skin thickness

[windfreak74]

Im starting my new board Project and i would like to build a hollow board for foiling to carry emergency gear, camping gear and a safe plataform for resting if things go sour.
something that can be paddle.
the pourpose is coastal cruising and adventure.
i live in Chile and coastal cities are to spread around so i can expect sometimes 50 miles of nothing while sailing.water is cold so a good flotation of board is a must.
my initial thoughts are to build a 170 x 60 board with 20 cms thick to carry the gear inside and an adittional wáter backpack somewhere in the 200 to 250 liters.
first prototipe will be fiberglass with a kevlar carbón outer layer.
with proper reinforcing how much skin thickness do you guys think ill have a good structure?
what is the normal skin thickness on a kayak?
any thoughts?
Pedro.

[windfreak74]

board sketch

[rynhardt]

I believe a typical surfboard top laminate is around 600g/m2 glass and bottom laminate around 400g/m2 glass.

That should give you some idea of typical skin thickness on a displacement type hull. Keep in mind that the thickness and density of the foam core provides some support and the integrity of the sandwich construction provides the overall rigidity.

In terms of whether the structure will be good or not is dependent on too many unknowns, so I'm going to reserve comment on the overall design concept, it's seaworthiness and possible adverse handling characteristics.

[BWD]

For a kayak with solid monolithic laminate I think the skin is 600gsm or more, with reinforcements as needed. But a lot of kayaks would have a sandwich skin, 3 to 6mm foam with 200-400gsm cloth each side. Or more.

I think you are going to want a sandwich skin over EPS core for this project, with some area hollowed out for storage, and stringers and other structural reinforcements around the storage areas and foil attachment. It sounds like a big, challenging project, building a mix of a board, and a boat. Good luck!

[Bigdog]

Here is kind of a wacko idea. Make your board with the ability to pump up extra tubes around the outside like a zodiac. Or add a outrigger also pumpup. Something you could squash down inside your storage area but assemble when a paddle is the only option.

[windfreak74]

better wacky than dead, all ideas are well taken!
I have been alone in the sea 1 km away from shore
waited for an hour for the wind to pick up again
its funny when you are having fun and you loose track of time and misjudge distance.
not very pleasent to swim in 5 to 8 degree celcius wáter and no one in miles to help.
If i decide not to kite when im alone i might just give up kitting.
is just my reallity.
probably 5 guys kite in a 150 km radius.
sometimes we cant get toghether.
survival is my main goal but it would be nice to have some gear if getting stranded for some odd reason.
shit happens!

[Bigdog]

You can use kite style LE construction to make a lightweight zodiac tube. Even an old kite repurposed.

[windfreak74]

hello bigdob,
there is a inflatable campers dinghy from klymit that is lightweight.
the problema i see is that you need a board that floats to be able to sit and inflate anything on wáter.

[zfennell]

hi pedro,
your drafting skills are pretty good.

the appropriate skin thickness for your 'boat' will likely have a lot to do with the fabrication technique you choose.

the comparison to kayaks may be a good application considering the relatively flat panels and hard chines shown in your drawing.
a quick search of 'stich n glue' or 'stripbuilt' or 'skin on frame' type kayak construction
would give you 3 different techniques that could get the job done.
they would also be a good fit for your wood working skills.

if you want to follow a more traditional surfboard type construction process, have a look at swaylocks.com
you should find examples for large home built SUPs or ocean going paddle boards

large Styrofoam (eps) blocks can be easily shaped and glassed.
the higher density cores (> 2#/ft3) can be glassed with a simple (non-sandwich) laminate.
likely to need only 1 or 2 plys of 6 oz glass

core less than 2 # density are suitable for sandwich skins .
some use .1" or .125" balsa with 4oz glass on either side.
some use .05" hard wood veneer skins with remarkable results
you can search swaylocks for "WMD compsand" to see what's involved
There is also a compsand.com forum with lots of examples

the benefits of the composite sandwich skin is the increase load capacity of the skin while reducing the density of the inner core and overall weight of the board.

if you take the idea to extreme, the board can be hollow as the sandwich skin gets more technical. A good example would be "aviso" boards with sandwich skins using carbon and structural pvc foam sheet core material. the skins need no additional ribs or stringers or Styrofoam.

if you choose something that is more of "boat" style construction, there is lots to learn from all the DIY moth builders.
http://www.teknologika.com
has lots of good building techniques for light and strong composite jobs


it all works, just pick the one that suits you.
have fun,
-bill

[windfreak74]

WoW Zfennell and BWD,
You guys are my building gurus!!
Thanks for participating in all my inquiries!
you guys are awesome participants of this forum for all DIY guys out there. allways helpfull and great orientation!
i wish there were more guys like this.

I have discarted monolithic building because of weight with fiberglass.
im considering soric infusion core.
its cheaper to get than foam in case on importing special foam like divinicell.
i suppose a core of 4mm will will give me a good and light composite.
the cheaper alternative is to use 3 mm wood laminate but i find it heavy.
my guestimates are in the 22 lbsto 25lbs.
polyesterene foam is harder to get here.
a have a plank from a scrap that is 2metrs x 60cms x 20cms thick from a cold storage pannels.
its a 20 kilos/cm2 density.
dont know if its the right density.
But i still am on the fence to which method i will use.
shaping or building a mold.winter is coming and ill have plenty of time to build.
any one with experience with soric core?
i will make a small model of 3mm wood laminate to understand how to make the molds and some trial laminates to give a better aproximation of weight, strength suplly for the build.
thanks,
Pedro