Re: Carbon fiber cloth for Treger's vp prop hub?

From: Tapio Linkosalo <tapio.linkosalo_at_iki.fi>
Date: Fri, 07 Jan 2011 08:43:01 +0200

On 7.1.2011 1:19, leop12345 wrote:
> A recent INAV shows a plan for Ivan Treger's F1D vp prop hub. The
> composite screw holder is made from carbon fiber cloth and foam. The
> foam is easily found but the carbon cloth (looks to be plain weave in
> the drawing) is specified to be 0.05mm thick. This works out to 0.002"
> or about 1 oz per square yard in weight.
>
> I cannot find cloth this light and even 2 oz cloth, at 0.004", is rare
> (and expensive). Does anyone know if Treger's plan's specification is
> incorrect? If not, does anyone know where Treger obtain the carbon fiber
> cloth he used.

When laminating spars for outdoor FF models I have found that 100g/m2
russian unidirectional carbon produces a laminate of 0.1 to 0.12mm per
layer, so that 0.05 thick laminate would translate to about 50 grams per
square meter. I think the thinnest fabrics available (in Europe I'd
suggest German R&G company, but I'd suppose there are firms also in the
US...) is about 60g/m2; however, this is somewhat "sparse", suitable for
D-box "taco shells", but I thing for a tiny part only about 1mm wide it
would not work that good. Therefore I think that "carbon paper", which
does not have rowings but is of separate fibers glued together might
work in such laminate.

> Treger's screw holder is neat because once one makes the composite
> structure piece, individual screw holders can be quickly cut off,
> drilled, and tapped. This makes for a neat way to produce many such
> screw holders.

Also the use of rohacell as core material is a good idea. For my own VP
hubs constructed of pultruded carbon tubes I have laminated the screw
holder out of carbon tow: made a simple male plug of balsa, wirh packing
take on top and then a little wax. Drilled a 1mm piano wire across to
the place where the screws are, then wetted carbon tow with epoxy and
wrapped it around one end of the piano wire, over the "back" of the mold
around the other wire and back. When dry, used dremel to deliberately
remove most of the carbon laminate. This works but is a bit too
flexible, so that for F1M I had to add a cross piece to stiffen it.
Tregers' way of making a carbon-rohacell-carbon -laminate is a better
way to make a stiff and light part.



-Tapio-
Received on Thu Jan 06 2011 - 22:43:13 CET