Fiberglass Release Agent for Vacuum Bagging

[John Foster]

I'm about to start a project of making new wing cradles for my trailer (a home-made trailer). I plan to vacuum-bag them using the wing as a mould. However, I still haven't finalized what I'm going to use as a release agent on the wing. It is an old glider that has damage history, and has been painted. The pain is chipping and peeling up in places, and I hesitate to use packing tape in case it would lift the paint off the wings. I've also considered using a thin piece of construction plastic taped over the wing, but question whether this will cause problems with the vacuum, as the vacuum will be applied over top of it. Any other ideas, or feedback on these thoughts?

[Morgan Hall]

I would use vacuum bagging release film. No worries about whether you waxed it enough or had any places where the resin might bond. Additionally you might want to put your felt padding or whatever on the wing and then cover with release film. Then your layups and bag it. Most likely you're going to want the cradle oversized enough to accept some type of cushion or pad. You may have to experiment with multiple layers depending on how much it compresses from the vacuum force.

Morgan

[Martin Gregorie]

On Wed, 15 Feb 2023 19:40:05 -0800 (PST), John Foster wrote:

> I'm about to start a project of making new wing cradles for my trailer
> (a home-made trailer). I plan to vacuum-bag them using the wing as a

> mould.....

> Any other ideas, or feedback on these thoughts?
>

I've not tried this on glider wings, but I used to fly entirely self-built
F1A free flight models with carbon wing D-boxes which I vacuum formed over
hot-wired blue foam male moulds.

My first thought is to tape whatever felt you'll line the wing cradles
with round the wing, and cover that with plastic film that's a suitable
thickness to wrap closely round the felt and give a smooth outer surface.
Then vacuum-form the cradles over that, using glass cloth as the inner and
outer layers and glass matt layers between them to give the cradles
whatever thickness and strength you require.

You could either vac-form the cradle's inner layer using one or two
glasscloth layers and then add more glass mat layers and a final
glasscloth layer or two without a using vacuum bag. This would probably be
easier than trying to assemble all the layers on the wing and then add a
vacuum bag over the lot.

Note that by 'vacuum bag' I mean using a plastic sheet with a vacuum
connection thats a suitable size to fit over the wetted glasscloth that
will form the cradle and be taped to the wing all round with something
like wide masking tape to provide a vacuum seal.


--

Martin | martin at
Gregorie | gregorie dot org

[Hank Nixon]

On Wednesday, February 15, 2023 at 10:40:08 PM UTC-5, John Foster wrote:
> I'm about to start a project of making new wing cradles for my trailer (a home-made trailer). I plan to vacuum-bag them using the wing as a mould. However, I still haven't finalized what I'm going to use as a release agent on the wing. It is an old glider that has damage history, and has been painted. The pain is chipping and peeling up in places, and I hesitate to use packing tape in case it would lift the paint off the wings. I've also considered using a thin piece of construction plastic taped over the wing, but question whether this will cause problems with the vacuum, as the vacuum will be applied over top of it. Any other ideas, or feedback on these thoughts?

For what you are doing there is no need for vacuum bagging.
Wrap the entire surface, with extra margin, with corrogated cardboard , with pleats spanwise . This adds allowance for felt. Then tightly wrap in plastic and lay glass directly on that. Masking tape can be used for all taping. It will be accurate enough for a wing saddle.
Good luck
UH

[emirs...@gmail.com]

Stretch film Is the cheapest. Mylar film Is the pro.

[jtr...@cox.net]

I have used a method similar to what Hank suggests except I use the felt as the spacer instead of cardboard. Polyethylene sheet works well for a release film. Lay up what you want over the plastic film, cover that with more film and squeegee the the result. Most excess resin can be removed this way. Not the same as bagging but works well. I have used this method to make wing cradles, wing wheel cuffs and tail dolly cuffs.
TR

[Steve Leonard]

On Thursday, February 16, 2023 at 2:27:57 PM UTC-6, jtr...@cox.net wrote:
> I have used a method similar to what Hank suggests except I use the felt as the spacer instead of cardboard. Polyethylene sheet works well for a release film. Lay up what you want over the plastic film, cover that with more film and squeegee the the result. Most excess resin can be removed this way. Not the same as bagging but works well. I have used this method to make wing cradles, wing wheel cuffs and tail dolly cuffs.
> TR

Curious as to why you go to the extra effort to "remove excess resin" from a non flying part? Unless it is just force of habit from working on flying parts, and you don't want to lose your touch. Peel ply, at the most, on the outer surface as a first step for paint prep.

