Fiberglass vacuum-bagging lamination/mold technique question

14 posts / 0 new
Last post
Zelda
Zelda's picture
Offline
Last seen: 17 hours 59 min ago
Joined: 03/07/2016 - 13:15
Posts: 74
Location: Switzerland
Fiberglass vacuum-bagging lamination/mold technique question

Maybe I find here some answers about lamination/mold technique for a solid fiberglass construction.
I have already looked in RC-Forums, the have mostly knowledge in small/flat constructions with vacuum bagging,
solid shapes are mostly done with the overlay method.

I’m planning to build a housing for an 18” axial fan with fiberglass and basalt fiber cloth.
The mold from below is a bell mouth, cylinder and the cone. It has already a protective layer of epoxy for the polyester-filler.
(Polyester eats foam.)

The fiber clothes would be hand laminated and vacuum bagged.
(Basalt 390g/m2 twill > E-glass 390g/m2 twill > E-glass 390g/m2 twill > Basalt 390g/m2 twill)
I’m using the resin «Epoxy Resin L + Hardener CL” from R & G with an extended processing time of 60min, because each layer is 1m2 large.

Is it possible to laminate this round shape or should I cut the mold in half? (half circle shape)

I’m concern about the gravity from the clothes, time to process in hand laminating (total 4m2),
apply release film and at the end put this in the large vacuum bag without relocating the wet fiber clothes.
(Since I’m using not many layers, vacuum bagging is a must for strength and nicer finish.)

Any ideas how that job could be done?

hIKARInoob
hIKARInoob's picture
Offline
Last seen: 1 week 16 hours ago
Joined: 08/28/2016 - 08:15
Posts: 4191

How about dividing it in something like 10 sections using 10 strips of fibre cloth slightly overlapping each other. So top down view you divide the circle in 10 sections of ~36 degrees.

Edit:

Basically use several sections instead of one piece. You can also think of one circular section for the top, one rectangle section for the centre section etc.

Oh wait, the problem is how to get the housing out of the mold without destroying it from the inside, as the centre part is not tapered. I see…

Zelda
Zelda's picture
Offline
Last seen: 17 hours 59 min ago
Joined: 03/07/2016 - 13:15
Posts: 74
Location: Switzerland

Thanks for the answer Thumbs Up

If I understood it correctly, I lay up a couple of strips with basalt and start with vacuum bagging.
After basalt, I continue with glassfiber and at final basalt?

This would take weeks and a lot brushes, epoxy, etc. since the resin needs 24 to 48h to cure.

hIKARInoob
hIKARInoob's picture
Offline
Last seen: 1 week 16 hours ago
Joined: 08/28/2016 - 08:15
Posts: 4191

Alright, initially I see two challenges:

1) A flat or tube shaped mold is easy to laminate. This 3D shape requires attention; you don’t want thick nasty overlaps, or sections where the fibres are spread too much apart.
2) Once you’ve laminated and cured the product, how do you get it out? A shape like this means you have to destroy the mold from the inside.

My initial reply concerned the challenge of how to laminate. What I initially had in mind was something like this:

With such a strip you will have relatively little deformation of the fibre cloth.
I’m not sure why it would take weeks. You apply the resin first, then place the first strip. apply a little resin at the edge of one strip where you will have the overlap with the second strip. Then apply the second strip. Continue until whole surface is covered. Then start over again for second layer using different material; so first layer glass fibre, then second layer basalt.
I’m not sure why you have different fibres though.

kiriba-ru
kiriba-ru's picture
Offline
Last seen: 3 days 17 hours ago
Joined: 01/17/2016 - 02:34
Posts: 2129
Location: Russia

You dont need vacuum technology for this part IMO.

hIKARInoob
hIKARInoob's picture
Offline
Last seen: 1 week 16 hours ago
Joined: 08/28/2016 - 08:15
Posts: 4191
kiriba-ru wrote:
You dont need vacuum technology for this part IMO.

