 boards in .
but still, the collective body of thought contributing to the techniques of this construction
really irons out deficencies quickly
actually
the easiest way is to get a block of foam
measure its dimensions
stick it in the bag
and pull vacumm to increments of 1 hg
everytime remove from the bag and remeasure dimensions
just to make sure everyone understands our ultra cheap technique…
we buy super cheap flat panels of .75lb EPS from the hardware store
we don’t hot wire cut rockers but use the classic $14 blank bend in rocker glue up with the following exception…
We don’t use rocker tables or offcuts
everyone that we tried with a table never really worked and the rocker flattened out.
What we do instead is find a rocker from one of the 29-35 boards we own and saran wrap tape the glued up slabs of foam to the bottom of the board whose rocker we want. We then stick the whole thing board and wrapped up foam blank into the vacuum bag and vacuum the foam to the board with the bottom balsa skin and internal stringer between the sheets of foam to “set” the rocker we want…
As I said we never had any luck a rocker table and I guess since the form we’re attaching the foam to in the bag is a completed surfboard our rocker mold is not impacted like an offcut by the higher pressures.
It’s a very hacker(non-professional) way of doing it but in our opinion better than the books and bricks technique of the original $14 stringer concept we originally saw posted around here.
If I were to use a table, I would do it the way the sailboard video shows and vacuum the blanks into the table using windshield glass tape and plastic sheeting instead of a bag. That would be kind of similar to what we’re doing with a surfboard as a rocker mold in the bag with the foam.
Just thought I’d clear that up for everyone who’s been wondering about our higher pressures and stuff.
No worries Bernie, I think I’d forgotten what vac pressure you used when I crushed that first board. The 15"hg seemed fine, but I agree with what Silly said, why chance it? If 6-10 is enough for my skins, no reason to go higher. The only reason I used more pressure was because of something (I think) Bert said, about the pressure forcing the epoxy resin to even itself out and fill in any dry patches in the cloth. I wet out my cloth by folding it into a small square and pouring an equal weight of resin on it and let it soak in. You end up with a few dry spots here and there when you do that, I was hoping the extra pressure would squeeze the resin into those dry spots. Another solution might be to roll the cloth on a pipe or cardboard tube like I’ve seen some guys here do. Could get me more even saturation of resin.
Also, I’ve had the same problem with my rockers flattening out. I use flat sheet foam mostly, and vac bag on an adjustable rocker table. I wonder if it flattens out because I’m using RR epoxy, it has some flex naturally. Maybe I should try a stiffer epoxy, like FGH’s, for the inner glass layer on the bottom, might hold the rocker better. I’m not ready to give up on the rocker table yet.
hey satori
just wet out the inner glass on the skin is the easiest with a spreader
it might only add 20 grams weight to the total
flip it on to the blank and bag it
wrt higher pressures as disscussed
most likely used in preforming the skins before you attach them to the blank
eg. if you want a really flat light skin. or use infusion tech.or a high temp post cure
even if you predo the skins you still need to attach to the blank the normal way(ie wet inner glass etc)
ps dont give up your rocker table imho
I was tempted by that aircraft ply as well a while ago, tho the price was bit ridiculous. Then i found a 1.5mm standard exterior 3ply somewhere and used it between 2 1.25inch thick eps sheets as a horizontal stringer to form a rockered blank that i could shape without being floppy. ended up a disaster when trying to timber veneer the deck and the vacuum cleaner died. Now the veneer on top looks like some bad camoflauge pattern, having to constantly rip off delamed patches and fill with resin…
Was hoping the horisontal ply would help control a good flex, but really i got no idea as to its effectiveness. Probably it is better used in the skin where compression and tension forces are greatest, rather than in centre of cross section where the forces are minimal.
Seem to be learning lot more reading this thread than thinking myself…
MOrgen
did someone remove the pictures from this thread??
I get little red crosses where the pictures are supposed to be
They’re still there for me.
just thought i d bring this back to remind some
this preceed any thing whith R
OR FIREWIRE for that mater