Just my two cents,
Steve Leonard

[John Sinclair]

I’d start by securing the wing with leading edge up and then mask off the area beyond your wing saddle, ie mask off everything except your saddle. Otherwise, the squeegee’d excess resin will end up all over your wing around the saddle. Your saddle needs to be wider than the wing to allow room for the cushion material ( about 1/4” if using carpeting). Lay up saddle until it’s about 1/8” thick, which will take something like 6 to 8 layers of 8 oz. cloth. Boat resin is fine for this application and it cures much faster, too! Add your wooden base plate set in thickened resin (cotton flow) and several layers of cloth to secure it. Trim your new saddle back to desired shape and paint it red, if desired.
Hope this helps,
JJ

[Charlie M. (UH, Pi & 002 owner/pilot)]

Removing excess resin also helps to push out air bubbles/pockets, thus a stronger part when done.
We do peel ply on flying bits, but also squeegee that as well for the same reasons.
Yes, it's a tiny bit lighter as well.

[Mark Mocho]

Excess epoxy in globs can also crack under stress. Its best strength is when it provides a minimum volume matrix with the glass fibers. Squeegee out as much excess as possible and cover with a peel-ply polyester fabric which will soak up some even more of the excess and then pull the peel ply off when everything is cured.

[Dan Marotta]

When I made a wing wheel cuff for my LS-6 back in the early 90s, I
didn't even bother with peel ply. I wrapped a strip of carpet (the
padding) around the wing, then plastic film, then wet layup glass and
epoxy. When it was cured, I spray painted it with a rattle can.

It wasn't beautiful but it worked great.

Dan
5J

[Papa3]

On Wednesday, February 15, 2023 at 10:40:08 PM UTC-5, John Foster wrote:

> I'm about to start a project of making new wing cradles for my trailer (a home-made trailer). I plan to vacuum-bag them using the wing as a mould. However, I still haven't finalized what I'm going to use as a release agent on the wing. It is an old glider that has damage history, and has been painted. The pain is chipping and peeling up in places, and I hesitate to use packing tape in case it would lift the paint off the wings. I've also considered using a thin piece of construction plastic taped over the wing, but question whether this will cause problems with the vacuum, as the vacuum will be applied over top of it. Any other ideas, or feedback on these thoughts?

Not what you asked for, but... A club member has designed a very simple but effective and sturdy wing saddle using aluminum sheet. It's much less bulky than fiberglass, easier to make, and lighter. The secret is the closure mechanism, which is elegantly simple. If you're interested I can try to get some pictures when I'm in the shop on Sunday.

P3

[Mark Mocho]

. A club member has designed a very simple but effective and sturdy wing saddle using aluminum sheet. It's much less bulky than fiberglass, easier to make, and lighter.

I built neatly 350 wing wheels from 2001 to 2019, when I stopped production due to other commitments. (As well as getting bored with them and not being able to charge enough to warrant the 15 hours of hand fabrication in each one.) All were made with a steel chassis and an aluminum cradle (cuff). Each could be shaped exactly to the wing profile from a cardboard template without having to have a mold or the actual wing to use for a fiberglass layup. Aluminum is a viable choice for a wing wheel, but it has to be of sufficient strength to avoid deformation and possible damage to the wing if it flexes excessively. I am considering resuming production on a limited basis, but only if I can charge enough to afford the "better beer" as opposed to the cheap swill I used to consume.

[jfitch]

I'd be very interested in seeing photos of the closure mechanism. This is the Achilles heel of all wing saddles.

[Dan Marotta]

Mine was closed with nuts and bolts at the trailing edge, but the LS-6
did not have winglets and the cuff was simply slipped on at the tip

Dan
5J

[weemacgregor]

Greetings P3:

I was wondering if you were able to get pictures of the aluminum sheet wing saddle that one of your club members had designed? I would be very interested in seeing this.

Thanks,

rob p.

[Papa3]

Sorry - forgot to do this when I was in the shop last week. Will try this weekend.

[Papa3]

> > Greetings P3:
> >
> > I was wondering if you were able to get pictures of the aluminum sheet wing saddle that one of your club members had designed? I would be very interested in seeing this.
> >
> > Thanks,
> >
> > rob p.
> Sorry - forgot to do this when I was in the shop last week. Will try this weekend.

Here are pics one of the club members took. https://share.icloud.com/photos/0e4Dsb8L_hzDX4woT4PJxvHCw

Things to note:

- Saddle is bent aluminum made from a single sheet.
- Closure uses PVC pipe with a slot cut in it to capture two robust pieces of aluminum bar stock.
- Foam is a medium density material that works very nicely.
- Mounting plates for the truss are riveted into the bent sheet.
- The truss could probably be made a little more robust (this one had a shock absorber/damper but it suffered from neglect and abuse in a club setting)

P3

[weemacgregor]

Great design, pictures, and explanation.

Thank you for your trouble P3.

rob p.