second skin

laminating skins and bagging

normaly i do both skins at once , on this board i wanted to clean up the foil a bit before the deckskin. if you look at a lot boards made this way the noses are usually pretty ugly and flat. it is because both skins are bagged at once. its more obvious on wide nose boards. also its better to leave the nose and tail pretty flat due to the fact the grain of the wood doesnt facilitate bending in that direction. its ok with pvc tho

images in reverse order

plotting a rail

the skins

using a pvc skin is easiest
you get the outline template and place it on top of the sheet of foam
draw a line with a pencil and cut the sheet out with a stanely knife or razor
if you want to use wood, its easiest to use hobby type balsa sheets that are 100mm wide and about 1000mm long
you want to use a nice thick skin for the best results
3mm thick is perfect or 1/8
id advize against using balsa wood on the deck or if you do it needs at least 6oz of glass but prefereably more
the reason why is that it break down very easily if water gets into it
other woods like paulownia are more suitable

so lets put together a balsa sheet
you needa nice big flat table to work on btw
i roll out some brown paper first (to keep resin off the table)
then i arrange my sheets and tape them together
we are taping the OUTSIDE of the skin remember
so tape and join them up. you can use this little miter box design for doing diagonals

once you have taped them together you draw the outline and trim them to shape with a razor
flip the balsa skin over and seal the untaped side with a slurry of epoxy and micro balloons.
i use around 70 grams of resin and squegee it onto the sheet.
the mix pushes into the joints and glues the sheet together and also prevents any resin bleeding through when you glass the inside.
i cut my skins 1mm over size
they should look like this

the whole operation takes 10 to 15 minutes
okay so skins are done, so you put them aside until you are ready to bag them onto the blank

you use a 2oz micro fiber for the inside glass
do the bottom skin first
put the skin on the table (covered in brown paper) and roll out your glass
trim the glass to the skin size with a razor or scissors
mix up some slow cure epoxy (you want about 1/2hr pot life,infusion resins are good)
i use 150 grams for a shortboard on a sealed balsa skin (but ive used far less,maybe 70 grams)
i perfer to mix a bit more these days and paint any leftovers on the rails and fin inserts.
wet out the cloth with squegee
flip the skin onto the bottom of your blank and place this on the rocker table
NOTE. your rocker table, blank and skins need witness marks to line up the skins with the core whilst bagging
these must be very visible in black pen

then we layup the deck skin same way and flip that onto the deck
then we tape it all down and in allignment
slide the whole lot into the bag and seal it up with mastic as shown by hunty
you need some shade cloth or material as a breather to stop the bag from sucking up the vaccum hose
however you dont need breathers all through the bag as the eps rocker table acts as a breather
turn on the pump
have your vaccum switch set to about 7 or 8 HG vaccum
you may hear a bit of hissing from small leaks
these can be sealed with more mastic
if you find small hole in the bag,mark them with a permenent marker so you can find them next time
thats it
walk away for 24 to 36 hours and your laughing
you can get away with about 6 to 8 hours in the bag

shaping the blank

so we have a raw blank at this stage i guess
before we go any further just a bit about rocker tables
rocker tables are the best and most accurate way to vac skins on to a core
they are made from EPS
they need to be a certain thickness so the dont warp or twist under vaccuum
and they need a flat bottom
you make them with same template you use to cut your blanks
its basically the bottom offcut but with a flat bottom
its good to proctect your rocker table with some 3mm mdf and it can be glues in place with contact or gorilla glue
bevel or round off any corners so they dont tear your bag
there is a picture of a rocker table below that i made with some insulation sheet
it is too thin, i intend to glue another sheet of 50 mm foam to the base

so now we have our raw blank and our rocker table waiting

now we shape the core
the nose and tail will be a bit thicker and the rail material will stick up a bit over the foil at the ends of the foil
first thing is weigh the blank onto you shaping stands and get those high density rails down to the same height as the foil
use a power planer
then foil out the thickness in the nose and tail.
have a couple of squares of 3mm thick balsa or foam sheet, to lay onto the (what you think is) the finshed tail so you can visulize the finished overall thickness.
basically you foil away the nose toalmost nothing (on a potatochip thruster) and the tail to desired thickness.
now its time to do the rail bands(plane the rail bevels)
cut the rail bands with a power planer, as in john carpers shaping 101 or such (plenty of shit on youtube)
you have a 2inch mark from the rail and a 4 inch one
although i find its more you need to adjust these when you use that little rail radius sketch i pictured above

