compsand longboard, what wood glass schedule?

General Discussion
1

Hello all,

The plans are to make the 16kg-m3 longboard below…

Besides Balsa, I have also Corecell lying around, a sheet of 10mm2450mm125mm, or 8 foot long * 4 foot wide * 2/5 inches thick

Rounded square, squared off a bit more

Light vee all over the board, flatter in the middle, 5 fin set up, with a centre fin box, for mckee-thruster-single+bite combos.

From what i understand, the forces during surfing are not really bigger. But the waves are, and their force on the board during a full on lip hit (i mean water falling onto board) are enormous. How can this board survive this type of waves…? Not very steep, but big, fat, sometimes fast, sunset type of wave… I have seen the most board broken, including my own…

What is the type of wood and glass i need to use?

My thought is to use stiff 6mm balsa, the browner color for the top. (or crossgrain 3mm twice with glass in between?)

Combo it with 6oz oz glass inside and 6oz outside for topl, i only have 0/90 glass and some hollw glass.

Btw, i will bag all the glass on. I currently use a 1:1.05 glass to resin ratio. I will use some of the flexible cold harding Araldite or greg loehrs felxible epoxy, god willing! GD seabase shipping never goes well, waiting since last december for it!

Bottom 4mm balsa, with 4oz/4oz.

And patches for feet hands, and extra glass over the rails-balsa attachment, feathering it all out.

Rails are going to be corecell. I found out that thin layers of balsa are not good enough at spreading the load.

I will lap the skins onto 1 cm of corecell, then add another cm to it, and final shape.

HD foam inserts of course

btw, i can also get hand on 5mm bamboo veneer, or 0.6 mm bamboo veneer and any other veneer basically.

2

Hej Wouter,

You didn’t say what kind of EPS inside (unless it was in metric and I just didn’t realize what you were talking about which is very likely)…

I’ve made dozens of balsa compsand longboards now and can hopefully give a little help here. I think you’re overthinking the skins and will end up with a very heavy board. I also would say that the balsa is MOST important on the rails, because the fiber strength is way better than any foam. Yes, laying on the rail pieces bit by bit is a horrible trial and time-waster, but those have all been the best-riding boards I’ve had. Definitely worth the trouble.

I’d also skip the ‘light vee all over the board’ as that kind of shape will limit flex and the thing that balsa compsands do best is flex. That way you can make them wide, thin, and with less rocker than a foam & glass board, and the flex will give you the rocker you need, when you need it. Edit: you can ease off the rocker by 1/2" on each end, from what your Atuacores shape above shows, and if you make the panels pretty flat (no big deck dome, no bottom concave or vee) it will behave just like that shape above when you’re turning it…

Hint: politics aside, not all of what Firewire says is bull$h!t. And they kept the balsa on the rails too.

If you use 1# EPS, you want 2mm balsa skins with probably 6oz glass on both sides of the deck & 4 oz on both sides of the bottom skin. If you use 2# EPS, just use 4oz glass everywhere (that’s what I do) with 2mm skins.

If you want to use that corecell somewhere, use it on the deck.

I build the balsa rails all the way up to a whole 1" in 4 - 1/4" pieces. Nose & tail blocks of solid balsa make quicker work of the curvy ends and if you put them on first, you can wedge the ends of the rail strips under the angled cuts of the blocks to help hold them on while the glue sets up.

If you’re bagging on all the glass, seal everything first, otherwise your resin will go too far into the EPS & the Balsa and leave the laminates too dry and they’ll peel off (delam). No fun. I have hand-glassed the outsides of all mine except one or two and won’t ever bother bagging on the outside glass again.

I built one (my first one) with 1/4" balsa skins, that’s about 8mm. It had a 1# EPS core. Sealed everything and only used single layers of 4oz glass. It weighed almost 35 lbs. :stuck_out_tongue: The worst, though, was that I cracked the skins in the two big dents where I knee paddle. I think that there’s a point in skin-core thickness (the balsa or the corecell or whatever) of diminishing returns. That’s the point where the core of the skin itself can be crushed, rendering the inner glass immaterial. You want the skin itself thin enough that the strength of BOTH of its pieces of glass will come into play. I’d go no more than 4mm EVER and I think 2 or 3 is best. Let the strength come from the rails and the shape…

And good luck & have fun! :smiley:

3

Hi Wouter -

First off, that’s one clean looking outline!

You won’t get better home brew technical advice on compsand longboards than from Benny1. He’s built a bunch and has tried all sorts of tricks.

Just for clarification if he’s still around, by sealing the EPS and balsa I assume that means with an epoxy microballoon slurry on the foam and clear (possibly thinned) epoxy on the balsa? Seal the balsa inside and out? Does the thinner balsa possibly absorb enough epoxy to essentially “plasticize” it through out the thickness? Would thinned epoxy allow better/deeper saturation into the balsa when sealing? Maybe seal under vacuum?

