|
>Gel coat is a pain.<
It certainly is when on the outside
of thin fibreglass parts. My cowl already has cracks, although it hasn´t
even been mounted yet. The gelcoat is .01 - .02 thick and is very
similar to an egg shell. It contains no fibers what so ever and the ability
to stretch is nil.
The upside is that, at least in theory,
the surface is closed and there are no pinholes. The celcoat simply has
to be sanded to a mat finish and can be painted without a lot of filling
and further sanding necessary. Sounds easy, doesn´t it?
The downside is, that the statement
above only applies to rigid structures, which our cowls are certainly not.
The only way to permanently repair
cracked gelcoat on our cowls is to remove the gelcoat completely from all
"problem areas", ie. the frontal area, around fasteners (alternatively
over and around the hinges) and along edges that are prone to vibrate.
The best substitute for the removed
gelcoat is 1 BID and some sanding and minimal filling. Remember that the
gelcoat cracked because of vibration and flexing, so if you fill the area
with micro alone, little strength will be added and cracks will reoccur
after a while. Micro is also a fiberless material with little or no ability
to stretch and will crack if applied in thick layers on vibrating
surfaces.
A general reinforcement of the cowls
is probably no bad idea. Two 1 1/4" strips of 1/4" foam, edges cut
to 45 deg. and top edge slightly rounded, strategically placed across the
cowl (both top and bottom cowl) and one similar foam strip along the centerline
of the top cowl sounds like a good (and light weight) approach. Cover with
2 BID and consider it done.
These days "double pigmented" gelcoat
is available. This allows for a very thin layer of gelcoat and thus
allows a lot of flexing before the gelcoat cracks. I have seen quite a
few of these parts for ultralights and still haven´t seen any cracks.
The downside is a considerable print through from the weave, requiring
a lot of wet sanding and polishing (real exciting on ultra thin gelcoat!)
if to be considered as final surface.
Finally, to those of you who still
don´t get it:
1.) From tomorrow morning, use the
metric system!
2.) Tell your neighbours to do the
same and have them tell their
neighbours..........
Cheers
Tim Jorgensen, Denmark
Fiberglass boat builder
LNC2, 1% done, expecting to fly later
this century.
|