Foil construction concept trial balloon

[Raggi_Thor]

Then you can buy our extruded aluminium foils :-)
Sorry for the adverticement...
http://www.mboats.no/Hardware/hardware.htm

Picture of the 200mm naca 0012:

[Steve Clark]

Nifty little foils!
I am going to PM you for details.
For shapers, Look at the following link.
http://www.charlesriverrc.org/articl...oilshaping.pdf
From AeroGrandMaster Mark Drela, a nifty way to accurately shape things using normal tools and a bit of time.
SHC

[grob]

How much are the 200mm naca 0012 profiles.

Thanks

Gareth
www.fourhulls.com

[BOATMIK]

Originally Posted by Tim B

Torsional loads are incurred because of the pressure distribution on the foil. With a foam cored foil, there's not too much cause for concern. Just put at least some plies per side on at +-45 degrees.

Probably not necessary. By the time you have covered worst case scenarios for the upwind and righting from capsize for bending moment the torsion is well and truly covered. Another layer of fibres just isn't required.

The +-45 might be hugely useful for a keel carrying a bulb in some circumstances.

There are are said to be some advantages for strong winds having a centreboard with a bit of torsional flex - at least in high level sailor's vernacular.

Best wishes
Michael Storer

[nflutter]

cool raggi, i think 29ers have those.

sounds like you are all going to a lot of effort to avoid making a mould.
its easy to make very accurate moulds using a block of sloid material and a router.

use cad or a really accurate drawing to define router groves at regular intervals along the chord, at specific depths to make a basic mould, then use a screed that is the exact shape of the foil (made out of thin perspex, cut with a sharp scalpal i found worked well) and heaps of bog to finish it off. maybe have 2 goes at the screeding, one rough one, sand it and then one fine one, with a wetter bog mix. i put some metal strips in the mould too, mainly to give the screed something true to slide on, but they provided a functional purpose later, when laying up the foil.

i made the screeded mould twice as long, and cut it in half so i had a propper double sided mould that bolted together. all this was achieved in a day.

basically i laid carbon into the mould, first layer was a thin square weave, and that overlapped the metal strips. the subsequent layers of carbon, uni mostly, didnt overlap. when the halves were set, i just ran the grinder along the metal strips, (only grinding through the light layer of carbon) and ended up with a perfect straight surface where the leading and trailing edges of the 2 halves would join. the halves can be vacuum bagged, baked etc. if your going to bake make sure the moulds are made of something that wont warp with temp, and make sure you first bake the mould empty before you bake it with something in it, so the bog is cured propperly.

the core consisted of a bit of foam, shaped with the grinder pretty roughly, i just kept cutting bits off until it fitted snugly inside the closed mould. the rest of the space was filled with carbon strands in lightweight bog. basically filled the whole lot with bog, chucked the core in and bolted the mould shut, and all the excess squeezed out the front and back. (you definitely want heaps of excess bog, so theres no air bubbles in the laminate)

total time from scratch to completed carbon foil is about 15 hours tops. foil is perfectly true as if extruded or cut by a CNC router. drawback is you cant make it taper, although for my application that wasnt necessary. plus side is now you have a mould, and you can churn them out at about 2 hours a-piece.

there are also ways to make it hollow, or hollow with I-beam-like carbon webs, or with timber stringers even with trailing edge flaps etc. built into the laminate. i wont go into that detal here, if you want to know ask me.

the section below is half of a NACA 66014 if i recall, chord 120mm cut into 19mm ply.

[sigurd]

Some things seem difficult to do without CNC.
For instance, I want a curved daggerboard that has taper and variable section profiles along the span.