Super 77 vs CA Glue; Veggie Bags vs Mylar

[nulluser]

Hello! A friend has recommended using 3M Super 77 to build the entire helicopter (not just wing coverings), as he claims it reduces weight. However, I believe that CA glue, if used with a capillary applicator, has the same benefits and is also easier to control and Super 77 should only be relegated to wing-covering duty. Is one better for general construction, or are they both the same? What is the difference between 6-micron veggie bags and 1.8-micron Mylar regarding performance? What should be used as trussing material?

Regards,

nulluser

[coachchuckaahs]

3M77 is a spray glue, and is not well suited to making structural joints. A very light coating is suitable for covering.

If you were to spray a bit of 3M77 onto a scrap of plastic, you could conceivably use a toothpick to place it. However, your puddle would dry quickly, and it is very gooey and sticky.

If you are looking for alternatives to CA, try Duco Cement, usually we thin it 50:50 with acetone, and apply it with a hypodermic.

For SO, and even Limited Penny Plane, I recommend staying with thin CA applied with a capillary. For SO you can even use medium CA applied with a toothpick, if the fit is not perfect.

I do not see 3M77 as a viable option for structural assembly.

Coach Chuck

[nulluser]

Thanks!

[coachchuckaahs]

Sorry, I missed your other questions.

In terms of performance, probably not much difference, though there could be substantial difference in mass. The veggie bag material may have a harder time conforming to the complex shape if an x-rotor design is used. You can still ball it up to make it in-plane springy, but it may be a struggle. But, the stuff is cheap! I have some P18 planes (7.5g planes) that have veggie bag covering.

For SO, the truss strings are usually kevlar thread. THis can be as supplied in the kits, or get some kevlar fishing line. They do not carry a lot of load, so something around 10lb should be plenty. Most kevlar fishing line has a coating, so getting glue to stick may be the primary challenge. You can find kevlar thread on Amazon or Ebay too, or get some from an indoor flying supplier. Kevlar is used because it does not stretch. In a pinch you could use sewing thread, but it may stretch a bit under load. I would strongly recommend Kevlar.

Coach Chuck

[nulluser]

Thanks once again. I got Kevlar with a 0.8mm diameter. It's coated in polyurethane, but binding thread with CA should solve that issue. Will watch weight and use capillary activator. Your resources are proving extremely helpful.