here it is again, it shows the hight of the rail material at the outline and the hight at 15mm in from the outline.
this is how you work out the distance in from the rail for your first marks to shape to.
you can actually use your finger on the bottom of the board as a marking guage and draw a line along the side of the rail material that marks the point (the rail material height at the outline)where the first rail band is cut to.
they look good and now you cut the second rail band.
so it should like a surfboard with the two main bevels cut.
do not touch the bottom at all, leave it flat and square edge.
also the top needs to be left with a square edge (this ensure a clean joint at the skin)
so again refer to the sketch and you will see the skin wrapped down on to the bevel and flat edge
and it shows how much material will be later removed once the skins are on.
then you block and round everything off as you would shape a normal surfboard
but the rail edge must remain square.
(you shape eps with a courser grit like 40 or 60 grit and the core can be finished at about 80 grit is fine)
okay so the core is now done

cutting the foil and high density rails

for sandwhich boards 1 pound density eps is the best bet for good flex
althouh will need a vent in the board in hot climates

the templates are screw or double sided tape to the foam block
i use a solvent free spray adhesive called ados
once you stick the template on, it wont budge at all
get the wire cooking,it should cut a side in about 5 minutes
a bit of ventilation will help.
i leave the nose and tail about 20mm thick and shape the last part of the foil in, by hand after the stringers are on.
now i use 60kg PCM density airex foam for my perimeter stringers and it works great and shapes well .dvynicell or corecell will also work.
i buy a 15mm thick sheet and cut between 30mm to 40mm wide, straight strips the length of a sheet(a sheet is usually 8ft by 4 ft)
lay out your rail on some paper like here and then you can get width/height measurements before you cut your strip of pvc

its is unecessary to cut the rocker into the strips, as you can bend the foam easily
it can be warmed with a heatgun and bent over around a simple jig and clamped for a few minutes
this is less wasteful then cutting a curved strip as in berts thread
also with this little drawing you can work out your rail band cuts

i overlap both skins over the stringers
it is faster and has no adverse effects to performance
also the board is more waterproof
airex pvc is waterproof, unlike balsa which goes soggy and greatly weakens the board

the best thing about putting on the stringers first and overlapping the skins
is that you can bag on both skins in one go

once you cut the blank
you trace the outline with your half template and mark your center line.
use a gauge or ruler and mark in the thickness of your rail
you need to have and idea of your rail radius before you decide on the width and thickness of your stringer
i find 15mm thick to be perfect
so you measure in from your outline 15mm and put marks with a fine tip felt pen every 4 inches or so
then you get your outline template and use it to redraw the outline on the points
i then use a japanese pull saw to cut the outline
i find the outline needs very little work to tidy up, as the japanese saw cuts it very fast and accurately
faster then jigsaw and sanding block

so you cut the outline
true up with a sanding block if neccesary
then you glue on the tail block first
that way when you clamp on the stringers, they have a strong material at the tail to glue on to
the stringers are glued on with a fast setting epoxy and held in place with masking tape
its best to let some overlap on the bottom of the board a mm or so

after the rails are glued on you check the outline with the template and check its all good
then run over the bottom with a sanding block and true up the stringers with the bottom.
then you lay out the fins and route in the high density inserts.
high density inserts greatly increase strength and isolate the plug from the core.
just lay out your shapers marks like a finished board
and use a router template to route some holes for your inserts
i make my inserts out of the same material as the stringer but it is 20 mm thick
if you allow for skin thickness ,then your total is 23mm this allows about 3 mm at the base of your FCS tm. plugs.
other fin systems may require deaper inserts.
i find that plug systems to be superior in this construction.
i have been testing boards for 3 years and have never had a failure.
there are other alternatives to FCS tm. like RAPTOR tm., 4WFS. tm and some copies like the euro plug
i personally prefer probox for an adjustable box system. also because it is uncapped.
and the fcs fusion box for a capped box
although in my opinion capping is uneccesary
a plug system is the lightest and easiest system to repair, and if damaged it wont damage the rest of the board as capped systems like FUTURES tm. do

this whole process takes me around 40 minute to an hour at the most
and what you have is a rough blank
in production you would make a few hundred at once