I just want to second David's comment (2) on scuff sanding.
The wing mouldings are very thin and it's easy to inadvertently cut
through the structural weave if you're over zealous. Use only 200 - 400
grit "wet and Dry" abrasive and look to achieve a "flat" finish.
All the pre-moulded components were delivered with small amounts of
release agents still coating the surface. If you are in any doubt as to
how effective this is, take a look at the attached picture of a
de-laminated firewall to tunnel reinforcement. There is no sign of the
firewall having been prepared - it is still "shiny" and the resulting
lamination has not bonded. I was able to slide a steel rule under one
edge and "unzip" it.
This aircraft was built by students studying for a degree in aerospace
engineering at a renowned university ..... which doesn't say much for
the quality of instruction or inspection.
I can't really name the university, but if Sir Geoffrey was alive today,
he'd be turning in his grave!
Nigel
On 24/01/2016 15:30, davidjoyce@doctors.org.uk wrote:
>
> Will, as far as the factory gel coat goes two very important principles:
>
> 1. Make sure you wash all the gel coated bits very, very thoroughly.
> The release agent used in the moulds has a great ability to induce
> potentially serious allergic reactions, if you just sand it off. (That
> speaking with my medical hat on!)
>
> 2. You need to fine sand the gel coat until you cannot see even a hint
> of any shiny patch, even with a magnifying glass. Any shiny bits
> however small will give imperfect adhesion of your covering coat.
>
> Regards, David, GXSDJ
>
> On 2016-01-24 13:43, William Daniell wrote:
>
>> Ummm....you got me there.
>>
>> I am talking about the white finish of parts that come from the factory.
>>
>> Will
>>
>> By that way david...nice pun
>>
>> On Jan 24, 2016 6:50 AM, "Jan de Jong" <jan_de_jong@casema.nl
>> <mailto:jan_de_jong@casema.nl>> wrote:
>>
>> There may be confusion re what we call gel coat?
>>
>> On 1/24/2016 12:12 PM, davidjoyce@doctors.org.uk
>> <mailto:davidjoyce@doctors.org.uk> wrote:
>>>
>>> Will, on the principle that extra weight is a definite downer
>>> and always think light or lighter, I would remove as much as you
>>> can without damaging the fibreglass, subject to getting your
>>> perfect profile. If the gel coat was properly applied in the
>>> first place it should be pretty much in chemical continuity with
>>> the FG resin.
>>>
>>> Regards, David Joyce, GXSDJ, with gel coat finish I would not
>>> change if you paid me!
>>>
>>> On 2016-01-23 22:12, William Daniell wrote:
>>>
>>> Is it ok to fill on top of gel coat orovided that its
>>> scuffed up. In other words is it necessary to go down to
>>> the fiberglass?
>>>
>>> I am dealing with the wing skin join and the fuselage join
>>>
>>> Thanks
>>>
>>> Will
>>>
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