Re: Q1 Fuselage comes up
Eugen,toggle quoted messageShow quoted text
Everyone is right about the sharp corners and the cloth wrapping them.
Guidelines on how much rounding of the corners is needed can be found here:
Also, the best way to round the corners in a very smooth way is to use a
spare piece of the foam as a sanding block. The foam will grind away on both
the block and the piece you are sanding and make a very nice curve (lots of
foam dust, so have a vacuum cleaner on hand).
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Rob de Bie
Sent: Tuesday, March 30, 2021 6:06 AM
Subject: Re: [Q-List] Q1 Fuselage comes up
Very nice work indeed!! But I agree with Keith: the sharp corners are far
from optimal. Your light vacuum will make sure that the glass fiber cloth
will conform, so that's not the problem. But if you have a multiple ply
laminate laid over a small radius, you will get high out-of-plane stresses
if a bending moment is applied. Now whether there is a lot of bending moment
in the fuselage skins, I don't know, they are probably secondary effects.
But I would nevertheless increase the radius quite a bit.
As an example of out-of-plane stresses: imagine laminating a 90 angle with
10 cm / 4 inch legs, with
3 or 4 layers. If you would bend it so the angle gets smaller, the
out-of-plane stresses will push the laminate plies against each other - no
problem. But if you bend it so the angle gets bigger, the sign changes, and
the out-of-plane stresses want to delaminate. Now do this same experiment
with different radii, and you will see that the larger the radius, the
stronger the specimen will be.
On 30 Mar 2021 13:43, Keith Welsh wrote:
Hi Eugen,cloth likes rounded edges.
It doesn't like making sharp turns. The only places I remember havingsharp turns is where glass
tapes were used for bulkheads and micro was used in the corners.:-))