Sailplanes are white...because of gelcoat?

I always thought sailplanes were white so the interior structure
wouldn't overheat and approach the glass temperature of epoxy, about
190 F, and fail. And yet I see homebuilt aircraft of wood/epoxy
structure painted all colors. So is it the gelcoat that the white
color is protecting?

On Sun, 07 Mar 2010 09:38:31 -0800, Bret wrote:

I always thought sailplanes were white so the interior structure
wouldn't overheat and approach the glass temperature of epoxy, about 190
F, and fail. And yet I see homebuilt aircraft of wood/epoxy structure
painted all colors. So is it the gelcoat that the white color is
protecting?

BGA rules for composite gliders limit coloured areas to the wingtips and
nose explicitly to prevent the structure from getting hot enough to lose
strength and/or affect the resin. The colouring rules are explicitly
stated to be for this reason. You can paint wooden or metal gliders
however you like.

In contrast, my Libelle's manual says that no particular steps need to be
taken to protect the glider from the sun regardless or whether its in its
trailer or rigged. Its resin looks like polyester rather than epoxy.
Does anybody know for sure which it is?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

I believe the first Phonix was Polyester Resin, then the later models
were Epoxy Resin. Libelles, etc are Epoxy Resin....pretty sure.
GA


In contrast, my Libelle's manual says that no particular steps need
to be
taken to protect the glider from the sun regardless or whether its in its
trailer or rigged. Its resin looks like polyester rather than *epoxy.
Does anybody know for sure which it is?

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

On Sun, 07 Mar 2010 15:06:04 -0800, glider wrote:

I believe the first Phonix was Polyester Resin, then the later models
were Epoxy Resin. Libelles, etc are Epoxy Resin....pretty sure.

The interior of the Libelle fuselage certainly looks like epoxy, but then
there's that opaque tan coloured layer just under the gelcoat on the
wings which made me think that maybe the wings were polyester. Could it
be some sort of sandable layer between the outside (epoxy?)/glass layer
and the gelcoat?

I don't know if B series are different in this respect: mine is pre-B
series and contains many m^2 of balsa.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Mar 7, 3:31*pm, Martin Gregorie
wrote:
On Sun, 07 Mar 2010 15:06:04 -0800, glider wrote:
I believe the first Phonix was Polyester Resin, then the later models
were Epoxy Resin. Libelles, etc *are Epoxy Resin....pretty sure.

The interior of the Libelle fuselage certainly looks like epoxy, but then
there's that opaque tan coloured layer just under the gelcoat on the
wings which made me think that maybe the wings were polyester. Could it
be some sort of sandable layer between the outside (epoxy?)/glass layer
and the gelcoat?

Martin,
All Libelles use only epoxy resin. In the early days some were
concerned about their ship getting too hot sitting in the trailer,
hence the note in your flight manual. I take it you have a H-301, if
so the opaque looking areas on your wings are probably thin gelcoat
allowing the balsa-wood core to show through. keep moisture away from
her and she's a good old girl............ I have owned 2 and loved
them both, but that removable canopy became too much for an old guy to
tolerate.
Hope this helps,
JJ

On Mon, 08 Mar 2010 06:05:32 -0800, JJ Sinclair wrote:

Martin,
All Libelles use only epoxy resin. In the early days some were concerned
about their ship getting too hot sitting in the trailer, hence the note
in your flight manual. I take it you have a H-301, if so the opaque
looking areas on your wings are probably thin gelcoat allowing the
balsa-wood core to show through. keep moisture away from her and she's a
good old girl............ I have owned 2 and loved them both, but that
removable canopy became too much for an old guy to tolerate.

Thanks for clearing that up, JJ.

I have an early H.201, s/n 82, so its definitely got balsa-skinned flying
surfaces. As a somewhat ex aeromodeler I can still recognise balsa and
know what it looks like under an epoxy/glass finish having finished bits
of several models that way.

The tan layer under my Libelle's wing and tail gelcoat is definitely not
balsa - its an even, textureless mid-tan colour with a matt finish.
There's a square inch or so exposed round the tailplane's front hold-down
where the tape I put over the hold-down has lifted some of the gelcoat
off. IOW there's sufficient of it exposed to be confident of its lack of
texture. Besides its a considerably darker yellow-brown colour than I've
ever seen on a piece of balsa. I'm now really puzzled as what it might
be.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

This has been discussed on RAC in the past. There was an article in Soaring back in 1975 that discussed the subject. This link covers some of the basic points.
(http://www.soaridaho.com/Schreder/Co...olor_Temp.html)




"Bret" wrote in message ...
I always thought sailplanes were white so the interior structure
wouldn't overheat and approach the glass temperature of epoxy, about
190 F, and fail. And yet I see homebuilt aircraft of wood/epoxy
structure painted all colors. So is it the gelcoat that the white
color is protecting?

Here is an article from the

The polyester resin gelcoat is non-structural. It protects the
underlying laminate resin and PVC core from excess temperatures and
the laminate resin (Usually epoxy) from UV exposure.

Structures that are bonded with an adhesive resin have a different
failure mode, and expoxy adhesive resins usually have a higher TG than
laminate resins

Read and follow the POH and AMM of the particular aircraft in
question. Most prohibit dark markings some areas.

aerodyne

The temperature issue is not with the gel coat, polyester gel coats
are routinely used in all colors for non-aircraft applications. The
purpose of white is to keep the structural laminate temperatures in
the range where a loss of mechanical properties does not become an
issue.

Bob