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Step 2 INSTALLATION OF THE BOTTOM SKIN |
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I have officially discovered
vacuum bagging! It's awesome! I did the landing brake inside
layup with the unit I purchased as a practice/test part (click
here to visit that page) and it turned out OK, but not as good as my
elevators have so far. Click here
to go to my vacuum bagging page. This picture is of the first elevator
I did, in the vacuum bag supplied with the kit. This layup, 2 layers
of UNI (at a 30 degree angle to the elevator) was covered with 2 layers of
peel ply, then two layers of paper towel and then bagged. This picture
shows how well the nylon bag works to conform to the shape of the part you
are bagging - you can even see the texture of the foam through the surface
of the bag. |
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You can see this system, the
same pump as the landing brake layup but now using the supplied bag is able
to pull a serious vacuum without leaks. I set the release valve at
about 15" of Hg, and, once the pump pulled this vacuum and things settled
down, this level of vacuum was held all night without the pump running.
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Here I am doing the second
elevator. I took a few more in progress shots for this one. The
layup is done as you would normally, here I am putting on the micro over the
foam. When the layup is complete, make sure you trim it very close to
all the edges - I used my Dritz electric scissors. |
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Once the layup is complete (and
trimmed), two layers of peel ply and paper towel are laid over the over the
layup and the part is inserted into the bag. This bagging system uses
a bag that is open at both ends, it's a 9 foot roll of bagging material.
I used one of the supplied clips on one end of the elevator and left the
other end open. |
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Once the elevator is inserted
into the bag, you install the vacuum fitting through a small hole you cut
into the bag. I make sure I have enough paper towels reaching from the
part/peel ply to the vacuum fitting so the air can be pulled out properly.
The paper towels function as breather ply in this setup. You then add
the clip on the other end of the bag and start the pump. |
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Once the pump pulls the vacuum
to the desired setting, the bagging material does its trick. It's
flexible enough to conform to some pretty sharp corners without wrinkling.
I did try pretty hard to get the peel ply on smoothly to help solve any
wrinkling problems. |
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The finished elevator.
Very, very nice when finished. A very smooth layup, no bubbles,
complete conformance to the shape of the part (you can see how good of a job
the bag did in attaching the glass layers around the front of the torque
tube) and maximum glass to resin ration for strength. Since these
parts are weight sensitive, it was very satisfying to do them this way and
know they were as light as they could be. |
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Here's a close up of one end of
one elevator after vacuum bagging. You can see I didn't get the layup
trimmed exactly to the edge of the core and the vacuum bag helped be out my
forcing the two layers of UNI (which is generally hard to get to bend around
corners) squarely over the edge. Sure, this will get sanded off but it
is a great demonstration of how good the bagging system works. |
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Here's the second elevator
curing in its bagged state. I think I might weight down the elevators
when I do the top skins to be sure there is no warp induced by how tight the
bag gets. |
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The second elevator after
bagging. You can see that the top and bottom layers of the bag have
forced the extra layup material in between the two of them but still forced
the layers around the curve of the tube. This is not a problem, all of
this gets sanded off before you put on the top skin layers. |
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A better shot of the effect
mentioned in the text above. |
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Once both bottom skins were
cured, I cleaned up the leading and trailing edges and ends with a sanding
block per plans. I also used my sanding spline to make sure the
trailing edge was straight. I didn't have to knife or saw trim the
trailing edge because I scissor trimmed it close to the foam core when I did
the vacuum bag steps. |
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Checking the trailing edge
"length" with the canard airfoil template. Once sanded close to size
and then spline sanded to make a straight edge, my elevators were ready for
their top skins. |
| Click here for Top
Skins |
