Laminating a foil

[Torchy]

Hi,

I'm just about to order the carbon and epoxy to laminate Loco's new main foil.

It is 1.6m*0.3m

I think I need a single full skin plus a central vertical lamination. My recollection is that this was the consensus at the sticky weekend.

It is a wooden core.

The lifting foil is ready and will be fixed in place after the vertical foil is done.

So, 3 questions:
i. What weave carbon for each component?
ii. Is the layout correct? ie single layer with vertical strengthening?
iii. If so how wide should the vertical carbon section be? My gut says up to where the fairing starts at front and rear of the foil.

Stom appears to possibly be in japan and busy, not responding to emails...does anyone else have a suitable vacuum pump and what plastic sheeting/other bits and pieces are required? (I have the peel ply)

I hope to get this done during June as I am back in the US most of July.

[Torchy]

Just found this article which gives detailed spec: http://www.uk-cherub.org/doku.php/tech/foils

[ade white]

ay up nige. or should i say howdie!
I have a vac pump and some plastic vac sheet and sealant.
Be good to arrange meet up, Draycote soon or pop over? cheers, ade. PM me.

[Torchy]

Fantastic mate...didn't know you had a vacuum pump.

Tom has phoned. It looks like the email I  'sent' didn't go and he is about.

PM/phone you soon

See yawwwwwl (I'll leave the six gun and ten gallon hat at home)

[Torchy]

From the article:

"Skins of unidirectional carbon and woven carbon cloth, will give lowest weight and maximum stiffness. Start with layers of 200 g/m² unidirectional carbon, one layer over all of the foil, plus a second layer of 200 g/m² unidirectional carbon over the top half, and a third layer of unidirectional carbon, approx.150mm wide, over top part of the foil, extending approx.100mm past the bottom of hull when the foil is right down. Then add one layer of 200 g/m² woven carbon cloth, and finally a layer of 86 g/m² glass cloth, both covering all of the foil. If you wish you can use white pigment in the top layer to enable you to produce a white foil without painting it."

Do people reckon the final layer of glass cloth is necessary/desirable?

[Torchy]

OK - getting complicated now...(the article specifies 200g carbon Uni and weave)

East Coast Glass supplies have 300g Uni and 199g plain weave

Easy Composites have 250g Uni and 130g plain weave

I suppose I go for 250g Uni and 199g plain weave....?

Or is it 300g Uni and 130g plain weave?

Or is it 250g Uni and 130g woven?

I suppose with this foil weight is not really an issue but strength and final thickness of the board are important. It would be a disaster if it wouldn't go in the slot.

Loco's slot is a wide one and when we machined the core a nominal depth for the carbon was left...Roland will probably remember what that was.

[Neil C.]

Hi Nigel,

I'm no expert on this, others may be along to correct me shortly, but....

As I understand it the unidirectional cloth is doing the great majority of the work in keeping the board stiff. The layers of woven cloth inside and out add very little extra stiffness, but help to stabilise the uni fibres and provide a degree of hoop strength. It you are going a bit heavy on the uni cloth, I would be tempted to use the lighter weave. The lightweight glass layer is purely to provide a smooth surface to make the fairing and finishing a bit easier, it has basically no structural value.

[Torchy]

Thanks Neil, that confirms my gut feelings. As long as nobody else pops up with an alternative view I'll go with that

Ciao

[Phil Alderson]

From your first post it looks like you are planning on putting a lifting foil onto it, this is going to increase the loads so I would increase the amount of Uni you use.

As Neil C mentions the woven gives you hoop strength and robustness, given the large twisting loads you could see I would certainly want to put the woven on at +- 45. An additonal strip at +-45 at the trailing edge can also help to make that more damage tolerant.

[Torchy]

Current thinking is that as it is a lifting foil then it does no harm to use 250g Uni. Thinking again about twisting forces...

Just checking I understand the offset woven layer. It would be at 45 degrees in a few strips either side of the board. I mistakenly posted this initially with 2 full layers, one under the Uni but looking back you start with the Uni. 2nd layer of offset weave is on trailing edge only.

It is very tempting to use 200g for the weave, the thinking being that the extra 50g/sq m on the Uni will not add a massive amount of bulk and we can grind width off the board if it turns out oversized, which is probably unlikely.

[Torchy]

A bit dim about all this...at what stage do you trim excess cloth/attempt to get some reasonable shape to the edges?

We faired the core but left the front and trailing edges square on the core for last 10-15mm to be formed entirely of (woven) carbon. Thinking it through the Uni should only extend to the edge of the core and for the top section, 3rd layer maybe only cover the middle 200mm ie middle 2/3rds

The weave is what will make the front and trailing edge, so I guess we just get a rough shape to the edges and rely on a lot (but hopefully not too much) of fairing of the surfaces.

[Stuberry]

Usually we wrap the cloth from the trailing edge, all the way around the front and back down the other side. So all the lose bits of cloth are at the back to make a trailing edge.

[Torchy]

Got it stu, ta

[Phil Alderson]

I have always draped the cloth over the leading edge of the foil, and just brought it together at the trailing edge in a straight line. Once cured just rough trim with a saw, and sand with a longboard to get it exact. The fibre should end up about 0.5 to 1cm beyond the end of the core to protect it.

I don't see how you could get a sharp trailing edge if you fold the fibres around it.

[Torchy]

From the way I read it I think that's what Stu was saying...it makes sense to bring the fibres together at the trailing edge.

I had wondered how easy it would be to trim and fair and from what you say I will resort to the saw,

Ta Phil