I know Bert Burger used to hint at stuff like that and posted a yacht advertisement once that mentioned wood impregnation.

4

Quote:

you can wedge the ends of the rail strips under the angled cuts of the blocks to help hold them on while the glue sets up.

5

You probably can get away with 1/8" balsa skins

sorry I have metricized myself yet.

Corecell on the deck or use the corecell for your rails or better yet for both with a balsa bottom.

BTW if want super tough the do what the sailboard do

balsa layer under the corcel glass under and over.

That should be very strong.

but remember this…

everything snaps

depending on the wave and where it hits

follow Benny’s glassing schedule

To keep it lighter you can seal the EPS with a thin fastnfinal spackle or with an epoxy microballoon slurry

before glassing on the skins

Then paint on and seal the outside of the wood skin with a solution of epoxy thinned out with Xylene (10%)

you can use a light epoxy slurry on the Qcel to also prevent alot of resin absorbtion as well.

If you want

if you super glue your balsa skins before hand you can seal the wood with the brushed on thinned out epoxy prior to attaching them to the foam which might be a better solution to prevent the epoxy soak discoloration you normally get. The “plastizing of the balsa tubes” not only decreases the resin sucking when lamming on the skins and outer glass but epoxy saturating the wood also helps breakdown the internal structure(according to wood ogre) and makes it more pliable when attaching it to the foam. Dpn’t know if this require you soing it when the wood is wet though.

I think most professional resin infusion is done using autoclaves, heat and intense vacuum pressures. Kind of like how they make those fancy resin impregnated woods used for wood turning of pens and knive handles. It’s also used to stabilize spunky burled wood that would normally fall apart when whirling at a high speed in a lathe. I don’t think you need anything that fancy.

In the end it’s just a surfboard…

And its gonna get dinged and break your heart sooner or later

sometimes I think we forget about that…

6

Yeah, these guys all know… :smiley:

I’m not afraid of spackle. In the end, its ALL just silica and plastic. Spackle IS microballoons, and usually a latex substrate. Whatever works. The last few boards, I’ve been using some tan filler for oak floors. You are supposed to nail down all the wood and then use this stuff to spackle the gaps & nail holes, then it mostly all sands off when you sand the floor smooth. So I figure its pretty good stuff, since floors take a lot of abuse. Plus, I bought a gallon bucket and the room I did only took about 20% of that LOL. Turns out, EPS likes it just fine. It lays down fast with a taping knife, sands smooth, and doesn’t delam. I actually realized part way through, that the color would help too if I ever sanded through the balsa where I was blending it to the rails… “Trowel Grade” ha ha ha :wink:

I don’t seal the inside of the balsa, though. I bag down the balsa skins (glued together first with a product called Multi-Grip, which is almost as fast as superglue but more flexible and the fumes don’t make my eyes water) with the glass underneath and epoxy. Pull about 9" Hg and any extra epoxy (I’m not real anal about my ratios) shows as spotting in the wood. This only works when the wood is thin, like John & Bernie said. I like seeing the spots, since I know I’m strengthening the pore spaces and waterproofing. Since I lay down the glass & resin on the wood before flipping it onto the blank, I know the epoxy was even, so I figure that since the epoxy only shows through to the other side in spots, then the places where it didn’t come through were better places in the wood. I’m not trying to saturate ALL the wood, just trying to give a little extra to the soft or porous areas.

And then, as said above, before hand glassing the outside, I give it all (including installed & shaped rails) a quick coat of epoxy. I don’t thin it, just heat it and work fast with a 4" throwaway brush. Then glass just a couple hours later.

I haven’t had any of the creeping black rot problems that some people report with balsa. A little extra resin & a couple prophylactic steps can go a long way… and don’t worry about your ratios. Sure, glass/resin is great at 1:1 or whatever, but unless you’re using those to laminate together two completely non-porous substances, that ratio isn’t going to stay that way because some of the resin will end up in something other than glass cloth. So control your pressure right and let the resin go where its needed. No reason to overthink any of this - the materials take care of themselves, given the chance.

7
Quote:

Hej Wouter,

You didn’t say what kind of EPS inside (unless it was in metric and I just didn’t realize what you were talking about which is very likely)… THAT IS 1.00 POUND/FOOT3

I’ve made dozens of balsa compsand longboards now and can hopefully give a little help here. I think you’re overthinking the skins and will end up with a very heavy board. I ALREADY HAVE THAT EXPERIENCE… ONLY 1 LAYER OF BALSA, WEIGHING IN ITSELF SOME 500 GRAMS ALREADY I also would say that the balsa is MOST important on the rails, because the fiber strength is way better than any foam. Yes, laying on the rail pieces bit by bit is a horrible trial and time-waster, but those have all been the best-riding boards I’ve had. Definitely worth the trouble. RIGHT ON

I’d also skip the ‘light vee all over the board’ as that kind of shape will limit flex and the thing that balsa compsands do best is flex. That way you can make them wide, thin, and with less rocker than a foam & glass board, and the flex will give you the rocker you need, when you need it. Edit: you can ease off the rocker by 1/2" on each end, from what your Atuacores shape above shows, and if you make the panels pretty flat (no big deck dome, no bottom concave or vee) it will behave just like that shape above when you’re turning it… GOOD ADVICE !

