Complex Bottoms on a CompSand

Been lurkin’ on the CompSand forum fer a bit… getting up to speed, and I got curious about bottoms ( Shocked don’t worry I’m talking surfboards).

A
lot of the CompSand boards seem to have fairly conservative bottom contours
(flat/concave/vee), just wondering what is possible (with or without
contour mats). A lot of the PUPE boards I make have interesting bottom
topography… hard chine channels, step bottoms, etc… is this
possible/easy with CompSand constuction.

I know a lot depends on what skins I use, I assume that this sorta thing will be more realistic with foam skins.
Thing
is… I’ve got a, surplus to requirement, IKEA paulownia blind secreted
under my bed, that would garner enough 3x30mm stips for a 7 footer.

I wonder… ideas of lapstrake(clinker) planking and staged skinning/inserts are floating around in my head.

Regards,
Gadget.

I’m going to be doing the Ikea mini-blind skins on a midi-simmons (7’)  I’m working out right now.

I already did the Ikea blinds on a 10’7" supertanker that is performing well. I did more than half those skins lapstraked with PU glue. (sandbag failure)

For the hull to flat to deep single concave bottom I’ve got planned out. I’m thinking I’ll hand lam the whole blank and let cure till it’s just flipable. Then lapstrake on the skins.  I’ll probably end up doing the deck the same way as it has a fairly pronounced S deck on top.

I’ll post details as I go.

he G

complex bottoms means complex procedures,

or at least time consuming procedures

i guess that is why bert sell series, not customs, do you know what he charges for customs?

a lot

what is do –> glue paper sheets on top of each on top of the bottom shape

then i cut out each line

once glue hardens [or epoxy]—> sand down edge, that is reversed shaping, time consuming, one offs only. nice hobby though


if you would mill them in with a machine, then you would have either put more HD foam in certain places OR reinforce the milled out parts with a lot of resin


or, copy existing complex bottoms and vac them into your own bottom. but i think you have to pretreat your skins to get them to conform to the complex shapes, say… veneer softener or such…

Mort Subite all the way

bye

 

this is what i do. its very difficulty and complicated

make your bottom skin about 5 or 6mm thick and shape in your bottom contours

 

What if you just leave the bottom naked :smiley:

I mean: no bottom skin. I guess that when the board flexes it wil induce a concave? EPS has memory, so you won’t get the dimples like a PU/PE?? #1 EPS without bottom skin shouldn’t be a problem, or am I wrong?

 

It’s just a thought.

hey hans

hoe is het?

greg loehr thinks says knows… that if you skin only one side, all the loads go there, usually breaking that side.

mine hasnt broken yet, but also has 3 layers of 4oz on bottom.

Doei

W

build it out don’t carve it in…

four years ago CMP showed me a trick.

why carve out a complex bottom when you can build it up.

he then showed be how to build a “bonzer-style” by cutting out specific shapes out of high density dcell and then glueing them to the bottom of a perfectly flat bottom to create a complex bottom with no shaping. He then vacuum bagged on a thin bottom layer and voila you can’t tell the difference.

 

he was also the first one who discussed with me his idea to carve  and glass rail channels under the bottom wood skin, so that you could insert these batons used in wind surfer sails of varying stiffness to alter the flex pattern of a balsa compsand. He even talked of making the channels larger so you could insert inflatable tubes than could be pumped up  with various gases to increase or decrease the floatation of a balsa compsand. Again this was all back in 2004. Here’s one he gave me that got ruined because the dcell deck insert shifted during the bagging process. The core on this is a 1.9 Marko 7’6" JJ funboard blank. Check out his “daisy’d” logo his daughter made. Also notice RedX boxed  fins that don’t hurt anyone,  a standard on all CMP made boards. Again 2004 stuff from CMP…

 

[img_assist|nid=1044998|title=CMP 2004 Composite with deck build|desc=|link=none|align=left|width=640|height=480][img_assist|nid=1045000|title=CMP deck build composite bottom|desc=|link=none|align=left|width=480|height=640]

[img_assist|nid=1045001|title=New CMP Logo 2004|desc=|link=none|align=left|width=640|height=480]

Wait.  What’s the story with Ikea blinds??

I don’t know if I’m betraying the Ikea/Lowes board building guild, but… Ikea sells a mini-blind made out of laquered paulownia, the laquer job is poor and sands off easily with two strokes of a 320 grit block. If you don’t mind the little slots for the cords, you might get enough slats out of one set to skin a shortboard. I used three for the skins and rails on my 10’7". the 40" wide blinds run $19.99 each so I paid 60 bucks for 3mm paulownia skins. I think if you cut off the ends so theres no slots, the slats are about 29" long.

Here’s what mine looked like before polish.

So, what did you use for the rails on that baby?

 

Here’s my take on the channel bottom thang.

  • Shape the general bottom contour (vee/concave/etc)
  • Rout out slots for the edges of the chines
  • Insert balsa
  • Shape the channels
[IMG]http://i65.photobucket.com/albums/h208/Gadget437/Surf/CompSand/compsand_channels.jpg[/IMG]

Not sure about the skinning schedule. Whether to skin in several hits or to skin in one hit and cut the laminate where it goes over the channels, before bagging. I guess a reverse rocker table might be handy.

I did the rails lapstraked. There is no perimiter stringer per-se, It just ends up being a continuous skin all the way around the rail. Took a week to do them, so not for production. Basically starting at the rail apex, lay a course, cure, plane the edge, lay the next course, cure, plane, etc… until the rail is lapped up to the deck. Here’s a poor attempt at a cross section of the rail.

[img_assist|nid=1045038|title=Lapstraked Rail cross section|desc=|link=none|align=left|width=640|height=352]