Thread Tools
This thread is privately moderated by eagle60, who may elect to delete unwanted replies.
Jul 19, 2017, 09:09 AM
Registered User
eagle60's Avatar
Thread OP

Covering wings with fiberglass under vacuum

Material needed :
- polythene flexible sheet (the one used to cover the salad in the vegetable garden will do)
- 60 gr/m2 glass cloth
- 120 gr/m2 glass cloth
- packing paper light
- a small piece of nylon cloth
- epoxy resin
- pure alcohol (the one used for liquors 95%)
- off course the wings with the shells
- an old fridge or freezer compressor (must be working) to be used as vacuum pump
- plastic to make a sealed bag and tape to seal it

Cut a piece of polythene big enough to envelope the wing (top and bottom) and make an invitation bent on the line of the leading edge (photo 1).
Cut a piece of packing paper like the polythene size.
Cut a piece of 60 gr glass cloth like the polythene size.
Cut 2 triangular pieces of 120gr glass cloth with base half the wing central cord and high 3/4 of the wing span (photo 2)
Cut 3 squares 1"x1" of nylon cloth

Now take the polythene sheet, place on it the paper and the 60gr cloth on the paper (no wax or detatching agent is needed as the epoxy will not stick on the polythene).
Mix the resin and the catalyst and dilute with the alcohol (40% about). For each wing in the photos I did use 12 gr resin, 5 gr catalyst and 6/7 gr alcohol. In my opinion it is better to dilute the resin beause it will be more fluid and you will need less resin to soak the glass cloth; remember that all the weight you place in this operation will increase the wing weight, whilst the alcohol will go away.
Now soak the whole surface using as less resin as possible.
Place the 2 triangular 120 gr glass cloth pieces in the center of each wing faces (top n bottom) and soak them.
Place the 3 nylon squares near the trailing edge of the top face of the wing and soak them: as problably the fiberglass will be too stiff to be used as aileron hinge it will be necessary to cut it and the pieces of nylon cloth will be the aileron hinges(photo 3 - sorry it is out of focus but it gives the idea).
If there is resin leftover you can slightly wet the wing (bottom first).
Place the wing on the cloth, close the sandwich and place it in the shells (I suggest to hinge the 2 shells on the front with paper tape to easy up the job).
Push the wing core as frontward as possible with the help of pins or sticks (photo 4).

Place on trailing edge and on center and tip some wrapped up paper (you can fix it with pins but be careful not to puncture the polythene sheet inside nor to leave a tip outside the shell as it will puncture the outer bag preventing vacuum to be effective). This in needed to help all the inside air and vapours to find a way out. Put it in a plastic bag and seal it leaving just a small hole. (photo 5)
The weight you see in photo is needed only to keep the sandwich flat on the table to avoid bents and warps.
Insert a hose in the hole and seal it with tape; connect it to the intake of the compressor and start it. While the bag is going under vacuum check that the bag is not going to block the hose or any other possible airflow and that there are no leaking points (you can ear the air hiss if there are some). (photo 6 and 7).

Let the resin cure for the necessary time ( I let it cure for 24 h to be sure) than you can take the wing out. The row result is on photos 8 n 9 while on photo 10 you see the wings cleaned. Each wing is 16 cm cord in the center, 10 in the tip and has 42 cm span and weights 45 gr as you see in photo.
The paper on the wings is needed to prevent the quantity of micro-holes that the fibergass usually carries and also helps to have a smooth surface avoiding the need of further treatment: you can paint directly with any type of paint with no risk to see the inner foam melting down.
Remember that before joining the 2 wings you will need to fix the aileron servo position, cut the servo slots and dig the channel for the servo wire.

I hope this could be helpful for somebody.
For bigger wing you will probably need to increase the glass cloth weight.
Last edited by eagle60; Jul 19, 2017 at 09:17 AM.
Sign up now
to remove ads between posts

Quick Reply
Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Covering a Convex / Under-cambered wing. Taxus812 Painting and Finishing Tips 4 Mar 05, 2016 01:33 PM
Question Covering a wing with Fiberglass dk31 Foamies (Scratchbuilt) 2 Jun 02, 2014 09:57 PM
Build Log Parflyer built completely with Honeycomb under vacuum pirulin Composites Fabrication 5 Feb 12, 2013 02:04 PM
Discussion Covering under-camber wings Malc The Builders Workshop 1 Jul 06, 2006 02:33 PM
Help! How to Cover Under Cambered Wing? dhable Electric Plane Talk 8 Apr 15, 2006 03:57 PM