Hint: politics aside, not all of what Firewire says is bull$h!t. And they kept the balsa on the rails too.

If you use 1# EPS, you want 2mm balsa skins with probably 6oz glass on both sides of the deck & 4 oz on both sides of the bottom skin. If you use 2# EPS, just use 4oz glass everywhere (that’s what I do) with 2mm skins.

If you want to use that corecell somewhere, use it on the deck.

I build the balsa rails all the way up to a whole 1" in 4 - 1/4" pieces. Nose & tail blocks of solid balsa make quicker work of the curvy ends and if you put them on first, you can wedge the ends of the rail strips under the angled cuts of the blocks to help hold them on while the glue sets up. I DONT QUITE FOLLOW THIS, BUT APPARENTLY GOOD ADVICE, ACCORDING TO AFOAF…

If you’re bagging on all the glass, seal everything first, I WILL SEAL WOOD WITH SPECIAL WOOD SEALING EPOXYY AND THE BLANK WITH SUPER LIGHT WEIGTH FILLER, THANKS BALSA… otherwise your resin will go too far into the EPS & the Balsa and leave the laminates too dry and they’ll peel off (delam). No fun. I SEE THAT ON ALL OF THE SURFTECHS I HAVE REPAIRED, REALLY EASY TO PEEL OFF. I have hand-glassed the outsides of all mine except one or two and won’t ever bother bagging on the outside glass again. MMM…

I built one (my first one) with 1/4" balsa skins, that’s about 8mm. It had a 1# EPS core. Sealed everything and only used single layers of 4oz glass. It weighed almost 35 lbs. NO SHIT ?? :stuck_out_tongue: The worst, though, was that I cracked the skins in the two big dents where I knee paddle. I think that there’s a point in skin-core thickness (the balsa or the corecell or whatever) of diminishing returns. That’s the point where the core of the skin itself can be crushed, rendering the inner glass immaterial. You want the skin itself thin enough that the strength of BOTH of its pieces of glass will come into play. I’d go no more than 4mm EVER and I think 2 or 3 is best. Let the strength come from the rails and the shape…

And good luck & have fun! :smiley:

8
Quote:

In the end it’s just a surfboard…

And its gonna get dinged and break your heart sooner or later

sometimes I think we forget about that…

9
Quote:

Hi Wouter - hi oneula !

1.First off, that’s one clean looking outline! THANKS JEFFREY SWARTWOOD

2.Just for clarification if he’s still around, by sealing the EPS and balsa I assume that means with an epoxy microballoon slurry on the foam and clear (possibly thinned) epoxy on the balsa? NO, SOME SUPER LIGHTWEIGTH WALL FILLER, REAL LIGHT, REAL EASY TO SAND DOWN. Seal the balsa inside and out? BENNY SAYS OUTSIDE ONLY, Does the thinner balsa possibly absorb enough epoxy to essentially “plasticize” it through out the thickness? Would thinned epoxy allow better/deeper saturation into the balsa when sealing? Maybe seal under vacuum? I HAVE TRIED, NOTHING CONVINCING YET

  1. I know Bert Burger used to hint at stuff like that and posted a yacht advertisement once that mentioned wood impregnation. I JUST USE SPECIALLY FORMULATED EPOXY, THAT SEALS WOOD TO PREVENT ROTTING. GOOD ENOUGH, AND THEN LAMINATE STRAIGHT ONTO THAT, WET IN WET.
10

Hey Benny

It is finally time

just want to add one more bit of into and ask some more questions…

The blank is only 2.25 inches thick - i worry about overflexing/ /breaking it [1.0# foam] with 2mm only skins, 1# and 2/25 inch balsa. What do you reckon? Still stand by your old advice of 2mm skins?

Thanks

11

i havent gotten around to T-flex yet, for lack of money

so ill post the build of this one step by step

i decided not to tape or clamp [no clamps] but vac a part of the rails together first

its so much easier than mocking with tape and stuff. i hate it.

first tried wood glue ----> LEARN = you need a lot of it, because it let go!

                                     LEARN  = epoxy is better option, which i used 4 try nr 2

nose rail curvature------> LEARN Make relief cuts! it doesnt bend in real well.

And, you also have to keep the planks together, cause you dont want voids, so there is minimal tape insde, to hold em together, outside tape [grey can be taken off again]

So its in the bag now, with relief cuts and epoxy