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av8r2488(at)yahoo.com
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 Posted: Sun Jan 23, 2011 2:53 am Post subject: Kitfox-List Digest: 8 Msgs - 01/22/11 |
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A followup on vacuum bagging and heating fiberglass for curing...There is a lot
of structural work in building a Glasair...I never vacuum bagged any
part...everything was hand layed two or three layers at a time...as long as the
room temps was close to 60- 70 degrees the glass would cure to sandable over
night so there was no need to heat anything if ambient was close to that
range....most builders (including myself) would wait for a cool day ( 45-50) to
layup big stuff like the wing spars and major assemblies so that the working
time and pot life would be long enough to make adjustments, but keep in mind the
cure time would be days for those parts under those conditions but the bond
would be just as strong..and heat the room...not the parts if you must...it
seems like there is many approaches to this subject but I definitely agree that
vacuum bagging parts is a waste of material and time for the projects we are
doing...if you were building one of rutans space planes or 50 foot windmill
props I could see a reason....but fuel tanks and speedcuffs, cowling..little
fairings....not worth the time and extra material..west epoxy is almost clear so
it works great if your going to leave parts natural..best stuff I have used so
far...I didnt start out with that system but once I found out about it I wouldnt
recommend anything else so far.......Gary ..,,,,,KF5 Outback.0-200 at
80%....Glasair 1TD flying... and Cessna 170A (My daily driver)
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EMAproducts(at)aol.com
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| Posted: Sun Jan 23, 2011 2:55 pm Post subject: Kitfox-List Digest: 8 Msgs - 01/22/11 |
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| Quote: | | Subject: Re: Re: Composites and mold work |
About 20 years I was doing some composite work and looking for a low cost vacuum pump. An old auto air conditioner compressor with a electric motor to turn it, hook to the inlet line with a gauge & relief valve and your vacuum is limited to the size of the electric motor driving it! I made lots of NASA inlets using it. has been over 30 years don't remember vacuum or anything else.
[quote][b]
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lcfitt(at)sbcglobal.net
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| Posted: Sun Jan 23, 2011 9:04 pm Post subject: Kitfox-List Digest: 8 Msgs - 01/22/11 |
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I am enjoying this discussion. It is informative and nice to see that there
are those that like trying new things and willing to share experiences.
The Lancair I spend a year and a half on was was pretty much built from
vacuum bagged skins - everything carbon fiber, except rudder. Vacuum
bagging was pretty obvious as the outer skin was slick and the inner was
covered by peel-ply. sandwiched in were foam stiffiners. We did wet
lay-ups, but it was mostly as doublers under Hysol bonded joggle joints or
fitting bulkheads. We used the squeegee between plastic mostly.
I also made gap seal cuffs in the horizontal and vertical tails of my
current Model IV project. I vacuum bagged them for the same reason the
Lancair folks did theirs - weight reduction. Also they had complex shapes
and since much of it would be on a visible surface, it was the only way to
get a really nice adaptation and surface. I figure that the cuffs plus the
electric trim tabs in both rudder and elevator added about six pounds. At
the eleven foot arm that far back, I think the vacuum bagging saved me
significant weight. I mention this because there are good reasons for
vacuum bagging on our little low tech airplanes. If you are making wing
strut fairings which will be right under the CG, probably not an issue
except for empty weight considerations, but I didn't want extra weight way
back there.
One further thought. I usually only put the bagging film on one side. I
would use a sheet of aluminum or one of the white laminated shelve boards
available from Lowes or Home Depot as the sealing tape stuck fine to that
and it didn't leak. I also found that by pulling the bagging film off with
a quick jerk, it would often separate from the tape and the tape could be
used again. for the next part. Being that I was making the gap seal cuffs
and all parts had basically the same outside dimension, the board and repeat
use of the tape saved some money.
A couple of notes regarding recent posts. My vacuum pump - for vacuum
investing for lost wax casting - was pricey even in its day. Along with the
auto air conditioner compressor, I once used a compressor out of an old
refrigerator, plumbed backward, they can suck a real vacuum. And the
refrigerator compressor has a motor attached. Also, I always mix in less
than two ounce mixes and use an electronic gram scale for proportioning.
Place the cup on the scale and zero out the cup weight and go from there. I
use a 4:1 mix so 40 grams resin equals a 50 gram mix.
Lowell
--------------------------------------------------
From: "great bear" <av8r2488(at)yahoo.com>
Sent: Sunday, January 23, 2011 2:51 AM
To: <kitfox-list(at)matronics.com>
Subject: Re: Kitfox-List Digest: 8 Msgs - 01/22/11
| Quote: |
A followup on vacuum bagging and heating fiberglass for curing...There is
a lot
of structural work in building a Glasair...I never vacuum bagged any
part...everything was hand layed two or three layers at a time...as long
as the
room temps was close to 60- 70 degrees the glass would cure to sandable
over
night so there was no need to heat anything if ambient was close to that
range....most builders (including myself) would wait for a cool day (
45-50) to
layup big stuff like the wing spars and major assemblies so that the
working
time and pot life would be long enough to make adjustments, but keep in
mind the
cure time would be days for those parts under those conditions but the
bond
would be just as strong..and heat the room...not the parts if you
must...it
seems like there is many approaches to this subject but I definitely agree
that
vacuum bagging parts is a waste of material and time for the projects we
are
doing...if you were building one of rutans space planes or 50 foot
windmill
props I could see a reason....but fuel tanks and speedcuffs,
cowling..little
fairings....not worth the time and extra material..west epoxy is almost
clear so
it works great if your going to leave parts natural..best stuff I have
used so
far...I didnt start out with that system but once I found out about it I
wouldnt
recommend anything else so far.......Gary ..,,,,,KF5 Outback.0-200 at
80%....Glasair 1TD flying... and Cessna 170A (My daily driver)
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