Rocker With Heat and Moisture

[gbgreen59]

Has anyone tried adding rocker by using heat and moisture? I'm sure the experienced guys know all about this. But, I'll ask anyway.

Boat builders, using wood for a medium, used to apply steam to the planks as they formed the planks to the shape of the boat. The added moisture to one side of the board causes the plank to bend.

Luthiers use a similar technique. They soak the wood for the sides of the instrument in water. Then they run a heated tube across one side of the wood. As one side of the plank starts losing moisture due to the heat, it can make very tight bends (the sides of a guitar are only about 1/8" thick).

I could see using this technique to add rocker to a board, but I've not seen anything on it in this group. I could have easily missed finding a discussion on it, though.

[gbgreen59]

One thing to note about the method Luthiers use is that they do not build jigs for shaping the bends. They draw the shape on paper, then they make the bends feehand. They control the radius of the bends by applying heat in specific areas.

As applied to a kiteboard, rocker could be made with sharper bends at the tails and mild rocker in the middle without making a jig (a rocker table). It seems that there would be more control over the rocker by using this method.

[zfennell]

not too many wood boards built that way.

addiction kiteboards in australia
uses that process for pawlonia cored boards

the kids on zero-prestige have promoted it for plywood boards.
........
but now i think they just surf them flat and let them bake in the sun
with a few bricks stacked on top.


-bill

[bay surfer]

Being a luthier/boat builder/board builder/ I can say its easier to do two laminations of thin wood on a jig, than to bend using heat, when making a fiddle you wet the wood first then bend on a hot round iron, and you use a solid thin piece of wood, not ply. boat buiding you always use a jig or the ribs for bend. A single lamination will increase the strength, and if you use screws with your jig the process is really easy, you just fill holes with epoxy and wood dust.

[gbgreen59]

Thanks for the response Bay.

It didn't make sense to me to try to bend plywood like this, since plywood is meant to be stable by putting the grain of the plys in different direcitons.

I'm new to reading this group, so I'm not familiar with your technique. Sounds like you lay up your own plys on the rocker table. Is this true? I know you have posted a lot of information in this group, so I'll do a search on you screen name to find out about your technique.

Thanks again for responding.

Gary

[Larpy]

gary there are two schools here
woodies and lay ups

woodies are easier and quite strong while the lay-ups tend to be very light and fairly strong and a bit more involved. I'm assumming your building a wood board which is fine but some what limited as far as design is concerned.

Honestly though you can ride anything so wood with a light rocker is fine.

[gbgreen59]

I'm just fishing and gathering information at this point.

I ran across a thread that was discussing types of foam core. Can anyone help me understand the following layup information:

H80-EGLASS-EPS-EGLASS-H80

I'm guessing that these are horizontal layers. Is EGLASS- epoxy glass layer. I know the H80 is Divinicell foam. With all these layers, seems this board would be quite thick unless the H80 is very thin...like say 1/4". How thick would you say this board is? Is EPS another type of foam?

Thanks again for the help.

Gary

[zfennell]

-the H80 sandwich skins will be .1 -.125" thick
-Eglass is E - type (normal/electrical ?) as opposed to better grade
S or S-2 .
-epoxy for compatibiliy wih EPS
-EPS= expanded polystyrene
-still need 1 layer of glass on full exterior

-total thickness should be between 1/2 - 3/4" (closer to 1/2)
or it will be probably be very stiff

The use of EPS as a core, along with H80 sandwich
should work fine.

however, a single 1/2" sheet of H80 will also work as well.

-bill

[crabman]

If your building wood boards ,then a rocker table is the best way to go .Thats what we use. The danger is that some of our wood boards are coming close to the weight of some carbon boards.If you put moisture in the board its a pig to get out unless you bake the wood after .http://www.racingfinish.co.uk

[joe90]

The way I go, is to cut X-section profiles, and attach mdf on rigid frame.
Seal the MDF and cover in PTFE/glass sheet from AeroVac....





This way you get rocker and concave.

More details on http://CustomKiteBoard.com under 2004 Diary