Hi Tony
I think, for what it is worth, that to flox the ribs first and let them
set is only a good idea if you can guarantee that you will get them
perfectly flush with the cores. As this is not possible, I would advise
that you don't. If you have low spots, then you will end up with bubbles
under the surface. If you end up with high spots, then in attempt to
sand them down, you will inevitably sand the foam surrounding the ribs
down before you even make an impression on the flox.
However, the flox when wet, is quite flexible and can be moved around
under the skin.
We did it by first applying masking tape parallel with the ribs right
next to the 45 degree cut-outs in the core, then applied the flox,
levelling it to be a flush as possible with the cores, laying clear
plastic over it, and using a squeegee to remove the excess flox. The
masking tape stops the flox from getting on to the flying surface
profile of the cores whilst you manipulate the flox with the squeegee.
Then whilst it was still wet, removed the masking tape and do the skin
lay-ups.
Practice putting the bi-axial cloth on before putting any slurry, resin
or flox on the wing surface. We rolled the cloth onto a cardboard roll.
We marked the leading edge with a pen line once we had alligned it, so
that doing it for real, we would know that it was positioned correctly.
This is because pulling the skin back up, pulls out the flox that you so
carefully positioned in the rib joints.
It all appears to be frightening, but once you start, it is ok. Floxing
vertically is ok if the consistancy is correct. Too dry and it rapidly
becomes unworkable as it picks up dust. Too wet and it drops out and
runs down the wing
I wouldn't do the leading edge lay-ups on my own either. You need one
person continuously mixing resin, and at least two applying the slurry.
Apply the resin quickly and generously before laying the Bi-axial cloth,
as you can squeegee the excess out to the surface, but trying to get the
resin back through on the dry spots is a nightmare. Once the skin is on,
a resin roller is an excellent way to draw the epoxy to the surface.
We peel plied the whole of the leading edge back to the spar. We were
told that it would also help to draw the excess through the fibre glass
and make a lighter wing. I am personally, not so sure that this is
correct. It could just leave a thicker layer under the peel ply, you
have to make your own mind up on that one.
Good luck
Eddie
Tony Renshaw wrote:
>
> Gidday,
> Advise on leading edge floxing sought from classic builders.
> I have a classic with the leading edge cores all setup for the big day.
> Only a few tidyup jobs to do and "on with the show". HOWEVER, I was
> wondering if I could get the collective wisdom of those that have gone
> before me.
> My question is this: "I want to flox the ribs in advance so that I have a
> perfectly flat surface to skin over. I have sought advice from Andy who
> recommends against this method but says that it should not degrade the
> required strength in this area considerably. The triangular sections either
> side of the ribs are 1/4" or 6 mm wide, so the total width should be approx
> 1/2" or 12 mm. My width is 15 mm and about 6-8 mm in depth. This increase
> in area combined with the fact that my wing skins will be perfectly flat
> over the ribs should equate to a strength neutral position and leave me
> with less to do in one go during the big layup. I intend on peel plying the
> flox and carefully sanding it prior to skin layup.
> So this is what I want to do, and I am keen to hear whether people think it
> is a dumb idea or a good one. In conclusion I figure if the wing flexes so
> much that the upper surface skin wants to depart the flox surrounding the
> rib below, that the wing is under tremendous stress already, and that a
> compromised or slumped wing skin that had the flox placed at the same time
> will not cope as well as my setup which will maximise the inherant strength
> of the skins. I know people will tell me that it isn't that bad to do all
> at once. The fact is that I don't really feel confident I can get the
> required standard I want with floxing in the vertical plane which is
> something I have never done before. I know my way I can get uncompromised
> skins.
> Help?????Pleeeeeeese.
> Reg Tony Renshaw
> Reg
> Tony Renshaw
> Builder No.236
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///////South East London Flying Group/////////
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