Glue

GLUE

We are using T-88 epoxy because of it's tolerance to loose fitting joints and reports of service worthiness over many years...

From experience with other epoxies in a Rutan Vari-eze project and instructions on the product labels we follow these shop practices:

We never glue in temperatures below 70 degrees F. (Drying takes forever if you break this rule and maybe the joint isn't so good too)

We glue in a well ventilated area and use vinyl throw away gloves.

T-88 uses white vinegar for clean up and that's what we use.

T-88 is a 1 to 1 mix and still there are mixing challenges because many sessions require a small amount of glue. We find that glue hangs on the side of the mixing pot so a small amount appears to be a smaller quantity than when it finally levels out.

Put a Sharpie pen mark on the side of the see thru mixing pot for each of the 2 part fill levels.

Observe the amount of each part carefully in the mixing pot - take your time!

Mix the material thoroughly - the color of the final blend should not show streaks of color. Mix by turning the material around and around with a stick in both clockwise and counterclockwise directions. Scrape the sides and bottom of the pot at least twice and scrape the mixing stick on both sides at least twice...

We use acid brushes and throw them away after one use.

We pop the hardened glue out of the mixing cups and reuse the cups several times. The mixing sticks are used several times too.

Handy wrap under glue joints keeps the bench and other parts clean. Be careful with wax paper - it leaves contamination on any surface that subsequently needs to be glued!

Click on the picture to the right for an inventory of the items needed for the gluing process.

It is January 20, 2001 and we in the final gluing stages of the second wing half... Along the way we have observed:

1) It really is best to glue in 70 degree F. or above temperatures... We are skeptical about glue penetrating the joining pieces properly in lower temperatures...

2) Examine the pieces to be joined for clean uncontaminated un-saw burned surfaces... We encountered some plywood that seems to be very smooth on one side - almost like there is a finish on it... We glued up some test samples and tore them apart - the break came at the glue line! A proper glue joint will pull wood out of the mated pieces as the glue is supposed to be (stronger) than the wood!

3) When ever possible put glue on both pieces to be joined... If you are putting the glue on one part only double coat it and then be sure the joining pieces are brought close together so there is some ooze out - however don't squeeze out a T88 joint by applying too much pressure... Light contact is the objective... On critical joints like the spar caps joining the spar web be sure to coat the spar web and the cap - both pieces...

4) We liked the vinyl gloves much better than the latex gloves which are necessary for the MEK based coating systems...

5) You get a real wave of satisfaction when that wing half is hanging finished in the rafters with the aileron moving smoothly in the hinges...

6) Then the next big decision - do you trust (train) helpers in the standing stage Vs 8 hours solitary with a sanding pad... (Yes) and teach them to put one light coat of varnish on too!...