Pocket board building

[grandeand]

guys,
my idea is to make a table about 125 cm by 47-48 cm. a freeride, therefore flat in the hull or with a slight flaring on the sides in the hull.
i have a 150 # 50 # 30 block of eps 25 kg / m3.
I have a block of high density PU for the tracks.
my question is: do i have to put a 5mm sheet of airex or material that resists compression on deck or just put some more fabric?
does the hull sink into the heel area?
should I possibly put it on deck and bottom?
I have difficulty finding Airex in Italy and a 150 # 50 panel costs me 50 euros.
What do you think?

[bay surfer]

Just use the PU Block if the tracks are set in, or make the core the same depth as the tracks then you don't need the PU . You have to beef it up anyway with glass/carbon and a wood or carbon stingers, or it will snap, its not a surfboard.

[grandeand]

I certainly have to laminate more than just a surfboard. my idea is two 25 cm and 20 cm wide strips of 200gr / m2 unidirectional carbon, which wraps the deck and hull in the center (it should replace the central spar and also covers rails and central pu block). then plain carbon or twill of 200 g / m2 one above and one below and to finish a 200gr layer of glass as a finish and protection for the carbon always above and below.

[TomW]

Question about laminate schedule.
Goal is to build lightest possible but maintain durability so the board lasts many years. I´m primarily concerned with compression/ding resistance for knocks and heel pressure.
Boards are all strapless " pocket" hydrofoil boards and i dont see them being used for strapless airs.
Core will be 80kg PU cellfoam.

My thinking was to use 1 layer of CF 200g twill on the bottom, and 1 layer on deck. Both layers are rail wrapped. on Deck i will also have 1extra 3/4 deckpatch.
In addition, on both sides, i will have 3 layers of 250g uni D CF staggered in length, 140mm wide " srips".
All laminates will be vacuum bagged on.

I have been thinking of carrying out some tests, but dont know how to go about doing the " pressure tests" in a somewhat quantitive method. other than making test parts and jumping up and down on them barefoot and hitting them with a bar end

Looking for some emperical evidence.

[merl]

Tom, I (90kg) can only give my single data point with my similar build (which we have previously discussed): after a busy few months I have bumped and bashed the rails a few times and I see no signs of any damage. Definitely no heal pressure issues anywhere, and it does not feel likely. I am also using just a peelply finish and no EVA. My feeling is that it is more robust than many boards I have owned. So I think your schedule is fine. I'd be interested to calculate the total weight of uni in the "stringer" as a point of reference. Mine was only two layers of approx 250g x 20cm wide, on extending as far as the front foot (70cm) and one shorter one (45cm) which is around 60g uni per side. If I did it again I would add one more short layer (even though I don't know if it is needed).

[downunder]

Hi,

I dont get u guys, sorry.

Here is undestructible bamboo 4mm + 2 layers of 4mm paulownia, so all around 12-13mm.

No carbon or FG yet. Only inserts. I cant bend it with my hands, 920/450 mm, rocker 40mm

Cost? AU$30.

As mentioned many times, corecell, airex etc sheet 5mm is $200. Plus other bits. It is just not worth for me when bamboo is more accessible.
Bonus, it is Planet friendly, but thats another topic.

[attachment=0]IMG_20200807_210113.jpg[/attachment]

[merl]

That's great too. After making a paulownia board I wanted to make something under 2kg and the materials I chose were probably the cheapest way to do that. And really simple too. I don't think I spent more than eur 100-150 on materials. No need to make it cheaper. It would be great if we could get thin paulownia at a good price though. The stuff I have seen is more expensive than HD foam. Different builds, different access to materials, different parts of the world.

[downunder]

Yes,

Bauhaus in EU sells Paulownia in 20mm thicknes by sheets for eur 30 or even less. It is at least 500mm wide and 1600 long if remember well.

So you guys CAN build light Paulownia boards with KISS method.

The obssesion with foam boards is just something I do not get.

It is not about the volume or weight. So what is it?

[TomW]

The 80kg foam I use costs 28€ per board. Because I'm buying small quantity. Thin paulonia not available. I'm trying to import from China.
Balsa is nice, still build that way, but it sucks water and disintegrates on water absorption.
Using 18mm paulonia from bauhaus would mean milling down to thin thickness with huge waste. or no rocker, which I want.
I'm trying to get under 2kg.

Thanks Merl, seems on on track. I heard a famous racing boat builder say" if it's not breaking it's too heavy". That said the extra carbon bit each side. will weigh only 50 - 100g.
What I do is take 2 full length uni d carbon strips, cut one into 2/3 and use that other 1/3 under foil plate too.

[downunder]

My build IS under 2kg.

re milling it. It takes 1 minute on thickenser to get down to any thickness needed.

Riding a flat board is even less problem once we pass some stage.

If Bauhaus plank is 1800mm long, this means 2 boards by 900. Adding extra bit width wise to close the grain, and can be 1100mm in length.
Cost? Under eur 20 for the core. No carbon at all.

Well worth doing it.

Im just saying that there ARE options, and way better for the environment. Not for you, u using foam and thats fine. Not true about Paulownia Tom, u well know the Malme shop who sells it there:

https://www.junksupply.com/product/paul ... tra-thick/


But for the other readers, like Italy, where foam is expensive, Bauhaus is sensible option.

Or buy above 12mm and build 24mm core with any rocker up to a point. Sure, will be slightly more in weight, but undestructible.