Gelcoat sag?

Dave,

I stand mine up on end, tip down. I find this works a little better than
trailing edge down, though I think most don't have the facilities. Main
thing is that you don't let the gelcoat set in any particular position over
the winter as the low temperatures will tend to make the waves permanent.
Best of all would be a warm room (above 60F) where you have the sapce to
turn them - almost like a giant, low heat rotisserie.

Missed you at R4N. Hope you can make it in 08.



wrote in message
...
On Dec 15, 12:42 pm, wrote:
Hey guys. I've got a question regarding wing "waviness". I've got an
LS1f with very good gelcoat condition. However, if I look down the
wing long-ways, just above the leading edge I can see what looks like
a series of 4"-6" diameter lumps (for lack of a better term). They're
somewhat regularly spaced along the full length of both wings and are
parallel to the leading edge. They are very, very subtle, and you
can't really see them without looking from the correct angle to use
the glossy reflection. They're very similar on both wings and are in
the 4"-8" range up from the leading edge. I've done some "tap tests"
to see if I could detect delamination, but the wing surface is
consistently solid all over. I'm thinking this might be gelcoat "sag"
and/or just improper sanding during the last refinish. Do refinishers
have rigs to "rotate" the wings (on the spar) as they're spraying? It
almost seems like after spraying the top of the wings, they were
rotated to a position where this point of the wing was the lowest
allowing sag there. Anyone have any thoughts or comments as to what
this might be? Besides these defects, the rest of the wing surfaces
are consistently smooth and uniform.

The description of the wing refinish in the log indicates the
following:

- acrylic enamel (from previous refinish) and factory gel coat removed
via sanding
- primed with Simtec primer
- sanded with 100 grit
- primed again with Simtec primer
- sanded with 120 grit
- series of coats of Simtec white to thickness of 6-8 mils
- sanded with 180 grit
- series of coats of Simtec white to thickness of 8 mils
- wet sanded with 1000 grit
- wet sanded with 1200 grit
- wet sanded with 1500 grit
- power buffer with 3M finesse #1
- power buffer with 3M finesse #2

There's nothing in the log that refers to profiling or shaping. Only
"sanding" and "polishing". If any attempts were done to shape and/or
profile, do you think that would have been logged along with the rest
of the description? There's two and a half pages devoted to this
refinish job, so it's not like he left much out.

The ship flies beautifully, and sure seems to have good legs relative
to it's published performance numbers. I don't think these surface
defects are pronounced enough to be having any large effect on
performance, but I haven't tried any serious attempts at performance
testing either. At this time I guess I'm more interested in knowing
what they are. Although there will probably come a time when I'd like
to remedy it for the performance improvements if there are any to be
had.

Thanks,
Dave

Experienced racers have long known about the dreaded sag.
We store our wings trailing edge down over the winter and they
revert back to correct shape for the next season.
See ya, Dave

PS: RAS = Rabid Aviation Speculation ;-)

On Dec 16, 9:01 am, "user" wrote:
Dave,

I stand mine up on end, tip down. I find this works a little better than
trailing edge down, though I think most don't have the facilities. Main
thing is that you don't let the gelcoat set in any particular position over
the winter as the low temperatures will tend to make the waves permanent.
Best of all would be a warm room (above 60F) where you have the sapce to
turn them - almost like a giant, low heat rotisserie.

Missed you at R4N. Hope you can make it in 08.

wrote in message

...



On Dec 15, 12:42 pm, wrote:
Hey guys. I've got a question regarding wing "waviness". I've got an
LS1f with very good gelcoat condition. However, if I look down the
wing long-ways, just above the leading edge I can see what looks like
a series of 4"-6" diameter lumps (for lack of a better term). They're
somewhat regularly spaced along the full length of both wings and are
parallel to the leading edge. They are very, very subtle, and you
can't really see them without looking from the correct angle to use
the glossy reflection. They're very similar on both wings and are in
the 4"-8" range up from the leading edge. I've done some "tap tests"
to see if I could detect delamination, but the wing surface is
consistently solid all over. I'm thinking this might be gelcoat "sag"
and/or just improper sanding during the last refinish. Do refinishers
have rigs to "rotate" the wings (on the spar) as they're spraying? It
almost seems like after spraying the top of the wings, they were
rotated to a position where this point of the wing was the lowest
allowing sag there. Anyone have any thoughts or comments as to what
this might be? Besides these defects, the rest of the wing surfaces
are consistently smooth and uniform.

The description of the wing refinish in the log indicates the
following:

- acrylic enamel (from previous refinish) and factory gel coat removed
via sanding
- primed with Simtec primer
- sanded with 100 grit
- primed again with Simtec primer
- sanded with 120 grit
- series of coats of Simtec white to thickness of 6-8 mils
- sanded with 180 grit
- series of coats of Simtec white to thickness of 8 mils
- wet sanded with 1000 grit
- wet sanded with 1200 grit
- wet sanded with 1500 grit
- power buffer with 3M finesse #1
- power buffer with 3M finesse #2

There's nothing in the log that refers to profiling or shaping. Only
"sanding" and "polishing". If any attempts were done to shape and/or
profile, do you think that would have been logged along with the rest
of the description? There's two and a half pages devoted to this
refinish job, so it's not like he left much out.

The ship flies beautifully, and sure seems to have good legs relative
to it's published performance numbers. I don't think these surface
defects are pronounced enough to be having any large effect on
performance, but I haven't tried any serious attempts at performance
testing either. At this time I guess I'm more interested in knowing
what they are. Although there will probably come a time when I'd like
to remedy it for the performance improvements if there are any to be
had.

Thanks,
Dave

Experienced racers have long known about the dreaded sag.
We store our wings trailing edge down over the winter and they
revert back to correct shape for the next season.
See ya, Dave

PS: RAS = Rabid Aviation Speculation ;-)- Hide quoted text -

- Show quoted text -

That's just mean! LOL!