That makes sense too. But perhaps you get a more even and smooth surface for aesthetics purpose?

kiriba-ru
kiriba-ru's picture
Offline
Last seen: 3 days 17 hours ago
Joined: 01/17/2016 - 02:34
Posts: 2129
Location: Russia

I dont have big experience with fiber glass parts making. But I have seen many car and rc boat parts that were made with simple way (putting hand-wringed layers in the mold) and had great surface.
If weight is not main target, adding extra coating layer can give more predictable result.

hIKARInoob
hIKARInoob's picture
Offline
Last seen: 1 week 16 hours ago
Joined: 08/28/2016 - 08:15
Posts: 4191
kiriba-ru wrote:
I dont have big experience with fiber glass parts making. But I have seen many car and rc boat parts that were made with simple way (putting hand-wringed layers in the mold) and had great surface. If weight is not main target, adding extra coating layer can give more predictable result.

The surface where the fibres are in contact with the mold will be of highest quality. In your case is it possible that the surface in contact with the mold is the exterior surface of the product?
In Zelda’s case it’s the opposite; of course maybe the final result may be satisfactory nevertheless.
I also have little experience btw.

kiriba-ru
kiriba-ru's picture
Offline
Last seen: 3 days 17 hours ago
Joined: 01/17/2016 - 02:34
Posts: 2129
Location: Russia

Agree. Better to have reversed mold.

Zelda
Zelda's picture
Offline
Last seen: 17 hours 59 min ago
Joined: 03/07/2016 - 13:15
Posts: 74
Location: Switzerland

The 3 molds are not glueded together, they would be hold together with threaded rod, after curing, I can remove them to release the fiber.

Without vacuum, its hard to get air bubbles out and needs a lot of sanding (maybe damage the basalt layer) because the twill is not so easy to handle like plain cloth. (The edges tend to fringe)
It has also an aesthetics purpose but without a solutaion I must change my mind…

In general, I see the goal to split into a couple of working steps, to reduce complexity, gain time and possible handling errors.

For doing the hole thing with vacuum infusion my pump is too weak (I get only 60%, around 90% is needed) an the foam would simply “crash”.

hIKARInoob
hIKARInoob's picture
Offline
Last seen: 1 week 16 hours ago
Joined: 08/28/2016 - 08:15
Posts: 4191

It’s nice to see a fibre related project. I love metals and machining, but this is a pleasant change for me. I hope you can keep us updated with more pictures. Thumbs Up

Zelda
Zelda's picture
Offline
Last seen: 17 hours 59 min ago
Joined: 03/07/2016 - 13:15
Posts: 74
Location: Switzerland

I started with building smaller parts, this blue housing is for a RD-Tech power supply, just for a little practice:

The front and the corner are made with peel ply, the side had direct contact with film from the vacuum bag.
At this time I didn’t had perforated film, I could buy them only as a huge, expensive roll.
Later I found out that a lot of bulky things like furniture are wrapped in PE-LD perforated film, which is slightly stretchable and not sticky to epoxy. Thumbs Up

I had a leak, (vacuum bag was a painter film with 5um thickness) I got only 200mbar ~ > 2000Kg/m2 pressure.
The cloth has some areas, they are not fully wetted, maybe the pressure was too low from the leak:

I have medium to plenty of experience in machining steel, non-ferrous metal and synthetic material, but this is something completely different. I started nearly from zero.

Zelda
Zelda's picture
Offline
Last seen: 17 hours 59 min ago
Joined: 03/07/2016 - 13:15
Posts: 74
Location: Switzerland

Finally, the "practice" part (casing) is completed!

(Inside is a RD-Tech DPS5020 with a PULS Dimension QS20a 36V powersupply, which can be adjusted to 40V.)

hIKARInoob
hIKARInoob's picture
Offline
Last seen: 1 week 16 hours ago
Joined: 08/28/2016 - 08:15
Posts: 4191

Hey that looks really nice! Thumbs Up Beer